INABILITY TO EASILY PREDICT INDIVIDUAL DEATHS IN A HEMORRHAGE AND RESUSCITATION MODEL

Abstract

While working on a hemorrhage with low-pressure stabilization protocol, we examined the possibility of identifying individual animals' short term outcomes prior to occurrence using the hemorrhage patterns of several variables currently used or suggested to identify patients and animals as in severe hemorrhagic shock. Methods: 8 anesthetized, ventilated dogs were hemorrhaged (H, 90min mean arterial pressure [MAP] = 35- 40mmHg or MAP < 30mmHg>10min or MAP < 25mmHg>1min), hypotensively stabilized (S, 120min enalaprilat 0.01mg/kg/hr + hemoglobin based oxygen carrier [HBOC] or 7.8% hypertonic saline dextran 70 [HSD] for MAP = 40-45mmHg), resuscitated (60min lactated Ringer's for MAP = 75-80mmHg), then only monitored (60min no fluids), and euthanized. Results: There were 2 non-survivors: NS1 (1 of 5 HBOC, died 117min into S) and NS2 (1 of 3 HSD, died 9min into S). Patterns of continuous, non-invasive variables: Non-survivors had the highest (NS2) and 2nd lowest (NS1) heart rates. All the animals' mean arterial pressures and end-tidal CO2s (related to cardiac output) were completely intermingled. Foreleg muscle StO2 was highest in NS1 (80%s throughout H) and intermingled with the 4 lowest survivors in NS2 (1% for the 1st third of H rising to 10% to 30%s for the remainder of H). Patterns of discontinuous and/or invasive variables: Shed blood volumes in NS1, NS2, and 2 survivors were essentially equivalent (38-40mL/kg) and less than those of the 4 other survivors (45-56mL/kg). All SvO2 values were intermingled. The start H base excess values were intermingled. The end H base excesses were NS1 = −18.8, NS2 = −19.2, 2 survivors each = −19.0, other survivors −13.9 to −17.5 mmol/L. Conclusions: Within our severely hemorrhaged group, the hemorrhage values and obvious patterns of the monitored variables failed to distinguish those individual animals that would undergo cardiovascular collapse despite receiving the same treatment from those that would survive. (Funding: IA Space Grant, Eagles).