Prevention of perioperative acute renal failure: what works?

Machine learning approach to predict acute kidney injury after liver surgery

BACKGROUND

Acute kidney injury (AKI) after surgery appears to increase the risk of death in patients with liver cancer. In recent years, machine learning algorithms have been shown to offer higher discriminative efficiency than classical statistical analysis.

AIM

To develop prediction models for AKI after liver cancer resection using machine learning techniques.

METHODS

We screened a total of 2450 patients who had undergone primary hepatocellular carcinoma resection at Changzheng Hospital, Shanghai City, China, from January 1, 2015 to August 31, 2020. The AKI definition used was consistent with the Kidney Disease: Improving Global Outcomes. We included in our analysis preoperative data such as demographic characteristics, laboratory findings, comorbidities, and medication, as well as perioperative data such as duration of surgery. Computerized algorithms used for model development included logistic regression (LR), support vector machine (SVM), random forest (RF), extreme gradient boosting (XGboost), and decision tree (DT). Feature importance was also ranked according to its contribution to model development.

RESULTS

AKI events occurred in 296 patients (12.1%) within 7 d after surgery. Among the original models based on machine learning techniques, the RF algorithm had optimal discrimination with an area under the curve value of 0.92, compared to 0.87 for XGBoost, 0.90 for DT, 0.90 for SVM, and 0.85 for LR. The RF algorithm also had the highest concordance-index (0.86) and the lowest Brier score (0.076). The variable that contributed the most in the RF algorithm was age, followed by cholesterol, and surgery time.

CONCLUSION

Machine learning algorithms are highly effective in discriminating patients at high risk of developing AKI. The successful application of machine learning models may help guide clinical decisions and help improve the long-term prognosis of patients.

The impact of intraoperative bleeding on the risk of chronic kidney disease after nephron-sparing surgery

PURPOSE

The current literature regarding the effect of blood loss (eBL) after nephron-sparing surgery (NSS) on long-term renal function is scarce. We tested the effect of eBL on the risk of developing chronic kidney disease (CKD) after NSS.

METHODS

Within an institutional prospectively maintained database, we identified 215 patients treated with NSS for cT₁N₀M₀ renal mass at one European high-volume center. Multivariable logistic regression models tested the effect of eBL on the risk of developing CKD, after accounting for surgical complexity, individual clinical characteristics, and surgical experience. Multivariable linear regression models identified predictors of eBL.

RESULTS

After a median follow-up of 36 months, 55 (25.6%) patients experienced CKD after surgery. At multivariable analyses, eBL independently predicted higher risk of CKD after NSS (odds ratio [OR]: 1.16; 95% confidence intervals [CI] 1.04-1.30; p < 0.01). Specifically, the relationship between eBL and probability of CKD emerged as nonlinear, with a plateau from 0 to 500 mL of eBL and an increase afterward. When multivariable linear regression analyses investigated predictors of eBL, hypertension (Est: 127, 95% CI 12-242; p = 0.03), clinical size (Est: 47, 95% CI 7-87; p = 0.02), and PADUA score (Est: 42; 95% CI 4-80 p = 0.03) achieved independent predictor status for higher intraoperative eBL. Conversely, surgical experience was associated with lower eBL (p = 0.01).

CONCLUSIONS

Intraoperative bleeding is independently associated with the risk of developing CKD after surgery, even after adjustment for well-known predictors of renal failure and tumor complexity. Hence, strategies aimed at maximally reducing such adverse events deserve special consideration.

A comparative study of machine learning algorithms for predicting acute kidney injury after liver cancer resection

Objective

Machine learning methods may have better or comparable predictive ability than traditional analysis. We explore machine learning methods to predict the likelihood of acute kidney injury after liver cancer resection.

Methods

This is a secondary analysis cohort study. We reviewed data from patients who had undergone resection of primary hepatocellular carcinoma between January 2008 and October 2015.

Results

The analysis included 1,173 hepatectomy patients, 77 (6.6%) of whom had AKI and 1,096 (93.4%) who did not. The importance matrix for the Gbdt algorithm model shows that age, cholesterol, tumor size, surgery duration and PLT were the five most important parameters. Figure 1 shows that Age, tumor size and surgery duration had weak positive correlations with AKI. Cholesterol and PLT also had weak negative correlations with AKI. The models constructed by the four machine learning algorithms in the training group were compared. Among the four machine learning algorithms, random forest and gbm had the highest accuracy, 0.989 and 0.970 respectively. The precision of four of the five algorithms was 1, random forest being the exception. Among the test group, gbm had the highest accuracy (0.932). Random forest and gbm had the highest precision, both being 0.333. The AUC values for the four algorithms were: Gbdt (0.772), gbm (0.725), forest (0.662) and DecisionTree (0.628).

Conclusions

Machine learning technology can predict acute kidney injury after hepatectomy. Age, cholesterol, tumor size, surgery duration and PLT influence the likelihood and development of postoperative acute kidney injury.

Hemodynamically adjusted infrahepatic inferior venous cava clamping can reduce postoperative deterioration in renal function: a retrospective observational study

PURPOSE

Infrahepatic inferior vena cava (IIVC) clamping is beneficial for reducing the amount of bleeding during hepatic surgery, although the associated systemic circulatory deterioration is noticeable. The relationship between changes in the degree of IIVC clamping and postoperative renal function was retrospectively evaluated.

METHODS

A total of 59 patients who underwent elective hepatic surgery with surgical IIVC clamping in the two years were analyzed. In 2016, constant 80% clamping of the IIVC was performed (29 cases), and in 2017, hemodynamically adjusted IIVC clamping was performed (30 cases). Intraoperative parameters, including total blood loss and number of blood transfusions, were examined. The use of each vasoactive agents was analyzed. Renal function in the acute postoperative phase was evaluated using serum creatinine (Cr) and estimated glomerular filtration rate (eGFR) values.

RESULTS

Comparison of the two groups showed that bolus doses of both ephedrine and phenylephrine were significantly higher in the 2016 group (P = 0.0221, 0.0017). Continuous doses of dopamine were significantly higher in the 2016 group, while those of noradrenaline were not. Postoperative serum Cr levels relative to baseline (%) were significantly higher in the 2016 group immediately after surgery and on postoperative day (POD) 1 (P = 0.0143, 0.0012). Postoperative eGFR relative to baseline (%) was significantly higher in the 2016 group immediately postoperatively and on PODs 1 and 2 (P = 0.0042, 0.0003, 0.0382).

CONCLUSION

Hemodynamically adjustable IIVC clamping might be superior to uniformly fixed clamping in preserving renal function without compromising the desired effect on hemostasis.

Vascular Adhesion Protein-1 Is Associated With Acute Kidney Injury in High-Risk Patients After Cardiac Surgery

BACKGROUND

Acute kidney injury is a common complication after cardiac surgery, with a high impact on morbidity and mortality. Vascular adhesion protein-1 is involved in inflammation, which, in turn, is part of the development of acute kidney injury after cardiac surgery.

