Differential change in cardiac baroreflex sensitivity estimated by sequence and spectral analysis during etomidate anesthesia.

Spontaneous baroreflex sensitivity, high-frequency gain, (0.15-0.35 Hz), and mid-frequency gain (0.07-0.14 Hz) are noninvasive measures of cardiac baroreflex function derived by spontaneous sequence and cross-spectral analysis. To demonstrate the difference between these baroreflex estimates, 14 patients received etomidate (0.3 mg/kg bolus and 0.9 mg/kg/h infusion), lidocaine (60 mg), and vecuronium (0.1 mg/kg) by intravenous injection. The authors found that spontaneous baroreflex sensitivity and high-frequency gain were decreased (p <0.05) after etomidate anesthesia, whereas mid-frequency gain was maintained. Spontaneous baroreflex sensitivity, high-frequency gain, and mid-frequency gain, although compared simultaneously, did not change in a parallel manner. In another 5 patients, who received normal saline only, measures were unchanged. The authors conclude that spontaneous baroreflex sensitivity, high-frequency gain, and mid-frequency gain are not interchangeable. Experimental results on baroreflex control depend on the parameter selected.