Complications

Question 1

What is believed to be the reason for the increased teratogenicity of N2O when compared to other inhaled and intravenous anesthetics?

Answer 1

oxidation of vitamin B12 and inactivation of methionine synthase.

Methionine synthase - methyltetrahydrofolate and homocysteine –> tetrahydrofolate (THF) and methionine.

Without THF and methionine –>reduced thymidine synthesis - essential nucleosides for DNA synthesis, its absence damages the genome and could theoretically induce cancer.

Question 2

True or false: desflurane can cause an increased risk for infertility.

Answer 2

False

Question 3

List three risk factors for teratogenesis under anesthesia.

Answer 3

◾The procedure being performed.
◾The proximity of the surgical site to the uterus.
◾The underlying maternal condition that necessitated the surgery

Question 4

What are the JCAHO limits for environmental exposure to volatile anesthetic agents?

Answer 4

less than 2 ppm for volatile anesthetic when used alone, and less than 0.5 ppm when used with N2O.

Question 5

What are the two major causes of waste gas contamination in the operating room?

Answer 5

operator issues (e.g. poorly fitting masks, filling anesthetic vaporizers, flushing the circuit)

equipment issues (e.g. punctured hoses, circuit leaks).

Question 6

During which trimester is a fetus at highest risk for death associated with anesthesia and surgery?

Answer 6

1st

Question 7

Describe the factors that contribute to trauma associated with airway management.

Answer 7

management of a difficult airway –> commonly multiple attempts at laryngoscopy

insertion of adjunctive airway devices - oropharyngeal or nasopharyngeal airways

Inexperience and poor technique increase the risk of airway complications.

Question 8

Name two nerves that can be injured during bag mask ventilation.

Answer 8

mandibular branch of the facial nerve –> transient facial palsy

mental nerves –> lower lip numbness

Question 9

List three common symptoms related to airway trauma.

Answer 9

sore throat
cough
dysphagia and odynophagia

usually self-limited but can progress –> retropharyngeal abscess in the case of a pharyngeal laceration.

Question 10

What two things should you do if a tooth becomes dislodged?

Answer 10

identified and retrieved

CXR if necessary ensure tooth not aspirated or swallowed

Question 11

What is the most common complication of nasotracheal intubation?

Answer 11

Epistaxis

Question 12

A patient presents with hoarseness and unilateral vocal cord paralysis after an uneventful endotracheal intubation. What is the most likely reason?

Answer 12

endotracheal cuff compression of the recurrent laryngeal nerve

Question 13

How can you decrease the risk of recurrent laryngeal injury during endotracheal intubation?

Answer 13

Avoiding overinflation and inappropriate placement of the endotracheal cuff

Question 14

After a difficult intubation a patient develops subcutaneous emphysema, hypotension, increased airway pressures and a mediastinal shift. What is the most likely cause?

Answer 14

tension pneumothorax - after airway perforation

Question 15

What are some signs and symptoms of esophageal perforation?

Answer 15

subcutaneous emphysema, neck pain, odynophagia, dysphagia, fever, cellulitis, empyema, and mediastinitis

Question 16

What is the normal intrathoracic pressure range?

Answer 16

-3 to -10 cm of H2O

Question 17

What are the four common risk factors for Negative Pressure Pulmonary Edema stated in the chapter?

Answer 17

◾Airway lesions.
◾Upper airway surgery.
◾Obesity.
◾Obstructive sleep apnea

postextubation laryngospasm, foreign body, hanging, strangulation, croup, and epiglottitis

Question 18

How does Post-obstructive/negative pressure pulmonary edema occur?

Answer 18

significant upper airway obstruction – for example, biting the endotracheal tube during emergence from anesthesia

Inspiratory effort to overcome the obstruction –> highly negative intrapleural and alveolar pressures –> large pressure gradient that causes fluid to move out of the pulmonary capillaries and into the interstitial and alveolar spaces

Question 19

How many hours should a patient be NPO after a light meal? After clear fluids?

Answer 19

6 hours after a light meal

2 hours after clear fluids

Question 20

Aspirated material is likely to contaminate which bronchus more often?

Answer 20

right main bronchus

Question 21

What are some risk factors for regurgitation, vomiting, and aspiration?

Answer 21

◾Pregnancy after the first trimester.
◾Acute gastrointestinal disease (esophageal or gastric disease, small bowel obstruction, ileus).
◾GI stasis (trauma, diabetes, obesity, drugs that inhibit gastrointestinal function),
◾The head-down and lithotomy positions.
◾Neurologic conditions that impair protective reflexes (Parkinson’s disease, bulbar palsy, myotonia dystrophica, stroke).
◾Decreased level of consciousness (traumatic brain injury, alcohol intoxication, general anesthesia, and drug overdose).

Question 22

With what force should cricoid pressure be applied when the patient of unconscious?

Answer 22

10 N (a weight of about 1 kg, which is tolerable) when the patient is awake and then increasing to 30 N (about 3 kg) when asleep

Question 23

True or false: All patients presenting for surgery should have anti-reflux prophylaxis.

Answer 23

False

Question 24

When aspiration is suspected, how should the patient be positioned?

Answer 24

semi-prone and tilted to a 30° head-down position

Suction –> secure airway –> NG tube
Always suction before giving PVV

Question 25

Aspiration pneumonitis is likely to occur if the volume of aspirate is _____ and the pH is ___.

