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

Association Between Urinary Biomarkers and CKD in Extremely Low Gestational Age Neonates

RATIONALE & OBJECTIVE

Children born before 28 weeks' gestation are at increased risk of chronic kidney disease (CKD). Urine biomarkers may shed light on mechanistic pathways and improve the ability to forecast CKD. We evaluated whether urinary biomarkers in neonates of low gestational age (GA) are associated with a reduced estimated glomerular filtration rate (eGFR) over time.

STUDY DESIGN

A cohort study of neonates with an exploratory case-control study of a subset of the cohort.

SETTING & PARTICIPANTS

327 neonates born at 24-27 weeks' gestation with 2-year eGFR data from the PENUT (Preterm Erythropoietin Neuroprotection Trial) and the REPaIReD (Recombinant Erythropoietin for Prevention of Infant Renal Disease) study.

EXPOSURES

11 urinary biomarkers measured at 27, 30, and 34 weeks' postmenstrual age for the primary cohort study and 10 additional biomarkers for the exploratory case-control study.

OUTCOMES

eGFR<90mL/min/1.73m2 at 2 years corrected for GA.

ANALYTICAL APPROACH

Linear mixed models to assess differences in biomarker values between neonates in whom CKD did and did not develop, accounting for multiple comparisons using Bonferroni-Holm correction in the cohort study only. Cohort analyses were adjusted for sex, GA, and body mass index. Cases were matched to controls on these variables in the case-control study.

RESULTS

After adjusting for weeks of GA, urinary levels of α-glutathione-S-transferase (log difference, 0.27; 95% CI, 0.12-0.43), albumin (log difference, 0.13; 95% CI, 0.02-0.25), and cystatin C (log difference, 0.19; 95% CI, 0.04-0.34) were higher in those in whom CKD developed than in those in whom it did not. Urinary albumin and cystatin C levels did not remain significantly different after Bonferroni-Holm correction. In the exploratory case-control analysis, there were no differences in any biomarkers between cases and controls.

LIMITATIONS

Early deaths and a high number of subjects without eGFR at 2 years corrected for GA.

CONCLUSIONS

Measurement of urinary biomarkers may assist in monitoring neonates who are at risk for CKD. Additional studies are needed to confirm these findings.

FUNDING

Grants from government (National Institutes of Health).

TRIAL REGISTRATION

Registered at ClinicalTrials.gov with study number NCT01378273.

PLAIN-LANGUAGE SUMMARY

Approximately 15 million neonates worldwide are born prematurely, and 2 million are born before 28 weeks' gestation. Many of these children go on to experience chronic kidney disease. Urine biomarkers may allow for early recognition of those at risk for the development of kidney disease. In this study of more than 300 children born before 28 weeks' gestational age, we found higher mean urinary levels of α-glutathione-S-transferase at 27, 30, and 34 weeks in children whose estimated glomerular filtration rate was<90mL/min/1.73m2 at 2 years compared with children whose estimated glomerular filtration rate was>90mL/min/1.73m2 at 2 years. Measurement of urinary biomarkers may assist in monitoring neonates who are at risk for chronic kidney disease. Additional studies are needed to confirm our findings.

Association of intraoperative cerebral and somatic tissue oxygen saturation with postoperative acute kidney injury in adult patients undergoing multiple valve surgery

BACKGROUND

The association between tissue oxygenation with postoperative acute kidney injury (AKI) in adult patients undergoing multiple valve surgery has not been specifically studied.

METHODS

In this prospective exploratory cohort study, 99 patients were enrolled. The left forehead, the left forearm, the left upper thigh, and the left renal region tissue oxygen saturation using near-infrared spectroscopy were monitored. The association between each threshold and AKI was assessed. The relative and absolute thresholds were < 70%, < 75%, < 80%, < 85%, < 90%, < 95%, and < 100% baseline, and baseline-standard deviation (SD), -1.5 SD, -2 SD, -2.5 SD, and -3 SD. Multivariate logistic regression analysis was adopted to explore the association.

RESULTS

AKI occurred in 53 (54%) patients. The absolute value-based SrrO2 thresholds associated with AKI were baseline-3 SD (odds ratio [OR], 4.629; 95% confidence interval [CI], 1.238-17.314; P = 0.023) and baseline-2.5 SD (OR, 2.842; 95% CI, 1.025-7.881; P = 0.045) after adjusting for the potential confounders, those are renal region tissue oxygen saturation of 55% and 60%, but not statistically significant after correcting for multiple testing (corrected P = 0.114 and 0.179, respectively).

CONCLUSION

The SrrO2 desaturation, defined as < baseline - 2.5 SD or < baseline - 3 SD, may be associated with AKI. The thresholds need to be verified in future large-scale studies.

TRIAL REGISTRATIONS

The study was registered at ClinicalTrials.gov, first trial registration: 26/10/2017, identifier: NCT03323203.

The Potential Use of Near- and Mid-Infrared Spectroscopy in Kidney Diseases

Traditional renal biomarkers such as serum creatinine and albuminuria/proteinuria are rather insensitive since they change later in the course of the disease. In order to determine the extent and type of kidney injury, as well as to administer the proper therapy and enhance patient management, new techniques for the detection of deterioration of the kidney function are urgently needed. Infrared spectroscopy is a label-free and non-destructive technique having the potential to be a vital tool for quick and inexpensive routine clinical diagnosis of kidney disorders. The aim of this review is to provide an overview of near- and mid-infrared spectroscopy applications in patients with acute kidney injury and chronic kidney disease (e.g., diabetic nephropathy and glomerulonephritis).

Intraoperative renal desaturation and postoperative acute kidney injury in older patients undergoing liver resection: A prospective cohort study

STUDY OBJECTIVE

To determine the association between intraoperative renal tissue desaturation as measured using near-infrared spectroscopy and increased likelihood of developing postoperative acute kidney injury (AKI) in older patients undergoing hepatectomy.

DESIGN

A multicenter prospective cohort study.

SETTING

The study was conducted at two tertiary hospitals in China from September 2020 to October 2021.

PATIENTS

157 older patients (≥ 60 years) undergoing open hepatectomy surgery.

INTERVENTIONS AND MEASUREMENTS

Renal tissue oxygen saturation was continuously monitored during operation using near-infrared spectroscopy. The exposure of interest was intraoperative renal desaturation, defined as at least 20% relative decline in renal tissue oxygen saturation from baseline. The primary outcome was postoperative AKI, defined using the Kidney Disease: Improving Global Outcomes criteria according to the serum creatinine criteria.

MAIN RESULTS

Renal desaturation occurred in 70 of 157 patients. Postoperative AKI was observed in 23% (16/70) and 8% (7/87) of patients with versus without renal desaturation. Patients with renal desaturation were at higher risk of AKI than patients without renal desaturation (adjusted odds ratio 3.41, 95% confidence interval: 1.12-10.36, p = 0.031). Predictive performance was 65.2% sensitivity and 33.6% specificity for hypotension alone, 69.6% sensitivity and 59.7% specificity for renal desaturation alone, and 95.7% sensitivity and 26.9% specificity for combined use of hypotension and renal desaturation.

CONCLUSIONS

Intraoperative renal desaturation occurred in >40% in our sample of older patients undergoing liver resection and was associated with increased risk of AKI. Intraoperative near-infrared spectroscopy monitoring enhances the detection of AKI.

Potential of Urine Biomarkers CHI3L1, NGAL, TIMP-2, IGFBP7, and Combinations as Complementary Diagnostic Tools for Acute Kidney Injury after Pediatric Cardiac Surgery: A Prospective Cohort Study

Acute kidney injury (AKI) is common after pediatric cardiac surgery (CS). Several urine biomarkers have been validated to detect AKI earlier. The objective of this study was to evaluate urine CHI3L1, NGAL, TIMP-2, IGFBP7, and NephroCheck® as predictors for AKI ≥ 1 in pediatric CS after 48 h and AKI ≥ 2 after 12 h. Pediatric patients (age < 18 year; body weight ≥ 2 kg) requiring CS were prospectively included. Urine CHI3L1, NGAL, TIMP-2, IGFBP7, and NephroCheck® were measured during surgery and intensive care unit (ICU) stay and corrected for urine dilution. One hundred and one pediatric patients were included. AKI ≥ 1 within 48 h after ICU admission occurred in 62.4% and AKI ≥ 2 within 12 h in 30.7%. All damage biomarkers predicted AKI ≥ 1 within 48 h after ICU admission, when corrected for urine dilution: CHI3L1 (AUC-ROC: 0.642 (95% CI, 0.535–0.741)), NGAL (0.765 (0.664–0.848)), TIMP-2 (0.778 (0.662–0.868)), IGFBP7 (0.796 (0.682–0.883)), NephroCheck® (0.734 (0.614–0.832)). Similarly, AKI ≥ 2 within 12 h was predicted by all damage biomarkers when corrected for urine dilution: uCHI3L1 (AUC-ROC: 0.686 (95% CI, 0.580–0.780)), NGAL (0.714 (0.609–0.804)), TIMP-2 (0.830 (0.722–0.909)), IGFBP7 (0.834 (0.725–0.912)), NephroCheck® (0.774 (0.658–0.865)). After pediatric cardiac surgery, the damage biomarkers urine CHI3L1, NGAL, TIMP-2, IGFBP7, and NephroCheck® reliably predict AKI after correction for urine dilution.

