Contributions to nephrology
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Polymyxin B fiber column is a medical device designed to reduce blood endotoxin levels in sepsis. Gram-negative-induced abdominal sepsis is likely to be associated with high circulating endotoxin. In June 2009, the EUPHAS study (Early Use of Polymyxin B Hemoperfusion in Abdominal Sepsis) was published in JAMA. ⋯ The PaO(2)/FiO(2) ratio increased slightly (235 to 264; p = 0.049) in the polymyxin B group, but not in the conventional therapy group (217 to 228; p = 0.79). SOFA scores improved in the polymyxin B group, but not in the conventional therapy group (change in SOFA: -3.4 vs. -0.1; p = 0.001), and 28-day mortality was 32% (11/34 patients) in the polymyxin B group and 53% (16/30 patients) in the conventional therapy group (unadjusted HR: 0.43, 95% CI: 0.20-0.94; adjusted HR: 0.36, 95% CI:0.16-0.80). The study demonstrated how polymyxin B hemoperfusion added to conventional therapy significantly improved hemodynamics and organ dysfunction and reduced 28-day mortality in a targeted population with severe sepsis and/or septic shock from intra-abdominal Gram-negative infections.
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The extracorporeal carbon dioxide removal (ECCO(2)R) concept, used as an integrated tool with conventional ventilation, plays a role in adjusting respiratory acidosis consequent to tidal volume (Vt) reduction in a protective ventilation setting. This concept arises from the extracorporeal membrane oxygenation (ECMO) experience. Kolobow and Gattinoni were the first to introduce extracorporeal support, with the intent to separate carbon dioxide removal from oxygen uptake; they hypothesized that to allow the lung to 'rest' oxygenation via mechanical ventilation could be dissociated from decarboxylation via extracorporeal carbon dioxide removal. ⋯ The future development of more and more efficient devices capable of removing a substantial amount of carbon dioxide production (30-100%) with blood flows of 250-500 ml/min is foreseeable. Moreover, in the future ARDS management should include a minimally invasive ECCO(2)R circuit associated with noninvasive ventilation. This would embody the modern mechanical ventilation philosophy: avoid tracheal tubes; minimize sedation, and prevent ventilator-induced acute lung injury and nosocomial infections.
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Several large observational studies or randomized controlled trials in the field of critical care nephrology have been completed and reported, or recently completed or have recently begun recruitment. These studies provide important information to guide our appreciation of current practice and consider new potentially effective intervention for the prevention or attenuation of acute kidney injury or suggest new avenues for the use of renal replacement therapy (RRT) in the treatment of sepsis. In particular, two studies, the ATN study and the RENAL study (both multicenter randomized controlled trials of > 1,000 patients) provide, for the first time, level I evidence to guide the practice of RRT in critically ill patients and to better define the optimal intensity of such RRT in this setting. Clinicians practicing in the field of critical care nephrology need to be aware of these trials, their details, their findings or design or current recruitment rate and likely time of completion to continue to offer their patients the highest level of evidence-based medical care.
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During critical illness, reductions in renal blood flow (RBF) are believed to be a major cause of kidney dysfunction, and therapy is often aimed at restoration of RBF. Despite this, our ability to measure RBF during critical illness has been limited by the invasiveness of the available techniques. Ciné Phase-Contrast Magnetic Resonance Imaging (CPC-MRI) represents an entirely noninvasive, contrast-free method of measuring blood flow with the potential of enabling the measurement of blood flow to major organs including the kidney. We have recently assessed the feasibility of measuring RBF by means of CPC-MRI in 2 critically ill patients with septic acute kidney injury and were able to compare such measurements to those obtained in a normal volunteer.
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Acute kidney injury (AKI) is a common complication of critical illness. While the etiology of AKI in critically ill patients is likely often multifactorial, sepsis has consistently been found an important contributing factor and has been associated with high attributable morbidity and mortality. Accordingly, the timely identification of septic AKI in critically ill patients is clearly a clinical priority. ⋯ In addition, several urinary biochemical tests, derived indices and microscopy have also been widely cited as valuable in the diagnosis and classification of AKI. However, the value of these urinary tests in the diagnosis, classification, prognosis and clinical management in septic AKI remains unclear, due in part to a lack of kidney morphologic changes and histopathology in human studies of septic AKI. This review will summarize the urinary biochemistry and microscopy in septic AKI.