Urinary biomarkers and renal near-infrared spectroscopy predict intensive care unit outcomes after cardiac surgery in infants younger than 6 months of age

Acute Kidney Injury in Pediatric Heart Failure

Acute kidney injury (AKI) is very common in pediatric medical and surgical cardiac patients. Not only is it an independent risk factor for increased morbidity and mortality in the short run, but repeated episodes of AKI lead to chronic kidney disease (CKD) especially in the most vulnerable hosts with multiple risk factors, such as heart transplant recipients. The cardiorenal syndrome, a term coined to emphasize the bidirectional nature of simultaneous or sequential cardiac-renal dysfunction both in acute and chronic settings, has been recently described in adults but scarcely reported in children. Despite the common occurrence and clinical and financial impact, AKI in pediatric heart failure outside of cardiac surgery populations remains poorly studied and there are no large-scale pediatric specific preventive or therapeutic studies to date. This article will review pediatric aspects of the cardiorenal syndrome in terms of pathophysiology, clinical impact and treatment options.

Early detection of acute kidney injury after pediatric cardiac surgery

Acute kidney injury (AKI) is increasingly recognized as a common problem in children undergoing cardiac surgery, with well documented increases in morbidity and mortality in both the short and the long term. Traditional approaches to the identification of AKI such as changes in serum creatinine have revealed a large incidence in this population with significant negative impact on clinical outcomes. However, the traditional diagnostic approaches to AKI diagnosis have inherent limitations that may lead to under-diagnosis of this pathologic process. There is a dearth of randomized controlled trials for the prevention and treatment of AKI associated with cardiac surgery, at least in part due to the paucity of early predictive biomarkers. Novel non-invasive biomarkers have ushered in a new era that allows for earlier detection of AKI. With these new diagnostic tools, a more consistent approach can be employed across centers that may facilitate a more accurate representation of the actual prevalence of AKI and more importantly, clinical investigation that may minimize the occurrence of AKI following pediatric cardiac surgery. A thoughtful management approach is necessary to mitigate the effects of AKI after cardiac surgery, which is best accomplished in close collaboration with pediatric nephrologists. Long-term surveillance for improvement in kidney function and potential development of chronic kidney disease should also be a part of the comprehensive management strategy.

Perioperative use of cerebral and renal near-infrared spectroscopy in neonates: a 24-h observational study

BACKGROUND

Neonates undergoing surgery and intensive care still carry a significant morbidity and mortality often related to hypoxic/ischemic events; some of which may go undetected by conventional monitoring. Near-infrared spectroscopy (NIRS) is a noninvasive, continuous method of measuring regional tissue oxygen saturation, and may be used to supplement conventional monitoring to improve neonatal perioperative care. However, high costs and lack of evidence regarding improved outcomes have minimized wider perinatal use of NIRS. The aim of this study was to investigate the applicability of NIRS in neonates and premature infants undergoing noncardiac surgeries.

METHOD

Neonates were monitored with both cerebral and renal NIRS for 24 h after induction of anesthesia and compared with systemic blood pressure (BP), peripheral oxygen saturation (SpO2 ), and heart rate (HR).

RESULTS

A total of 23 368 min of data were collected from 21 neonates. NIRS reported cerebral/renal hypoxia 2.8 (±8.3)%/19.3 (±25.4)% of the time intraoperatively and 9.6 (±17.0)%/9.9 (±18.9)% of the time postoperatively. A moderate positive correlation was found between SpO2 and NIRS (φcerebral = 0.371, φrenal = 0.542). BP showed a weaker positive correlation (φcerebral = 0.231, φrenal = 0.246), and HR no correlation (φcerebral = -0.083, φrenal = -0.029). NIRS reported hypoxia two to three times more frequently than SpO2 , and SpO2 readings were 10-15 s delayed compared to NIRS. Furthermore, NIRS appeared effective at detecting postoperative apnea.

CONCLUSION

Near-infrared spectroscopy is an easily applicable technique that appears effective at detecting hypoxic events and postoperative apneas in neonates. The high incidences of regional hypoxia reported by NIRS in this study imply that there is a need for a more specific regional cerebral and renal monitoring. Despite some practical and economical limitations, NIRS may be considered a useful supplement to perinatal perioperative intensive care.

