Improved small volume resuscitation from hemorrhagic shock with acellular hemoglobin

Abstract

Systemic and microvascular hemodynamic responses to hemorrhagic shock volume resuscitation with hypertonic saline (HTS) followed by infusion of polymerized bovine Hb (PBH) at different concentrations were studied in the hamster window chamber model, to determine role of plasma oxygen carrying capacity and vasoactivity during resuscitation. Moderate hemorrhagic shock was induced by arterial controlled bleeding of 50% of blood volume (BV), and a hypovolemic state was maintained for one hour. Volume was restituted by infusion of HTS (7.5% NaCl) 3.5% of BV of followed by 10% of BV of PBH at two different concentrations. Resuscitation was followed for 90 minutes and was carried out using 13 gPBH/dl [PBH13], PBH diluted to 4 gPBH/dl in albumin solution at matching colloidal osmotic pressure (COP) [PBH4], and albumin only solution at matching COP [PBH0]. Systemic parameters, microvascular hemodynamics and functional capillary density (FCD) were determined during hemorrhage, hypovolemic shock and resuscitation. PBH13 caused higher arterial pressure without reverting vasoconstriction and hypoperfusion. PBH4 and PBH0 had lower MAP and partially reverted vasoconstriction. Only treatment with PBH4 restored perfusion and FCD when compared to PBH13 and PBH0. Blood gas parameters and acid‐base balance recovered proportionally to microvascular perfusion. Tissue pO2 was significantly improved in the PBH4 group showing that limited restoration of oxygen carrying capacity is beneficial and compensates for the effects of vasoactivity characteristic of molecular hemoglobin solutions proposed as blood substitutes.