Pharm: Exam 4- Local Anesthetics Flashcards

Question

Why is it essential to memorize the "maximum single dose for infiltration" for local anesthetics? A. To avoid systemic toxicity B. To ensure rapid onset of action C. To prevent allergic reactions D. To prolong the duration of anesthesia

Answer 1

Correct Answer: A. To avoid systemic toxicity Rationale: Knowing the maximum single dose for infiltration of local anesthetics is critical to prevent systemic toxicity. Exceeding these limits can result in toxic plasma concentrations, leading to adverse effects ranging from mild systemic symptoms to severe complications like seizures or cardiovascular depression.

Answer 2

Correct Answer: B. Provides a timed release for prolonged duration of action Rationale: Liposome delivery systems can encapsulate a higher amount of local anesthetic and provide a consistent release of the drug in the tissues, thereby prolonging the duration of action and potentially decreasing toxicity.

Answer 3

Correct Answer: C. By binding to voltage-gated sodium channels and inhibiting sodium passage Rationale: Local anesthetics bind to the intracellular portion of voltage-gated sodium channels, inhibiting sodium ion passage through nerve membranes and thus preventing the nerve from reaching the threshold potential necessary for action potential propagation.

Answer 4

Correct Answer: D. Repetitively stimulated nerves Rationale: Repetitive stimulation of nerves increases their sensitivity to local anesthetics, meaning less drug is needed to achieve the desired anesthetic effect.

Answer 5

Correct Answer: B. Converts more local anesthetic to its ionized form, reducing effectiveness Rationale: If a patient is acidotic, the acidic environment will convert more of the local anesthetic to its ionized form, which is less lipid-soluble and less able to penetrate nerve cell membranes to exert its effect.

Answer 6

Correct Answer: D. Preganglionic B fibers Rationale: Preganglionic B fibers are the fastest blocked by local anesthetics, affecting the sympathetic nervous system responses such as blood pressure and heart rate.

Answer 7

Correct Answer: B. The minimum aleveolar concentration (MAC) Rationale: MEC or Cm for local anesthetics is similar to MAC for volatile anesthetics. It represents the concentration needed to achieve a clinical effect without causing systemic toxicity

Answer 8

Correct Answer: D. A pKa value closer to physiologic pH is associated with the most rapid onset of action. Rationale: Local anesthetics with pKa values close to the physiological pH will have a greater proportion of the drug in the non-ionized form at physiological pH, which more readily penetrates nerve membranes, leading to a more rapid onset of action.

Answer 9

Correct Answer: D. Greater systemic absorption Rationale: Intrinsic vasodilator activity of local anesthetics like lidocaine increases local blood flow, which can lead to greater systemic absorption of the drug. With a decrease in potency and shorter duration of action.

Answer 10

Correct Answer: D. Pregnancy is associated with increased sensitivity, requiring careful dosing. Rationale: Pregnant patients often exhibit increased sensitivity to local anesthetics, potentially due to physiological changes that affect the drug's pharmacokinetics and pharmacodynamics, necessitating careful dosing to avoid toxicity.

Answer 11

Correct Answer: D. A and B are correct. Rationale: The site of injection significantly impacts the duration of action for local anesthetics. More vascular sites will have shorter durations due to faster systemic absorption, whereas less vascular sites like subcutaneous tissue will have a longer duration of action.

Answer 12

Correct Answer: B. Intravenous Rationale: According to the hierarchy presented, intravenous injections result in the highest blood concentrations of local anesthetics, due to direct entry into the vascular system.

Answer 13

B. Caudal block

Answer 14

Correct Answer Order: 1.Subcutaneous (Lowest systemic absorption) 2. Epidural 3. Caudal 4.Intravenous (Highest systemic absorption)

Answer 15

Correct Answer: D. Increased lipid solubility is directly related to greater potency of the anesthetic. Rationale: The potency of local anesthetics is directly related to their lipid solubility, as this property enables the drug to penetrate the lipid-rich neuronal membranes more effectively.

