Epinephrine iontophoresis attenuates changes in skin blood flow and abolishes cutaneous contamination of near-infrared diffuse correlation spectroscopy estimations of muscle perfusion.

Near-infrared diffuse correlation spectroscopy (NIR-DCS) is an optical imaging technique for measuring relative changes in skeletal muscle microvascular perfusion (i.e., fold change above baseline) during reactive hyperemia testing and exercise and is reported as a blood flow index (BFI). Although it is generally accepted that changes in BFI are primarily driven by changes in muscle perfusion, it is well known that large, hyperthermia-induced changes in cutaneous blood flow can uncouple this relationship. What remains unknown, is how much of an impact that changes in cutaneous perfusion have on NIR-DCS BFI and estimates of skeletal muscle perfusion under thermoneutral conditions, where changes in cutaneous blood flow are assumed to be relatively low. We therefore used epinephrine iontophoresis to pharmacologically block changes in cutaneous perfusion throughout a battery of experimental procedures. The data show that 1) epinephrine iontophoresis attenuates changes in cutaneous perfusion for up to 4-h posttreatment, even in the face of significant neural and local stimuli, 2) under thermoneutral conditions, cutaneous perfusion does not significantly impact NIR-DCS BFI during reactive hyperemia testing or moderate-intensity exercise, and 3) during passive whole body heat stress, when cutaneous vasodilation is pronounced, epinephrine iontophoresis preserves NIR-DCS measures of skeletal muscle BFI during moderate-intensity exercise. Collectively, these data suggest that cutaneous perfusion is unlikely to have a major impact on NIR-DCS estimates of skeletal muscle BFI under thermoneutral conditions, but that epinephrine iontophoresis can be used to abolish cutaneous contamination of the NIR-DCS BFI signal during studies where skin blood flow may be elevated but skeletal muscle perfusion is of specific interest.

Impact of cutaneous blood flow on NIR-DCS measures of skeletal muscle blood flow index.

Near-infrared diffuse correlation spectroscopy (NIR-DCS) is an optical technique for estimating relative changes in skeletal muscle perfusion during exercise but may be affected by changes in cutaneous blood flow, as photons emitted by the laser must first pass through the skin. Accordingly, the purpose of this investigation was to examine how increased cutaneous blood flow affects NIR-DCS blood flow index (BFI) at rest and during exercise using a passive whole body heating protocol that increases cutaneous, but not skeletal muscle, perfusion in the uncovered limb. BFI and cutaneous perfusion (laser-Doppler flowmetry) were assessed in 15 healthy young subjects before (e.g., rest) and during 5 min of moderate-intensity handgrip exercise in normothermic conditions and after cutaneous blood flow was elevated via whole body heating. Hyperthermia significantly increased both cutaneous perfusion (∼7.3-fold; P ≤ 0.001) and NIR-DCS BFI (∼4.5-fold; P ≤ 0.001). Although relative BFI (i.e., fold-change above baseline) exhibited a typical exponential increase in muscle perfusion during normothermic exercise (2.81 ± 0.95), there was almost no change in BFI during hyperthermic exercise (1.43 ± 0.44). A subset of eight subjects were subsequently treated with intradermal injection of botulinum toxin-A (Botox) to block heating-induced elevations in cutaneous blood flow, which 1) nearly abolished the hyperthermia-induced increase in BFI and 2) restored BFI kinetics during hyperthermic exercise to values that were not different from normothermic exercise (P = 0.091). Collectively, our results demonstrate that cutaneous blood flow can have a substantial, detrimental impact on NIR-DCS estimates of skeletal muscle perfusion and highlight the need for technical and/or pharmacological advancements to overcome this issue moving forward.NEW & NOTEWORTHY We used passive whole body heat stress, in combination with local intradermal botulinum toxin type A treatment, to experimentally manipulate cutaneous blood flow and investigate its impact on NIR-DCS measures of skeletal muscle BFI at rest and during exercise. Collectively, the results show that cutaneous blood flow, which was augmented in response to passive whole body heat stress, markedly affects NIR-DCS-derived BFI, such that the BFI signal becomes dominated by changes in cutaneous red blood cell flux.

Cutaneous leishmaniasis in a 65-year-old North Texas male, treated with cryotherapy: A case report.

We report a case of a 65-year-old male seen in a North Texas dermatology clinic with three erythematous nodules possessing central ulceration and scaling on the left lateral shoulder, present for months. Head, ears, lips, oral mucosa, and other body surfaces did not reveal similar lesions, and review of systems was negative. Shave biopsy was performed and histopathological findings demonstrated granulomatous inflammation in the dermis and parasitized histiocytes containing peripherally located amastigotes. Leishmaniasis was diagnosed and patient was educated on the disease while communication with the Centers for Disease Control and Prevention was initiated. The patient declined systemic medications from infectious disease specialists and, 3 weeks later, returned for follow-up treatment with cryotherapy.