Lippincott's Anesthesia Review: 1001 Questions and Answers
Chapter 20. Postoperative Anesthesia Care
Sheri Berg and Edward Bittner
1. The most common cause of postanesthesia care unit (PACU)–related malpractice claims is
A. Undertreated pain
B. Critical respiratory incidents
C. Nerve injury from regional blocks
D. Cardiovascular events
2. Which of the statements regarding the American Society of Anesthesiologists (ASA) Standards for Postanesthesia Care is true?
A. A physician is responsible for the discharge of a patient from the postanesthesia care unit (PACU)
B. Medical supervision and coordination of patient care in the PACU should be the responsibility of an anesthesiologist
C. Use of a PACU scoring system is recommended
D. All of the above
3. The most common cause of postoperative airway obstruction is
A. Loss of pharyngeal tone in a sedated patient
B. Weak diaphragmatic contraction
C. Redundant pharyngeal tissue
D. Laryngeal edema
4. A 36-year-old man who underwent a laparoscopic cholecystectomy develops upper airway obstruction in the PACU. You suspect that residual neuromuscular blockade is a major contributing factor. Which of the following would exclude the presence of residual neuromuscular blockade?
A. Oxygen saturation of 98% on 2-L nasal cannula
B. Normal tidal volumes while spontaneously breathing
C. Normal end-tidal carbon dioxide concentration while spontaneously breathing
D. None of the above
5. After reversal of neuromuscular blockade, pharyngeal function returns to baseline when the adductor pollicis train-of-four (TOF) ratio is greater than
6. Which of the following is considered the “gold standard” when using clinical assessment to evaluate for residual neuromuscular blockade?
A. Tongue protrusion
B. Ability to lift the head off the bed for 5 seconds
C. Ability to lift the legs off the bed for 5 seconds
D. Hand-grip strength
7. Which of the following metabolic states can contribute to residual neuromuscular blockade?
8. You are called to evaluate a 14-year-old girl in the postanesthesia care unit (PACU) with decreased oxygen saturation. The nurse tells you her anesthesia team “extubated her deep.” You determine that she is in laryngospasm. Which of the following would be the most appropriate first step in her management?
A. Wait for 5 minutes, watch her, and reassess
B. Administer 2 mg/kg of propofol
C. Provide a jaw thrust and apply continuous positive airway pressure (CPAP)
D. Administer 0.5 mg/kg of succinylcholine
9. A 40-year-old woman undergoes an 8-hour spine surgery and is left intubated for concern of airway edema. Which of the following statements regarding the assessment of airway edema is correct?
A. The absence of facial edema excludes the presence of airway edema
B. The presence of air movement around the endotracheal tube with the cuff deflated excludes the presence of airway edema
C. The absence of scleral edema excludes the presence of airway edema
D. The cuff-leak test cannot exclude the presence of airway edema
10. Strategies to reduce the risk of airway obstruction in patients with obstructive sleep apnea (OSA) include all of the following, except
A. Administration of benzodiazepines in place of opioids to reduce anxiety
B. Application of postoperative continuous positive airway pressure (CPAP)
C. Use of continuous regional anesthetic techniques
D. Preoperative screening to identify patients at high risk
11. You are called to evaluate a 65-year-old man in the postanesthesia care unit who underwent a left-carotid endarterectomy earlier in the day. He is having difficulty breathing, and you notice that the left side of his neck appears swollen. As you examine him, he becomes agitated and his oxygen saturation decreases to 92%. You ask for the surgeon be called “stat” and attempt bag mask ventilation. The next step to take is
A. Wait for the surgeon to arrive
B. Release the sutures and evacuate the hematoma
D. Administer naloxone
E. Apply noninvasive ventilation
12. The most common cause of transient postoperative hypoxemia in the postanesthesia care unit (PACU) is
C. Alveolar hypoventilation
D. Pulmonary embolus
13. For every 1-mm Hg increase in arterial PaCO2, minute ventilation increases by
A. 0.5 L/min
B. 1 L/min
C. 2 L/min
D. 4 L/min
14. Which of the following is not a cause of arterial hypoxemia in the postanesthesia care unit?
A. Decreased alveolar partial pressure of oxygen
B. Ventilation-to-perfusion mismatch
D. Decreased venous admixture
15. A healthy 21-year-old college football player is admitted to the postanesthesia care unit with hypoxemia after undergoing an Achilles tendon repair. The patient developed laryngospasm after extubation in the operating room, which resolved after application of positive pressure. What is the likely cause of his pulmonary edema?