Answer 16

Correct Answer: B. Cardiac output and protein binding Rationale: The rate at which a local anesthetic is cleared from the body depends on the cardiac output and the extent to which the drug binds to proteins. An increased cardiac output leads to increased metabolism of the drug, and the percentage bound is inversely related to the percentage available in plasma.

Answer 17

Correct Answer: B. Esters, because they undergo rapid hydrolysis by cholinesterase enzymes in the plasma. Rationale: Esters are generally metabolized more rapidly than amides because they are hydrolyzed by cholinesterase enzymes present in plasma, which occurs faster than the metabolism of amides by liver enzymes.

Answer 18

Correct Answer: A. Amides are not metabolized into para-aminobenzoic acid (PABA), a known allergen. Rationale: Esters can be metabolized into PABA, which is associated with allergic reactions. Amides, on the other hand, do not have this metabolic pathway and thus are less likely to cause allergic reactions.

Answer 19

Correct Answer: B. Decreased rate of clearance due to reduced cardiac output and protein plasma levels. Rationale: As individuals age, they typically experience a decrease in cardiac output and a reduction in protein plasma levels, which can lead to a slower rate of clearance for local anesthetics, necessitating a lower dose to avoid toxicity.

Answer 20

Correct Answer: B. Prilocaine Rationale: According to the slide, Prilocaine, classified under amides, has a protein binding of 55% and a maximum single dose for infiltration of 400 mg on chart but slide 32 says 600mg so who fucking knows.

Answer 21

Correct Answer: A. 300 mg, 70% Rationale: Lidocaine, which is an amide local anesthetic, has a maximum single dose for infiltration of 300 mg and a protein binding percentage of 70%.

Answer 22

Correct Answer: C. Prilocaine Rationale: The slide indicates that among the listed amides, Prilocaine is metabolized at the most rapid rate by liver microsomal enzymes.

Answer 23

Correct Answer: B. Esters Rationale: Esters are primarily metabolized by hydrolysis through cholinesterase enzymes in the plasma, as mentioned in the slide. An exception is cocaine, which is metabolized in the liver.

Answer 24

Correct Answer: B. Approximately 10-12% Rationale: Unlike most local anesthetics that are metabolized before renal excretion, cocaine has a unique characteristic where 10-12% can be excreted unchanged in the urine.

Answer 25

Correct Answer: C. Lidocaine D. Mepivacaine Rationale: Lidocaine has an intermediate rate of metabolism when processed by liver microsomal enzymes, alongside Mepivacaine.

Answer 26

Correct Answer: C. Poor water solubility of the drugs Rationale: Local anesthetics are typically weak bases with poor water solubility, which means that a relatively small amount of the unchanged drug can be excreted through the kidneys. As the slides indicate, less than 5% of the unchanged drug is usually found in the urine, primarily due to their poor solubility in water. This means that most of the drug is metabolized before it is excreted.

Answer 27

Answer: B. Esters Rationale: Esters are rapidly hydrolyzed by plasma cholinesterases, and lower levels of these enzymes during pregnancy would affect the metabolism of ester local anesthetics.

Answer 28

Answer: C. They have higher protein binding, potentially leading to greater fetal accumulation. Rationale: Higher protein binding in the fetus can result in more of the drug being retained, and the significant transplacental transfer of amides compounds this effect.

Answer 29

Answer: C. Fetal acidosis can lead to nonionized local anesthetics becoming ionized within the fetus, leading to accumulation. Rationale: Nonionized forms of local anesthetics cross the placental barrier but may become ionized in the acidic environment of the fetal bloodstream, leading to accumulation since the ionized form cannot easily cross back into the maternal circulation.

Answer 30

Answer: A. Administering bicarbonate to the mother Rationale: Administering bicarbonate to the mother can help correct fetal acidosis, potentially reducing the ion trapping of local anesthetics in the fetus.

