Renal Near-infrared Spectroscopy Research Articles

Monitoring abdominal near-infrared spectroscopy during feeds in neonates with CHD recovering from surgery: a feasibility study

Abstract Objective: Monitoring cerebral and renal near-infrared spectroscopy for regional venous oxygenation is a common practice in the postoperative care of neonates recovering from surgery for CHD. In this study, we aimed to test the feasibility of using this technology for monitoring changes in splanchnic perfusion during feeds in infants recovering from cardiac surgery. Methods: We monitored renal and splanchnic near-infrared spectroscopy in 29 neonates once recovered from the critical postoperative state and tolerating full enteral nutrition. Infants were tested over 3 feeds for splanchnic regional oxygenation (rO2), arterial to splanchnic saturation difference and splanchnic to renal regional oxygenation ratio. Result: Splanchnic regional oxygenation data were obtained with no failure or interruptions. Interclass correlation for agreement between measurements suggested good repeatability: 0.84 at baseline and 0.82 at end of feed. Infants with physiologic repair (n = 19) showed a trend towards increased splanchnic regional oxygenation at the end of feeds and were more likely to achieve regional oxygenation > 50% compared to infants with shunt-dependent circulation (n = 10, p = 0.02). Calculating AVO2 and regional oxygenation index did not result in improved test sensitivity. Conclusion: Monitoring splanchnic regional oxygenation during feeds for infants recovering from congenital heart surgery is feasible and reliable. These results suggest that near-infrared spectroscopy could be further studied as a tool for bedside monitoring to assist in feeding management and prevention of necrotising enterocolitis in this sensitive patient population.

Assessment of Autoregulation of the Cerebral Circulation during Acute Lung Injury in a Neonatal Porcine Model.

In neonates with acute lung injury (ALI), targeting lower oxygenation saturations is suggested to limit oxygen toxicity while maintaining vital organ function. Although thresholds for cerebral autoregulation are studied for the management of premature infants, the impact of hypoxia on hemodynamics, tissue oxygen consumption and extraction is not well understood in term infants with ALI. We examined hemodynamics, cerebral autoregulation and fractional oxygen extraction, as measured by near-infrared spectroscopy (NIRS) and blood gases, in a neonatal porcine oleic acid injury model of moderate ALI. We hypothesized that in ALI animals, cerebral oxygen extraction would be increased to a greater degree than kidney or gut oxygen extraction as indicative of the brain's adaptive efforts to increase cerebral oxygen extraction at the expense of splanchnic end organs. Fifteen anesthetized, ventilated 5-day-old neonatal piglets were divided into moderate lung injury by treatment with oleic acid or control (sham injection). The degree of lung injury was quantified at baseline and after establishment of ALI by blood gases, ventilation parameters and calculated oxygenation deficit, hemodynamic indices by echocardiography and lung injury score by ultrasound. PaCO2 was maintained constant during ventilation. Cerebral, renal and gut oxygenation was determined by NIRS during stepwise decreases in inspired oxygen from 50% to 21%, correlated with PaO2 and PvO2; changes in fractional oxygen extraction (ΔFOE) were calculated from NIRS and from regional blood gas samples. The proportion of cerebral autoregulation impairment attributable to blood pressure, and to hypoxemia, was calculated from autoregulation nomograms. ALI manifested as hypoxemia with increasing intrapulmonary shunt fraction, decreased lung compliance and increased resistance, and marked increase in lung ultrasound score. Brain, gut and renal NIRS, obtained from probes placed over the anterior skull, central abdomen and flank, respectively, correlated with concurrent SVC (brain) or IVC (gut, renal) PvO2 and SvO2. Cerebral autoregulation was impaired after ALI as a function of blood pressure at all FiO2 steps, but predominantly by hypoxemia at FiO2 < 40%. Cerebral ΔFOE was higher in ALI animals at all FiO2 steps. We conclude that in an animal model of neonatal ALI, cerebrovascular blood flow regulation is primarily dependent on oxygenation. There is not a defined oxygenation threshold below which cerebral autoregulation is impaired in ALI. Cerebral oxygen extraction is enhanced in ALI, reflecting compensation for exhausted cerebral autoregulation due to the degree of hypoxemia and/or hypotension, thereby protecting against tissue hypoxia.

Analysis of haemodynamics surrounding blood transfusions after the arterial switch operation: a pilot study utilising real-time telemetry high-frequency data capture.

