Drug- and temperature-induced changes in peripheral circulation measured by laser-Doppler flowmetry and digital-pulse plethysmography.

We measured the effects of a new transdermal nitroglycerin patch (25 mg, 10 cm2) applied for 24 h, norphenephrine (6 mg), prazosin (1 mg) as well as local heat and cold provocation on blood pressure, heart rate, skin blood flow (measured by laser-Doppler flowmetry, L-D) and peripheral arterial resistance (assessed by digital pulse plethysmography, D-P) in 15 healthy volunteers (aged 21-31 years). Heat provocation induced a three-fold increase in skin blood flow in the hand (p less than 0.001) and cold provocation a decrease in flow (p less than 0.05) of about 20%. Forehead skin blood flow did not change. Peripheral arterial resistance showed less consistent changes during the provocation tests. Prazosin increased the forehead skin blood flow (p less than 0.01) and decreased peripheral arterial resistance, while norphenephrine showed an opposite effect. Transdermal nitroglycerin induced an increase of 25% in forehead skin blood flow (p less than 0.05) which persisted for 24 h and a decrease in peripheral arterial resistance (p less than 0.02), but this effect was evident up to 8 h only. We conclude that (1) local heat and cold provocation mainly affected skin blood flow, (2) vasodilative and vasoconstrictive drugs showed marked changes in peripheral arterial resistance, but at different points in time from subject to subject, and (3) transdermal nitroglycerin patches induced haemodynamic changes persisting for up to 8-24 h.