A noninvasive estimation of mixed venous oxygen saturation using near-infrared spectroscopy by cerebral oximetry in pediatric cardiac surgery patients

Regional Cerebral Oxygen Saturation and Estimated Oxygen Extraction Ratio as Predictive Markers of Major Adverse Events in Infants with Congenital Heart Disease

Regional cerebral oxygen saturation (ScO2) determined by near-infrared spectroscopy, monitoring both arterial and venous blood oxygenation of the brain, could reflect the balance between oxygen delivery and consumption. The aim of this study was to determine the predictabilities of ScO2 and estimated oxygen extraction ratio (eO2ER) with outcomes in infants with congenital heart disease (CHD). This study was a two-center, retrospective study of patients at 12 months of age or younger with CHD who underwent cardiac surgery. The primary outcome was a composite of one or more major adverse events (MAEs) after surgery: death from any cause, circulatory collapse that needed cardiopulmonary resuscitation, and requirement for extracorporeal membrane oxygenation. Based on the assumptions of arterial to venous blood ratio, eO2ER was calculated. A total of 647 cases were included in this study. MAEs occurred in 16 patients (2.5%). There were significant differences in post-bypass ScO2 [46.61 (40.90, 52.05) vs. 58.52 (51.52, 66.08), p < 0.001] and post-bypass eO2ER [0.66 (0.60, 0.78) vs. 0.52 (0.43, 0.61), p < 0.001] between patients with MAEs and patients without MAEs. Area under the receiver operating curve (AUROC) of post-bypass ScO2 was 0.818 (95% confidence interval: 0.747-0.889), AUROC of post-bypass eO2ER was 0.783 (0.697-0.870) and AUROC of post-bypass maximum serum lactate level was 0.635 (0.525-0.746). Both ScO2 and eO2ER, especially after weaning off bypass, are acceptable predictive markers for predicting MAEs after cardiac surgery in infants.(227 words).

First Characterization of Tissue Oxygen Saturation Recovery Patterns in Pediatric Cardiac Surgery Patients Undergoing Remote Ischemic Preconditioning and the Association With Clinical Outcomes

OBJECTIVE

This study aimed to delineate the recovery patterns of regional oxygen saturation (SrO2) in pediatric cardiac surgery patients subjected to remote ischemic preconditioning (RIPC), utilizing near-infrared spectroscopy (NIRS) for quantification. It also sought to establish the correlation between these perfusion patterns and postoperative clinical outcomes.

DESIGN

A prospective longitudinal observational study.

SETTING

The study was conducted at Fundación Valle Del Lili, a high-complexity service provider institution in Fundación Valle Del Lili.

PARTICIPANTS

Pediatric patients (younger than 18 years of age) scheduled for elective cardiac surgery requiring cardiopulmonary bypass between August 2022 and July 2023.

INTERVENTIONS

RIPC was performed after anesthetic induction, involving cycles of ischemia and reperfusion on a lower limb. Monitoring included SrO2 using NIRS.

MEASUREMENTS AND MAIN RESULTS

The study identified 4 distinct patterns of SrO2 during RIPC. Findings demonstrated a significant association between the negative SrO2 pattern and increased postoperative adverse events, including extended hospital stays and higher mortality, while a positive pattern was associated with better outcomes.

CONCLUSIONS

Specific patterns of SrO2 response to RIPC may serve as important indicators for risk stratification in congenital heart surgery. This study illustrated the potential of NIRS in detecting hypoxic states and predicting postoperative outcomes, emphasizing the need for standardized clinical interpretation of RIPC patterns.

Understanding Near-Infrared Spectroscopy: An Update

Near-infrared spectroscopy (NIRS) is a novel technology that uses infrared light to noninvasively and continuously measure regional oxygen extraction in real time at the bedside. Neonatal research using this device supports its use as an adjunct to routine cardiovascular monitoring because NIRS serves as a surrogate marker for end-organ perfusion and can detect minute changes in cerebral, intestinal, and kidney tissue beds. Multiple conditions affecting premature infants are frequently associated with hypoperfusion; therefore, methods to detect early tissue-specific perfusion alterations may substantially improve the clinician's ability to intervene and prevent further deterioration.

Noninvasive tracking of mixed venous oxygen saturation via near-infrared spectroscopy cerebral oximetry: a retrospective observational study

Although previous studies have shown correlation between regional cerebral oxygen saturation (rScO2) and mixed venous oxygen saturation (SvO2), there is a lack of pragmatic information on the clinical applicability of these findings, such as tracking ability. We retrospectively analyzed continuous intraoperative recordings of rScO2 and SvO2 obtained from a pulmonary artery catheter and either of two near-infrared spectroscopy (NIRS) devices (INVOS 5100C, Medtronic; O3, Masimo) during off-pump cardiopulmonary bypass (OPCAB) surgery in adult patients. The ability of rScO2 to track SvO2 was quantitatively evaluated with 5 min interval changes transformed into relative values. The analysis included 176 h of data acquired from 48 subjects (26 and 22 subjects for INVOS and O3 dataset, respectively). The area under ROC of the left-rScO2 for detecting change of SvO2 ≥ 10% in INVOS and O3 datasets were 0.919 (95% CI 0.903-0.936) and 0.852 (95% CI 0.818-0.885). The concordance rates between the interval changes of left-rScO2 and SvO2 in INVOS and O3 datasets were 90.6% and 91.9% with 10% exclusion zone. rScO2 can serve as a noninvasive tool for detecting changes in SvO2 levels, a critical hemodynamic measurement.

Effect of Red Blood Cell Transfusion on Regional Tissue Oxygenation in Pediatric Cardiac Surgery Patients

BACKGROUND

Red blood cell (RBC) transfusions are used frequently in pediatric patients admitted to the intensive care unit (ICU) after cardiac surgery. To improve data-driven transfusion decision-making in the ICU, we conducted a retrospective analysis to assess the effect of RBC transfusion on cerebral and somatic regional oxygenation (rSO2).