METHODS

In this ancillary study to the RENal effects of Remote Ischemic Preconditioning in cardiac surgery trial, we investigated whether vascular adhesion protein-1 might be associated with the development of acute kidney injury in high-risk patients after cardiac surgery. In total, 114 patients were included in this data set. Acute kidney injury was defined by the Kidney Disease: Improving Global Outcomes criteria serum creatinine and/or urine output. Vascular adhesion protein-1 concentrations were measured at baseline (before surgery), 4 hours, and 12 hours after cardiopulmonary bypass.

RESULTS

Vascular adhesion protein-1 levels at 12 hours were significantly higher in patients with acute kidney injury (no acute kidney injury, 271 ng/mL [Q1, Q3, 179, 364 ng/mL] versus acute kidney injury, 384 ng/mL [Q1, Q3, 311, 478 ng/mL]; P < .001). Moreover, patients developing acute kidney injury had higher differences in vascular adhesion protein-1 levels between 12 hours and baseline (P < .001) and between 12 and 4 hours (P < .001) after cardiopulmonary bypass. At a cut point difference value of 99 ng/mL (95% CI, 63-133) between 12 hours and baseline, patients with differences >99 ng/mL showed a higher occurrence rate of acute kidney injury (acute kidney injury, 78.6% versus no acute kidney injury, 31.5%; P < .001). Receiver-operating characteristic curve analyses demonstrated best performance for vascular adhesion protein-1 levels at 12 hours for acute kidney injury within 72 hours after surgery, especially in the subgroup of patients with chronic kidney disease (area under the receiver-operating characteristic curve, 0.78; P < .001).

CONCLUSIONS

Vascular adhesion protein-1 is elevated in patients developing acute kidney injury assuming that vascular adhesion protein-1 plays a crucial role in the development of acute kidney injury in high-risk patients after cardiac surgery.

Early postoperative change in serum creatinine predicts acute kidney injury after cardiothoracic surgery: a retrospective cohort study

BACKGROUND

Acute kidney injury (AKI) is one of the most severe complications after cardiothoracic surgery (CTS). However, diagnosis of AKI by elevation of serum creatinine (SCr) misses a critical time period for prevention and treatment of AKI. We have observed that patients who develop AKI show a smaller SCr decrease after CTS than those without AKI. Hence, we hypothesized that the magnitude of the SCr change (ΔSCr) measured early after CTS can predict subsequent AKI.

METHODS

We conducted a retrospective analysis from January 2014 to December 2016 to examine the association of ΔSCr with AKI. ΔSCr was calculated as follows: (early postoperative SCr on intensive care unit [ICU] admission) - (preoperative SCr). Established risk factors and demographics were included in the multivariate-adjusted logistic regression model. AKI was defined by SCr criteria of the Kidney Disease: Improving Global Outcomes group.

RESULTS

Among 252 patients who underwent CTS, 69 developed AKI. The median ΔSCr was - 0.14 mg/dL (range - 0.96-0.45). Patients were divided into three groups based on ΔSCr: Group 1, ≤ - 0.2 mg/dL (n = 84); Group 2, > - 0.2 to < - 0.1 mg/dL (n = 76); and Group 3, ≥ - 0.1 mg/dL (n = 92). In the multivariate analysis, Group 3 had a significantly higher incidence of AKI than Group 1 (odds ratio, 7.34; 95% confidence interval 2.55-23.3). ΔSCr was an independent risk factor for AKI (odds ratio for every 0.1-mg/dL increase in ΔSCr, 1.55; 95% confidence interval 1.23-1.97).

CONCLUSIONS

A minor change in the SCr level early after CTS can predict subsequent AKI just after ICU admission.

Influence of chlorpromazine on renal histology of rats submitted to ischemia and reperfusion injury

PURPOSE:

To analyze the influence of chlorpromazine on renal histology of rats submitted to ischemia and reperfusion injury.

METHODS:

Sixteen Wistar rats - split in two groups - have been used: control group, receiving 3 mg/kg isotonic saline solution through caudal vein, and, the chlorpromazine group, receiving 3 mg/kg-IV of such medication. The nephrectomy of the left kidney lower third was carried out; immediately, the test-drug was administrated. After 15 minutes of test-drug administration, the renal pedicle was clamped; in 60 minutes of ischemia it was released. After 24 hours of the renal reperfusion, the rats were, once more, anesthetized and submitted to total left nephrectomy, and, afterwards, to euthanasia. Histological findings regarding ischemia have been evaluated and compared between the groups.

RESULTS:

There was no statistical difference related to inferior renal pole histological analysis. Regarding 60-minute renal ischemia, chlorpromazine has statistically reduced the accrual of leucocytes within the vasa recta renis (p=0.036) and the congestion of peritubular capillaries (p=0.041). When conducting joint analysis of histological patterns, the control group showed a median score of 11 and chlorpromazine group of 5.5 (p=0.036).

CONCLUSION:

Chlorpromazine significantly reduced the occurrence of secondary damage to ischemia and reperfusion process in the overall histological analysis.

Effects of acute kidney injury after liver resection on long-term outcomes

Background

To investigate the effects of acute kidney injury (AKI) after liver resection on the long-term outcome, including mortality and renal dysfunction after hospital discharge.

Methods

We conducted a historical cohort study of patients who underwent liver resection for hepatocellular carcinoma with sevoflurane anesthesia between January 2004 and October 2011, survived the hospital stay, and were followed for at least 3 years or died within 3 years after hospital discharge. AKI was diagnosed based on the Acute Kidney Injury Network classification within 72 hours postoperatively. In addition to the data obtained during hospitalization, serum creatinine concentration data were collected and the glomerular filtration rate (GFR) was estimated after hospital discharge.

Results

AKI patients (63%, P = 0.002) were more likely to reach the threshold of an estimated GFR (eGFR) of 45 ml/min/1.73 m² within 3 years than non-AKI patients (31%) although there was no significant difference in mortality (33% vs. 29%). Cox proportional hazard regression analysis showed that postoperative AKI was significantly associated with the composite outcome of mortality or an eGFR of 45 ml/min/1.73 m² (95% CI of hazard ratio, 1.05–2.96, P = 0.033), but not with mortality (P = 0.699), the composite outcome of mortality or an eGFR of 60 ml/min/1.73 m² (P =0.347).

Conclusions

After liver resection, AKI patients may be at higher risk of mortality or moderate renal dysfunction within 3 years. These findings suggest that even after discharge from the hospital, patients who suffered AKI after liver resection may need to be followed-up regarding renal function in the long term.

Algorithm-guided goal-directed haemodynamic therapy does not improve renal function after major abdominal surgery compared to good standard clinical care: a prospective randomised trial

BACKGROUND

Acute kidney injury is a common complication after major surgery. In this study, we investigated whether an algorithm-guided goal-directed haemodynamic therapy (GDT) can improve renal outcome compared to good standard clinical care.

METHODS

A total of 180 patients undergoing major abdominal surgery were prospectively and randomly assigned to one of two groups: in the GDT group, patients were treated with a GDT algorithm using transpulmonary thermodilution while standard care was applied to the control patients. Change in creatinine was studied as the primary end point, postoperative complications as well as 1-year mortality as secondary outcomes. Haemodynamics in GDT and control patients were compared calculating goal-achievement rates.