Packed red blood cell transfusions occur frequently after congenital heart surgery to augment haemodynamics, with limited understanding of efficacy. The goal of this study was to analyse the hemodynamic response to packed red blood cell transfusions in a single cohort, as "proof-of-concept" utilising high-frequency data capture of real-time telemetry monitoring. Retrospective review of patients after the arterial switch operation receiving packed red blood cell transfusions from 15 July 2020 to 15 July 2021. Hemodynamic parameters were collected from a high-frequency data capture system (SickbayTM) continuously recording vital signs from bedside monitors and analysed in 5-minute intervals up to 6 hours before, 4 hours during, and 6 hours after packed red blood cell transfusions-up to 57,600 vital signs per packed red blood cell transfusions. Variables related to oxygen balance included blood gas co-oximetry, lactate levels, near-infrared spectroscopy, and ventilator settings. Analgesic, sedative, and vasoactive infusions were also collected. Six patients, at 8.5[IQR:5-22] days old and weighing 3.1[IQR:2.8-3.2]kg, received transfusions following the arterial switch operation. There were 10 packed red blood cell transfusions administered with a median dose of 10[IQR:10-15]mL/kg over 169[IQR:110-190]min; at median post-operative hour 36[IQR:10-40]. Significant increases in systolic and mean arterial blood pressures by 5-12.5% at 3 hours after packed red blood cell transfusions were observed, while renal near-infrared spectroscopy increased by 6.2% post-transfusion. No significant changes in ventilation, vasoactive support, or laboratory values related to oxygen balance were observed. Packed red blood cell transfusions given after the arterial switch operation increased arterial blood pressure by 5-12.5% for 3 hours and renal near-infrared spectroscopy by 6.2%. High-frequency data capture systems can be leveraged to provide novel insights into the hemodynamic response to commonly used therapies such as packed red blood cell transfusions after paediatric cardiac surgery.

Evaluation of renal near-infrared spectroscopy for predicting extubation outcomes in the pediatric intensive care setting.

In pediatric intensive care units, extubation failure following invasive mechanical ventilation poses significant health risks. Determining readiness for extubation in children can minimize associated morbidity and mortality. This study investigates the potential role of renal near-infrared spectroscopy (RrSO2) in predicting extubation failure in pediatric patients. A total of 84 patients aged between 1 month and 18 years, mechanically ventilated for at least 24 h, were included in this prospective study. RrSO2 levels were measured using near-infrared spectroscopy before and during an extubation readiness test (ERT). The primary outcome measure was extubation failure, defined as a need for reintubation within 48 h. Of the 84 patients, 71 (84.6%) were successfully extubated, while 13 (15.4%) failed extubation. RrSO2 was found to be lower in the failed extubation group, also decrease in RrSO2 values during ERT was significantly greater in patients with extubation failure. ROC analysis indicated a decrease in ΔRrSO2 of more than 6.15% from baseline as a significant predictor of extubation failure, with a sensitivity of 0.984 and a specificity of 0.889. Monitoring changes in RrSO2 values may serve as a helpful tool to predict extubation failure in pediatric patients. Further multi-center research is warranted to improve the generalizability and reliability of these findings.

Low-Dose vasopressin and renal perfusion in pediatric cardiac surgery.

Congenital heart surgeries are associated with post-bypass renal and cardiac dysfunctions. The use of low-dose vasopressin has been found to be beneficial in adult cardiac surgeries. To assess the hemodynamic and renal effects of patients undergoing on-pump pediatric cardiac surgery under general anesthesia (GA) with low-dose vasopressin infusion. Prospective randomized controlled study. Operation room and ICU, tertiary care teaching hospital. Fifty-five pediatric cardiac patients undergoing repair for congenital heart diseases (CHD). Low-dose vasopressin infusion in the study group and placebo in the control group. Renal near-infrared spectroscopy (NIRS), serum NGAL, and inflammatory mediators-IL6 and IL8 along with other renal and hemodynamic parameters in the perioperative period were recorded. Diastolic blood pressure (DBP) and cardiac index were significantly higher in the vasopressin group. Inflammatory markers were significantly high in the immediate postoperative period in all patients which later stabilized in the next 48 h but showed similar trends in both groups. Low-dose vasopressin infusion did not improve either renal perfusion or function. The duration of mechanical ventilation and length of hospital stay, the incidence of AKI development, and transfusion requirements were marginally lower in the vasopressin group, although not significant. Low-dose vasopressin infusion improved hemodynamics and showed a decreased incidence of complications. However, it failed to show any benefit of renal function and overall outcome in pediatric cardiac surgery.

