An injection of caffeine can reveal whether patients have a rare life-threatening reaction to anesthesia known as malignant hyperthermia, or MH, reported researchers in the May 4 issue of The Lancet.
MH is a disorder in which volatile anesthetics and depolarizing muscle relaxants induce a potentially hyper-metabolic syndrome in skeletal muscles. Susceptibility to MH is diagnosed by a test that requires an open muscle biopsy sample. This screening detects only 20 to 40 percent of susceptible patients.
Researchers at the University of Würzburg in Germany theorized that an intramuscular injection of caffeine increases local partial pressure of carbon dioxide, or PCO2, in people who are susceptible to malignant hyperthermia.
According to the researchers, caffeine induces abnormal shortening or shrinkage in the skeletal-muscle bundles of patients who are susceptible to MH by increasing sarcoplasmic calcium release.
Researchers injected 500 microliters of caffeine 80 millimolar per liter into 12 subjects who were known to be susceptible to malignant hyperthermia, eight subjects who were not susceptible but had a family history of MH and seven healthy control subjects.
In all 12 susceptible subjects, PCO2 temporarily increased to a maximum of 63 millimeters of mercury compared with 44 mg Hg in the nonsusceptible subjects and 42 mm Hg in the control subjects.
Researchers said they want to study larger numbers of subjects in a multicenter trial to define sensitivity and specificity before this test can allow for definite diagnosis of susceptibility to MH.
