Is Vasodilation to Local Skin Heating Altered in Patients with Cystic Fibrosis?

Abstract

Local heating produces a bimodal rise in skin blood flow, where blood flow increases to an initial peak (axon-reflex) then decreases to a nadir before rising again to a sustained plateau. These responses are thought to include specific neuropeptides along with NO. Altered neuropeptide content in the cutaneous nerves of patients with Cystic Fibrosis (CF) may change these responses. PURPOSE: To determine the contribution of NO to vasodilation with local skin heating in patients with CF vs. controls. METHODS: In 4 CF patients and 4 controls, two microdialysis fibers were placed in the forearm skin of the non-dominant arm. Skin blood flow was monitored over each site with laser-Doppler flowmetry as skin temperature was increased 0.5° C every 5 sec to 42° C, then maintained at 42°C for ∼45 min. Lactated Ringer's was infused continuously in a control site and 10 mM L-NAME was infused continuously through an experimental site. Cutaneous vascular conductance (CVC) was calculated as red blood cell flux/mean arterial pressure and scaled as percent maximal CVC obtained during 25mM sodium nitroprusside infusion at each skin site. RESULTS: The initial peak (75±3 vs. 76±2%), nadir (60±9% vs. 53±7%), and plateau (88±7 vs. 81±6 %) skin blood flow responses at the control skin sites were similar in CF patients and control subjects. NO synthase inhibition blunted the initial peak more in control subjects than CF patients (22±5 vs. 11 ±6%). The impact of NO synthase inhibition was similar on the plateau phase in both groups (49±5 vs. 44±4%). CONCLUSIONS: The contribution of NO to the initial peak vasodilation with local skin heating may be fundamentally different in patients with CF.