Local Anesthetics Flashcards
(120 cards)
1
Q
A 23-year-old woman is scheduled to undergo augmentation mammaplasty with intravenous administration of a sedative and local injection of 1% lidocaine with 1:100,000 epinephrine. Weight is 110 lb(50 kg). Which of the following is the maximum dose of lidocaine with epinephrine that can be administered to this patient? A) 20 mL B) 25 mL C) 30 mL D) 35 mL E) 40 mL
A
D) 35 mL
The maximum dose of lidocaine with 1:100,000 epinephrine recommended for nontumescent injection is 7 mg/kg. In the 110-lb (50-kg) patient described, the maximum dose is 350 mg. Onepercent lidocaine with 1:100,000 epinephrine contains 10 mg per 1 mL; therefore, the maximum dosage for injection is 35 mL
2
Q
The maximum dose of lidocaine with 1:100,000 epinephrine recommended for nontumescent injection is:
A
The maximum dose of lidocaine with 1:100,000 epinephrine recommended for nontumescent injection is 7 mg/kg.
3
Q
Quick way to calculate amount of 1% lidocaine w/ 1:100,000 epinephrine
A
[ weight in kg / 10 ] * 7 = mL
4
Q
An otherwise healthy 45-year-old woman undergoes excisional biopsy of a skin lesion on the chest under local anesthesia with 30 mL of 1% lidocaine with 1:100,000 epinephrine. Weight is 176 lb (80 kg). The patient says she has light-headedness, headache, and palpitations 5 minutes into the case after administration of anesthesia. Cyanosis and tachycardia are noted. Oxygen saturation is 90%, and supplemental oxygen is administered. Methemoglobinemia is suspected. Administration of which of the following antidotes is the most appropriate next step? A) Dantrolene B) Glucagon C) Insulin D) Methylene blue E) Propranolol
A
D) Methylene blue
5
Q
Methylene blue is used to treat:
A
Methemoglobinemia
6
Q
Treatment for methemoglobinemia / dose of tx
A
Methylene blue: Most patients require only one dose. Resolution of toxicity should be seen within 1 hour, often within 20 minutes. The most appropriate dosage for adults is 1 to 2 mg/kg (0.1 to 0.2 mL/kg) intravenously over 3 to 5 minutes; the dose is repeated in 1 hour if continued symptomatology or significant methemoglobinemia is noted. The total dose should not exceed 7 mg/kg
Although there are reports of successful usage in neonates and infants, administration of methylene blue is not recommended for pediatric patients younger than age 6 years. For patients older than age 6 years, dosage is individualized; most cases reported in medical literature have utilized starting doses of 1 mg/kg either intravenously, intramuscularly, or intraosseously over a period of 5 minutes
7
Q
Methemoglobinemia
A
Methemoglobinemia prevents hemoglobin from carrying oxygen. Red blood cells contain four hemoglobin chains. Each hemoglobin molecule is composed of four polypeptide chains associated with four heme groups. The heme group contains an iron molecule in the reduced or ferrous form (Fe2+). By sharing an electron in this form, iron can combine with oxygen to form oxyhemoglobin. Hemoglobin can accept and transport oxygen only when the iron atom is in its ferrous form. When hemoglobin loses an electron and becomes oxidized, it is converted to the ferric state (Fe3+), or methemoglobin. Methemoglobin lacks the electron that is needed to form a bond with oxygen and, thus, is incapable of oxygen transport.
8
Q
Color of blood containing methemoglobin
A
Blood containing methemoglobin is a dark, reddish brown color.
9
Q
At what levels does methemoglobin change the color of blood / relevance
A
This dark hue imparts clinical cyanosis when methemoglobin levels are at 1.5 g/dL (approximately 10 to 15% methemoglobin concentration); however, a level of 5 g/dL of deoxygenated blood is required for similar effects. Therefore, when methemoglobin levels are relatively low, cyanosis may be observed without cardiopulmonary symptoms.
10
Q
Levels of methemoglobinemia vs symptoms
A
0-3%: Normal methemoglobin concentrations
3-15%: Slight discoloration (i.e., pale, gray, or blue) of the skin may be present.
15-20%: The patient may be relatively asymptomatic, but cyanosis is likely to be present. 25-50%: Headache, dyspnea, light-headedness, weakness, confusion, palpitations, and chest pain.
50-70%: Cardiac arrhythmias, delirium, seizures, profound acidosis, coma, and death can occur
11
Q
Local anesthetics associated with methemoglobinemia
A
Local anesthetics can act as oxidizing agents for the ferrous form of iron.
Most cases of local anesthetic-related methemoglobinemia have been associated with topical benzocaine (1 in 7000 bronchoscopies in one study). However, there are cases of lidocaine associated with this potentially fatal reaction in the literature, and knowledge of this is vitally important given the frequency with which plastic surgeons use this dru
12
Q
Local anesthetics and iron
A
Local anesthetics can act as oxidizing agents for the ferrous form of iron.
Relevance: can cause methemoglobinemia
13
Q
Glucagone is an antidote for:
A
Antidote for beta blocker overdose
14
Q
Antidote for beta blocker overdose
A
Glucagon
15
Q
A 40-year-old woman is scheduled to undergo exploration and repair of an isolated tendon laceration. An infusion of 1% lidocaine with 1:100,000 epinephrine is administered from the mid palm to the middle phalangeal area. No tourniquet or additional anesthesia is planned. Which of the following conditions is the surgeon most likely to encounter during surgery? A) Critical digital ischemia B) Enhanced tendon mobility C) Excessive patient anxiety D) Optimal surgical field E) Poor hemostasis
A
D) Optimal surgical field
16
Q
The few cases of digital necrosis w/ epinephrine reported in the literature employed agents such :
A
The few cases of digital necrosis reported in the literature employed agents such as cocaine and procaine with undisclosed volumes of injection or concentrations of epinephrine
17
Q
Backup if concerned about blanching/ischemia in the hand after using epinephrine
A
In patients who demonstrate excessive intraoperative blanching or concerning symptoms of ischemia, phentolamine can safely reverse the vasoconstrictive effects of epinephrine. In one study of over 3000 patients, not a single case required phentolamine reversal
18
Q
Avoiding a tourniquet in hand surgery
A
Large case series of common hand procedures, such as carpal tunnel surgery and tendon repair, support the safety of a local anesthesia-only, tourniquet-free approach. Tourniquets and upper extremity blocks, while generally very safe, are not without morbidity or complication.
Study authors recommend direct volar digital injections of 2 mL of local anesthesia. Up to 30 mL may be used in the wrist and hand and more in the forearm, if needed. The tumescent effect provides a fully anesthetic, bloodless field for optimal visualization
19
Q
A 62-year-old woman is undergoing excision of a ganglion on the dorsal wrist with lidocaine Bier block. During the procedure, she says she feels pain, becomes restless progressively, develops a metallic taste in the mouth, and has ringing in the ears. Which of the following is the most appropriate management
A) Administer diphenhydramine intravenously and continue with the procedure
B) Decrease the tourniquet pressure by 50 mmHg to ease the tourniquet pain
C) Deflate the tourniquet completely, wait a few minutes to reperfuse the arm, then exsanguinate and reinflate the tourniquet
D) Inject bupivacaine (Marcaine) locally to help with the pain and continue with the procedure
E) Maintain an airway and administer oxygen
A
E) Maintain an airway and administer oxygen
The clinical scenario describes tourniquet cuff leak leading to lidocaine toxicity
20
Q
Factors that predispose to cuff leak during Bier block anesthesia
A
Factors that predispose to cuff leak during Bier block anesthesia include obesity (funnel-shaped arms) and hypertension
21
Q
Signs of lidocaine toxicity
A
Initial signs of lidocaine toxicity include anxiety, tinnitus, and perioral numbness; muscular twitching, seizures, and respiratory or circulatory arrest may develop later.
22
Q
Management of lidocaine toxicity
A
Critical initial management includes maintenance of the airway, oxygen ventilation, and intravenous fluid administration
23
Q
A 64-year-old woman is evaluated because of pulmonary distress that begins in the postanesthesia care unit after undergoing a 3-hour elective abdominoplasty and progressively worsens during the next 6 hours. History includes long-standing hypertension that is well controlled with metoprolol. She smokes one pack of cigarettes per week, but she discontinued smoking 2 weeks before the surgery. Preoperative vital signs were within normal limits.
