Anesthesiology
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The authors investigated the hemodynamic, metabolic, electroencephalographic (EEG), and electromyographic (EMG) characteristics of narcotic-induced rigidity during induction of anesthesia with alfentanil (175 micrograms/kg) in 10 patients. Thiopental (4 mg/kg) was administered to a ten-patient control group. Rigidity was quantified in eight muscle groups (sternocleidomastoid, deltoid, biceps, forearm flexors, intercostal, rectus abdominus, vastus medialis/lateralis, and gastrocnemius). ⋯ The immediate increase in central venous pressure with the onset of rigidity, along with occasional simultaneous parallel variations in central venous pressure and the EMG, strongly suggest a mechanical mechanism for the change in central venous pressure. The metabolic changes during rigidity may be partly related to the absence of the normal cardiovascular reflexes that are reported to occur during voluntary isometric muscle contractions. A neurochemical mechanism of narcotic-induced rigidity is briefly reviewed.