Long-Term Outcomes of Acute Kidney Injury
2008; Elsevier BV; Volume: 15; Issue: 3 Linguagem: Inglês
10.1053/j.ackd.2008.04.009
ISSN1548-5609
Autores Tópico(s)Trauma, Hemostasis, Coagulopathy, Resuscitation
ResumoAcute kidney injury (AKI) is common in the intensive care unit and is associated with significant morbidity and mortality. Based on the RIFLE criteria, AKI occurs in up to 67% of patients in the intensive care unit (ICU), with approximately 4% of critically ill patients requiring renal replacement therapy (RRT). It is well known that this subset of AKI patients who require RRT have an in-hospital mortality rate exceeding 50%. However, long-term outcomes of survivors of AKI requiring RRT remain poorly described. Long-term mortality is greater in those patients who survived AKI when compared with critically ill patients without AKI. Long-term morbidity, renal and extrarenal, is a frequent and underappreciated complication of AKI. Among survivors of AKI at long-term follow-up (1-10 years), approximately 12.5% are dialysis dependent (wide range of 1%-64%, depending on the patient population) and 19% to 31% have chronic kidney disease. According to the United States Renal Data System, "acute tubular necrosis without recovery" as a cause of end-stage kidney disease increased from 1.2% in 1994 to 1998 to 1.7% in 1999 to 2003. The incidence will likely continue to rise with the aging population, increase in comorbidities, and expansion of intensive care unit capabilities. AKI is an underrecognized cause of chronic kidney disease (CKD) and patients who survive should be followed closely for new CKD and/or progression of underlying CKD Acute kidney injury (AKI) is common in the intensive care unit and is associated with significant morbidity and mortality. Based on the RIFLE criteria, AKI occurs in up to 67% of patients in the intensive care unit (ICU), with approximately 4% of critically ill patients requiring renal replacement therapy (RRT). It is well known that this subset of AKI patients who require RRT have an in-hospital mortality rate exceeding 50%. However, long-term outcomes of survivors of AKI requiring RRT remain poorly described. Long-term mortality is greater in those patients who survived AKI when compared with critically ill patients without AKI. Long-term morbidity, renal and extrarenal, is a frequent and underappreciated complication of AKI. Among survivors of AKI at long-term follow-up (1-10 years), approximately 12.5% are dialysis dependent (wide range of 1%-64%, depending on the patient population) and 19% to 31% have chronic kidney disease. According to the United States Renal Data System, "acute tubular necrosis without recovery" as a cause of end-stage kidney disease increased from 1.2% in 1994 to 1998 to 1.7% in 1999 to 2003. The incidence will likely continue to rise with the aging population, increase in comorbidities, and expansion of intensive care unit capabilities. AKI is an underrecognized cause of chronic kidney disease (CKD) and patients who survive should be followed closely for new CKD and/or progression of underlying CKD Acute kidney injury (AKI) is common in hospitalized patients and is associated with a considerable increase in morbidity and mortality. Specifically, AKI in the hospitalized patient results in an increase in the length of intensive care unit (ICU) and hospital stay, ventilator days, overall hospital cost, and, most importantly, mortality.1Chertow G.M. Burdick E. Honour M. et al.Acute kidney injury, mortality, length of stay, and costs in hospitalized patients.J Am Soc Nephrol. 2005; 16: 3365-3370Crossref PubMed Scopus (2522) Google Scholar, 2Nash K. Hafeez A. Hou S. Hospital-acquired renal insufficiency.Am J Kidney Dis. 2002; 39: 930-936Abstract Full Text Full Text PDF PubMed Scopus (1554) Google Scholar, 3Uchino S. Kellum J.A. Bellomo R. et al.Acute renal failure in critically ill patients: A multinational, multicenter study.JAMA. 2005; 294: 813-818Crossref PubMed Scopus (3172) Google Scholar, 4Mehta R.L. Pascual M.T. Soroko S. et al.Spectrum of acute renal failure in the intensive care unit: The PICARD experience.Kidney Int. 2004; 66: 1613-1621Crossref PubMed Scopus (675) Google Scholar, 5Liangos O. Wald R. O'Bell J.W. et al.Epidemiology and outcomes of acute renal failure in hospitalized patients: A national survey.Clin J Am Soc Nephrol. 