RESULTS

Postoperative change in creatinine (18 ± 39 μmol/l (control) vs. 16 ± 42 μmol/l (GDT); mean difference (95 % confidence interval) 1.6 μmol/l (-10 to 13 μmol/l)) was comparable between the GDT and the control group. Postoperative complications and mortality during hospital stay and after 1 year were not influenced by the use of a GDT algorithm. Achievement rates of haemodynamic goals were not higher in the GDT group compared to the already high (>80 %) rates in the control group. Multivariate regression analysis revealed intraoperative hypotension (MAP < 70 mmHg) and postoperative hypovolaemia (GEDI < 640 ml/m(2)) as risk factors for postoperative renal impairment.

CONCLUSIONS

In this study, GDT was not superior to standard clinical care in order to avoid renal failure after major abdominal surgery. The reason for this finding is most likely the high achievement rate of haemodynamic goals in the control group, which cannot be improved by the GDT algorithm.

TRIAL REGISTRATION

Clinicaltrials.gov; NCT01035541; registered 17 December 2009.

Fenoldopam to prevent acute kidney injury after major surgery-a systematic review and meta-analysis

Background

Acute kidney injury (AKI) after surgery is associated with increased mortality and healthcare costs. Fenoldopam is a selective dopamine-1 receptor agonist with renoprotective properties. We conducted a systematic review and meta-analysis of randomised controlled trials comparing fenoldopam with placebo to prevent AKI after major surgery.

Methods

We searched EMBASE, PubMed, meta-Register of randomised controlled trials and Cochrane CENTRAL databases for trials comparing fenoldopam with placebo in patients undergoing major surgery. The primary outcome was incidence of new AKI. Secondary outcomes were requirement for renal replacement therapy and hospital mortality.

Results

Eighty-three publications were screened; 23 studies underwent full data extraction and scoring. Six trials were suitable for inclusion in the data synthesis (total of 507 subjects undergoing cardiovascular surgery, partial nephrectomy, liver transplant surgery). Five studies were rated at high risk of bias. Data on post-operative incidence of AKI were available in five of the six trials (total of 471 patients) but definitions of AKI varied between studies. Of the 238 patients receiving fenoldopam, 45 (18.9 %) developed AKI compared to 62 (26.6 %) of the 233 patients who received placebo (p = 0.004, I² = 0 %; random-effects model odds ratio 0.46, 95 % confidence interval 0.27–0.79). In patients treated with fenoldopam, there was no difference in renal replacement therapy (n = 478; p = 0.11, I² = 47 %; fixed-effect model odds ratio 0.27, 95 % confidence interval 0.06–1.19) or hospital mortality (p = 0.60, I² = 0 %; fixed-effect model odds ratio 1.0, 95 % confidence interval 0.14–7.37).

Conclusions

In this analysis, peri-operative treatment with fenoldopam was associated with a significant reduction in post-operative AKI but it had no impact on renal replacement therapy or hospital mortality. Equipoise remains for further large trials in this area since the studies were conducted in three types of surgery, the majority of studies were rated at high risk of bias and the criteria for AKI varied between trials.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-1166-4) contains supplementary material, which is available to authorized users.

Perioperative risk factors for acute kidney injury after liver resection surgery: an historical cohort study

PURPOSE

This study aimed to identify the incidence and risk factors for acute kidney injury (AKI) after liver resection surgery and to clarify the relationship between postoperative AKI and outcome.

METHODS

We conducted a historical cohort study of patients who underwent liver resection surgery with sevoflurane anesthesia from January 2004 to October 2011. Acute kidney injury was diagnosed based on the Acute Kidney Injury Network classification within 72 hr after the surgery. Patient data, surgical and anesthetic data, and laboratory data were extracted manually from the patients' electronic charts. Multivariable logistic regression analysis was used to identify perioperative risk factors for postoperative AKI.

RESULTS

Acute kidney injury was diagnosed in 78 of 642 patients (12.1%; 95% confidence interval [CI]: 9.7 to 14.9). Multivariable analysis showed an independent association between postoperative AKI and preoperative estimated glomerular filtration rate (adjusted odds ratio [aOR] 0.74; 95% CI: 0.64 to 0.85), preoperative hypertension (aOR 2.10; 95% CI: 1.11 to 3.97), and intraoperative red blood cell transfusion (aOR 1.04; 95% CI: 1.01 to 1.07). Development of AKI within 72 hr after liver resection surgery was associated with increased hospital mortality, prolonged length of stay, and increased rates of mechanical ventilation, reintubation, and renal replacement therapy.

CONCLUSION

Perioperative risk factors for AKI after liver resection surgery are similar to those established for other surgical procedures. Further studies are needed to establish causality and to determine whether interventions on modifiable risk factors can reduce the incidence of postoperative AKI and improve patient outcome. This study was registered at the University Hospital Medical Information Network (UMIN) Center (UMIN 000008089).

Urinary TIMP-2 and IGFBP7 as early biomarkers of acute kidney injury and renal recovery following cardiac surgery

BACKGROUND

Difficulties in prediction and early identification of (acute kidney injury) AKI have hindered the ability to develop preventive and therapeutic measures for this syndrome. We tested the hypothesis that a urine test measuring insulin-like growth factor-binding protein 7 (IGFBP7) and tissue inhibitor of metalloproteinases-2 (TIMP-2), both inducers of G1 cell cycle arrest, a key mechanism implicated in acute kidney injury (AKI), could predict AKI in cardiac surgery patients.

METHODS

We studied 50 patients at high risk for AKI undergoing cardiac surgery with cardiopulmonary bypass (CPB). Serial urine samples were analyzed for [TIMP-2]*[IGFBP7] concentrations. The primary outcome measure was AKI as defined by international consensus criteria following surgery. Furthermore, we investigated whether urine [TIMP-2]*[IGFBP7] could predict renal recovery from AKI prior to hospital discharge.

RESULTS

26 patients (52%) developed AKI. Diagnosis based on serum creatinine and/or oliguria did not occur until 1-3 days after CPB. In contrast, urine concentration of [TIMP-2]*[IGFBP7] rose from a mean of 0.49 (SE 0.24) at baseline to 1.51 (SE 0.57) 4 h after CPB in patients who developed AKI. The maximum urinary [TIMP-2]*[IGFBP7] concentration achieved in the first 24 hours following surgery (composite time point) demonstrated an area under the receiver-operating characteristic curve of 0.84. Sensitivity was 0.92, and specificity was 0.81 for a cutoff value of 0.50. The decline in urinary [TIMP-2]*[IGFBP7] values was the strongest predictor for renal recovery.

CONCLUSIONS

Urinary [TIMP-2]*[IGFBP7] serves as a sensitive and specific biomarker to predict AKI early after cardiac surgery and to predict renal recovery.

CLINICAL TRIAL REGISTRATION INFORMATION

www.germanctr.de/, DRKS-ID: DRKS00005062.

Suppression of renal TRPM7 may alleviate kidney injury in the renal transplantation

PURPOSE

The aim of this study was to investigate the effect of renal cortex transient receptor potential melastatin 7 (TRPM7) suppression on renal ischemia reperfusion injury induced by transplantation in mice.