Answer 31

Answer and Rationale: C. Lidocaine’s maximum recommended infiltration dose is 300 mg when used without epinephrine and 500 mg when combined with epinephrine. Rationale: The correct answer is C. The slide indicates that Lidocaine undergoes oxidative dealkylation in the liver, not the kidneys, making A incorrect. Hepatic disease does indeed affect the metabolism and elimination of Lidocaine, which rules out B. D is incorrect as the slide specifies that Lidocaine has anti-dysrhythmic properties. Therefore, the correct statement is C, as it accurately reflects the information given on the maximum doses of Lidocaine with and without epinephrine.

Answer 32

Answer and Rationale: B. 140 mg IV over 5 minutes Rationale: Methemoglobinemia can occur when Prilocaine is metabolized to its metabolite, orthotoluidine, which then converts hemoglobin to methemoglobin, reducing the oxygen-carrying capacity of the blood and leading to symptoms like cyanosis. The treatment for methemoglobinemia is Methylene Blue, administered at 1-2 mg/kg IV. Given the patient's weight of 70 kg, and not exceeding the total dose limit of 7 to 8 mg/kg as stated on the slide, the maximum recommended dose would be 70 kg x 2 mg/kg = 140 mg given over 5 minutes, which corresponds to answer B. A is underdosed

Answer 33

Answer and Rationale: C. Prolonged elimination in fetus and newborn. Rationale: Mepivacaine is similar to Lidocaine in many respects; however, it lacks vasodilatory activity, which confers a longer duration of action. Another distinguishing factor is that Mepivacaine has prolonged elimination in the fetus and newborn, and hence, it is not typically used for obstetrical anesthesia (OB). This characteristic is highlighted in the slide as a key difference, making option C the correct answer. Options A and B are incorrect as they describe properties that are not associated with Mepivacaine when compared to Lidocaine. Option D is incorrect as the slide does not discuss the metabolism of Mepivacaine via N-dealkylation; this is mentioned in relation to Bupivacaine.

Answer 34

Answer: C. Lidocaine Rationale: Lidocaine’s maximum recommended doses are 300mg for plain and 500mg when combined with epinephrine, to slow absorption and prolong the effect.

Answer 35

Answer: C. Prilocaine Rationale: Prilocaine’s metabolite orthotoluidine can convert hemoglobin to methemoglobin, leading to methemoglobinemia at high doses.

Answer 36

Answer: B. Amides, not esters, have significant transplacental transfer Rationale: Esters are rapidly hydrolyzed by plasma cholinesterases, reducing their transplacental transfer compared to amides. Protein binding also affects the rate and degree of diffusion across the placental barrier.

Answer 37

Answer: D. Bupivacaine and C. Ropivacaine Rationale: Bupivacaine has a high protein binding capacity, particularly to α1-acid glycoprotein, influencing its duration of action and metabolism.

Answer 38

Answer: C. Ropivacaine

Answer 39

Answer: C. Atypical pseudocholinesterase Rationale: The Dibucaine number is a measure of the inhibition of plasma cholinesterase activity by Dibucaine and is used to diagnose atypical forms of the enzyme that are associated with prolonged paralysis after the administration of Succinylcholine.

Answer 40

Answer: B. Ropivacaine Rationale: Ropivacaine's metabolites can accumulate in uremic patients, which is a concern due to the potential for systemic toxicity. However, Ropivacaine has lesser systemic toxicity overall compared to Bupivacaine.

Answer 41

Answer: B. Chloroprocaine Rationale: Chloroprocaine is hydrolyzed 3.5 times faster than procaine by plasma cholinesterase, making it the ester local anesthetic with the fastest hydrolysis rate.

Answer 42

Answer: C. Para-aminobenzoic acid (PABA) Rationale: The metabolism of ester local anesthetics such as procaine, chloroprocaine, and tetracaine results in the production of PABA, which is excreted unchanged in the urine.

