Platelet function and anesthetics in cardiac surgery: An in vitro and ex vivo study

We studied the effects of the anesthetics commonly used in cardiac surgery on platelet function. Fentanyl, droperidol, succinylcholine, pancuronium, t hiopental, and diazepam at therapeutic concentrations were tested for their in vitro effects on the expression of platelet membrane glycoproteins Ib a nd IIbIIIa (GpIb, GpIIb-IIIa) and of P-selectin in anticoagulated whole blo od by flow cytometry. The expression of P-selectin was determined under bas al conditions, after the incubation of blood with adenosine diphosphate (AD P) 10 mu mol/L, and the stable prostaglandin endoperoxide analog U46619 1 m u mol/L. No drug affected the expression of P-selectin in unstimulated and ADP- or US6619-stimulated platelets, with the exception of thiopental, whic h markedly decreased the U46619-induced expression of P-selectin. Thiopenta l concentration-dependently inhibited U46619-induced and ADP-induced platel et aggregation, with effects on U46619-induced aggregation at therapeutic c oncentrations. To assess au vivo effects, the same platelet markers were al so assessed in blood obtained from 10 patients undergoing elective coronary surgery, Compared with basal values, platelet response to U46619 was signi ficantly reduced just after the administration of anesthetic drugs, and the effect persisted for 48 h after surgery. Our study suggests that, at thera peutic concentrations, thiopental inhibits U46619-induced platelet activati on bo th in vitro and ex vivo. The mechanisms responsible of this effect, t ogether with its clinical significance, require further investigation Impli cations: Thiopental inhibited prostaglandin-induced platelet activation at therapeutic concentrations both in vitro and ex vivo in cardiac surgical pa tients whereas adenosine diphosphate-induced activation was affected only a t supratherapeutic drug concentrations. Thus, administration of sodium thio pental may contribute to the in vivo impairment of platelet function in pat ients undergoing elective cardiac surgery.