Abstract 289: Effect of Elevated Legs on Hemodynamic Performance During Cardiopulmonary Resuscitation in a Porcine Model of Cardiac Arrest

Abstract

Purpose of the study: During advanced life support (ALS) end-tidal carbon dioxide (EtCO 2 ) reflects cardiac output (CO). A recent clinical study found an association between passive leg raising (PLR) and increased EtCO 2 during ALS. This may reflect a transient increase in pulmonary blood flow and CO, but might cause a detrimental decrease in coronary perfusion pressure (CPP). We evaluated the effect of PLR during experimental ALS in a randomized, factorial design. Materials and methods: In nine anesthetized domestic pigs (30±1.8 kg) ventricular fibrillation was induced electrically. After 3 minutes of no-flow, mechanical chest compressions (5cm @ 100 min -1 ) were started. During four 5-minute segments of CPR we measured CO, EtCO 2 , perfusion pressures, carotid and cerebral cortical microcirculatory blood flow (MBF) and CPP (the average of the positive pressure difference between decompression aortic pressure (AP) and right atrial pressure (RAP)) at minute 2 and 4. Interventions were provided in a randomized sequence with PLR vs supine position, with or without epinephrine (0.5mg iv). Values are given as mean±standard deviation. Results: PLR did not increase EtCO2 compared to supine position (3.1±0.7 vs 3.0±0.8 kPa), but CO was minimally increased from 1.1±0.3 to 1.2±0.3 Lmin -1 ,(p=0.003). PLR did not significantly increase AP (57±15 vs. 48±18 mmHg, p=0.3), but RAP was higher (43±10 vs. 31±7, p=0.003). However, no difference was found in CPP due to marked variation in both groups (median(range): PLR 20 (9,43) and supine 17(9,58)). The effect of epinephrine during this experimental setup was minimal. Conclusion: We did not find a positive effect of PLR during experimental ALS, but there were no obviously detrimental effects either.