Response of fingertip circulation to local warming in the injured hand--a study using laser Doppler flowmetry

A laser Doppler flowmeter was used to assess the fingertip circulation serially in 41 patients with various hand injuries. The "flux value" measures the flow of red cells across the site of assessment and the "fluctuation" represents the pulsatile peak-trough difference in flux value with each cardiac contraction. Local temperature at the fingertip was raised stepwise by a special heater-thermostat from 36 to 44 degrees C. Compared to the normal hand both the flux value and fluctuation in the injured hand are smaller at lower temperatures. The differences narrow down at higher temperatures and the trend reverses above 42 degrees C and remains so on cooling. This may represent abnormal sympathetic tone in the injured hand.