Answer 43

Answer: B. Decreases activity by 40% Rationale: Pregnancy is associated with a 40% decrease in plasma cholinesterase activity, which could affect the metabolism of local anesthetics that are hydrolyzed by this enzyme.

Answer 44

Answer: C. It is a weak acid which makes it predominantly nonionized at physiological pH, potentially causing Methemoglobinemia if overdosed. Rationale: Benzocaine is unique because it is a weak acid with a pKa of 3.5, making it predominantly nonionized at the physiological pH of 7.4. This is in contrast to most local anesthetics, which are weak bases. A potential complication of Benzocaine is Methemoglobinemia, which can occur with doses exceeding 200-300mg. Methemoglobinemia is a condition where hemoglobin is modified into methemoglobin, which cannot effectively release oxygen to tissues, leading to hypoxia.

Answer 45

Answer: B) Parturients Rationale: Cocaine is metabolized by plasma and liver cholinesterases. Plasma cholinesterase activity is decreased in parturients (those about to give birth), neonates, the elderly, and those with severe hepatic disease. This affects the metabolism and clearance of cocaine in these populations.

Answer 46

Answer: C) 60 minutes Rationale: The peak effect of Cocaine occurs between 30 to 45 minutes after administration, and the duration of action lasts for about 60 minutes post-peak.

Answer 47

Answer: C) 24 to 36 hours Rationale: After its effect peaks, Cocaine is eliminated in the urine within 24 to 36 hours.

Answer 48

Answer: B) Coronary vasospasm Rationale: Cocaine can cause significant cardiovascular effects such as coronary vasospasm, ventricular dysrhythmias, hypertension (HTN), tachycardia, and can aggravate coronary artery disease (CAD). These risks warrant caution during its use.

Answer 49

Answer: C) It increases the percentage of the lipid-soluble or non-ionized form of LAs. Rationale: Alkalization of LA solutions is used to increase the percentage of the drug that is in a lipid-soluble or non-ionized form, which can more easily diffuse across nerve membranes.

Answer 50

Answer: B) Faster onset of action Rationale: By increasing the lipid-soluble or non-ionized form of LAs through alkalization, the onset of the anesthetic action is faster. This also enhances the depth and increases the spread of epidural blockage.

Answer 51

Answer: C) Speeds onset by 3 to 5 minutes Rationale: Alkalizing local anesthetic solutions can reduce the time it takes for peripheral and epidural blocks to take effect, typically speeding the onset by 3 to 5 minutes.

Answer 52

Answer: A) More Ionized Rationale: Weak acids are more ionized when the environmental pH is higher than their pKa, as they will have donated their protons. A weak acid has a charge when it donates a proton

Answer 53

Answer: A) Mostly nonionized Rationale: Weak bases are predominantly nonionized at pH levels above their pKa because they will have donated protons and weak bases have no charge when they are unprotonated

Answer 54

Answer: B) Mostly non-ionized Rationale: Weak acids with a pKa significantly higher than the physiological pH will not donate protons bc the environment is more acidic, and an acid with its proton is not charged and therefor unionized .

Answer 55

Answer: b) Mostly non-ionized Rationale: Since thiopental's pKa is close to but slightly higher than physiological pH, it will tend to be more keep its protons and thus make it non-ionized. Note if this was a base, a base that accepts protons is charged and ionized, that is why LA's are in effective in acidic tissue

Answer 56

Answer: A) In the ionized form Rationale: Weak bases are more likely to be ionized in environments where the pH is lower than their pKa. At pH 7.4, Drug V with a pKa of 9.1 will be more in the ionized form, meaning it has accepted protons.