Effect of retropneumoperitoneum on cerebral and renal oxygen saturation during retroperitoneal robotic-assisted laparoscopic pyeloplasty (R-RALP) in a pediatric population: Preliminary results of a prospective observational study using a dedicated anesthetic protocol and Near-InfraRed Spectroscopy

BackgroundRetroperitoneal robotic-assisted laparoscopic pyeloplasty (R-RALP) for ureteropelvic junction obstruction (UPJO) has gained growing acceptance among pediatric urologists, and is increasingly performed as day-case surgery, involving smaller children and infants. However, retroperitoneal CO2 insufflation may cause hemodynamic derangements, respiratory changes, and hypercapnia, whose consequences are poorly investigated. We, therefore, decided to prospectively study its effect on regional tissue perfusion and oxygenation in a cohort of pediatric patients undergoing R-RALP, using a dedicated anesthetic protocol and cerebral and renal Near InfraRed Spectroscopy (NIRS). Material and methodsBetween January 2021 and September 2022, a cohort of 21 consecutive children [12 males (9 females), mean age of 7.1 ± 3.8 years and mean body weight of 25.7 ± 12.3 kg] underwent their first elective pyeloplasty for UPJO by R-RALP. The surgical procedure followed a previously described standardized technique and a dedicated anesthetic protocol. In conjunction with the minimal expected standard monitoring, cerebral and renal NIRS were added. Standard monitoring parameters and NIRS values were recorded at preset points throughout the procedures. ResultsStandard monitoring and NIRS measurements during R-RALP were not adversely affected by CO2 insufflation, pending a significant increase in respiratory rate, aimed to avoid hypercapnia, while keeping the ventilation pressure within the safety range, preventing lung injury. ConclusionsR-RALP, using a constant retroperitoneal CO2 insufflation pressure of 12 mmHg with a 5 L.min−1 flow, does not adversely affect respiratory and hemodynamics parameters, pending the implementation of a specifically designed anesthetic protocol aimed to prevent hypercapnia, the most threatening effect of retroperitoneal CO2 insufflation. Clinical Trial Registration NumberNCT03274050.

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.

Descriptors of Failed Extubation in Norwood Patients Using Physiologic Data Streaming

The objective of this study is to evaluate the utility of high-frequency physiologic data during the extubation process and other clinical variables for describing the physiologic profile of extubation failure in neonates with hypoplastic left heart syndrome (HLHS) post-Norwood procedure. This is a single-center, retrospective analysis. Extubation events were collected from January 2016 until July 2021. Extubation failure was defined as the need for re-intubation within 48h of extubation. The data included streaming heart rate, respiratory rate, blood pressure, arterial oxygen saturation, and cerebral/renal near-infrared spectroscopy (NIRS). The most recent blood laboratory results before extubation were also included. These markers, demographics, clinical characteristics, and ventilatory settings were compared between successful and failed extubations. The analysis included 311 extubations. The extubation failure rate was 10%. According to univariable analyses, failed extubations were preceded by higher respiratory rates (p = 0.029), lower end-tidal CO2 (p = 0.009), lower pH (p = 0.043), lower serum bicarbonate (p = 0.030), and lower partial pressure of O2 (p = 0.022). In the first 10min after extubation, the failed events were characterized by lower arterial (p = 0.028) and cerebral NIRS (p = 0.018) saturations. Failed events were associated with persistently lower values for cerebral NIRS 2h post-extubation (p = 0.027). In multivariable analysis, vocal cord anomaly, cerebral NIRS at 10min post-extubation, renal NIRS at pre-extubation and post-extubation, and end-tidal CO2 at pre-extubation remained as significant co-variables. Oximetric indices before, in the 10min immediately after, and 2h after extubation and vocal cords paralysis are associated with failed extubation events in patients with parallel circulation.