2006; 1: 43-51Crossref PubMed Scopus (439) Google Scholar, 6Hoste E.A. Clermont G. Kersten A. et al.RIFLE criteria for acute kidney injury are associated with hospital mortality in critically ill patients: A cohort analysis.Crit Care. 2006; 10: R73Crossref PubMed Scopus (1157) Google Scholar The "short-term" or in-hospital associated morbidity and mortality have been written about extensively in the literature and are well appreciated by clinicians and administrators alike. It is the "long-term" outcome of AKI that has been less well studied. A greater understanding of, and appreciation for, the long-term outcomes of AKI is critical for both the acute care of the hospitalized patient and appropriate outpatient follow-up for survivors of AKI. Definitions of AKI abound and etiologies are multiple. Fortunately, there has been tremendous progress in establishing a uniform classification of AKI beginning with the RIFLE criteria7Bellomo R. Ronco C. Kellum J.A. et al.Acute renal failure—Definition, outcome measures, animal models, fluid therapy and information technology needs: The Second International Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) Group.Crit Care. 2004; 8: R204-R212Crossref PubMed Google Scholar established in 2002 by the Acute Dialysis Quality Initiative. More recently, the Acute Kidney Injury Network (AKIN) modified the RIFLE criteria, in part by lowering the absolute qualifying rise in serum creatinine (SCr) from ≥0.5 mg/dL to ≥0.3 mg/dL.8Mehta R.L. Kellum J.A. Shah S.V. et al.Acute Kidney Injury Network: Report of an initiative to improve outcomes in acute kidney injury.Crit Care. 2007; 11: R31Crossref PubMed Scopus (5256) Google Scholar The AKIN criteria have not yet been validated. AKI is a complex disorder occurring in a variety of clinical settings with multiple clinical manifestations ranging from small increases in SCr to the requirement for renal replacement therapy (RRT). Although it has been increasingly recognized that even small changes in SCr are associated with increased mortality,1Chertow G.M. Burdick E. Honour M. et al.Acute kidney injury, mortality, length of stay, and costs in hospitalized patients.J Am Soc Nephrol. 2005; 16: 3365-3370Crossref PubMed Scopus (2522) Google Scholar, 9Coca S.G. Peixoto A.J. Garg A.X. et al.The prognostic importance of a small acute decrement in kidney function in hospitalized patients: A systematic review and meta-analysis.Am J Kidney Dis. 2007; 50: 712-720Abstract Full Text Full Text PDF PubMed Scopus (181) Google Scholar, 10Ostermann M. Chang R.W. Acute kidney injury in the intensive care unit according to RIFLE.Crit Care Med. 2007; 35: 1837-1843Crossref PubMed Scopus (536) Google Scholar, 11Loef B.G. Epema A.H. Smilde T.D. et al.Immediate postoperative renal function deterioration in cardiac surgical patients predicts in-hospital mortality and long-term survival.J Am Soc Nephrol. 2005; 16: 195-200Crossref PubMed Scopus (389) Google Scholar, 12Dasta J.F. Kane-Gill S.L. Durtschi A.J. et al.Costs and outcomes of acute kidney injury (AKI) following cardiac surgery.Nephrol Dial Transplant. 2008; (Jan 4 [Epub ahead of print])PubMed Google Scholar there are little data available on the long-term outcomes of these less severe forms of AKI. The focus of this review, therefore, is on the long-term outcomes of AKI in critically ill patients. AKI has been previously reported to occur in approximately 7% of all hospitalized patients.2Nash K. Hafeez A. Hou S. Hospital-acquired renal insufficiency.Am J Kidney Dis. 2002; 39: 930-936Abstract Full Text Full Text PDF PubMed Scopus (1554) Google Scholar More recently, the incidence has been described in up to 18%13Uchino S. Bellomo R. Goldsmith D. et al.An assessment of the RIFLE criteria for acute renal failure in hospitalized patients.Crit Care Med. 2006; 34: 1913-1917Crossref PubMed Scopus (733) Google Scholar using the RIFLE criteria.7Bellomo R. Ronco C. Kellum J.A. et al.Acute renal failure—Definition, outcome measures, animal models, fluid therapy and information