HYPERRIGIDITY AND HYPERTHERMIA ASSOCIATED WITH ANESTHESIA

Malignant Hyperthermia

Malignant hyperthermia (MH) is a rare, genetically inherited hypermetabolic syndrome that remains dormant until triggered by exposure to certain conditions (emotional and physical stresses) or pharmacological agents (anesthetic gases and succinylcholine) in susceptible individuals. It is believed that MH is caused by a derangement in the control of intracellular calcium ions, which results in a hypermetabolic state from sustained muscle contractures. Without supportive measures and immediate treatment with the antidote, dantrolene, the mortality rate from MH can be as high as 70%. A complete personal and family medical history before surgery can show important clues that might alter the anesthetic regimen preoperatively and postoperatively (eg, the use of nontriggering agents) in MH-susceptible patients. Anesthesia personnel need to recognize the early signs of a MH crisis (eg, tachycardia, muscle stiffness, hypercapnia, and tachypnea), then monitor for other signs (eg, arrhythmias, blood pressure changes, fever, metabolic and respiratory acidosis, and mottling cyanosis), and initiate prompt treatment. Because immediate recognition and treatment of this potentially fatal hyperpyrexic episode increase a patient's chance of survival, other health care personnel (eg, nurses, pharmacists) play key roles in the emergency treatment of a MH crisis. A suspected episode of MH should be followed up with contracture testing to determine MH susceptibility (MHS). Reports of MH should be reported to the North American MH Registry.

Management of malignant hyperthermia

A case of malignant hyperthermia in a young girl with vesicoureteral reflux and multiple congenital abnormalities is discussed. Malignant hyperthermia is a relatively newly defined problem that is associated with anesthesia. It is being recognized with increasing frequency, particularly in children with multiple musculoskeletal anomalies. The term itself is a misnomer. It is a drug-induced syndrome of hypermetabolism that may represent an inborn error of metabolism. Recognition, prophylaxis and crisis management are reviewed, and the use of dantrolene sodium in the care of patients with malignant hyperthermia is discussed. Because recognition of malignant hyperthermia is an important concern for the practicing urologist, the principles of identifying the patient at risk, as well as managing the crisis, should be familiar to the clinician.

Malignant hyperpyrexia. Further muscle studies in asymptomatic carriers identified by creatinine phosphokinase screening

The history, clinical presentation, and management of malignant hyperpyrexia are presented. The aetiology seems to be associated with some inherited abnormality which affects the movement and binding of calcium ions in the sarcoplasmic reticulum, sarcoplasm, and mitochondria. Whether this is a primary muscular defect or secondary to some trophic neural influence is yet to be established. The subjects carrying the abnormal trait show evidence of a myopathy which is subclinical in most instances and revealed only by estimation of serum CPK or biopsy. In some families where the myopathy is clinically obvious there may be, in addition, a variety of musculoskeletal abnormalities. A plea is made for routine monitoring of temperature during anaesthesia and for procainamide or procaine to be readily available in all operating theatres. A history of anaesthetic deaths in a family calls for special care, and, if the serum CPK is elevated, suxamethonium and halothane are to be avoided. Families with orthopaedic and muscular abnormalities are at increased risk and should have estimation of serum CPK before surgery. As a bonus of this study it is suggested that serum CPK estimations be used to screen pigs for selective breeding and so eliminate the disease, which causes soft exudative pork.