Long-term risk of mortality and acute kidney injury during hospitalization after major surgery. Ann Surg. 2009;249:851-858. [PMID: 19387314 DOI: 10.1097/sla.0b013e3181a40a0b]

Preventing acute kidney injury after noncardiac surgery

PURPOSE OF REVIEW

In surgical patients, outcome is strictly dependent on the occurrence of postoperative complications, and a postoperative failing kidney has a significant independent effect on outcome. Acute kidney injury (AKI) occurs in 1% of noncardiac surgical patients and is commonly associated with more serious complications. It is important to prevent AKI wherever possible.

RECENT FINDINGS

The mainstay of postoperative AKI prevention is perioperative maintenance of blood volume with adequate cardiac output by hemodynamic monitoring and fluids/inotropes infusion. There is a growing interest for pharmacological and metabolic interventions. Most interventions, however, have been predominantly evaluated in cardiac surgery and no definite conclusion can be translated in other settings. Tight control of glycemia is still matter of debate and a role, if any, may be limited to cardiac surgical patients.

SUMMARY

Adopting adequate nephroprotective strategies is favored by knowing the moment of the actual insult to the kidney. Nevertheless, in the literature too many areas of uncertainty still exist due to the lack of renal risk stratification, of adequately powered studies, of uniform AKI definition, and of appropriate sample composition. The only recommendation for renal protection still consists in maintaining an optimal blood volume and an adequate cardiac output.

Clinical accuracy of RIFLE and Acute Kidney Injury Network (AKIN) criteria for acute kidney injury in patients undergoing cardiac surgery

Introduction

The RIFLE (risk, injury, failure, loss of kidney function, and end-stage renal failure) classification for acute kidney injury (AKI) was recently modified by the Acute Kidney Injury Network (AKIN). The two definition systems differ in several aspects, and it is not clearly determined which has the better clinical accuracy.

Methods

In a retrospective observational study we investigated 4,836 consecutive patients undergoing cardiac surgery with cardiopulmonary bypass from 2005 to 2007 at Mayo Clinic, Rochester, MN, USA. AKI was defined by RIFLE and AKIN criteria.

Results

Significantly more patients were diagnosed as AKI by AKIN (26.3%) than by RIFLE (18.9%) criteria (P < 0.0001). Both definitions showed excellent association to outcome variables with worse outcome by increased severity of AKI (P < 0.001, all variables). Mortality was increased with an odds ratio (OR) of 4.5 (95% CI 3.6 to 5.6) for one class increase by RIFLE and an OR of 5.3 (95% CI 4.3 to 6.6) for one stage increase by AKIN. The multivariate model showed lower predictive ability of RIFLE for mortality. Patients classified as AKI in one but not in the other definition set were predominantly staged in the lowest AKI severity class (9.6% of patients in AKIN stage 1, 2.3% of patients in RIFLE class R). Potential misclassification of AKI is higher in AKIN, which is related to moving the 48-hour diagnostic window applied in AKIN criteria only. The greatest disagreement between both definition sets could be detected in patients with initial postoperative decrease of serum creatinine.

Conclusions

Modification of RIFLE by staging of all patients with acute renal replacement therapy (RRT) in the failure class F may improve predictive value. AKIN applied in patients undergoing cardiac surgery without correction of serum creatinine for fluid balance may lead to over-diagnosis of AKI (poor positive predictive value). Balancing limitations of both definition sets of AKI, we suggest application of the RIFLE criteria in patients undergoing cardiac surgery.

The prognostic importance of worsening renal function during an acute myocardial infarction on long-term mortality

BACKGROUND

Although an acute worsening in renal function (WRF) commonly occurs among patients hospitalized for acute myocardial infarction (AMI), its long-term prognostic significance is unknown. We examined predictors of WRF and its association with 4-year mortality.

