Effect of cutaneous burn injury and resuscitation on the cerebral circulation in an ovine model.

The aim of our study was to evaluate the effects of a large cutaneous burn injury on the cerebral circulation. Anesthetized sheep (n = 8) were prepared with vascular catheters, a urinary catheter and a Richmond bolt for intracranial pressure monitoring. A scald injury was inflicted on 70 percent of total body surface area with hot water. Resuscitation was started 30 min after scald with Ringer's lactate to restore and maintain baseline oxygen delivery. Resuscitation maintained blood pressure, cardiac output and urine output at normal levels. Brain blood flow was measured with colored microspheres. During resuscitation intracranial pressure rose slowly from 10.6 +/- 1.5 to 17.0 +/- 4.0 mmHg (P < 0.05) and cerebral perfusion pressure was reduced from 86.4 +/- 6.8 to 64.1 +/- 2.8 mmHg (P < 0.05). During early resuscitation cerebrovascular resistance declined to maintain brain blood flow and oxygen delivery at baseline or better. After 6 h, mean cerebrovascular resistance was inappropriately increased during a period of reduced cerebral perfusion pressure which resulted in brain blood flow reductions of half the baseline levels. These data suggest that autoregulation maintains brain blood flow immediately after burn shock and early resuscitation, but the autoregulation may be less effective as burn resuscitation proceeds.