technology needs: The Second International Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) Group.Crit Care. 2004; 8: R204-R212Crossref PubMed Google Scholar However, AKI in critically ill patients is substantially more common. The epidemiology of AKI in the ICU depends on the definition used (to date, greater than 35 appear in the literature). The often-reported incidence of AKI in the ICU ranges between 1% and 31%.3Uchino S. Kellum J.A. Bellomo R. et al.Acute renal failure in critically ill patients: A multinational, multicenter study.JAMA. 2005; 294: 813-818Crossref PubMed Scopus (3172) Google Scholar, 4Mehta R.L. Pascual M.T. Soroko S. et al.Spectrum of acute renal failure in the intensive care unit: The PICARD experience.Kidney Int. 2004; 66: 1613-1621Crossref PubMed Scopus (675) Google Scholar, 14Metnitz P.G. Krenn C.G. Steltzer H. et al.Effect of acute renal failure requiring renal replacement therapy on outcome in critically ill patients.Crit Care Med. 2002; 30: 2051-2058Crossref PubMed Scopus (722) Google Scholar Using the more sensitive RIFLE criteria, the overall incidence of AKI in the ICU ranges between 36% and 67%.6Hoste E.A. Clermont G. Kersten A. et al.RIFLE criteria for acute kidney injury are associated with hospital mortality in critically ill patients: A cohort analysis.Crit Care. 2006; 10: R73Crossref PubMed Scopus (1157) Google Scholar, 10Ostermann M. Chang R.W. Acute kidney injury in the intensive care unit according to RIFLE.Crit Care Med. 2007; 35: 1837-1843Crossref PubMed Scopus (536) Google Scholar, 15Bagshaw S.M. George C. Dinu I. et al.A multi-centre evaluation of the Rifle criteria for early acute kidney injury in critically ill patients.Nephrol Dial Transplant. 2007; 23: 1203-1210Crossref PubMed Scopus (393) Google Scholar Furthermore, multiple investigators have reported the incidence of "severe" ICU-related AKI requiring RRT to be approximately 4% (range, 3.4%-4.9%).3Uchino S. Kellum J.A. Bellomo R. et al.Acute renal failure in critically ill patients: A multinational, multicenter study.JAMA. 2005; 294: 813-818Crossref PubMed Scopus (3172) Google Scholar, 10Ostermann M. Chang R.W. Acute kidney injury in the intensive care unit according to RIFLE.Crit Care Med. 2007; 35: 1837-1843Crossref PubMed Scopus (536) Google Scholar, 14Metnitz P.G. Krenn C.G. Steltzer H. et al.Effect of acute renal failure requiring renal replacement therapy on outcome in critically ill patients.Crit Care Med. 2002; 30: 2051-2058Crossref PubMed Scopus (722) Google Scholar, 16Bagshaw S.M. Laupland K.B. Doig C.J. et al.Prognosis for long-term survival and renal recovery in critically ill patients with severe acute renal failure: A population-based study.Crit Care. 2005; 9: R700-R709Crossref PubMed Google Scholar The subset of patients requiring RRT in the ICU have been the primary focus of the majority of published studies describing long-term outcomes of AKI.16Bagshaw S.M. Laupland K.B. Doig C.J. et al.Prognosis for long-term survival and renal recovery in critically ill patients with severe acute renal failure: A population-based study.Crit Care. 2005; 9: R700-R709Crossref PubMed Google Scholar, 17Liano F. Felipe C. Tenorio M.T. et al.Long-term outcome of acute tubular necrosis: A contribution to its natural history.Kidney Int. 2007; 71: 679-686Crossref PubMed Scopus (115) Google Scholar, 18Leacche M. Rawn J.D. Mihaljevic T. et al.Outcomes in patients with normal serum creatinine and with artificial renal support for acute renal failure developing after coronary artery bypass grafting.Am J Cardiol. 2004; 93: 353-356Abstract Full Text Full Text PDF PubMed Scopus (67) Google Scholar, 19Korkeila M. Ruokonen E. Takala J. Costs of care, long-term prognosis and quality of life in patients requiring renal replacement therapy during intensive care.Intensive Care Med. 2000; 26: 1824-1831Crossref PubMed Scopus (183) Google Scholar, 20Schiffl H. Renal recovery from acute tubular necrosis requiring renal replacement therapy: A prospective study in critically ill patients.Nephrol Dial Transplant. 