A. Cardiovascular dysfunction
C. Postobstructive pulmonary edema
D. Volume overload
16. Administration of 5 L/min of oxygen by nasal cannula results in an FIO2 delivery of
17. Which of the following postoperative hemodynamic abnormalities is the most predictive of unplanned ICU admission and mortality
18. The most common cause of systemic hypotension in the postanesthesia care unit (PACU) is
A. Intravascular volume depletion
B. Myocardial ischemia
C. Residual anesthetic effects
19. A sympathetic block above which level can result in bradycardia and hypotension?
20. Which of the following statements regarding a perioperative anaphylactic reaction is most correct?
A. Vasopressin is the drug of choice to treat anaphylaxis
B. The absence of bronchospasm and rash excludes the diagnosis of anaphylaxis
C. Low serum tryptase concentrations can differentiate between anaphylactic and anaphylactoid reactions
D. Neuromuscular-blocking drugs are the most common causes of anaphylactic reactions in the perioperative setting
21. You are called to the bedside to evaluate new ST-segment depressions on a routine postoperative EKG of a 42-year-old woman who underwent a partial colectomy. She is asymptomatic. Her heart rate is 80 to 90 bpm, and her blood pressure is 135/60. Your next step in the management includes
A. Wait and monitor her
B. Send off one set of troponins
C. Administer metoprolol for HR control
D. Call a cardiology consult
22. Which of the following patients warrants a routine postoperative EKG?
A. An 85-year-old male with hypothyroidism who underwent a cystoscopy and ureteral stent placement
B. A 72-year-old male with coronary artery disease (CAD) and hypertension who underwent an ankle fusion
C. A 52-year-old male with hypertension, hyperlipidemia, and diabetes who underwent a radical prostatectomy
D. A 50-year-old male with rheumatoid arthritis who underwent bilateral knee replacements
23. You are called to evaluate a 68-year-old woman who underwent a right upper lobectomy for lung cancer. She is complaining of chest pain and palpitations and explains to you that she has never had this problem before. Her EKG demonstrates atrial fibrillation with a rate of 152. Her blood pressure is currently 65/40. Which of the following is the most appropriate first step in managing her?
A. Repeat EKG in 15 minutes
B. Administer 150 mg IV amiodarone
C. Administer 5 mg IV metoprolol
D. Electrical cardioversion
24. Postoperative premature ventricular contractions (PVCs) most commonly are a result of
A. QT prolongation
B. Excessive β-blocker administration
C. Increased sympathetic system stimulation
D. Residual volatile anesthetics
25. Which of the following could result in bradydysrhythmias in the postoperative period?
A. Opioid administration
B. Bowel distention
C. Increased intraocular pressure
D. All of the above
26. What percentage of patients over the age of 50 who undergo elective surgery will experience postoperative delirium within the first 5 days following their surgical procedure?