METHODS

M7shRNA was used to decrease the expression of TRPM7 in NRK-52e cells. The mice were subjected to renal intra-parenchymal injection with lentivirus containing M7shRNA to produce hypo-expression of TRPM7 in renal cortex. Cell hypoxia mode and syngeneic renal transplantation in vivo were established. Then the effects of M7shRNA were measured by fluorescent probe for reactive oxygen species (ROS), intracellular calcium and magnesium; Western blot was applied for p38-MAPKs and Bax expression in cell studies. In vivo studies, mice were killed 24 h, 48 h, 72 h, 7 days and 21 days, respectively, after transplantation and the kidneys were dissected. Serum creatinine was measured, and the H&E, Masson's trichrome staining, TUNEL, Kim-1 and α-smooth muscle actin were used to evaluate pathological change.

RESULTS

In cell model of hypoxia, the level of ROS in NRK-52e-M7shRNA was significantly lower than that in both NRK-52e and NRK-52e control cells, while the activation of p38-MAPKs was limited. In renal transplanted mice, renal function of M7shRNA group was conspicuously better than PBS- and vector-control-treated group. The histological examination showed that renal tubule injury and interstitial fibrosis were lower in M7shRNA-treated group compared with PBS and vector-control group.

CONCLUSIONS

Suppression of renal cortex TRPM7 could alleviate kidney injury induced by transplantation in mice. The mechanism may involve reducing the early stage of ischemia reperfusion injury by inhibition of intracellular Ca(2+), Mg(2+) and ROS.

Acute kidney injury, renal function, and the elderly obese surgical patient: a matched case-control study

OBJECTIVE

To investigate the association between obesity and perioperative acute kidney injury (AKI), controlling for preoperative kidney dysfunction.

BACKGROUND

More than 30% of patients older than 60 years are obese and, therefore, at risk for kidney disease. Postoperative AKI is a significant problem.

METHODS

We performed a matched case-control study of patients enrolled in the Obesity and Surgical Outcomes Study, using data of Medicare claims enriched with detailed chart review. Each AKI patient was matched with a non-AKI control similar in procedure type, age, sex, race, emergency status, transfer status, baseline estimated glomerular filtration rate, admission APACHE score, and the risk of death score with fine balance on hospitals.

RESULTS

We identified 514 AKI cases and 694 control patients. Of the cases, 180 (35%) followed orthopedic procedures and 334 (65%) followed colon or thoracic surgery. After matching, obese patients undergoing a surgical procedure demonstrated a 65% increase in odds of AKI within 30 days from admission (odds ratio = 1.65, P < 0.005) when compared with the nonobese patients. After adjustment for potential confounders, the odds of postoperative AKI remained elevated in the elderly obese (odds ratio = 1.68, P = 0.01.)

CONCLUSIONS

: Obesity is an independent risk factor for postoperative AKI in patients older than 65 years. Efforts to optimize kidney function preoperatively should be employed in this at-risk population along with keen monitoring and maintenance of intraoperative hemodynamics. When subtle reductions in urine output or a rising creatinine are observed postoperatively, timely clinical investigation is warranted to maximize renal recovery.

Acute kidney injury in peripheral arterial surgery patients: a cohort study

PURPOSE

The aim of the study was to evaluate the prevalence of acute kidney injury (AKI) in a cohort of surgically treated patients with peripheral artery disease (PAD) and its association with the short-term and long-term outcome.

MATERIALS AND METHODS

We conducted a retrospective cohort study on all the consecutive PAD inpatients in 2008. Data on the patients' demographic characteristics, medical history, treatment, outcome and laboratory tests measurements were retrieved from the medical records.

RESULTS

We analyzed 166 patients (71.6% males, mean age 63.2 years ± SD 10.7 years) and found an AKI prevalence of 12.7%. The AKI patients' group had more chronic kidney disease (CKD) (23.8% vs. 6.2%, p = 0.005), diabetes mellitus (DM) (61.9% vs. 33.1%, p = 0.011) and a higher length of hospital stay (19.48 vs. 15.42 days, p = 0.047). At one year, the mortality was 33.3% in the AKI group compared to 1.3% in non-AKI group, with a strong association between AKI and death (OR = 35.7; 95%CI = 6.7 to 189) and AKI and major cardiovascular events (OR = 29.1; 95% CI = 6.8 to 123.4). There was no significant difference in terms of age, cardiovascular disease and medication between the two groups.

CONCLUSIONS

AKI was associated with a poorer one-year outcome after the surgery of PAD patients. In our study, the presence of previous chronic kidney disease and type 2 diabetes increased the incidence of acute kidney injury after surgery.

Endothelium injury and inflammatory state during abdominal aortic aneurysm surgery: scrutinizing the very early and minute injurious effects using endothelial markers - a pilot study

INTRODUCTION

One of the most severe complications of repair surgery for abdominal aortic aneurysms (AAA) is acute kidney injury (AKI). Acute kidney injury is an inflammatory process whose pathogenesis involves endothelial cells (EC). The aim of this study was to assess the dynamics of endothelium injury markers measured during elective AAA surgery which might confirm the inflammatory character of AKI.

MATERIAL AND METHODS

The study group consisted of 14 patients with AAA. We measured plasma soluble forms of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin, P-selectin as well as the levels of von Willebrand factor (vWF) before, during (including intra-abdominal vein levels before and after aortic clamp removal) and within 2 days after surgery.

RESULTS

We have found a biphasic response of ICAM-1, VCAM-1 and P-selectin with an initial fall and subsequent rise. However, only VCAM-1 changes were significant compared to its baseline value. The maximum decrease of VCAM-1 was observed in the renal vein 5 min after aortic clamp removal (335.42 ±129.63 ng/ml vs. 488.90 ±169.80 ng/ml baseline value, p < 0.05), and the highest rise 48 h after aortic clamp removal (721.46 ±333.99 vs. baseline, p < 0.05).

CONCLUSIONS

Vascular cell adhesion molecule-1 turned out to be the most sensitive indicator of EC injury and inflammatory status after AAA surgery. During AAA surgery, soluble forms of P-selectin, ICAM-1 and VCAM-1 demonstrate a biphasic response with an initial fall and subsequent rise. These soluble forms could have a modulatory effect on the development of inflammation.

Effect of diuretic use on 30-day postdialysis mortality in critically ill patients receiving acute dialysis

BACKGROUND

The impact of diuretic usage and dosage on the mortality of critically ill patients with acute kidney injury is still unclear.

METHODS AND RESULTS

In this prospective, multicenter, observational study, 572 patients with postsurgical acute kidney injury receiving hemodialysis were recruited and followed daily. Thirty-day postdialysis mortality was analyzed using Cox's proportional hazards model with time-dependent covariates. The mean age of the 572 patients was 60.8±16.6 years. Patients with lower serum creatinine (p = 0.031) and blood lactate (p = 0.033) at ICU admission, lower predialysis urine output (p = 0.001) and PaO(2)/FiO(2) (p = 0.039), as well as diabetes (p = 0.037) and heart failure (p = 0.049) were more likely to receive diuretics. A total of 280 (49.0%) patients died within 30 days after acute dialysis initiation. The analysis of 30-day postdialysis mortality by fitting propensity score-adjusted Cox's proportional hazards models with time-dependent covariates showed that higher 3-day accumulated diuretic doses after dialysis initiation (HR = 1.449, p = 0.021) could increase the hazard rate of death. Moreover, higher time-varying 3-day accumulative diuretic doses were associated with hypotension (p<0.001) and less intense hemodialysis (p<0.001) during the acute dialysis period.

