VAGAL INNERVATION INFLUENCES THE WHOLE-BODY OXYGEN CONSUMPTION-DELIVERY RELATIONSHIP IN THE DOG

Vagotomy alters regional blood flow distribution by interrupting the t onic central inhibitory effect of cardiopulmonary vagal afferent nerve s on sympathetic outflow predominantly to the renal, splanchnic, and c utaneous circulations. We hypothesized that the alteration of blood fl ow distribution by vagotomy would lead to disruption of the oxygen con sumption-oxygen delivery relationship (VO2/DO2), increase critical DO2 (DO2Crit), and decrease whole-body oxygen extraction ratio (O(2)ER). Nineteen chloralose-anesthetized, paralyzed, splenectomized dogs were submitted to either bilateral vagosympathectomy (n = 7), bilateral vag otomy (n = 6), or sham denervation (n = 6) following baseline cardiore spiratory parameter measurement. VO2 was measured by indirect calorime try and carotid blood flow by ultrasonic flow probe. Incremental hemor rhages (1-5 mL/kg) were performed to determine the VO2/DO2 relationshi p. Cardiorespiratory parameters were measured after each hemorrhage at steady-state VO2. DO2Crit was derived from the VO2/DO2 relationship u sing a best-fit regression analysis technique. The average DO2Crit val ues of the vagotomy (9.1 +/- .54) and vagosympathectomy (11.5 +/- 1.2 mL/min/kg) groups were significantly greater than the control group (7 .72 +/- .43). After hemorrhage had been performed to a point that decr eased mean arterial pressure to approximately 70 mmHg from baseline va lues, carotid blood flow in the vagosympathectomy group was significan tly greater than the control group. We conclude that vagotomy disrupts the VO2/DO2 relationship. Vagosympathectomy causes a severe disruptio n of the VO2/DO2 relationship, probably by the combined effect of vago tomy and interruption of sympathetic nervous system control of blood f low to the head and neck.