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

Introduction: 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. Methods: 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. Results: 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). Conclusion: 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.