Agreement of somatic and renal near-infrared spectroscopy with reference blood samples during a controlled hypoxia sequence: a healthy volunteer study

Purpose: O3® Regional Oximetry (Masimo Corporation, California, USA) is validated for cerebral oximetry. We aimed to assess agreement of somatic and renal near-infrared spectroscopy with reference blood samples. Methods: O3 sensors were placed bilaterally on the quadriceps and flank of 26 healthy volunteers. A stepped, controlled hypoxia sequence was performed by adding a mixture of nitrogen and room air to the breathing circuit. O3-derived oxygen saturation values were obtained at baseline and at six decremental saturation levels (5% steps). Blood samples (radial artery, iliac vein (somatic reference) and renal vein) were obtained at each step. Reference values were calculated as: 0.7 × venous saturation + 0.3 × arterial saturation. The agreement between O3-derived values with blood reference values was assessed by calculating root-mean-square error accuracy and Bland-Altman plots. Results: The root-mean-square error accuracy was 6.0% between quadriceps oxygen saturation and somatic reference values. The mean bias was 0.8%, with limits of agreement from -7.7 to 9.3%. These were 5.1% and 0.6% (-8.3 to 9.5%) for flank oxygen saturation and somatic reference values, respectively, and 7.7% and -4.9% (-15.0 to 5.2%) for flank oxygen saturation and renal reference values. The kidney depth was 3.1 ± 0.9 cm below the skin. Conclusion: O3 regional oximetry can be used on the quadriceps and flank to monitor somatic saturation, yet has a saturation-level dependent bias. O3-derived values obtained at the flank underestimated renal reference values. Additionally, it is unlikely that the flank sensors did directly measure renal tissue. Trial registration: Clinicaltrials.gov (NCT04584788): registered October 6th, 2020.

Acute Effects of Sodium Bicarbonate in Children with Congenital Heart Disease with Biventricular Circulation in Non-cardiac Arrest Situations.

Despite the controversy, sodium bicarbonate is a commonly used medication in critically ill patients of all ages. There is a lack of data on the acute impact on hemodynamic parameters, biomarker indicators of cardiac output, and changes in vasoinotropic support after sodium bicarbonate therapy. In our retrospective study on children with biventricular circulation in pediatric cardiac intensive care unit receiving bicarbonate therapy: we analyzed its effects on arterial blood gases, heart rate, blood pressure (BP), central venous pressures (CVP), cerebral and renal near-infrared spectroscopy (NIRS), changes in vasoinotropic and ventilator changes before and after sodium bicarbonate administration. Thirty-one administrations of sodium bicarbonate in 23 patients with congenital heart disease without residual shunts were analyzed. The average age was 15.4months, weight 7.7kg, and the average bicarbonate dose was 1meq/kg. There was an increase in arterial pH from 7.24 to 7.30 (p = 0.14) and bicarbonate changed from 18 to 20mEq/L (p = 0.23). No clinically significant changes were found in the following parameters: heart rate (141 ± 20.1 to 136 ± 19), systolic BP (84 ± 17 to 86 ± 14mmHg), diastolic BP (48 ± 12 to 49 ± 12mmHg), cerebral NIRS (64 ± 12 to 65 ± 12), renal NIRS (80 ± 10 to 81 ± 7), CVP (9 ± 3 to 10 ± 4mmHg), paCO2 (45 ± 26 to 42 ± 7mmHg), paO2 (143 ± 78 to 127 ± 59mmHg), serum lactate (2.2 ± 2.7 to 3.6 ± 3.8mmol/L), and vasoinotropic score (7.5 ± 5.0 to 7.7 ± 4.7). Outside of a change in serum pH and bicarbonate levels no other significant changes were noted after sodium bicarbonate administration in children with congenital heart disease with fully septated, biventricular circulation. There was no improvement in systemic oxygen delivery.

Intraoperative and Postoperative Hemodynamic Predictors of Acute Kidney Injury in Pediatric Heart Transplant Recipients

