The Effect of Nociceptive Stimulation on the Changes in Hemodynamics and Oxygen Transport Induced by Hemorrhage in Anesthetized Pigs

The effects of somatic nociceptive afferent stimulation on aspects of cardiac function and oxygen transport were examined in a model of hemorrhage in anesthetized pigs. The brachial nerves were stimulated (BNS) alternately to obtain a rise in heart rate of 18% and in mean arterial pressure of 17%. This stimulation was started 75 minutes before the start of hemorrhage and maintained throughout and after the withdrawal of blood. The animals were bled at a rate of 0.75 ml/min.kg until a total of 30 ml/kg had been removed. At the end of hemorrhage the reductions in cardiac index (CI), stroke volume (SV), and left ventricular stroke work (LVSW) were greater in the BNS group compared with controls. The nociceptive stimulation also elicited greater reductions in oxygen delivery (DO2I) and oxygen consumption (VO2) and a greater rise in the arterial plasma lactate concentration. Thus it seems that nociceptive stimulation exacerbates the changes in systemic oxygen transport and cardiac function induced by hemorrhage.