Intraoperative studies show: Crystalloid - 4 L EBL 250 m UOP 125 mL SaO2 >90% on 10L nonrebreather face mask
Heart rate is 80 bpm, respirations are 24/min, and blood pressure is 162/95 mmHg. Evaluation shows no abdominal discomfort, chest pain, or changes in mental status. A portable chest x-ray study shows pulmonary venous congestion. ECG shows sinus rhythm, signs of left ventricular hypertrophy, and normal S-T segments. Which of the following is the most likely cause of the pulmonary failure?
A ) Acute coronary syndrome
B ) Congestive heart failure
C ) Exacerbation of chronic obstructive pulmonary disease
D ) Pneumonia
E ) Pulmonary embolism
A
B ) Congestive heart failure
The patient described has developed early postoperative pulmonary failure most likely caused by congestive heart failure. Perioperative fluids were administered with the assumption that the patient had normal cardiac function. Her history of long-standing hypertension, combined with postoperative studies that included the ECG showing left ventricular hypertrophy and chest x-ray study consistent with pulmonary edema, support diastolic dysfunction.
Acute coronary syndrome is causedby an atherosclerotic plaque rupture blocking a coronary artery. The acute event is usually associated with chest pain and elevation of S-T segments on ECG. Pulmonary embolism is always a concern, but that usually occurs later in the postoperative period.Onset of symptoms is sudden and characterized by chest pain, respiratory distress, and anxiety. Pneumonia and chronic obstructive pulmonary disease exacerbation are not supported by the clinical history
24
Q
Leading admission diagnosis for medicine and cardiology hospital services and why
A
Congestive heart failure is currently the leading admission diagnosis for medicine and cardiology hospital services. The main reason is the overlooked high prevalence of diastolic dysfunction secondary to long-standing systemic hypertension. Patients with hypertension and cardiac diastolic dysfunction have preserved left ventricular contractile function, but they also have hypertrophied ventricular muscle that is unable to maintain normal diastolic compliance. This can lead to higher left ventricular filling pressures, elevated atrial pressures, atrial distension, atrial arrhythmias, elevated postcapillary pulmonary pressures, ventilation/perfusion mismatches, and pulmonary and peripheral edema. Treatment involves afterload and preload reduction
25
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A 24-year-old man who sustained burns over 60% of the total body surface area in a chemical fire requires skin grafting for release of ectropion after 8 weeks in the intensive care unit. When administering anesthesia, which of the following drugs is most likely to have adverse effects in this patient?
A ) Atropine
B ) Diazepam
C ) Enflurane
D ) Pentobarbital
E ) Succinylcholine
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E ) Succinylcholine
Succinylcholine-induced hyperkalemia is most frequently observed in patients with large burns who have also had long hospitalizations. Without treatment, potentially fatal cardiac arrhythmias can occur. This condition is also observed in patients who have endured long hospitalizations for neurologic disorders, limiting mobility. Upregulation of acetylcholine receptors is thought to be responsible for the increased efflux of potassium from muscle cells when depolarizing neuromuscular blocking drugs such as succinylcholine are administered to such patients.
26
Predisposition for succinylcholine-induced hyperkalemia
Patients with large burns and long hospitalizations
| Patients who have endured long hospitalizations for neurologic disorders, limiting mobility.
27
What is thought to be responsible for the increased efflux of potassium resulting from administration of depolarizing neuromuscular blocking drugs such as succinylcholine?
Upregulation of acetylcholine receptors is thought to be responsible for the increased efflux of potassium from muscle cells when depolarizing neuromuscular blocking drugs such as succinylcholine are administered to patients with predispositions.
28
Treatment of succinylcholine-induced hyperkalemia
Treatment includes supportive measures and administration of calcium, glucose, insulin, albuterol, furosemide, and/or sodium polystyrene sulfonate (Kayexalate), depending on the patient's symptoms
29
An otherwise healthy 38-year-old man comes to the emergency department after inadvertently hitting the tip of the index finger of the nondominant left hand with a hammer. He has smoked one pack of cigarettes daily for 20 years. Physical examination shows a subungual hematoma from a nail bed laceration, as well as edema and ecchymosis of the finger tip. There are no exposed vital structures. To repair the injury, a digital block is performed with 1% lidocaine in 1:200,000 epinephrine. Two hours after administration of the local anaesthetic, the finger remains pale and cool. Which of the following is the most appropriate next step in management?
A ) Administration of low-dose aspirin
B ) Application of a warm compress to the affected digit
C ) Elevation of the hand
D ) Injection of phentolamine
E ) Topical application of papaverine to the digit
D ) Injection of phentolamine
30
What is phentolamine
alpha-blocker that can be used to reverse epinephrine ischemia
31
Which of the following anesthesia techniques is contraindicated in a 44-year-old man scheduled to undergo open carpal tunnel release?
A ) General anesthesia
B ) Local anesthesia with lidocaine and epinephrine
C ) Local anesthesia with lidocaine only
D ) Regional anesthesia with a Bier block
E ) Regional anesthesia with a nerve block at the cubital tunnel
E ) Regional anesthesia with a nerve block at the cubital tunnel
A nerve block at the cubital tunnel, through which the ulnar nerve passes, will provide appropriate anesthesia for the ulnar nerve, but not for the median nerve, which passes anterior to the cubital tunnel at the elbow and through the carpal tunnel at the wrist. This would not provide sufficient anesthesia to perform carpal tunnel release.
32
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A 59-year-old woman is scheduled to undergo blepharoplasty. She has a history of postoperative nausea and vomiting. Administration of which of the following anesthetic agents is most appropriate for this patient?
A ) Inhalational nitrous oxide
B ) Inhalational sevoflurane
C ) Intravenous etomidate
D ) Intravenous ketamine
E ) Intravenous propofol
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E ) Intravenous propofol
Propofol is widely used in ambulatory surgery because of its favorable clinical characteristics, including rapid recovery and minimal PONV. When compared with propofol, sevoflurane is associated with a higher incidence of PONV. Etomidate has minimal cardiovascular side effects, but it has a high incidence of PONV and is not commonly used in outpatient anesthesia. Nitrous oxide has been found to increase PONV when used as a primary anesthetic agent but not when used in combination with other agents. Intravenous anesthesia with ketamine has a lower risk of pulmonary aspiration but may result in higher rates of PONV.
33
Most predictive factors of postoperative nausea and vomiting
Postoperative nausea and vomiting (PONV):
A recent study concluded that female gender, a history of motion sickness or PONV, nonsmoking status, and use of postoperative opioids were most predictive. The incidences of PONV with the presence of zero, one, two, three, or all four of these risk factors were 10%, 21%, 39%, 61%, and 79%, respectively.
Some surgical procedures are associated with a higher incidenceof PONV, eg, major breast procedures, strabismus surgery, laparoscopy, and laparotomy.
Agents used during anesthesia, including opioids, nitrous oxide (N2O), and volatile inhalational anesthetics, are emetogenic. Pain, anxiety, and dehydration may also increase the incidence of PONV
34
Pros of propofol for ambulatory surgery
Propofol is widely used in ambulatory surgery because of its favorable clinical characteristics, including rapid recovery and minimal postop nausea and vomiting.
35
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A 25-year-old man with profound hyperhidrosis is undergoing botulinum toxin type A (BOTOX Cosmetic) injection. EMLA (prilocaine-lidocaine) cream is applied to the injection site. Which of the following best represents the minimum amount of time necessary to achieve anesthesia?
A ) 5 Minutes
B ) 15 Minutes
C ) 30 Minutes
D ) 60 Minutes
E ) 90 Minutes
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D ) 60 Minutes
36
EMLA (eutectic mixture of local anesthetic)
EMLA (eutectic mixture of local anesthetic) is a highly effective method of inducing topical anesthesia. A eutectic mixture consists of two substances that when mixed have a lower melting point than either substance alone. EMLA uses a combination of lidocaine and prilocaine. It has excellent penetration and produces remarkably little sensitivity reactio
37
Time required for anesthesia with EMLA (eutectic mixture of local anesthetic)
60 minutes
38
Application of EMLA (eutectic mixture of local anesthetic)
The cream is applied fairly thickly (1-2 g of EMLA per 10 cm2of skin) and a dressing such as Opsite or Tegaderm is used to keep it in place. Gentle regular massage to the area can be applied for at least an hour
39
A 25-year-old woman is undergoing bilateral augmentation mammaplasty. During the procedure, the patient becomes tachycardic, with a sudden rise in end-tidal carbon dioxide, a decrease in oxygen saturation, and elevated temperature. Which of the followingis the most appropriate sequence of management?
