Depressed reflex vasomotor control of the burn wound

Total leg blood flow was measured by venous occlusion plethysmography in five normals and 14 burned patients before and after 30 min of external heating. Leg surface temperatures were held constant, but rectal temperatures increased on the average of 0.4 to 0.5 degrees C in all subjects following this heat load. Leg blood flow increased by 56.0% in the controls, 63.2% in five patients with essentially no leg burn (mean burn size = 1.5% leg surface), and 9.6% in nine patients with major leg injuries (mean burn size 55% leg surface). Failure of reflex vasodilatation in the burned leg was evident up to 107 days postinjury even when the wound was well-healed. All subjects sweated freely from the unburned skin. In two patients, where arm and leg blood flows were measured simultaneously, flow to the uninjured arm increased while that to the injured leg remained unchanged. This lack of reflex vasodilatation in the burned limbs suggests either that wound vessels are denervated or that they are so dilated in the basal state that further dilatation is limited. The bulk of this and other data would support the denervation concept. This physical or chemical denervation could occur at the time of injury, be localised to the area of the wound, and result in loss of both neurogenic vasoconstrictor tone and active reflex vasodilatation.