Microvascular Autoregulation in Skeletal Muscle Using Near-Infrared Spectroscopy and Derivation of Optimal Mean Arterial Pressure in the ICU: Pilot Study and Comparison With Cerebral Near-Infrared Spectroscopy.

Microvascular autoregulation (MA) maintains adequate tissue perfusion over a range of arterial blood pressure (ABP) and is frequently impaired in critical illness. MA has been studied in the brain to derive personalized hemodynamic targets after brain injury. The ability to measure MA in other organs is not known, which may inform individualized management during shock. This study determines the feasibility of measuring MA in skeletal muscle using near-infrared spectroscopy (NIRS) as a marker of tissue perfusion, the derivation of optimal mean arterial pressure (MAPopt), and comparison with indices from the brain. Prospective observational study. Medical and surgical ICU in a tertiary academic hospital. Adult critically ill patients requiring vasoactive support on the first day of ICU admission. Fifteen critically ill patients were enrolled. NIRS was applied simultaneously to skeletal muscle (brachioradialis) and brain (frontal cortex) while ABP was measured continuously via invasive catheter. MA correlation indices were calculated between ABP and NIRS from skeletal muscle total hemoglobin (MVx), muscle tissue saturation index (MOx), brain total hemoglobin (THx), and brain tissue saturation index (COx). Curve fitting algorithms derive the MAP with the lowest correlation index value, which is the MAPopt. MAPopt values were successfully calculated for each correlation index for all patients and were frequently (77%) above 65 mm Hg. For all correlation indices, median time was substantially above impaired MA threshold (24.5-34.9%) and below target MAPopt (9.0-78.6%). Muscle and brain MAPopt show moderate correlation (MVx-THx r = 0.76, p < 0.001; MOx-COx r = 0.69, p = 0.005), with a median difference of -1.27 mm Hg (-9.85 to -0.18 mm Hg) and 0.05 mm Hg (-7.05 to 2.68 mm Hg). This study demonstrates, for the first time, the feasibility of calculating MA indices and MAPopt in skeletal muscle using NIRS. Future studies should explore the association between impaired skeletal muscle MA, ICU outcomes, and organ-specific differences in MA and MAPopt thresholds.

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Copyright © 2024 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the Society of Critical Care Medicine.

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Dr. Mendelson receives research support from the Manitoba Medical Services Foundation Dr. F. W. DuVal and John Henson Clinical Research Professorship. Drs. Mendelson and Zeiler have funding, that is, unrelated to this current project from the Health Sciences Centre Foundation (Winnipeg), the Canadian Institutes of Health Research (CIHR), the Canada Foundation for Innovation, and the Research Manitoba. Dr. Gomez is supported by the CIHR Fellowship program. Mr. Singh Sainbhi is supported by the University of Manitoba Graduate Fellowship in Biomedical Engineering—Doctoral Stream. Dr. Froese is supported through the Natural Sciences and Engineering Research Council of Canada (NSERC) Post-Doctoral Fellowship program. Dr. Zeiler is supported through the University of Manitoba Endowed Manitoba Public Insurance Chair in Neuroscience and the NSERC (DGECR-2022-00260, RGPIN-2022-03621, ALLRP-578524-22, ALLRP-576386-22, ALLRP-586244-23, I2IPJ 586104–23). Dr. Zarychanski receives research support from the Lyonel G. Israels Endowed Research Chair in Hematology, University of Manitoba; he has funding, that is, unrelated to the current project from the CIHR. The remaining authors have disclosed that they do not have any potential conflicts of interest.