Use of Renal Near-Infrared Spectroscopy and Urinary Neutrophil Gelatinase-Associated Lipocalin Monitoring as Indicators of Acute Kidney Injury in Pediatric Cardiac Surgery

Acute kidney injury (AKI) is a common complication following cardiac surgery under cardiopulmonary bypass (CPB) in children. A prospective study for examining urinary neutrophil gelatinase-associated lipocalin (NGAL) and renal near-infrared spectroscopy (NIRS) trends during AKI was conducted among pediatric patients undergoing cardiac surgery with CPB. Urinary NGAL showed a significant difference between intensive care unit admission (0 h) and 2 h post-admission (p < 0.001) and remained significant up to 4 h (p < 0.05). The renal NIRS in the AKI group showed a significant rate of decrease and lower values during the intraoperative period (p < 0.05). The cumulative median saturation of renal regional saturation of oxygen (rSO2) during CPB was 1637.5% min in the AKI group and 943.0% min in the non-AKI group. The median renal rSO2 scores at a reduction of 20% and 25% were significantly higher (p < 0.001) in the AKI group. Our results suggest that monitoring renal rSO2 scores and limiting their decline might be useful in preventing AKI. The combination of NGAL, renal rSO2, and renal rSO2 scores might be useful in the early diagnosis of AKI during pediatric cardiac surgery.

Association between nitric oxide synthase 3 genetic variant and acute kidney injury following pediatric cardiac surgery

BACKGROUND

Acute kidney injury (AKI) complicates 30% to 50% of cardiac surgeries in pediatric patients. Genetic variants that affect renal blood flow and inflammation have been associated with AKI after cardiac surgery in diverse populations of adults but have not been studied in children. The objective of this study is to test the hypothesis that common candidate genetic variants are associated with AKI following pediatric cardiac surgery.

METHODS

This is a retrospective cohort study at a single tertiary referral children's hospital of 2,062 individual patients undergoing surgery for congenital heart disease from September 2007 to July 2020. Pre-specified variants in candidate genes (AGTR1, APOE, IL6, NOS3, and TNF) were chosen. AKI was defined using Kidney Disease: Improving Global Outcomes serum creatinine criteria in the first week following surgery. Outcomes were analyzed by univariate and multivariable analysis of demographic, clinical, and genetic factors.

RESULTS

The study population had median age of 6 (interquartile range [IQR], 1-53) months, 759 (37%) of whom met criteria for postoperative AKI. In unadjusted analyses of each genetic variant, only NOS3 (rs2070744) was associated with lower risk for AKI (OR 0.75, 95% CI 0.62-0.9, P = .002). In logistic regression analyses adjusting for body surface area, previously identified genetic syndrome, Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery (STAT) score, cardiopulmonary bypass time, and nephrotoxic medication exposure, the NOS3 variant remained protective against AKI (OR 0.7, 95% CI 0.58-0.85, P<.001).

CONCLUSIONS

A common variant in NOS3 is associated with decreased incidence of AKI in children undergoing cardiac surgery. Further analysis of the genetic contributions to postoperative AKI may help identify individual risk in the pediatric population.

Evaluation of postoperative renal functions and its effect on body perfusion in patients with double aortic cannulation

BACKGROUND

The optimal visceral preservation method during aortic arch reconstruction is still controversial. It has been thought that double aortic cannulation is effective. Herein, it was aimed to evaluate this technique in providing distal perfusion.

METHODS

A total of 74 patients who underwent arch reconstruction between 2011 and 2019 were included. Patients were grouped according to ventricular physiology and cannulation strategies. Group 1 were univentricle patients, and all had double aortic cannulation. Group 2 were biventricular patients. Group 2A double aortic cannulation-done and Group 2B non-double aortic cannulation were included. Lactate, urea, creatinine values, renal functions, and need for peritoneal dialysis of patients were evaluated.

RESULTS

There were no complications observed due to descending aortic cannulation in any of the patients. A delayed sternal closure and the need for peritoneal dialysis were more common in the Group 1 (p < 0.01). The preoperative and postoperative 1st- and 2nd-day lactate, urea, and creatinine values in the Group 1 were higher (p < 0.05) when compared with the Group 2A and 2B. The same values were higher in Group 2A than the Group 2B (p < 0.05).

CONCLUSION

The positive effect of double aortic cannulation on renal dysfunction could not be demonstrated. This may be associated with a <1 month of age, low weight, complex surgical procedure, and high preoperative lactate, urea, and creatinine values in patients with double aortic cannulation.

Is there an association of near-infrared spectroscopy with low cardiac output and adverse outcomes in single-ventricle patients after stage 1 palliation?

Objective

Our primary objective study was to evaluate the association between near-infrared spectroscopy (NIRS) and low cardiac output (LCO) in patients with single-ventricle physiology after stage 1 palliation.

Methods

In this retrospective study, infants ≤6 months of age with single-ventricle physiology who underwent stage 1 palliation were included. Cerebral and renal NIRS values at various time intervals after surgery were compared between patients with low and normal cardiac output. LCO within the first 48 after surgery was defined as per the pediatric cardiac critical care consortium database. NIRS values were also compared with other adverse outcomes such as cardiac arrest, need for extracorporeal membrane oxygenation and mortality. The receiver operative characteristic curve was generated to determine an optimal cut-off NIRS value for detecting LCO.

Results

Ninety-one patients with median (Interquartile range) age of 10 days (6-26) and weight of 3.3 kg (3-3.5) were included in the study. Cerebral NIRS at 1 h (41.2 vs. 49.5; P = 0.002), 6 h (44 vs. 52.2; P = 0.001), and 12 h (51.8 vs. 56; P = 0.025) was significantly lower in the grouP with LCO compared to no LCO. Cerebral NIRS at 6 h was independently associated with LCO (P = 0.018), and cerebral NIRS at 6 h ≤57% had 91% sensitivity and 72% specificity to detect LCO.

Conclusions

Cerebral NIRS ≤57% at 6 h after surgery detected LCO after stage 1 palliation in single-ventricle patients. Cerebral or renal NIRS was not associated with adverse outcomes and therefore, may not be useful in predicting adverse outcomes in this population.

Biomarkers of acute kidney injury after pediatric cardiac surgery: a meta-analysis of diagnostic test accuracy

Acute kidney injury (AKI) occurs frequently after cardiac surgery in children. Although current diagnostic criteria rely on serum creatinine and urine output, changes occur only after considerable loss of kidney function. This meta-analysis aimed to synthesize the knowledge on novel biomarkers and compare their ability to predict AKI. PubMed/MEDLINE, Embase, Scopus, and reference lists were searched for relevant studies published by March 2021. Diagnostic accuracy parameters were extracted and analyzed using hierarchical summary receiver operating characteristic (HSROC) method. Pooled estimates of the area under the curve (AUC) were calculated using conventional random-effects meta-analysis. Fifty-six articles investigating 49 biomarkers in 8617 participants fulfilled our eligibility criteria. Data from 37 studies were available for meta-analysis. Of the 10 biomarkers suitable for HSROC analysis, urinary neutrophil gelatinase-associated lipocalin (uNGAL) to creatinine (Cr) ratio yielded the highest diagnostic odds ratio (91.0, 95% CI 90.1-91.9), with a sensitivity of 91.3% (95% CI 91.2-91.3%) and a specificity of 89.7% (95% CI 89.6-89.7%). These results were confirmed in pooled AUC analysis, as uNGAL-to-Cr ratio and uNGAL were the only elaborately studied biomarkers (> 5 observations) with pooled AUCs ≥ 0.800. Liver fatty acid-binding protein (L-FABP), serum cystatin C (sCysC), serum NGAL (sNGAL), and interleukin-18 (IL-18) all had AUCs ≥ 0.700.

