MALIGNANT HYPERTHERMIA TESTING IN PATIENTS WITH PERSISTENTLY INCREASED SERUM CREATINE-KINASE LEVELS

We describe 49 neurologically asymptomatic patients with persistently increased serum creatine kinase (CK) levels (idiopathic hyperCKemia or IHCK) who were referred to our institution for diagnostic muscle biop sy, including malignant hyperthermia (MH) susceptibility testing betwe en 1979 and 1993. Muscle biopsy samples of the vastus lateralis were o btained for histologic analysis and MH contracture testing with haloth ane and caffeine. From 1979 to November 1987, patients were tested for MH in accordance with a standardized institutional protocol. After No vember 1987, contracture testing was performed according to the recent ly adopted North American MH Group protocol. In both protocols, a pati ent was considered to be MH susceptible (MHS) if one or more muscle st rip demonstrated an abnormal contracture response after exposure to 3% halothane, 2% halothane, or caffeine alone. Twenty-four of the 49 IHC K patients (49%) had positive contracture tests. No significant correl ation was found between the magnitude of CK increase and the incidence of MHS or histologic abnormalities. Unexplained persistently increase d CK levels in an otherwise healthy patient should alert the anesthesi ologist to the possibility of MI-IS and/or myopathy.