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 StudyJugular venous bulb oxyhemoglobin saturation during cardiac surgery: accuracy and reliability using a continuous monitor.
Previous studies have demonstrated the feasibility of continuously monitoring jugular venous oxygen saturation (SjO2) with a fiberoptic catheter during hypothermic cardiopulmonary bypass (CPB). In the present study, with patients maintained at either moderate (28 degrees C) or mild (32-34 degrees C) hypothermia during CPB, SjO2 values obtained from a fiberoptic catheter were compared to intermittent samples analyzed by a co-oximeter. Twenty patients scheduled for elective coronary artery or valvular surgery had a 5.5 Fr Opticath catheter inserted into the left internal jugular bulb after induction of general anesthesia. ⋯ Catheter and co-oximetry SjO2 values obtained at four time points--1) pre-CPB, 2) target CPB temperature, 3) mid-rewarming, and 4) post-CPB--were compared using linear regression, Bland-Altman analysis, and Shrout-Fleiss interclass correlation coefficient analysis. These statistical methods revealed poor correlation between the catheter and co-oximetry SjO2 values: r = 0.44 by linear regression and 0.32 by interclass correlation coefficient analysis, and was unacceptably discrepant by Bland-Altman analysis. Oxyhemoglobin saturation values obtained continuously from a jugular venous bulb fiberoptic catheter during CPB may not accurately reflect true oxyhemoglobin saturation, and caution is warranted when interpreting SjO2 values obtained from a fiberoptic catheter during CPB.
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Anesthesia and analgesia · May 1996
Comparative StudySpectral analysis of arterial pressure variability during induction of propofol anesthesia.
We studied the effect of continuous infusion of propofol on spectral components in systemic arterial pressure (SAP) signals in 35 consenting patients undergoing abdominal surgery. Anesthesia was induced with intravenous bolus administration of propofol (2.0 mg/kg), followed by infusion at either 5 mg.kg-1.h-1 (Group 1, n = 18) or 10 mg.kg-1.h-1 (Group 2, n = 17). Tracheal intubation was facilitated by administration of vecuronium (0.1 mg/kg). ⋯ There were 14.1-, 2.8-, and 2.8-fold increases in the respective components of the SAP signal in Group 2. At all intervals, the spectral components of SAP, however, did not correlate well with the plasma concentration of propofol in either group. These results suggest that spectral analysis of SAP signals may provide an alternative for assessing autonomic activities, such as the sympathetic response, to tracheal intubation during propofol anesthesia.
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Anesthesia and analgesia · May 1996
Comparative StudyThe use of a circumferential cathode improves amplitude of intraoperative electrical transcranial myogenic motor evoked responses.
Measurement of motor evoked responses to transcranial electrical stimulation (tc-MER) is a technique for intraoperative monitoring of motor pathways. Since most anesthetics significantly reduce motoneuronal excitability, optimal stimulation paradigms should be sought. We compared the efficiency of stimulus delivery using two different configurations of the cathode component of the stimulating electrode pair (circumferential: Fz, F3, F4, A1, and A2 versus a single cathode at Fz). ⋯ There was no significant difference in onset latency between electrode configurations. The observed tc-MER amplitude augmentation with the use of a circumferential cathode might allow tc-MER monitoring in those patients who do not have sufficiently reproducible responses when a single cathode is used. A possible explanation is that the circumferential cathode alters the direction of the electrical currents in the cortex, resulting in more efficient depolarization of cortical motor neurons.
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Anesthesia and analgesia · May 1996
Perioperative distribution of pulmonary vascular resistance in patients undergoing coronary artery surgery.
This study was undertaken to measure distribution of pulmonary vascular resistance (PVR) perioperatively in patients undergoing coronary artery bypass grafting (CABG) and to examine the effects of cardiopulmonary bypass (CPB) on pulmonary capillary pressure (Pc) relative to wedge pressure (Pw). Pulmonary artery catheters were placed before anesthetic induction in 18 patients scheduled for elective CABG and systemic hemodynamic variables were measured. Pulmonary artery pressure was recorded during balloon inflation and stored for off-line determination of Pc. ⋯ Administration of large-dose opioid anesthesia had no significant effect (P > 0.05) on total PVR or on segmental distribution of vascular resistance. At all data points, Pc was significantly larger than Pw (P < 0.05). This study demonstrates that perioperative measurement of Pc is feasible, that during CABG under these conditions, relative contribution of arterial and venous resistances remain relatively unchanged, that Pc is always larger than Pw, and that the administration of large-dose opioid anesthesia has a minimal effect on pulmonary vascular hemodynamics.