Renal function and cardiopulmonary bypass in pediatric cardiac surgical patients

Kinetics of Renin Concentrations in Infants Undergoing Congenital Cardiac Surgery

BACKGROUND

Elevated renin has been shown to predict poor response to standard vasoactive therapies and is associated with poor outcomes in adults. Similarly, elevated renin was associated with mortality in children with septic shock. Renin concentration profiles after pediatric cardiac surgery are unknown. The purpose of this study was to characterize renin kinetics after pediatric cardiac surgery.

METHODS

Single-center retrospective study of infants who underwent cardiac surgery with cardiopulmonary bypass (CPB) utilizing serum samples obtained in the perioperative period to measure plasma renin concentrations (pg/mL). Time points included pre-bypass and 1, 4, and 24 h after initiation of CPB.

RESULTS

Fifty patients (65% male) with a median age 5 months (interquartile range (IQR) 3.5, 6.5) were included. Renin concentrations peaked 4 h after CPB. There was a significant difference in preoperative and 4 h post-CPB renin concentration (4 h post-CPB vs preoperative: mean difference 100.6, 95% confidence interval (CI) 48.9-152.4, P < .001). Median renin concentration at 24 h after CPB was lower than the preoperative baseline.

CONCLUSIONS

We describe renin kinetics in infants after CPB. Future studies based on these data can now be performed to evaluate the associations of elevated renin concentrations with adverse outcomes.

Biomarkers as predictors of renal damage in neonates undergoing cardiac surgery

BACKGROUND

Acute Kidney Injury is a complication in children with heart disease undergoing cardiac surgery with cardiopulmonary bypass. The aim of this study is to describe the behavior of KIM-1 (Kidney Injury Molecule) and NGAL (Neutrophil Gelatinase Associated Lipocalin) as early predictors of renal damage, comparing them with serum creatinine and creatinine clearance, in neonates undergoing cardiac surgery.

METHODS

Twenty-one (21) neonates, under 4 kg, with complex congenital heart diseases, RACHS-1 > 3, without preoperative renal failure, were studied. Serum creatinine and creatinine clearance were measured preoperatively and at 24, 48, 72, 96 hours postoperatively. Urinary samples of KIM-1(pg/ml) and NGAL (ng/ml) were collected after induction of anesthesia at 24 and 48 hours post-operatively.

RESULTS

nRIFLE criteria were used to divide cohorts in "NO AKI" (12 patients) and "AKI" (nine patients). In the AKI group, serum creatinine increased significantly and creatinine clearance decreased significantly at 24, 48, and 72 hours compared with their respective baseline values. There was no difference in KIM-1 and NGAL values between patients who developed AKI and those who did not at any measured time.

CONCLUSIONS

The deterioration of renal function continues to be one of the most frequent complications in this population. In our study, biomarkers did not show any correlation with the appearance of AKI. It remains to be seen whether this behavior of the biomarkers is linked with the non-consistent release of these types of molecules in immature kidneys. It is likely that a larger panel of biomarkers together with other glomerular filtration rate assessment methods will provide more information about AKI diagnosis.

The effect of intraoperative dexmedetomidine on acute kidney injury after pediatric congenital heart surgery: A prospective randomized trial

BACKGROUND

Dexmedetomidine has been reported to have a renal protective effect after adult open heart surgery. The authors hypothesized that intraoperative infusion of dexmedetomidine would attenuate the decrease in renal function after pediatric open heart surgery.

METHODS

Twenty-nine pediatric patients (1-6 years) scheduled for atrial or ventricular septal defect repair were randomly assigned to receive either continuous infusion of normal saline (control group, n = 14) or dexmedetomidine (a bolus dose of 0.5 μg/kg and then an infusion of 0.5 μg/kg/h) (dexmedetomidine group, n = 15) from anesthesia induction to the end of cardiopulmonary bypass. Serum creatinine (Scr) was measured before surgery (T0), 10 minutes after anesthesia induction (T1), 5 minutes after cardiopulmonary bypass weaning (T2), 2 hours after T2 (T3), and after postoperative day 1 (POD1) and postoperative day 2 (POD2) and estimated glomerular filtration rates (eGFRs) were calculated. Renal biomarkers were measured at T1, T2, and T3. Acute kidney injury (AKI) was defined as an absolute increase in Scr of ≥ 0.3 mg/dL or a percent increase in Scr of ≥50%.

RESULTS

The incidence of AKI during the perioperative period was significantly higher in the control group than in the dexmedetomidine group (64% [9/14] vs 27% [4/15], P = .042). eGFR was significantly lower in the control group than in the dexmedetomidine group at T2 (72.6 ± 15.1 vs 83.9 ± 13.5, P = .044) and T3 (73.4 ± 15.4 vs 86.7 ± 15.9, P = .03).