2006; 21: 1248-1252Crossref PubMed Scopus (123) Google Scholar AKI is a growing problem. Based on the most recent release from the United States Renal Data System, the number of patients being diagnosed with AKI grew 245% between 1993 and 1995 and 2003 and 2005 to reach an incidence of more than 69,000 per year.21Collins A.J. Foley R. Herzog C. et al.Excerpts from the United States Renal Data System 2007 annual data report.Am J Kidney Dis. 2008; 51: S1-S320PubMed Google Scholar Several different surveys have also documented an increase in the number of hospitalizations that included a diagnosis of AKI. A study done first in 1979 and subsequently repeated in 1996 documented an increase in hospital acquired renal insufficiency from a frequency of 4.9% in 1983 up to 7.2% in 1996.2Nash K. Hafeez A. Hou S. Hospital-acquired renal insufficiency.Am J Kidney Dis. 2002; 39: 930-936Abstract Full Text Full Text PDF PubMed Scopus (1554) Google Scholar, 22Hou S.H. Bushinsky D.A. Wish J.B. et al.Hospital-acquired renal insufficiency: A prospective study.Am J Med. 1983; 74: 243-248Abstract Full Text PDF PubMed Scopus (985) Google Scholar An investigation into Medicare claims showed an increase of 11% per year in the number of hospitalizations with AKI between 1979 and 2001,23Xue J.L. Daniels F. Star R.A. et al.Incidence and mortality of acute renal failure in Medicare beneficiaries, 1992 to 2001.J Am Soc Nephrol. 2006; 17: 1135-1142Crossref PubMed Scopus (623) Google Scholar whereas a study based on the International Classification of Diseases codes found an increase in the cases of AKI identified from discharge codes from 0.4% in 1988 to 2.1% in 2002.24Waikar S.S. Wald R. Chertow G.M. et al.Validity of International Classification of Diseases, Ninth Revision, Clinical Modification Codes for Acute Renal Failure.J Am Soc Nephrol. 2006; 17: 1688-1694Crossref PubMed Scopus (376) Google Scholar The increased incidence of AKI over time is multifactorial. Clearly, both an increased awareness of AKI as well as the establishment of more sensitive definitions contribute significantly but do not entirely explain the continued rise in AKI in the hospitalized patient. Additional contributors are likely because of more aggressive support of the critically ill patient, complications of modern diseases such as human immunodeficiency virus/acquired immunodeficiency syndrome, and the introduction and more widespread use of a number of new medications and hospital-based diagnostic and interventional procedures. Given that AKI is common and increasing in incidence, defining the long-term outcomes of this clinically important entity are of paramount importance. Over the last few years, there has been increasing attention paid to the growing burden of critical care in terms of both patient mortality and financial cost. For this reason, there has been an increasing number of studies in the critical care literature exploring the long-term outcomes of survivors of the ICU, in general,25Herridge M.S. Long-term outcomes after critical illness: Past, present, future.Curr Opin Crit Care. 2007; 13: 473-475Crossref PubMed Scopus (32) Google Scholar and in those with AKI, in particular.16Bagshaw S.M. Laupland K.B. Doig C.J. et al.Prognosis for long-term survival and renal recovery in critically ill patients with severe acute renal failure: A population-based study.Crit Care. 2005; 9: R700-R709Crossref PubMed Google Scholar, 19Korkeila M. Ruokonen E. Takala J. Costs of care, long-term prognosis and quality of life in patients requiring renal replacement therapy during intensive care.Intensive Care Med. 2000; 26: 1824-1831Crossref PubMed Scopus (183) Google Scholar, 26Gopal I. Bhonagiri S. Ronco C. et al.Out of hospital outcome and quality of life in survivors of combined acute multiple organ and renal failure treated with continuous venovenous hemofiltration/hemodiafiltration.Intensive Care Med. 1997; 23: 766-772Crossref PubMed Scopus (102) Google Scholar, 27Morgera S. Kraft A.K. Siebert G. et al.Long-term outcomes in acute renal failure patients treated with continuous renal replacement therapies.Am J Kidney Dis. 2002; 40: 275-279Abstract Full Text Full Text PDF PubMed Scopus (216) Google Scholar Long-term outcomes, for the purpose of this review, will include both morbidity (renal and extrarenal) and