METHODS

Acute myocardial infarction patients from the multicenter PREMIER study (N=2,098) who survived to hospital discharge were followed for at least 4 years. Worsening in renal function was defined as an increase in creatinine during hospitalization of ≥0.3 mg/dL above the admission value. Correlates of WRF were determined with multivariable logistic regression models and used, along with other important clinical covariates, in Cox proportional hazards models to define the independent association between WRF and mortality.

RESULTS

Worsening in renal function was observed in 393 (18.7%) of AMI survivors. Diabetes, left ventricular systolic dysfunction, and a history of chronic kidney disease (documented history of renal failure with baseline creatinine>2.5 mg/dL) were independently associated with WRF. During 4-year follow-up, 386 (18.6%) patients died. Mortality was significantly higher in the WRF group (36.6% vs 14.4% in those without WRF, P<.001). After adjusting for other factors associated with WRF and long-term mortality, including baseline creatinine, WRF was independently associated with a higher risk of death (hazard ratio=1.64, 95% CI 1.23-2.19).

CONCLUSIONS

Worsening in renal function occurs in approximately 1 of 6 AMI survivors and is independently associated with an adverse long-term prognosis. Further studies on interventions to minimize WRF or to more aggressively treat patients developing WRF should be tested.

Predictors of early and late mortality following open extent IV thoracoabdominal aortic aneurysm repair in a large contemporary single-center experience

OBJECTIVE

The primary purpose of this study was to examine outcomes following open repair of extent IV thoracoabdominal aortic aneurysms (TAAAs) at a single university hospital. As a secondary aim, comparison was made to patients who underwent open abdominal aortic aneurysm (AAA) repair with supraceliac clamping but without left renal artery bypass to assess the effect of left renal artery bypass on outcomes.

METHODS

Patients undergoing open extent IV TAAA repair from 1998 to 2008 were identified (n = 108). Primary outcomes were 30-day and long-term survival. Secondary outcomes were major complication, renal failure, and postoperative change in renal function. A second analysis was performed, comparing patients undergoing extent IV TAAA repair with patients undergoing AAA repair with supraceliac clamping but without left renal artery bypass (n = 50).

RESULTS

Eighty-three men (76.9%) and 25 women (23.1%), with a mean age of 72.9 years, underwent open extent IV TAAA repair. Nine patients (8.3%) were ruptured. Mean aneurysm maximal diameter was 6.5 ± 1.3 cm. Supraceliac and left renal ischemic times were 22.9 ± 9.3 and 40.6 ± 16.2 minutes, respectively. Six patients (5.6%) died at 30 days. The only predictor of 30-day mortality was decreased preoperative estimated glomerular filtration rate (eGFR) (P = .044 by multivariate analysis; and P = .011 by univariate analysis). One-year and 5-year survival rates were 87% and 50%, respectively. Patients with a history of cerebrovascular disease (P = .001) and postoperative renal insufficiency (P = .034) had increased long-term mortality by log-rank test. Twenty-five (25.3%) patients sustained a postoperative decrease in renal function, while 19 (19.2%) patients had an improvement in renal function. There was no difference in 30-day mortality (5.6% vs 6.0%; P = 1.000), 5-year survival (50% vs 48%; P = .886), major complications (37.0% vs 38.0%; P = 1.000), renal failure (6.1% vs 0%; P = .215), or postoperative change in renal function, in patients undergoing extent IV TAAA repair vs AAA repair with supraceliac clamping but without left renal artery bypass.

CONCLUSIONS

Open extent IV TAAA repair can be performed with low morbidity and mortality rates. The performance of left renal artery bypass does not appear to contribute to the morbidity and mortality of extent IV TAAA repair. While decreased preoperative eGFR appears to increase the risk of 30-day mortality, a history of cerebrovascular disease and postoperative renal insufficiency appear to increase the risk of long-term mortality. Finally, open extent IV TAAA repair not uncommonly improves renal function.

Duration of acute kidney injury impacts long-term survival after cardiac surgery

BACKGROUND

Acute kidney injury (AKI) after cardiac surgery is associated with worse outcomes. However, it is not known how adverse long-term consequences vary according to the duration of AKI. We sought to determine the association between duration of AKI and survival.