A ) Administer a beta blocker, volume resuscitate, and finish surgery
B ) Administer therapeutic dose of heparin intravenously and start a heparin drip; rush patient to angiography suite
C ) Open the incision, remove both prostheses, and administer high-dose antibiotics
D ) Place bilateral chest tubes and order a chest radiograph
E ) Stop inhalational agents, hyperventilate with 100% oxygen, and administer dantrolene
E ) Stop inhalational agents, hyperventilate with 100% oxygen, and administer dantrolene
40
Malignant hyperthermia
Malignant hyperthermia is an inherited myopathy characterized by a hypermetabolic state when the patient is exposed to an appropriate triggering agent, such as all inhalational agents or depolarizing muscle relaxants (ie, succinylcholine).
41
Clinical presentation of malignant hyperthermia
Initial presentation is usually an unexplained tachycardia, followed by an increase in end-tidal carbon dioxide, decrease in oxygen saturation, dysrhythmia, and muscle rigidity. Hyperthermia occurs but can be a late finding.
42
Treatment/response for malignant hyperthermia
The most appropriate management involves calling for assistance, stopping all triggering agents, hyperventilating with 100% oxygen, administering dantrolene, stopping all surgery, volume resuscitating, and correcting hyperkalemia
43
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A 44-year-old man is scheduled to undergo extensive body contouring surgery following massive weight loss. Which of the following best represents the most appropriate minimum ambient operating room temperature?
A ) 60°F (15.6°C)
B ) 65°F (18.3°C)
C ) 70°F (21.1°C)
D ) 75°F (23.9°C)
E ) 80°F (26.7°C)
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C ) 70°F (21.1°C)
Long operative times and significant surface area exposure are often required in body contouring procedures following massive weight loss. These factors may contribute to decreases in core body temperature. Actively maintaining intraoperative normothermia allows patients to maintain normal coagulation function during elective plastic surgery lasting longer than two hours, potentially reducingthe occurrence of bleeding-related complications.It has been recommended that ambient room temperatures for these cases be kept no less than 70°F (21.1°C)
44
Recommended ambient temperature for long case with significant surface area exposure
70°F (21.1°C)
45
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The American Association for Accreditation of Ambulatory Surgery Facilities (AAAASF) standards mandate that all facilities must have which of the following drugs readily available for the treatment of malignant hyperthermia?
A ) Dalteparin
B ) Dantrolene
C ) Darifenacin
D ) Dicyclomine
E ) Dobutamine
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B ) Dantrolene
46
Earliest signs of malignant hyperthermia
The earliest signs are tachycardia and an increase in the end-expired carbon dioxide concentration.
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Mortality with / without dantrolene for malignant hyperthermia
With the use of dantrolene, the mortality from malignant hyperthermia decreased from 80% in 1960 to less than 10%.
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What is dantrolene
Dantrolene is a skeletal muscle relaxant that depresses the intrinsic mechanisms of excitation-contraction coupling.
49
Pediatric dosing of dantrolene
Pediatric dosing is the same as for adults
Therapy is started by continuous rapid intravenous push beginning at a dose of 1 mg/kg to 2.5 mg/kg and continuing until symptoms subside or the maximum cumulative dose of 10 mg/kg is reached
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Care during infusion of dantrolene
Care must be taken during infusion to avoid extravasation because there is a possibility for tissue necrosis because of the high pH
51
Screening test for malignant hyperthermia
The only screening is through muscle biopsy
52
Approach to anesthesia for patients known to be prone to malignant hyperthermia
Dantrolene should be administered preoperatively to patients prone to malignant hyperthermia; anesthetic drugs that are known to trigger malignant hyperthermia should be avoided.
Medications considered safe for patients susceptible to malignant hyperthermia include both lidocaine and bupivacaine. General anesthesia can be performed with alternative anesthetic regimens including nondepolarizing paralytic agents, nitrous oxide, and opioids (eg, vecuronium, propofol [Diprivan], and fentanyl
53
A 57-year-old man has chest pain in the recovery room after undergoing uneventful septorhinoplasty for repair of a deviated septum and collapsed internal nasal valve. Electrocardiography shows changes consistent with acute myocardial ischemia. He has no history of cardiac disease and takes no medications. Weight is 154 lb (70 kg). Intraoperative anesthesia included 1% lidocaine 20 ml with 1:100,000 epinephrine infiltrated into the nasal tissues, followed by intranasal placement of pledgets soaked in 4 ml of 10% cocaine solution. Infraorbital nerve blocks were performed bilaterally using a total of 10 ml of 0.5% bupivacaine. Which of the following is the most likely mechanism of the myocardial ischemia?
(A)Decreased systolic and diastolic left ventricular function
(B)Histamine-induced coronary spasm
(C)Impaired depolarization of the cardiac action potential
(D)Increased peripheral vascular resistance
(E)Vasoconstriction of epicardial coronary arteries
(E)Vasoconstriction of epicardial coronary arteries
The most likely cause of change in electrocardiography in the patient described is vasoconstriction of the epicardial coronary arteries caused by a toxic dose of cocaine. The maximum safe dose of cocaine is 1.5 mg/kg, or 100 mg in a 70-kg adult. The patient described received a topical dose of 400 mg. With an average 37% mucosal absorption rate, the absorbed dose is still approximately 150 mg.
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Maximum safe dose of cocaine
The maximum safe dose of cocaine is 1.5 mg/kg, or 100 mg in a 70-kg adult.
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Muscosal absorption of cocaine
37%
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Cardiac effects of cocaine
Cocaine increases myocardial oxygen demands via alpha-adrenergic stimulation and decreases myocardial oxygen supply through vasoconstriction of the coronary arteries, resulting in myocardial ischemia.
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Adverse cardiac reactions from local anesthetics
Adverse cardiovascular reactions are possible after the administration of local anesthetics. At toxic levels, lidocaine and bupivacaine block sodium channels in cardiac tissue, resulting in a depressed rate of depolarization during phase 0 of the cardiac action potential. This manifests as prolonged QRS width, depression of left ventricular function, and ventricular arrhythmias from increased activity in reentrant pathways.
58
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A 32-year-old mancomes to the emergency department because he has a 2-cm laceration of the forehead. He developed urticaria after receiving a local anesthetic during suturing of a laceration of the leg two years ago. Which of the following local anesthetics is most likelyto cause hypersensitivity in this patient?
(A)Bupivacaine
(B)Etidocaine
(C)Lidocaine
(D)Mepivacaine
(E)Procaine
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(E)Procaine
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Local anesthetics that cause most allergic reactions
Local anesthetics with a para-aminobenzoic acid (PABA) ester-type structure seem to cause most anesthesia-related allergic reactions
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Why does 'the other' class of local aesthetics not cause as many hypersensitivity reactions?
Local anesthetics with a para-aminobenzoic acid (PABA) ester-type structure seem to cause most anesthesia-related allergic reactions. Documented cross-sensitivity has been exhibited within the ester-based family of local anesthetics and structurally related compounds (eg, paraben preservatives). PABAis structurally similar to methylparaben. Amide local anesthetics do not metabolize to PABA; therefore, hypersensitivity to amide local anesthetics is rare.
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Solution to hypersensitivity reactions with ester-based anesthetics
Because of possible hypersensitivity, many manufacturers have reformulated some of their products to eliminate methylparaben. Some of these products include Nesacaine-MPF (methylparaben-free), Xylocaine MPF, Polocaine MPF, and Sensorcaine MPF.
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A 50-year-old woman comes to the office for rhytidectomy. Height is 5 ft 1 in and weight is 110 lb (50 kg). Diazepam 10 mg and oxycodone 5 mg is administered with a sip of water approximately 30 minutes before the procedure is scheduled to begin. Forty-five minutes after 50 ml of 0.5% bupivacaine and 10 ml of 0.5% lidocaine with 1:100,000 epinephrine is injected into the patient’s face, she becomes confused and disoriented. The ECG monitor shows heart block and wide-complex arrhythmia. Which of the following is the most likely cause of the ECG reading?
(A)Benzodiazepine toxicity
(B)Bupivacaine toxicity
(C)Lidocaine toxicity
(D)Opioid toxicity
(E)Primary undiscovered coronary artery disease
(B)Bupivacaine toxicity
In the scenario described, a medication error has apparently occurred. A staff member has probably misread the surgeon’s formula for local anesthetic and used bupivacaine in place of lidocaine.