mortality. Just as definitions of AKI vary throughout the literature so, too, do definitions of kidney recovery. The vast majority of literature defines kidney recovery as simply independence from dialysis. This definition ignores those patients with new or worsened chronic kidney disease (CKD) as sequelae of their AKI. Few studies have explored the long-term impact of AKI. Because most patients recover enough kidney function to be independent from RRT at hospital discharge, those patients with CKD as a complication of their AKI may go unrecognized. Based on the best data available, most clinicians (both nephrologists and nonnephrologists) would agree that "complete" kidney recovery means a return to pre-AKI baseline. However, even a return of SCr to pre-AKI levels may not represent a true "complete" recovery. That is to say that potentially the injury itself may increase the risk of subsequent events and decrease kidney reserve leading to an increased risk of CKD. Survival, kidney function, and quality of life are key issues in evaluating the long-term outcomes of acute kidney injury. Probably the most well recognized complication of AKI in the ICU is the high mortality rate which exceeds 50% in the majority of studies2Nash K. Hafeez A. Hou S. Hospital-acquired renal insufficiency.Am J Kidney Dis. 2002; 39: 930-936Abstract Full Text Full Text PDF PubMed Scopus (1554) Google Scholar, 3Uchino S. Kellum J.A. Bellomo R. et al.Acute renal failure in critically ill patients: A multinational, multicenter study.JAMA. 2005; 294: 813-818Crossref PubMed Scopus (3172) Google Scholar, 4Mehta R.L. Pascual M.T. Soroko S. et al.Spectrum of acute renal failure in the intensive care unit: The PICARD experience.Kidney Int. 2004; 66: 1613-1621Crossref PubMed Scopus (675) Google Scholar, 27Morgera S. Kraft A.K. Siebert G. et al.Long-term outcomes in acute renal failure patients treated with continuous renal replacement therapies.Am J Kidney Dis. 2002; 40: 275-279Abstract Full Text Full Text PDF PubMed Scopus (216) Google Scholar, 28Cosentino F. Chaff C. Piedmonte M. Risk factors influencing survival in ICU acute renal failure.Nephrol Dial Transplant. 1994; 9: 179-182PubMed Google Scholar, 29Chertow G.M. Christiansen C.L. Cleary P.D. et al.Prognostic stratification in critically ill patients with acute renal failure requiring dialysis.Arch Intern Med. 1995; 155: 1505-1511Crossref PubMed Scopus (357) Google Scholar, 30Bernieh B. Al Hakim M. Boobes Y. et al.Outcome and predictive factors of acute renal failure in the intensive care unit.Transplant Proc. 2004; 36: 1784-1787Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar, 31Levy E.M. Viscoli C.M. Horwitz R.I. The effect of acute renal failure on mortality. A cohort analysis.JAMA. 1996; 275: 1489-1494Crossref PubMed Scopus (0) Google Scholar (Table 1). This high mortality persists despite aggressive overall ICU care and recent advances in renal replacement technology. Regarding long-term outcomes, an increased mortality attributable to AKI persists even after hospital discharge. However, the specific causes of out-of-hospital death have not been rigorously reported. Several articles make reference to the presence of comorbidities at the time of AKI, yet few comment on the contribution these comorbid illnesses had on mortality. Overall, long-term mortality and the associated causes of death have not been well studied.Table 1Long-Term Mortality After AKINumber of Patients Followed Long-Term∗Discharged alive.Average AgeInclusion CriteriaIn-Hospital Mortality†Original study cohort.Time of Follow-UpMortality at Study CompletionLiano et al, 200717Liano F. Felipe C. Tenorio M.T. et al.Long-term outcome of acute tubular necrosis: A contribution to its natural history.Kidney Int. 2007; 71: 679-686Crossref PubMed Scopus (115) Google Scholar187 (10 lost to follow-up)57.8All AKI; CKD excluded55%10 yearsTrauma 16%‖Excludes in-hospital mortality (mortality rate of survivors only) surgical 47%‖Excludes in-hospital mortality (mortality rate of survivors only) medical 56%‖Excludes in-hospital mortality (mortality rate of survivors only)Lins et al, 200637Lins R.L. Elseviers M.M. Daelemans R. Severity scoring and mortality 1 year after acute renal failure.Nephrol Dial Transplant. 