Answer 57

Answer: D) Dexmedetomidine Rationale: Dexmedetomidine is a selective α2-adrenergic agonist that, when used intravenously, has been shown to prolong the duration of motor and sensory blocks. It can also delay the first analgesic request after spinal anesthesia, which makes it a valuable adjuvant in enhancing the efficacy of local anesthetics during various procedures. Other options listed such as magnesium, clonidine, ketamine, and dexamethasone also serve as adjuvants to local anesthetics, each with its unique properties and benefits. Magnesium is often used to prolong the duration of spinal anesthesia with or without opioids. Clonidine and ketamine can be useful in pediatric regional anesthesia for their sedative properties and pain modulation effects, respectively. Dexamethasone has been found to prolong block duration when administered intravenously or mixed with local anesthetics.

Answer 58

Answer: C) Clonidine and Ketamine

Answer 59

Answer: C) Magnesium

Answer 60

D) Dexmedetomidine

Answer 61

D) Production of a rapid onset Rationale: Combining Chloroprocaine, a fast-acting anesthetic, with Bupivacaine, which has a longer duration, can produce a rapid onset while maintaining prolonged anesthesia.

Answer 62

Answer: D) Both A and B are correct Rationale: Alkalinization with sodium bicarbonate increases the proportion of the non-ionized form of the anesthetic, enhancing its ability to penetrate nerve membranes, thus speeding up the onset.

Answer 63

Answer: D) The toxic effects Rationale: Toxic effects of local anesthetics are additive; hence, combining different local anesthetics requires careful dosing to prevent systemic toxicit

Answer 64

Answer: B) Precipitation and instability of the solution Rationale: Over-alkalinization can cause precipitation, which can compromise the efficacy and safety of the anesthetic solution.

Answer 65

Correct Answer: B) 225 mg Rationale: 40% of the maximum dose of Lidocaine (300 mg) is 120 mg, and 60% of the maximum dose of Bupivacaine (175 mg) is 105 mg. Adding these together gives a total of 225 mg, which is below the maximum dose for each drug individually to prevent additive toxicity.

Answer 66

Correct Answer: C) Lidocaine 120 mg and Bupivacaine 105 mg Rationale: Both A) and D) exceed the safety margin when drugs are combined, with D) being the maximum dose of each drug if used alone, which could lead to systemic toxicity. C) uses the 40% of Lidocaine's maximum dose and 60% of Bupivacaine's maximum dose, summing up to 225 mg, which is within the safe combined dosage limit.

Answer 67

Correct Answer: D) Bupivacaine Rationale: The image indicates that for Bupivacaine, the recommended maximum single dose is 175 mg, but this can be increased to 225 mg when combined with epinephrine, which is used to prolong the anesthetic effect and reduce systemic absorption.

Answer 68

Correct Answer: B) 300 mg Rationale: According to the table, Lidocaine can be administered up to a maximum single dose of 300 mg for infiltration without the addition of epinephrine. 500mg w/ epi

Answer 69

B) 500 mg 400 without

Answer 70

Correct Answer: A) 5 mcg/mL Rationale: A 1:200,000 epinephrine solution means that there is 1 gram of epinephrine in 200,000 mL of solution. Converting 1 gram to 1,000,000 mcg and then dividing by 200,000 mL yields a concentration of 5 mcg/mL.

Answer 71

Correct Answer: C) 1% Rationale: Local anesthetic concentrations are often given in percentage form. A 1% solution means there is 1 gram of anesthetic in 100 mL of solution, which is equivalent to 10 mg/mL.

Answer 72

Correct Answer: C) 1,000 mcg Rationale: A 1:1,000 ratio means 1 gram of epinephrine is diluted in 1,000 mL. Since 1 gram is equal to 1,000,000 mcg, dividing by 1,000 mL gives you 1,000 mcg/mL.

Answer 73

Correct Answer: D) 4% Rationale: The higher the percentage, the higher the concentration of the anesthetic agent. Therefore, a 4% solution has a higher concentration (40 mg/mL) compared to the others listed and would provide a more potent effect.

Answer 74

Answer: C. 160 mg Rationale: A 4% solution means 4 grams per 100mL, or 40mg per mL. Thus, in a 4mL syringe, the total dose is 40mg/mL x 4mL = 160mg.