AbstractAcute kidney injury (AKI) is common after pediatric heart transplantation (HT) and is associated with inferior patient outcomes. Hemodynamic risk factors for pediatric heart transplant recipients who experience AKI are not well described. We performed a retrospective review of 99 pediatric heart transplant patients at Lucile Packard Children's Hospital Stanford from January 1, 2015, to December 31, 2019, in which clinical and demographic characteristics, intraoperative perfusion data, and hemodynamic measurements in the first 48 postoperative hours were analyzed as risk factors for severe AKI (Kidney Disease: Improving Global Outcomes [KDIGO] stage ≥ 2). Univariate analysis was conducted using Fisher's exact test, Chi-square test, and the Wilcoxon rank-sum test, as appropriate. Multivariable analysis was conducted using logistic regression. Thirty-five patients (35%) experienced severe AKI which was associated with lower intraoperative cardiac index (p = 0.001), higher hematocrit (p &lt; 0.001), lower body temperature (p &lt; 0.001), lower renal near-infrared spectroscopy (p = 0.001), lower postoperative mean arterial blood pressure (MAP: p = 0.001), and higher central venous pressure (CVP; p &lt; 0.001). In multivariable analysis, postoperative CVP &gt;12 mm Hg (odds ratio [OR] = 4.27; 95% confidence interval [CI]: 1.48–12.3, p = 0.007) and MAP &lt;65 mm Hg (OR = 4.9; 95% CI: 1.07–22.5, p = 0.04) were associated with early severe AKI. Children with severe AKI experienced longer ventilator, intensive care, and posttransplant hospital days and inferior survival (p = 0.01). Lower MAP and higher CVP are associated with severe AKI in pediatric HT recipients. Patients, who experienced AKI, experienced increased intensive care unit (ICU) morbidity and inferior survival. These data may guide the development of perioperative renal protective management strategies to reduce AKI incidence and improve patient outcomes.

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.

Results of Less Than 5-mm Right Ventricle-Pulmonary Artery Conduits in Single Ventricle Palliation

Our programmatic approach to single ventricle (SV) neonatal palliation has evolved to using smaller-size right ventricle to pulmonary artery (RV-PA) conduits for pulmonary blood flow. Therefore, we sought to compare the early outcomes of less than 5-mm versus 5-mm RV-PA conduits in SV patients undergoing neonatal palliation. We performed a retrospective review of SV patients who had neonatal palliation with either a less than 5-mm or 5-mm RV-PA connection, constructed using a waterproof, breathable fabric membrane graft (Gore-Tex, Flagstaff, AZ). Data before, during, and after surgery were analyzed using SPSS software. A total of 26 patients in group 1 (n= 11; <5 mm) and group 2 (n= 15; 5 mm) were operated on, with a mean follow-up of 13 months. Statistical differences (P ≤ .05) were noted with renal near-infrared spectroscopy (mean, 56 versus 44), and oxygen saturation at discharge (mean, 80% versus 85%) in groups 1 and 2, respectively. We found no significant difference in patient weight, peak lactate, cerebral near-infrared spectroscopy, length of intubation, length of hospitalization, or need for RV-PA conduit intervention after stage 1 along with age, branch PA sizes, or need for PA plasty at bidirectional Glenn between groups. Our early results of less than 5-mm conduits support further exploration into the tailoring of the RV-PA conduit size for each patient. A smaller-diameter conduit may improve systemic cardiac output and net oxygen delivery. Larger patient cohorts and longer follow-up with assessment of pulmonary artery growth are warranted to guide clinical practice.

Renal Near-Infrared Spectroscopy for Assessment of Renal Oxygenation in Adults Undergoing Cardiac Surgery: A Method Validation Study

To investigate the correlation between invasively measured renal venous oxygen saturation (SrvO2) and tissue oxygenation (rSO2) measured with near-infrared spectroscopy (NIRS) in adult patients undergoing cardiac surgery. Prospective observational study. Single cardiac surgery center at a university hospital. Thirteen adult patients with skin- to- kidney distance ≤4 cm undergoing open cardiac surgery with cardiopulmonary bypass (CPB). All patients received renal vein catheters for invasive measurement of SrvO2, and NIRS electrodes for assessment of renal rSO2 were placed over the kidney using ultrasound guidance. Measurements were made before CPB, during CPB at 3 different flow rates (2.4, 2.7, and 3.0 L/min/m2), and after CPB. Repeated- measures correlation analyses and Bland-Altman plots were used to study the correlation and agreement between rSO2 and SrvO2. For all measurement points, renal rSO2 correlated with SrvO2 (rrm = 0.61, p < 0.001), and the mean difference (bias) between rSO2 and SrvO2 was -2.71 ± 7.22 (p = 0.002), with an error of 17.6%. When measurements during CPB and before and after CPB were studied separately, rSO2 and SrvO2 were correlated (rrm = 0.51, p < 0.007 and rrm = 0.73, p < 0.001, respectively). During CPB, renal rSO2 predicted SrvO2 with a bias of -3.41 ± 7.76 (p = 0.009) and an error of 18.8%. Before and after CPB, the mean difference was -1.93 ± 6.60 (p = 0.092), with an error of 16.2%. Renal rSO2 is correlated to and predicts SrvO2 with a small bias and acceptable agreement. Further studies are needed before renal NIRS can be used as a surrogate marker of renal oxygenation in clinical practice.

