Improvements in rheologic properties of blood by fluid resuscitation after burn injury in rats.

Severe burn injury impairs tissue perfusion both by adversely altering the rheologic properties of blood and by decreasing circulating blood volume. Although resuscitation is known to improve perfusion by increasing whole blood volume, it is possible that it may also improve blood flow. To assess these latter effects of resuscitation after burn injury, we studied several determinants of blood flow. Burned animals were resuscitated with 20 ml of lactated Ringer's solution given intraperitoneally. This fluid resuscitation significantly improved the hemoconcentration that was produced by burn injury (p less than 0.05). Burn injury caused an increase in free plasma hemoglobin (p less than 0.05). Fluid resuscitation after injury reduced free plasma hemoglobin compared with that of the burned animals (p less than 0.05), although it still remained higher than free plasma hemoglobin in unburned controls (p less than 0.05). Increased whole blood viscosity and increased osmotic fragility, which were caused by burn injury, were also corrected by fluid resuscitation. Finally, the decrease in red blood cell membrane deformability that is associated with burn injury was improved by resuscitation, although it never completely returned to normal. These results demonstrate beneficial effects of fluid resuscitation on rheologic properties of blood after burn injury. Restoration of blood flow to tissue by resuscitation after burn injury may be due to improved blood rheology as well as to intravascular volume loading.