Critical Events
Malignant hyperthermia, local anesthetic systemic toxicity, anaphylaxis, venous air embolism, severe hyperkalemia, can't-intubate / can't-ventilate. ← Back to Q-Bank
Q1. Earliest sign of malignant hyperthermia
During emergence from a sevoflurane anesthetic in a 22-year-old, the EtCO₂ rises from 38 to 62 mmHg over 10 minutes despite increased minute ventilation. Masseter rigidity is noted. The most reliable earliest clinical sign of malignant hyperthermia is:
A. Temperature >38.5°C
B. Hyperkalemia on ABG
C. Unexplained rise in end-tidal CO₂
D. Sinus tachycardia
E. Masseter rigidity
Show answer
Answer: C. Unexplained rising ETCO₂ (or spontaneous tachypnea / breathing over the ventilator in a SV patient) is the most reliable earliest sign. Tachycardia and masseter rigidity occur but are less specific; temperature elevation and hyperkalemia are late findings. Treatment: dantrolene 2.5 mg/kg IV q5–10 min up to 10 mg/kg, then 1 mg/kg q4–6h × 24–48h.
Q2. Local anesthetic systemic toxicity management
A patient receives 0.5% bupivacaine for an interscalene block and develops seizures followed by ventricular dysrhythmia and cardiac arrest. After securing the airway, the most appropriate next step is:
A. Amiodarone 300 mg IV
B. Lidocaine 1.5 mg/kg IV bolus
C. 20% lipid emulsion: 1.5 mL/kg bolus, then 0.25 mL/kg/min infusion
D. Vasopressin 40 units IV
E. Calcium chloride 1 g IV
Show answer
Answer: C. LAST protocol: 1.5 mL/kg lipid emulsion bolus (~100 mL over 2–3 min in adult), then 0.25 mL/kg/min infusion; can re-bolus and double the infusion if persistent instability; max 12 mL/kg. Avoid vasopressin, calcium channel blockers, β-blockers, and local anesthetics (including lidocaine) during LAST resuscitation. Epinephrine doses should be reduced (≤1 mcg/kg).
Q3. Venous air embolism detection sensitivity
During posterior fossa surgery in the sitting position, end-tidal CO₂ abruptly drops from 36 to 22 mmHg with concurrent hypotension. The single most sensitive monitor for the suspected complication is:
A. Precordial Doppler
B. End-tidal CO₂
C. Transesophageal echocardiography
D. Esophageal stethoscope (mill-wheel murmur)
E. Pulmonary artery pressure monitoring
Show answer
Answer: C. Venous air embolism detection sensitivity (most → least): TEE > precordial Doppler > PAP > EtCO₂ > RAP > EKG > esophageal stethoscope. Management: stop air entrainment (compress jugulars, flood field), 100% FiO₂, Durant's maneuver (left lateral decubitus, head down), aspirate via central line if accessible.
Q4. Anaphylaxis intraoperative
Five minutes after induction with rocuronium, a patient develops urticaria, profound hypotension, bronchospasm, and SpO₂ falls to 78%. The most appropriate epinephrine dose is:
A. 1 mg IV push
B. 1 mcg/kg IV bolus (~50–100 mcg in adult), repeat as needed
C. 0.3 mg IM only
D. 10 mcg via endotracheal tube
E. Wait for blood pressure response to fluids first
Show answer
Answer: B. Intraop anaphylaxis: epinephrine 1 mcg/kg IV (50–100 mcg) titrated to response, up to code dose 10 mcg/kg. Concurrently: 100% O₂, IV fluids (25 mL/kg up to 50 mL/kg), stop offending agent, get help. Mast cell tryptase ↑ at 1–2 hr confirms. Most common triggers: NMBDs (sux > roc), latex, antibiotics, chlorhexidine, blood products.
Q5. Anaphylaxis triggers in anesthesia
The most common cause of perioperative anaphylaxis is:
A. Volatile anesthetic
B. Neuromuscular blocking drug
C. Local anesthetic
D. Opioid
E. Propofol
Show answer
Answer: B. NMBDs are the most common (especially succinylcholine and rocuronium), then latex, then antibiotics. Cross-reactivity between aminosteroid NMBDs and over-the-counter products containing quaternary ammonium (cosmetics, toothpaste) — patients may have antibodies without prior exposure.
Q6. Hyperkalemic cardiac arrest
A patient with ESRD on hemodialysis arrives in PEA with K⁺ 7.8 on i-STAT. ACLS is in progress. The most appropriate priority among the following is:
A. Sodium bicarbonate 1 mEq/kg
B. Calcium chloride 1 g IV
C. Albuterol 10–20 mg nebulized
D. Regular insulin 10 U IV + D50
E. Emergent hemodialysis
Show answer
Answer: B. Calcium first — stabilizes cardiac membrane within minutes. Then bicarbonate + insulin/glucose + β₂-agonist to shift K⁺ intracellularly. Then dialysis or kayexalate for total body K⁺ removal. Calcium does NOT lower K⁺ but buys time.
