A 10-year old child is undergoing squint surgery. He suddenly developed increased heart rate, arrhythmia, high fever, metabolic and respiratory acidosis on arterial blood gases and elevation of end tidal CO2. Which of the following would be the first agent of choice in the management of this condition?
Ans. a. Dantrolene (Ref: Miller's 7/e p1180-1189; Lee 13/e p352-354: Morgan 4/945-950)Sudden development of increased heart rate, arrhythmia, high fever, metabolic and respiratory acidosis on arterial blood gases and elevation of end tidal CO2 in a child undergoing squint surgery is highly suggestive of malignant hyperthermia. Dantrolene would be the first agent of choice in the management of malignant hyperthermia.''Malignant Hyperthermia: Dantrolene is the only drug effective in reversing the symptoms and preventing the episode."Suxamethonium is the drug most commonly responsible for causing malignant hyperthermia.'Drugs causing malignant hyperthermia are- succinylcholine (most common cause), halothane (MC inhalational agent), iso/des/sevo/methoxy- fluranes, lignocaine, TCA, MAO inhibitors and phenothiazines.''Thiopentone and pancuronium are protective drugs for malignant hyperthermia, as these raise the triggering threshold.''In malignant hyperthermia susceptible patients, safe anesthetics are N2O, Non-depolarizing muscle relaxants (atracurium), opiates, tranquilizers, etomidate, barbiturates (thiopentone) and propofol.'Malignant Hyperthermia* Autosomal dominant genetic disorder of skeletal muscle* Occurs in susceptible individuals due to exposure to some triggering agents, typically Suxamethonium or volatile agents, which cause an abnormal increase in intracellular calcium.* It is caused by dysregulation of excitation-contraction coupling in skeletal muscle.Triggering Agents:* Succinylcholine (most common cause)* Halothane (MC inhalational agent)* Halogenated Anesthesia:- Fluranes: Isoflurane, desflurane, sevoflurane. methoxy-flurane- Ether- Cyclopropane* Lignocaine* TCA* MAO inhibitors* PhenothiazinesClinical Features:* Rise in end tidal CO2 (1st sign)* Masseter muscle rigidity (MMR) and tachycardia are earliest sign* Hypermetabolic features, metabolic acidosis, fever, hyperthermia* Sympathetic over activity: Tachycardia, arrhythmia, unstable BP. initial hypertension* Muscle damage: Masseter muscle spasm, generalized rigidity, hyperkalemiaTretment:* Triggering agent must be stopped and hyperventilate with 100% oxygen* The mainstay of therapy is immediate administration of IV dantrolene.* Dantrolene is the only drug effective in reversing the symptoms and preventing the episode.
Dantrolene
Paracetamol
Procainamide
Sodium bicarbonate
Complications Of Anaesthesia