Augmentation of vital organ blood flow during experimental cardiopulmonary resuscitation

Clinical outcome from cardiac arrest remains poor. If the time from arrest to restoration of spontaneous circulation can be shortened and resuscitation techniques improved so that higher blood flow and oxygen delivery to vital organs is achieved, it is possible that the outcome from cardiac arrest could improve. This thesis is based on experimental studies of different aspects of blood flow augmentation during cardiopulmonary resuscitation. Using a biological assay, it was found that the biological activity of epinephrine is reduced after injection through an intravenous cannula containing alkaline buffer, but the degree of inactivation is unlikely to be of clinical significance. In a porcine model of ventricular fibrillation, a cardiovascular post-resuscitation syndrome was described. The cardiovascular compromise seen after restoration of spontaneous circulation was characterised by a substantially reduced cardiac index and mixed venous oxygen saturation. Cortical cerebral blood flow and the cerebral oxygen extraction ratio were reduced, and there was a protracted acidosis in cerebral tissue in spite of buffering to normal arterial pH. The cardiovascular post-resuscitation syndrome was in no respect alleviated by Platelet Activating Factor antagonism. Repeated doses of high-dose epinephrine during cardiopulmonary resuscitation were unable to improve cortical cerebral blood flow compared to standard-dose epinephrine, and appeared to redistribute blood flow from the superficial cerebral cortex to other parts of the brain. The novel method of continuous balloon occlusion of the descending aorta during cardiopulmonary resuscitation increased coronary blood flow, cortical cerebral blood flow and the rate of restoration of spontaneous circulation. No detrimental effects were noted after restoration ofspontaneous circulation and deflation of the balloon. A prominent finding was the short duration of increased cortical cerebral blood flow seen after bolus administration of standard-dose epinephrine during cardiopulmonary resuscitation. No evidence of vasoconstriction in superficial cerebral cortex was found after administration of standard-dose epinephrine