Answer 75

Answer: C. When injected into tissues supplied by end arteries Rationale: Epinephrine causes vasoconstriction, which can lead to ischemia and potential necrosis in areas with end-arterial blood supply, such as fingers, toes, ears, nose, and penis.

Answer 76

Answer: C. Cocaine Rationale: Cocaine causes localized vasoconstriction, which can help to decrease blood loss and improve surgical visualization.

Answer 77

Answer: C. It contains prilocaine, which can exacerbate methemoglobinemia. Rationale: Prilocaine, one of the components of EMLA, can lead to the formation of methemoglobin, a form of hemoglobin that is unable to carry oxygen efficiently.

Answer 78

Answer: B. 5% Rationale: EMLA cream contains a eutectic mixture of 2.5% lidocaine and 2.5% prilocaine, totaling 5% local anesthetic.

Answer 79

Answer: C. 2 hours Rationale: EMLA cream typically requires 2 hours to take effect for skin grafting procedures.

Answer 80

Answer: B,C,D Rationale: EMLA cream requires the shortest onset time of 10 minutes for procedures like cautery of genital warts.

Answer 81

Answer: B. 10 cm² Rationale: The recommended dose for EMLA cream is 1 to 2 grams per 10 cm² of skin area.

Answer 82

Answer: C. Lidocaine and prilocaine Rationale: EMLA is a eutectic mixture of lidocaine and prilocaine, both present at 2.5% concentration.

Answer 83

Answer: A. EMLA Rationale: EMLA cream is not recommended for application on skin wounds.

Answer 84

Answer: D. Amethocaine Rationale: Amethocaine is described as EMLA-like, implying it's a mixture similar to EMLA which is a eutectic mixture of lidocaine and prilocaine.

Answer 85

Answer: B. Patients with allergies to amide-type local anesthetics Rationale: EMLA cream contains amide-type local anesthetics, so it is contraindicated in patients with allergies to these compounds. C/I in amide allergies

Answer 86

Answer: C. 7% Rationale: The slide lists Lidocaine 7% as one of the alternative preparations for topical anesthesia.

Answer 87

Answer: C. To double the duration of anesthesia Rationale: Epinephrine is added to local anesthetics to prolong their action by causing vasoconstriction, which slows the systemic absorption of the drug.

Answer 88

Answer: B. 0.25% Rationale: The slide indicates that Ropivacaine is used at a concentration of 0.25% for local infiltration at an inguinal operative site.

Answer 89

Answer: C. Subcutaneous Rationale: Local infiltration involves the extravascular placement of a local anesthetic, typically by subcutaneous injection.

Answer 90

Answer: B. Diffuses from outer mantle to central core of nerve Rationale: The MOA of LAs in peripheral nerve blocks is based on diffusion from the outer layers of the nerve (mantle) to the inner layers (core), utilizing a concentration gradient to exert an anesthetic effect.

Answer 91

Answer: C. Autonomic, sensory, motor Rationale: Typically, the smallest sensory and autonomic nervous system (ANS) fibers are anesthetized first because they are more easily penetrated by the anesthetic due to their size and myelination status.

Answer 92

Answer: B. Proximal Rationale: Sensation typically returns in the reverse order of the block; therefore, the area that was anesthetized last (distal) is usually the last to recover, making the proximal areas the first to regain sensation.

Answer 93

Answer: D. Fingers Rationale: In an interscalene block, anesthesia is applied to the brachial plexus, which affects the shoulder first and then spreads distally, with the fingers being the last to be numbed.

Answer 94

Answer: C. The pKa of the local anesthetic Rationale: The onset of action (OOA) for local anesthetics is dependent on the pKa of the drug, which determines the proportion present in the nonionized, lipid-soluble form that can diffuse across nerve membranes.