The accepted maximum dose of bupivacaine is 2.5 mg/kg, and thus anything over 150 mg is considered toxic in a 50-kg patient. The patient described was given 50 ml of a 0.5% solution, which contains 5 mg/ml of medication. Therefore, she was given 250 mg of the medication, well into the toxic range. On the other hand, had she been given lidocaine 0.5% with epinephrine, the maximum dosage would have been 7 mg/kg, or 350 mg of lidocaine. The amount of lidocaine in 50 ml of a 0.5% solution is 250 mg, within the safe zone for this patient. If the solution had been mixed as intended, the patient described would have received 250 mg of lidocaine and 25 mg of bupivacaine, and the resulting total amount would have been within the safe zone and well below the toxic range.
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Accepted maximum dose of bupivacaine
2.5 mg/kg
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Cardiac effects of large doses of bupivacain
Large doses of bupivacaine can cause irreversible, nonrecoverable heart block (a recent case in Australia involved placing the patient on cardiac bypass until the toxicity was resolved [Soltesz, et al. 2003]). Recent literature has indicated that intralipid (1 ml/kg of a 20% solution IV recommended by Weinberg) is important in reducing mortality (Weinberg, et al. 1998, 2003, 2006; Rosenblatt, et al. 2006). Discussion at recent anesthesiology meetings has resulted in the recommendation that all facilities using bupivacaine also be stocked with intralipid (Dr. P. Schneider, anesthesiologist, personal communication
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A 55-year-old woman is scheduled to undergo concurrent suction lipectomy of the neck and lower abdomen and rhytidectomy. Weight is 110 lb (50 kg). Conscious sedation with a local anesthetic and tumescent solution is planned. The neck and face should be injected and this portion of the surgery performed prior to the injection and liposuction of the abdomen for which of the following reasons?
(A)The absorption rate of local anesthetic above the clavicles is two times faster than below the clavicles
(B)The epinephrine must be injected immediately before suctioning or it will not be effective
(C)The facial area requires more anesthesia so the sedation can be lightened during the abdominal portion of the case
(D)The lower abdominal liposuction should be performed first to allow time for the epinephrine to work for the rhytidectomy
(E)The peak absorption of tumescent solution from the abdomen is two hours, and surgery must be completed by this time
(A)The absorption rate of local anesthetic above the clavicles is two times faster than below the clavicles
The absorption of lidocaine from above the clavicles peaks at approximately five to six hours when injected into the neck via tumescent solution. The absorption of the tumescent peaks at approximately 12 hours for the trunk region (the thighs in the reference below). If the tumescent is given for the abdomen and several hours later for the face and neck, then thelidocaine absorption curves could be superimposed and reach a toxic level.
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Local anesthetic absorption in the body by location
The absorption rate of local anesthetic above the clavicles is two times faster than below the clavicles
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Additive effects of local anesthetics
Local anesthetics are additive in their risk and have a certain degree of cross-reactivity in their doses. Mixing a less-than-toxic dose of bupivacaine plus a less-than-toxic dose of lidocaine can add to a toxic effect.
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A 30-year-old woman at 10 weeks’ gestation is brought to the emergency department 30 minutes after she sustained injuries to the right hand during a motor vehicle collision. Physical examination shows an open, volarly displaced, and rotated fracture of the fifth metacarpal. Emergency surgery for reduction of the fracture and closure of the wound is planned. Administration of which of the following drugs should be avoided in this patient?
(A) Bupivacaine
(B) Chloroprocaine
(C) Diazepam
(D) Fentanyl
(E) Morphine
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(C) Diazepam = Category D for pregnancy
Emergency surgery that requires anesthesia must be taken into consideration because there is a likelihood of initiating labor due to stress and because there is also a risk of drug-induced fetal defects, especially during the first trimester. The anesthetic technique of choice is regional anesthesia. Chloroprocaine is hydrolyzed quickly and, therefore, becomes unavailable for transfer across the placenta. Bupivacaine is strongly bound to protein and, therefore, very little drug is available for transfer across the placenta. If systemic drugs need to be given, morphine and fentanyl are preferred.
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Categories of risk for pregnancy for medications
Category A: Controlled studies in women fail to demonstrate a risk to the fetus in the first trimester (and there is noevidence of a risk in later trimesters). The possibility of harm to the fetus seems remote.
Category B: Either animal-reproduction studies have not demonstrated a risk to the fetus but there are no controlled studies in pregnant women, or animal-reproduction studies have shown an adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the first trimester (and there is no evidence of a risk in later trimesters).
Category C: Either studies in animals have shown adverse effects on the fetus (teratogenic or embryocidal or other) and there are no controlled studies in women, or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.
Category D: Evidence of risk to the fetus in humans, but the benefits from use in pregnant women may be acceptable despite the risk (e.g., if the drug is needed in a life-threatening situation or for a serious disease for which safer drugs cannot be used or are ineffective).
Category X: The drug is contraindicated in women who are or may become pregnant
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Who are bentos not safe to give to?
These are FDA pregnancy category D - increased risk of congenital malformations when ingested by the mother during the first trimester of pregnancy.
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What systemic drugs are preferred in pregnancy for anesthesia?
Morphine and fentanyl
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A 46-year-old woman undergoes suction lipectomy of the abdomen using tumescent anesthesia containing lidocaine. Despite doses of lidocaine higher than recommended for local infiltration, toxicity to the drug does not develop in this patient. Which of the following is the most likely explanation?
(A) Chemical structure of lidocaine
(B) pH of the tissue
(C) Rate of lidocaine absorption
(D) Removal of lidocaine by suction
(E) Toxic threshold for plasma lidocaine concentration
(C) Rate of lidocaine absorption
Lidocaine for local infiltration is available in 0.5%, 1%, 1.5%, and 2% solutions that contain epinephrine at a concentration of 1:100,000 or 1:200,000. In contrast, lidocaine for tumescent anesthesia commonly is available in a 0.05% solution that contains epinephrine at a concentration of 1:1,000,000. This dilute solution results in a very slow rate of lidocaine absorption from subcutaneous tissue, which prevents high peak plasma concentrations of the drug as well as toxicity. Although a standard 1% solution yields a maximum plasma concentration of lidocaine in 1 hour, a tumescent solution provides a maximal plasma concentration in 8 to 12 hours.
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Difference in tumescent lidocaine versus local infiltration lidocaine
Lidocaine for local infiltration is available in 0.5%, 1%, 1.5%, and 2% solutions that contain epinephrine at a concentration of 1:100,000 or 1:200,000. In contrast, lidocaine for tumescent anesthesia commonly is available in a 0.05% solution that contains epinephrine at a concentration of 1:1,000,000. This dilute solution results in a very slow rate of lidocaine absorption from subcutaneous tissue, which prevents high peak plasma concentrations of the drug as well as toxicity. Although a standard 1% solution yields a maximum plasma concentration of lidocaine in 1 hour, a tumescent solution provides a maximal plasma concentration in 8 to 12 hours.
74
How much does suction lipectomy reduce the amount of lidocaine?
Suction lipectomy removes some lidocaine, which reduces the peak plasma concentration by approximately 25% (compared with a nonBsuction-lipectomy control).
75
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A 27-year-old woman has a true allergy to a local anesthetic agent used in the past. Use of which of the following local anesthetic agents is most appropriate for this patient?
(A) Benzocaine
(B) Chloroprocaine
(C) Lidocaine
(D) Procaine
(E) Tetracaine
```
(C) Lidocaine
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Amide-type anesthetics include
The amide-type anesthetics lidocaine, bupivacaine, mepivacaine, and prilocaine do not cause true allergic reactions
77
```
Which of the following is LEAST sensitive to increasing plasma levels of lidocaine?
(A) Blood pressure
(B) Central nervous system activity
(C) Heart rate
(D) Muscle tone
```
(A) Blood pressure
78
Blood pressure vs local anesthetics
Blood pressure is typicallyinsensitive to increasing plasma levels of lidocaine and other local anesthetics because a compensatory increase in systemic vascular resistance prevents the blood pressure from increasing
79
Evolution of local anesthetic CNS toxicity
Adverse reactions in the central nervous system are much more common and are biphasic. Initially, an excitatory phase occurs, which may be due to inhibition of the amygdala. This phase may produce muscle twitching in the face and extremities followed by tremors that can progress to seizures. As the amount of local anesthetic increases, a depressive phase occurs and is characterized by drowsiness, unconsciousness, and respiratory arrest
80
Relative cardiac toxicity of local anesthetics
The more lipid-soluble local anesthetics, such as bupivacaine, tend to have a higher toxicity than the less lipid-soluble drugs, such as lidocaine
81
Control of local anesthetic induced seizures
If seizures occur, they are typically controlled with diazepam or midazolam
82
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Which of the following best explains the long duration of bupivacaine when compared with lidocaine?
