Influence of pentobarbital, propofol and ketamine on skeletal muscle capillary perfusion during hemorrhage: a comparative study in the rabbit.

Abstract

Anesthetics affect tissue blood flow, which is of importance especially in situations of inadequate perfusion, as in hemorrhage. The present study compared the effect of three commonly used anesthetic agents on skeletal muscle capillary and regional blood flow during and after recovery from hemorrhage. Three groups of rabbits were anesthetized randomly with either pentobarbital, propofol or ketamine, chosen such that the anesthetic level, blood pressure and withdrawn blood volume were comparable in all groups. Capillary blood flow was measured using a local hydrogen clearance technique with a multi-wire microelectrode, placed on the left vastus medialis muscle surface, and the contralateral site served for regional microcirculatory blood flow measurements using laser-Doppler flowmetry. Hemorrhage was induced by withdrawal of blood to a mean arterial pressure of 40 mm Hg and monitoring was continued during the subsequent spontaneous recovery period of 120 min. Both capillary and regional blood flow decreased significantly during hemorrhage in all groups. The flow values in the pentobarbital group were given a mean value of 100% and the other two groups were compared with this. Local hydrogen clearance flow decreased from a relative baseline level of 100 to 64% during hemorrhage with pentobarbital, from 87 to 43% with propofol and from 146 to 70% with ketamine. Laser-Doppler flowmetry flow decreased from relative baseline levels of 100, 96 and 139%, to 71, 77 and 103%, respectively, during hemorrhage, whereas the percentage of zero capillary flow values increased from 4 to 34, 19 to 50 and 5 to 27% in the three groups, respectively. The results of the present study indicate that capillary perfusion is best maintained in the ketamine group followed by pentobarbital and propofol last. Furthermore, the flow distribution shapes for each anesthetic indicate a more pronounced deregulation of capillary blood flow in the propofol group than in the others, even at baseline.