Anesthesiology
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Randomized Controlled Trial Clinical Trial
Anesthesia for laparoscopic cholecystectomy. Is nitrous oxide contraindicated?
Since it has been suggested that the use of nitrous oxide (N2O) may contribute to bowel distention, we evaluated the effects of N2O on operating conditions during laparoscopic cholecystectomy in 50 healthy patients using a double-blind protocol design. All patients received the same preanesthetic medication (midazolam, 2 mg intravenously) and induction of anesthesia consisted of intravenously administered fentanyl 1.5 micrograms.kg-1, thiopental 4-6 mg.kg-1, and a nondepolarizing muscle relaxant. For maintenance of anesthesia, patients were randomly assigned to one of two treatment groups: group 1 (n = 26) received isoflurane with 70% N2O in oxygen (O2), whereas group 2 (n = 24) received isoflurane in an air/O2 mixture. ⋯ Finally, the incidence of postoperative nausea and vomiting was similar in both treatment groups. The surgeon was able to correctly determine that N2O had been administered only 44% of the time. Thus, N2O had no clinically apparent deleterious effects during laparoscopic cholecystectomy.
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Clinical studies have reported that body core temperature decreases during prolonged surgery and anesthesia. Although this finding has been attributed primarily to increased heat loss resulting from exposure of body cavities and infusion of cold solutions, it is generally recognized that anesthesia interferes with the thermoregulatory system. The present study examined the effects of mild narcosis induced by 30% N2O on shivering thermogenesis and cutaneous thermoregulatory vasoconstriction in humans, during exposure in a much more intense peripheral thermal stimulus than the ones often used in clinical studies. ⋯ No significant difference was observed in cutaneous thermoregulatory vasoconstriction between the two experimental conditions, as indicated by the Tsk-gr values. The estimated Tes threshold for shivering (estimated from the O2 consumption vs. delta Tes regression) was reduced by 0.95 +/- 0.26 (SE) degrees C during the immersion phase and by 0.39 +/- 0.05 (SE) degrees C during the rewarming phase in the N2O condition compared to the control conditions. Although the thermosensitivity (gain) of shivering appeared preserved during the immersion phase, it was reduced during the N2O rewarming phase.(ABSTRACT TRUNCATED AT 400 WORDS)
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The effects of propofol, etomidate, midazolam, and fentanyl on motor evoked responses to transcranial stimulation (tc-MERs) were studied in five healthy human volunteers. Each subject, in four separate sessions, received intravenous bolus doses of propofol 2 mg.kg-1, etomidate 0.3 mg.kg-1, midazolam 0.05 mg.kg-1, and fentanyl 3 micrograms.kg-1. Electrical tc-MERs (tce-MERs) were elicited with anodal stimuli of 500-700 V. ⋯ Etomidate caused significant but transient depression of tc-MER amplitude. However, there was considerable intersubject variability. Latency did not change significantly after any drug.(ABSTRACT TRUNCATED AT 250 WORDS)
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Editorial Comment
Improving anesthesiologists' performance by simulating reality.