Anesthesiology
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Malignant hyperthermia (MH), heat stroke, and exercise-induced rhabdomyolysis (ER) were suspected to be related syndromes. However, it is not known whether individuals with history of ER have an increased incidence of susceptibility to MH. To establish an association between ER and susceptibility to MH, the authors determined the MH status in patients with a history of MH-like episodes induced by physical stress. ⋯ Regarding these results, the authors recommend performing muscle biopsies for histologic examination and IVCT in patients with ER. In addition, the patient should be seen by a neurologist and screened for genetic abnormalities to shed light on the genetics of MH.
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Tetrodotoxin-resistant Na(+) channels play an important role in generation and conduction of nociceptive discharges in peripheral endings of small-diameter axons of the peripheral nervous system. Pathophysiologically, these channels may produce ectopic discharges in damaged nociceptive fibers, leading to neuropathic pain syndromes. Systemically applied Na(+) channel--blocking drugs can alleviate pain, the mechanism of which is rather unresolved. The authors investigated the effects of some commonly used drugs, i.e., lidocaine, mexiletine, carbamazepine, amitriptyline, memantine, and gabapentin, on tetrodotoxin-resistant Na+ channels in rat dorsal root ganglia. ⋯ Less negative membrane potential and repetitive firing have little effect on tetrodotoxin-resistant Na(+) current amplitude but increase their sensitivity to lidocaine, mexiletine, and amitriptyline so that concentrations after intravenous administration of these drugs can impair channel function. This may explain alleviation from pain by reducing firing frequency in ectopic sites without depressing central nervous or cardiac excitability.