IMPROVEMENT IN OXYGEN EXTRACTION CAPABILITIES DURING PROSTAGLANDIN E ADMINISTRATION IN EXPERIMENTAL SEPSIS Haibo Zhang. Malik Benlabed Herbert Snaoen. Duc Nam Nguyen. Jean-Louis Vincent To investigate whether prostaglandin Ei (PGE i) could improve the 02 extraction capabilities in severe sepsis, we studied the 02 uptake/Oz delivery (VO2/DO2) relationship during an acute reduction in blood flow induced by cardiac tamponade in endotoxemic dogs. 44 anesthetized, paralyzed and ventilated dogs were divided into 2 series of experiments. A first series included 3 groups of 10 for each. Group A served as a control receiving 20 mlkg.h of saline iv.. Group B received 100 ng/kg.min of PGEi along with the same saline infusion. Group C received the same dose of PGEi alone. A bolus of E coil endotoxin (2 mg/kg) was injected in each dog. Tamponade was then induced by repeated bolus injections of saline into the pericardial space. V02 derived from the expired gases and D02 calculated from the product of cardiac index and 02 content. PGE i+fluids resulted in significant increases in stroke volume, cardiac output, DOz and reductions In systemic and pulmonary vascular resistance. Stroke volume and cardiac output were higher in the PGEt+fluids than in the PGE i alone group. V02 levels at critical D02 (DOmrk) were identical. DO2.n, which was 12.2±2.8 ml/kg.min in the control group, was decreased to 9.8±2.0 in the PGEi+fluid's and 9.3±2.7 mVkg.min in the PGEi alone group (both p<0.05). Critical 02 extraction ratio (02ER,,e) which was 47±14 % in the control, was increased to 63±16 % in the PGE i+fluids and 61±17 % in the PGEi alone group (both p<0.05). The slope of the supply-dependent line was also increased from 0.44±0.15 in the control to 0.64±0.15 in the PGE,+fluids (p<0.01) and to 0.57±0.24 (p>0.05) in the PGEi alone group. To investigate whether PGEi also improves 02 extraction capabilities in the absence of endotoxin, a second series experiments was performed in 14 dogs receiving 20 mVkg.h of saline (N=7) alone or plus PGEn at 100 ngikg.min (N=7). DOzo,x was 10.7±1.8 mllkg.min in the control group vs 11.3±2.9 mlkg.min in the PGEi group (NS). OsERcri tended to be higher in the PGEi than in the control group (68±13% vs 60±15 %, p=0.054). We conclude that PGEi could almost entirely restore tissue 02 extraction capabilities after endotoxin challenge on this dog model. The effects on 02 extraction were present with or without concurrent saline administration, but the combination of PGEi with fluids improved global hemodynamics. In control conditions, the influence of PGE, on the tissue 02 extraction capabilities was minimal.