(A) Lipid solubility
(B) Longer onset of action
(C) pKa
(D) Protein binding
(E) Vasoconstrictor activity
```
(D) Protein binding
83
The duration of action of a local anesthetic is related to:
The duration of action correlates directly with protein binding; ie, greater protein binding results in a longer duration of action. This best explains the long duration of action of bupivacaine when compared with lidocaine; bupivacaine has been shown to be 96% protein-bound, while lidocaine is 64% protein-bound.
84
The potency of a local anesthetic is related to:
The lipid solubility of a local anesthetic determines its potency. Higher solubilityleads to a higher potency drug
85
The onset of action of a local anesthetic is related to:
The pKa is defined as the negative logarithm of the acid ionization constant. This determines the onset of action of a local anesthetic because the uncharged (or base) form is the active component. Local anesthetics with a high pKa have the slowest onset of action because the pKa varies more greatly from the physiologic pH of the drug. Lidocaine, with a pKa of 7.9, has a more rapid onset of action than bupivacaine, which has a pKa of 8.1
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Addition of epinephrine to a local anesthetic does what?
Addition of epinephrine, a vasoconstrictor, to a local anesthetic prolongs the duration of action of the anesthetic and decreases its toxicity. All local anesthetics, with the exception of cocaine, have natural vasodilator activity
87
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An otherwise healthy 5-year-old child who weighs 22 kg sustains a 3-cm laceration of the right arm in a fall. A 1% lidocaine solution is to be injected prior to suturing. What is the maximum safe dose of lidocaine that should be used in this patient?
(A) 5 mL
(B) 10 mL
(C) 15 mL
(D) 20 mL
(E) 25 mL
```
(B) 10 mL
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Max safe dose of lidocaine without epi
4.5 mg/kg
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In a 50-year-old woman who has a history of allergic reaction to tetracaine, which of the following anesthetics should NOT be used?
(A) Bupivacaine
(B) Etidocaine
(C) Lidocaine
(D) Mepivacaine
(E) Procaine
```
(E) Procaine
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Ester type anesthetics include
Ester-type local anesthetics include procaine, benzocaine, chloroprocaine, and tetracaine
91
How do ester type anesthetics produce allergic reactions?
These anesthetics are metabolized by pseudocholinesterase, forming para-aminobenzoic acid (PABA). This compound triggers antibody formation and lymphocyte stimulation to elicit a hypersensitivity reaction. In one study of patients who had no known history of allergy to local anesthetics, 30% of patients developed a positive skin reaction following intradermal injection of an ester-type anesthetic
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Allergic reactions to amides are most likely caused by:
. Any “allergic” reaction to amide-type local anesthetics is most likely caused by methylparaben, a preservative that is structurally related to PABA. Preservative-free local anesthetics are currently available for use in any patient who has sensitivity to methylparaben.
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Trick to help remember which local anesthetics belong to which group
A trick to help remember which complexes belong to which group is that all amides have an “i” in the prefix before the “caine” (ie, bupivacaine, etidocaine, lidocaine, and mepivacaine.
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A 5-year-old boy is brought to the emergency department after sustaining a laceration of the left lower extremity. Physical examination shows an isolated 2-cm lesion extending through the dermis. EMLA cream is applied prior to suturing.The surgeon should wait for how many minutes before suturing the laceration?
(A) 5 minutes
(B) 10 minutes
(C) 20 minutes
(D) 30 minutes
(E) 60 minutes
```
(E) 60 minutes
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A 5-year-old boy is brought to the emergency department 45 minutes after accidentally injecting his palm with epinephrine from an auto-injector (EpiPen). On physical examination, the ring finger is soft and pale, and capillary refill time is poor. A small puncture mark is noted on the flexor surface of the palm just proximal to the metacarpophalangeal (MCP) joint. Which of the following is the most appropriate next step in management?
A) Application of a hot pack
B) Emergent operative exploration
C) Subcutaneous injection of nifedipine
D) Topical nitroglycerin paste
E) Observation
```
E) Observation
Accidental self-injection of epinephrine with an EpiPen occurs in 1 in 50,000 syringes. There have been no documented cases of digital necrosis following injection, and observation is indicated in this case. The effect of epinephrine’s vasoconstriction lasts for approximately 90 minutes and will likely resolve on its own.
Phentolamine has been described as a reversal agent for epinephrine and has shown clinical efficacy, but there has been no study to show that there are better outcomes with phentolamine injection compared with observation. Also, the added volume of injection with phentolamine could cause pressure necrosis and the timing between EpiPen injection and definitive treatment would usually be outside of the 90 minutes it would take for the epinephrine to wear off on its own.
Topical nitroglycerin paste and subcutaneous injection of calcium channel blockers such as nifedipine have not shown to be viable treatment modalities. Application of a hot pack can lead to increased tissue damage and burns and is not indicated. Emergent exploration is indicated for compartment syndrome and is not indicated in this case where the finger is soft
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A 35-year-old man undergoes a 90-minute rhytidectomy procedure with intravenous sedation. The patient smokes 10 cigarettes daily, but is otherwise healthy. Which of the following factors most likely places this patient at increased risk for postoperative nausea and vomiting?
A) Duration of procedure
B) Gender
C) History of cigarette smoking
D) History of postoperative nausea and vomiting
E) Type of anesthesia
D) History of postoperative nausea and vomiting
Risk factors for postoperative nausea and vomiting include: female gender, nonsmoking status, prior history of postoperative nausea/vomiting/motion sickness, use of volatile anesthetics/general anesthesia, opioid/narcotic use, facial rejuvenation procedures, and long duration of surgery.
Several measures can be taken to decrease postoperative nausea and vomiting. A thorough history with identification of risk factors can aid stratification of patients preoperatively. Use of long-acting local anesthetic agents, nonsteroidal anti-inflammatory drugs (NSAIDs), and cyclooxygenase-2 selective inhibitors can decrease the need for postoperative opioid use. Avoidance of nitrous oxide, especially in combination with fentanyl and volatile inhalational gases, and multimodal use of serotonin antagonists combined with other antiemetic agents can also decrease postoperative nausea and vomiting
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A 37-year-old man, who is American Society of Anesthesiologists (ASA) Class 2, comes to the office for evaluation and treatment of human immunodeficiency virus (HIV)–associated lipodystrophy. The patient has a CD4 count of 100 cells/mm3. Autologous fat grafting is planned. Which of the following factors is most likely to increase this patient’s risk of postoperative complications?
A) ASA Class
B) CD4 cell count
C) HIV seropositivity
D) Percutaneous surgery
```
B) CD4 cell count
Higher American Society of Anesthesiologists (ASA) class has been identified as a risk factor for postoperative complications in HIV-positive patients in multiple studies. A patient who is ASA Class 2 has only mild systemic disease. Increasing class number indicates increasing severity of disease (Class 3 – severe systemic disease, Class 4 – severe systemic disease that is a constant threat to life).
Acquired immunodeficiency syndrome (AIDS) is diagnosed when the CD4 count is
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Types of infection not associated with increased risk in HIV patients
Percutaneous surgery, such as fat grafting, has not been associated with increased risk of infection in HIV patients, nor has skin incisional surgery. Transoral mucosal incisional surgery has been found to be associated with a significantly greater risk of wound infection in HIV patients
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A 35-year-old woman comes to the office for consultation on augmentation mammaplasty. During preoperative workup, she reports that her mother has a history of malignant hyperthermia. The patient has never undergone surgery. Which of the following anesthetic agents is most appropriate for this surgery?
A) Desflurane
B) Halothane
C) Isoflurane
D) Propofol
E) Succinylcholine
```
D) Propofol
Propofol can be safely used in patients with a suspected diagnosis of malignant hyperthermia.
Malignant hyperthermia is a rare, life-threatening inherited skeletal muscle disorder that shows symptoms of hypermetabolic reaction to volatile anesthetic gases and depolarizing muscle relaxants. The incidence is between 1 in 5000 to 1 in 100,000 anesthetic encounters. Mortality rates have decreased from 70% to less than 5% as awareness of this condition has led to accurate diagnosis and treatment.