METHODS

We evaluated post- versus pre-RBC transfusion cerebral rSO2 and somatic rSO2 in all consecutive pediatric patients (age >28 days to <18 years) who underwent biventricular cardiac surgery at a single center between July 2016 and April 2020.

RESULTS

The final data set included 263 RBC postoperative transfusion events in 75 patients who underwent 83 surgeries. The median pretransfusion hemoglobin was 10.6 g/dL (25th-75th percentile, 9.3-11.6). The median pretransfusion cerebral and somatic rSO2 were 63% (54-71) and 69% (55-80), which increased by a median of 3 percentage points (-2 to 6) and 2 percentage points (-3 to 6), respectively, after transfusion. After adjusting for pretransfusion hemoglobin, change in hemoglobin posttransfusion versus pretransfusion, and potential confounders (age, sex, and STAT surgical mortality risk score), the posttransfusion versus pretransfusion change in cerebral or somatic rSO2 was not statistically significant. Pretransfusion cerebral rSO2 (crSO2) was ≤50%, a previously described threshold for increased risk for unfavorable neurological outcome, for 22 of 138 (16%) transfusion events with complete pre- and post-crSO2 data. Sixteen of these 22 (73%) transfusions resulted in a posttransfusion crSO2 >50%. When restricting analysis to the first (index) transfusion after arrival to the ICU from the operating room (administered at a median of 1.15 postoperative days [25th-75th percentile, 0.84-1.93]), between-patient pretransfusion hemoglobin was not associated with pretransfusion crSO2 but within-patient posttransfusion versus pretransfusion hemoglobin difference was significantly associated with posttransfusion versus pretransfusion crSO2 difference (mean posttransfusion versus pretransfusion crSO2 difference, 2.54; 95% confidence interval, 0.50-4.48).

CONCLUSIONS

In this study, neither cerebral nor somatic rSO2 increased significantly post- versus pre-RBC transfusion in pediatric cardiac surgery patients admitted to the ICU after biventricular repairs. However, almost three-quarters of transfusions administered when pretransfusion crSO2 was below the critical threshold of 50% resulted in a posttransfusion crSO2 >50%. In addition, the significant within-patient change in crSO2 in relation to the change in posttransfusion versus pretransfusion hemoglobin in the immediate postoperative period suggests that a personalized approach to transfusion following within-patient trends of crSO2 rather than absolute between-patient values may be an important focus for future research.

Do Cerebral Cortex Perfusion, Oxygen Delivery, and Oxygen Saturation Responses Measured by Near-Infrared Spectroscopy Differ Between Patients Who Fail or Succeed in a Spontaneous Breathing Trial? A Prospective Observational Study

BACKGROUND

Alterations in perfusion to the brain during the transition from mechanical ventilation (MV) to a spontaneous breathing trial (SBT) remain poorly understood. The aim of the study was to determine whether changes in cerebral cortex perfusion, oxygen delivery (DO₂), and oxygen saturation (%StiO₂) during the transition from MV to an SBT differ between patients who succeed or fail an SBT.

METHODS

This was a single-center prospective observational study conducted in a 16-bed medical intensive care unit of the University Hospital Leuven, Belgium. Measurements were performed in 24 patients receiving MV immediately before and at the end of a 30-min SBT. Blood flow index (BFI), DO₂, and %StiO₂ in the prefrontal cortex, scalene, rectus abdominis, and thenar muscle were simultaneously assessed by near-infrared spectroscopy using the tracer indocyanine green dye. Cardiac output, arterial blood gases, and systemic oxygenation were also recorded.

RESULTS

During the SBT, prefrontal cortex BFI and DO₂ responses did not differ between SBT-failure and SBT-success groups (p > 0.05). However, prefrontal cortex %StiO₂ decreased in six of eight patients (75%) in the SBT-failure group (median [interquartile range 25-75%]: MV = 57.2% [49.1-61.7] vs. SBT = 51.0% [41.5-62.5]) compared to 3 of 16 patients (19%) in the SBT-success group (median [interquartile range 25-75%]: MV = 65.0% [58.6-68.5] vs. SBT = 65.1% [59.5-71.1]), resulting in a significant differential %StiO₂ response between groups (p = 0.031). Similarly, a significant differential response in thenar muscle %StiO₂ (p = 0.018) was observed between groups. A receiver operating characteristic analysis identified a decrease in prefrontal cortex %StiO₂ > 1.6% during the SBT as an optimal cutoff, with a sensitivity of 94% and a specificity of 75% to predict SBT failure and an area under the curve of 0.79 (95% CI: 0.55-1.00). Cardiac output, systemic oxygenation, scalene, and rectus abdominis BFI, DO₂, and %StiO₂ responses did not differ between groups (p > 0.05); however, during the SBT, a significant positive association in prefrontal cortex BFI and partial pressure of arterial carbon dioxide was observed only in the SBT-success group (SBT success: Spearman's ρ = 0.728, p = 0.002 vs. SBT failure: ρ = 0.048, p = 0.934).

CONCLUSIONS

This study demonstrated a reduced differential response in prefrontal cortex %StiO₂ in the SBT-failure group compared with the SBT-success group possibly due to the insufficient increase in prefrontal cortex perfusion in SBT-failure patients. A > 1.6% drop in prefrontal cortex %StiO₂ during SBT was sensitive in predicting SBT failure. Further research is needed to validate these findings in a larger population and to evaluate whether cerebral cortex %StiO₂ measurements by near-infrared spectroscopy can assist in the decision-making process on liberation from MV.