METHODS

Medical records of 4,987 cardiac surgery patients from 2002 through 2007 with serum creatinine (SCr) collection at a medical center in northern New England were reviewed. Acute kidney injury was defined as at least a 0.3 (mg/dL) or at least a 50% increase in SCr from baseline and further classified into AKI Network stages. Duration of AKI was defined by the number of days AKI was present and categorized as no AKI and AKI for 1 to 2, 3 to 6, and at least 7 days.

RESULTS

Thirty-nine percent of patients exhibited AKI. Long-term survival was significantly different by AKI duration (p < 0.001). The proportion of patients with AKI duration, adjusted hazard ratio, and 95% confidence interval for mortality (no AKI as referent) were as follows: 1 to 2 days (18%; adjusted hazard ratio, 1.66; 95% confidence interval, 1.32 to 2.09), 3 to 6 days (11%; adjusted hazard ratio, 1.94; 95% confidence interval, 1.51 to 2.49), ≥7 days (9%; adjusted hazard ratio, 3.40; 95% confidence interval, 2.73 to 4.25). This graded relationship of duration of AKI with long-term mortality persisted when patients who died during hospitalization were excluded from analysis (p < 0.001). Propensity-matched analysis confirmed results.

CONCLUSIONS

The duration of AKI after cardiac surgery is directly proportional to long-term mortality. This AKI dose-dependent effect on long-term mortality helps to close the gap between association and causation, whereby AKI stages and AKI duration have important implications for patient care and can aid clinicians in evaluating the risk of in-hospital and postdischarge death.

The assessment, serial evaluation, and subsequent sequelae of acute kidney injury (ASSESS-AKI) study: design and methods

Background

The incidence of acute kidney injury (AKI) has been increasing over time and is associated with a high risk of short-term death. Previous studies on hospital-acquired AKI have important methodological limitations, especially their retrospective study designs and limited ability to control for potential confounding factors.

Methods

The Assessment, Serial Evaluation, and Subsequent Sequelae of Acute Kidney Injury (ASSESS-AKI) Study was established to examine how a hospitalized episode of AKI independently affects the risk of chronic kidney disease development and progression, cardiovascular events, death, and other important patient-centered outcomes. This prospective study will enroll a cohort of 1100 adult participants with a broad range of AKI and matched hospitalized participants without AKI at three Clinical Research Centers, as well as 100 children undergoing cardiac surgery at three Clinical Research Centers. Participants will be followed for up to four years, and will undergo serial evaluation during the index hospitalization, at three months post-hospitalization, and at annual clinic visits, with telephone interviews occurring during the intervening six-month intervals. Biospecimens will be collected at each visit, along with information on lifestyle behaviors, quality of life and functional status, cognitive function, receipt of therapies, interim renal and cardiovascular events, electrocardiography and urinalysis.

Conclusions

ASSESS-AKI will characterize the short-term and long-term natural history of AKI, evaluate the incremental utility of novel blood and urine biomarkers to refine the diagnosis and prognosis of AKI, and identify a subset of high-risk patients who could be targeted for future clinical trials to improve outcomes after AKI.

Fenoldopam use in a burn intensive care unit: a retrospective study

BACKGROUND

Fenoldopam mesylate is a highly selective dopamine-1 receptor agonist approved for the treatment of hypertensive emergencies that may have a role at low doses in preserving renal function in those at high risk for or with acute kidney injury (AKI). There is no data on low-dose fenoldopam in the burn population. The purpose of our study was to describe our use of low-dose fenoldopam (0.03-0.09 mug/kg/min) infusion in critically ill burn patients with AKI.

METHODS

We performed a retrospective analysis of consecutive patients admitted to our burn intensive care unit (BICU) with severe burns from November 2005 through September 2008 who received low-dose fenoldopam. Data obtained included systolic blood pressure, serum creatinine, vasoactive medication use, urine output, and intravenous fluid. Patients on concomitant continuous renal replacement therapy were excluded. Modified inotrope score and vasopressor dependency index were calculated. One-way analysis of variance with repeated measures, Wilcoxson signed rank, and chi-square tests were used. Differences were deemed significant at p < 0.05.

