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.

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.

Background: The three-way indwelling urinary catheter (IUC) is used for continuous bladder irrigation and is considered the cornerstone for clinical treatment of patients with macroscopic hematuria. Although there seems to be a logical relationship between catheter size and efficacy of irrigation and drainage, we often observe relevant variations in these parameters between different brands of catheters available on the market. The aim of this study was to compare the mechanical properties of different models of latex and silicone three-way catheters in an in vitro setting that resembles clinical use. Methods: Three different three-way catheters were evaluated: Gold Silicone-Coated Rusch® (Model A), 100% Silicone Rusch® (Model B) and X-Flow Coloplast® (Model C). Irrigation channel, drainage channel, and overall cross-sectional areas were all digitally measured. Irrigation and drainage channel flow rates were measured and correlated with their corresponding catheter cross-sectional area values. Results: Different catheter models of the same caliber have different internal irrigation port diameters, internal drainage port diameters and internal cuff port diameters. The Model C IUC internal irrigation port diameter is significantly larger than models A and B. When flows were evaluated, we found that in the same model, the increase in caliber of the IUC was related to an increased drainage flow, but not to an increased irrigation flow. Conclusion: Precise measurements of the internal architecture of the three-way catheter, rather than relying on the caliber itself, could assist surgeons in choosing the best product for each specific patient, while minimizing complications.

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