CONCLUSION

A variety of biomarkers have been proposed as predictors of cardiac surgery-associated AKI in children, of which uNGAL was the most prominent with excellent diagnostic qualities. However, more consolidatory evidence will be required before these novel biomarkers may eventually help realize precision medicine in AKI management.

WHAT IS KNOWN

• Acute kidney injury (AKI) occurs in about 30-60% of children undergoing cardiac surgery and is associated with increased in-hospital mortality and adverse short-term outcomes. However, in current clinical practice, AKI definitions and detection often rely on changes in serum creatinine and urine output, which are late and insensitive markers of kidney injury. • Although various novel biomarkers have been studied for the diagnosis of AKI in children after cardiac surgery, it remains unclear how these compare to one another in terms of diagnostic accuracy.

WHAT IS NEW

• Pooled analyses suggest that for the diagnosis of AKI in children who underwent cardiac surgery, NGAL is the most accurate among the most frequently studied biomarkers. • A number of other promising biomarkers have been reported, although they will require further research into their diagnostic accuracy and clinical applicability.

Urine Biomarkers for the Assessment of Acute Kidney Injury in Neonates with Hypoxic Ischemic Encephalopathy Receiving Therapeutic Hypothermia

OBJECTIVE

To evaluate the predictive performance of urine biomarkers for acute kidney injury (AKI) in neonates with hypoxic ischemic encephalopathy (HIE) receiving therapeutic hypothermia.

STUDY DESIGN

We performed a multicenter prospective observational study of 64 neonates. Urine specimens were obtained at 12, 24, 48, and 72 hours of life and evaluated for neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), cystatin C, interleukin-18 (IL-18), tissue inhibitor of metalloproteinases 2 (TIMP2), and insulin-like growth factor-binding protein 7 (IGFBP7). Logistic regression models with receiver operating characteristics for area under the curve (AUC) were used to assess associations with neonatal modified KDIGO (Kidney Disease: Improving Global Outcomes) AKI criteria.

RESULTS

AKI occurred in 16 of 64 infants (25%). Neonates with AKI had more days of vasopressor drug use compared with those without AKI (median [IQR], 2 [0-5] days vs 0 [0-2] days; P = .026). Mortality was greater in neonates with AKI (25% vs 2%; P = .012). Although NGAL, KIM-1, and IL-18 were significantly associated with AKI, the AUCs yielded only a fair prediction. KIM-1 had the best predictive performance across time points, with an AUC (SE) of 0.79 (0.11) at 48 hours of life. NGAL and IL-18 had AUCs (SE) of 0.78 (0.09) and 0.73 (0.10), respectively, at 48 hours of life.

CONCLUSIONS

Urine NGAL, KIM-1, and IL-18 levels were elevated in neonates with HIE receiving therapeutic hypothermia who developed AKI. However, wide variability and unclear cutoff levels make their clinical utility unclear.

Biomarkers of acute kidney injury in pediatric cardiac surgery

Acute kidney injury (AKI) is characterized by a sudden decrease in kidney function. Children with congenital heart disease are a special group at risk of developing AKI. We performed a systematic review of the literature to search for studies reporting the usefulness of novel urine, serum, and plasma biomarkers in the diagnosis and progression of AKI and their association with clinical outcomes in children undergoing pediatric cardiac surgery. In thirty studies, we analyzed the capacity to predict AKI and poor outcomes of five biomarkers: Cystatin C, Neutrophil gelatinase-associated lipocalin, Interleukin-18, Kidney injury molecule-1, and Liver fatty acid-binding protein. In conclusion, we suggest the need for further meta-analyses with the availability of additional studies.

Association between Elevated Urine Neutrophil Gelatinase-Associated Lipocalin and Postoperative Acute Kidney Injury in Neonates

OBJECTIVE

To examine the incidence of postoperative neonatal acute kidney injury (AKI) following general surgical procedures and to test the hypothesis that postoperative urine neutrophil gelatinase-associated lipocalin (uNGAL) concentrations predict AKI. The secondary objective was to evaluate for an association between AKI and hospital mortality.

STUDY DESIGN

Prospective observational study of infants undergoing abdominal and thoracic surgical procedures in the neonatal intensive care unit from October 2018 to March 2020. The primary outcome was incidence of neonatal AKI (defined by the neonatal modified Kidney Diseases Improving Global Outcomes criteria) following each procedure to postoperative day 5. Severe AKI was defined as stage 2 or 3 AKI. Urine samples were obtained pre- and postoperatively at 6 time points to evaluate for levels of uNGAL. Secondary outcomes were in-hospital mortality and length of stay.

RESULTS

Subjects (n = 141) underwent a total of 192 general surgical procedures during the study period. Neonatal AKI and severe AKI occurred following 36 (18%) and 15 (8%) procedures (n = 33 subjects). Percent change of uNGAL from 24 hours preoperatively to 24 hours postoperatively was greater in subjects with neonatal AKI (190.2% [IQR 0.0, 1666.7%] vs 0.7% [IQR -31.2%,140.2%], P = .0374). The strongest association of uNGAL and AKI occurred at 24 hours postoperatively (area under the receiver operator curves of 0.81, 95% CI 0.72, 0.89). Increased mortality risk was observed in subjects with any postoperative AKI (aOR 11.1 95% CI 2.0, 62.8, P = .0063) and severe AKI (aOR 13.8; 95% CI 3.0, 63.1, P = .0007).

CONCLUSION

Elevation in uNGAL 24 hours postoperative was associated with AKI. Neonates with postoperative AKI had increased mortality.

Advances in Neonatal Acute Kidney Injury

In this state-of-the-art review, we highlight the major advances over the last 5 years in neonatal acute kidney injury (AKI). Large multicenter studies reveal that neonatal AKI is common and independently associated with increased morbidity and mortality. The natural course of neonatal AKI, along with the risk factors, mitigation strategies, and the role of AKI on short- and long-term outcomes, is becoming clearer. Specific progress has been made in identifying potential preventive strategies for AKI, such as the use of caffeine in premature neonates, theophylline in neonates with hypoxic-ischemic encephalopathy, and nephrotoxic medication monitoring programs. New evidence highlights the importance of the kidney in "crosstalk" between other organs and how AKI likely plays a critical role in other organ development and injury, such as intraventricular hemorrhage and lung disease. New technology has resulted in advancement in prevention and improvements in the current management in neonates with severe AKI. With specific continuous renal replacement therapy machines designed for neonates, this therapy is now available and is being used with increasing frequency in NICUs. Moving forward, biomarkers, such as urinary neutrophil gelatinase-associated lipocalin, and other new technologies, such as monitoring of renal tissue oxygenation and nephron counting, will likely play an increased role in identification of AKI and those most vulnerable for chronic kidney disease. Future research needs to be focused on determining the optimal follow-up strategy for neonates with a history of AKI to detect chronic kidney disease.

Brain and Muscle Oxygen Saturation Combined with Kidney Injury Biomarkers Predict Cardiac Surgery Related Acute Kidney Injury

Background: Early identification of patients at risk for cardiac surgery-associated acute kidney injury (CS-AKI) based on novel biomarkers and tissue oxygen saturation might enable intervention to reduce kidney injury. Aims: The study aimed to ascertain whether brain and muscle oxygenation measured by near-infrared spectroscopy (NIRS), in addition to cystatin C and NGAL concentrations, could help with CS-AKI prediction. Methods: This is a single-centre prospective observational study on adult patients undergoing cardiac surgery using cardiopulmonary bypass (CPB). Brain and muscle NIRS were recorded during surgery. Cystatin C was measured on the first postoperative day, while NGAL directly before and 3 h after surgery. Results: CS-AKI was diagnosed in 18 (16%) of 114 patients. NIRS values recorded 20 min after CPB (with cut-off value ≤ 54.5% for muscle and ≤ 62.5% for the brain) were revealed to be the most accurate predictors of CS-AKI. Preoperative NGAL ≥ 91.5 ng/mL, postoperative NGAL ≥ 140.5 ng/mL, and postoperative cystatin C ≥ 1.23 mg/L were identified as independent and significant CS-AKI predictors. Conclusions: Brain and muscle oxygen saturation 20 min after CPB could be considered early parameters possibly related to CS-AKI risk, especially in patients with increased cystatin C and NGAL levels.

Renal Oxygenation (rSO2) Population Parameter Estimates in Premature Infants Routinely Monitored With Near-Infrared Spectroscopy

BACKGROUND

Currently, reference ranges for renal oxygenation measured by near-infrared spectroscopy (NIRS) in preterm infants beyond the first days of life are lacking, especially those born prior to 29 weeks' gestation. Population estimates of renal oxygenation (rSO2) levels among preterm infants over time have yet to be established, leading to reluctance in clinical application.