RESULTS

Seventy-seven patients were treated with low-dose fenoldopam out of 758 BICU admissions (10%). Twenty (26%) were AKI network (AKIN) stage 1, 14 (18%) were AKIN stage 2, 42 (55%) were AKIN stage 3, and 1 (1%) was AKIN stage 0. Serum creatinine improved over the first 24 hours and continued to improve through 48 hours (p < 0.05). There was an increase in systolic blood pressure in the first 24 hours that was sustained through 48 hours after initiation of fenoldopam (p < 0.05). Urine output increased after initiation of fenoldopam without an increase in intravenous fluid requirement (p < 0.05; p = NS). Modified inotrope score and vasopressor dependency index both decreased over 48 hours (p < 0.0001; p = 0.0012).

CONCLUSIONS

These findings suggest that renal function was preserved and that urine output improved without a decrease in systolic blood pressure, increase in vasoactive medication use, or an increase in resuscitation requirement in patients treated with low-dose fenoldopam. A randomized controlled trial is required to establish the efficacy of low-dose fenoldopam in critically ill burn patients with AKI.

Inhaled carbon monoxide prevents acute kidney injury in pigs after cardiopulmonary bypass by inducing a heat shock response

BACKGROUND

Cardiopulmonary bypass (CPB) may be associated with acute kidney injury (AKI). Inhaled carbon monoxide (CO) is cyto- and organ-protective. We hypothesized that pretreatment with inhaled CO prevents CPB-associated AKI.

METHODS

Pigs (n = 38) were nonrandomly assigned to SHAM, standard CPB, pretreatment with inhaled CO (250 ppm, 1 hour) before SHAM or CPB, to pretreatment with quercetin (an inhibitor of the heat shock response), and to pretreatment with SnPPIX (an inhibitor of endogenously derived CO), before CO inhalation and CPB. The primary outcome variables were markers of AKI (urea, uric acid, creatinine, cystatin C, neutrophil gelatinase-associated lipocalin, interleukin-6, tumor necrosis factor-alpha), which were determined 120 minutes after CPB. Secondary outcome variables were heat shock protein (HSP)-70 and heme oxygenase-1 protein expressions as indicators of CO-mediated heat shock response.

RESULTS

Pretreatment with inhaled CO attenuated (all P < 0.001) CPB-associated, (1) increases in serum concentrations of cystatin C (64 +/- 14 vs 28 +/- 9 ng/mL), neutrophil gelatinase-associated lipocalin (391 +/- 65 vs 183 +/- 56 ng/mL), renal tumor necrosis factor-alpha (450 +/- 73 vs 179 +/- 110 pg/mL), and interleukin-6 (483 +/- 102 vs 125 +/- 67 pg/mL); (2) increase in renal caspase-3 activity (550 +/- 66 vs 259 +/- 52 relative fluorescent units); and (3) histological evidence of AKI. These effects were accompanied by activation of HSP-70 (196 +/- 64 vs 554 +/- 149 ng/mL, P < 0.001). Pretreatment with the heat shock response inhibitor quercetin counteracted the CO-associated biochemical and histological renoprotective effects (all P < 0.001), whereas the heme oxygenase inhibitor SnPPIX only partially counteracted the CO-associated renoprotection and the activation of the heat shock response.

CONCLUSIONS

CO treatment before CPB was associated with evidence of renoprotection, demonstrated by fewer histological injuries and decreased cystatin C concentrations. The findings that the antiinflammatory and antiapoptotic effects of CO were accompanied by activation of HSP-70, which in turn were reversed by quercetin, suggest that renoprotection by pretreatment with inhaled CO before CPB is mediated by activation of the renal heat shock response.

