Jordan Loader1, Matthieu Roustit2, Frances Taylor3, Richard J MacIsaac4, Simon Stewart5, Christian Lorenzen6, Guillaume Walther7. 1. Centre of Research Excellence to Reduce Inequality in Heart Disease, Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia; School of Exercise Science, Australian Catholic University, Melbourne, Australia; Avignon University, LAPEC EA4278, F-84000 Avignon, France. Electronic address: jordan.loader@acu.edu.au. 2. Clinical Pharmacology, Grenoble University Hospital; and Inserm U1042, HP2, Université Grenoble Alpes, F-38000 Grenoble, France. 3. Centre of Research Excellence to Reduce Inequality in Heart Disease, Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia. 4. Department of Endocrinology and Diabetes, St Vincent's Hospital, Melbourne, Australia; The University of Melbourne, Melbourne, Australia. 5. Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia. 6. School of Exercise Science, Australian Catholic University, Melbourne, Australia. 7. School of Exercise Science, Australian Catholic University, Melbourne, Australia; Avignon University, LAPEC EA4278, F-84000 Avignon, France.
Abstract
AIM: Iontophoresis of vasoactive agents is commonly used to assess cutaneous microvascular reactivity. However, it is known that iontophoresis can be limited by confounding non-specific vasodilatory effects. Despite this, there is still no standardization of protocols or data expression. Therefore, this study evaluated commonly used protocols of iontophoresis by assessing each for evidence of non-specific vasodilatory effects and examined the reproducibility of those protocols that are free of non-specific responses. METHODS: Twelve healthy participants were administered doses of acetylcholine (ACh) 1-2% and sodium nitroprusside (SNP) 1%, diluted in sodium chloride 0.9% or deionized water, and insulin 100U/mL in a sterile diluent using iontophoresis coupled with laser speckle contrast imaging (LSCI). Increases in blood flux at a control electrode, containing the diluent only, indicated a non-specific response. Reproducibility of iontophoresis protocols that were free of non-specific vasodilatory effects were subsequently compared to that of post-occlusive reactive hyperemia (PORH), used as a standard, in 20 healthy participants. RESULTS: Iontophoresis of ACh or SNP in sodium choloride (0.02mA for 200 and 400s, respectively) and ACh in deionized water (0.1mA for 30s) mediated the least non-specific vasodilatory effects. Microvascular responses to insulin were mediated mainly by non-specific effects. Compared to PORH, the intraday and interday reproducibility for iontophoresis of ACh and SNP (0.02mA for 200 and 400s, respectively) with LSCI was weaker, but still deemed good to excellent when data was expressed, in perfusion units or cutaneous vascular conductance, as the absolute peak blood flux response to the vascular reactivity test or as the change in blood flux between peak and baseline values. CONCLUSION: This study provides updated recommendations for assessing cutaneous microvascular function with iontophoresis.
AIM: Iontophoresis of vasoactive agents is commonly used to assess cutaneous microvascular reactivity. However, it is known that iontophoresis can be limited by confounding non-specific vasodilatory effects. Despite this, there is still no standardization of protocols or data expression. Therefore, this study evaluated commonly used protocols of iontophoresis by assessing each for evidence of non-specific vasodilatory effects and examined the reproducibility of those protocols that are free of non-specific responses. METHODS: Twelve healthy participants were administered doses of acetylcholine (ACh) 1-2% and sodium nitroprusside (SNP) 1%, diluted in sodium chloride 0.9% or deionized water, and insulin 100U/mL in a sterile diluent using iontophoresis coupled with laser speckle contrast imaging (LSCI). Increases in blood flux at a control electrode, containing the diluent only, indicated a non-specific response. Reproducibility of iontophoresis protocols that were free of non-specific vasodilatory effects were subsequently compared to that of post-occlusive reactive hyperemia (PORH), used as a standard, in 20 healthy participants. RESULTS: Iontophoresis of ACh or SNP in sodium choloride (0.02mA for 200 and 400s, respectively) and ACh in deionized water (0.1mA for 30s) mediated the least non-specific vasodilatory effects. Microvascular responses to insulin were mediated mainly by non-specific effects. Compared to PORH, the intraday and interday reproducibility for iontophoresis of ACh and SNP (0.02mA for 200 and 400s, respectively) with LSCI was weaker, but still deemed good to excellent when data was expressed, in perfusion units or cutaneous vascular conductance, as the absolute peak blood flux response to the vascular reactivity test or as the change in blood flux between peak and baseline values. CONCLUSION: This study provides updated recommendations for assessing cutaneous microvascular function with iontophoresis.
Authors: François Guerrero; Kate Lambrechts; Qiong Wang; Aleksandra Mazur; Michael Théron; Alessandro Marroni Journal: Diving Hyperb Med Date: 2020-09-30 Impact factor: 0.887
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