PURPOSE

To characterize the distribution and estimate population parameters for renal oxygenation measured by NIRS during the first 14 days of life among preterm infants.

METHODS

We prospectively observed rSO2 trends of 37 infants before 34 weeks' gestation and 1800-g or less birth weight for the first 14 days of life. Analyses included distribution fit tests, ordinary least squares (OLS) regression, and t tests.

RESULTS

Average daily rSO2 variation steadily increased with 42% difference through the first 14 days of life. For all infants, renal rSO2 means peaked during the first 3 days of life and plateaued around 7 days. Daily rSO2 slopes were significantly lower among males and infants 29 weeks' or less gestation.

IMPLICATIONS FOR PRACTICE

Renal rSO2 during the first 14 days of life reflects normal extrauterine transition reaching stabilization around 7 days of life. Gestational age, birth weight, and gender may predict the early trajectory of rSO2 patterns. Population estimates provide parameters for renal rSO2 that may indicate early-onset tissue hypoxia when acute or significant drops from baseline occur.

IMPLICATIONS FOR RESEARCH

We present a framework to guide future research using renal NIRS technology in preterm infants to determine deviations from expected trends that may precede renal injury.

Fluid management, electrolytes imbalance and renal management in neonates with neonatal encephalopathy treated with hypothermia

Kidney dysfunction and acute kidney injury (AKI) frequently accompanies neonatal encephalopathy and contributes to neonatal morbidity and mortality. While there are currently no proven therapies for the treatment of AKI, understanding the pathophysiology along with early recognition and treatment of alterations in fluid, electrolyte and metabolic homeostasis that accompany AKI offer opportunity to reduce associated morbidity. Promising new tests and technologies, including urine and serum biomarkers and renal near-infrared spectroscopy offer opportunities to improve diagnosis and monitoring of neonates at risk for kidney injury. Furthermore, recent advances in neonatal kidney supportive therapies such as hemofiltration and hemodialysis may further improve outcomes in this population. This chapter provides an overview of disorders of fluid balance, electrolyte homeostasis and kidney function associated with neonatal encephalopathy and therapeutic hypothermia. Recommendations for fluid and electrolyte management based upon published literature and authors' opinions are provided.

Renal Oxygenation Measured by Near-Infrared Spectroscopy in Neonates

BACKGROUND

Acute kidney injury (AKI) affects approximately 30% of infants admitted to the neonatal intensive care unit (NICU), and increases mortality risk by 50%. Current diagnostic criteria (serum creatinine rise with oliguria) cannot detect early-onset AKI, as up to 50% of nephron damage may occur by the time these abnormalities present. Once AKI is established, clinical management is often ineffective; therefore, prevention is key. Near-infrared spectroscopy (NIRS) offers a feasible, noninvasive approach to continuously monitor renal oxygenation trends over time, serving as a surrogate marker for renal perfusion.

PURPOSE

To provide an overview of NIRS principles for measuring renal oxygenation, and to describe current evidence of how this technology is being used among infants admitted to the NICU relative to the prediction and identification of AKI.

METHODS

A comprehensive search of PubMed and CINHAL focused on renal NIRS studies in NICU preterm and term infants was conducted.

RESULTS

Findings from 34 studies were included. In term infants, reduced renal oxygenation correlated to invasive SvO2 monitoring, predicted survivability and AKI. In preterm infants, reduced renal oxygenation was associated with AKI in one study, yet contrasting findings were reported in those with patent ductus arteriosus, including those who received prostaglandin inhibitors. Normative data in all infants were sparse.

IMPLICATIONS FOR PRACTICE

Renal NIRS may offer a noninvasive measurement of kidney hypoperfusion that may precede conventional diagnostic measures.

IMPLICATIONS FOR RESEARCH

Normative data are lacking, the threshold for renal ischemia is not defined, and consensus guiding clinical treatment based on NIRS data is nonexistent.

Acute Kidney Injury in Pediatric Cardiac Intensive Care Children: Not All Admissions Are Equal: A Retrospective Study

OBJECTIVES

To describe the incidence, associated characteristics, and outcomes of the maximum severity of acute kidney injury (AKI) in a heterogeneous population of critically ill children with cardiac disease.

DESIGN

Retrospective cohort study.

SETTING

Pediatric cardiac intensive care unit (PCICU).

PARTICIPANTS

Patients admitted to the PCICU.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

From January 2018 to July 2020 all patients admitted to a tertiary PCICU were included. Only the first admission was considered. Neonates ≤seven days old were excluded. Of 742 patients, 53 were medical cases, 69 catheterization laboratory cases, and 620 surgical cases (with five subgroups). The median age was 2.47 years (interquartile range [IQR], 0.38-9.85 years), with a median Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery score of 2 (IQR, 1-3). Median PCICU length of stay was three days (IQR, 2-7 days), and 21 (2.8%) patients died. Any incidence of AKI occurred in 70% of patients, 26% of which were classified as mild (stage 1) and 43% as severe (stages 2 and 3). AKI was diagnosed by urine output criteria in 56%, serum creatinine in 28%, and both in 16% of patients. Severe AKI occurred in subgroups as follows: medical (38%), catheterization laboratory (45%), correction (35%), palliation (55%), transplantation (85%), mechanical assistance (70%), and redo surgery (58%). Severe AKI patients were significantly older (p = 0.004), had a higher Pediatric Index of Mortality 3 score (p = 0.0004), had a higher cumulative fluid balance (p < 0.0001), and had a longer cardiopulmonary bypass time (p < 0.0001). Early AKI (≤24 hours from admission) was the most frequent presentation, with a greater proportion of severe cases in the early group compared with the intermediate (>24 and ≤48 hours) and late (>48 hours) (p < 0.0001) groups. Presentation of late severe AKI had a higher mortality (odds ratio, 4.9; 95% confidence interval, 1.8-15; p = 0.001).

CONCLUSIONS

Severe AKI occurs in 43% of cardiac children and is diagnosed early, most often by urine output criteria. Severe AKI incidence varies significantly within subgroups of cardiac patients. Late AKI is associated with worse outcomes.

Near-infrared spectroscopy (NIRS) measured tissue oxygenation in neonates with gastroschisis: a pilot study

BACKGROUND

Management of gastroschisis involves either primary or staged closure. Bowel ischemia and abdominal compartment syndrome (ACS) are possible complications that can be related to a method of treatment. NIRS monitoring has never been applied in this group of patients and may allow for earlier detection of complications.

OBJECTIVE

To assess near-infrared spectroscopy (NIRS) monitoring in neonates with gastroschisis for detecting changes in tissue oxygenation (rSO₂) related to bowel reductions or height of bowel in the silo and for detecting tissue ischemia.

METHODS

Patients with gastroschisis and controls underwent continuous multi-channel assessment of oxygenation of the brain (CrSO₂), kidney (RrSO₂) and bowel (GrSO₂) in a prospective pilot study.

RESULTS

Fifteen neonates were treated with primary closure (n = 3) or staged closure (n = 12); two had confirmed bowel ischemia, none developed ACS.There was no significant correlation between height of the bowel and GrSO₂ at apex (p = .72) or base (p = .54) within the silo. During staged reductions there was a clinically non-significant change in RrSO₂ (Δ-2.5%, p = .04), but no significant changes in CrSO₂ (p = .11), and GrSO₂ of apex (p = .97) and base (p = .31). Patients with confirmed ischemia had GrSO₂ that were lower than controls.

CONCLUSIONS

Measuring GrSO₂ through a silo is feasible. Staged reduction seems safe based on NIRS measurements, with minimal effect of hydrostatic pressure on bowel oxygenation. NIRS was able to detect subtle changes in intra-abdominal renal perfusion during reduction and could differentiate healthy and ischemic bowel.

Impact on Renal Function and Hospital Outcomes of an Individualized Management of Cardiopulmonary Bypass in Congenital Heart Surgery: A Pilot Study

During cardiopulmonary bypass (CPB), high flows can allow an adequate perfusion to kidneys, but, on the other hand, they could cause emboli production, increased vascular pressure, and a more intense inflammatory response, which are in turn causes of renal damage. Along with demographic variables, other intra-operative management and post-operative events, this might lead to Acute kidney injury (AKI) in infants undergoing cardiac surgery. The aim of our study was to investigate if a CPB strategy with flow requirements based on monitoring of continuous metabolic and hemodynamic parameters could have an impact on outcomes, with a focus on renal damage. Thirty-four consecutive infants and young children undergoing surgery requiring CPB, comparable as for demographic and patho-physiological profile, were included. In Group A, 16 patients underwent, for a variable period of 20 min, CPB aiming for the minimal flow that could maintain values of MVO₂ > 70% and frontal NIRS (both left and right) > 45%, and renal NIRS > 65%. In Group B, 18 patients underwent nominal flows CPB. Tapered CPB allowed for a mean reduction of flows of 34%. No difference in terms of blood-gas analysis, spectroscopy trend, laboratory analyses, and hospital outcome were recorded. In patients developing AKI (20%), renal damage was correlated with demographic characteristics and with renal NIRS during the first 6 h in the ICU. A safe individualized strategy for conduction of CPB, which allows significant flow reduction while maintaining normal hemodynamic and metabolic parameters, does not impact on renal function and hospital outcomes.