Acute kidney injury in elderly persons

The incidence rate of acute kidney injury (AKI) is highest in elderly patients, who make up an ever-growing segment of the population at large. AKI in these patients is associated with an increased risk of short- and long-term death and chronic kidney disease, including end-stage renal disease. Whether AKI in older individuals carries a larger relative risk for these outcomes compared with younger individuals is unclear at this time. Other domains, such as health-related quality of life, may be mildly impacted on after an episode of AKI. No effective therapies for AKI currently are available for widespread use. However, because the incidence of AKI is highest in the elderly and the phenotype is not discernibly different from AKI in all populations, future randomized controlled trials of interventions for AKI should be performed in the elderly population.

Open surgical repair of ruptured juxtarenal aortic aneurysms with and without renal cooling: observations regarding morbidity and mortality

OBJECTIVES

Little is known about the outcome of ruptured juxtarenal aortic aneurysm (RJAA) repair. Surgical treatment of RJAAs requires suprarenal aortic cross-clamping, which causes additional renal ischemia-reperfusion injury on top of the pre-existing hypovolemic shock syndrome. As endovascular alternatives rarely exist in this situation, open repair continues to be the gold standard. We analyzed our results of open RJAA repair during an 11-year period.

DESIGN

Retrospective observational study.

MATERIALS AND METHODS

Between July 1997 and December 2008, all consecutive patients with RJAAs were included in the study. Part of these patients received cold perfusion of the kidneys during suprarenal aortic cross-clamping. Perioperative variables, morbidity, and 30-day or in-hospital mortality were assessed. Renal insufficiency was defined as an acute rise of >or=0.5 mg/dL in serum creatinine level. Multiple organ failure (MOF) was scored using the sequential organ failure assessment score (SOFA score).

RESULTS

A total of 29 consecutive patients with an RJAA, confirmed by computed tomography-scanning, presented to our hospital. In eight patients, the operation was aborted before the start of aortic repair, because no blood pressure could be regained in spite of maximal resuscitation measures. They were excluded from further analysis. Of the remaining 21 patients, 10 died during hospital stay. Renal insufficiency occurred in 11 out of 21 of the patients. Eleven out of 21 patients developed MOF postoperatively. In a subgroup of patients who received renal cooling during suprarenal aortic clamping, the 30-day or in-hospital mortality was two of 10 vs eight of 11 in patients who did not receive renal cooling (P = .03); renal insufficiency occurred in one out of 10 patients in the subgroup with renal cooling vs 10 out of 11 without renal cooling (P < .001) and MOF in two of 10 vs nine of 11, respectively (P = .009).

CONCLUSIONS

Open surgical repair of RJAAs is still associated with high mortality and morbidity. To our knowledge, this is the first report of cold perfusion of the kidneys during RJAA repair. Although numbers are small, a beneficial effect of renal cooling on the outcome of RJAA repair is suggested, warranting further research with this technique.

Acute kidney injury in non-severe pneumonia is associated with an increased immune response and lower survival

While sepsis is a leading cause of acute kidney injury in critically ill patients, the relationship between immune response and acute kidney injury in less severely ill patients with infection is not known. Here we studied the epidemiology, 1-year mortality, and immune response associated with acute kidney injury in 1836 hospitalized patients with community-acquired severe and non-severe pneumonia. Acute kidney injury developed in 631 patients of whom 329 had severe and 302 had non-severe sepsis. Depending on the subgroup classification, 16-25% of the patients with non-severe pneumonia also developed acute kidney injury. In general, patients with acute kidney injury were older, had more comorbidity, and had higher biomarker concentrations (interleukin-6, tumor necrosis factor, D-dimer) even among patients without severe sepsis. The risk of death associated with acute kidney injury varied when assessed by Gray's survival model and after adjusting for differences in age, gender, ethnicity, and comorbidity. This risk was significantly higher immediately after hospitalization but gradually fell over time in the overall cohort and in those with non-severe pneumonia. A significantly higher risk of death (hazard ratio 1.29) was also present in those never admitted to an intensive care unit. Hence acute kidney injury is common even among patients with non-severe pneumonia and is associated with higher immune response and an increased risk of death.