Contributions to nephrology
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Review Comparative Study
Continuous renal replacement in critical illness.
Acute renal failure in the intensive care unit is usually part of the multiple organ dysfunction syndrome, and the complexity of illness in patients with this complication has risen in recent years. Continuous renal replacement therapy (CRRT) was introduced in the late 1970s and early 1980s to compensate for the inadequacies of conventional intermittent hemodialysis (IHD) in the treatment of these patients. IHD was considered aggressive and unphysiological, often resulting in hemodynamic intolerance and limited efficiency. ⋯ However, these studies are generally underpowered and have certain aspects which may influence the interpretation of their results. In addition, the development of hybrid techniques, such as slow extended daily dialysis, makes this a dynamic area of study where the terms of comparison are constantly changing. This article reviews recent trials comparing CRRT and IHD, and discusses their results and limitations.
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Continuous renal replacement therapies (CRRTs) are increasingly used in order to maintain normal or near-normal acid-base balance in intensive care unit (ICU) patients. Acid-base balance is greatly influenced by the type of dialysis employed and by the administration route of replacement fluids. In continuous veno-venous hemofiltration, buffer balance depends on losses with ultrafiltrate and gain with replacement fluid, while in techniques such as continuous veno-venous hemodiafiltration, clinicians should balance the role of the dialysate. ⋯ However, the dialysate buffer or electrolyte concentration need always to be balanced with that of the replacement fluids employed. Both fluids should contain electrolytes in concentrations aiming for a physiologic level and taking into account preexisting deficits or excess and all input and losses. Clinicians should be aware that in CRRTs the quality control for sterility, physical properties, individualized prescription and balance control are vitally important.
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Endotoxin is one of the principal biological substances that cause gram-negative septic shock. Lack of clinical success with antiendotoxin or anticytokine therapy has shifted interest to extracorporeal therapies to reduce circulating levels of the mediators of sepsis. Direct hemoperfusion with polymyxin-B-immobilized fiber (PMX-F) is a promising treatment of gram-negative sepsis in critically ill patients. ⋯ In a systematic review of 28 studies (pooled sample size 1,390 patients), the preliminary results of which are described here, PMX-F therapy appeared to significantly lower endotoxin levels, improve blood pressure, and reduce mortality. However, publication bias and lack of blinding need to be considered. These encouraging results need to be verified with large-scale controlled clinical trials.
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The practice of renal replacement therapy (RRT) has reached an optimal standard of care worldwide. Nevertheless, some aspects of acute renal failure treatment and support still present wide variability between different centers. This is especially true for the mode and dose of RRT. This review describes the epidemiology of dialysis prescription and delivery around the world based on recent observational studies and international surveys. ⋯ A trend to continuous therapies and increased RRT dosage over the last 10 years is shown by the surveys presented, even if scientific evidence is now very necessary as far as definitive RRT indications and prescriptions are concerned.
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Acute kidney injury (AKI) is a common and serious postoperative complication following exposure to cardiopulmonary bypass (CPB). Several mechanisms have been proposed by which the kidney can be damaged and interventional studies addressing known targets of renal injury have been undertaken in an attempt to prevent or attenuate CPB-associated AKI. However, no definitive strategy appears to protect a broad heterogeneous population of cardiac surgery patients from CPB-associated AKI. ⋯ Sodium bicarbonate is safe, simple to administer and inexpensive. If part of AKI after CPB is truly secondary to hemoglobin-induced pigment nephropathy, prophylactic sodium bicarbonate infusion might help attenuate it. A trial of such treatment might be a reasonable future investigation in higher risk patients receiving CPB.