Patterns of Urinary Neutrophil Gelatinase-Associated Lipocalin and Acute Kidney Injury in Neonates Receiving Cardiopulmonary Bypass

Elevated urinary neutrophil gelatinase-associated lipocalin (uNGAL) predicts acute kidney injury (AKI) in children following cardiopulmonary bypass (CPB) during cardiac surgery, but little is known about uNGAL’s predictive ability in neonates in this setting. We sought to determine the relationship between AKI and post-CPB uNGAL in neonates in the first 72 post-operative hours. Methods: Urine samples for uNGAL analysis were collected at preoperative baseline and serially post-operatively from 76 neonates undergoing CPB. Mixed-effects regression models and logistic models assessed associations between uNGAL and AKI (controlling for sex, gestational age, CPB time, surgical complexity, and age at surgery). Receiver-operator curves were applied to define optimal uNGAL cut-off values for AKI diagnosis. Results: Between 0 and 4 h post-operatively, uNGAL values did not differ between neonates with and without AKI. After 4 h until 16 h post-operatively, significant time-wise separation occurred between uNGAL values of neonates with AKI and those without AKI. Odds ratios at each time point significantly exceeded unity, peaking at 10 h post-operatively (3.48 (1.58, 8.71)). Between 4 and 16 h post-operatively, uNGAL discriminated AKI from no-AKI, with a sensitivity of 0.63 (0.49, 0.75) and a specificity of 0.68 (0.62, 0.74) at a cut-off value of 100 ng/mL. Conclusion: After 4 h until 16 h post-operatively, elevated uNGAL is associated with AKI in neonates receiving CPB during cardiac surgery; however, this relationship is more complex than in older children.

Early prediction of acute kidney injury in neonates with cardiac surgery

Background

Acute kidney injury (AKI) occurs in 42%–64% of the neonatal patients experiencing cardiac surgery, contributing to postoperative morbidity and mortality. Current diagnostic criteria, which are mainly based on serum creatinine and hourly urine output, are not sufficiently sensitive and precise to diagnose neonatal AKI promptly. The purpose of this review is to screen the recent literature, to summarize the novel and cost-effective biomarkers and approaches for neonatal AKI after cardiac surgery (CS-AKI), and to provide a possible research direction for future work.

Data sources

We searched PubMed for articles published before November 2019 with pertinent terms. Sixty-seven articles were found and screened. After excluding 48 records, 19 articles were enrolled for final analysis.

Results

Nineteen articles were enrolled, and 18 possible urinary biomarkers were identified and evaluated for their ability to diagnose CS-AKI. Urinary neutrophil gelatinase-associated lipocalin (uNGAL), serum cystatin C (sCys), urinary human kidney injury molecule-1 (uKIM-1), urinary liver fatty acid-binding protein (uL-FABP) and interleukin-18 (uIL-18) were the most frequently described as the early predictors of neonatal CS-AKI.

Conclusions

Neonates are vulnerable to CS-AKI. UNGAL, sCys, uL-FABP, uKIM-1 and uIL-18 are potential biomarkers for early prediction of neonatal CS-AKI. Renal regional oxygen saturation by near-infrared spectroscopy is a non-invasive approach for early identification of neonatal AKI. Further work should focus on exploring a sensitive and specific combined diagnostic model that includes novel biomarkers and other complementary methods.

Can We Still Improve Survival Outcomes of Neonatal Biventricular Repairs?

BACKGROUND

We sought to identify modifiable factors to improve survival of neonatal biventricular repair by analyzing the cause of death and predictors of mortality and reintervention in the last 2 decades.

METHODS

Between 1995 and 2016, 991 consecutive neonates were included. The cohort was divided by era: era I was from 1995 to 1999, era II 2000 to 2007, and era III 2008 to 2016. The Kaplan-Meier method was used to estimate freedom from death and reintervention. Univariable and multivariable Cox regression was applied to assess predictors for mortality or reintervention in the contemporary cohorts (2000-2016).

RESULTS

Median age was 8 days (range, 5-13), and median body weight at operation was 3.3 kg (range, 2.9-3.6). The most common diagnosis was transposition with intact ventricular septum (32%), followed by transposition with ventricular septal defect (14.5%), and simple left-to-right shunt lesion (10.9%). There was significant improvement in survival from era I to eras II and III but no difference between eras II and III (1 year: 82.1% vs 89.4% vs 89.6%, respectively; P < .001). The most common cause of death was sudden death in eras I and III and cardiac in era II. Multivariable analysis revealed preoperative (P = .005)/postoperative (P < .001) extracorporeal membrane oxygenation and postoperative renal replacement (P < .001) as independent predictors for mortality. The reintervention rates were comparable between eras II and III (P = .53). Atrioventricular septal defects and common atrial trunk were identified as predictors for reintervention.

CONCLUSIONS

Survival after neonatal biventricular repair remained unchanged. Preventing sudden death, myocardial protection, and minimizing residual lesions are potential targets to improve outcomes.

Acute Kidney Injury and Renal Regional Oxygen Saturation During Pediatric Liver Transplantation

Background

Kidney injury is a complication among children undergoing liver transplantation (pLTx). Cystatin C serum concentration seems to be superior to creatinine-based determination of kidney injury in adults and children. Near-infrared spectroscopy (NIRS) technology provides non-invasive and real-time measurement of renal tissue oxygenation. Here, we compared renal tissue oximetry (rSrO₂) with conventional diagnostic criteria cystatin C and creatinine concentration in children undergoing pLTx.

Material/Methods

rSrO₂ was measured intraoperatively in children undergoing pLTx over the left kidney, and was statistically compared with pre- and postoperative serum creatinine and cystatin C concentrations.

Results

rSrO₂ was affected by hemoglobin concentration, bilirubin concentration, and FiO₂. Statistical analysis demonstrated that rSrO₂ was significantly reduced in children with preoperative pathologic increased cystatin C concentrations compared to children without (63.7±4.3 vs. 53.4±4.9, p<0.05). We did not detect a significant difference in rSrO₂ between children who developed postoperative renal impairment, either determined by increased postoperative cystatin C concentration, creatinine concentration, or the pRIFLE criteria. Intraoperative increase or decrease in rSrO₂ did not predict the development of postoperative kidney injury.

Conclusions

In children with liver failure undergoing pLTx, a preoperative decrease in rSrO₂ indicates compromised renal function. However, intraoperative rSrO₂ is not predictive of postoperative kidney injury.

Renal Tissue Oxygenation Monitoring-An Opportunity to Improve Kidney Outcomes in the Vulnerable Neonatal Population

Adequate oxygenation of the kidney is of critical importance in the neonate. Non-invasive monitoring of renal tissue oxygenation using near-infrared spectroscopy (NIRS) is a promising bedside strategy for early detection of circulatory impairment as well as recognition of specific renal injury. As a diagnostic tool, renal NIRS monitoring may allow for earlier interventions to prevent or reduce injury in various clinical scenarios in the neonatal intensive care unit. Multiple studies utilizing NIRS monitoring in preterm and term infants have provided renal tissue oxygenation values at different time points during neonatal hospitalization, and have correlated measures with ultrasound and Doppler flow data. With the establishment of normal values, studies have utilized renal tissue oxygenation monitoring in preterm neonates to predict a hemodynamically significant patent ductus arteriosus, to assess response to potentially nephrotoxic medications, to identify infants with sepsis, and to describe changes after red blood cell transfusions. Other neonatal populations being investigated with renal NIRS monitoring include growth restricted infants, those requiring delivery room resuscitation, infants with congenital heart disease, and neonates undergoing extracorporeal membrane oxygenation. Furthermore, as the recognition of acute kidney injury (AKI) and its associated morbidity and mortality in neonates has increased over the last decade, alternative methods are being investigated to diagnose AKI before changes in serum creatinine or urine output occur. Studies have utilized renal NIRS monitoring to diagnose AKI in specific populations, including neonates with hypoxic ischemic encephalopathy after birth asphyxia and in infants after cardiac bypass surgery. The use of renal tissue oxygenation monitoring to improve renal outcomes has yet to be established, but results of studies published to date suggest that it holds significant promise to function as a real time, early indicator of poor renal perfusion that may help with development of specific treatment protocols to prevent or decrease the severity of AKI.