Comparison of Bilateral Cerebro-Renal Tissue Oxygenations in Healthy Children.

To investigate right and left cerebral tissue (ctSO2) and renal tissue oxygenations (rtSO2) in otherwise healthy children. In this observational cross-sectional study, one hundred children seen as outpatients for well child care or common non-critical complaints, were included. Bilateral ctSO2 and rtSO2 were recorded simultaneously with INVOS™ 5100 device. The median age was 6.7 y (IQR 3-10.4) andmedian weight was 21kg (IQR 13-33). Right and left sided ctSO2 and rtSO2 values were 78.7% ± 6.0% and 79.1% ± 5.7%; 81.5% ± 9.4% and 81.4% ± 9.5% respectively. There were no differences in right and left cerebral and renal near infrared spectroscopy (NIRS) values, and no age centered lateralization effect. Renal measurements were higher than cerebral counterparts in 63% of the children. Interaction between age and regional oxygenation was significant. For both sides, renal oxygenation was higher than that of cerebrum in older children, whereas the opposite held true with younger age. There are no right and left side differences in ctSO2 and rtSO2 values in otherwise healthy children. On the other hand, there seem to be differences between cerebral and renal regions with a significant age effect. Acknowledging its limitations, this study sheds light on laterality and cranial and renal NIRS measurements in otherwise healthy children, and may contribute to the interpretation of NIRS data in critically ill patients.

Acute Effects of Hypoxic Gas Admixtures on Pulmonary Blood Flow and Regional Oxygenation in Children Awaiting Norwood Palliation.

IntroductionOxygen delivery in patients with functionally univentricular hearts awaiting Norwood palliation depends on a balance between systemic blood flow (Qs) and pulmonary blood flow (Qp). Modulations of pulmonary vascular resistance and systemic vascular resistance are utilized to maintain balanced Qp:Qs in a circulation prone to pulmonary overcirculation at the expense of systemic perfusion. This study aimed to characterize changes in Qp:Qs and regional (cerebral and renal) oxygen delivery in patients awaiting Norwood palliation receiving hypoxic gas admixture therapy.MethodsPatients who received care prior to Norwood palliation were identified from 2014 to 2018. Of these patients, those with cerebral and renal near-infrared spectroscopy were identified (NIRS). Arterial oxygen saturation by pulse oximetry, renal NIRS, and cerebral NIRS prior to hypoxic gas admixture initiation were compared to values six hours, 12 hours, and 24 hours after initiation.ResultsA total of 28 patients were eligible for inclusion in the study. Arterial saturation by pulse oximetry was 91% prior to initiation and decreased to 86% 24 hours after initiation (p<0.001). Cerebral NIRS were a mean of 60 prior to initiation compared to 58 at 24 hours (p=0.187). Renal NIRS were a mean of 60 prior to initiation compared to 57 at 24 hours (p=0.120). Calculated Qp:Qs was 9.6 at baseline compared to 2.5 at 24 hours (p=0.006). Arteriovenous difference and lactate did not significantly change with hypoxic gas admixture administration.ConclusionAdministration of hypoxic gas admixture to patients with functionally univentricular hearts awaiting Norwood palliation decreases the ratio of Qp and Qs but does not improve regional oxygenation delivery.

Near-infrared spectroscopy for prediction of extubation success after neonatal cardiac surgery.

