title: Renovascular reactivity measured by near-infrared spectroscopy.
abstract: Hypotension and shock are risk factors for death, renal insufficiency, and stroke in preterm neonates. Goal-directed neonatal hemodynamic management lacks end-organ monitoring strategies to assess the adequacy of perfusion. Our aim is to develop a clinically viable, continuous metric of renovascular reactivity to gauge renal perfusion during shock. We present the renovascular reactivity index (RVx), which quantifies passivity of renal blood volume to spontaneous changes in arterial blood pressure. We tested the ability of the RVx to detect reductions in renal blood flow. Hemorrhagic shock was induced in 10 piglets. The RVx was monitored as a correlation between slow waves of arterial blood pressure and relative total hemoglobin (rTHb) obtained with reflectance near-infrared spectroscopy (NIRS) over the kidney. The RVx was compared with laser-Doppler measurements of red blood cell flux, and renal laser-Doppler measurements were compared with cerebral laser-Doppler measurements. Renal blood flow decreased to 75%, 50%, and 25% of baseline at perfusion pressures of 60, 45, and 40 mmHg, respectively, whereas in the brain these decrements occurred at pressures of 30, 25, and 15 mmHg, respectively. The RVx compared favorably to the renal laser-Doppler data. Areas under the receiver operator characteristic curves using renal blood flow thresholds of 50% and 25% of baseline were 0.85 (95% CI, 0.83-0.87) and 0.90 (95% CI, 0.88-0.92). Renovascular autoregulation can be monitored and is impaired in advance of cerebrovascular autoregulation during hemorrhagic shock.
authors.affiliation: Department of Pediatrics, Section of Neonatology, Texas Children's Hospital/Baylor College of Medicine, Houston, TX 77030, USA. cjrhee@texaschildrens.org
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Rhee
authors.forename: Kathleen K
authors.initials: KK
authors.lastname: Kibler
authors.forename: R Blaine
authors.initials: RB
authors.lastname: Easley
authors.forename: Dean B
authors.initials: DB
authors.lastname: Andropoulos
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
authors.forename: Peter
authors.initials: P
authors.lastname: Smielewski
authors.forename: Ken M
authors.initials: KM
authors.lastname: Brady
mesh_terms: D000465:Algorithms; D000818:Animals; D062186:Arterial Pressure; D001795:Blood Pressure Determination / Q000379:methods; D001811:Blood Volume Determination / Q000379:methods; D006454:Hemoglobins / Q000032:analysis*; D010092:Oximetry / Q000379:methods*; D012077:Renal Artery / Q000503:physiopathology*; D012079:Renal Circulation; D051437:Renal Insufficiency / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012769:Shock / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013552:Swine
chemical_list: D006454:Hemoglobins