CONCLUSION

Intraoperative infusion of dexmedetomidine may reduce the incidence of AKI and suppress post-bypass eGFR decline.

Urine Output During Cardiopulmonary Bypass Predicts Acute Kidney Injury After Cardiac Surgery: A Single-Center Retrospective Analysis

Urine output is closely associated with renal function and has been used as a diagnostic criterion for acute kidney injury (AKI). However, urine output during cardiopulmonary bypass (CPB) has never been identified as a predictor of postoperative AKI. Considering altered renal homeostasis during CPB, we made a comprehensible approach to CPB urine output and evaluated its predictability for AKI.Patients undergoing cardiovascular surgery with the use of CPB, between January 2009 and December 2011, were retrospectively reviewed. AKI was defined as an increase in serum creatinine ≥0.3 mg/dL in the first postoperative 48 hours. We extrapolated a possible optimal amount of urine output from the plot of probability of AKI development according to CPB urine output. After separating patients by the predicted optimal value, we performed stepwise logistic regression analyses to find potential predictors of AKI in both subgroups.A total of 696 patients were analyzed. The amount of CPB urine output had a biphasic association with the incidence of AKI using 4 mL/kg/h as a boundary value. In a multivariate logistic regression to find predictors for AKI in entire patients, CPB urine output did not show statistical significance. After separating patients into subgroups with CPB urine output below and over 4 mL/kg/h, it was identified as an independent predictor for AKI with the odds ratio of 0.43 (confidence interval 0.30-0.61) and 1.11 (confidence interval 1.02-1.20), respectively.The amount of urine output during CPB with careful analysis may serve as a simple and feasible method to predict the development of AKI after cardiac surgery at an early time point.

Major cardiac surgery induces an increase in sex steroids in prepubertal children

While the neuroprotective benefits of estrogen and progesterone in critical illness are well established, the data regarding the effects of androgens are conflicting. Surgical repair of congenital heart disease is associated with significant morbidity and mortality, but there are scant data regarding the postoperative metabolism of sex steroids in this setting. The objective of this prospective observational study was to compare the postoperative sex steroid patterns in pediatric patients undergoing major cardiac surgery (MCS) versus those undergoing less intensive non-cardiac surgery. Urinary excretion rates of estrogen, progesterone, and androgen metabolites (μg/mmol creatinine/m(2) body surface area) were determined in 24-h urine samples before and after surgery using gas chromatography-mass spectrometry in 29 children undergoing scheduled MCS and in 17 control children undergoing conventional non-cardiac surgery. Eight of the MCS patients had Down's syndrome. There were no significant differences in age, weight, or sex between the groups. Seven patients from the MCS group showed multi-organ dysfunction after surgery. Before surgery, the median concentrations of 17β-estradiol, pregnanediol, 5α-dihydrotestosterone (DHT), and dehydroepiandrosterone (DHEA) were (control/MCS) 0.1/0.1 (NS), 12.4/11.3 (NS), 4.7/4.4 (NS), and 2.9/1.1 (p=0.02). Postoperatively, the median delta 17β-estradiol, delta pregnanediol, delta DHT, and delta DHEA were (control/MCS) 0.2/6.4 (p=0.0002), -3.2/23.4 (p=0.013), -0.6/3.7 (p=0.0004), and 0.5/4.2 (p=0.004). Postoperative changes did not differ according to sex. We conclude that MCS, but not less intensive non-cardiac surgery, induced a distinct postoperative increase in sex steroid levels. These findings suggest that sex steroids have a role in postoperative metabolism following MCS in prepubertal children.

Urinary glutathione S-transferases in the pathogenesis and diagnostic evaluation of acute kidney injury following cardiac surgery: a critical review

PURPOSE OF REVIEW

A focused review of the nature, source, physiological role and rapidly expanding evidence for glutathione S-transferase (GST) subtypes π and α as biomarkers of acute kidney injury (AKI) in patients undergoing cardiac surgery. Expanded insights into the site-specific expression of the GSTs in defined parts of the nephron during renal damage are presented, with particular emphasis on the pathogenesis of cardiac surgery and cardiopulmonary bypass (CPB)-associated AKI and the role of GSTs in oxygen radical disposal.

RECENT FINDINGS

Recent developments have highlighted a potential role of urinary α-GST and π-GST in the diagnostic evaluation of cardiac surgery-associated AKI. Both urinary α-GST and π-GST are detected in the postoperative period. π-GST performed best at predicting AKI severity at the time of the initial diagnosis of AKI. α-GST was able to predict the future development of both stage 1 and stage 3 AKI.

