Anesthesia and analgesia
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Anesthesia and analgesia · May 1996
Randomized Controlled Trial Comparative Study Clinical TrialThe effect of sevoflurane and isoflurane on the neuromuscular block produced by vecuronium continuous infusion.
Volatile anesthetics enhance the action of neuromuscular blockade to various degrees, although the influence of sevoflurane on the neuromuscular block has not yet been characterized. The purpose of this investigation is to determine the vecuronium infusion rate requirement under sevoflurane anesthesia and to compare it to that of isoflurane anesthesia. Twenty patients scheduled for otorhinolaryngologic surgery were randomly assigned to receive either sevoflurane (SEV) or isoflurane (ISO) at 1 minimum alveolar anesthetic concentration (MAC) (1.7% and 1.2%, respectively) in combination with 67% nitrous oxide. ⋯ The plasma concentrations of vecuronium (CVEC) and 3-desacetylvecuronium (CDES) at steady state were measured with a gas chromatographic assay. There was no difference between SEV and ISO in the following variables: the vecuronium infusion rate requirements to achieve 90% muscle relaxation (0.42 +/- 0.11 [SEV] vs 0.40 +/- 0.10 [ISO] microgram-kg-1.min-1), CVEC (144.4 +/- 38.1 [SEV] vs 149.7 +/- 69.2 [ISO] ng/mL), CDES (57.2 +/- 20.3 [SEV] vs 65.3 +/- 26.1 [ISO], ng/mL), and plasma vecuronium clearance (2.85 +/- 0.86 [SEV] vs 3.19 +/- 1.24 [ISO] mL.kg-1.min-1). This study indicates that SEV at 1 MAC requires a vecuronium infusion rate similar to that of ISO at 1 MAC to achieve 90% muscle relaxation.
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Anesthesia and analgesia · May 1996
Comparative StudyInteraction of heart rate and hypothermia on global myocardial contraction of the isolated rabbit heart.
We studied the effects of mild hypothermia on cardiac contractility in isolated rabbit hearts perfused with Krebs-Henseleit solution according to the technique of Langendorff. Isovolumetric left ventricular pressure (LVP) was measured with a fluid-filled balloon. Hearts were paced after induction of atrioventricular block. ⋯ At pacing rates > or = 90 bpm, lower systolic LVP, higher diastolic LVP, and lower positive and negative LV dP/dt were obtained in hypothermic (93 +/- 12 mm Hg, 55 +/- 18 mm Hg, 584 +/- 137 mm Hg/s, and 323 +/- 57 mm Hg/s at 210 bpm, respectively) compared to normothermic hearts (123 +/- 4 mm Hg, 10 +/- 4 mm Hg, 1705 +/- 145.5 mm Hg/s, and 1155 +/- 78 mm Hg/s at 210 bpm, respectively.) The duration of mechanical diastole was reduced or suppressed in these hearts. Exposure to the beta-adrenoreceptor agonist, isoproterenol, improved this diastolic dysfunction during hypothermia and pacing at high rates, suggesting that the sarcoplasmic reticulum Ca2+ uptake might be involved. Our data are also consistent with an increase in myofilament Ca2+ sensitivity that is opposed by isoproterenol during hypothermia.