Renal dysfunction after vascular surgery

Immediate postoperative plasma neutrophil gelatinase-associated lipocalin to predict acute kidney injury after major open abdominal aortic surgery: A prospective observational study

INTRODUCTION

Plasma neutrophil gelatinase-associated lipocalin (pNGAL) has been used as a biomarker in acute kidney injury (AKI). AKI is a common postoperative complication of aortic surgery. We sought to evaluate the performance of the immediately postoperative pNGAL level in comparison with the serum creatinine (SCr) level in predicting AKI and the need for renal replacement therapy (RRT).

PATIENTS AND METHODS

Prospective non-interventional study in a university hospital. Fifty patients undergoing elective or emergent major intra-abdominal aortic surgery were included. Comparisons between groups of patients with or without postoperative AKI, according to KDIGO staging, were made. Performance of NGAL was determined by examining the area under receiver operating characteristic (AUROC) curve.

RESULTS

The incidence of AKI was 36%. At H+2, pNGAL values in AKI and non-AKI patients, respectively, were 221 [133-278] versus 50 [50-90] ng/mL (P<0.0001), and SCr values were 115 [96-178] versus 90 [72-99] μmol/L (P<0.0008). The AUROC of pNGAL for prediction of AKI was 0.90 (95% CI: 0.81-0.98) with an optimal cutoff of 112ng/mL, a sensitivity of 83%, specificity of 84%, and positive and negative predictive values of 75% and 90%, respectively. SCr produced an AUROC curve of 0.79 (0.65-0.92) at a cutoff of 110μmol/L. The diagnostic performance of pNGAL was significantly better than that of SCr (P=0.039). PNGAL at H+2 better predicted the RRT requirement [0.96 (0.90-1.0)] compared to SCr [0.86 (0.73-0.98)], but this difference was not statistically significant.

CONCLUSIONS

A 2-hour postoperative determination of pNGAL outperformed SCr level in predicting postoperative AKI after major aortic surgery.

Prevention of renal ischemia/reperfusion injury in rats using acetylcysteine after anesthesia with isoflurane

PURPOSE: To evaluate the effect of N-acetylcysteine, as a renoprotective agent, when administered early after anesthesia induction, against ischemia/reperfusion injury in rats anesthetized with isoflurane. METHODS: Eighteen male Wistar rats weighing > 300g were anesthetized with isoflurane. The internal jugular vein and the left carotid artery were dissected and cannulated. The animals were randomly divided into GAcetyl, receiving intravenous N-acetylcysteine, 300mg/kg, and GIsot, isotonic saline. After 30 minutes, right nephrectomy was performed and the left renal artery was clamped during 45 minutes. The animals were sacrificed after 48 hours and blood samples were taken after anesthetic induction and upon sacrificing of the animals to evaluate blood creatinine. The kidneys were sent for histological analysis. RESULTS: The variation in serum creatinine was 2.33mg/dL ± 2.21 in GAcetyl and 4.38mg/dL ± 2.13 in GIsot (p=0.074). Two animals presented intense tubular necrosis in GAcetyl, compared to 5 in GIsot. Only GAcetyl presented animals free of tubular necrosis (two) and tubular degeneration (one). CONCLUSION: After renal ischemia/reperfusion, the rats which were given N-acetylcysteine presented less variation in serum creatinine and milder kidney injuries than the control group.

[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.

Renal impairment following total joint arthroplasty: who is at risk?

Postoperative renal impairment is a serious complication of major surgeries that leads to increased morbidity and mortality. The objective of our study was to identify the risk factors for renal impairment following total joint arthroplasty. Among 17 938 total joint arthroplasties performed between 2000 and 2007, patients developing renal complications were identified. For performing univariate and multivariate analyses, patients with renal impairment were matched in a 1:2 ratio with control group who did not develop renal impairment. Ninety-eight (0.55%) patients developed either acute renal failure or acute renal injury. We identified the following as independent risk factors: elevated body mass index; elevated preoperative serum creatinine; and history of chronic obstructive pulmonary disease, liver disease, congestive heart failure, hypertension, and underlying heart disease. Renal impairment was significantly associated with increased duration of hospital stay and with in-hospital and 1-year all-cause mortality. In high-risk patients, preoperative optimization might be considered in an attempt to reduce the incidence of such a complication.

Effect of noble gases on oxygen and glucose deprived injury in human tubular kidney cells

The noble gas xenon has been shown to be protective in preconditioning settings against renal ischemic injury. The aims of this study were to determine the protective effects of the other noble gases, helium, neon, argon, krypton and xenon, on human tubular kidney HK2 cells in vitro. Cultured human renal tubular cells (HK2) were exposed to noble gas preconditioning (75% noble gas; 20% O(2); 5% CO(2)) for three hours or mock preconditioning. Twenty-four hours after gas exposure, cell injury was provoked with oxygen-glucose deprived (OGD) culture medium for three hours. Cell viability was assessed 24 h post-OGD by a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay. Other cohorts of cultured cells were incubated in the absence of OGD in 75% noble gas, 20% O(2) and 5% CO(2) and cellular signals phospho-Akt (p-Akt), hypoxia-inducible factor-1alpha (HIF-1alpha) and Bcl-2 were assessed by Western blotting. OGD caused a reduction in cell viability to 0.382 +/- 0.1 from 1.0 +/- 0.15 at control (P < 0.01). Neon, argon and krypton showed no protection from injury (0.404 +/- 0.03; 0.428 +/- 0.02; 0.452 +/- 0.02; P > 0.05). Helium by comparison significantly enhanced cell injury (0.191 +/- 0.05; P < 0.01). Xenon alone exerted a protective effect (0.678 +/- 0.07; P < 0.001). In the absence of OGD, helium was also detrimental (0.909 +/- 0.07; P < 0.01). Xenon caused an increased expression of p-Akt, HIF-1alpha and Bcl-2, while the other noble gases did not modify protein expression. These results suggest that unlike other noble gases, preconditioning with the anesthetic noble gas xenon may have a role in protection against renal ischemic injury.

