Near Infrared Spectroscopy for the Detection of Acute Kidney Injury in Children Following Cardiac Surgery

Study Overview
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Brief Summary
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One in a hundred children is born with a heart defect. Some children require heart surgery within the first few days of life, while others can wait until they are older. A complication of open-heart surgery is low blood flow due to the heart-lung machine that can cause sudden loss of kidney function known as acute kidney injury (AKI). AKI causes complications that can increase hospital length of stay and increase risk of death. Current ways to identify AKI are not able to it until 2 or 3 days after it has occurred. Because of this, there is not a specific treatment for AKI. If the investigators diagnose AKI early, they might be able to treat it and improve outcomes in children. NIRS is a skin monitor that can detect low blood flow to the kidney and might help diagnose AKI when it occurs in the operating room. The use of NIRS to diagnose AKI early is the focus of this study.

Detailed Description
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Near infrared spectroscopy (NIRS) is a noninvasive tool used for continuous monitoring of regional tissue oxyhemoglobin saturation. Sensors are placed on the head and abdomen or flank and use light to measure the percent oxygen levels in tissues. Head NIRS has been correlated with oxygen levels of the blood returning from the brain, and an abrupt decline in post-operative cardiac patients has been shown in retrospective studies to predict an impending event such as cardiac arrest. Animal studies have demonstrated that somatic NIRS monitoring is able to detect flow-induced changes in regional oxygen levels of the kidney and gut directly under the sensor. Unlike cerebral NIRS monitoring, there is no data regarding the clinical utility of NIRS over the abdomen and flank in predicting outcomes. Children are at risk of decreased organ perfusion following cardiac surgery, and is a phenomenon termed low cardiac output syndrome (LCOS). It occurs in approximately 25% of neonates and young children following cardiac surgery. The effects of LCOS on end organ function, specifically the kidney may result in acute kidney injury, thereby increasing morbidity and mortality. The incidence of acute kidney injury (AKI) following cardiac surgery is reported as high as 40%. The use of NIRS in the operating room to detect AKI in pediatric patients undergoing cardiac surgery is the focus of this proposal Specific Aim 1: Determine if a reduction in renal NIRS intra-operatively identifies patients with AKI Hypothesis: Reduced intra-operative renal NIRS will precede the diagnosis of acute kidney injury by an increase in serum creatinine within 1 to 3 days post-cardiopulmonary bypass Specific Aim 2: Determine if a reduction in renal NIRS intra-operatively correlates with increases in emerging biomarkers of AKI. Hypothesis: Reduced intra-operative renal NIRS will precede the development if AKI as detected by neutrophil gelatinase-associated lipocalin, IL-6 and IL-18 by at least 2 hours.

Official Title
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Use of Near Infrared Spectroscopy (NIRS) for the Early Detection of Acute Kidney Injury in Children Post Cardiopulmonary Bypass

Conditions
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Acute Kidney Injury, Heart; Dysfunction Postoperative, Cardiac Surgery, Children

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: All children less than or equal to age 4 undergoing cardiac surgery with the use of cardiopulmonary bypass at Colorado Children's Hospital Exclusion Criteria: Prior enrollment in the study Agre greater than 4 years Use of nephrotoxic drugs within 48 hours of surgery Underlying renal dysfunction (preoperative estimated Schwartz clearance less than 80ml/min/1.73m2) Gestational age less than 34 weeks at the time of surgery Withdrawal of care planned

Ages Eligible for Study
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Minimum Age: 1 Day
Maximum Age: 4 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Acute kidney injury<br>The group of patients who develop acute kidney injury as defined by the pediatric RIFLE criteria. | |
| No acute kidney injury<br>The patients who do not develop acute kidney injury | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Acute kidney injury | A decline in intra-operative renal NIRS to predict AKI as measured by an increase in serum creatinine. Baseline lab testing, including BMP, UA. Renal NIRS sensors will be placed prior surgery. In the OR, continuous real time monitoring of NIRS will occur and continue for 72 hours after cardiopulmonary bypass (CPB). BMP will be performed after surgery and at 24, 48 and 72 hours. Repeat UA will be performed at 24 hours post CPB, and urine electrolytes and urea will be performed at 12, 24, 48 and 72 hours. AKI as defined by the pRIFLE criteria at 48-72 hours post cardiopulmonary bypass. | 48-72 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Acute kidney injury by renal biomarkers | NIRS monitoring as described above. Baseline renal biomarkers (urine: NGAL, IL-18, IL-6, serum: IL-6, IL-8) followed by repeated sampling at 6, 12, 24, 48 and 72 hours post initiation of CPB. Serum sampling will last only occur through 24 hours. | 12 hours | 
| Mechanical ventilation and acute kidney injury | Duration of mechanical ventilation, including any failures of extubation. Will include ventilator parameters (inspired oxygen, peak pressures) | Hospital admission (day 1) | 
| Hospital length of stay and AKI | Evaluate intensive care and hospital length of stay with regards to presence or absence of AKI | An average of 1 week for simple defects and 4 weeks for complex congenital heart defects (Hypoplastic left heart syndrome) | 
| 30-day mortality and AKI | Evaluate the 30-day mortality with regards to presence or absence of AKI | 30 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Near Infrared Spectroscopy (NIRS), Acute kidney injury (AKI)