Answer 95

Answer: B. It has a lower pKa Rationale: Lidocaine has a faster onset of action because its pKa (7.9) is closer to the physiological pH, resulting in a higher proportion of the drug in the nonionized, lipid-soluble form. Bupivacaine is (8.1)

Answer 96

Answer: D. All of the above Rationale: The duration of a nerve block can be significantly extended by adding adjuncts such as epinephrine, fentanyl, or clonidine, which help prolong the anesthetic effect.

Answer 97

Answer: C. Improve pain control and patient satisfaction Rationale: Continuous infusion blocks often use additives and are associated with improved pain control, less nausea, and greater patient satisfaction compared to single-injection blocks.

Answer 98

Answer: B Rationale: The local anesthetic should be deposited in the paraneural sheath surrounding the nerve for effective diffusion and nerve block without damaging the nerve fibers directly.

Answer 99

Answer: B Rationale: The paraneural sheath is the target for local anesthetic deposition. Visualizing it ensures that the local anesthetic will surround the nerve, leading to an effective block.

Answer 100

Answer: A Rationale: Local anesthetics typically appear hypoechoic or darker on ultrasound, indicating appropriate distribution around the nerve when correctly injected.

Answer 101

Answer: B. To prevent systemic spread of the local anesthetic. Rationale: Exsanguination, which involves elevating the extremity and using a bandage or esmarch to expel blood, is used in a Bier Block to create a bloodless field and to help localize the effects of the local anesthetic to the extremity.

Answer 102

Answer: A. To have a backup in case one cuff fails. Rationale: A double cuff is used to provide a safety margin in case one cuff deflates unintentionally, which could allow local anesthetic to enter systemic circulation and increase the risk of toxicity.

Answer 103

C. IV start, exsanguination, double cuff ,LA injection, IV D/C

Answer 104

Answer: C. Sympathetic nervous system (SNS) fibers Rationale: The sequence of blockade typically starts with the SNS fibers due to their myelination and smaller size, which makes them more susceptible to the effects of local anesthetics.

Answer 105

Answer: B. SNS, Sensory, Motor Rationale: The sequence of blockade typically follows the order of sympathetic (leading to hypotension, bradycardia), then sensory (affecting pain and temperature sensation), and finally motor blockade.

Answer 106

Answer: C. Motor fibers Rationale: Motor fibers are typically the last to be affected by local anesthetics during a neuraxial block due to their larger size and the myelination of the Aδ fibers which transmit proprioception and motor function.

Answer 107

Answer: B. 15-30 minutes Can speed it up to 3-5 min by adding bicarb and alkalizing it. Rationale: Epidural anesthesia typically has a 15-30 minute delay in onset due to the slow diffusion of the local anesthetic through the dura to act on nerve roots and the spinal cord.

Answer 108

Answer: C. Lidocaine Rationale: Lidocaine is most commonly used for epidural anesthesia because it diffuses well through tissues and has a relatively rapid onset.

Answer 109

Answer: B. It has no advantage in terms of duration. Rationale: Adding epinephrine to bupivacaine in epidural anesthesia does not provide an advantage in extending the duration of action.

Answer 110

Answer: C. 24-48 hours Rationale: The effects of an epidural block on the fetus can last for 24-48 hours due to the crossing of the local anesthetic through the placental barrier.

Answer 111

Answer: B. SNS blockade is 2 spinal segments cephalad, and motor blockade is 2 segments below the sensory level. Rationale: In spinal anesthesia, the blockade of the SNS usually occurs 2 segments above the level of sensory denervation, while motor blockade typically occurs 2 segments below.

Answer 112

Answer: C. Typically involves larger doses due to more systemic absorption. Rationale: Epidural anesthesia requires larger doses than spinal anesthesia because the local anesthetic must diffuse through the dura mater to reach the nerve roots, leading to more systemic absorption.

Answer 113

Answer: C. More pronounced on the right side. Rationale: Hyperbaric solutions are denser than CSF and will gravitate to the lowest point due to gravity. Therefore, positioning the patient on their right side will result in the local anesthetic settling more on that side, intensifying the block there.

