Management and Prevention of Acute Renal Failure: Notes from the ICC Conference
Antoinette Spevetz, MD, FCCM
Cooper University Hospital
Oxford, Pennsylvania, USA
The 9th International Consensus Conference in Intensive Care Medicine, held in Montreal, Canada, allowed intensivists and nephrologists from around the world to address vital questions related to the management and prevention of acute renal therapy in the intensive care unit (ICU). Over two days of intense learning, experts offered presentations on five specific questions related to acute renal failure (ARF) while a jury debated these issues.
The American Thoracic Society held the May 2007 meeting, which was sponsored by the Society of Critical Care Medicine, the European Respiratory Society, the European Society of Intensive Care Medicine and the Société de Réanimation de Langue Française. A panel of experts addressed these questions:
• How can we identify acute renal failure in ICU patients?
• What can we do to protect against developing acute renal
failure during routine ICU care?
• Can we prevent acute renal failure from developing in
specific disease states?
• How should we manage a critically ill patient who
develops acute renal failure?
• What is the impact of renal replacement on mortality and
recovery?
The important topics in acute renal failure were debated, evidence was analyzed, and participants left the meeting with a great breadth of knowledge to enhance their critical care practice. A summary of the meeting’s highlights is provided here, but a consensus paper prepared by the jury will be released later this year.
There is no established definition for acute renal failure and we have no sensitive marker to define early acute renal failure. The Beginning and Ending Supportive Therapy for the Kidney (BEST) study, which is the only international study and largest epidemiological study for ARF, found that the average incidence of severe acute renal failure requiring renal replacement therapy (RRT) is approximately 4%. Hospital mortality rates of those treated with RRT reach 60.3%. Unfortunately, available data are not sufficient for clinicians to predict accurately which ICU patients will develop acute kidney injury (AKI).
Fluid resuscitation in patients who are volume depleted is critical; however, for patients who already are volume overloaded, resuscitation can worsen hypertension, cause pulmonary edema and hypoxia, and require mechanical ventilation. Ultrafiltration may be possible, removing 10 to 20 liters over several days, avoiding the complication of prolonged mechanical ventilation. The type of fluid used for resuscitation has been debated. No large randomized control trial has shown that colloid-based resuscitation was associated with improved renal outcome. In fact, there is evidence that the use of colloid exposes patients to a higher risk of renal dysfunction.
Current literature suggests that a minimum mean arterial pressure (MAP) of 65 mm Hg is appropriate for drug titration in patients requiring pressors. Further studies are needed to determine the MAP choice and specific pressor to optimize outcome.
Prevention of contrast-induced nephropathy is of paramount importance. Consensus panel recommendations included avoiding contrast media when possible, optimizing volume status with nephron-sparing surgery or isotonic sodium bicarbonate, and using acetylcysteine. Use of low volume and low osmolar contrast media and discontinuation of all drugs that could affect renal function adversely are recommended. Follow-up with creatinine in 24 to 72 hours is warranted. In the ICU, periprocedural hemofiltration has been shown to prevent contrast-induced nephropathy in patients who underwent percutaneous coronary intervention.
AKI in specific disease states deserves special attention. In liver disease, risk factors for AKI include ascites, spontaneous
bacterial peritonitis, sepsis, aminoglycoside use, gastrointestinal bleeding, cirrhosis and hypotension. Patients are sensitized because of endogenous nephrotoxins such as bile acids and endotoxin.
AKI occurring after cardiac surgery is an ominous event. There are a number of risk factors that have been shown to predict AKI, including left ventricular dysfunction, diabetes, peripheral vascular disease, chronic obstructive pulmonary disease, emergent surgery, intra-aortic balloon pumps, female gender and chronic kidney disease. The most important risk factor probably is an increased serum creatinine. At present, no therapeutic interventions appear to prevent AKI in patients undergoing coronary artery bypass graft. Off-pump surgery may have some utility, but technical issues limit its use.
Tumor lysis syndrome is seen in lymphoma and leukemia and causes a number of metabolic disorders as well as acute renal failure. Fluids and allopurinol or uricase given in advance of chemo- or radiotherapy may prevent AKI. Similarly, in patients with rhabdomyolysis, volume resuscitation and forced diuresis are used to avoid myoglobinuric tubular injury.
Intra-abdominal hypertension (IAH) is a cause of AKI in the critically ill patient. The etiology is likely related to renal blood flow as well as hormonal changes. Abdominal decompression is helpful, although this alone did not reverse the sequelae once IAH was established. Management of AKI is based on:
• Preserving and optimizing renal function
• Correcting and maintaining electrolytes
• Correcting acid base abnormalities
• Minimizing secondary organ damage
• Managing effects of decreased renal function
Attention to nutritional status and strict glucose control also is paramount; the protein needs of the patients frequently are underestimated.
There was no consensus regarding indications for RRT. Clearly refractory hyperkalemia, fluid overload, severe acidosis and overt uremic symptoms are causes for RRT. The degree of azotemia and duration of AKI requiring dialysis are more controversial. Early initiation to the ICU may have some advantages over the general population secondary to increased catabolism, volume resuscitation, metabolic derangements.
Studies comparing CRRT with conventional hemodialysis have not been designed to give a clear answer regarding outcomes. It seems that the dose of dialysis of at least 35 mL/kg/hr is the most important factor.
The impact of ARF on morbidity and survival rates is significant. Any degree of renal failure increases overall mortality rates and those who suffer postoperative ARF have a six-fold increase in mortality. Those requiring RRT have a predicted in-hospital mortality rate of >50%.
In analyzing CRRT versus intermittent hemodialysis, no controlled studies have shown the superiority of CRRT. It appears that the major factor is the delivered dose of dialysis. Improvements in outcomes are shown with both hemodialysis and CRRT when the dose is increased. Ongoing studies may resolve some of the unanswered questions regarding dosing of RRT.
Controversy exists as to the role of high-volume hemofiltration as adjunctive therapy in patients with severe septic shock. High-volume hemofiltration may be a potent immunomodulatory treatment.
The 9th International Consensus Conference in Intensive Care Medicine produced many opportunities for ongoing research in this important field. The Society of Critical Care Medicine and the critical care community await the consensus paper produced from this meeting to continue to improve strategies in the management and prevention of acute renal failure.
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