Abstract 186: Remote Limb Ischemic Preconditioning Improves Short and Long Term Survival and Maintains Intravascular Blood Volume During Resuscitation of Hemorrhagic Shock

Abstract

Background: We further examined the protective effects of experimental bilateral lower limb remote ischemic preconditioning (RIPC) in rats undergoing experimental hemorrhagic shock. Methods: Sprague Dawley rats (both genders) were randomized into RIPC (n= 26) or control group (n= 27), and anesthetized with intraperitoneal ketamine/xylazine. RIPC was induced by 4 cycles of inflating small bilateral pressure cuffs to 200 mmHg around the femoral arteries for 5 minutes, followed by 5 minute deflation of the cuffs. Hemorrhagic shock was induced by withdrawing blood from the carotid artery. Target mean blood pressure of 30 mmHg was maintained for 30 minutes followed by reinfusion of shed blood within the next 30 min. Rats remained anesthetized for another 30 min before recovery; endpoints were survival at 72 hours and 6 weeks. Results: The % of estimated total blood volume withdrawn to maintain a level of 30 mmHg was similar in the RIPC group (41.7 ± 1.0 %) and control group (41.9 ± 1.0 %). Recovery of blood pressure during the early resuscitation phase was significantly improved in the RIPC group. The diastolic internal dimension of the left ventricle (echocardiogram), which indicates circulating intravascular blood volume, was significantly larger in the RIPC group at 1 hour after initiation of shed blood reinfusion (5.8 ± 0.1 mm) compared to 5.4 ± 0.1mm in the control group (p=0.04). Left ventricular fractional shortening was comparable between RIPC (50.9 ± 1.9 %) and control group (49.6 ± 1.8 %; p=0.64) at 1 hour after initiation of resuscitation. At 48 hours after shock, BUN was within normal range in the RIPC group (17.3 ± 1.2 mg/dl); but elevated in the control group (22.0 ± 1.7 mg/dl). At 72 hours after hemorrhagic shock injury, 6 of 27 (22.2 %) rats in the control group and 13 of 26 (50 %, p = 0.047) rats in the RIPC group survived. At 6 weeks, 5 of 27 (18.5 %) rats in the control group and 13 of 26 (50 %; p = 0.021) rats in the RIPC group survived. RIPC significantly increased survival rate at both 72 hours and 6 weeks. Conclusions: RIPC improved recovery of blood pressure and maintained more circulating intravascular blood volume in the early phase of resuscitation, improved BUN, and markedly and significantly improved short and long term survival in rats subjected to hemorrhagic shock.