27. Which of the following intraoperative factors is predictive of postoperative delirium?
A. Blood loss
B. Anesthetic technique
C. Intraoperative hypotension
D. Intraoperative hypertension
28. Each of the following increases the risk of postoperative delirium, except
A. Advanced age
B. Preexisting cognitive impairment
C. Alcohol abuse
D. Chronic pain
29. Which of the following statements regarding emergence excitement is most correct?
A. It is most common in children aged 6 to 8 years
B. Less than 5% of children experience emergence excitement
C. It is associated with long-term cognitive sequelae
D. Preoperative midazolam administration is associated with an increased incidence
30. Oliguria is defined as urine output less than
A. 0.2 mL/kg/hr
B. 0.5 mL/kg/hr
C. 0.7 mL/kg/hr
D. 1.0 mL/kg/hr
31. Postoperative urinary retention (POUR) is the inability to void despite a bladder volume of
A. 100 to 200 mL
B. 300 to 400 mL
C. 500 to 600 mL
D. 700 to 800 mL
32. The most common cause of oliguria in the immediate postoperative period is
A. Low cardiac output
B. Acute tubular necrosis
C. Renal vascular obstruction
33. An intra-abdominal pressure higher than which of the following is required to impede renal perfusion?
A. 10 cm H2O
B. 15 cm H2O
C. 20 cm H2O
D. 30 cm H2O
34. A 42-year-old morbidly obese male undergoes a laparoscopic gastric bypass. The surgical procedure lasts 8 hours. Estimated blood loss is 200 mL, and he receives 4.5 L of crystalloid. In the postanesthesia care unit, his urine output is 5 to 10 mL/hr despite an additional 1 L of crystalloid. The most likely etiology of his oliguria is
A. Contrast-induced nephropathy
D. Surgical injury of ureters
35. All of the following are consequences of moderate hypothermia (33–35°C), except
A. Inhibition of platelet function
B. Prolongation of neuromuscular blockade
C. Inhibition of drug metabolism
D. Increases coagulation-factor activity
36. The most accurate measurement of core body temperature is obtained via
B. Tympanic membrane
37. The most effective treatment for abolishing postoperative shivering is
38. A 22-year-old nonsmoking woman with no previous anesthetic history undergoes a laparoscopic ovarian cystectomy. Her risk of postoperative nausea and vomiting (PONV) is most closely approximated by
39. A 30-year-old woman who underwent a knee arthroscopy has postoperative nausea and vomiting (PONV) in the postanesthesia care unit (PACU). Per report, she received ondansetron 4 mg IV 30 minutes prior to the conclusion of her procedure. Which of the following treatments is most appropriate for managing her PONV in the PACU?
A. Scopolamine patch
40. Which of the following is the most frequent cause of delayed awakening in the postanesthesia care unit (PACU)?
C. Residual effects of sedatives
41. Which of the following general principles regarding discharge from the postanesthesia care unit (PACU) is correct?
A. A mandatory minimum stay in the PACU is not required
B. Patients should not be discharged until they are pain-free
C. Patients need to void prior to PACU discharge
D. Patients need to demonstrate the ability to drink and retain clear fluids prior to PACU discharge
42. According to the ASA Standards for Postanesthesia Care, which of the following statements is correct?
A. A patient is to be transported to the postanesthesia care unit (PACU) by at least one physician
B. A patient must be monitored by continuous pulse oximetry during transport to the PACU
C. A patient who solely received regional anesthesia may routinely bypass the PACU
D. A patient must be discharged from the PACU by a physician
43. An otherwise-healthy adult male breathing room air receives a large dose of opioid that depresses his ventilation to the point that his alveolar PaCO2 is 80 mm Hg. What is his predicted alveolar PaO2?
A. 40 mm Hg
B. 50 mm Hg
C. 70 mm Hg
D. 90 mm Hg
44. If the patient described in the previous question is administered 2 L of oxygen by nasal cannula, then his alveolar PaO2 increases to what amount?
A. 60 mm Hg
B. 80 mm Hg
C. 100 mm Hg
D. 120 mm Hg
45. A 42-year-old woman complains of pain and inability to dorsiflex the first toe. The nerve most likely to be involved is the
46. Which of the following clinical criteria is associated with transfusion-related acute lung injury (TRALI) as compared to transfusion-associated circulatory overload (TACO)?
A. Pulmonary edema
47. Which of the following statements regarding postoperative shivering is most correct?
A. Occurs with general anesthesia but not epidural anesthesia
B. Is always associated with a decrease in body temperature
C. In normothermic patients is related to a hypothalamic depressant effects of opioids
D. In normothermic patients results from uninhibited spinal reflexes
48. A 49-year-old woman with nephrolithiasis develops tachycardia, low-grade fever, and hypotension after a ureteral stent placement. Urine output is 5 to 10 mL/hr. All of the following can be used to treat the patient, except
49. All of the following are advantages of high-flow nasal cannula delivery systems, except
A. Humidification of the gas
B. Gas delivery up to 6 L/min
C. Deliver of gas throughout the respiratory cycle
D. Ability to deliver warm gas (37°C)
50. Which of the following procedures is most likely to be associated with postoperative hypertension?
C. Gastric bypass
D. Hip arthroplasty
CHAPTER 20 ANSWERS
1. B. Critical respiratory events accounted for more than half of the PACU malpractice claims in the US closed-claims database.
