Ans. is 'c' i.e., Increased intracellular Ca o The mechanism involves a sudden rise in intracellular calcium due to release of stored calcium in sarcoplasmic reticulum, stimulating contraction, rhabdomyolysis and a hypermetabolic state.o Tachycardia and not bradycardia, is a feature of malignant hyperthermia.MALIGN ANT HYPERTHERMIAo Malignant hyperthermia is a life-threatening medical emergency which is genetically determined. The condition occurs during or immediately after anaesthesia and may be precipitated by potent inhalational agents,o The mechanism involves a sudden rise in intracellular calcium due to release of stored calcium in sarcoplasmic reticulum stimulating contraction, rhabdomyolysis and a hypermetabolic state.Drugs causing malignant hyperthermia# Succinylcholine# Desflurane# Tricyclic antidepressants# Halothane# Cyclopropane# Phenothiazines# Isoflurane# Ether# Lignocaine# Enflurane# Methoxyflurane # Sevoflurane# MAO inhibitors o Succinylcholine is the most common cause of MHoAmongst inhalational agents halothane is the most common cause.o Combination of Sch and Halothane has a much higher incidence.Clinical featureso Masseter spasm - if a patient develops severe masseter spasm after suxamethonium, there is a significant possibility of malignant hyperthermia.o Tachycardia, arrhythmias and hypertension.o Hyperthermiao Rise in end-tidal CO2 - May rise to more than 100 mm Hg (normal is 32-42 mm Hg). It is the earliest and most sensitive indicator.o Hyperkalemia, metabolic acidosis, elevated creatininephosphokinase, muscle rigidity,o Increased myoglobin, renal failure.o Muscle biopsy contracture test (definitive diagnostic procedure) :- The muscle biopsy contracture test is the most sensitive and specific test. The Caffeine Halothane Contracture test (CHCT), a test performed on freshly biopsied muscle; is the "gold standard" for diagnosis of malignant hyperthermia. However, the test is available only at few centers in the world (only about 30 centers world wide) and it is very costly. The CHCT test should be considered for all those judged to be at significant risk for malignant hyperthermia, either through family history, or by elicitation of signs of an episode of malignant hyperthermia, or if there had been any previous uncharacterized adverse reaction to a general anesthetic.Managemento Stop all anaesthetics immediately,o Hyperventilation with 100% oxygeno Cooling of body by ice coolingo Correct acidosis and hyperkalemia,o Maintain urine output,o IV dantrolene is the drug of choiceo Procaine is the local anaesthetic of choice for malignant hyperthermia patients,o Propofol is the intravenous anaesthetic of choice for malignant hyperthermia patient