Kidney Injury Molecule-1 and Cardiovascular Diseases: From Basic Science to Clinical Practice

Despite the recent findings concerning pathogenesis and novel therapeutic strategies, cardiovascular disease (CVD) still stays the leading cause of morbidity and mortality in patients with renal dysfunction, especially acute kidney injury (AKI). Early detection of patients with impaired renal function with cardiovascular risk may help ensure more aggressive treatment and improve clinical outcome. Kidney injury molecule-1 (KIM-1) is a new, promising marker of kidney damage which is currently the focus of countless studies worldwide. Some recent animal and human studies established KIM-1 as an important marker of acute tubular necrosis (ATN) and reliable predictor of development and prognosis of AKI. Food and Drug Administration (FDA) in USA acclaimed KIM-1 as an AKI biomarker for preclinical drug development. Recent data suggest the importance of monitoring of KIM-1 for early diagnosis and clinical course not only in patients with various forms of AKI and other renal diseases but also in patients with cardiorenal syndrome, heart failure, cardiopulmonary bypass, cardiothoracic surgical interventions in the pediatric emergency setting, and so forth. The aim of this review article is to summarize the literature data concerning KIM-1 as a potential novel marker in the early diagnosis and prediction of clinical outcome of certain cardiovascular diseases.

Near-infrared spectroscopy after high-risk congenital heart surgery in the paediatric intensive care unit

OBJECTIVE

To establish whether the use of near-infrared spectroscopy is potentially beneficial in high-risk cardiac infants in United Kingdom paediatric intensive care units.

DESIGN

A prospective observational pilot study.

SETTING

An intensive care unit in North West England.

PATIENTS

A total of 10 infants after congenital heart surgery, five with biventricular repairs and five with single-ventricle physiology undergoing palliation.

INTERVENTIONS

Cerebral and somatic near-infrared spectroscopy monitoring for 24 hours post-operatively in the intensive care unit.

MEASUREMENT AND MAIN RESULTS

Overall, there was no strong correlation between cerebral near-infrared spectroscopy and mixed venous oxygen saturation (r=0.48). At individual time points, the correlation was only strong (r=0.74) 1 hour after admission. The correlation was stronger for the biventricular patients (r=0.68) than single-ventricle infants (r=0.31). A strong inverse correlation was demonstrated between cerebral near-infrared spectroscopy and serum lactate at 3 of the 5 post-operative time points (1, 4, and 12 hours: r=-0.76, -0.72, and -0.69). The correlation was stronger when the cerebral near-infrared spectroscopy was <60%. For cerebral near-infrared spectroscopy <60%, the inverse correlation with lactate was r=-0.82 compared with those cerebral near-infrared spectroscopy >60%, which was r=-0.50. No correlations could be demonstrated between (average) somatic near-infrared spectroscopy and serum lactate (r=-0.13, n=110) or mixed venous oxygen saturation and serum lactate. There was one infant who suffered a cardiopulmonary arrest, and the cerebral near-infrared spectroscopy showed a consistent 43 minute decline before the event.

CONCLUSIONS

We found that cerebral near-infrared spectroscopy is potentially beneficial as a non-invasive, continuously displayed value and is feasible to use on cost-constrained (National Health Service) cardiac intensive care units in children following heart surgery.

Intraoperative renal near-infrared spectroscopy indicates developing acute kidney injury in infants undergoing cardiac surgery with cardiopulmonary bypass: a case-control study

Introduction

Acute kidney injury (AKI) is a frequent complication after cardiac surgery with cardiopulmonary bypass in infants. Renal near-infrared spectroscopy (NIRS) is used to evaluate regional oximetry in a non-invasive continuous real-time fashion, and reflects tissue perfusion. The aim of this study was to evaluate the relationship between renal oximetry and development of AKI in the operative and post-operative setting in infants undergoing cardiopulmonary bypass surgery.