Serum alpha 1-antitrypsin predicts severe acute kidney injury after cardiac surgery

Background

Human alpha 1-antitrypsin (A1AT) is involved in the pathophysiological process underlying ischemic acute kidney injury (AKI). To test the hypothesis that serum A1AT (sA1AT) is a predictor for severe AKI after cardiopulmonary bypass (CPB), we conducted a prospective cohort study in 201 patients undergoing cardiac surgery.

Methods

We collected blood and urine samples, and analyzed the sA1AT and other injury biomarkers during the perioperative period. Severe AKI is defined as Kidney Disease Improving Global Outcomes (KDIGO) stage 2 or 3, and overall AKI is defined as KDIGO stage 1, 2, or 3.

Results

Ninety-one (45.3%) patients developed overall AKI, and 22 (10.9%) among them developed severe AKI after operation. sA1AT level spiked 2 hours after surgery in patients who subsequently developed severe AKI, while serum creatinine peaked 12 hours after operation. Higher postoperative sA1AT independently correlated to the development of severe AKI [OR, 1.54 (1.17-2.03); P=0.002]. The highest quartile of postoperative sA1AT level was associated with 6-fold higher hazards of severe AKI compared to the lowest quartile. Higher sA1AT levels were correlated with longer stays in the intensive care unit and the hospital. For predicting severe AKI, the AUC of sA1AT 2 hours after CPB reached 0.814. After combining with urine T cell immunoglobulin mucin-1 and clinical model, the AUC improved to 0.923.

Conclusions

In summary, sA1AT is a valuable predictor of severe AKI development and prolonged ICU and hospital stays in patients after cardiac surgery.

Near-Infrared Spectroscopy in Pediatric Congenital Heart Disease

Near-infrared spectroscopy (NIRS) is widely used to monitor tissue oxygenation in the pediatric cardiac surgical population. Clinicians who use NIRS must understand the underlying measurement principles in order to interpret and use this monitoring modality appropriately. The aims of this narrative review are to provide a brief overview of NIRS technology, discuss the normative and critical values of cerebral and somatic tissue oxygen saturation and the interpretation of these values, present the clinical studies (and their limitations) of NIRS as a perioperative monitoring modality in the pediatric congenital heart disease population, and introduce the emerging and future applications of NIRS.

Biomarkers of Inflammation, Fibrosis, and Acute Kidney Injury in Patients with Heart Failure with and without Left Ventricular Assist Device Implantation

BACKGROUND/AIMS

Renal dysfunction or renal failure is a common complication in left ventricular assist device (LVAD) recipients and is associated with reduced survival. To date, serum creatinine and glomerular filtration rate (GFR) are used for the evaluation of kidney function. However, serum creatinine and GFR have limitations. The objective of our study is to assess the levels of kidney biomarkers in LVAD recipients compared to heart failure patients and healthy controls and to examine their association with conventional clinical biomarkers.

METHODS

The biomarkers neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), plasminogen activator inhibitor-1 (PAI-1), and adiponectin were assessed in 51 participants: 19 heart failure patients, 16 LVAD recipients, and 16 healthy controls. Linear regressions were performed to assess whether demographic and clinical variables predict the levels of biomarkers that are associated with acute kidney injury and the risk of chronic kidney disease.

RESULTS

The levels of NGAL and adiponectin were higher in LVAD recipients and patients with heart failure as compared with healthy controls. The levels of PAI-1 and KIM-1 were not elevated in LVAD recipients. The results of linear regression analysis indicated that when controlling for the effect of CRP and BNP, 40.1% of the variance in NGAL levels can be explained by GFR (R2 = 0.401, F = 5.56, p = 0.005), while CRP can explain 35.3% of the variance in adiponectin levels (R2 = 0.353, F = 4.55, p = 0.01), when controlling for the effect of BNP and GFR.

CONCLUSIONS

The levels of NGAL and adiponectin were augmented in LVAD recipients, suggesting that renal functions were not restored with circulatory support. Larger studies should assess the predictability of these biomarkers of renal dysfunction in LVAD recipients.

Associations of Perioperative Renal Oximetry Via Near-Infrared Spectroscopy, Urinary Biomarkers, and Postoperative Acute Kidney Injury in Infants After Congenital Heart Surgery: Should Creatinine Continue to Be the Gold Standard?

OBJECTIVES

Examine the relationship between perioperative renal regional tissue oximetry, urinary biomarkers, and acute kidney injury in infants after congenital cardiac surgery with cardiopulmonary bypass.

DESIGN

Prospective, observational.

SETTING

Cardiac operating room and cardiac ICU.

PATIENTS

Neonates and infants without history of kidney injury or anatomic renal abnormality.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Renal regional tissue oximetry was measured intraoperatively and for 48 hours postoperatively. Urinary levels of neutrophil gelatinase-associated lipocalin and tissue inhibitor of metalloproteinases 2 together with insulin-like growth factor-binding protein 7 were measured preoperatively, 2, 12, and 24 hours postoperatively. Patients were categorized as no acute kidney injury, stage 1, or Stage 2-3 acute kidney injury using the Kidney Disease: Improving Global Outcomes criteria with 43 of 70 (61%) meeting criteria for any stage acute kidney injury. Stage 2-3 acute kidney injury patients had higher tissue inhibitor of metalloproteinases 2, insulin-like growth factor-binding protein 7 at 2 hours (0.3 vs 0.14 for stage 1 acute kidney injury and 0.05 for no acute kidney injury; p = 0.052) and 24 hours postoperatively (1.71 vs 0.27 for stage 1 acute kidney injury and 0.19 for no acute kidney injury, p = 0.027) and higher neutrophil gelatinase-associated lipocalin levels at 24 hours postoperatively (10.3 vs 3.4 for stage 1 acute kidney injury and 6.2 for no acute kidney injury, p = 0.019). Stage 2-3 acute kidney injury patients had lower mean cardiac ICU renal regional tissue oximetry (66% vs 79% for stage 1 acute kidney injury and 84% for no acute kidney injury, p = 0.038). Regression analyses showed that tissue inhibitor of metalloproteinases 2, insulin-like growth factor-binding protein 7 at 2 hours postoperatively and nadir intraoperative renal regional tissue oximetry to be independent predictors of postoperative kidney damage as measured by urinary neutrophil gelatinase-associated lipocalin.

CONCLUSIONS

We observed modest differences in perioperative renal regional tissue oximetry and urinary biomarker levels compared between acute kidney injury groups classified by creatinine-dependent Kidney Disease: Improving Global Outcomes criteria, but there were significant correlations between renal regional tissue oximetry, tissue inhibitor of metalloproteinases 2, insulin-like growth factor-binding protein 7, and postoperative neutrophil gelatinase-associated lipocalin levels. Kidney injury after infant cardiac surgery may be undetectable by functional assessment (creatinine) alone, and continuous monitoring of renal regional tissue oximetry may be more sensitive to important subclinical acute kidney injury.

Postoperative kidney oxygen saturation as a novel marker for acute kidney injury after adult cardiac surgery

OBJECTIVE

Acute kidney injury is a severe complication and one of the stronger risk factors for death in patients undergoing cardiac surgery. The relationship between postoperative brain oxygen saturation and kidney oxygen saturation with acute kidney injury in adults undergoing cardiac surgery has not been determined. We designed a single-center prospective study to determine if the continuous monitoring of postoperative brain oxygen saturation and kidney oxygen saturation could predict postoperative acute kidney injury.

METHODS

We conducted a prospective open cohort study from January to September 2017. The primary outcome was postoperative acute kidney injury using the Kidney Disease: Improving Global Outcomes criteria. Brain oxygen saturation and kidney oxygen saturation, the metrics of which were area measurements (%-min), were recorded during the surgery and the first 48 hours after the cardiac procedure. Receiver operating characteristic curve analysis was used to evaluate the predictive power of kidney oxygen saturation for acute kidney injury.