BACKGROUND AND SIGNIFICANCE

Higher time-varying 3-day accumulative diuretic dose predicts mortality in postsurgical critically ill patients requiring acute dialysis. Higher diuretic doses are associated with hypotension and a lower intensity of dialysis. Caution should be employed before loop diuretics are administered to postsurgical patients during the acute dialysis period.

[Risk factors for postoperative acute kidney injury in a cohort of 2378 patients from 59 hospitals]

OBJECTIVES

To assess risk factors for postoperative acute kidney injury (AKI) in adults with normal renal function hospitalized for major surgery. To analyze mortality and length of hospital stay in patients who develop postoperative AKI.

PATIENTS AND METHODS

Data for analysis were drawn from the 2006 ARISCAT study. The dependent variable was postoperative AKI defined as a decline in renal function demonstrated by a rise in plasma creatinine level to twice the baseline measurement or a 50% reduction in the glomerular filtration rate. Bivariate and multivariate analyses were used to identify preoperative and intraoperative risk factors.

RESULTS

We analyzed 2378 of the ARISCAT cases, which had been enrolled from 59 participating hospitals; 25 patients (1.1%) developed AKI. Analysis identified 5 risk factors: age, peripheral arterial disease, type of surgical incision, blood loss, and infusion of colloids. The area under the receiver operating characteristic curve was 0.88% (95% confidence interval, 0.79%-0.69%). Duration of hospital stay was longer for patients with postoperative AKI (21.8 days, vs 5.5 days for other patients; P=.007). Mortality was higher in patients with AKI at 30 days (36% vs 0.9%) and at 3 months (48% vs 1.7%).

CONCLUSIONS

The incidence of postoperative AKI was slightly over 1%. Knowledge of postoperative AKI risk factors can facilitate the planning of surgical interventions and anesthesia to reduce subsequent morbidity and mortality and length of hospital stay.

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.

Who is at increased risk for acute kidney injury following noncardiac surgery?

Abelha and colleagues evaluated the incidence and determinants of postoperative acute kidney injury (AKI) after major noncardiac surgery in patients with previously normal renal function. In this retrospective study of 1,166 patients with no previous renal insufficiency, who were admitted to a postsurgical intensive care unit (ICU) over a 2-year period, the incidence of AKI was 7.5%. Multivariate analysis identified American Society of Anesthesiologists physical status, Revised Cardiac Risk Index, high-risk surgery and congestive heart disease as preoperative AKI risk factors. AKI was an independent risk factor for hospital mortality (odds ratio = 3.12, 95% confidence interval = 1.41 to 6.93; P = 0.005), and was associated with higher severity of illness scores (Simplified Acute Physiology Score II and Acute Physiology and Chronic Health Evaluation II), longer ICU length of stay, higher ICU mortality, increased hospital mortality and higher mortality at 6-month follow up. Although the study design excluded 121 patients with significant preoperative renal insufficiency by design, the relatively crude serum creatinine cut-offs used certainly permitted inclusion of numerous patients with preoperative renal impairment. Accordingly, the study design failed to quantify the impact of preoperative renal impairment on risk and outcomes of perioperative AKI in noncardiac surgery, and this should be a goal of such studies in the future. Nonetheless, the study is an important addition to the literature in an under-studied population of patients at high risk for AKI.

Does perioperative hemodynamic optimization protect renal function in surgical patients? A meta-analytic study

OBJECTIVE

Postoperative acute deterioration in renal function, producing oliguria and/or increase in serum creatinine, is one of the most serious complication in surgical patients. Most cases are due to renal hypoperfusion as a consequence of systemic hypotension, hypovolemia, and cardiac dysfunction. Although some evidence suggests that perioperative monitoring and manipulation of oxygen delivery by volume expansion and inotropic drugs may decrease mortality in surgical patients, no study analyzed this approach on postoperative renal dysfunction. The objective of this investigation is to perform a meta-analysis on the effects of perioperative hemodynamic optimization on postoperative renal dysfunction. DATA SOURCES, STUDY SELECTION, DATA EXTRACTION: A systematic literature review, using MEDLINE, EMBASE, and The Cochrane Library databases through January 2008 was conducted and 20 studies met the inclusion criteria (4220 participants). Data synthesis was obtained by using odds ratio (OR) with 95% confidence interval (CI) by random-effects model.

DATA SYNTHESIS

Postoperative acute renal injury was significantly reduced by perioperative hemodynamic optimization when compared with control group (OR 0.64; CI 0.50-0.83; p = 0.0007). Perioperative optimization was effective in reducing renal injury defined consistently with risk, injury, failure, and loss and end-stage kidney disease and Acute Kidney Injury Network classifications, and in studies defining renal dysfunction by serum creatinine and/or need of renal replacement therapy only (OR 0.66; CI 0.50-0.88; p = 0.004). The occurrence of renal dysfunction was reduced when treatment started both preoperatively and intraoperatively or postoperatively, was performed in high-risk patients, and was obtained by fluids and inotropes. Mortality was significantly reduced in treatment group (OR 0.50; CI 0.31-0.80; p = 0.004), but statistical heterogeneity was observed.

CONCLUSIONS

Surgical patients receiving perioperative hemodynamic optimization are at decreased risk of renal impairment. Because of the impact of postoperative renal complications on adverse outcome, efforts should be aimed to identify patients and surgery that would most benefit from perioperative optimization.

Kidney-specific reconstitution of the A1 adenosine receptor in A1 adenosine receptor knockout mice reduces renal ischemia-reperfusion injury

Genetic deletion of the adenosine A1 receptor (A1AR) increased renal injury following ischemia-reperfusion injury suggesting that receptor activation is protective in vivo. Here we tested this hypothesis by expressing the human-A(1)AR in A(1)AR knockout mice. Renal ischemia-reperfusion was induced in knockout mice 2 days after intrarenal injection of saline or a lentivirus encoding enhanced green fluorescent protein (EGFP) or EGFP-human-A(1)AR. We found that the latter procedure induced a robust expression of the reporter protein in the kidneys of knockout mice. Mice with kidney-specific human-A(1)AR reconstitution had significantly lower plasma creatinine, tubular necrosis, apoptosis, and tubular inflammation as evidenced by decreased leukocyte infiltration, pro-inflammatory cytokine, and intercellular adhesion molecule-1 expression in the kidney following injury compared to mice injected with saline or the control lentivirus. Additionally, there were marked disruptions of the proximal tubule epithelial filamentous (F)-actin cytoskeleton in both sets of control mice upon renal injury, whereas the reconstituted mice had better preservation of the renal tubule actin cytoskeleton, which co-localized with the human-A(1)ARs. Consistent with reduced renal injury, there was a significant increase in heat shock protein-27 expression, also co-localizing with the preserved F-actin cytoskeleton. Our findings suggest that selective expression of cytoprotective A(1)ARs in the kidney can attenuate renal injury.

