The effect of ambient temperature on capillary vascular malformations.

Background: Following pulsed dye laser (PDL) treatment of capillary vascular malformations (CMs), the capillaries left behind tend to be smaller and deeper. The PDL is most effective against capillaries over 50 microm, suggesting that clearance of CM could be improved by inducing capillary vasodilation of the smaller remaining capillaries. However, there are reduced perivascular nerves within CMs, implying that autonomic innervation to these capillaries may be abnormal.

Objectives: To investigate whether CM capillaries will vasodilate in response to autonomic stimulation by raising ambient temperature.

Methods: Ten patients with untreated CMs and nine with previously laser-treated CMs were studied as ambient temperature was increased from 20 degrees C to 28 degrees C. The following measurements were taken at 2 degrees C intervals: skin blood flow (SBF); capillary diameter and depth; CM colour; and skin and core temperatures.

Results: All the subjects studied demonstrated superficial capillary vasodilation and increased SBF as the ambient temperature was raised from 20 degrees C to 28 degrees C. Mean+/-SEM capillary diameter increased from 66+/-7 microm to 110+/-13 microm (P<0.001) in the untreated group, compared with an increase from 28+/-5 microm to 70+/-14 microm (P<0.001) in the treated group. Mean+/-SEM SBF increased from 427.2+/-98.2 perfusion units (PU) to 580.9+/-92.7 PU (P<0.01) in the untreated group, compared with an increase from 201.3+/-28.4 PU to 458.1+/-53.7 PU (P<0.05) in the treated group.

Conclusions: Superficial capillary vasodilation within CM is achievable by raising ambient temperature, including in those patients resistant to PDL treatment, potentially allowing further clearance of these lesions.