Reliable predictors of extubation readiness are needed and may reduce morbidity related to extubation failure. We aimed to examine the relationship between changes in pre-extubation near-infrared spectroscopy measurements from baseline and extubation outcomes after neonatal cardiac surgery. In this retrospective cross-sectional multi-centre study, a secondary analysis of prospectively collected data from neonates who underwent cardiac surgery at seven tertiary-care children's hospitals in 2015 was performed. Extubation failure was defined as need for re-intubation within 72 hours of the first planned extubation attempt. Near-infrared spectroscopy measurements obtained before surgery and before extubation in patients who failed extubation were compared to those of patients who extubated successfully using t-tests. Near-infrared spectroscopy measurements were available for 159 neonates, including 52 with single ventricle physiology. Median age at surgery was 6 days (range: 1-29 days). A total of 15 patients (9.4 %) failed extubation. Baseline cerebral and renal near-infrared spectroscopy measurements were not statistically different between those who were successfully extubated and those who failed, but pre-extubation cerebral and renal values were significantly higher in neonates who extubated successfully. An increase from baseline to time of extubation values in cerebral oximetry saturation by ≥ 5 % had a positive predictive value for extubation success of 98.6 % (95%CI: 91.1-99.8 %). Pre-extubation cerebral near-infrared spectroscopy measurements, when compared to baseline, were significantly associated with extubation outcomes. These findings demonstrate the potential of this tool as a valuable adjunct in assessing extubation readiness after paediatric cardiac surgery and warrant further evaluation in a larger prospective study.

Elevated renal tissue oxygenation in premature fetal growth restricted neonates: An observational study.

BackgroundFetal growth restriction (FGR) is associated with an increased risk for kidney disease in later life. Studies reporting on early signs of renal disturbances in FGR are sparse and mostly include invasive measurements, which limit the possibility for early identification and prevention. We aim to investigate whether renal tissue oxygen saturation (rSO2) measured with near-infrared spectroscopy (NIRS) and the derived value fractional tissue oxygen extraction (FTOE) differ between premature FGR and control neonates in the first three days after birth.MethodsNine FGR and seven control neonates born <32 weeks of gestation were included. FGR was defined as biometry <p10 combined with prenatal signs of placental insufficiency. Renal rSO2 was measured continuously with NIRS for 72 hours. FTOE was calculated as: (arterial saturation-rSO2)/arterial saturation. Renal artery blood flow (pulsatility and resistance index) was measured within 24 hours after birth. A linear mixed model approach was used (intercept ± slope = r) to analyze the NIRS parameters.ResultsRenal rSO2 was higher in FGR neonates compared to controls (94% vs. 83%; pgroup = 0.002). During the first three days after birth, renal rSO2 decreased in FGR neonates and increased in controls (r = -0.25 vs. r = 0.03; pinteraction = 0.001). Renal FTOE was lower in FGR neonates (0.02 vs. 0.14; pgroup = 0.01) and increased slightly during three days after birth, while it remained stable in controls (r = 0.003 vs. r = -0.0001; pinteraction = 0.001). Renal artery blood flow was similar between groups.ConclusionsFGR neonate kidneys showed higher rSO2 as measured with NIRS and lower derived values of FTOE in the first three days after birth. We speculate that this was caused by either a reduced oxygen consumption due to impaired renal maturation or increased renal oxygen supply. How these observations correlate with short- and long-term renal function needs further investigation before renal NIRS can be implemented in screening and prevention in clinical practice.

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

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). 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. 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). 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.

Use of renal near-infrared spectroscopy measurements in congenital diaphragmatic hernia patients on ECMO

IntroductionThis study tests the hypothesis that renal tissue oxygen saturation as measured by Near Infrared Spectroscopy (NIRS) would correlate with urine output in neonates with congenital diaphragmatic hernia (CDH) on extracorporeal membrane oxygenation (ECMO). MethodsBetween 2012 and 2015, neonates with CDH were enrolled as part of a comprehensive study that provided renal/cerebral/abdominal NIRS monitoring for the duration of ECMO support. Continuous NIRS measurements, mean arterial pressure, and urine output were recorded. Periods of anuria (NU), adequate urine output >1ml/kg/h (AU), and low urine output <1ml/kg/h (LU) were noted and analyzed. ResultsOver 1500h of continuous renal NIRS were obtained from six neonates. NIRS values were significantly different during periods of AU, LU, and anuria (84±6%, 76±3%, and 67±6%, p<0.01). ROC curves identified NIRS >76% as highly predictive of adequate urine output (AUC=0.96). MAP was significantly lower only in anuric patients, 36.42±10.26, compared to patients with AU and LU - 42.99±5.25 and 42.85±7.4, respectively (p<0.001). ConclusionRenal NIRS measurements correlate with urine production. Lower values are noted as urine output declines and precedes a decline in MAP. Renal NIRS may have promise as a non-invasive means of determining adequacy of renal perfusion and urine output in neonates with complex fluid shifts. Level of evidenceIIb.