Phosphorylase ratio and susceptibility to malignant hyperthermia.

Abstract

The ratio of muscle phosphorylase a to total phosphorylase, expressed as a percent, was determined in vastus lateralis muscle of 26 patients to examine the efficacy of this parameter as a method for screening for susceptibility to malignant hyperthermia (MH). As standard screening, all patients also had muscle contracture responses determined to 2% halothane and 0.25-32 mM caffeine at 37 degrees C. Each drug was given separately and not combined. Nine patients were susceptible to MH, based upon caffeine threshold of 2 mM or less (seven patients) or a rapidly developing contracture tension to halothane of more than 400 mg (seven patients, including five with positive caffeine responses). Mean phosphorylase ratio in these nine patients was 14.5 +/- 2.0% (mean, SEM). In the 17 nonsusceptible patients mean phosphorylase ratio (12.4 +/- 1.9%) was not significantly different. The range of phosphorylase ratios in susceptible patients was 6.5-26% while 13 nonsusceptible patients had ratios greater than 6% and up to 29%. The unacceptably high number of false-positive responses in nonsusceptible patients precludes the use of phosphorylase ratio as a definitive diagnostic test.

• Authors: C A Traynor, R A Van Dyke, G A Gronert
• Journal: Anesthesia and analgesia (Anesth Analg) Vol. 62 Issue 3 Pg. 324-6 (Mar 1983) ISSN: 0003-2999 [Print] United States
• PMID: 6299136 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Caffeine
• Phosphorylase a
• Phosphorylases
• Phosphotransferases

Topics

• Adolescent
• Adult
• Caffeine (pharmacology)
• Clinical Enzyme Tests
• Female
• Humans
• In Vitro Techniques
• Male
• Malignant Hyperthermia (diagnosis, etiology)
• Muscle Contraction (drug effects)
• Muscles (enzymology)
• Phosphorylase a (metabolism)
• Phosphorylases (metabolism)
• Phosphorylation
• Phosphotransferases (metabolism)
• Risk