Hyperoxia-induced protection against rat's renal ischemic damage: relation to oxygen exposure time

BACKGROUND

Pre-exposure to hyperoxic gas (>or= 95%) has been shown to protect the heart and central nervous system from ischemia-reperfusion injury. In the present study, we investigated whether oxygen pretreatment induces delayed renal protection in rats. The possible role of some renal antioxidant agents was also investigated.

MATERIALS AND METHODS

Adult male Wistar rats were kept in a hyperoxic (HO) (>or= 95% O(2)) environment for 0.5 h, 1 h, 2 h, 3 h, 6 h, and 2 h/day for three consecutive days and 4 h/day for six consecutive days, and control group (IR) animals were kept in the cage with no HO, one day before subjecting their kidney to 40 minutes of ischemia and 24h of reperfusion. Renal function was assessed by comparing plasma creatinine (Cr), blood urea nitrogen (BUN), creatinine clearance (CLCr), and fractional excretion of sodium (FENa%). Histopathological injury score was also determined according to the Jablonski method. To examine the antioxidant system induction by hyperoxia, we measured renal catalase and superoxide dismutase activity, and renal glutathione and malondialdehyde content.

RESULTS

Our data demonstrated that only in 4 h/day HO for six consecutive days, the renal function tests (Cr, CLCr, BUN, and FENa%) and Jablonski histological injury were better than control group (p < 0.05). The beneficial effect of oxygen pretreatment in this group was associated with increased renal catalase activity compared with those obtained from control group (p < 0.05).

CONCLUSION

The present study demonstrates that repeated exposure to hyperoxic (>or= 95% O(2)) environment can reduce subsequent rat's renal ischemia-reperfusion damage. Induction of endogenous antioxidant system may partially explain this beneficial effect of hyperoxic preconditioning.

Isoflurane mediates protection from renal ischemia-reperfusion injury via sphingosine kinase and sphingosine-1-phosphate-dependent pathways

The inhalational anesthetic isoflurane has been shown to protect against renal ischemia-reperfusion (IR) injury. Previous studies demonstrated that isoflurane modulates sphingolipid metabolism in renal proximal tubule cells. We sought to determine whether isoflurane stimulates sphingosine kinase (SK) activity and synthesis of sphingosine-1-phosphate (S1P) in renal proximal tubule cells to mediate renal protection via the S1P signaling pathway. Isoflurane anesthesia reduced the degree of renal failure and necrosis in a murine model of renal IR injury. This protection with isoflurane was reversed by SK inhibitors (DMS and SKI-II) as well as an S1P(1) receptor antagonist (VPC23019). In addition, mice deficient in SK1 enzyme were not protected from IR injury with isoflurane. SK activity as well as SK1 mRNA expression increased in both cultured human proximal tubule cells (HK-2) and mouse kidneys after exposure to isoflurane. Finally, isoflurane increased the generation of S1P in HK-2 cells. Taken together, our findings indicate that isoflurane activates SK in renal tubule cells and initiates S1P-->S1P(1) receptor signaling to mediate the renal protective effects. Our findings may help to unravel the cellular signaling pathways of volatile anesthetic-mediated renal protection and lead to new therapeutic applications of inhalational anesthetics during the perioperative period.

Perioperative acute renal failure

PURPOSE OF REVIEW

Recent biochemical evidence increasingly implicates inflammatory mechanisms as precipitants of acute renal failure. In this review, we detail some of these pathways together with potential new therapeutic targets.

RECENT FINDINGS

Neutrophil gelatinase-associated lipocalin appears to be a sensitive, specific and reliable biomarker of renal injury, which may be predictive of renal outcome in the perioperative setting. For estimation of glomerular filtration rate, cystatin C is superior to creatinine. No drug is definitively effective at preventing postoperative renal failure. Clinical trials of fenoldopam and atrial natriuretic peptide are, at best, equivocal. As with pharmacological preconditioning of the heart, volatile anaesthetic agents appear to offer a protective effect to the subsequently ischaemic kidney.

SUMMARY

Although a greatly improved understanding of the pathophysiology of acute renal failure has offered even more therapeutic targets, the maintenance of intravascular euvolaemia and perfusion pressure is most effective at preventing new postoperative acute renal failure. In the future, strategies targeting renal regeneration after injury will use bone marrow-derived stem cells and growth factors such as insulin-like growth factor-1.

Prevention of perioperative acute renal failure: what works?

Perioperative acute renal failure (ARF) is associated with increased morbidity and mortality. Patients undergoing cardiac, vascular and major abdominal surgery and those with pre-operative renal insufficiency are at increased risk for developing post-operative ARF. The aetiologies of perioperative ARF are multi-factorial. However, pre-renal azotaemia and ischaemic acute tubular necrosis (ATN) are the predominant causes. Preventive strategies involve identifying patients at risk, optimizing intravascular volume as well as renal function with perioperative haemodynamic monitoring, and avoiding nephrotoxins. Various pharmacological agents have been used to optimize renal perfusion and tubular function. Unfortunately, none has been shown to be effective in randomized placebo-controlled trials. In this chapter, we discuss the prophylactic use of fluids, vasoactive drugs, diuretics and other agents, as well as modification of surgical techniques to reduce the incidence of perioperative ARF.