Abstract P129: Oxygen Transport in Post Cardiac Arrest Syndrome With Goal Directed Hemodynamic Optimization
INTRODUCTION. Goal directed hemodynamic optimization has been proposed for the management of the post cardiac arrest syndrome. However the impact of this approach on oxygen transport is uncertain. We aimed to describe whole body and organ specific oxygen transport in hemodynamically optimized post arrest subjects.
METHODS. Six male swine (mean 46.8 kg, SD 2.2) were subjected to 12 min of electrically induced ventricular fibrillation then resuscitated according to standard normothermic American Heart Association Advanced Cardiac Life Support guidelines. Resuscitated animals were managed with fluids and vasopressors to meet goals of CVP 8 to 12 mmHg, MAP >80 mmHg and SvO2 >65%. FiO2 was reduced from 1.0 to 0.5 within 60 min of return of spontaneous circulation (ROSC). Measurements at baseline, cardiac arrest, ROSC, and every 30 min for 6 hours included oxygen delivery (DO2) and consumption (VO2) calculated by reverse Fick method, oxygen extraction ratio (OER), lactate, and tissue oxygen tension (PtO2) of the liver, ileum, hind-limb adductor muscle and sublingual mucosa by phosphorescence quenching method. Heart PtO2 was measured only after ROSC. Data were analyzed using mixed-model ANOVA (p<0.05 taken as significant).
RESULTS. Five animals were resuscitated and analyzed. CVP, MAP and SvO2 achieved target levels from 30 min post ROSC. Compared to baseline, DO2 was significantly higher between 60 and 180 min post ROSC. OER tended to be slightly lower but was not significantly different (p=0.09). VO2 was similar to baseline at all time points post ROSC. Lactate rose significantly at ROSC but fell below 4 mmol/L after 90 min. Liver PtO2 recovered to baseline at ROSC and ileum at 30 min. Muscle PtO2 recovered at 30 min, but became depressed again from 4 hrs. Sublingual PtO2 never returned to baseline. Mean cardiac PtO2 was 44.5 mmHg [95 CI; 25.7, 63.4] at ROSC and remained stable.
CONCLUSION. This model provides a staging point for evaluating post ROSC therapies. Despite attaining target CVP, MAP and SvO2 within 30 min and overall restoration of perfusion and oxygen transport, specific organs displayed differing recovery patterns of PtO2. Future studies will examine the effects of longer arrest times and hypothermia on interventions required to achieve hemodynamic goals.