SUMMARY

The current data from a small number of patients suggest a potential role of urinary GSTs in the clinical diagnostic evaluation of AKI following cardiac surgery. The performance of the GSTs for the early diagnosis of AKI needs to be validated in larger multicentre studies and in other patient populations at increased risk of AKI (e.g. patients with acute transplant rejection, septic patients). Comparison with other emerging AKI biomarkers is required to continue the development of π-GST and α-GST. Finally, additional studies examining the pathophysiological role of the GSTs in minimizing oxygen free radical exposure in the renal tubules during CPB may shed further light into their role as promising biomarkers of cardiac surgery-associated AKI.

Effect of iloprost on renal function in patients undergoing coronary artery bypass grafting: a clinical study

PURPOSE

Renal dysfunction remains a serious complication of coronary artery bypass grafting (CABG) surgery and is associated with increased mortality and morbidity. To date, a number of different strategies, including new pharmacologic agents, off-pump and cardiopulmonary bypass techniques have been used to avoid it, but none of them proves the excellent result.

METHODS

Between April 2009 to September 2011, 185 consecutive patients with multivessel coronary artery disease undergoing elective CABG were included the study. Iloprost was given with the onset of rewarming period at a dose of 1.25-2.5 ng/kg/min and it was ended together with the ending of CPB in 94 patients and remaining were in the control group. Creatinine clearance (CCr) and GFR were measured at the time of hospitalisation and on day first and fifth postoperatively. Serum potassium level was determined every 6 hours, during the first 24 hours postoperatively, and every 12 hours for the next 72 hours, and glomerular filtration rate was estimated.

RESULTS

There was no statistically significant difference in preoperative comorbidity. There were no significant differences in postoperative morbidity or mortality between either of the two groups that completed the study. However, urine output during the operation was significantly higher in the study group. An increase in creatine levels was more common in the control group. Development of a new CCr less than 50 ml/min was also significantly higher in the control group, postoperatively.

CONCLUSION

Our study demonstrates that prophylactic intravenous iloprost administration after initiation of a rewarming period during CPB in patients undergoing CABG surgery is associated with improved renal function, compared with conventional treatment in well-hydrated patients. It also has a good safety profile and is generally well tolerated.

Cardiopulmonary bypass and its direct effects on neonatal piglet kidney morphology

Renal failure after open heart surgery is a serious complication even in the pediatric population. The aim of the present study was to analyze morphological changes after cardiopulmonary bypass (CPB) surgery in a neonatal piglet model. The kidneys of newborn piglets sacrificed 6 h after CPB were examined (CPB; n = 4) regarding tubular dilatation, vacuole formation, leukocytic infiltration, epithelial destruction, and interstitial edema. Thereafter, the findings were compared with the morphology of normal (untreated) neonatal piglet kidneys (control; n = 4). All changes but the interstitial edema were statistically significant if compared with the normal renal tissue: tubular dilatation (CPB vs. control P < 0.05), vacuole formation (CPB vs. control P < .05), leukocytic infiltration (CPB vs. control P < 0.05), and epithelial destruction (CPB vs. control P < 0.001). In conclusion, CPB induces significant changes in the morphology of the neonatal piglet kidneys.

Aprotinin and renal dysfunction after pediatric cardiac surgery

BACKGROUND

Aprotinin is a potent antifibrinolytic drug, which reduces postoperative bleeding and transfusion requirements. Recently, two observational studies reported increased incidence of renal dysfunction after aprotinin use in adults. Therefore, the aim of the study was to investigate the safety of aprotinin use in pediatric cardiac surgery patients.

METHODS

Data were prospectively and consecutively collected from 657 pediatric patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). The database was assessed with regard to a possible relationship between aprotinin administration and dialysis and between aprotinin and postoperative renal dysfunction [defined as 25% decrease in the creatinine clearance (Ccr) compared with the preoperative value] by propensity-score adjustment and multivariable methods.

RESULTS

The incidence of dialysis (9.6% vs 4.1%; P = 0.005) and renal dysfunction (26.3% vs 16.1%; P = 0.019) was higher in patients who received aprotinin; however, propensity adjusted risk ratios were not significant [odds ratio (OR) of dialysis: 1.22; 95% confidence interval (CI) 0.46-3.22; OR of renal dysfunction 1.26; 95% CI: 0.66-1.92]. Aprotinin significantly reduced blood loss in the first postoperative 24 h. The main contributors of renal dysfunction were CPB duration, cumulative inotropic support, age, preoperative Ccr, amount of transfusion and pulmonary hypertension.

CONCLUSIONS

Despite the higher incidences of renal dysfunction and failure in the aprotinin group, an independent role of the drug in the development of renal dysfunction or dialysis could not be demonstrated in pediatric cardiac patients undergoing CPB.