Malignant hyperthermia is genetically transmitted through an autosomal dominant inheritance pattern with variable penetrance. In obtaining a medical history, it is important to document family history of adverse outcomes to general anesthesia. If it is reported that a first-degree relative has had a malignant hyperthermia crisis or susceptibility, then the patient should not be exposed to triggering agents. Anesthetic agents that trigger malignant hyperthermia include: halothane, enflurane, isoflurane, desflurane, sevoflurane, and succinylcholine. Nitric oxide can be used if the anesthesia machine is “vapor-free” and contains no traces of volatile gas. Other safe agents include nondepolarizing muscle relaxants (such as vecuronium, rocuronium, and pancuronium), all ester and amide local anesthetics, ketamine, propofol, etomidate, barbiturates, opiates, and benzodiazepines.
Although it is safe to undergo minor procedures with administration of a topical or local anesthetic agent, patients undergoing complex procedures with intravenous sedation, general anesthesia, or major conduction blockade should be referred to an accredited ambulatory surgical center or hospital. If symptoms are recognized in the operating room (high temperature, increased end-tidal CO2, muscle rigidity), rapid treatment with dantrolene sodium is the highest priority. Acute episodes may require stopping the procedure and transfer to an intensive care unit.
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A 42-year-old woman, with a history of anaphylactic reaction to procaine, comes to the office for consultation regarding augmentation mammaplasty. Anesthetics that contain which of the following should be avoided in this patient?
A) Acetaldehyde
B) Epinephrine
C) Iodine
D) Methylparaben
E) Para-aminobenzoic acid
```
E) Para-aminobenzoic acid
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An otherwise healthy 52-year-old woman with a family history of cardiac disease undergoes suction-assisted lipectomy of the flanks, thighs, and abdomen using a tumescent technique. She returns to the emergency department 6 hours after discharge because of slurred speech and restlessness. Which of the following is the most likely diagnosis?
A) Fat embolism
B) Lidocaine toxicity
C) Parietal stroke
D) Pulmonary embolism
E) Third spacing
```
B) Lidocaine toxicity
Because lidocaine absorbs slowly from fat, infiltrate solutions that contain up to 35 mg/kg of lidocaine are generally considered safe. Nonetheless, lidocaine toxicity is still a risk of the procedure. In tumescent solution with epinephrine, peak plasma lidocaine levels occur approximately 10 to 14 hours after infiltration, and thus, the presentation 6 hours after discharge is consistent with peak plasma concentration.
Lidocaine toxicity has symptoms of neurologic or cardiac toxicity. In the early stages, the complications are primarily neurologic and can include slurred speech, restlessness, tinnitus, and a metallic taste, as well as numbness of the mouth. As the concentrations increase, the neurologic concentrations become more severe, and can progress to muscle twitching, seizures, and cardiac arrest. Treatment of lidocaine toxicity is supportive.
Fat embolism presents as a petechial rash, respiratory dysfunction, and cerebral dysfunction, and the symptoms usually appear 24 to 48 hours after surgery. Pulmonary embolism presents as leg pain and edema, tachycardia, and low-grade fevers.
Parietal strokes usually cause sensory symptoms, self-perception anomalies, and left-right agnosia. Third spacing refers to fluid shifts into interstitial spaces and can cause edema, hypotension, and decreased cardiac output.
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A 40-year-old woman with a history of severe postoperative nausea and vomiting is scheduled for exchange of bilateral breast tissue expanders for permanent silicone implants. Use of which of the following medications is most likely to decrease the chance of postoperative nausea?
A) Bupivacaine
B) Fentanyl
C) Isoflurane
D) Midazolam
E) Nitrous oxide
```
A) Bupivacaine
Addition of local anesthetics during general anesthesia, whether by subcutaneous, tumescent, or regional block infiltration, can result in decreased dosage requirements of the common sedatives and analgesics that can result in nausea and emesis.
Common anesthetic agents that promote nausea and emesis include opioids (fentanyl, hydromorphone, morphine) and inhalationals (halothane, isoflurane, nitrous oxide). Propofol is currently the most commonly used intravenous agent. It does not appear to directly result in nausea, but it has limited analgesic effects. Therefore, effective anesthesia with propofol requires addition of opioid narcotics (which cause nausea) and/or local anesthetics such as lidocaine and bupivacaine (which may decrease the narcotic requirement).
Midazolam is a sedative-hypnotic that has anxiolytic and amnesic effects, both of which are helpful adjuncts to the surgical patient experience. Nausea is possible with midazolam, but less commonly reported than with narcotic and inhalational agents.
The cause of postoperative nausea and vomiting is multifactorial and not fully understood. Strategies for prevention include:
Recognition of high-risk patients (females, nonsmokers, history of motion sickness, previous postoperative nausea, general anesthesia)
Pre- and postoperative treatment with multiple modalities
(such as scopolamine, ondansetron, aprepitant, corticosteroids) Supplemental intraoperative oxygen
and hydration
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A 54-year-old woman has onset of ventricular fibrillation and severe hypotension 5 minutes after 30 mL bupivacaine 0.5% is administered to the ankle for postoperative pain control during reconstruction of the foot. After initiation of cardiopulmonary resuscitation, intravenous administration of which of the following is the most appropriate management?
A) Atropine
B) Dantrolene
C) Flumazenil
D) Lipid emulsion
E) Metoprolol
```
D) Lipid emulsion
The most appropriate management of acute bupivacaine toxicity is a bolus and infusion of 20% lipid emulsion. Every facility where local anesthetic is used in large doses should have a lipid rescue kit clearly labeled and available should the need arise. Although lipid rescue mechanism of action is not completely understood, it may be that the added lipid in the bloodstream acts as a “sink,” allowing for the removal of lipophilic toxins from affected tissues. Major local anesthetic toxicity can have such symptoms as sudden loss of consciousness, tonic-clonic seizures, hypertension followed by progressive hypotension, tachycardia, ventricular fibrillation, bradycardia, asystole, and cardiac arrest. Arrhythmias may be refractory to treatment, and resuscitation may be prolonged, sometimes requiring more than 1 hour.
In the event of a local anesthetic toxicity event, airway management, seizure suppression, and, if needed, cardiopulmonary resuscitation should be performed. Alert the nearest facility having cardiopulmonary bypass capability and administer 20% lipid emulsion (values in parentheses are for 70 kg) as follows:
Bolus 1.5 mL/kg intravenously over 1 minute (~100 mL)
Continuous infusion 0.25 mL/kg/min (~500 mL over 30 minutes)
Repeat bolus every 5 minutes for persistent cardiovascular collapse
Double infusion rate if blood pressure returns but remains decreased
Continue infusion for a minimum of 30 minutes
Although beta-adrenergic blockers may be useful in treating the excitatory cardiovascular phase of local anesthetic toxicity, the potential to progress to more advanced phases with myocardial depression and collapse preclude their routine use. In addition to lipid emulsion, the treatment for local anesthetic–induced cardiac toxicity is generally supportive, and may include amrinone, closed-chest cardiac massage, and cardiopulmonary bypass.
Flumazenil is used to reverse the effects of benzodiazepine toxicity.
Dantrolene is administered in the acute treatment of malignant hyperthermia.
Atropine and dopamine are administered as part of the Advanced Cardiac Life Support protocol for bradycardia or asystole and would not be used in the scenario described.
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A 16-year-old boy who has asthma is brought to the emergency department 3 hours after accidentally injecting the index finger of the nondominant hand with his epinephrine auto-injector. On examination, the finger is cool, pale, and painful. Which of the following drugs works to competitively antagonize the sympathomimetic effects of epinephrine?
A) Lidocaine
B) Marcaine
C) Nitroglycerin paste
D) Phentolamine
E) Prostacyclin
```
D) Phentolamine
Epinephrine use in hand surgery is becoming more common as is the inadvertent self-injection by people who carry epinephrine injectors (EpiPens). Typically, there is little treatment needed other than supportive care. However, when concern for tissue viability is raised or there is marked pain, subcutaneous phentolamine is the drug of choice to reverse the sympathomimetic effects of epinephrine. Plain lidocaine (typically 2% or more) will cause vasodilation but by a different mechanism than the reversal of the epinephrine. Topical nitroglycerin paste has been used for reversal of vasospasm, but again, a different mechanism is used.
Marcaine is an amide anesthetic that inhibits sodium ion channels. It is not an antagonist of epinephrine.