2. D. The ASA has adopted Standards for Postanesthesia Care that delineate the minimum requirements for PACU monitoring and care. All of the statements are contained within the ASA Standards for Postanesthesia Care.
3. A. Airway obstruction is a common and potentially devastating complication in the postoperative period. The most frequent cause of postoperative airway obstruction is the loss of pharyngeal tone due to the residual depressant effects of inhaled and intravenous anesthetics and the persistent effects of neuromuscular-blocking drugs.
4. D. The possibility of residual neuromuscular blockade must be considered as a potential cause of upper airway obstruction in any patient who received neuromuscular-blocking drugs during anesthesia. Residual neuromuscular blockade may not be clinically evident because the diaphragm recovers from neuromuscular blockade before the pharyngeal muscles do. End-tidal carbon dioxide concentrations, oxygen saturation, and tidal volumes may indicate adequate ventilation and oxygenation, while the ability to maintain a patent upper airway and clear upper airway secretions remains compromised.
5. A. Measurement of the TOF ratio is commonly used to assess reversal of neuromuscular blockade. Significant clinical weakness may persist to a ratio of 0.7, and pharyngeal function does not return to baseline until an adductor pollicis TOF ratio is greater than 0.9.
6. B. In awake patients, clinical assessment of reversal of neuromuscular blockade is preferred to the application of painful train-of-four or tetanic stimulation. Clinical evaluation includes grip strength, tongue protrusion, the ability to lift the legs off the bed, and the ability to lift the head off the bed for a full 5 seconds. Of these maneuvers, the 5-second sustained head lift is considered the gold standard because it reflects not only generalized motor strength but, more importantly, the patient’s ability to maintain and protect the airway.
7. A. If persistence or return of neuromuscular weakness in the postanesthesia care unit is suspected, prompt review of possible etiologic factors is indicated. Metabolic states that can contribute to prolonged neuromuscular blockade include hypocalcemia, hypermagnesemia, hypothermia, respiratory acidosis, and hepatic and renal failure.
8. C. Laryngospasm refers to a sudden spasm of the vocal cords that completely occludes the laryngeal opening. Although it is most likely to occur in the operating room at the time of tracheal extubation, patients who arrive in the PACU asleep after general anesthesia are also at risk for laryngospasm. Jaw thrust with CPAP is often sufficient stimulation to “break” the laryngospasm. If jaw thrust and CPAP maneuvers fail, then administration of propofol and providing muscle relaxation with succinylcholine are effective treatments.
9. D. Airway edema is a possible complication in patients undergoing prolonged procedures in the prone position and in procedures with large amounts of blood loss, requiring aggressive fluid resuscitation. Although facial and scleral edema are important physical signs that can alert the clinician to the presence of airway edema, significant edema of pharyngeal tissue is often not accompanied by visible external signs. If tracheal extubation is to be attempted in these patients in the postanesthesia care unit, evaluation of airway patency must precede removal of the endotracheal tube (ETT). The patient’s ability to breathe around the ETT can be evaluated by a “cuff-leak” test. By deflating the ETT cuff and with occlusion of the proximal end of the ETT, the patient is asked to breathe around the tube. Good air movement suggests that the patent’s airway will remain patent after tracheal extubation. Though helpful, the cuff-leak “test” does not fully exclude the presence of airway edema.
10. A. Patients with OSA are particularly prone to airway obstruction and, therefore, deserve special consideration in the postanesthesia care unit (PACU). Patients with OSA are exquisitely sensitive to opioids, and when possible, continuous regional anesthesia techniques should be used to provide postoperative analgesia. Benzodiazepines can have a more intense effect on pharyngeal muscle tone than opioids and, therefore, can contribute to airway obstruction in the PACU. When caring for a patient with OSA, plans should be made preoperatively to provide CPAP in the immediate postoperative period. The majority of patients with mild to moderate OSA are undiagnosed at the time of surgery; therefore, care should be taken to identify at-risk patients based on preoperative clinical suspicion, a history of snoring, and daytime sleepiness.
