Effects on skeletal muscle oxygenation and capillary blood flow by adenosine-, sodium nitroprusside- and acetylcholine-induced hypotension.

Abstract

Adenosine (ADO)-induced hypotension during diethyl ether anesthesia has been shown to increase skeletal muscle oxygenation. Whether this beneficial effect of ADO hypotension is present also during another anesthetic technique was tested in the present study using ketamine-xylazine anesthesia, and its actions were compared with sodium nitroprusside (SNP) and acetylcholine (ACh) induced hypotension in rabbits. Local oxygen pressure and capillary blood flow were measured with a multiwire microelectrode which was placed on the surface of the left vastus medialis muscle. The experiments were performed in three groups, in which either ADO, SNP or ACh was infused into a central vein in a dose that produced a reduction of the mean arterial pressure by 20-25%, to approximately 60 mmHg. In the ADO group (60-170 micrograms kg-1 min-1) the tissue oxygen pressures increased by 23% while capillary blood flow decreased by 38%. During SNP administration (1-3 micrograms kg-1 min-1) the oxygen pressures decreased by 21% and an increase of 31% in capillary flows was seen. When ACh was infused (1-4 micrograms kg-1 min-1) the oxygen pressures decreased by 21% and, in parallel, capillary blood flow decreased by 50%. During hypotension no low tissue oxygen pressure values (< 1.5 kPa) were found in the ADO group, whereas they were present in both the SNP and ACh group. Compared to sodium nitroprusside and acetylcholine, adenosine appears to have an oxygen-sparing effect in the skeletal muscle during pharmacologically induced hypotension.