Validation of the Masimo O3™ regional oximetry device in pediatric patients undergoing cardiac surgery

We assessed the accuracy of Masimo O3™ regional cerebral oxygen saturation (rSO₂) readings by comparing them with reference values and evaluated the relationship between rSO₂ and somatic tissue oxygen saturation (StO₂) in children undergoing cardiac surgery. After anesthesia induction, pediatric sensors were applied to the forehead and foot sole, and rSO₂ and StO₂ values were monitored continuously. Before cardiopulmonary bypass (CPB), F_IO₂ was set to 0.2, 0.5, and 0.8 serially every 15 min. After CPB, F_IO₂ was reversed. The reference values (SavO₂) were calculated by combining arterial (SaO₂) and central venous oxygen saturation (SvO₂) readings from the arterial and central lines, respectively (0.7 [Formula: see text] SvO₂ + 0.3 [Formula: see text] SaO₂). In total, 265 pairs of rSO₂/StO₂ and SavO₂ from 49 patients were analyzed. The bias, standard deviation (SD), standard error (SE), and root mean squared error (RMSE) of rSO₂ were 2.6%, 4.5%, 0.3%, and 4.3%, respectively. The limits of agreement ranged from -6.3% to 11.6%. Trend accuracy analysis yielded a relative mean error of -1.4%, with an SD of 4.3%, SE of 0.2%, and RMSE of 3.9%. According to multiple linear regression analysis, the application of CPB, F_IO₂, Hb level, and tip location of the central venous catheter influenced the bias (all P < 0.05). Furthermore, the correlation between rSO₂ and StO₂ was weak (r = 0.254). rSO₂ readings by the Masimo O3™ device and pediatric sensor had good absolute and trending accuracies with respect to the calculated reference values in children undergoing cardiac surgery. rSO₂ and StO₂ cannot be used interchangeably.Clinical trial registration http://clinicaltrials.gov (number: NCT04208906).

Recent advancements in pediatric cardiopulmonary bypass technology for better outcomes of pediatric cardiac surgery

Background

Pediatric cardiac surgery is in itself very enigmatic and individualized. Presently, there has been a slew of new developments aimed primarily toward pediatric cardiopulmonary bypass for safer, patient-centered pediatric cardiac surgery. Still, lot of technological challenges need to be resolved, and their safer application in pediatric and neonate patients requires further refinement.

Main body of the abstract

Considering various significant yet unresolved issues of pediatric cardiac bypass, an exhaustive literature search was done on various internet databases with standard keywords. There are various new recent improvements; as the first oxygenator explicitly designed for neonatal patients; pediatric oxygenators with low prime volumes and surface areas that allow flows up to 2 L/min; pediatric oxygenators with integrated arterial filters; and miniature ultrafiltration devices that allow for high rates of ultrafiltrate removal. These advancements can significantly reduce cardiopulmonary bypass circuit surface areas and prime volumes. These advancements could reduce or eliminate the requirement for homologous red blood cells during or after surgery with reduction or eliminate bypass-related hemodilution, and inflammation. Because of the immaturity of the neonatal hemostatic system, conventional coagulation tests alone are insufficient to guide neonatal hemostatic therapy. Myocardial preservation techniques, safe temperature with duration are still debatable and yet to be fully explored.

Short conclusion

This review is based on Standards for Quality Improvement Reporting Excellence guidelines to provide a framework for reporting new knowledge to find better management strategy for pediatric cardiac cases.

Comparing near-infrared spectroscopy-measured cerebral oxygen saturation and corresponding venous oxygen saturations in children with congenital heart disease: a systematic review and meta-analysis

BACKGROUND

Near-infrared spectroscopy (NIRS) is a non-invasive approach that measures cerebral regional oxygen saturation (rScO₂). In this study, we evaluated the evidence on the validity of NIRS and the interchangeability between NIRS and common invasive approaches by exploring the correlation and consistency and comparing the mean and standard deviation between the NIRS rScO₂ and jugular bulb venous oxygen saturation (SjvO₂) as well as central venous oxygen saturation (ScvO₂) in the perioperative period of children with congenital heart disease (CHD).

METHODS

We searched electronic bibliographic databases (PubMed, The Cochrane Library and Embase) and screened the studies that met the inclusion criteria. We included cross-sectional studies of CHD pediatric patients in the perioperative period receiving both tests for NIRS rScO₂ and SjvO₂ or NIRS rScO₂ and ScvO₂. Methodological quality assessment and heterogeneity analyses were performed. We qualitatively summarized the results of Bland-Altman's analysis. Meta-regression, subgroup analyses, and sensitivity analyses were carried out to explore the causes of heterogeneity.

RESULTS

There was no significant difference in Cohen's d between rScO₂ and ScvO₂ or between rScO₂ and SjvO₂ (Cohen's d =0.06, 95% CI: -0.16 to 0.28; Cohen's d =0.03, 95% CI: -0.25 to 0.31, respectively) and notable heterogeneity existed (I²=76.0%, P<0.001; I²=73.6%, P<0.001, respectively). A positive linear correlation was present between rScO₂ and ScvO₂ or between rScO₂ and SjvO₂ (r=0.58, 95% CI: 0.54 to 0.63; r=0.60, 95% CI: 0.54 to 0.66, respectively) and the heterogeneity was not significant (I²=36.7%, P=0.065; I²=12.7%, P=0.328, respectively). In most studies, the 95% limits of agreements of Bland-Altman's analysis were large. No evidence of publication bias was observed.

CONCLUSIONS

The rScO₂ measured by NIRS reflected the SjvO₂ and ScvO₂ monitored by invasive measurements in the perioperative period of children with CHD to some extent. However, wide limits of agreements between rScO₂ and SjvO₂ as well as ScvO₂ indicated that NIRS and SjvO₂ as well as ScvO₂ are not interchangeable. Whether NIRS plays a prominent role in monitoring cerebral oxygen saturation in children with CHD needs further research.