Q7. Can't-intubate / can't-ventilate
In a failed mask ventilation and failed intubation scenario, after a single attempt with a supraglottic airway fails, the next definitive step is:
A. Additional intubation attempts
B. Emergent cricothyrotomy
C. Awake fiberoptic
D. Increase volatile concentration
E. Lateral positioning
Show answer
Answer: B. Per ASA Difficult Airway Algorithm: failed mask + failed intubation + failed SGA → emergency invasive airway. Cricothyrotomy (scalpel-bougie-tube) is gold standard. Limit total time; SpO₂ <80% = transition to surgical airway. Don't keep attempting laryngoscopy in a saturating patient.
Q8. Laryngospasm management
A 5-year-old develops laryngospasm during inhalation induction. After applying CPAP at 20 cm H₂O with 100% O₂ and a jaw thrust, the next step is:
A. 1 mg/kg propofol to deepen anesthesia
B. Succinylcholine 4 mg/kg IM
C. Atropine 0.02 mg/kg IV
D. Lidocaine 1 mg/kg IV
E. Wait
Show answer
Answer: A. Laryngospasm ladder: jaw thrust + CPAP + 100% O₂ → propofol 1 mg/kg to deepen → succinylcholine 0.25–2 mg/kg IV (or 4–5 mg/kg IM) if persistent. Pretreat children with atropine 0.01–0.02 mg/kg before sux to prevent bradycardia.
Q9. Acute hemolytic transfusion reaction
A patient receiving pRBCs develops fever, flank pain, hemoglobinuria, and hypotension within 30 minutes of transfusion start. The most likely mechanism is:
A. Cytokine release from leukocytes in storage
B. ABO incompatibility → IgM-mediated intravascular hemolysis
C. Donor anti-leukocyte antibodies
D. IgE-mediated mast cell degranulation
E. Bacterial contamination
Show answer
Answer: B. Acute hemolytic transfusion reaction = ABO mismatch → IgM-mediated complement activation → intravascular hemolysis. Treatment: stop transfusion, support hemodynamics, generous IV fluids/diuretic to maintain UOP, treat hyperkalemia, watch for DIC. Send blood back with fresh sample for retypecross and direct Coombs.
Q10. TRALI vs TACO
A patient develops respiratory distress and bilateral pulmonary infiltrates within 4 hours of FFP transfusion. CVP is normal, BNP is normal. The diagnosis is:
A. Transfusion-associated circulatory overload (TACO)
B. Transfusion-related acute lung injury (TRALI)
C. Anaphylactic reaction
D. Bacterial contamination
E. Acute hemolytic reaction
Show answer
Answer: B. TRALI: non-cardiogenic pulmonary edema within 6 hr of transfusion; donor anti-leukocyte antibodies (most often from multiparous female donors). Treat with lung-protective ventilation, supportive care, low TV. TACO has high BNP/CVP (volume overload) and responds to diuresis.
Q11. Massive hemorrhage venous air
The fatal volume of air that produces an "air lock" in the right ventricle is approximately:
A. 10 mL bolus of air
B. 100 mL bolus of air
C. 300–500 mL (~3–5 mL/kg) bolus of air, or 10–15 mL/kg of CO₂
D. 1000 mL of air slowly
E. Any volume above 5 mL
Show answer
Answer: C. Cardiovascular collapse with 3–5 mL/kg bolus of air or 10–15 mL/kg of CO₂. Sources: open neck veins (sitting craniotomy), large open wounds above heart level, central line placement, laparoscopy CO₂.
Q12. Pediatric bradycardia
A 4-month-old infant under sevoflurane anesthesia develops HR 75. First action:
A. IV atropine 20 mcg/kg
B. Confirm and treat hypoxia (the most common cause)
C. Chest compressions
D. Epinephrine 1 mcg/kg
E. Pacing pads
Show answer
Answer: B. Pediatric bradycardia is hypoxia until proven otherwise. Check airway, ventilation, FiO₂, ETT position. If HR <100 despite stimulation in a newborn → PPV with O₂. If HR <60 despite 30 sec of effective PPV → chest compressions. Atropine and epinephrine are later in the algorithm.
Q13. Negative pressure pulmonary edema
A 28-year-old wrestler develops pink frothy sputum and bilateral infiltrates immediately after extubation that was preceded by 30 seconds of laryngospasm. The mechanism is:
A. Direct alveolar barotrauma
B. Generation of large negative intrathoracic pressure against a closed glottis → increased venous return + decreased LV afterload → pulmonary edema
C. Aspiration
D. Anaphylaxis to neuromuscular blocker
E. Cardiogenic pulmonary edema
Show answer
Answer: B. Type I negative pressure pulmonary edema follows obstructed inspiration (laryngospasm, tube biting). Young, muscular males at highest risk (generate biggest negative pressure). Treat with O₂, PEEP/CPAP, often resolves in 24–48 hr. Type II follows relief of chronic upper airway obstruction.
