Actions of some vasodilators on isolated human hand veins.

Vasospasm is a well recognized complication during microvascular surgery of the hand. In the search for new spasmolytic drug therapies, the effects of papaverine, nitroprusside, nimodipine and lidocaine on isolated human hand veins contracted by several postulated mediators of vasospasm were examined. Mechanical activity was recorded isometrically in ring segments of the vessels. Potassium ions, noradrenaline (NA), 5-hydroxytryptamine (5-HT) and prostaglandin F2 alpha (PGF2 alpha) all produced strong contractions that were highly dependent on the presence of extracellular Ca2+. Papaverine acted as a nonselective vasodilator, as it produced an almost identical inhibition of contractile responses to all examined stimulants. Nitroprusside inhibited contractions induced by agonists more than those evoked by K+, whereas the opposite was found for nimodipine. Nitroprusside also seemed to display a certain degree of selectivity among the agonist-induced responses (NA greater than PGF2 alpha greater than 5-HT). Lidocaine increased the contractile response to K+ and at high concentrations (greater than 10(-5) M) produced a contraction per se. The clinical efficacy of lidocaine as a vasodilator after topical application therefore seems to reflect an inhibitory action on vasoconstrictor nerves. Papaverine, nitroprusside, nimodipine and lidocaine differ considerably in their profiles of action and therefore deserve to be further evaluated in the treatment of vasospasm during microvascular surgery.