Anesthesiology
-
We compared the duration of action and recovery times for vecuronium in normothermic and mildly hypothermic patients. Ten patients were actively cooled to a central body temperature near 34.5 degrees C, and ten were maintained at a normothermic central temperature (greater than 36.5 degrees C); temperature was measured in the distal esophagus. Vecuronium 0.1 mg/kg was administered as an intravenous (iv) bolus to all patients, and the evoked mechanical response to train-of-four stimulation was recorded. ⋯ Vecuronium's duration of action (from injection of drug until T1 = 10%) was 28 +/- 4 and 62 +/- 8 min during normothermia and hypothermia, respectively (P less than 0.05). The corresponding values for spontaneous recovery from T1 = 10% to TOF ratio greater than 75% were 37 +/- 15 and 80 +/- 24 min (P less than 0.05), and for neostigmine-induced recovery were 10 +/- 3 and 16 +/- 11 min (difference not significant). We conclude that mild hypothermia increases the duration of action of and time for spontaneous recovery from vecuronium-induced neuromuscular blockade.
-
Intravenous lidocaine has been shown to relieve acute postoperative pain and chronic neuropathic pain. It is not known whether analgesia produced by 2-10 micrograms/ml plasma concentrations of lidocaine is due to an effect on peripheral-pain-transducing nerves or to central nervous system effects. The current study examined effects of analgesic concentrations of lidocaine on injury-induced discharge of A-delta and C fibers, using the in vitro rabbit corneal nerve preparation. ⋯ The median effective concentration (ED50) (5.7 micrograms/ml) corresponds to clinically effective plasma concentrations for analgesia. Electrically evoked nerve conduction was not blocked until lidocaine concentrations were greater than 250 micrograms/ml. Thus, analgesia produced by lidocaine appears to result from suppression of tonic neural discharge in injured peripheral A-delta and C fiber nociceptors.