Mice that overexpress human heat shock protein 27 have increased renal injury following ischemia reperfusion

We previously showed that activation of the A1 adenosine receptor protected the kidney against ischemia-reperfusion injury by induction and phosphorylation of heat shock protein 27 (HSP27). Here, we used mice that overexpress human HSP27 (huHSP27) to determine if kidneys from these mice were protected against injury. Proximal tubule cells cultured from the transgenic mice had increased resistance to peroxide-induced necrosis compared to cells from wild-type mice. However, after renal ischemic injury, HSP27 transgenic mice had decreased renal function compared to wild-type mice, along with increased renal expression of mRNAs of pro-inflammatory cytokines (TNF-alpha, ICAM-1, MCP-1) and increased plasma and kidney keratinocyte-derived cytokine. Following ischemic injury, neutrophils infiltrated the kidneys earlier in the transgenic mice. Flow cytometric analysis of lymphocyte subsets showed that those isolated from the kidneys of transgenic mice had increased CD3(+), CD4(+), CD8(+), and NK1.1(+) cells 3 h after injury. When splenocytes or NK1.1(+) cells were isolated from transgenic mice and adoptively transferred into wild-type mice there was increased renal injury. Further, depletion of lymphocytes by splenectomy or neutralization of NK1.1(+) cells resulted in improved renal function in the transgenic mice following reperfusion. Our study shows that induction of HSP27 in renal tubular cells protects against necrosis in vitro, but its systemic increase counteracts this protection by exacerbating renal and systemic inflammation in vivo.

Urinary cystatin C as an early biomarker of acute kidney injury following adult cardiothoracic surgery

There is a need to develop early biomarkers of acute kidney injury following cardiac surgery, where morbidity and mortality are increased by its presence. Plasma cystatin C (CyC) and plasma and urine Neutrophil Gelatinase Associated Lipocalin (NGAL) have been shown to detect kidney injury earlier than changes in plasma creatinine in critically ill patients. In order to determine the utility of urinary CyC levels as a measure of kidney injury, we prospectively collected plasma and urine from 72 adults undergoing elective cardiac surgery for analysis. Acute kidney injury was defined as a 25% or greater increase in plasma creatinine or renal replacement therapy within the first 72 hours following surgery. Plasma CyC and NGAL were not useful predictors of acute kidney injury within the first 6 hours following surgery. In contrast, both urinary CyC and NGAL were elevated in the 34 patients who later developed acute kidney injury, compared to those with no injury. The urinary NGAL at the time of ICU arrival and the urinary CyC level 6 hours after ICU admission were most useful for predicting acute kidney injury. A composite time point consisting of the maximum urinary CyC achieved in the first 6 hours following surgery outperformed all individual time points. Our study suggests that urinary CyC and NGAL are superior to conventional and novel plasma markers in the early diagnosis of acute kidney injury following adult cardiac surgery.

Sevoflurane protects against renal ischemia and reperfusion injury in mice via the transforming growth factor-beta1 pathway

We previously demonstrated that several clinically utilized volatile anesthetics including sevoflurane protected against renal ischemia-reperfusion (IR) injury by reducing necrosis and inflammation in vivo. We also demonstrated that volatile anesthetics produced direct anti-necrotic and anti-inflammatory effects in cultured renal tubules via mechanisms involving the externalization of phosphatidylserine and subsequent release of transforming growth factor (TGF)-beta1. In this study, we tested the hypothesis that volatile anesthetic-mediated renal protection requires TGF-beta1 and SMAD3 signaling in vivo. We subjected TGF-beta1+/+, TGF-beta1+/-, SMAD3+/+, or SMAD3-/- mice to renal IR under anesthesia with pentobarbital sodium or with sevoflurane. Although TGF-beta1+/+ and SMAD3+/+ mice were significantly protected against renal IR injury under sevoflurane anesthesia with reduced necrosis and inflammation, TGF-beta1+/- mice and SMAD3-/- mice were not protected against renal IR with sevoflurane. Furthermore, a neutralizing TGF-beta1 antibody blocked renal protection with sevoflurane in TGF-beta1+/+ mice. Sevoflurane caused nuclear translocation of SMAD3 and reduced the TNF-alpha-induced nuclear translocation of NF-kappaB in primary cultures of proximal tubules from TGF-beta1+/+ but not in TGF-beta1+/- mice. Finally, sevoflurane protected against necrosis induced with hydrogen peroxide in primary cultures of proximal tubules from TGF-beta1+/+ mice or SMAD3+/+ mice but not in proximal tubules from TGF-beta1+/- or SMAD3-/- mice. Therefore, we demonstrate in this study that sevoflurane-mediated renal protection in vivo requires the TGF-beta1-->SMAD3 signaling pathway.

Sevoflurane-mediated TGF-beta1 signaling in renal proximal tubule cells

Several volatile anesthetics, including sevoflurane, protect against renal ischemia-reperfusion injury in vivo by reducing necrosis and inflammation. Furthermore, in cultured renal tubule cells, sevoflurane directly induced the phosphorylation of the cytoprotective kinases (ERK and Akt), upregulated 70-kDa heat shock protein (HSP70), and attenuated nuclear translocation of the proinflammatory transcription factor NF-kappaB. It has been shown that sevoflurane increases the release of transforming growth factor-beta1 (TGF-beta1) in human proximal tubule (HK-2) cells via externalization of plasma membrane phosphatidylserine (PS), and this increase in TGF-beta1 protected HK-2 cells against hydrogen peroxide-mediated necrosis. In this study, we aimed to determine whether the sevoflurane-mediated phosphorylation of ERK and Akt, induction of HSP70, and reduction in NF-kappaB activation are due to TGF-beta1 receptor-mediated signaling after PS externalization in HK-2 cells. Exogenous TGF-beta1 and a liposome mixture containing PS mimicked sevoflurane-mediated ERK and Akt phosphorylation and HSP70 induction in HK-2 cells. Sevoflurane and TGF-beta1 caused the nuclear translocation of the SMAD3 transcription factor in HK-2 cells. Furthermore, a neutralizing TGF-beta1 antibody or exogenous annexin V to bind PS prevented sevoflurane-induced ERK and Akt phosphorylation and HSP70 induction in HK-2 cells. Finally, a TGF-beta1 antibody and annexin V attenuated the reduction in nuclear translocation of NF-kappaB by sevoflurane. Therefore, we demonstrate in this study that sevoflurane-mediated cytoprotective and anti-inflammatory effects in HK-2 cells are at least partially due to the externalization of PS and activation of TGF-beta1 signaling pathways.