RESULTS

A total of 121 consecutive patients were enrolled. Thirty-five patients (28.9%) developed acute kidney injury. Brain oxygen saturation showed no statistical difference in both groups; however, kidney oxygen saturation was related to acute kidney injury (P = .001). Receiver operating characteristic curve analysis showed that kidney oxygen saturation could predict the risk of acute kidney injury. Kidney oxygen saturation less than 65% (area under the curve-receiver operating characteristic, 0.679 ± 0.054, 95% confidence interval, 0.573-0.785, P = .002) and 20% decrease from baseline (area under the curve-receiver operating characteristic, 0.639 ± 0.059, 95% confidence interval, 0.523-0.755, P = .019) showed the better performance, respectively.

CONCLUSIONS

Postoperative kidney oxygen saturation is related to the development of cardiac surgery-associated acute kidney injury. Continuous kidney saturation monitoring might be a promising, noninvasive tool for predicting acute kidney injury during the postoperative period for adult patients after cardiac surgery.

Subclinical acute kidney injury is associated with adverse outcomes in critically ill neonates and children

Background

Research on acute kidney injury (AKI) has focused on identifying early biomarkers. However, whether AKI could be diagnosed in the absence of the classic signs of clinical AKI and whether the condition of subclinical AKI, identified by damage or functional biomarkers in the absence of oliguria or increased serum creatinine (sCr) levels, is clinically significant remains to be elucidated in critically ill children. The aims of the study were to investigate the associations between urinary cystatin C (uCysC) levels and AKI and mortality and to determine whether uCysC-positive subclinical AKI is associated with adverse outcomes in critically ill neonates and children.

Methods

In this prospective cohort study, uCysC levels were serially measured during the first week after intensive care unit (ICU) admission in a heterogeneous group of patients (n = 510) presenting to a tertiary neonatal and pediatric ICU. The diagnosis of neonatal AKI that developed during the first week after admission was based on neonatal KDIGO criteria or sCr >1.5 mg/dL, and pediatric AKI was based on Kidney Disease: Improving Global Outcomes (KDIGO) criteria. The term “uCysC(−)” or “uCysC(+)”, indicating the absence or presence of tubular injury, was defined by the optimal peak uCysC cutoff value for predicting ICU mortality.

Results

The initial and peak uCysC levels were significantly associated with AKI and mortality, and had an area under the receiver operating characteristic curve of 0.76 and 0.81, respectively, for predicting mortality. At the optimal cutoff value of 1260 ng/mg uCr, the peak uCysC displayed sensitivity of 79.2% and specificity of 72.3% for predicting mortality. Among all patients, 130 (25.5%) developed uCysC(+)/AKI(−) status during the first week after admission. The adjusted odds ratio for patients with uCysC(+)/AKI(−) status in association with an increased risk of mortality compared with that for patients with uCysC(−)/AKI(−) was 9.34 (P < 0.001). Patients with uCysC(+)/AKI(−) spent 2.8 times as long in the ICU as those with uCysC(−)/AKI(−) (P < 0.001).

Conclusions

Both initial and peak uCysC levels are associated with AKI and mortality and are independently predictive of mortality in critically ill neonates and children. Subclinical AKI may occur without detectable loss of kidney function, and uCysC-positive subclinical AKI is associated with worse clinical outcomes in this population.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2193-8) contains supplementary material, which is available to authorized users.

Renal Saturation and Acute Kidney Injury in Neonates with Hypoxic Ischemic Encephalopathy Undergoing Therapeutic Hypothermia

OBJECTIVE

To investigate the range of renal near-infrared spectroscopy (NIRS) measures in neonates undergoing therapeutic hypothermia for hypoxic ischemic encephalopathy (HIE) and to determine the association between renal NIRS measures and the development of acute kidney injury (AKI).

STUDY DESIGN

A retrospective chart review was conducted of neonates with moderate to severe HIE who received therapeutic hypothermia at a tertiary care center from 2014 to 2016. Neonates had routine continuous NIRS monitoring of cerebral and renal saturation (Rsat) as part of their clinical care for 72 hours of cooling and until 24 hours after rewarming. The outcome of AKI was defined by an abnormal rate of decline of serum creatinine over the first 5 days of life. Mixed effects models determined the association between renal NIRS measures and AKI over time.

RESULTS

Of 38 neonates with HIE undergoing cooling, 15 (39%) developed AKI. Rsat was lower than cerebral saturation during cooling (P < .01), but Rsat increased over time after rewarming, while renal oxygen extraction levels decreased (P < .0001). Neonates with AKI had higher Rsat levels (P < .01) compared with those without AKI after 24 hours of life. Using receiver operating characteristic curves, Rsat >75% by 24-48 hours predicted AKI with a sensitivity of 79% and specificity of 82% (area under the receiver operating characteristic curve = 0.76).

CONCLUSIONS

Throughout cooling, neonates with AKI had higher Rsat measures than those without AKI. These differences may reflect lower oxygen extraction by the injured kidney. NIRS monitoring of Rsat may identify neonates with HIE at risk of developing AKI.

Association Between Early Postoperative Acetaminophen Exposure and Acute Kidney Injury in Pediatric Patients Undergoing Cardiac Surgery

IMPORTANCE

Acute kidney injury (AKI) is a common and serious complication for pediatric cardiac surgery patients associated with increased morbidity, mortality, and length of stay. Current strategies focus on risk reduction and early identification because there are no known preventive or therapeutic agents. Cardiac surgery and cardiopulmonary bypass lyse erythrocytes, releasing free hemoglobin and contributing to oxidative injury. Acetaminophen may prevent AKI by reducing the oxidation state of free hemoglobin.

OBJECTIVE

To test the hypothesis that early postoperative acetaminophen exposure is associated with reduced risk of AKI in pediatric patients undergoing cardiac surgery.

DESIGN, SETTING, AND PARTICIPANTS

In this retrospective cohort study, the setting was 2 tertiary referral children's hospitals. The primary and validation cohorts included children older than 28 days admitted for cardiac surgery between July 1, 2008, and June 1, 2016. Exclusion criteria were postoperative extracorporeal membrane oxygenation and inadequate serum creatinine measurements to determine AKI status.

EXPOSURES

Acetaminophen exposure in the first 48 postoperative hours.

MAIN OUTCOMES AND MEASURES

Acute kidney injury based on Kidney Disease: Improving Global Outcomes serum creatinine criteria (increase by ≥0.3 mg/dL from baseline or at least 1.5-fold more than the baseline [to convert to micromoles per liter, multiply by 88.4]) in the first postoperative week.

RESULTS

The primary cohort (n = 666) had a median age of 6.5 (interquartile range [IQR], 3.9-44.7) months, and 341 (51.2%) had AKI. In unadjusted analyses, those with AKI had lower median acetaminophen doses than those without AKI (47 [IQR, 16-88] vs 78 [IQR, 43-104] mg/kg, P < .001). In logistic regression analysis adjusting for age, cardiopulmonary bypass time, red blood cell distribution width, postoperative hypotension, nephrotoxin exposure, and Risk Adjustment for Congenital Heart Surgery score, acetaminophen exposure was protective against postoperative AKI (odds ratio, 0.86 [95% CI, 0.82-0.90] per each additional 10 mg/kg). Findings were replicated in the validation cohort (n = 333), who had a median age of 14.1 (IQR, 3.9-158.2) months, and 162 (48.6%) had AKI. Acetaminophen doses were 60 (95% CI, 40-87) mg/kg in those with AKI vs 70 (95% CI, 45-94) mg/kg in those without AKI (P = .03), with an adjusted odds ratio of 0.91 (95% CI, 0.84-0.99) for each additional 10 mg/kg.

CONCLUSIONS AND RELEVANCE

These results indicate that early postoperative acetaminophen exposure may be associated with a lower rate of AKI in pediatric patients who undergo cardiac surgery. Further analysis to validate these findings, potentially through a prospective, randomized trial, may establish acetaminophen as a preventive agent for AKI.

Furosemide Response Predicts Acute Kidney Injury After Cardiac Surgery in Infants and Neonates

OBJECTIVE

Cardiac surgery-induced acute kidney injury occurs frequently in neonates and infants and is associated with postoperative morbidity/mortality; early identification of cardiac surgery-induced acute kidney injury may be crucial to mitigate postoperative morbidity. We sought to determine if hourly or 6-hour cumulative urine output after furosemide in the first 24 hours after cardiopulmonary bypass could predict development of cardiac surgery-induced acute kidney injury and other deleterious outcomes.

DESIGN

Retrospective chart review.

SETTING

Pediatric cardiac ICU.

