Intraoperative oliguria predicts acute kidney injury after major abdominal surgery.

Background: The threshold of intraoperative urine output below which the risk of acute kidney injury (AKI) increases is unclear. The aim of this retrospective cohort study was to investigate the relationship between intraoperative urine output during major abdominal surgery and the development of postoperative AKI and to identify an optimal threshold for predicting the differential risk of AKI. Methods: Perioperative data were collected retrospectively on 3560 patients undergoing major abdominal surgery (liver, colorectal, gastric, pancreatic, or oesophageal resection) at Kyoto University Hospital. We evaluated the relationship between intraoperative urine output and the development of postoperative AKI as defined by recent guidelines. Logistic regression analysis was performed to adjust for patient and operative variables, and the minimum P -value approach was used to determine the threshold of intraoperative urine output that independently altered the risk of AKI. Results: The overall incidence of AKI in the study population was 6.3%. Using the minimum P -value approach, a threshold of 0.3 ml kg -1 h -1 was identified, below which there was an increased risk of AKI (adjusted odds ratio, 2.65; 95% confidence interval, 1.77-3.97; P <0.001). The addition of oliguria <0.3 ml kg -1 h -1 to a model with conventional risk factors significantly improved risk stratification for AKI (net reclassification improvement, 0.159; 95% confidence interval, 0.049-0.270; P =0.005). Conclusions: Among patients undergoing major abdominal surgery, intraoperative oliguria <0.3 ml kg -1 h -1 was significantly associated with increased risk of postoperative AKI.

Renal tubular injury during cardiopulmonary bypass as assessed by urinary release of N-acetyl-ß-D-glucosaminidase.

BACKGROUND: Acute kidney injury (AKI) is a common complication with a major impact on morbidity and mortality after cardiac surgery with cardiopulmonary bypass (CPB). The aim of the present study was to perform a detailed analysis on the release of the tubular injury biomarker N-acetyl-b-D-glucosaminidase (NAG) during and early after CPB and to describe independent predictors of maximal tubular injury. We hypothesized that renal tubular injury occurs early after the onset of CPB. METHODS: In this prospective observational study, we included 61 patients undergoing open cardiac surgery with an expected CPB duration exceeding 60 min. The urinary NAG levels were measured at 30 min intervals during CPB, as well as early (30 min) after CPB and post-operatively. Independent predictors of tubular injury were identified using an Interquantile multivariate regression model. RESULTS: Already 30 min after the onset of CPB, NAG excretion was significantly increased (P < 0.001), followed by a sixfold peak increase after discontinuation of CPB (P < 0.001). In the multivariable regression model, CPB duration (P < 0.05) and the degree of rewarming during CPB (P < 0.05), were independent predictors of peak NAG excretion. CONCLUSION: In cardiac surgery, a renal tubular cell injury is seen early after onset of CPB with a peak biomarker increase early after end of CPB. The magnitude of this tubular injury is independently related to CPB duration and the degree of rewarming. Efforts made to decrease the CPB duration and to avoid hypothermia and the need for rewarming may decrease the risk for tubular injury.

Urine and serum microRNA-1 as novel biomarkers for myocardial injury in open-heart surgeries with cardiopulmonary bypass.

MicroRNA-1 (miR-1) is a cardio-specific/enriched microRNA. Our recent studies have revealed that serum and urine miR-1 could be a novel sensitive biomarker for acute myocardial infarction. Open-heart surgeries with cardiopulmonary bypass (CPB) are often accompanied with surgery injury and CPB-associated injury on the hearts. However, the association of miR-1 and these intra-operative and post-operative cardiac injures is unknown. The objective of this study was to test the hypothesis that urine and serum miR-1 might be a novel biomarker for myocardial injuries in open-heart surgeries with CPB. Serum and urine miR-1 levels in 20 patients with elective mitral valve surgery were measured at pre-surgery, pre-CPB, 60 min post-CBP, and 24h post-CBP. Serum cardiac troponin-I (cTnI) was used as a positive control biomarker for cardiac injury. Compared with these in pre-operative and pre-CPB groups, the levels of miR-1 in serum and urine from patients after open-heart surgeries and CPB were significant increased at all observed time points. A similar pattern of serum cTnI levels and their strong positive correlation with miR-1 levels were identified in these patients. The results suggest that serum and urine miR-1 may be a novel sensitive biomarker for myocardial injury in open-heart surgeries with CPB.