Acute and delayed renal protection against renal ischemia and reperfusion injury with A1adenosine receptors

We showed previously that activation of A1adenosine receptors (AR) protects against renal ischemia-reperfusion (IR) injury in rats and mice. In the heart, transient A1AR activation produces biphasic protective effects: acute protection wanes after several hours but protective effects return 24–72 h later (second window of protection). In this study, we determined whether A1AR activation produces delayed renal protection and elucidated the mechanisms of acute and delayed renal protection. A1AR wild-type mice were subjected to 30-min renal ischemia and 24 h of reperfusion to produce acute renal failure. Pretreatment with a selective A1AR agonist 2-chloro- N6-cyclopentyladenosine (CCPA; 0.1 mg/kg bolus ip) either 15 min or 24 h before renal ischemia protected against renal IR injury and reduced renal corticomedullary necrosis, apoptosis, and inflammation. Transient A1AR activation led to phosphorylation of extracellular signal-regulated protein kinase mitogen-activated protein kinase (ERK MAPK), Akt, and heat shock protein 27 (HSP27). Moreover, induction of HSP27 and Akt occurred with CCPA treatment. Inhibition of PKC with chelerythrine prevented acute but not delayed renal protection with A1AR activation. Moreover, deletion of PI3Kγ or inhibition of Akt, but not inhibition of ERK, prevented delayed and acute renal protection with A1AR activation. Inhibition of Gi/owith pertussis toxin obliterated both acute and delayed A1AR-mediated renal protection. In contrast to renal protection with delayed ischemic preconditioning, nitric oxide synthase activity was not induced with delayed A1AR-mediated renal protection. Therefore, transient activation of renal A1AR led to acute as well as delayed protective effects against renal IR injury via distinct signaling pathways.

Acute Renal Injury and Dysfunction Following Elective Abdominal Aortic Surgery

OBJECTIVES

To evaluate the incidence of kidney injury and acute renal dysfunction (ARD) and associated risk factors in open abdominal aortic surgery.

MATERIALS AND METHODS

69 patients undergoing elective infrarenal aortic repair were included in a prospective study. Anaesthesia and haemodynamic management were standardised targeting a mean arterial pressure (MAP) of 70-90 mmHg, pulmonary artery occlusion pressure of 12-14 mmHg and cardiac index >or=2.4 l/min/m(2). Urinary albumin-creatinine and N-acetyl-B-D-glucosaminidase-creatinine ratios were measured as indicators of kidney injury. The definition of ARD was based on the RIFLE criteria.

RESULTS

Kidney injury was found in most patients. ARD developed in 22% of the patients, and acute renal failure in 4%. The patients with ARD were older, and had lower plasma creatinine and estimated GFR before surgery. ARD was associated with intraoperative hypotension (MAP <60 mmHg >15 min), low cardiac index (<2.4 l/min/m(2)), rhabdomyolysis, and early reoperation. Intraoperative hypotension and postoperative low cardiac output were independent risk factors for ARD in multivariate analysis.

CONCLUSIONS

Kidney injury occurs in most patients undergoing infrarenal aortic surgery, but only 22% develop acute renal dysfunction. Hypotension and low cardiac output are risk factors that could be avoided by optimizing perioperative management.

Renal arterial resistive index response to intraabdominal hypertension in a porcine model

OBJECTIVE

The abdominal compartment syndrome is a potentially life-threatening condition with frequent renal involvement. There are few if any means of inferring subclinical effects before organ dysfunction. Because intrarenal pressure correlates with renal sonographic indices in other renal diseases, the purpose of this study was to determine the relationship between increasing intraabdominal hypertension and renal vascular flow velocities in a porcine model using renal Doppler ultrasound.

DESIGN

Animal study.

SETTING

University research laboratory.

SUBJECTS

Eight anesthetized, mechanically ventilated, well-hydrated, 30-kg female Yorkshire pigs.

INTERVENTIONS

Intraabdominal hypertension was induced by instillation of warmed intraperitoneal saline through a midline laparoscopic port. Intraabdominal pressure (IAP) was continuously monitored directly from the peritoneum and indirectly from the bladder. IAP was varied from 0 to 50 mm Hg in increments of 5 mm Hg. At each IAP level, gray-scale, color, and spectral Doppler renal arcuate artery ultrasound was obtained and resistive index (RI) and peak airway pressure calculated.

MEASUREMENTS AND MAIN RESULTS

Excellent agreement between direct and indirect IAP was found (bias, 0.032 mm Hg; 95% limits, -5.5 to 5.6 mm Hg). A linear relationship between RI and indirect IAP was observed and was defined by the regression equation: RI = 0.553 + 0.0104 x bladder pressure. There was a trend toward different RIs between left and right kidneys (p = .052) at the same IAP. RI varied in a linear fashion at low peak airway pressure and demonstrated an inflection point with steeper subsequent slope after peak airway pressure of 30 cm H2O. RI values rapidly returned to near baseline after abdominal decompression.

CONCLUSIONS

In this model, the renal artery RI correlated strongly and linearly with the severity of intraabdominal hypertension, making renal Doppler ultrasound a potential noninvasive screening tool for the renal effects of intraabdominal hypertension. Further studies are warranted.

Defining Acute Renal Failure: RIFLE and Beyond: Table 1

The introduction of the RIFLE classification has increased the conceptual understanding of the acute kidney injury (AKI) syndrome, and this classification has been successfully tested in a number of clinical studies. This review discusses the strengths and weaknesses of the RIFLE classification and suggests additional parameters to broaden future definitions of AKI. These definitions should not only focus on kidney function alone, but also include parameters describing the origin of the patient, the most important causal factors responsible for AKI and information on the pre-existing kidney function. This more complete definition should lead to a decrease in the variability of the results of epidemiological studies and of future clinical trials in AKI populations.

Incidence, risk factors and prognosis of changes in serum creatinine early after aortic abdominal surgery

OBJECTIVE

To determine the incidence, risk factors, and prognostic implications of serum creatinine changes following major vascular surgery.

DESIGN

Observational study.

SETTINGS

University hospital.

PATIENTS

Cohort of 599 consecutive patients undergoing elective abdominal aortic surgery.

INTERVENTIONS

Review of prospectively collected data from 1993 to 2004.

MEASUREMENTS AND RESULTS

The receiver-operator characteristic (ROC) curve analysis was used to detect the best threshold for postoperative elevation in serum creatinine (Delta Creat) in relation to major complications. A cut-off value of +0.5 mg/dl was selected to define renal dysfunction (RD(0.5) group, n=91; no RD(0.5), n=508) that was associated with higher mortality (7.7% in RD(0.5) group vs 1.4% in no RD(0.5) group, P<0.05), rate of admission to the ICU (34% vs 13%, P<0.05), and incidence of cardiovascular (9% vs 4%, P<0.05), respiratory (21% vs 7%, P<0.05), surgical (24% vs 10%, P<0.05), and septic complications (9% vs 3%, P<0.05). After multivariate analysis with logistic regression, renal dysfunction was independently related to low preoperative creatinine clearance [<40 ml/min; odds ratio (OR) 1.5, 95% confidence interval (CI) 1.1-3.9], prolonged renal ischemic time (>40 min; OR, 3.8, 95% CI, 1.9-7.2), blood transfusion (>5 units; OR, 1.9, 95% CI 1.2-6.1), and rhabdomyolysis (OR, 3.6, 95% CI 1.7-7.9).

CONCLUSIONS

Postoperative RD(0.5) (Delta Creat >0.5 mg/dl) occurs in 15% of vascular patients and carries a bad prognosis. Preoperative renal insufficiency and factors related to the complexity of surgery are the main predictors of renal dysfunction.