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.

Can central-venous oxygen saturation be estimated from tissue oxygen saturation during a venous occlusion test?

OBJECTIVE

To test whether tissue oxygen saturation (StO2) after a venous occlusion test estimates central venous oxygen saturation (ScvO2).

METHODS

Observational study in intensive care unit patients. Tissue oxygen saturation was monitored (InSpectra Tissue Spectrometer Model 650, Hutchinson Technology Inc., MN, USA) with a multiprobe (15/25mm) in the thenar position. A venous occlusion test in volunteers was applied in the upper arm to test the tolerability and pattern of StO2 changes during the venous occlusion test. A sphygmomanometer cuff was inflated to a pressure 30mmHg above diastolic pressure until StO2 reached a plateau and deflated to 0mmHg. Tissue oxygen saturation parameters were divided into resting StO2 (r-StO2) and minimal StO2 (m-StO2) at the end of the venous occlusion test. In patients, the cuff was inflated to a pressure 30mmHg above diastolic pressure for 5 min (volunteers' time derived) or until a StO2 plateau was reached. Tissue oxygen saturation parameters were divided into r-StO2, m-StO2, and the mean time that StO2 reached ScvO2. The StO2 value at the mean time was compared to ScvO2.

RESULTS

All 9 volunteers tolerated the venous occlusion test. The time for tolerability or the StO2 plateau was 7 ± 1 minutes. We studied 22 patients. The mean time for StO2 equalized ScvO2 was 100 sec and 95 sec (15/25mm probes). The StO2 value at 100 sec ([100-StO2] 15mm: 74 ± 7%; 25mm: 74 ± 6%) was then compared with ScvO2 (75 ± 6%). The StO2 value at 100 sec correlated with ScvO2 (15 mm: R2 = 0.63, 25mm: R2 = 0.67, p < 0.01) without discrepancy (Bland Altman).

CONCLUSION

Central venous oxygen saturation can be estimated from StO2 during a venous occlusion test.

A new physiologic-based integrated algorithm in the management of neonatal hemodynamic instability

Physiologic-based management of hemodynamic instability is proven to guide the logical selection of cardiovascular support and shorten the time to clinical recovery compared to an empiric approach that ignores the heterogeneity of the hemodynamic instability related mechanisms. In this report, we classified neonatal hemodynamic instability, circulatory shock, and degree of compensation into five physiologic categories, based on different phenotypes of blood pressure (BP), other clinical parameters, echocardiography markers, and oxygen indices. This approach is focused on hemodynamic instability in infants with normal cardiac anatomy.Conclusion: The management of hemodynamic instability is challenging due to the complexity of the pathophysiology; integrating different monitoring techniques is essential to understand the underlying pathophysiologic mechanisms and formulate a physiologic-based medical recommendation and approach. What is Known: • Physiologic-based assessment of hemodynamics leads to targeted and pathophysiologic-based medical recommendations. What is New: • Hemodynamic instability in neonates can be categorized according to the underlying mechanism into five main categories, based on blood pressure phenotypes, systemic vascular resistance, and myocardial performance. • The new classification helps with the targeted management and logical selection of cardiovascular support.

The acute influence of vasopressin on hemodynamic status and tissue oxygenation following the Norwood procedure

Objectives

Arginine vasopressin (AVP) is used to treat hypotension. Because AVP increases blood pressure by increasing systemic vascular resistance, it may have an adverse effect on tissue oxygenation following the Norwood procedure.

Methods

Retrospective analysis of continuously captured hemodynamic data of neonates receiving AVP following the Norwood procedure.

Results

We studied 64 neonates exposed to AVP within 7 days after the Norwood procedure. For the entire group, AVP significantly increased mean blood pressure (2.5 ± 6.3) and cerebral and renal oxygen extraction ratios (4.1% ± 9.6% and 2.0% ± 4.7%, respectively; P < .001 for all values). In the right ventricle to pulmonary artery shunt cohort, AVP significantly increased blood pressure, arterial oxygen saturation (1.4% ± 3.8%; P = .011), pulmonary to systemic perfusion ratio (0.2 ± 0.4; P = .017), and cerebral and renal oxygen extraction ratios (4.6% ± 8.7%; P = .010% and 4.7% ± 9.4%; P = .014, respectively). The Blalock-Taussig shunt cohort experienced a less significant vasopressor response and no change in arterial oxygen saturation, pulmonary to systemic perfusion ratio, or cerebral and renal oxygen extraction ratios.

Conclusions

The right ventricle to pulmonary artery shunt cohort experienced a significant vasopressor response to AVP that was associated with a significant increase in pulmonary perfusion and decrease in cerebral and renal perfusion, whereas the Blalock-Taussig shunt cohort experienced a less significant vasopressor response and no change in pulmonary or systemic perfusion. The influence of AVP on tissue oxygenation following the Norwood procedure may have clinical implications that require further study.

Diagnostic Validation Study. Relationship Between Optical Spectroscopy and Ankle Brachial Index Tests for Peripheral Artery Disease

INTRODUCTION

Ankle brachial index (ABI) is an essential diagnostic test for peripheral artery disease. It has some important limitations so it can´t always be performed. In those cases, tissue oximetry based on near-infrared spectrum could overcome these limitations.

OBJECTIVES

Assessment of the relationship between ABI and tissue oximetry tests and the ability of the oximetry to detect postoperative improvement.

METHOD AND MATERIALS

Prospective observational study. Several measures were made by both, ankle pressure and tissue oximetry tests, in lower limbs. Absolute values were collected at foot level (anterior and posterior tibial arteries) and the indexes were calculated in relation to a control (upper limbs for ABI and left infraclavicular region for tissue oximetry). In order to evaluate the correlation between ankle pressure and tissue oximetry values, Pearson correlation coefficient and linear regression analyses were applied. T-Student and ROC curve analysis were made to evaluate the postoperative improvement detected by both ankle pressure and tissue oximetry tests.

