PERIPHERAL CIRCULATORY EFFECTS OF PUMP PERFUSION ON CAT SKELETAL-MUSCLE WITH AND WITHOUT PROSTACYCLIN

The present study analyses the peripheral circulatory effects oi pump perfusion on a sympathectomized cat skeletal muscle in terms of effect s on segmental vascular resistances (large-bore arterial vessels. arte rioles and veins), hydrostatic capillary pressure, capillary filtratio n coefficient transcapillary filtration and autoregulation of blood fl ow. The effect of prostacyclin during pump perfusion was analysed to e valuate whether it interferes with the pump-induced vascular alteratio ns, especially ii it reduces transcapillary filtration through its cap illary permeability decreasing effect. Pump perfusion initiates a mark ed vasodilation (from 17.3 to 10.1 PRU). an increase in hydrostatic ca pillary pressure. and a marked inhibition of myogenic reactivity and o f autoregulation of blood flow. There was a slow restoration of vascul ar tone reaching a steady-stare level somewhat below the autoperfusion value within 2 h. Pump perfusion did not change the capillary filtrat ion coefficient, indicating that the capillary permeability was not in creased. This implies that short-term pump-induced capillary leakage i s more an effect of increase in hydrostatic capillary pressure. perhap s in combination with increased number of open capillaries, than oi an increase in capillary permeability. Prostacyclin decreased capillary permeability by at least 22% but simultaneously increased hydrostatic capillary pressure. resulting in an unchanged filtration compared with the situation just after the starting of the pump, The results obtain ed show that experiments using pump perfusion should be interpreted wi th care due to the interference with normal peripheral vascular contro l. The results give reasonable explanations of the lowered blood press ure and transcapillary fluid loss during the clinical use of a heart-l ung machine.