EFFECTS OF LACTATE ON CROSS-SPECTRAL ANALYSIS OF HEART-RATE, BLOOD-PRESSURE, AND LUNG-VOLUME IN NORMAL VOLUNTEERS

Baroreceptor reflex sensitivity, coherence functions, and transfer fun ctions between respiration and heart rate, and between respiration and blood pressure, were studied in nine normal volunteers before and aft er intravenous sodium lactate infusions. Cross-spectral analysis was u sed to examine heart rate, finger blood pressure, and respiration obta ined with the subjects in a supine posture during spontaneous breathin g. Sodium lactate produced a significant decrease of the modulus betwe en respiration and heart rate (beats/min/l). There was no such change for the placebo infusions. The absence of a significant difference in the modulus between systolic blood pressure and heart rate for placebo or lactate indicated that there were no significant changes in the ba roreceptor sensitivity index. These findings suggest that lactate infu sions are associated with a decrease in cardiac vagal function.