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A 53-year-old woman comes to the office for removal of multiple nevi. On injection of lidocaine, which of the following signs and symptoms is most likely to suggest lidocaine toxicity in this patient?
A) Bronchospasm
B) Hypertension
C) Tachycardia
D) Tinnitus
E) Urticaria
```
D) Tinnitus
Signs and symptoms of lidocaine toxicity include dizziness, agitation, lethargy, tinnitus, metallic taste, perioral paresthesia, slurred speech, euphoria, hypotension, and bradycardia.
Tachycardia is not a sign of lidocaine toxicity. Bradycardia is more common.
Bronchospasm and urticaria are not signs of lidocaine toxicity.
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Signs and symptoms of lidocaine toxicity
Signs and symptoms of lidocaine toxicity include dizziness, agitation, lethargy, tinnitus, metallic taste, perioral paresthesia, slurred speech, euphoria, hypotension, and bradycardia.
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An otherwise healthy 22-lb (10-kg), 2-year-old boy undergoes extirpation of a 5 × 5-cm arteriovenous malformation of the face. To decrease intraoperative blood loss, infusion of which of the following solutions around the lesion is most appropriate?
A) 20 mL of 0.25% bupivacaine with 1:100,000 epinephrine
B) 20 mL of 0.25% bupivacaine with 1:200,000 epinephrine
C) 20 mL of 1.0% lidocaine with 1:100,000 epinephrine
D) 20 mL of 1.0% lidocaine with 1:200,000 epinephrine
E) 20 mL of 1:200,000 epinephrine
The most appropriate solution to infuse around the lesion to decrease intraoperative blood loss is 20 mL of 1:200,000 epinephrine. Although the maximum dose of subcutaneous epinephrine is unknown in a healthy child, large amounts have been shown to be safe in patients undergoing liposuction. The most conservative estimate for the amount of epinephrine (1:200,000) that can be safely injected in this child is 30 mL (3 mL/kg) every 10 minutes. Because this estimate was used in the past when halothane anesthesia was being administered (halothane lowered the arrhythmogenic threshold to epinephrine), greater volumes could likely be infused because other inhalational anesthetics are now used.
Twenty mL of 1% lidocaine or 0.25% bupivacaine with epinephrine cannot be given to this 22-lb (10-kg) child because it exceeds the maximum dose. The maximum dose of lidocaine with epinephrine that can be administered is 7 mg/kg; because the concentration of 1% lidocaine is 10 mg/mL, only 7 mL of this solution could be injected. The maximum dose of bupivacaine with epinephrine that can be given is 3 mg/kg; because the concentration of 0.25% bupivacaine is 2.5 mg/mL, only 12 mL of this solution could be administered.
108
The maximum dose of bupivacaine with epinephrine that can be given is:
The maximum dose of bupivacaine with epinephrine that can be given is 3 mg/kg
109
A 7-year-old boy with a history of anaphylactic reaction to bee stings is brought to the office 45 minutes after epinephrine was mistakenly injected to the tip of the index finger from his automatic injection device. Physical examination of the finger shows swelling, tenderness, and decreased capillary refill. Which of the following is the most appropriate next step in management?
A) Apply a cold compress
B) Apply a warm compress
C) Elevate the extremity
D) Perform a stab incision and saline irrigation
E) Subcutaneously administer an antidote
C) Elevate the extremity
The most appropriate next step in management is elevation of the extremity. Elevation facilitates venous return of the infiltrate, decreases swelling, and minimizes the risk of skin necrosis. The vasoconstrictive effects of epinephrine only last for 60 to 90 minutes; much longer ischemia times are necessary to cause skin necrosis. For example, amputated digits may be successfully replanted after 33 hours of warm ischemia time.
The use of warm or cold compresses on an infiltration site is controversial. Heat may theoretically stimulate the evacuation of the infiltrate through vasodilation and increased blood flow. Ice may theoretically limit the inflammatory reaction as well as the diffusion of the infiltrated substance by causing vasoconstriction. However, warm or cold compresses may worsen tissue damage. Heat can cause thermal injury, and ice can cause ischemia from vasoconstriction, resulting in a “second hit” at the extravasation site. A partial-thickness skin injury may be converted to a full-thickness wound.
Although phentolamine, an alpha-adrenergic antagonist, has been used to treat epinephrine infiltrations, the added volume of phentolamine can worsen the injury. Injection of an antidote adds more fluid to the subcutis and may increase the risk of pressure necrosis. In addition, because epinephrine causes vasoconstriction for only 60 to 90 minutes, its effects have usually worn off by the time the extravasation is noted, the patient is evaluated by a physician, the phentolamine is ordered, and the antidote is obtained from the pharmacy.
Saline flush-out, using stab incisions through which saline is flushed, may be helpful for the infiltration of chemotherapeutic agents, but it requires several incisions and would be considered after elevation of the extremity.
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A 48-year-old woman is evaluated because of a unilateral fixed, dilated, and nonresponsive pupil 1 day after she underwent prophylactic mastectomy and immediate reconstruction with a superior gluteal artery perforator free flap. History includes marked postoperative nausea. Multimodal antiemetic prophylaxis therapy was implemented during the procedure. Which of the following is the most likely causal agent of the fixed and dilated pupil?
```
A) Intravenous dexamethasone
B) Intravenous droperidol
C) Intravenous ondansetron
D) Oral metoclopramide
E) Scopolamine patch
```
E) Scopolamine patch
Postoperative nausea and vomiting (PONV) is a distressing complication of general anesthesia and occurs in 25 to 30% of surgeries. Oftentimes, multimodality treatment is implemented for prophylaxis.
Transdermal scopolamine is a potential long-acting prophylactic antiemetic initially developed to prevent motion sickness but approved in 2001 by the US Food and Drug Administration (FDA) for the prevention of PONV. Scopolamine is a centrally acting anticholinergic agent and is designed as a patch placed behind the ear that will deliver 1.5 mg of scopolamine transdermally at a constant rate over 3 days. It has been shown to be effective in decreasing PONV for up to 24 hours after surgery. Several adverse events can occur including sedation, dry mouth, and blurred vision. In addition, mydriasis, usually ipsilateral to the side of patch application, can occur if direct contamination to the eye occurs from rubbing the eyes after manipulating the patch without hand washing. The diagnosis of scopolamine contamination can be confirmed by placing 0.5 to 1.0% pilocarpine hydrochloride in the affected eye. A dilated pupil from pharmacologic mydriasis will not constrict, whereas a dilated pupil from paralytic mydriasis will constrict. Misdiagnosis can result in an unnecessary and extensive workup for an intracranial etiology.
The other options including dexamethasone, droperidol, metoclopramide, and ondansetron are effective antiemetic agents but have no anticholinergic profile.
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A 23-year-old woman with no history of surgery undergoes augmentation mammaplasty with administration of nitrous oxide, isoflurane, and propofol. Sixty minutes into the procedure, the nurse anesthetist notifies the surgeon that the patient has increasing end-tidal carbon dioxide concentrations, tachycardia, and severe masseter muscle rigidity. Which of the following is the most appropriate next step in management?
A) Administer intravenous saline
B) Administer a muscle relaxant
C) Stop isoflurane
D) Stop nitrous oxide
E) Stop propofol
```
C) Stop isoflurane
The patient is experiencing signs of early malignant hyperthermia, which is a life-threatening crisis and requires immediate attention. The typical symptoms of malignant hyperthermia are caused by a hypercatabolic state with increased heart rate, increased breathing rate, increased carbon dioxide production, increased oxygen consumption, acidosis, masseter muscle rigidity, and rhabdomyolysis. Very high temperature (110.0°F [43.0°C]) usually presents late. Even if treated properly, death may occur as brain damage, muscle damage, renal failure, and multiple organ failure ensue.
The malignant hyperthermia crisis is a biochemical chain reaction response that is “triggered” by commonly used general anesthetics and the paralyzing agent succinylcholine within the skeletal muscles of susceptible individuals. Volatile gaseous inhalation anesthetics like sevoflurane, desflurane, isoflurane, and halothane can trigger malignant hyperthermia. The exact incidence of malignant hyperthermia is not known. Estimates vary from a frequency of one in 5000 to one in 65,000. Over 80 genetic defects have been associated with malignant hyperthermia. Malignant hyperthermia susceptibility is inherited with an autosomal dominant inheritance pattern. Children and siblings of a patient with malignant hyperthermia susceptibility usually have a 50% chance of inheriting a gene defect for malignant hyperthermia.