2006; 21: 1066-1068Crossref PubMed Scopus (41) Google Scholar14568AKI (SCr >2 mg/dL); CKD excluded51%1 year62%§Includes in-hospital mortality (overall mortality rate).; 22%‖Excludes in-hospital mortality (mortality rate of survivors only)Ahlstrom et al, 200551Ahlstrom A. Tallgren M. Peltonen S. et al.Survival and quality of life of patients requiring acute renal replacement therapy.Intensive Care Med. 2005; 31: 1222-1228Crossref PubMed Scopus (147) Google Scholar40456AKI requiring RRT; Previous CKD ND41%1 year 5 year57%§Includes in-hospital mortality (overall mortality rate).; 70%§Includes in-hospital mortality (overall mortality rate).Bagshaw et al, 200516Bagshaw S.M. Laupland K.B. Doig C.J. et al.Prognosis for long-term survival and renal recovery in critically ill patients with severe acute renal failure: A population-based study.Crit Care. 2005; 9: R700-R709Crossref PubMed Google Scholar12066AKI requiring RRT; CKD not excluded60%1 year64%§Includes in-hospital mortality (overall mortality rate).Loef et al, 200511Loef B.G. Epema A.H. Smilde T.D. et al.Immediate postoperative renal function deterioration in cardiac surgical patients predicts in-hospital mortality and long-term survival.J Am Soc Nephrol. 2005; 16: 195-200Crossref PubMed Scopus (389) Google Scholar14564.7All AKI; ESKD excluded14.5%100 months38%‖Excludes in-hospital mortality (mortality rate of survivors only)Leacche et al, 200418Leacche M. Rawn J.D. Mihaljevic T. et al.Outcomes in patients with normal serum creatinine and with artificial renal support for acute renal failure developing after coronary artery bypass grafting.Am J Cardiol. 2004; 93: 353-356Abstract Full Text Full Text PDF PubMed Scopus (67) Google Scholar1169.5AKI requiring RRT; CKD excluded72%‡Operative mortality defined as death from any cause occurring within 30 days after surgery or during same hospitalization.1 year90%§Includes in-hospital mortality (overall mortality rate).; 63%‖Excludes in-hospital mortality (mortality rate of survivors only)Morgera et al, 200227Morgera S. Kraft A.K. Siebert G. et al.Long-term outcomes in acute renal failure patients treated with continuous renal replacement therapies.Am J Kidney Dis. 2002; 40: 275-279Abstract Full Text Full Text PDF PubMed Scopus (216) Google Scholar26758.5AKI requiring RRT; Previous CKD ND69%159 to 2,653 days37%‖Excludes in-hospital mortality (mortality rate of survivors only)Korkeila et al, 200019Korkeila M. Ruokonen E. Takala J. Costs of care, long-term prognosis and quality of life in patients requiring renal replacement therapy during intensive care.Intensive Care Med. 2000; 26: 1824-1831Crossref PubMed Scopus (183) Google Scholar6256.3AKI requiring RRT; ESKD excluded45%6 months 5 year55%§Includes in-hospital mortality (overall mortality rate).; 65%§Includes in-hospital mortality (overall mortality rate).Abbreviations: ND, not described; AKI, acute kidney injury; CKD, chronic kidney disease; RRT, renal replacement therapy; ESKD, end-stage kidney disease.∗ Discharged alive.† Original study cohort.‡ Operative mortality defined as death from any cause occurring within 30 days after surgery or during same hospitalization.§ Includes in-hospital mortality (overall mortality rate).|| Excludes in-hospital mortality (mortality rate of survivors only) Open table in a new tab Abbreviations: ND, not described; AKI, acute kidney injury; CKD, chronic kidney disease; RRT, renal replacement therapy; ESKD, end-stage kidney disease. Between approximately 1950 and 1980, in-hospital AKI mortality rates were reported to be 21% to 68%, and long-term survival (1-10 years) ranged from 50% to 70%.32Turney J.H. Ellis C.M. Parsons F.M. Obstetric acute renal failure 1956-1987.Br J Obstet Gynaecol. 1989; 96: 679-687Crossref PubMed Scopus (42) Google Scholar, 33Frost L. Pedersen R.S. Bentzen S. et al.Short and long term outcome in a consecutive series of 419 patients with acute dialysis-requiring renal failure.Scand J Urol Nephrol. 