Remote Ischemic Preconditioning Improves Tissue Oxygenation in a Porcine Model of Controlled Hemorrhage Without Fluid Resuscitation

Abstract

Purpose Remote Ischemic preconditioning (RIPC) involves deliberate, brief interruptions of blood flow to increase the tolerance of distant critical organs to ischemia. This study tests the effects of limb RIPC in a porcine model of controlled hemorrhage without replacement therapy simulating an extreme field situation of delayed evacuation to definitive care.Methods Twenty-eight pigs (47±6kg) were assigned to: (1) control, no procedure (n=7); (2) HS=hemorrhagic shock (n=13); and (3) RIPC+HS=remote ischemic preconditioning followed by hemorrhage (n=8). The animals were observed for 7 hours after bleeding without fluid replacement. Results Survival rate between animals that underwent RIPC before bleeding and those bled without prior RIPC were similar (HS, 6 of 13[46%]-vs-RIPC+HS, 4 of 8[50%], p=0.86 by Chi-square). Animals with prior RIPC had faster recovery of mean arterial pressure and developed higher heart rates without complications. Those with RIPC had less decrease in pH and bicarbonate, and the increase in lactate began later. Global oxygen delivery was higher, and tissue oxygen extraction ratio lower, in animals bled after RIPC. Conclusions These improvements after RIPC in hemodynamic and metabolic status provide essential substrates for improved cellular response after hemorrhage and reduction of the likelihood of potentially catastrophic consequences of the accompanying ischemia.