PATIENTS

All infants younger than 90 days old admitted to the cardiac ICU from October 2012 to December 2015 who received at least one dose of furosemide in the first 24 hours after cardiopulmonary bypass surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Ninety-nine patients met inclusion and exclusion criteria. In total, 45.5% developed cardiac surgery-induced acute kidney injury. Median time between cardiopulmonary bypass and furosemide was 7.7 hours (interquartile range, 4.4-9.5). Six-hour cumulative urine output was 33% lower (p = 0.031) in patients with cardiac surgery-induced acute kidney injury. Area under the curve for prediction of cardiac surgery-induced acute kidney injury was 0.69 (p = 0.002). Other models demonstrated urine output response to furosemide had significant area under the curves for prediction of peak fluid over load greater than 15% (0.68; p = 0.047), prolonged peritoneal dialysis (area under the curve, 0.79; p = 0.007), prolonged mechanical ventilation (area under the curve, 0.79; p < 0.001), prolonged hospitalization (area under the curve, 0.62; p = 0.069) and mortality (area under the curve, 0.72; p = 0.05).

CONCLUSIONS

Urine output response to furosemide within 24 hours of cardiopulmonary bypass predicts cardiac surgery-induced acute kidney injury development and other important morbidity in children younger than 90 days old; prospective validation is warranted.

Urinary Biomarkers to Predict Neonatal Acute Kidney Injury: A Review of the Science

Acute kidney injury (AKI) occurs in approximately 30% of all infants hospitalized in the neonatal intensive care unit. About 40% of very low-birth-weight infants develop AKI, with an estimated mortality rate of 50% to 80%. Very low-birth-weight survivors have twice the risk of developing chronic renal disease later in life compared with their term counterparts. Current diagnostic modalities for AKI include serum creatinine and urine output; however, recent studies suggest that these measures are imprecise, as they may not change until 25% to 50% of renal function is lost. Urinary biomarkers may more accurately identify infants at risk for early AKI development. The purpose of this review is to discuss current research findings related to neonatal AKI risk factors, provide an overview of short- and long-term outcomes, describe innovative diagnostic approaches, and identify future research direction needed to improve prediction and intervention strategies associated with renal impairment.

Near-Infrared Spectroscopy and Vascular Occlusion Test for Predicting Clinical Outcome in Pediatric Cardiac Patients: A Prospective Observational Study

OBJECTIVES

This study is designed to determine the feasibility and utility of vascular occlusion test variables as measured by INVOS Medtronic, Dublin, Ireland) in pediatric cardiac patients.

DESIGN

A prospective observational study.

SETTING

A tertiary children's hospital.

PATIENTS

Children less than or equal to 8 years old who were scheduled for elective cardiac surgery under cardiopulmonary bypass.

INTERVENTIONS

A vascular occlusion test (3 min of ischemia and reperfusion) was performed on the calf at three time points: after induction of anesthesia (T0), during cardiopulmonary bypass (T1), and after sternal closure (T2).

MEASUREMENTS AND MAIN RESULTS

Baseline regional tissue hemoglobin oxygen saturation, deoxygenation rate, minimum regional tissue hemoglobin oxygen saturation, and reoxygenation rate were measured using INVOS. Influence of age on variables at each measurement point was also checked using linear regression analysis. Receiver operating characteristics curve analysis was performed to determine the ability of vascular occlusion test variables at T2 to predict the occurrence of major adverse events. Both the deoxygenation and reoxygenation rates were lowest in T1. There was a tendency to decreased regional tissue hemoglobin oxygen saturation in younger patients at T0 (r = 0.37; p < 0.001), T1 (r = 0.33; p < 0.001), and T2 (r = 0.42; p < 0.001) during vascular occlusion. Minimum regional tissue hemoglobin oxygen saturation was correlated with age at T0 (r = 0.51; p < 0.001) and T2 (r = 0.35; p = 0.001). Patients with major adverse events had similar baseline regional tissue hemoglobin oxygen saturation but lower minimum regional tissue hemoglobin oxygen saturation (48.8% ± 19.3% vs 63.3% ± 13.9%; p < 0.001) and higher reoxygenation rate (4.30 ± 3.20 vs 2.57 ± 2.39 %/s; p = 0.008) at T2 compared with those without. The minimum regional tissue hemoglobin oxygen saturation less than 51% after sternal closure could predict the occurrence of major adverse events with a sensitivity of 61.1% and a specificity of 85.4%.

CONCLUSIONS

Vascular occlusion test using INVOS can be applied in children undergoing cardiac surgery. Vascular occlusion test variables are influenced by age and cardiopulmonary bypass. The minimum regional tissue hemoglobin oxygen saturation less than 51% after sternal closure is associated with worse clinical outcomes in pediatric cardiac patients.

Biomarkers of acute kidney injury: the pathway from discovery to clinical adoption

Acute kidney injury (AKI) is a common complication of critical illnesses and has a significant impact on outcomes, including mortality and morbidities. Unfortunately, apart from prophylactic measures, no effective treatment for this syndrome is known. Therefore, early recognition of AKI not only can provide better opportunities for preventive interventions, but also opens many gates for research and development of effective therapeutic options. Over the last few years, several new AKI biomarkers have been discovered and validated to improve early detection, differential diagnosis, and differentiation of patients into risk groups for progressive renal failure, need for renal replacement therapy (RRT), or death. These novel AKI biomarkers complement serum creatinine (SCr) and urine output, which are the standard diagnostic tools for AKI detection. In this article, we review the available literature on characteristics of promising AKI biomarkers that are currently the focus of preclinical and clinical investigations. These biomarkers include neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule 1 (KIM-1), liver-type fatty acid-binding protein, interleukin 18 (lL-18), insulin-like growth factor-binding protein 7, tissue inhibitor of metalloproteinase 2 (TIMP-2), calprotectin, urine angiotensinogen (AGT), and urine microRNA. We then describe the clinical performance of these biomarkers for diagnosis and prognostication. We also appraise each AKI biomarker's advantages and limitations as a tool for early AKI recognition and prediction of clinical outcomes after AKI. Finally, we review the current and future states of implementation of biomarkers in the clinical practice.

AKI after pediatric cardiac surgery for congenital heart diseases-recent developments in diagnostic criteria and early diagnosis by biomarkers

Background

Acute kidney injury (AKI) after cardiac surgery in children with congenital heart disease is a common complication. AKI is also associated with high morbidity and mortality. The Kidney Diseases Improving Global Outcomes (KDIGO) criteria for AKI classification are now widely used for the definition of AKI. It is noteworthy that a statement about children was added to the criteria. Many studies aimed at finding useful biomarkers are now being performed by using these criteria. Clinicians should be aware of the recent progress in understanding AKI in children.

Main contents

Unlike adult patients, young age is one of the major risk factors for AKI in pediatric cardiac surgery. The mechanism of the development of AKI in children might be different from that in adults because the surgical procedure and CPB technique in pediatric patients are greatly different from those in adult patients.

There are many biomarkers for early detection of AKI, and some of them are widely used in hospitals. One of the major benefits of such biomarkers is the rapidness of expression for detecting increases in their expression levels. Neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, cystatin C, and albumin have been investigated in some studies, and the usefulness of these biomarkers for detection of AKI and diagnosis of disease severity has been shown.

Although there are many interventions for preventing and treating AKI after cardiac surgery in children, there is still no specific effective treatment. Peritoneal dialysis is effective for only maintaining a negative fluid balance early after cardiac surgery. The long-term prognosis of AKI is an issue of interest. Although mortality and morbidity of AKI in the acute phase of disease remain high, the long-term condition in pediatric patients is relatively acceptable unlike in adults.

Conclusions

KDIGO criteria are advocated as a diagnostic tool for common perception. Early recognition and intervention for AKI can be achieved by using several biomarkers. Further studies are needed to establish effective treatment for AKI.

Investigating the Role of Near-Infrared Spectroscopy in Neonatal Medicine

Near-infrared spectroscopy (NIRS) is a clinical tool that provides a bedside method of noninvasively measuring continuous, "real-time" oxygen consumption and monitoring for potential ischemia of somatic tissues, particularly the brain, kidneys, and intestine in neonates. Although the concept of NIRS seems promising, its implementation into clinical practice has been inconsistent for various reasons, including difficulty in interpreting regional oxygen saturation (rSO2), the wide variation in types of NIRS monitors and probes, the cost of new equipment, different monitoring modalities, large discrepancies in both intra- and interindividual use, a lack of defined universal normative values, and little to no data on outcomes or potentially harmful interventions made based on rSO2 readings. We combine findings from previously published informational articles and studies on the use of NIRS in neonatal medicine to provide a comprehensive overview of this tool and identify potential indications for clinical use.

Acute kidney injury after pediatric cardiac surgery

Acute kidney injury is a common complication after pediatric cardiac surgery. The definition, staging, risk factors, biomarkers and management of acute kidney injury in children is detailed in the following review article.

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.