11. B. An obstructed upper airway requires immediate attention. It may not be possible to mask-ventilate a patient with severe upper airway obstruction as a result of edema or hematoma. In the case of hematoma after carotid surgery, an attempt should be made to decompress the airway by opening the wound and evacuating the hematoma. This maneuver may not effectively decompress the airway if a significant amount of fluid or blood has infiltrated the tissue planes of the pharyngeal wall. If emergency tracheal intubation is required, it is important to have ready access to difficult airway equipment and surgical backup for performance of an emergency tracheostomy.
12. C. Alveolar hypoventilation and atelectasis are the most common causes of transient postoperative hypoxemia in the PACU. Microaspiration, pneumothorax, and pulmonary embolus are less common causes of postoperative hypoxemia.
13. C. Under normal conditions, minute ventilation increases by approximately 2 L/min for every 1-mm Hg increase in arterial PaCO2. This normal ventilatory response to carbon dioxide can be significantly depressed in the immediate postoperative period by the residual effects of drugs.
14. D. Increased venous admixture, decreased alveolar partial pressure of oxygen, ventilation-to-perfusion mismatch, and shunt are causes of arterial hypoxemia in the postoperative period. Increased venous admixture is due to mixing of desaturated venous blood with oxygenated arterial blood. Normally, only 2% to 5% of cardiac output is shunted through the lungs, and this small amount of shunted blood with a normal mixed venous saturation has a minimal effect on PaO2. In low cardiac output states, or conditions in which the shunt fraction increases (such as pulmonary edema and atelectasis), there is mixing of a greater amount of desaturated shunted blood with saturated arterialized blood, which decreases the PaO2.
15. C. Postobstructive pulmonary edema is a rare, but significant complication resulting from upper airway obstruction produced by the exaggerated negative pressure generated by inspiration against a closed glottis. This exaggerated negative intrathoracic pressure increases venous return, which further promotes the transudation of fluid. Muscular healthy patients are at increased risk because of their ability to generate significant inspiratory force. Laryngospasm is the most common cause of upper airway obstruction leading to postobstructive pulmonary edema, but pulmonary edema may result from any condition that occludes the upper airway. Arterial hypoxemia is usually manifested within 90 minutes after development of postobstructive pulmonary edema and is accompanied by bilateral fluffy infiltrates on the chest radiograph. The diagnosis depends on clinical suspicion once other causes of pulmonary edema are ruled out. Treatment is supportive and includes supplemental oxygen, diuresis, and positive-pressure ventilation.
16. B. As a general rule, each L/min of oxygen flow through nasal cannula increases FIO2 by 0.04, with 5 L/min resulting in approximately 0.41 FIO2 [0.04 × 5 = 0.2 + 0.21 (room air) = 0.41].
17. D. Hemodynamic alterations in the postoperative period can have a negative impact on outcome. Surprisingly, postoperative hypertension and tachycardia are more predictive of unplanned admission to the critical care unit and mortality rate than are hypotension and bradycardia.
18. A. Intravascular volume depletion (hypovolemia) is the most common cause of hypotension in the PACU. Common causes of decreased intravascular volume in the immediate postoperative period include ongoing third-space translocation of fluid, inadequate intraoperative fluid replacement, and loss of sympathetic nervous system tone as a result of spinal or epidural blockade. Bleeding should be ruled out as a cause of hypovolemia in patients who have undergone a surgical procedure in which significant blood loss is possible.
19. A. A high sympathetic block (T4) can result in bradycardia and hypotension secondary to blockade of the cardioaccelerator fibers. This should be treated promptly with vasopressors, such as ephedrine, as cardiac arrest secondary to bradycardia and hypotension can ensue. Epinephrine is used when there is severe bradycardia and hypotension.
20. D. Anaphylactic (or anaphylactoid) reactions may be the cause of postoperative hypotension. Anaphylaxis should be considered in cases of sudden refractory hypotension even when not accompanied by the classic signs of bronchospasm and rash. Increased serum tryptase concentrations confirm the occurrence of an allergic reaction, but this change does not differentiate anaphylactic from anaphylactoid reactions. Neuromuscular-blocking drugs are the most common cause of anaphylactic reactions in the operative setting. Epinephrine is the drug of choice to treat anaphylaxis.
