Anesthesiology
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Comparative Study
Amide local anesthetic alterations of effective refractory period temporal dispersion: relationship to ventricular arrhythmias.
The hemodynamic and electrophysiologic effects of bupivacaine, etidocaine, mepivacaine, and lidocaine were investigated in 32 pentobarbital-anesthetized adult mongrel dogs. Following equipotent dosing, all four agents produced similar hemodynamic effects: decrease in stroke volume and cardiac output, heart rate slowing, increase in systemic vascular resistance, and increases in pulmonary arterial pressure (PAP) and pulmonary capillary wedge pressure (PCWP). The effects of the various agents on the ECG were different. ⋯ Six of seven bupivacaine, six of seven etidocaine, two of eight mepivacaine, and none of eight lidocaine animals sustained a polymorphic, undulating ventricular tachycardia similar to Torsades de Pointes following burst ventricular pacing. The results of this study suggest that bupivacaine, etidocaine, and occasionally mepivacaine can result in a Torsades de Pointes-like syndrome following intravenous administration. The magnitude of ERP temporal dispersion differences between the various agents appears to explain their differential arrhythmogenicity.
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Median nerve somatosensory evoked potentials (SSEPs) were recorded in 21 healthy subjects anesthetized with halothane, isoflurane, or enflurane (with and without nitrous oxide) for abdominal or pelvic surgery. Recordings were made prior to induction, then at 0.5 MAC increments of each volatile agent with 60% N2O up to 1.5 MAC, and, finally, at 1.5 MAC without N2O. All three volatile anesthetics produced dose-related reductions in the amplitude and increases in the latency of the cortical component of the SSEP. ⋯ At 1.5 MAC of each volatile agent, cortical latency decreased and amplitude increased when nitrous oxide was discontinued. The results suggest that in neurologically intact patients, end-tidal concentrations of 1.0 MAC halothane and 0.5 MAC enflurane or isoflurane (each in 60% N2O) can be compatible with effective SSEP monitoring. Volatile anesthetic concentrations consistent with satisfactory somatosensory-evoked potential recording may be greater if N2O is not employed.