Contributions to nephrology
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Acute lung injury (ALI) and acute kidney injury (AKI) are complications often encountered in the setting of critical illness. Both forms of end-organ injury commonly occur in similar settings of systemic inflammatory response syndrome, shock, and evolving multiple organ dysfunction. Distant organ effects of apparently isolated injuries to the lungs, gut, and kidneys have all been discovered in recent years. In this review of the emerging evidence of deleterious bidirectional organ crosstalk between the lungs and kidney, we will focus on the role of ventilator-induced kidney injury in the pathogenesis of AKI in patients with ALI.
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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 correct selection of anticoagulation in acute blood purification is crucial for avoiding exacerbation of bleeding in critical care patients with acute renal failure, as these patients frequently exhibit hemorrhagic complications. The mode of acute blood purification is determined mainly by the patient's hemodynamic stability, and continuous renal replacement therapies (CRRTs) have been extensively performed for patients with hemodynamic instability. Unfractionated heparin, low molecular weight heparin and nafamostat mesilate (nafamostat) are available in acute blood purification for the patients. ⋯ This is especially the case with patients of small stature, which is the case for many Japanese people. Nafamostat can be used safely in CRRT for critical care patients with acute renal failure and bleeding risks, because it acts as a regional anticoagulant due to its pharmacological characteristics. Nafamostat has been widely used in acute blood purification at critical care units in Japan.
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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.