Increase plasma viscosity sustains microcirculation after resuscitation from hemorrhagic shock and continuous bleeding

Resuscitation from hemorrhagic shock (50% of blood volume, BV) followed by continuous bleeding (20% of BV per hour, over the entire observation time, 90 min) was studied in the unanesthetized hamster chamber window model. Blood losses equaled 100% of total BV. A single volume infusion (resuscitation) was performed 60 min after hemorrhage using 25% of the BV with 10% hydroxyethyl starch (HES 200, group HES4), or a mixture of HES 200 with 0.3% or 0.6% (w/v) alginate (groups HES7 and HES10, respectively) leading to solutions with a uniform colloidal oncotic pressure (84-87 mmHg) and viscosities ranging from 3.8 to 9.8 cp. Results showed all solutions to be similar immediately after resuscitation (10-15 min) and diverged after this initial period. The viscosity-enhanced solutions showed improved and longer-lasting effects (90 min) relative to the conventional low viscosity, in terms of sustained arterial blood pressure, microvascular flow, capillary perfusion, and laboratory parameters. All microvascular parameters 90 min after resuscitation with low viscosity fell back to the shock level. Improved recovery obtained with a hyperviscous plasma expander was related to microcirculation shear stress preservation, leading to improve blood flow by lowering peripheral vascular resistance when compared with low viscosity resuscitation. These findings suggest the possibility of using hyperviscous plasma expanders to prolong the period for initial treatment of blood losses and definitive institution therapy.