N-Acetylcysteine for the Prevention of Kidney Injury in Abdominal Aortic Surgery: A Randomized, Double-Blind, Placebo-Controlled Trial

In this prospective, randomized, placebo-controlled, double-blind trial we studied the effects of IV N-acetylcysteine for prevention of renal injury in patients undergoing abdominal aortic surgery. Seventy patients without previously documented renal dysfunction were randomly allocated to receive either N-acetylcysteine (150 mg/kg mixed in 250 mL of 5% dextrose infused in 20 min, followed by an infusion of 150 mg/kg in 250 mL of 5% dextrose over 24 h) or placebo. The infusion was started after the induction of anesthesia. The primary outcome measure was renal injury as measured by the increases in urinary N-acetyl-beta-d-glucosaminidase (NAG)/creatinine ratio (indicator of renal tubular injury) and urinary albumin/creatinine ratio (indicator of glomerular injury). Renal function was assessed by measuring plasma creatinine and serum cystatin C concentrations. The urinary NAG/creatinine ratio increased significantly from baseline to before crossclamp and remained increased on day 5 in both groups. The urinary albumin/creatinine ratio increased significantly from baseline to 6 h after declamping in the N-acetylcysteine group. However, the changes in the NAG/creatinine ratio and the albumin/creatinine ratio were not significantly different between the two groups. Plasma creatinine and serum cystatin C values remained unchanged during the study period in both groups. In conclusion, N-acetylcysteine did not offer any significant protection from renal injury during elective aortic operation in patients with normal preoperative renal function, and some degree of tubular injury seems to occur before aortic crossclamp.

Renal allograft compartment syndrome: an underappreciated postoperative complication

PURPOSE

Renal allograft compartment syndrome (RACS) is early graft dysfunction secondary to retroperitoneal hypertension and resultant ischemia. Our purpose was to identify the incidence, therapies and outcomes of patients with RACS.

METHODS

All patients who underwent a renal transplant between 2000 and 2005 were reviewed. Patients with signs of acute allograft dysfunction were identified. RACS was diagnosed via visual allograft hypoperfusion and/or with preoperative Doppler ultrasound.

RESULTS

Among 458 patients, 11 (2%) were diagnosed with RACS. Characteristics between patient groups were similar. Five (45%) patients displayed adequate initial allograft function after transplantation. Doppler ultrasound was diagnostic. Six (55%) patients displayed poor initial allograft function and were classified as early presenters of RACS. Allograft function improved dramatically upon decompression.

CONCLUSIONS

Clinicians must remain aware of RACS as a potential diagnosis when patients display rapid deterioration in kidney performance after good initial allograft function. Doppler ultrasound is useful in diagnosing late presenters.

A comparison between fenoldopam and low-dose dopamine in early renal dysfunction of critically ill patients*

OBJECTIVE

Fenoldopam mesylate is a selective dopamine-1 agonist, with no effect on dopamine-2 and alpha1 receptors, producing a selective renal vasodilation. This may favor the kidney oxygen supply/demand ratio and prevent acute renal failure. The aim of the study was to investigate if fenoldopam can provide greater benefit than low-dose dopamine in early renal dysfunction of critically ill patients.

DESIGN

Prospective, multiple-center, randomized, controlled trial.

SETTING

University and city hospital intensive care units.

PATIENTS

One hundred adult critically ill patients with early renal dysfunction (intensive care unit stay<1 wk, hemodynamic stability, and urine output<or=0.5 mL/kg over a 6-hr period and/or serum creatinine concentration>or=1.5 mg/dL and<or= 3.5 mg/dL).

INTERVENTIONS

Patients were randomized to receive 2 microg/kg/min dopamine (group D) or 0.1 microg/kg/min fenoldopam mesylate (group F). Drugs were administered as continuous infusion over a 4-day period.

MEASUREMENTS AND MAIN RESULTS

Systemic hemodynamic and renal function variables were recorded daily. The two groups were well matched at enrollment for illness severity and hemodynamic and renal dysfunction. No differences in heart rate or systolic, diastolic, or mean arterial pressure were observed between groups. Fenoldopam produced a more significant reduction in creatinine values compared with dopamine after 2, 3, and 4 days of infusion (change from baseline at time 2, -0.32 vs. -0.03 mg/dL, p=.047; at time 3, -0.45 vs. -0.09 mg/dL, p=.047; and at time 4, -.041 vs. -0.09 mg/dL, p=.02, in groups F and D, respectively). The maximum decrease in creatinine compared with baseline was significantly greater in group F than group D (-0.53+/-0.47 vs. -0.34+/-0.38 mg/dL, p=.027). Moreover, 66% of patients in group F had a creatinine decrease>10% of the baseline value at the end of infusion, compared with only 46% in dopamine group (chi-square=4.06, p=.04). Total urinary output during drug infusion was not significantly different between groups. After 1 day, urinary output was lower in group F compared with group D (p<.05).

CONCLUSIONS

In critically ill patients, a continuous infusion of fenoldopam at 0.1 microg/kg/min does not cause any clinically significant hemodynamic impairment and improves renal function compared with renal dose dopamine. In the setting of acute early renal dysfunction, before severe renal failure has occurred, the attempt to reverse renal hypoperfusion with fenoldopam is more effective than with low-dose dopamine.

Contrast nephropathy may be partly mediated by autonomic dysfunction: renal failure considered as a modern maladaptation of the prehistoric trauma response

The mechanism behind iodinated radiocontrast nephropathy remains elusive. Direct oxidative damage is the prevailing hypothesis, but the apparent protective effect of iodine against oxidation contradicts this view. We propose that autonomic dysfunction participates in the pathogenesis of radiocontrast nephropathy and may account for other contrast-associated reactions previously attributed to allergy. Iodine, through its effects on thyroid function and chemoreceptor response to metabolic acidosis, may induce hyperadrenergia and consequently diminish renovascular flow and urine output. The renal response to adrenergia likely served an adaptive function during prehistoric evolution when trauma was a dominant source of hypovolemia and adrenergia, but the response may behave maladaptively today as evolutionarily nai ve triggers for adrenergia have emerged. Autonomic dysfunction can further impair renal function by deranging renovascular autoregulation and inducing oxidative reperfusion injury as a secondary phenomenon. Many other causes of acute renal failure such as drug toxicity, surgery, hospitalization, and diabetes may operate through hyperadrenergia, impaired renovascular autoregulation, and oxidative reperfusion injury. Dialysis, a volume reduction therapy for renal failure, can counterintuitively worsen renal dysfunction by exacerbating adrenergia, which may explain its association with accelerated atherosclerosis, inflammation, and cancer. Other examples of vicious cycles that perpetuate renal dysfunction may include renal artery stenosis, carotid stenosis, and atherosclerosis as well as the cardio-renal, hepato-renal, and pulmonary-renal syndromes. The benefits of hydration and bicarbonate in protecting renal function may operate in part through baroreceptor- and chemoreceptor-mediated reduction of sympathovagal ratio, respectively. New treatment paradigms for renal failure including pharmacologic and electro-mechanical therapies are envisioned based on autonomic remodeling, reduced sympathovagal ratio, and neuromodulation of pathways typically associated with trauma such as renin, angiotensin, vasopressin, and aldosterone.