Answer 114

Answer: B. T8 Rationale: The sympathetic nervous system blockade occurs two segments above the sensory level. So, for a sensory block at T10, the SNS blockade would be at T8.

Answer 115

Answer: B. 100 mg Rationale: The maximum recommended dose of lidocaine for spinal anesthesia is 100 mg, considering the safety profile and potential for systemic toxicity.

Answer 116

Answer: D. The height of the patient Rationale: The dosage of local anesthetic for an SAB is tailored primarily according to the height of the patient because it correlates with the volume of the subarachnoid space, influencing the spread of the drug.

Answer 117

Answer: B. 1.5 mL Rationale: The guideline suggests 1 mL of 0.75% bupivacaine for a 5-foot patient, with an additional 0.1 mL for every inch above 5 feet, which equals 1.5 mL for a person who is 5 feet 5 inches tall.

Answer 118

Answer: C. It determines the spread of the drug within the cerebrospinal fluid (CSF). Rationale: The specific gravity of the local anesthetic solution relative to CSF is a crucial factor in determining the cephalad or caudad spread of the drug within the subarachnoid space. Hyperbaric solutions will sink, and hypobaric solutions will rise.

Answer 119

Answer: B. 2 mL Rationale: The text indicates a maximum of 2 mL total for a patient of any height over 5 feet, with 1 mL for the base height and 0.1 mL for each additional inch.

Answer 120

B. Bupivacaine has a reduced effect on the fetus due to protein binding. Rationale: Bupivacaine has limited crossing of the placental barrier due to its lipid solubility and protein binding. This is an advantage in obstetric anesthesia as it reduces the potential effect on the fetus compared to less protein-bound local anesthetics like Lidocaine, which will cross more readily.

Answer 121

Answer: B. There is no differential zone of SNS blockade with epidurals. Rationale: Unlike subarachnoid blocks, where the SNS blockade is typically two spinal segments cephalad to the sensory level, epidural anesthesia does not create a differential zone of SNS blockade.

Answer 122

Answer: B. To produce vasoconstriction and minimize blood loss Rationale: Epinephrine causes vasoconstriction when added to the dilute lidocaine solution in tumescent liposuction, which decreases bleeding and allows for clearer visibility during the procedure. It also contributes to prolonged postoperative analgesia due to the reduced systemic absorption of lidocaine.

Answer 123

Answer: C. 12 to 14 hours post-injection Rationale: The peak plasma concentration of lidocaine occurs 12 to 14 hours after injection due to the slow and sustained release from the subcutaneous tissues, necessitating careful monitoring for signs of lidocaine toxicity.

Answer 124

Answer: C. Taut stretching of the skin due to large volume infiltration Rationale: The tumescent technique involves infiltrating large volumes of a dilute lidocaine and epinephrine solution into subcutaneous tissues, causing taut stretching of the overlying skin, vasoconstriction, and subsequent bloodless aspirates, which aids in fat removal and provides extended postoperative analgesia.

Answer 125

Answer: B. 7 mg/kg Rationale: For regional anesthesia using lidocaine with epinephrine, the recommended dosage is 7 mg/kg. This dosage takes into account the "mega-dose" approach of the tumescent technique, which allows for the use of higher total doses of lidocaine due to its slow systemic absorption and "tissue buffering system."

Answer 126

Answer: C. 35 to 55 mg/kg Rationale: The tumescent technique for liposuction utilizes a "mega-dose" of highly diluted lidocaine, often ranging from 35 to 55 mg/kg. This high dosage is possible because the lidocaine is infused into the subcutaneous tissue and absorbed slowly, thereby reducing peak plasma concentrations and minimizing the risk of toxicity. However, close monitoring is still essential due to the delayed peak plasma levels.

Pharm: Exam 4- Local Anesthetics Flashcards

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