SOE sample stem with a worked answer: an intraoperative crisis

This stem was written for practice. It is not an ABA question and is not taken from any book or question bank. Treatment steps follow the Malignant Hyperthermia Association of the United States (MHAUS) emergency guidance; your institution's protocols and your own judgment govern real patients.

"The most common cause in this setting is CO2 absorption from insufflation, including subcutaneous emphysema. But a rising end-tidal CO2 that does not respond to increased ventilation, with tachycardia, rising temperature and a hot absorbent canister, is malignant hyperthermia until proven otherwise. Rebreathing is unlikely because inspired CO2 is zero. I would also consider sepsis from a perforated appendix, light anesthesia, and, less likely, thyroid storm."

"Quickly examine for crepitus and ask the surgeon to lower or stop insufflation. CO2 absorption should plateau and respond to ventilation; MH keeps climbing. I would send an arterial blood gas looking for a mixed respiratory and metabolic acidosis, and potassium. But I would not wait for the gas if the picture keeps progressing."

"I treat it as MH. I call for help and the MH cart, tell the surgeon to stop and finish as quickly as possible, and turn off the sevoflurane. I hyperventilate with 100% oxygen at fresh gas flows of 10 liters per minute and put activated charcoal filters on both limbs of the circuit. I give dantrolene 2.5 mg/kg IV immediately, about 175 mg for her, and repeat it until the CO2, heart rate and rigidity improve. I switch to intravenous anesthesia, send blood gases, potassium and CK, place an arterial line and a urinary catheter, and call the MHAUS hotline for support."

"It depends on the formulation in our cart. Dantrium or Revonto come as 20 mg vials, each mixed with 60 mL of sterile water, so I need nine vials and extra hands to mix them. Ryanodex is a 250 mg vial reconstituted with 5 mL, so one vial covers the first dose. Either way I assign one person to do nothing but mix."

"I keep dosing; MHAUS notes that some patients need more than 10 mg/kg. But if large doses are not working, MHAUS advises considering alternative diagnoses, so I would think again about sepsis from the appendix and thyroid storm."

"Treat it immediately. Calcium chloride 10 mg/kg, about 700 mg, to stabilize the myocardium. Then shift potassium into cells with 10 units of regular insulin and 50 mL of 50% dextrose, check glucose hourly, and give sodium bicarbonate for the acidosis. Dantrolene treats the cause, so I keep giving it. If she develops an arrhythmia, I use standard drugs but avoid calcium channel blockers with dantrolene."

"Active cooling: cold intravenous saline, ice packs to the groin and axillae, a cooling blanket, and cold irrigation of any open body cavity. I stop cooling once she is below 38 °C to avoid overshooting into hypothermia."

"Yes, if it can be finished quickly. Leaving an inflamed appendix risks sepsis, which would cloud the picture. I keep her under a non-triggering intravenous anesthetic, and we close as fast as is safe."

"She goes to the ICU for at least 24 hours, because MH can recur. I would continue dantrolene according to MHAUS guidance, follow temperature, CO2, potassium, CK, urine myoglobin and coagulation, and keep urine output above 1 mL/kg/h, alkalinizing the urine if CK or potassium climbs. Before discharge she and her family need to know what happened, that relatives may be susceptible, and that she should be referred to an MH testing center. I would report the event to the North American MH Registry and document it clearly."

"Treat her as susceptible until tested. A non-triggering technique: no volatile agents and no succinylcholine, an anesthesia machine prepared according to the manufacturer's instructions or with charcoal filters, dantrolene immediately available, and standard monitoring with temperature. I would not give prophylactic dantrolene."