[Diagnosis of susceptibility to malignant hyperthermia using the in vitro contracture test]

Though a malignant hyperthermia (MH) crisis is still a critical event during general anesthesia, recent developments in prophylaxis and treatment should help in avoiding fatal episodes. The best means to avoid MH episodes would be early recognition of MH susceptibility. Today the only reliable test to identify MH susceptibility is the in vitro contracture test. Thus, to diagnose MH susceptibility we performed this test on muscle biopsies from 26 individuals who: (1) had an event during general anesthesia that may have been indicative of MH (4 patients); (2) had a family member with a medical history of MH (20 patients); or (3) had unexplained elevated CK levels (1 patient). The criteria according to which patients were submitted to the testing are shown in detail in Table 1. We used the standardized version of the contracture test that has been proposed by the European Malignant Hyperpyrexia Group. Muscle biopsies (20-30 mm long, 8 mm diameter) were dissected into 8-10 small bundles (2-3 mm diameter) and tested within 3 h post-biopsy in four independent tissue baths with various concentrations of caffeine or halothane. According to the concentration of caffeine or halothane necessary to elicit contractures exceeding a predefined force threshold (20 mN), it was possible to classify the patients as MHS (MH-susceptible), MHE (equivocal), or MHN (negative). In addition to the in vitro test, clinical, laboratory, and neurophysiological data were collected from these patients and correlated with the individual test results (Table 2). Thirteen patients were classified as MHS, five were MHE, and seven patients MHN (Fig. 3).(ABSTRACT TRUNCATED AT 250 WORDS)