Does N-acetylcysteine prevent contrast-induced nephropathy during endovascular AAA repair? A randomized controlled pilot study.

PURPOSE: To examine if N-acetylcysteine (NAC) reduces the incidence of contrast nephropathy during endovascular abdominal aortic aneurysm repair (EVAR) as evidenced by changes in markers of renal function. METHODS: Twenty consecutive men (mean age 72 years, range 65-79) undergoing EVAR were randomized to receive standard intravenous fluid hydration or standard fluid hydration and NAC (600 mg BID orally, 4 doses). Venous blood and urine were collected prior to the procedure and for 5 postoperative days and analyzed blindly for serum creatinine, urinary retinol-binding protein (RBP), and albumin/creatinine ratio (ACR). RESULTS: There were no significant differences in baseline demographics between the groups. No patient developed acute renal failure. In both groups, urinary RBP rose significantly from baseline (median 15 microg/mmol to peak 699 microg/mmol in controls versus 17 to 648 microg/mmol in the treatment group, p<0.003). There were similar significant rises in ACR (p<0.02). There was, however, no significant difference in the postoperative RBP or ACR between the groups at any time point. CONCLUSION: EVAR causes significant acute renal injury in most patients. This was not attenuated by N-acetylcysteine. The causes of renal injury are probably multifactorial, the long-term clinical significance of which is unclear.

Propylene glycol toxicity caused by prolonged infusion of etomidate.

We describe a case of propylene glycol toxicity due to intravenous administration of etomidate for cerebral protection. A continuous etomidate infusion was titrated to burst suppression of the electroencephalogram during surgical resection of a large intracranial arteriovenous malformation. The etomidate formulation used (Amidate, Abbot) contains etomidate 2 mg/ml in a 35% propylene glycol vehicle. A total of 5 g/kg of the solvent was given during 12 h. Adverse effects of propylene glycol were observed including hyperosmolality with an increased osmolal gap, hemolysis, hemoglobinuria, and metabolic acidosis. Normalization of these metabolic and ionic alterations occurred after 12 h of discontinuation of the infusion. The potential toxicity of the solvent should be considered during long-term administration of etomidate.

[Impairment of diuresis in surgical intervention. Role of urinary prostaglandins]. / Contrazione della diuresi in corso di intervento chirurgico. Ruolo delle prostaglandine urinarie.

In 8 patients who underwent abdominal surgery for non-neoplastic reasons, we have evaluated some parameters of renal function (PRP, NaU, GFR and diuresis) plasma levels of PRA and ADH and urinary prostaglandins PGE2 and 6-keto-PGF1 alpha. In 4 patients we found that surgery per se was associated with enhancements of PRA, ADH and 6-keto-PGF1 alpha. In other 4 patients, Indomethacin, a specific inhibitor of prostaglandin synthesis was given and this was followed by impairment of natriuresis and RPF. These data confirm the central role of prostaglandins in the control of diuresis and natriuresis and suggest that use of drugs affecting prostaglandin synthesis should be avoided in patients who are undergoing surgery.

[Clinical significance of urinary N-acetyl-beta-D-glucosaminidase activities in surgery].

Urinary N-acetyl-beta-D-glucosaminidase (U-NAG) activities were measured in 62 patients surgically treated in our clinic. The results obtained were as follows: The preoperative U-NAG activities were 9.53 +/- 8.63 IU/day in patients in elective operations, and 31.39 +/- 23.47 IU/day in cases in emergency surgery or exploratory laparotomies. The U-NAG activities were elevated slightly even in patients with no postoperative complications, suggesting there was significant damage to the renal tubular epithelium. In the patients with postoperative complications, the U-NAG activities were elevated markedly, especially in those with circulatory shock, suggesting severe damage to the renal tubular epithelium. Though the U-NAG showed abnormally high activities, the values of BUN, S-Cr, U-protein, UUN/BUN, FENa, Ccr, CH2O remained within the normal range. On the contrary, when they were abnormal, the U-NAG activities were not elevated. All patients, who showed high U-NAG activities with abnormal values of Ccr and/or CH2O, developed acute renal failure (ARF). In order to detect ARF in an early stage, Ccr and CH2O should be measured when U-NAG activities rose to over 50 IU/day.