ARTERIAL BLOOD-GASES DURING CARDIAC-ARREST - MARKERS OF BLOOD-FLOW IN A CANINE MODEL

Measures of CO2 have been shown to correlate with coronary perfusion pressure and cardiac output during cardiac arrest. We evaluated arterial pH (pH(a)) relative to blood flow during cardiac arrest in a canine electromechanical dissociation (EMD) model of cardiac arrest using different resuscitation techniques. Following 15 min of cardiac arrest, 24 mongrel dogs received epinephrine with continued CPR or closed-chest cardiopulmonary bypass. Central arterial blood gases, end-tidal carbon dioxide (P(et)CO2), coronary perfusion pressure and cardiac output were measured. During CPR, prior to epinephrine or bypass, there was no correlation of pH(a), P(A)CO2 and P(et)CO2, with cardiac output or coronary perfusion pressure. Immediately after instituting the resuscitation techniques, both pH(a) and P(a)CO2 showed a significant correlation with cardiac output (pH(a); R = -0.78, P < 0.001 and P(a)CO2; R = 0.87, P < 0.001) and with coronary perfusion pressure (pH(a); R = -0.75, P < 0.001 and P(a)CO2; R = 0.75, P < 0.001). Eventual survivors (n = 15) had an early significant decrease in pH(a), base excess and a significant increase in P(a)CO2 which was not present in non-survivors (n = 9). Neither pH(a) nor P(a)CO2 correlate with blood flow under low flow conditions of CPR. However, with effective circulatory assistance, pH(a) and P(a)CO2 reflect systemic blood flow and reperfusion washout.