21. A. Postoperative ECG changes should be interpreted in light of the patient’s cardiac history and risk index. In low-risk patients (<45 years of age, no known cardiac disease, only one risk factor), postoperative ST-segment changes on the ECG do not usually indicate myocardial ischemia. Relatively benign causes of ST-segment changes in these low-risk patients include anxiety, gastroesophageal reflux disease, hyperventilation, and hypokalemia. In general, low-risk patients require only routine postanesthesia care unit observation unless associated signs and symptoms warrant further clinical evaluation.
22. C. A routine postoperative ECG is only recommended for patients with known or suspected CAD who have undergone high- or intermediate-risk surgery. High-risk surgery includes emergency surgery, major vascular surgery, peripheral vascular surgery, and unanticipated prolonged procedures associated with large fluid shifts or blood loss. Intermediate-risk procedures include intra-abdominal and thoracic surgery, carotid endarterectomy, head and neck surgery, orthopedic surgery, and prostate surgery.
23. D. Control of the ventricular response rate is the immediate goal in the treatment of new-onset atrial fibrillation. While most patients can be treated pharmacologically, hemodynamically unstable patients require prompt electrical cardioversion.
24. C. PVCs and ventricular bigeminy are common in the postoperative period. PVCs most often reflect increased sympathetic nervous system stimulation, as many occur with hypoxemia, hypercapnia, and acidemia.
25. D. Bradycardia in the PACU is often iatrogenic. Drug-related causes include administration of α-blockers, opioids, anticholinesterase agents, and treatment with dexmedetomidine. Procedure- and patient-related causes include bowel distention, increased intracranial or intraocular pressure, and spinal anesthesia.
26. C. Approximately 10% of adult patients older than 50 years who undergo elective surgery will develop postoperative delirium within the first five postoperative days.
27. A. Intraoperative factors that are predictive of postoperative delirium include surgical blood loss, the number of intraoperative blood transfusions, and hematocrit less than 30%. Intraoperative hemodynamic derangements and the anesthetic technique do not seem to be predictors of postoperative delirium.
28. D. Many adult patients at risk for postoperative delirium can be identified preoperatively. The most significant preoperative risk factors include (1) advanced age, (2) preoperative cognitive impairment, (3) decreased functional status, (4) alcohol abuse, and (5) a previous history of delirium. Chronic pain is not a risk factor for postoperative delirium.
29. D. Emergence excitement is a transient confusional state that is associated with emergence from general anesthesia. It is common in children, with more than 30% experiencing agitation or delirium at some period during their postanesthesia care unit stay. The peak age of emergence excitement in children is between 2 and 4 years. Unlike delirium, emergence excitement typically resolves quickly and without long-term cognitive sequelae. Preoperative midazolam administration has been associated with an increase in the incidence and duration of emergence delirium in children.
30. B. Postoperative oliguria can result from prerenal, renal, and postrenal causes. Frequently, the cause is multifactorial, with a preexisting renal insufficiency that is exacerbated by an intraoperative insult. Oliguria is defined as urine output less than 0.5 mL/kg/hr.
31. C. POUR is defined as the inability to void despite a bladder volume of more than 500 to 600 mL. Risk factors include male gender, age older than 50 years, intraoperative fluid volume, duration of surgery, and bladder volume on admission. Certain types of surgery are also associated with a higher risk of POUR, including anorectal and joint replacement surgery. Commonly used perioperative medications such as anticholinergics, β-blockers, and narcotics can also contribute to POUR. Diagnosis can be made by clinical examination, bladder catheterization, or ultrasound assessment. Bladder volumes measured by ultrasound imaging correlate well with volumes obtained by urinary catheterization.
32. D. The most common cause of oliguria in the immediate postoperative period is hypovolemia. A fluid challenge is usually effective in restoring urine output. Volume resuscitation to maximize renal perfusion is particularly important in order to prevent the development of acute kidney injury. If an intravascular fluid challenge is contraindicated or oliguria persists, assessment of intravascular volume or cardiac function is indicated to differentiate hypovolemia from low cardiac output states.
