A SWINE MODEL OF HEMORRHAGIC SHOCK (HS) FOR THE DEVELOPMENT OF NOVEL MARKERS OF SHOCK SEVERITY

Abstract

Currently available markers of shock severity are insensitive and fail to differentiate compensated from decompensated HS. OBJECTIVE: To develop a model of HS with a 5-hour mortality rate of near 50%, and to utilize this model to identify markers of shock severity and the transition from compensated to decompensated shock. METHODS: 25 anesthetized swine (20 - 25 kg) underwent splenectomy and placement of arterial, peripheral and portal venous, PA, and LV catheters, and liver microdialysis probes. Animals were bled to a mean arterial pressure (MAP) of 40mmHg, and maintained at that MAP for 90 minutes. After 90 min, animals were resuscitated to normal physiological parameters with shed blood and lactated Ringer's. Regional blood flow was measured via the microsphere technique. Animals were observed for 5 hrs following the 90- min shock period. RESULTS: 5-hour mortality was 56%. Mean survival times in Survivors (S) vs Nonsurvivors (NS) were 390(0) vs 174(77) minutes. Hemorrhage volumes were 29(7) and 28(7) ml/kg in S vs NS (p = 0.680; t-test). Standard parameters such as base deficit (BD) and arterial lactate (LAC) did not differ between S and NS (BD p = 0.380; LAC p = 0.365; rmANOVA). Cardiac output (CO) (p = 0.01), mixed venous O2 saturation (MVO2Sat) (p = 0.048), and O2 consumption (VO2) (p = 0.018) were significantly greater in S vs NS over time (rmANOVA). Ninety-minute CO, MVO2Sat, ileal blood flow (IBF), and VO2 were predictive of outcome (Table). Tissue and plasma cytokine data are pending. CONCLUSION: In this HS model, survival was not predicted by standard easily measured physiologic parameters, but was predicted by small bowel perfusion, CO, MVO2Sat, and VO2. These data suggest that future studies to define markers of shock severity should focus in these areas.Table