Methods

In this prospective study, we enrolled 59 infants undergoing cardiopulmonary bypass surgery for congenital heart disease for univentricular (n = 26) or biventricular (n = 33) repair. Renal NIRS was continuously measured intraoperatively and for at least 24 hours postoperatively and analysed for the intraoperative and first 12 hours, first 24 hours and first 48 hours postoperatively. The renal oximetry values were correlated with the paediatric risk, injury, failure, loss, end (pRIFLE) classification for AKI, renal biomarkers and the postoperative course.

Results

Twenty-eight (48%) infants developed AKI based on pRIFLE classification. Already during intraoperative renal oximetry and further in the first 12 hours, 24 hours and 48 hours postoperatively, significantly lower renal oximetry values in AKI patients compared with patients with normal renal function were recorded (P < 0.05). Of the 28 patients who developed AKI, 3 (11%) needed renal replacement therapy and 2 (7%) died. In the non-AKI group, no deaths occurred. Infants with decreased renal oximetry values developed significantly higher lactate levels 24 hours after surgery. Cystatin C was a late parameter of AKI, and neutrophil gelatinase-associated lipocalin values were not correlated with AKI occurrence.

Conclusion

Our results suggest that prolonged low renal oximetry values during cardiac surgery correlate with the development of AKI and may be superior to conventional biochemical markers. Renal NIRS might be a promising non-invasive tool of multimodal monitoring of kidney function and developing AKI in infants undergoing cardiac surgery with cardiopulmonary bypass.

Near-infrared spectroscopy: exposing the dark (venous) side of the circulation

The safety of anesthesia has improved greatly in the past three decades. Standard perioperative monitoring, including pulse oximetry, has practically eliminated unrecognized arterial hypoxia as a cause for perioperative injury. However, most anesthesia-related cardiac arrests in children are now cardiovascular in origin, and standard monitoring is unable to detect many circulatory abnormalities. Near-infrared spectroscopy provides noninvasive continuous access to the venous side of regional circulations that can approximate organ-specific and global measures to facilitate the detection of circulatory abnormalities and drive goal-directed interventions to reduce end-organ ischemic injury.

Fluid overload in infants following congenital heart surgery

OBJECTIVE

To describe postoperative fluid overload patterns and correlate degree of fluid overload with intensive care morbidity and mortality in infants undergoing congenital heart surgery.

DESIGN

Prospective, observational study. Fluid overload (%) was calculated by two methods: 1) (Total fluid in - Total fluid out)/(Preoperative weight) × 100; and 2) (Current weight - Preoperative weight)/(Preoperative weight) × 100. Composite poor outcome included: need for renal replacement therapy, upper quartile time to extubation or intensive care length of stay (> 6.5 and 9.9 days, respectively), or death ≤ 30 days after surgery.

SETTING

University hospital pediatric cardiac ICU.

PATIENTS

Forty-nine infants < 6 months of age undergoing congenital heart surgery with cardiopulmonary bypass during the period of July 2009 to July 2010.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients had a median age of 53 days (21 neonates) and mean weight of 4.5 ± 1.3 kg. Forty-two patients (86%) developed acute kidney injury by meeting at least Acute Kidney Injury Network and Kidney Disease Improving Global Outcomes stage 1 criteria (serum creatinine rise of 50% or ≥ 0.3mg/dL). The patients with adverse outcomes (n = 17, 35%) were younger (7 [5 - 10] vs. 98 [33 - 150] days, p = 0.001), had lower preoperative weight (3.7 ± 0.7 vs. 4.9 ± 1.4 kg, p = 0.0002), higher postoperative mean peak serum creatinine (SCr) (0.9 ± 0.3 vs. 0.6 ± 0.3mg/dL, p = 0.005), and higher mean maximum fluid overload by both method 1 (12% ± 10% vs. 6% ± 4%, p = 0.03) and method 2 (24% ± 15% vs. 14% ± 8%, p = 0.02). Predictors of a poor outcome from multivariate analyses were cardiopulmonary bypass time, use of circulatory arrest, and increased vasoactive medication requirements postoperatively.

CONCLUSIONS

Early postoperative fluid overload is associated with suboptimal outcomes in infants following cardiac surgery. Because the majority of patients developed kidney injury without needing renal replacement therapy, fluid overload may be an important risk factor for adverse outcomes with all degrees of acute kidney injury.