Abstract 187: Effects of Anesthetic Agents on the Hemodynamic Stabilization and Long Term Survival in an Experimental Model of Hemorrhagic Shock

Abstract

Background: We investigated the cardiovascular responses to acute bleeding and shed blood restoration under different anesthetic agents, and their effects on long-term survival rate after hemorrhagic shock in rats, after our initial pilot study suggested differences between anesthetics. Methods: Sprague Dawley rats (both genders) were randomized to receive either intraperitoneal ketamine/xylazine (K/X, 90 mg/kg and 10 mg/kg; n=12), or isoflurane (5% isoflurane induction and 2% maintenance in room air; n=12) for anesthesia. Blood was withdrawn from the carotid artery to maintain mean arterial blood pressure (MBP) at 30 mm Hg for one hour, followed by 30 min of resuscitation with shed blood. Rats remained anesthetized for another 30 min before they were allowed to recovery and survive for 6 weeks. Hemodynamics were monitored during the surgical procedure. Results: During the shock phase, the total withdrawn blood volume (expressed as % of estimated total blood volume) to maintain MBP at 30 mmHg was significantly higher in the isoflurane group (51 ± 1.5 %) compared to the K/X group (45.3 ± 1.8 %; p=0.023). The diastolic internal dimension of the left ventricle, which indicated circulating intravascular blood volume, was significantly larger in the isoflurane group at the end of 1 hour of the shock phase (4.5 ± 0.2 mm compared to 3.5 ± 0.2 mm in K/X group; p=0.0003) and at 1 hour after initiation of shed blood reinfusion (6.3 ± 0.2 mm compared to 5.3 ± 0.3 in K/X group; p=0.014). Recovery of blood pressure during the resuscitation phase was significantly improved in the isoflurane group compared to the K/X group. The survival rate at 6 weeks was 1 of 12 (8.3%) in rats receiving K/X and 10 of 12 (83.3%) in rats receiving isoflurane (p < 0.001). Histology demonstrated brain infarction in the 1 surviving rat receiving K/X; no brain infarction in the 10 surviving rats that received isoflurane at 6 weeks. No infarction was detected in heart, lung, liver or kidneys in all surviving rats. Conclusions: These results suggest that isoflurane stabilizes the cardiovascular response to acute blood lose and benefits the perfusion of tissue, which resulted in significantly higher long term survival rate and improved blood pressure response to resuscitation, without end-organ infarction.