VOLATILE ANESTHETICS REDUCE ADHESION OF BLOOD-PLATELETS UNDER LOW-FLOW CONDITIONS IN THE CORONARY SYSTEM OF ISOLATED GUINEA-PIG HEARTS

Background: inhibitory effects of volatile anaesthetics on platelet ag gregation have been demonstrated in several studies. However, the infl uence of volatile anaesthetics on intracoronary platelet adhesion has not been elucidated so far. Methods: Isolated hearts of guinea pigs we re perfused with buffer in the absence or presence of volatile anaesth etics (0.5 and 1 MAC) at constant coronary flow rates of 5 ml/min for 25 min, then 1 ml/min for 30 min and again 5 ml/min for 10 min. Before , during and after low-flow perfusion, a bolus of human platelets was applied into the coronary system. To simulate thrombogenic conditions, 0.3 U/ml human thrombin was infused during low-flow perfusion and rep erfusion. The number of platelets sequestered to the endothelium was c alculated from the difference between coronary in- and output of plate lets. The myocardial production of lactate and consumption of pyruvate and coronary perfusion pressure were also determined. Results: At a f low rate of 5 ml/min only about 3% of the applied platelets did not em erge from the coronary system, in any group. In contrast, 13.1+/-1.2% (mean+/-SEM) of infused platelets became adherent in low-flow perfusio n in the control group without anaesthetic. The adherence was reduced with each 1 MAC isoflurane (to 6.2+/-1.2%), sevoflurane (to 4.4+/-0.9% ) or halothane (to 3.2+/-1.5%) (each P<0.05 vs, control). Volatile ana esthetic, 0.5 MAC, did not inhibit platelet adhesion to a statisticall y significant extent in any case. Perfusion pressure and metabolic par ameters were not statistically different between the control and the h earts exposed to anaesthetics. Conclusion: Volatile anaesthetics in a concentration of 1 MAC can reduce the adhesion of platelets in the cor onary system under reduced flow conditions. This action does not arise from vasodilation or inhibition of ischaemic stress.