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V. A. Diaz, R. Schonberger, W. Worden, K. Menn, R. Stout, K. Shelley, D. Silverman, R. Adelman; Laser Doppler Flowmetry Study Assessing Microvascular Function in Patients With Proliferative Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2089. doi: https://doi.org/.
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Assessments of microvascular function with non-iontophoretic acetylcholine and nitroglycerin patches have demonstrated a robust vasodilatory response in healthy volunteers. The present investigation tests whether significant local vasodilation is induced at comparable dosages on a cohort of subjects with proliferative diabetic retinopathy.
After IRB approval, 10 patients presenting for routine visits to a retina clinic were recruited for LDF measurements of forehead perfusion at sites of transdermal application of acetycholine, nitroglycerin, and placebo.Laser Doppler probes were placed as well as to define the area (59.4-mm2) for drug application. Heart rate was monitored continuously, and intermittent blood pressure were obtained. All of the subjects had proliferative diabetic retinopathy by prior fluorescein angiography. Each probe remained in place for up to 20 minutes.The primary endpoint was the change in LDF voltage after transdermal application of each active drug versus placebo in the study population. Secondary endpoints were also assessed. First, the effects of the single dose of acetylcholine was compared to the single dose of nitroglycerin in the subjects. Second, the response in the 10 diabetic patients was compared to previously published data on the response of younger, healthy controls to the same challenges. These data were compared using the Mann-Whitney U Test.
Readings increased by 156% (91%-221%) and 116% (79%-153%), respectively, at the acetylcholine and nitroglycerin sites, vs. 21% (CI 4-37%) at the placebo site (p=0.005 for placebo versus each active site). Heart rate and blood pressure did not change significantly. Diabetics’ responses at both active sites were significantly impaired relative to prior published data on a group of younger healthy controls using the same doses of drug (p<0.001 and p=0.009, respectively.
Transdermal non-iontophoretic delivery of acetylcholine and nitroglycerin induces significant local vasodilatory responses in a population with known microvascular disease. The means of transdermal delivery and testing described previously may be implemented successfully on patients with advanced disease in the course of a typical clinic visit. This minimally invasive method to interrogate the microvasculature offers a practical way to assess microvascular response in a variety of disorders and the microcirculatory changes induced by therapeutic interventions.
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