The medical antidote is dantrolene. Additional methods include use of a hypothermia blanket (under/over the patient) and cold isotonic saline for intravenous solution.
112
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A 53-year-old man is brought to the emergency department after sustaining a laceration of the index flexor digitorum profundus, superficialis, and radial digital nerve of the nondominant left hand. He is scheduled to undergo urgent repair with single-cuff Bier block anesthesia. Which of the following would be the best reason to use an axillary block in this patient?
A) Age
B) Gender
C) Occupation
D) Surgical duration
E) Urgency of surgery
```
D) Surgical duration
The advantages of Bier block include reliability with low incidence of block failure, safety with rapid onset and recovery. The block is limited to tourniquet pain often occurring after 20 to 30 minutes and limits its use to shorter procedures on the upper extremities.
Sudden cardiovascular collapse or seizures may occur if local anesthetic is released into the circulation too early. Disease processes in which a tourniquet is contraindicated include Raynaud disease, sickle cell disease, and severe hypertension. Uncooperative patients and young children are also contraindications.
Short duration procedures, including carpal tunnel release, tendon contracture release, foreign body extraction, and trigger finger release, are examples of procedures where Bier blocks may be considered.
Age, gender, occupation, and urgency of surgery are not contraindications to this procedure. Bier block anesthesia is a contraindication in the very young and very old, but not in a 53-year-old patient.
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Time limit of Bier block surgery
The block is limited to tourniquet pain often occurring after 20 to 30 minutes and limits its use to shorter procedures on the upper extremities
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Contraindications to Bier block surgery
Disease processes in which a tourniquet is contraindicated include Raynaud disease, sickle cell disease, and severe hypertension. Uncooperative patients and young children are also contraindications.
115
```
A previously healthy 38-year-old woman has onset of a brief tonic-clonic seizure 30 minutes after a lidocaine-based tumescent anesthesia is administered during large-volume liposuction of the abdomen, hips, and thighs. After 3 minutes, she has onset of asystole, and cardiopulmonary resuscitation is initiated. She is unresponsive to the standard ACLS resuscitation protocols for asystole. Administration of which of the following is the most appropriate next step?
A) Dantrolene
B) Dimercaprol
C) Lipid emulsion
D) N-acetylcysteine
E) Naloxone
```
C) Lipid emulsion
This is a case of inadvertent lidocaine toxicity with subsequent seizure and cardiac arrest. Furthermore, lipid emulsion has been used with apparent success early in the spectrum of local anesthetic systemic toxicity to preempt cardiac arrest. The role of lipid emulsion has expanded to treatment of cardiac toxicity due to other lipophilic drugs.
Dantrolene is a treatment for malignant hypothermia. Dimercaprol is a chelating agent used for the treatment of heavy metal toxicities. N-acetylcysteine is used as a mucolytic and also in cases of acetaminophen overdose. Naloxone is used to treat narcotic overdose. There are no data to suggest that any of these medications are otherwise helpful in lidocaine toxicity.
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A 5-year-old girl has subcutaneous extravasation of an epinephrine infusion in the upper extremity. On examination 1 hour later, the extremity is swollen, nontender, and well perfused. Which of the following is the most appropriate next step in management?
A)Application of a cold compress
B)Application of a warm compress
C)Elevation of the extremity
D)Incision and saline irrigation
E)Subcutaneous administration of phentolamine
C)Elevation of the extremity
The most appropriate next step in management is elevation of the extremity. Elevation facilitates venous return of the extravasate, reduces swelling, and minimizes the risk of skin necrosis.
The use of warm or cold compresses on the extravasation site is controversial. Heat may theoretically stimulate the evacuation of the infiltrate through vasodilation and increased blood flow. Ice may theoretically limit the inflammatory reaction, as well as the diffusion of the infiltrated substance, by causing vasoconstriction. However, warm or cold compresses may also worsen tissue damage. Heat can cause thermal injury, and ice can cause ischemia from vasoconstriction resulting in a ?second hit? at the extravasation site; a partial-thickness skin injury may be converted to a full-thickness wound.
Although phentolamine, an alpha-adrenergic antagonist, has been used to treat epinephrine extravasation, the added volume of phentolamine can worsen the injury. Injection of an antidote adds more fluid to the subcutis and may increase the risk of pressure necrosis. In addition, because epinephrine causes vasoconstriction for only 60 to 90 minutes, its effects have usually worn off by the time the extravasation is noted, the patient is evaluated by a physician, the phentolamine is ordered, and the antidote is obtained from the pharmacy.
Saline flush out, or using stab incisions through which saline is flushed, may be helpful for the extravasation of chemotherapeutic agents, but it requires several incisions and would be considered only after elevation of the extremity.
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An otherwise healthy 17-year-old boy is brought to the emergency department after sustaining a laceration of the distal middle toe. On examination, the toe is bleeding. Infusion of which of the following local anesthetics is most appropriate at the wound site before repair?
A) 0.5% Lidocaine
B) 1% Lidocaine
C) 1% Lidocaine with sodium bicarbonate
D) 1% Lidocaine with 1:200,000 epinephrine
E) 2% Lidocaine
D) 1% Lidocaine with 1:200,000 epinephrine
The most appropriate local anesthetic to infuse at the wound site before repair is 1% lidocaine with 1:200,000 epinephrine. The addition of epinephrine to the local anesthetic increases the safety of the lidocaine and facilitates the laceration repair. Epinephrine slows the absorption of the local anesthetic, which allows lower doses to be used. Epinephrine also increases the duration of action of lidocaine, which provides longer pain relief. Vasoconstriction from the epinephrine reduces bleeding at the site of the injury, which shortens the operative time, lowers the risk of iatrogenic injury, and facilitates the repair.
Epinephrine is not contraindicated in the fingers or toes. The vasoconstrictive effects of epinephrine only last for 60 to 90 minutes; much longer ischemia times are necessary to cause skin necrosis. For example, amputated digits may be successfully replanted after 33 hours of warm ischemia time.
Although epinephrine diluted to a concentration of 1:1,000,000 (which is commonly used in tumescent solution for liposuction) will cause vasoconstriction, its onset is prolonged and its duration of action is shortened compared with epinephrine 1:200,000.
Lidocaine or bupivacaine without epinephrine does not reduce bleeding at the site of injury, which increases the difficulty of the repair. In addition, without epinephrine, lower doses of local anesthetic must be used, and the patient has a shorter duration of pain relief.
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A 5-year-old girl undergoes repair of a forehead laceration in the emergency department. Administration of ketamine is used for sedation. Which of the following best describes intravenous administration of ketamine when compared with intramuscular administration in this patient?
A)Higher rate of laryngospasm
B)Longer duration of effect
C)Longer time to clinical onset
D)Lower rate of vomiting
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D)Lower rate of vomiting
Ketamine can be administered intravenously or intramuscularly. Intravenous injection is generally safer, and has a lower rate of laryngospasm, shorter duration of clinical onset and effect, and lower rate of vomiting. It can be titrated with a continuous infusion or repeated boluses to effect.
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IV vs IM Ketamine administration: difference in effects
Ketamine can be administered intravenously or intramuscularly. Intravenous injection is generally safer, and has a lower rate of laryngospasm, shorter duration of clinical onset and effect, and lower rate of vomiting. It can be titrated with a continuous infusion or repeated boluses to effect.
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Which of the following medications is most likely to trigger malignant hyperthermia?
A) Dantrolene
B) Isoflurane
C) Nitrous oxide
D) Pancuronium
E) Propofol
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B) Isoflurane
Malignant hyperthermia is a rare but potentially fatal sensitivity to volatile anesthetics and depolarizing neuromuscular blocking agents. A commonly used volatile inhalation agent is isoflurane. Succinylcholine is a depolarizing muscle relaxant frequently present in the operating room. When genetically susceptible individuals are given anesthesia with these agents, the classic findings include skeletal muscle rigidity, tachycardia, fever, cardiac arrhythmias, and metabolic and respiratory acidosis, leading to severe hypotension. Hyperthermia, the hallmark of malignant hyperthermia, is most often a late sign. The earliest signs are tachycardia and an increase in the end-expired carbon dioxide concentration.
Dantrolene is not a trigger for malignant hyperthermia. It is the only drug recommended for the treatment of malignant hyperthermia.
Propofol and nitrous oxide are not malignant hyperthermia triggers. Pancuronium is a non-depolarizing muscle relaxant and is therefore safe to use.
