Experimental Models of Acute Renal Failure and Erythropoietin: What Evidence of a Direct Effect?

Relaxin: new pathophysiological aspects and pharmacological perspectives for an old protein

Human relaxin-2 (hereafter simply defined as "relaxin") is a 6-kDa peptidic hormone best known for the physiological role played during pregnancy in the growth and differentiation of the reproductive tract and in the renal and systemic hemodynamic changes. This factor can also be involved in the pathophysiology of arterial hypertension and heart failure, in the molecular pathways of fibrosis and cancer, and in angiogenesis and bone remodeling. It belongs to the relaxin peptide family, whose members comprehensively exert numerous effects through interaction with different types of receptors, classified as relaxin family peptide (RXFP) receptors (RXFP1, RXFP2, RXFP3, RXFP4). Research looks toward the in-depth examination and complete understanding of relaxin in its various pleiotropic actions. The intent is to evaluate the likelihood of employing this substance for therapeutic purposes, for instance in diseases where a deficit could be part of the underlying pathophysiological mechanisms, also avoiding any adverse effect. Relaxin is already being considered as a promising drug, especially in acute heart failure. A careful study of the different RXFPs and their receptors and the comprehension of all biological activities of these hormones will probably provide new drugs with a potential wide range of therapeutic applications in the near future.

Peri-operative renal protection: The strategies revisited

Postoperative acute renal failure (ARF) is a serious complication which can result in a prolonged hospital stay and a high mortality and morbidity. Underlying renal disease, cardiac diseases, nephrotoxin exposure and renal hypoperfusion are the possible predisposing risk factors which can create a high probability for the development of ARF. The incidence of ARF is highest after major vascular, cardiac and high-risk thoraco-abdominal surgery. Among the various renal protection strategies, adequate peri-operative volume expansion and avoidance of hypovolemia is the most accepted and practiced strategy. Numerous bio-markers of renal injury are used to estimate the presence and extent of renal insult and various new are currently under trial. Traditional pharmacological interventions like dopamine, diuretics and calcium antagonists are not currently the first line of reno-protective agents. The new non-pharmacological and pharmacological methods may improve outcome in renal transplantation, contrast-induced nephropathy and in various other settings of ARF. The current review is an attempt to refresh the knowledge and put forth the various renal protection strategies during the peri-operative period.

Acute kidney injury in the intensive care unit

Acute kidney injury (AKI) is common among critically ill patients and results in increased mortality in this population. This review focuses on the diagnosis and management of AKI. The authors first explore new aspects of diagnosis, including new criteria that take into account even modest changes in renal function, and the development of novel biomarkers to allow earlier identification and better differential diagnosis of AKI. The authors also explore the available data on choice of dialysis modality and dialysis dose for the treatment of AKI, as well as the breakthrough development of the bioartificial kidney. Last, the authors review co-interventions that may have relevance to prognosis of AKI, such as intensive insulin therapy and the use of erythropoietin.

The prevention of acute kidney injury an in-depth narrative review: Part 2: Drugs in the prevention of acute kidney injury

The second part of this in-depth clinical review focuses on drugs used in the prevention of AKI in the patient at risk and/or in the management of the patient with incipient AKI. Among the drugs used to maintain a normal renal perfusion pressure, norepinephrine and vasopressin are most commonly used in hypotensive critically ill patients. The most recent RCT did not find a difference between low-dose vasopressin plus norepinephrine and norepinephrine alone in patients with septic shock, suggesting that either approach is reasonable. However, vasopressin may be beneficial in the less severe septic shock subgroup. Loop diuretics may convert an oliguric into a non-oliguric form of AKI that may allow easier fluid and/or nutritional support of the patient. Volume overload in AKI patients is common and diuretics may provide symptomatic benefit in that situation. However, loop diuretics are neither associated with improved survival, nor with better recovery of renal function in AKI. Among the renal vasodilating drugs, the routine administration of dopamine to patients for the prevention of AKI or incipient AKI is no longer justified. On the other hand, although additional studies may be warranted, fenoldopam may appear to be a likely candidate for the prevention of AKI, particularly in critically ill patients, if the positive results obtained in some recent studies are confirmed. Trials with natriuretic peptides were in general inconclusive but despite the fact that nesiritide is currently approved by the FDA only for the treatment of heart failure, this vasodilator may in the future play a role in the prevention of AKI, particularly in association with heart failure and cardiac surgery. The most recent trials seem to confirm a potential positive preventive effect of N-acetylcysteine (NAC), particularly in contrast-induced nephropathy (CIN), NAC alone should never take the place of IV hydration in patients at risk for CIN; fluids likely have a more substantiated benefit. At present, initiation of statin therapy for the prevention of CIN cannot be recommended, but these drugs should not be stopped before a radiological intervention in patients on chronic statin therapy. Rasburicase is very effective in the prevention of acute tumour lysis syndrome. Erythropoietin (EPO) has tissue-protective effects and prevents tissue damage during ischaemia and inflammation, and currently trials are performed with EPO in the prevention of AKI post-cardiac surgery, CIN and post-kidney transplantation. From this review it becomes clear that single-drug therapy will probably never be effective in the prevention of AKI and that multiple agents may be needed to improve outcomes. In addition, drugs should be administered early during the course of the disease.