Local heating-induced cutaneous vasodilation in reinnervated and noninnervated deep inferior epigastric perforator flaps.

Abstract

Cutaneous vascular reactivity to local heating in free flaps has not been characterized. We aimed to assess local heating-induced cutaneous vasodilation in reinnervated and noninnervated deep inferior epigastric perforator (DIEP) flaps. We conducted a cross-sectional study of 21 female patients with an uncomplicated unilateral delayed DIEP breast reconstruction at least 2 years after surgery. DIEP flaps and contralateral breasts were subjected to direct local heating, and skin blood flow was assessed using laser-Doppler flowmetry. To evaluate sensory-nerve-fiber function, touch perception thresholds were assessed using a 20-piece Touch-test™ Sensory Evaluator, and cutaneous warm detection and heat pain thresholds were measured using a TSA-II device. Of the participants, 10 had a reinnervated DIEP flap with a single coapted nerve (mean flap weight, 610 ± 296 g) and 11 had a noninnervated DIEP flap (mean flap weight, 613 ± 169 g). Mean age was 58 ± 11 years, mean follow-up time was 5 ± 1 years, and mean BMI was 24 ± 3 kg/m² . DIEP flaps exhibited significantly weaker cutaneous vasodilation in response to local heating than contralateral breasts (median peak skin blood flow, 59 [25th-75th percentile, 36-71] a.u. for DIEP flaps versus 94 [74-141] a.u. for contralateral breasts; p < .001). The magnitude of the response was similar between reinnervated and noninnervated flaps (median peak skin blood flow, 55 [25th-75th percentile, 39-68] a.u. for reinnervated DIEP flaps versus 66 [36-77] a.u. for noninnervated DIEP flaps; p = .75). Of participants with reinnervated DIEP flaps, 90% perceived heat pain below the 50°C safety threshold, as compared to 36% of participants with noninnervated DIEP flaps (two-tailed p = .02). Our results suggest that free flap transfer causes longstanding impairment, yet not complete abolition, of both the sensory nerve-mediated and nitric oxide-dependent local heating-induced cutaneous vasodilatory systems. We found no statistical evidence that flap reinnervation improves the ability to raise skin blood flow in response to local heating.