BCA Anesthesia Complications & Management 3 — Questions and Answers
Question 1: A 45-year-old patient develops seizures and cardiovascular collapse after an axillary nerve block. Which local anesthetic has the narrowest margin between CNS toxicity and cardiovascular toxicity?
- Lidocaine
- Bupivacaine (Correct answer)
- Chloroprocaine
- Ropivacaine
Correct answer: Bupivacaine
Bupivacaine has the narrowest therapeutic index because its high lipid solubility and protein binding cause rapid cardiac sodium channel blockade that is difficult to reverse, making cardiac toxicity appear at doses close to CNS toxicity doses.
Question 2: During laryngoscopy, the patient develops sudden bradycardia to 32 bpm. What is the most likely mechanism?
- Vagal stimulation from laryngeal instrumentation (Correct answer)
- Hypoxia-induced sinus node suppression
- High spinal blockade of cardiac accelerators
- Beta-blocker toxicity
Correct answer: Vagal stimulation from laryngeal instrumentation
Laryngoscopy can trigger a vagally mediated reflex bradycardia through stimulation of the superior laryngeal nerve, which is particularly pronounced in pediatric patients or lightly anesthetized adults.
Question 3: A patient undergoing laparoscopic surgery develops sudden hemodynamic instability with a 'mill-wheel' murmur. What has occurred?
- Tension pneumothorax from trocar injury
- Venous air embolism from CO2 insufflation (Correct answer)
- Acute hemorrhage from vessel injury
- Cardiac tamponade
Correct answer: Venous air embolism from CO2 insufflation
A mill-wheel murmur is pathognomonic for venous air (or gas) embolism, where gas enters the right heart and creates a churning sound as the gas-blood mixture circulates.
Question 4: Which intervention is CONTRAINDICATED in the management of local anesthetic systemic toxicity (LAST)?
- 20% lipid emulsion 1.5 mL/kg IV bolus
- Benzodiazepines for seizure control
- Propofol as the preferred agent for cardiac arrest (Correct answer)
- Cardiopulmonary resuscitation
Correct answer: Propofol as the preferred agent for cardiac arrest
Propofol is contraindicated in LAST because it contains lipid but also has direct myocardial depressant effects and should not substitute for 20% lipid emulsion; it can worsen cardiac depression.
Question 5: A patient emerges from general anesthesia with oxygen saturation of 88% and increased work of breathing. Auscultation reveals diffuse wheezing. The most likely diagnosis is:
- Pulmonary edema
- Laryngospasm
- Bronchospasm (Correct answer)
- Pneumothorax
Correct answer: Bronchospasm
Diffuse expiratory wheezing with hypoxemia after extubation indicates bronchospasm, often triggered by airway secretions, blood, or the extubation stimulus in susceptible patients.
Question 6: Which factor most significantly increases the risk of postoperative nausea and vomiting (PONV)?
- Male sex
- Non-smoker status
- Age over 65
- Intravenous opioid use (Correct answer)
Correct answer: Intravenous opioid use
Opioid use is a significant independent risk factor for PONV by stimulating the chemoreceptor trigger zone and delaying gastric emptying; other major factors include female sex, non-smoker status, and history of PONV.
Question 7: During one-lung ventilation, a patient develops severe hypoxemia. After confirming correct tube positioning, what is the most effective intervention?
- Increase FiO2 to 1.0
- Apply CPAP 5 cmH2O to the non-ventilated lung (Correct answer)
- Increase PEEP to 15 cmH2O on the ventilated lung
- Switch to two-lung ventilation
Correct answer: Apply CPAP 5 cmH2O to the non-ventilated lung
Applying CPAP (5–10 cmH2O) to the non-ventilated (operative) lung recruits collapsed alveoli and reduces intrapulmonary shunt, effectively improving oxygenation without requiring two-lung ventilation.
BCA Anesthesia Complications & Management 3
A 45-year-old patient develops seizures and cardiovascular collapse after an axillary nerve block.
Which local anesthetic has the narrowest margin between CNS toxicity and cardiovascular toxicity?