Clinical Usefulness of the Muscle Contracture Test: Time to Reevaluate?

Abstract

Red Deer Regional Medical Center, Red Deer, Alberta, Canada. ikwetny@hotmail.comIn a recent article, Tautz et al. 1discussed the use of a muscle contracture test for diagnosis of malignant hyperthermia (MH) susceptibility. They correctly noted that there is a 2% chance that contracture testing will incorrectly mislabel an MH-susceptible individual as normal. It is difficult to believe that any of my colleagues will expose a patient to a 2% risk of severe complications by giving triggering anesthetics. In my opinion, the fact that a patient has been evaluated for MH will be a strong indication for using nontriggering anesthesia management. Tautz et al. stated that there is a consensus among experts that a person who has had contracture testing and who is labeled not susceptible can safely receive triggering anesthetics. Unfortunately, they did not provide references to any written guidelines or consensus statements on that issue.Tautz et al. mentioned another reason for using the contractility test: the fact that for certain patients (children, severe asthmatics, and patients with difficult airways) potent inhaled anesthetics are useful. Yes, they are useful. But how safe are they? Is 98% safe enough when we have 100% safe nontriggering alternatives available? Most biopsy centers do not perform these tests for children under 5 yr old.*In the very few situations in which inhalation induction is the safest approach (e.g ., acute epiglottitis or a difficult pediatric airway), the anesthesiologist should be prepared to monitor and treat a possible MH crisis regardless of the patient's test results.I recall consulting one of my own patients regarding contracture testing after an MH crisis.2According to the clinical grading scale, this patient's likelihood of MH was “almost certain.”3The patient and family were informed, and the patient was advised to wear a Medic Alert bracelet. However, I felt uneasy recommending a procedure that was very expensive ($6,000 USD), invasive (need for another anesthesia, relative disability for 3–4 days), and burdensome (3-h flight to nearest biopsy center), with no clear benefits for the patient. In their article, Tauzt et al. wrote: “We cannot fault a clinician who wishes to give a nontriggering anesthetic to a person who has had contracture testing and who is not susceptible to MH.” Thank you for not blaming me for playing it safe! But perhaps we should fault an anesthesiologist who unnecessarily canceled elective procedures because he or she was uncomfortable anesthetizing the patients before their MH status had been established by biopsy. The debate about the usefulness of the muscle contracture test has had a long history.4In our era of evidence-based medicine and cost-effective analyses, should we not also reevaluate muscle biopsy testing for MH?Red Deer Regional Medical Center, Red Deer, Alberta, Canada. ikwetny@hotmail.com