Does spontaneous ventilation compared to controlled respiration improve cardiovascular responses during halothane anesthesia in healthy volunteers?
Spontaneous ventilation lessens the cardiovascular depression associated with halothane anesthesia compared to controlled respiration.
The effects of duration of anesthesia on the cardiovascular responses to halothane in eight healthy male volunteers were studied during spontaneous ventilation and CO2 challenge. We compared these results with those obtained in a previous study of another group of volunteers during controlled respiration. Spontaneous ventilation lessened the depression of the cardiovascular system associated with halothane anesthesia. Cardiac output, heart rate, mean arterial pressure, left ventricular work, IJ-wave amplitude, and muscle blood flow were all greater during spontaneous than during controlled ventilation. Cardiovascular stimulation also occurred with duration of anesthesia in the presence of spontaneous ventilation. Cardiac output, heart rate, left ventricular minute work, and myocardial function increased 20 to 40 per cent in the course of five hours of halothane anesthesia, while total peripheral resistance and mean right atrial pressure decreased. Finally, halothane (like Forane, fluroxene, ether, and cyclopropane) depressed the cardiovascular responsiveness to carbon dioxide challenge. However, at twice MAC, the depression of the cardiac output and arterial pressure responses was more with halothane than with fluroxene or ether.
Bahlman et al. (Mon,) studied this question.