1993; 27: 453-462Crossref PubMed Scopus (38) Google Scholar, 34McCarthy J.T. Prognosis of patients with acute renal failure in the intensive-care unit: A tale of two eras.Mayo Clin Proc. 1996; 71: 117-126Abstract Full Text Full Text PDF PubMed Scopus (172) Google Scholar More recently, a few studies have re-examined the long-term outcomes of AKI, specifically mortality rates. In a retrospective review of 979 patients with AKI treated with continuous renal replacement therapy (CRRT) in Germany, the in-hospital mortality rate was 69% (n = 678), with 301 (31%) patients surviving to hospital discharge. Questionnaires were sent to all of the surviving patients. "Nonresponders" were investigated by a local registry office, insurance agency, or family doctor. Two hundred sixty-seven patients (89%) from the initial 301 survivors were included in the survival analysis. The median follow-up was 938 days (range, 159-2,653 days). The survival probability for the first 6 months after discharge was 77%. Patients surviving 6 months had a probability of 89% to survive the following 6 months. Overall, there was a 50% probability of death approximately 5 years after hospital discharge.27Morgera S. Kraft A.K. Siebert G. et al.Long-term outcomes in acute renal failure patients treated with continuous renal replacement therapies.Am J Kidney Dis. 2002; 40: 275-279Abstract Full Text Full Text PDF PubMed Scopus (216) Google Scholar Liano et al followed 177 AKI survivors for between 6 months and 22 years, the longest published duration of follow-up. The survival rates at 10 years for those age 1.4 mg/dL), 60% survival versus 43% at 10 years.17Liano F. Felipe C. Tenorio M.T. et al.Long-term outcome of acute tubular necrosis: A contribution to its natural history.Kidney Int. 2007; 71: 679-686Crossref PubMed Scopus (115) Google Scholar As shown in a large cohort of nonspecific critically ill patients, any degree of kidney dysfunction is associated with an increased risk of long-term death (1 year). Specifically, 5,693 adults admitted into the Calgary Health Region ICU system between 1999 and 2002 were stratified by severity of kidney dysfunction. Although a total of 6% of all patients (343) required RRT, only 4.2% (240) were included in the cohort (103 patients were excluded for chronic RRT, RRT requirements without critical illness, or RRT for toxin removal). Stratified by kidney function, crude case-fatality rates at 1 year were 17.3% for no AKI (n = 4,411, SCr <1.7 mg/dL), 47% for mild AKI (n = 790, SCr 1.7-3.4 mg/dL), 48% for moderate AKI (n = 160, SCr ≥3.4 mg/dL), 64% for severe AKI (n = 240, need for RRT), and 40% for end-stage kidney disease (ESKD).35Bagshaw S.M. Mortis G. Doig C.J. et al.One-year mortality in critically ill patients by severity of kidney dysfunction: A population-based assessment.Am J Kidney Dis. 2006; 48: 402-409Abstract Full Text Full Text PDF PubMed Scopus (104) Google Scholar Of note, the difference between mild and moderate AKI was not statistically significant. For these 240 patients who required RRT, the overall in-hospital mortality was 60%, increasing to 64% at 1 year. The 28-day, 90-day, and 1-year case-fatality rates were 51% (n = 123), 60% (n = 143), and 64% (n = 153), respectively. Approximately 19% of these 240 patients had a diagnosis of CKD (defined as a preexisting SCr of ≥1.7 mg/dL for at least 6 months before ICU admission). Of the original 240 patients requiring RRT in the ICU, only 87 were still alive at the 1-year follow-up.16Bagshaw S.M. Laupland K.B. Doig C.J. et al.Prognosis for long-term survival and renal recovery in critically ill patients with severe acute renal failure: A population-based study.Crit Care. 2005; 9: R700-R709Crossref PubMed Google Scholar An important limitation of this study is the absence of data regarding presence or absence of preexisting kidney disease and other comorbidities at each of the follow-up time points. It is therefore difficult to determine if the long-term mortality impact was different for those with or without preexisting kidney disease. These authors suggest that a minimum follow-up of 90 days is necessary given that, in their study, approximately 4% of mortality occurred between 90 days and 1 year.35Bagshaw S.M. Mortis G. Doig C.J. et al.One-year mortality in critically ill patients by seve
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