33. D. An intra-abdominal pressure higher than 30 cm H2O can impede renal perfusion, leading to renal ischemia and postoperative renal dysfunction. Bladder pressure should be measured in patients in whom intra-abdominal hypertension is suspected so that abdominal decompression can be performed to relieve intra-abdominal pressure and restore renal perfusion.
34. B. Rhabdomyolysis is a recognized cause of postoperative renal insufficiency in morbidly obese patients, particularly those who have undergone gastric bypass procedures. Risk factors include the body mass index and duration of surgery. Volume loading, diuretics, and alkalinization of urine to flush the renal tubules can prevent ongoing renal tubular damage and subsequent acute renal failure.
35. D. Mild to moderate hypothermia (33–35°C) is a recognized cause of a number of postoperative complications, including inhibition of platelet function, reduced coagulation-factor activity, and decreased drug metabolism. In addition, it exacerbates postoperative bleeding, prolongs neuromuscular blockade, and may delay awakening.
36. B. Core body temperature can most accurately be measured at the tympanic membrane. Axillary, rectal, and nasopharyngeal temperature measurements are less accurate and may underestimate core temperature.
37. C. A number of opioids and clonidine are effective in stopping shivering once it starts, but meperidine is the most effective treatment. Doxapram, a central nervous system stimulant, is somewhat effective in abolishing postoperative shivering.
38. D. A simple risk score consisting of four factors can be used to identify high-risk patients for PONV. The four risk factors are (1) female gender, (2) history of motion sickness or PONV, (3) nonsmoking, and (4) the use of postoperative opioids. The incidence of PONV correlates with the number of these factors present: zero, one, two, three, or four factors correspond to an incidence of 10%, 21%, 39%, 61%, and 79%, respectively. The patient in the vignette has two risk factors (female, nonsmoker), so her approximate risk of PONV is 40%.
39. D. When choosing a rescue antiemetic for patients with PONV, both the class of drug and the timing of administration are factors. If an adequate dose of antiemetic given at the appropriate time proves ineffective, simply giving more of the same class of drug in the PACU is unlikely to be of significant benefit. If no prophylactic drug was given, the recommended treatment is a low-dose 5-HT3 antagonist, ondansetron. Of the choices provided in the vignette, promethazine is likely to be the most effective rescue antiemetic. Since the patient received ondansetron for prophylaxis, additional ondansetron is unlikely to be effective. A scopolamine patch is unlikely to take effect rapidly enough to be beneficial. Dexamethasone, while effective for prophylaxis, is less beneficial for rescue.
40. C. Even after prolonged surgery and anesthesia, a response to stimulation in 60 to 90 minutes should be expected. The etiology of delayed awakening after anesthesia can be divided into the general categories of pharmacologic, metabolic, and neurologic causes. Of these, residual sedation from drugs used during anesthesia is the most frequent cause of delayed awakening in the PACU.
41. A. Specific PACU discharge criteria may vary, but certain general principles are universally applicable. These principles include mandatory minimum stay in the PACU is not required, patients must be observed until they are no longer at risk for respiratory depression, and their mental status is clear or has returned to baseline; hemodynamic criteria are based on the patient’s baseline hemodynamics without specific systemic blood pressure and heart rate requirements. To facilitate PACU discharge, discharge scoring systems have been developed and modified over time to reflect current anesthesia practice.
42. D. The Standards for Postanesthesia Care are intended to ensure the quality of postanesthetic patient care. They include the following:
• Standard I: “All patients who have received general anesthesia, regional anesthesia, or monitored anesthesia care shall receive appropriate post anesthesia management”
• Standard II: “A patient transported to the PACU shall be accompanied by a member of the anesthesia care team who is knowledgeable about the patient’s condition. The patient shall be continually evaluated and treated during transport with monitoring and support appropriate to the patient’s condition”
• Standard III: “Upon arrival to the PACU, the patient shall be reevaluated and a verbal report provided to the responsible PACU nurse by the member of the anesthesia care team who accompanies the patient”
• Standard IV: “The patient’s condition shall be evaluated continually in the PACU”
• Standard V: “A physician is responsible for the discharge of the patient from the PACU”
43. B. At sea level, a normocapnic patient breathing room air will have an alveolar oxygen pressure of 100 mm Hg. Review of the alveolar gas equation demonstrates that hypoventilation alone is sufficient to cause arterial hypoxemia in a patient breathing room air. In this case, a rise in PaCO2 from 40 to 80 mm Hg (alveolar hypoventilation) results in an alveolar oxygen pressure (PaO2) of 50 mm Hg.
