Malignant hyperthermia (MH) develops intraoperatively. The earliest clinical sign is usually:

• A Hyperthermia (temperature >38.5°C)
• B Muscle rigidity
• C Unexplained rise in end-tidal CO2 (hypercarbia) with tachycardia ✓
• D Hyperkalaemia on ABG

Explanation

The earliest sign of malignant hyperthermia is an unexplained rise in ETCO2 (hypercarbia) reflecting hypermetabolism of skeletal muscle, accompanied by tachycardia and mixed respiratory and metabolic acidosis. Temperature elevation, the hallmark sign, is actually a late finding. The triggering agents are volatile inhalational anaesthetics and succinylcholine. Immediate management: call for help, remove triggers (switch to TIVA, change circuit and CO2 absorber, increase FGF), administer dantrolene 2.5 mg/kg IV (repeat as needed up to 10 mg/kg), and treat hyperkalaemia, acidosis, and arrhythmias. Dantrolene inhibits RyR1-mediated calcium release from sarcoplasmic reticulum.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.