Q14. Tension pneumothorax
In a mechanically ventilated patient, sudden hypotension, tracheal deviation, decreased breath sounds, and rising peak airway pressures suggest tension pneumothorax. The most appropriate immediate intervention is:
A. CT scan
B. Needle thoracostomy at the 2nd intercostal space, midclavicular line (or 4th–5th ICS, anterior axillary line)
C. Bronchoscopy
D. Increased PEEP
E. Albuterol nebulizer
Show answer
Answer: B. Clinical diagnosis — don't wait for imaging. Immediate needle decompression followed by chest tube. CXR confirmation, but treat clinically.
Q15. Serotonin syndrome perioperative
A patient on fluoxetine, tramadol, and ondansetron develops hyperthermia, clonus, agitation, and rigidity post-anesthesia. The most likely diagnosis is:
A. Malignant hyperthermia
B. Neuroleptic malignant syndrome
C. Serotonin syndrome
D. Thyroid storm
E. Anticholinergic toxicity
Show answer
Answer: C. Serotonin syndrome: clonus (lower > upper), hyperreflexia, mydriasis, agitation, hyperthermia. Triad of agents: SSRI + serotonergic drug (tramadol, meperidine, methadone, ondansetron, MAOIs, methylene blue, linezolid). Treat: stop agents, supportive care, cyproheptadine (5HT₂ antagonist), benzodiazepines, dantrolene for severe hyperthermia.
Q16. Methylene blue + SSRI
A patient on sertraline is given methylene blue for vasoplegic shock. Why is this combination concerning?
A. Methylene blue inhibits SSRI metabolism
B. Methylene blue is a potent reversible MAOI → risk of serotonin syndrome
C. SSRIs prevent vasopressor response
D. Methylene blue inhibits guanylate cyclase
E. Both combine to cause methemoglobinemia
Show answer
Answer: B. Methylene blue is a reversible MAOI at doses >5 mg/kg → serotonin syndrome with concurrent serotonergic agents. Use indigo carmine instead if just identifying ureters. Methylene blue still useful for vasoplegic shock and methemoglobinemia.
Q17. Neuroleptic malignant syndrome
NMS classically presents with:
A. Hyperthermia, "lead-pipe" rigidity, autonomic instability, altered mental status, elevated CK in a patient on dopamine antagonists
B. Clonus and hyperreflexia
C. Sudden flaccid paralysis
D. Polyuria and hyperglycemia
E. Bradycardia with anticholinergic signs
Show answer
Answer: A. NMS: D2 antagonism (antipsychotics: haloperidol, metoclopramide, prochlorperazine) → muscle rigidity + autonomic dysregulation. Slower onset than serotonin syndrome. Treat: stop offending drug, supportive care, bromocriptine (D2 agonist), dantrolene.
Q18. Carcinoid crisis
During induction for tumor debulking in a patient with metastatic carcinoid, severe hypotension, bronchospasm, and flushing develop. The most appropriate immediate management is:
A. Epinephrine 1 mg IV
B. Octreotide 100 mcg IV bolus
C. Phenylephrine infusion
D. Diphenhydramine and steroids
E. β-blocker
Show answer
Answer: B. Carcinoid crisis: tumor release of serotonin, histamine, kallikrein. β-agonists (epinephrine, ephedrine) can paradoxically worsen via kallikrein release → bradykinin → vasodilation. Octreotide is first-line. Pretreat all known carcinoid patients with octreotide preoperatively (100 mcg subq TID for several days + 100 mcg infusion).
Q19. Hyperkalemia ECG progression
The earliest ECG sign of hyperkalemia is:
A. Sine wave
B. Peaked T waves
C. Wide QRS
D. Loss of P waves
E. PR prolongation
Show answer
Answer: B. Hyperkalemia ECG progression: peaked T waves → PR prolongation/short QT → P wave flattening → QRS widening → sine wave → asystole/VF. Treatment by severity: peaked T or K >6.5: shift; ECG changes or K >7: stabilize membrane with calcium, shift, remove.
Q20. Aspiration risk factors
Risk factors for clinically significant aspiration pneumonitis (Mendelson syndrome) include:
A. Gastric volume >0.4 mL/kg, pH <2.5, presence of particulates
B. Any aspiration of saliva
C. Gastric volume >0.1 mL/kg regardless of pH
D. pH >5 with large volume
E. Only solid food aspiration
Show answer
Answer: A. Mendelson criteria: aspirate >0.4 mL/kg + pH <2.5 + particulates. Modern recommendation: clear liquids 2 hr, breast milk 4 hr, formula/light meal 6 hr, fatty meal 8 hr before elective surgery.