= FIO2 × (Patm − PH2O) − PaCO2/R)
= 0.21 × (760 − 47) − 80/0.8
= 50 mm Hg
(Patm = atmospheric pressure mm Hg, PH2O = water vapor pressure mm Hg, R = respiratory quotient—8 CO2 molecules produced for every oxygen molecule consumed)
44. C. In the setting of isolated hypoventilation, modest increases in inspired oxygen are remarkably effective at restoring alveolar oxygenation. For this patient, if 2 L of supplemental oxygen is administered by nasal cannula, then the FIO2 increases to approximately 28% and the calculated alveolar PaO2 is 100 mm Hg.
= FIO2 × (Patm − PH2O) − PaCO2/R)
= 0.28 × (760 − 47) − 80/0.8
= 100 mm Hg
45. D. An assessment and written documentation of the patient’s peripheral nerve function on discharge from the postanesthesia care unit may become useful information should a new peripheral neuropathy develop in the later postoperative period. The peroneal nerve provides the motor innervation for dorsiflexion of the first toe, while the tibial nerve allows plantar flexion of the first toe.
46. C. TRALI can occur up to 6 hours after transfusion of blood, coagulation factor, or platelet transfusions. Therefore, it should be included in the differential diagnosis of pulmonary edema in the postanesthesia care unit, among patients who received intraoperative transfusions. The resulting noncardiogenic pulmonary edema is often associated with fever, systemic hypotension, and the presence of exudative pulmonary fluid. If a complete blood count is obtained with the onset of symptoms, an acute decrease in the white blood cell count (leukopenia) reflecting the sequestration of granulocytes is seen within the lung. Initially, it may be difficult distinguishing TRALI from TACO caused by volume overload resulting from the blood products transfused. In either case, treatment is supportive and includes supplemental oxygen, dieresis, and mechanical ventilation, if needed.
47. D. Postoperative shivering commonly occurs after both general and neuraxial anesthesia and is usually, but not always, associated with a decrease in the patient’s body temperature. Although thermoregulatory mechanisms can explain shivering in a hypothermic patient, a separate mechanism has been proposed to explain shivering in normothermic patients. The mechanism of normothermic shivering is thought to be a result from uninhibited spinal reflexes, which are manifested as clonic activity.
48. C. Urinary tract manipulation can result in sepsis in the postanesthesia care unit. In these cases, hypotension is often accompanied by fever and rigor. If sepsis is suspected, fluid resuscitation and vasopressor support should be initiated, blood should be obtained for culture, and antibiotic therapy should be administered. The patient’s low urine output should be improved with hemodynamic support. Diuretics are not indicated for a hypovolemic patient with sepsis.
49. B. Delivery of oxygen by traditional nasal cannula is limited to 6 L/min flow to minimize discomfort and complications that result from inadequate humidification. Alternatively, oxygen can be delivered up to 40 L/min by high-flow nasal cannula systems, which humidify and warm the gas to 99.9% relative humidity and 37°C. Unlike non-rebreather masks, these devices deliver oxygen directly to the nasopharynx throughout the respiratory cycle.
50. A. A number of patient, procedural, and postoperative factors can contribute to the development of postoperative hypertension. Patients with a history of essential hypertension are at greatest risk for significant systemic hypertension in the postanesthesia care unit. Advanced age, history of cigarette smoking, and preexisting renal disease are other patient-related risk factors for postoperative hypertension. Surgical procedures that predispose the patient to postoperative hypertension include craniotomy and carotid endarterectomy. Other common postoperative causes of hypertension include pain, hypoxemia, hypoventilation and associated hypercapnia, emergence excitement, shivering, bladder distension, drug withdrawal, and hypervolemia.