Arterio-Venous Anastomoses and Thermoregulation (Arterio-Veneuze Anastomosen en Thermoregulatie)

Abstract : In a cold environment human heat loss is reduced by peripheral vasoconstriction, counter-current heat exchange and a change of peripheral circulation pattern. However, these mechanisms go at the expense of the tissue temperature in the extremities. The cooling can be so pronounced that local cold injuries occur. Cold induced vasodilation (CIVD) may be regarded as an effective protection against local cold injury. The underlying mechanism is often associated with the presence of arterio-venous anastomoses (AVA). Rhythmic relaxation and contraction of the strong muscular wall of the AVA is often supposed to cause the hunting response in CIVD. The contraction phase is probably caused by stimulation of the alpha-adrenoceptors in the smooth muscle wall. Relaxation may be caused by a nervous blockade of the sympathetic system. There is no scientific evidence for humeral mediators. The influence of the body temperature on the vasomotor tone of the AVA remains to be investigated. The locations of AVA and the sites where CIVD occurs are not in perfect correspondence and also this point needs further research.