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The effect of severe local cooling of the finger on the vasomotor activity of the arteriovenous anastomoses (AVAs) and other finger vessels was examined. Before cooling, blood velocity in both fingers showed the familiar large, closely correlated fluctuations caused by synchronous opening and closing of the AVAs. Results showed that these velocity fluctuations continued to be positively correlated with arterial blood velocity fluctuations in the control finger during cold-induced vasodilation.

The effect of local cooling from 35 to 19 degrees C on acral skin circulation in thermoneutral subjects was studied. Arterial blood velocity of the third finger in both hands were simultaneously recorded using ultrasound-Doppler systems. As expected, the constriction of the arteriovenous anastomoses (AVAs) caused large blood velocity fluctuations. From 35 to about 21.5 degrees C, the fluctuations were almost unchanged. However, at local temperatures below 21.5 degrees C, the velocities did not fluctuate which suggest sustained local closure of the AVAs.