Remote ischemic preconditioning improves tissue oxygenation in a porcine model of controlled hemorrhage without fluid resuscitation

Abstract

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. Twenty-eight pigs (47\u2009±\u20096 kg) were assigned to: (1) control, no procedure (n\u2009=\u20097); (2) HS\u2009=\u2009hemorrhagic shock (n\u2009=\u200913); and (3) RIPC\u2009+\u2009HS\u2009=\u2009remote ischemic preconditioning followed by hemorrhage (n\u2009=\u20098). The animals were observed for 7 h after bleeding without fluid replacement. Survival rate between animals of the RIPC\u2009+\u2009HS group and those of the HS group were similar (HS, 6 of 13[46%]-vs-RIPC\u2009+\u2009HS, 4 of 8[50%], p\u2009=\u20090.86 by Chi-square). Animals of the RIPC\u2009+\u2009HS group had faster recovery of mean arterial pressure and developed higher heart rates without complications. They also 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 RIPC\u2009+\u2009HS animals. 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.