RESULTS

60 patients with peripheral artery disease were included. Ankle pressure and tissue oximetry were measured in 70 lower limbs, in 45 of them before and after revascularization. Compared to ankle pressure, tissue oximetry was able to detect improvement in absolute values and indexes after revascularization. This indexes improvement was parallel (P=0.234 for anterior tibial artery and P=0.356 for posterior tibial artery). We weren´t able to determine a cutoff point between both tests (ROC curve analysis). We observed a significative positive correlation in absolute values of both tests (Pearson correlation coefficient, r = 0,281; P < 0.001).

CONCLUSION

Tissue oximetry is able to detect improvement after revascularization of lower limbs.

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.

Cerebral regional oxygen saturation variability in neonates following cardiac surgery

BACKGROUND

Reduced cerebral regional oxygen saturation (crSO₂) variability in neonates, as measured by near-infrared spectroscopy, following cardiac surgery with deep hypothermic circulatory arrest (DHCA) is associated with poor neurodevelopmental outcomes. We sought to evaluate the variability of crSO₂ in a cohort of neonates following cardiac surgery with brief or no exposure to DHCA.

METHODS

Variability of averaged 1-min crSO₂ values was calculated for the first 48 h following cardiac surgery in consecutive neonates over a 30-month period. Neonates requiring aortic arch repair underwent antegrade cerebral perfusion with either brief or no exposure to DHCA.

RESULTS

There were 115 neonates included in the study. Reduced crSO₂ variability was observed in neonates with aortic arch obstruction (p = 0.02) and non-survivors (p = 0.02). Post hoc analysis demonstrated that the reduction in crSO₂ variability was not as marked as in previously studied neonates with aortic arch obstruction who received DHCA alone (p < 0.001).

CONCLUSIONS

Neonates with aortic arch obstruction have reduced crSO₂ variability following cardiac surgery. The reduction in crSO₂ variability observed in aortic arch obstruction is likely influenced by a number of factors, including perioperative perfusion technique. The impact of interventions on crSO₂ variability and resultant influence on neurodevelopmental outcomes requires further study.

IMPACT

Neonates with aortic arch obstruction have reduced crSO₂ variability following cardiac surgery, which has been associated with poor neurodevelopmental outcomes, and is likely influenced by a number of factors, including perioperative perfusion technique. The contribution of perioperative perfusion technique to crSO₂ variability following neonatal cardiac surgery is significant. Monitoring of crSO₂ variability may provide insights into the adequacy of cerebral perfusion in neonates following cardiac surgery.

Comparison of bilateral cerebral and somatic tissue oxygenation with near-infrared spectroscopy in cyanotic and acyanotic pediatric patients receiving cardiac surgery

INTRODUCTION

Compromise of tissue oxygenation during surgery is associated with increased mortality and morbidity in the postoperative period in patients with congenital cardiac disorders. It may be monitored with near-infrared spectroscopy (NIRS). We aimed to evaluate the tissue oxygenation and factors which may affect it by bilateral cerebral and somatic NIRS levels during cardiopulmonary bypass and to compare the NIRS values of cyanotic and acyanotic patient groups.

MATERIAL AND METHODS

Two groups of patients with cyanotic and acyanotic congenital heart diseases were included in the study. Each group consisted of 15 patients between 0 and 5 years of age. All data were collected following anesthesia induction (T1), the 10th (T2) and 30th min (T3) of cardiopulmonary bypass (CPB), every 30 min during CPB (T4, T5, T6) and 1 h after (TS). Bilateral and somatic NIRS, blood gases, mean arterial pressure, and temperatures were recorded.

RESULTS

Left and right somatic NIRS values in groups at all measurements did not differ significantly. Left and right cerebral NIRS values at T2 and T3 in cyanotic patients were significantly higher than in acyanotic patients. Mean arterial pressure and lactate levels at T1 and T3 measurements were responsible for left cerebral NIRS changes and mean arterial pressure on right cerebral NIRS values.

CONCLUSIONS

Monitorization of tissue perfusion has critical importance during CPB of patients with congenital heart defects. Oxygenation may easily and reliably be measured with NIRS. Cerebral and somatic NIRS are more pronounced in cyanotic patients and cerebral NIRS is strongly associated with mean arterial pressure and circulating lactate levels.

Noninvasive monitoring of central venous oxygen saturation by jugular transcutaneous near-infrared spectroscopy in pediatric patients undergoing congenital cardiac surgery

Background and aim

In patients undergoing congenital cardiac surgery, it is crucial to maintain oxygen demand-consumption balance. Central venous oxygen saturation (ScvO₂) is a useful indicator of oxygen demand and consumption balance which is an invasive method. Near-infrared spectroscopy (NIRS) is a noninvasive, continuous monitoring technique that measures regional tissue oxygenation. NIRS that is placed over the internal jugular vein cutaneous area (NIRSijv) has the potential to show ScvO₂ indirectly. In this study, we aimed to determine the correlation between ScvO₂ with NIRSijv in pediatric patients undergoing congenital cardiac surgery.

Materials and methods

Fifty children participated in the study. Four patients were excluded for the inability of internal jugular vein (IJV) catheterization due to technical difficulties. After anesthesia induction, NIRS probes were placed on the IJV site with ultrasound guidance for the measurement of continuous transcutaneous oxygen saturation. The catheter insertion was also done through the IJV from the other side using ultrasound guidance. Cerebral oxygenation monitoring was done using NIRS with a single pediatric probe placed on the right forehead. Values of NIRSijv, cerebral NIRS (NIRSc) and ScvO₂, were recorded at certain times until postoperative 24th hour.

