Malignant hyperthermia (MH) diagnostic biopsy centers across North America have not previously been standardized in regard to protocols and specific muscles. Recent standardization criteria prompted this study of the vastus and rectus abdominis muscles. This study evaluated changes in
contracture tension after electrical stimulation of 271 bundles taken from the vastus (n = 16) and rectus abdominus (n = 19) muscle biopsies of normal individuals when exposed to tissue
baths in the absence of and in the presence of
caffeine (0.5, 1.0, 2.0, 4.0, 8.0, and 32.0 mM) alone,
halothane (1% or 3%) alone, or the combination of
halothane (1%) plus
caffeine (0.25, 0.5, 1.0, 2.0, 4.0, and 32.0).
Caffeine threshold concentration was that concentration of
caffeine that produced
a 7% increase in tension.
Caffeine specific concentration (CSC) and
halothane caffeine specific concentration (HCSC) were those concentrations of
caffeine alone or of
halothane plus
caffeine that produced a 1 g increase in tension. The concentration of
caffeine alone that increased the
contracture tension by 7% averaged 6.7 +/- 0.3 mM for vastus, significantly greater than 4.1 +/- 0.2 mM for the rectus muscle biopsies.
Caffeine specific concentration was significantly greater for vastus muscle (7.7 +/- 0.7 mM) than it was for rectus muscle (4.9 +/- 0.4 mM). Three percent
halothane alone showed
contractures in 3/41 vastus (all less than 0.5 g) and 18/54 rectus muscle bundles (8 greater than 0.5 g). Mean HCSC was statistically significantly greater for vastus muscle (1.9 +/- 0.2 mM) than for rectus muscle (1.2 +/- 0.2 mM).(ABSTRACT TRUNCATED AT 250 WORDS)