RESUMO
We studied the vasodilatory effects of fentanyl, remifentanil and sufentanil on the human saphenous vein strips at 37, 32 and 28 degrees C. Fentanyl produced concentration-dependent relaxation of human saphenous vein strips precontracted with 5-hydroxytryptamine (5-HT) at every temperature studied. Compared with vein strips at 37 degrees C, relaxant responses to each one concentration of fentanyl were significantly reduced at 32 and 28 degrees C. Remifentanil relaxed vein strips in a concentration-dependent way and the relaxation for all concentrations were significantly greater at 32 and 28 degrees C compared with 37 degrees C. Sufentanil produced concentration-dependent relaxation in saphenous vein strips precontracted with 5-HT. These relaxant responses were similar at 32 degrees C compared with 37 degrees C. When bath temperature was lowered from 37 to 28 degrees C, the relaxant responses to sufentanil were significantly reduced. In summary, the present study suggests that cooling reduces the relaxation caused by fentanyl and sufentanil on human saphenous veins but augments the relaxation with remifentanil. The augmented vasodilatory effect of remifentanil with cooling may be useful on systemic vascular resistance and organ preservation under hypothermic conditions like cardiopulmonary bypass surgery.