Results

Data were collected at 8 different time points. There was a significant correlation between ScvO₂ and NIRSijv in all measurement time points (r = 0.91), (P = 0.001). The mean bias between ScvO₂ and NIRSijv was 2.92% and the limits of agreement were from 11% to –5.2%. There was a moderate correlation between ScvO₂ and NIRSc (r = 0.45), (P = 0.001). The mean bias between ScvO₂ and NIRSc was 2.7% and the limits of agreement were from +26% to –20%.

Conclusion

In this study, we found a strong correlation between ScvO₂ and NIRS measurements taken from the internal jugular vein site. Accordingly, continuous noninvasive monitoring with transcutaneous NIRSijv can be an alternative method as a trend monitor for the central venous oxygen saturation in pediatric cardiac patients undergoing congenital cardiac surgery.

Near-Infrared Spectroscopy in Extremely Preterm Infants

With advances in neonatal care, survival of premature infants at the limits of viability has improved significantly. Despite these improvement in mortality, infants born at 22-24 weeks gestation are at a very high risk for short- and long-term morbidities associated with prematurity. Many of these diseases have been attributed to abnormalities of tissue oxygenation and perfusion. Near-infrared spectroscopy utilizes the unique absorption properties of oxyhemoglobin and deoxyhemoglobin to provide an assessment of regional tissue oxygen saturation, which can be used to calculate the fractional tissue oxygen extraction. This allows for a non-invasive way to monitor tissue oxygen consumption and enables targeted hemodynamic management. This mini-review provides a brief and complete overview of the background and physiology of near-infrared spectroscopy, practical use in extremely preterm infants, and potential applications in the neonatal intensive care unit. In this mini-review, we aim to summarize the three primary application sites for near-infrared spectroscopy, disease-specific indications, and available literature regarding use in extremely preterm infants.

Cardiopulmonary Resuscitation in Infants and Children With Cardiac Disease: A Scientific Statement From the American Heart Association

Cardiac arrest occurs at a higher rate in children with heart disease than in healthy children. Pediatric basic life support and advanced life support guidelines focus on delivering high-quality resuscitation in children with normal hearts. The complexity and variability in pediatric heart disease pose unique challenges during resuscitation. A writing group appointed by the American Heart Association reviewed the literature addressing resuscitation in children with heart disease. MEDLINE and Google Scholar databases were searched from 1966 to 2015, cross-referencing pediatric heart disease with pertinent resuscitation search terms. The American College of Cardiology/American Heart Association classification of recommendations and levels of evidence for practice guidelines were used. The recommendations in this statement concur with the critical components of the 2015 American Heart Association pediatric basic life support and pediatric advanced life support guidelines and are meant to serve as a resuscitation supplement. This statement is meant for caregivers of children with heart disease in the prehospital and in-hospital settings. Understanding the anatomy and physiology of the high-risk pediatric cardiac population will promote early recognition and treatment of decompensation to prevent cardiac arrest, increase survival from cardiac arrest by providing high-quality resuscitations, and improve outcomes with postresuscitation care.

Let us save the brain with cerebral oximeter: Two case reports

In the neonates, tracheal atresia and tracheoesophageal fistula (TEF) surgery may result in hemodynamic instabilization, leading to cerebral perfusion insufficiency due to the retraction of the pulmonary vessels and truncus brachiocephalicus. We represented one male and one female neonates which were performed thoracoscopic primary repair of TEF through right thoracotomy at the 3^th and 4^th postpartum day. Anesthesia was induced using sodium thiopental (5 mg/kg), fentanyl 4 mcg, and rocuronium (0.5 mg/kg) given through intravenous route. Sevoflurane 2% and 50% O₂in air were used for the maintenance therapy. During the right lung compression to expose posterior esophagus, no value was observed on the pulse oximeter (PO) probe placed on the right hand, and radial artery was not palpated. At the same time, oxygen saturation was observed as 96%-97% on the left foot probe. As the right cerebral oximeter values (rSO₂) were rapidly decreased to 31%, the lung compression was ceased. Right pulse oximeter and right rSO₂measurements return to the baseline levels. For the second case - different from the first case -both left and right rSO₂was rapidly decreased to 40% levels and return to the baseline levels after was removed the retractors. Right PO and right and left cerebral rSO₂values returned to baseline immediately when the retractor compression was ended During the operations involving the great vessels in neonates, cerebral perfusion could be preserved using cerebral oximeter. Cerebral oximeter is more efficient than pulse oximeter for detecting cerebral tissue oxygenation and could be helpful to minimize neuronal damage in the neonates.

Transposition of the Great Arteries and Common Variants

OBJECTIVES

The objectives of this review are to discuss the physiology, perioperative management, surgical correction, and outcomes of infants with transposition of the great arteries and common variants undergoing the arterial switch operation.

DATA SOURCE

MEDLINE and PubMed.

CONCLUSION

The widespread adoption of the arterial switch operation for transposition of great arteries has been one of the more gratifying advances in pediatric cardiovascular care, and represents the simultaneous improvements in diagnostics, surgical and bypass techniques, anesthesia in the neonate, improvements in intensive care technology, nursing strategies, and system-wide care delivery. Many of the strategies adopted for the neonate with transposition of the great arteries have been translated to neonatal care for other congenital heart lesions. Continued work is necessary to investigate the effects of perioperative care on long-term neurodevelopmental outcomes, as well as collaboration between centers to spread "best practices" for outcome, cost, and morbidity reduction.

Near Infrared Spectroscopy as a Hemodynamic Monitor in Critical Illness

OBJECTIVES

The objectives of this review are to discuss the technology and clinical interpretation of near infrared spectroscopy oximetry and its clinical application in patients with congenital heart disease.

DATA SOURCE

MEDLINE and PubMed.