Answer 25

0.3 mL per kilogram of body weight (20-25 mL in adults) with a pH

Question 26

Antibiotics should be started in a patient who has aspirated and showed signs of pneumonitis for more than ____ hours after the event

Answer 26

48 hours

Question 27

What is the reported occurrence of corneal injury in the perioperative period?

Answer 27

near 0% with adequate protective precautions, and up to 44% with no protective intervention

Question 28

How does general anesthesia interfere with the eye’s natural reflexes to protect the cornea?

Answer 28

masking of pain perception decreased tear production lagopthalmos (failure of eyelid to close) abolishment of Bell’s phenomenon (the upward rotation of the eyeball normally observed during sleep to protect the cornea behind the upper eyelid)

Question 29

Name six risk factors for corneal abrasion.

Answer 29

``` general anesthesia prone (and possibly lateral) positioning prolonged anesthesia/surgery lower ASA physical status advanced patient age less experienced anesthesia care providers ```

Question 30

How does a corneal injury typically present?

Answer 30

foreign-body sensation photophobia pain with blinking or eye movement

Question 31

What is the best preventive measure to avoid corneal abrasion in the perioperative period?

Answer 31

Taping the eyelid closed immediately after induction | Water-based methylcellulose eye ointment

Question 32

Name three different mechanisms for post-operative visual loss.

Answer 32

retinal ischemia anterior ischemic optic neuropathy (AION) posterior ischemic optic neuropathy (PION) - more likely to be related to surgery than AION cortical blindness

Question 33

Describe the fundoscopic exam of central retinal artery occlusion.

Answer 33

normal optic disc, pale retina, and cherry-red macula.

Question 34

What type of retinal ischemia most often occurs due to embolic phenomenon?

Answer 34

Branch retinal artery occlusion

Question 35

A severe head trauma patient complains of post-operative visual loss. What will the fundoscopic exam most likely reveal?

Answer 35

Purtscher retinopathy (cotton wool exudates) = retinal bleeding Also seen in: abdominal trauma acute pancreatitis fat or amniotic fluid embolism

Question 36

What is the prognosis of retinal ischemia visual loss?

Answer 36

most patients sustain permanent visual loss

Question 37

Name the two types of ischemic optic neuropathy and describe the anatomic location of the vascular compromise.

Answer 37

Anterior ischemic optic neuropathy (AION) - at the head of the optic nerve as it passes through the lamina cribrosa to enter the globe; AION acutely affects the optic disc. Posterior ischemic optic neuropathy (PION) - in the retrobulbar portion of the optic nerve.

Question 38

List three high-risk surgeries for AION

Answer 38

cardiac surgery, especially ***CABG*** bilateral radical neck procedures spine, or other orthopedic surgeries ``` Other risk factors: head-down positions (prone or steep Trendelenburg) lower nadir [Hbg] (8.0 g/dL) large volumes of crystalloid lower MAP prolonged surgical time (>500 minutes) possibly, pressor support ```

Question 39

Describe ophthalmic exam findings of AION in the immediate postoperative period.

Answer 39

optic disc edema pale NO pupillary light reflex

Question 40

Describe ophthalmic exam findings of PION in the immediate postoperative period.

Answer 40

initially normal --> pale in following weeks to months Most commonly in spinal fusions

Question 41

List six risk factors for post-operative cortical blindness

Answer 41

``` cardiac and vascular surgeries - emboli cardiac arrest profound hypotension thrombosis vascular occlusion ``` normal optic disc + intact pupillary reflex Prognosis is quite good (unlike ischemic neuropathy)

Question 42

How can pressure injuries from tourniquets be prevented?

Answer 42

Using wider and contoured cuffs lower inflation pressures limiting tourniquet times

Question 43

How can the brachial plexus be injured during a median sternotomy?

Answer 43

compressed against the clavicle during retraction

Question 44

What are signs of possible intraneural injection of local anesthetic during peripheral nerve blockade?

Answer 44

pain on injection low stimulation current abnormal resistance during injection

Question 45

Name the four types of heat transfer that occur in the operating room.

Answer 45

Evaporative - sweating and moisture losses from the airway. (~10%) Conductive - transfer between two adjacent surfaces. Radiation - transfer of heat from one object (the patient) to another (the room), with no contact between the objects. (MAJOR) Convection - heat loss as a result of air currents. (#2)

Question 46

What causes the initial decrease in temperature that occurs during the first hour of surgery?

Answer 46

general anesthesia --> vasodilation --> heat transfer from core to periphery

Question 47

How can hypothermia result in wound infections?

Answer 47

directly impairing immune function | thermoregulatory vasoconstriction --> reduce tissue oxygen delivery = further predisposing patients to wound infection

Question 48

What is the most commonly used medication to treat post-operative shivering?

Answer 48

Meperidine

Question 49

What is the most effective means of maintaining normothermia during longer operations?

Answer 49

Forced-air warming

Question 50

What are the mechanisms by which humans preserve body temperature in warm environments?

Answer 50

sweating - cools the skin through evaporation | increased respiration - eliminates heat through the excretion of warm gas from the lungs

Question 51

List 4 consequences of untreated hyperthermia perioperatively.

Answer 51

tissue destruction --> myoglobinuria coagulopathy - damage to hepatocytes arrhythmias --> cardiac arrest increases the MAC of most anesthetics

Question 52

List 4 potential causes of elevated temperature in an anesthetized patient with an unknown medical history.

Answer 52

1. Infection 2. Metabolic - thyrotoxicosis, pheochromocytoma, status epilepticus, carcinoid syndrome, and malignant hyperthermia 3. Traumatic brain injury 4. Meds - anti-cholinergic, TCAs, MAOIs