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Objective: To investigate the impacts of continuous venovenous hemodiafiltration on the microcirculation in patients with acute kidney injury., Methods: A prospective observational pilot study conducted in a 40-bed, open clinical-surgical intensive care unit of a private tertiary care hospital located in the city of São Paulo (SP), Brazil. Microcirculation was assessed using near-infrared spectroscopy by means of a 15mm probe placed over the thenar eminence. Vascular occlusion test was performed on the forearm to be submitted to near-infrared spectroscopy by inflation of a sphygmomanometer cuff to 30mmHg higher than the systolic arterial pressure. The primary endpoint was the assessment of near-infrared spectroscopy-derived parameters immediately before, 1, 4 and 24 hours after the initiation of continuous venovenous hemodiafiltration., Results: Nine patients were included in this pilot study over a period of 2 months. Minimum tissue oxygen saturation measured during the vascular occlusion test was the only near-infrared spectroscopy-derived parameter to differed over the time (decrease compared to baseline values up to 24 hours after initiation of continuous venovenous hemodiafiltration)., Conclusion: The impacts of microcirculatory dysfunction on clinical outcomes of patients undergoing to continuous venovenous hemodiafiltration need to be further investigated.

Parameters related to macrocirculation, such as the mean arterial pressure, central venous pressure, cardiac output, mixed venous saturation and central oxygen saturation, are commonly used in the hemodynamic assessment of critically ill patients. However, several studies have shown that there is a dissociation between these parameters and the state of microcirculation in this group of patients. Techniques that allow direct viewing of the microcirculation are not completely disseminated, nor are they incorporated into the clinical management of patients in shock. The numerous techniques developed for microcirculation assessment include clinical assessment (e.g., peripheral perfusion index and temperature gradient), laser Doppler flowmetry, tissue oxygen assessment electrodes, videomicroscopy (orthogonal polarization spectral imaging, sidestream dark field imaging or incident dark field illumination) and near infrared spectroscopy. In the near future, the monitoring and optimization of tissue perfusion by direct viewing and microcirculation assessment may become a goal to be achieved in the hemodynamic resuscitation of critically ill patients.

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Objective: To address the impact of continuous venovenous hemodiafiltration (CVVHDF) on microcirculation of patients with acute kidney injury. Methods: Prospective observational pilot study was conducted in a forty bed, open clinical-surgical, ICU of a private, tertiary care, hospital in São Paulo, Brazil. Microcirculation was assessed using near-infrared spectroscopy (NIRS) (InSpectra StO2 Tissue Oxygenation Monitor model 650, Hutchinson, MN, USA) with a 15-mm probe over the thenar eminence. Vascular occlusion test (VOT) were performed by inflation of a sphygmomanometer cuff to 30 mmHg above the systolic arterial pressure on the forearm of the NIRS during 3 minutes. Primary endpoint was the assessment of NIRSderived parameters, immediately before, one, four, and 24 hours after the initiation of CVVHDF. Results: Nine patients were included in this study over a period of two months. Median (IQR) age was 66 (61 - 76) years and SAPS III score was 60 (51-63). Baseline median (IQR) tissue oxygen saturation (StO2), maximum StO2, descending slope, ascending slope and recovery time were, respectively, 83 (81-89) %, 94 (87-95) %, 8.3 (4.4-10.4) %/min, 1.6 (1.2-3.1) %/sec and 31.0 (29.5-48.5) sec. Only minimum StO2 during VOT was different over the time, with a decrease from 64 (49-67) % at baseline to 52 (43-59) % after 24 hours of CVVHDF initiation (p=0.023). Conclusion: Minimum StO2 measured during the VOT was the only NIRS-derived parameter affected during the first 24 hours of CVVHDF. [ABSTRACT FROM AUTHOR]