CONCLUSION

Near infrared spectroscopy provides a continuous noninvasive assessment of tissue oxygenation. Over 20 years ago, near infrared spectroscopy was introduced into clinical practice for monitoring cerebral oxygenation during cardiopulmonary bypass in adults. Since that time, the utilization of near infrared spectroscopy has extended into the realm of pediatric cardiac surgery and is increasingly being used in the cardiac ICU to monitor tissue oxygenation perioperatively.

Mesenteric near-infrared spectroscopy and risk of gastrointestinal complications in infants undergoing surgery for congenital heart disease

We hypothesised that lower mesenteric near-infrared spectroscopy values would be associated with a greater incidence of gastrointestinal complications in children weighing <10 kg who were recovering from cardiac surgery. We evaluated mesenteric near-infrared spectroscopy, central venous oxygen saturation, and arterial blood gases for 48 hours post-operatively. Enteral feeding intake, gastrointestinal complications, and markers of organ dysfunction were monitored for 7 days. A total of 50 children, with median age of 16.7 (3.2-31.6) weeks, were studied. On admission, the average mesenteric near-infrared spectroscopy value was 71±18%, and the systemic oxygen saturation was 93±7.5%. Lower admission mesenteric near-infrared spectroscopy correlated with longer time to establish enteral feeds (r=-0.58, p<0.01) and shorter duration of feeds at 7 days (r=0.48, p<0.01). Children with gastrointestinal complications had significantly lower admission mesenteric near-infrared spectroscopy (58±18% versus 73±17%, p=0.01) and higher mesenteric arteriovenous difference of oxygen at admission [39 (23-47) % versus 19 (4-27) %, p=0.02]. Based on multiple logistic regression, admission mesenteric near-infrared spectroscopy was independently associated with gastrointestinal complications (Odds ratio, 0.95; 95% confidence interval, 0.93-0.97; p=0.03). Admission mesenteric near-infrared spectroscopy showed an area under the receiver operating characteristic curve of 0.76 to identify children who developed gastrointestinal complications, with a suggested cut-off value of 72% (78% sensitivity, 68% specificity). In this pilot study, we conclude that admission mesenteric near-infrared spectroscopy is associated with gastrointestinal complications and enteral feeding tolerance in children after cardiac surgery.

A Cross-Sectional Survey of Near-Infrared Spectroscopy Use in Pediatric Cardiac ICUs in the United Kingdom, Ireland, Italy, and Germany

OBJECTIVES

Despite the increasing use of near-infrared spectroscopy across pediatric cardiac ICUs, there is significant variability and equipoise with no universally accepted management algorithms. We aimed to explore the use of near-infrared spectroscopy in pediatric cardiac ICUs in the United Kingdom, Ireland, Italy, and Germany.

DESIGN

A cross-sectional multicenter, multinational electronic survey of one consultant in each pediatric cardiac ICU.

SETTING

Pediatric cardiac ICUs in the United Kingdom and Ireland (n = 13), Italy (n = 12), and Germany (n = 33).

INTERVENTIONS

Questionnaire targeted to establish use, targets, protocols/thresholds for intervention, and perceived usefulness of near-infrared spectroscopy monitoring.

RESULTS

Overall, 42 of 58 pediatric cardiac ICUs (72%) responded: United Kingdom and Ireland, 11 of 13 (84.6%); Italy, 12 of 12 (100%); and Germany, 19 of 33 (57%, included all major centers). Near-infrared spectroscopy usage varied with 35% (15/42) reporting that near-infrared spectroscopy was not used at all (7/42) or occasionally (8/42); near-infrared spectroscopy use was much less common in the United Kingdom (46%) when compared with 78% in Germany and all (100%) in Italy. Only four units had a near-infrared spectroscopy protocol, and 18 specifically used near-infrared spectroscopy in high-risk patients; 37 respondents believed that near-infrared spectroscopy added value to standard monitoring and 23 believed that it gave an earlier indication of deterioration, but only 19 would respond based on near-infrared spectroscopy data alone. Targets for absolute values and critical thresholds for intervention varied widely between units. The reasons cited for not or occasionally using near-infrared spectroscopy were expense (n = 6), limited evidence and uncertainty on how it guides management (n = 4), difficulty in interpretation, and unreliability of data (n = 3). Amongst the regular or occasional near-infrared spectroscopy users (n = 35), 28 (66%) agreed that a multicenter study is warranted to ascertain its use.

CONCLUSIONS

Although most responding units used near-infrared spectroscopy for high-risk patients, the majority (31/35 [88%]) did not have any protocols or guidelines for intervention. Target thresholds and intervention algorithms are needed to support the use of near-infrared spectroscopy in pediatric cardiac ICUs; an international multicenter study is warranted.

Comparison of Minimally and More Invasive Methods of Determining Mixed Venous Oxygen Saturation

OBJECTIVE

To investigate the accuracy of a minimally invasive, 2-step, lookup method for determining mixed venous oxygen saturation compared with conventional techniques.

DESIGN

Single-center, prospective, nonrandomized, pilot study.

SETTING

Tertiary care hospital, university setting.

PARTICIPANTS

Thirteen elective cardiac and vascular surgery patients.

INTERVENTIONS

All participants received intra-arterial and pulmonary artery catheters. Minimally invasive oxygen consumption and cardiac output were measured using a metabolic module and lithium-calibrated arterial waveform analysis (LiDCO; LiDCO, London), respectively. For the minimally invasive method, Step 1 involved these minimally invasive measurements, and arterial oxygen content was entered into the Fick equation to calculate mixed venous oxygen content. Step 2 used an oxyhemoglobin curve spreadsheet to look up mixed venous oxygen saturation from the calculated mixed venous oxygen content. The conventional "invasive" technique used pulmonary artery intermittent thermodilution cardiac output, direct sampling of mixed venous and arterial blood, and the "reverse-Fick" method of calculating oxygen consumption.

