Abstract 12073: Identification of Critical Level of Blood Volume Reduction in a Swine Model of Hemorrhagic Shock
Background: Acute reduction in intravascular volume is a life-threatening emergency associated with high risk of initial death or subsequent organ dysfunction. In a swine model of hemorrhagic shock (HS) we sought to identify the critical level of intravascular blood volume reduction at which resuscitability is compromised.
Methods: In one series, 50% of the blood volume was removed over 30 minutes (Series-50%). In another series, an additional 15% was removed over an additional 30 minutes for a total of 65% reduction of blood volume (Series-65%). At 90 minutes of HS, resuscitation was attempted by delivering 0.9% NaCl over 4 hours (three times the amount of blood removed) followed by reinfusion of the blood removed over 1 hour.
Results: Intensification of HS severity by increasing the amount of blood removed from 50% to 65% of the blood volume profoundly reduced resuscitability from 83% to 25% (p=0.006 by Gehan-Breslow test). Intensification of HS was accompanied by further reduction in cardiac index (CI) and O2 delivery (iDO2) reaching an O2 extraction (VO2/DO2) of 71% prompting generation of lactic acid with increases in the PCO2 gradient between mixed venous and aortic blood [P(V-Ao)CO2]; all indicative that 71% was the maximal VO2/DO2 and that the anaerobic threshold was exceeded (Table).
Conclusions: In this swine model, further reduction in blood volume from 50% to 65% exhausted adaptive mechanisms needed to maintain aerobic metabolism precipitously compromising resuscitability. The current model with high lethality may be useful to examine survival and metabolic effects of novel therapeutic interventions.
- © 2012 by American Heart Association, Inc.