Not Every Hypermetabolic State Is Due to Malignant Hyperthermia!

Abstract

To the Editor: We have concerns about the diagnosis of malignant hyperthermia (MH) in a recent case report by Lichtman and Oribabor (1). As the authors stated “several items in this patient’s postoperative course were atypical ….” One hour postoperatively the patient developed a hypermetabolic state with combined respiratory and metabolic acidosis. This state was successfully treated with dantrolene. The fact that dantrolene was effective is not surprising. Muscle rigidity from any cause places considerable metabolic demand on the body, which is effectively attenuated by blocking sarcoplasmic calcium release by dantrolene. Indeed, dantrolene is effective in other hypermetabolic diseases, such as malignant neuroleptic syndrome (2) and is an effective therapeutic strategy to reduce muscle protein breakdown and muscle lactate formation (3). Despite the potentially positive family history and muscle rigidity, there were no other clinical signs of MH. There are many reasons for postoperative hypermetabolic states, e.g., sepsis, hypoperfusion, and propofol infusion syndrome (4–6). It would have been useful had the authors discussed alternatives and not focused on only one possible diagnosis. MH is defined as a pharmacogenetic disease, where triggering agents (volatile anesthetic agents and depolarizing neuromuscular blocking agents) initiate a hypermetabolic reaction in genetically susceptible patients. This definition separates MH from other hypermetabolic states. We do not question the choice of dantrolene for this patient, although we are not aware of the evidence to initiate an oral dantrolene therapy. We similarly are unaware of evidence to support the conclusion to consider off-pump CABG rather than traditional hypothermic CPB in MH susceptible individuals. Lastly, although we respect the patient’s decision to refuse testing for MH, we are disappointed that further testing could not be done. Molecular genetic investigations are now available in North America (7) and alternative minimal invasive methods have been recently presented (8). It is particularly odd that patient without symptomatic cardiac disease would agree to coronary bypass grafting in order to improve his preoperative condition for the planned shoulder surgery, but refuse testing for MH, and why the currently proposed diagnostic approach for MH testing has not been applied to this patient and his family (7). Thierry Girard, MD Albert Urwyler, MD Department of Anesthesia University Hospital Basel CH 4031 Basel Switzerland [email protected]