Anesthesia and analgesia
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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 effects of propofol on the 40-Hz auditory steady-state response and on the electroencephalogram in humans.
The auditory steady-state response (ASSR) is a nearly sinusoidal electrical response of the brain to auditory stimuli delivered at fast rates. The amplitude of the response is largest for stimulus rates near 40/s, hence the label 40-Hz ASSR. We have studied the effects of propofol (1.5 mg/kg) on the 40-Hz ASSR in 14 patients. ⋯ Recovery of the 40-Hz ASSR occurs whether or not consciousness is regained, but the 40-Hz ASSR tends to be larger after the return of consciousness. An association between higher amplitude 40-Hz ASSR and the return of consciousness could not be conclusively established, perhaps because of low signal-to-noise ratio in three patients. The 40-Hz ASSR did not offer any clear advantage over the SEF in predicting the return of consciousness.
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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.