MEASUREMENTS AND MAIN RESULTS

LiDCO overestimated thermodilution cardiac output by 26%. Pulmonary artery catheter-derived oxygen consumption underestimated metabolic module measurements by 27%. Mixed venous oxygen saturation differed between techniques; the calculated values underestimated the direct measurements by between 12% to 26.3%, this difference being statistically significant.

CONCLUSION

The magnitude of the differences between the minimally invasive and invasive techniques was too great for the former to act as a surrogate of the latter and could adversely affect clinical decision making.

A retrospective study about cerebral near-infrared spectroscopy monitoring during paediatric cardiac surgery and intra-operative patient blood management

OBJECTIVES

Cerebral non-invasive monitoring of oxygen saturation by near-infrared spectroscopy (rSO2) during paediatric cardiac surgery is supposed to decrease the risk of neurological complications. Since haemoglobin level is one of the factors changing rSO2, we aimed to explore if rSO2 monitoring influences intra-operative RBC (red blood cell) transfusion threshold and volumes, as well as the duration of ICU stay.

METHODS

The design was a retrospective analysis involving 91 children less than 2 years of age (including 16 neonates) with a congenital heart disease requiring surgical treatment with or without cardiopulmonary bypass from January 2006 to August 2009. Systematic rSO2 monitoring was introduced after September 2007 (n=56). The independent factors associated with the intra-operative transfusion threshold haemoglobin (Hb) level>9.5g/dL, total volume of intra-operative RBC transfusion<30mL/kg and ICU stay<6 days were identified by multivariate analysis logistic regression. Data were expressed as medians (25-75%).

RESULTS

Cardiac malformations and demographic characteristics were similar in both periods. Two independent factors, weight and rSO2 monitoring, were identified as independent factors associated with the three end-points. The transfusion threshold, total transfusion volume and ICU stay with and without rSO2 were 9.8 (8.9 to 10.3) versus 8.7 (8.2 to 9.6) g/dL (P<0.0001), 20 (14-49) versus 36 (22.5-51.5) mL/kg (P=0.0165) and 5 (3-8) versus 7 (5-10.7) days (P=0.0084), respectively.

CONCLUSION

rSO2 monitoring changed our transfusion strategy with an earlier transfusion but a reduced total RBC volume and decreased the length of ICU stay.

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

OBJECTIVE

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

DESIGN

A prospective observational pilot study.

SETTING

An intensive care unit in North West England.

PATIENTS

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

INTERVENTIONS

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

MEASUREMENT AND MAIN RESULTS

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

CONCLUSIONS

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

Challenges and controversies in fetal diagnosis and treatment: hypoplastic left heart syndrome

Today, almost 70% of babies with hypoplastic left heart syndrome (HLHS) will survive into adulthood, although significant long-term morbidity and mortality still exists. Prenatal diagnosis of HLHS is increasingly common, allowing improved counseling, and the potential for fetal intervention if indicated. Exciting progress continues to be made in the area of fetal diagnosis and intervention, specifically catheter intervention for intact atrial septum or severe aortic stenosis. Pediatric cardiologists should be keenly aware of the flaws of staged palliation for the treatment of HLHS, and need to keep abreast of the emerging data regarding fetal diagnosis and intervention.

Near-infrared Spectroscopy to Assess Cerebral Perfusion during Head-up Tilt-table Test in Patients with Syncope

OBJECTIVE

Neurocardiogenic syncope (NCS) is the most common cause of syncope in children and adolescents. Neurocardiogenic syncope occurs secondary to cerebral hypotension because of bradycardia, hypotension, or both. Head-up tilt-table test (HUTT) is the primary diagnostic test. Near-infrared spectroscopy (NIRS) is a noninvasive technology that directly monitors trends in regional tissue oxygen saturations over a specific body region. Placing an NIRS probe over the temporal region allows an indirect measurement of cerebral perfusion. Our hypothesis is that regional tissue oxygen saturation will decrease during an NCS episode and will remain stable in patients without syncope.

PATIENTS AND DESIGN

The investigators conducted a retrospective review of all HUTT utilizing cephalic NIRS performed at our institution from August 2012 to January 2013. Tests were classified as positive, negative, or psychogenic reactions. Paired t-test was used to determine statistical significance of NIRS changes and one-way analysis of variance was used to analyze baseline characteristics among the three groups.

RESULTS

Twelve patients were included in the study (female = 10). The average age was 14.4 years (range: 12-17). Five tests were positive for NCS, four were negative, and three demonstrated psychogenic reactions. Patients with a positive test had a sudden, significant decrease in regional tissue oxygen saturations (P = .009) by an average of 11.3 ± 5.2% compared with baseline. The decrease in regional tissue oxygen saturation preceded symptoms, hypotension, and bradycardia in all patients. Regional tissue oxygen saturation levels remained stable in patients with a negative test or psychogenic syncope.

CONCLUSIONS

NIRS monitoring during HUTT produces a reliable, positive result that precedes clinical signs and symptoms. Further, it helps distinguish NCS from psychogenic syncope.

Cerebral and tissue oximetry

The use of near-infrared spectroscopy (NIRS) has been increasingly adopted in cardiac surgery to measure regional cerebral oxygen saturation. This method takes advantage of the fact that light in the near-infrared spectrum penetrates tissue, including bone and muscle. Sensors are placed at fixed distances from a light emitter, and algorithms subtract superficial light absorption from deep absorption to provide an index of tissue oxygenation. Although the popularity of NIRS monitoring is growing, definitive data that prove outcome benefits with its use remain sparse. Therefore, widespread, routine use of NIRS as a standard-of-care monitor cannot be recommended at present. Recent investigations have focused on the use of NIRS in subgroups that may benefit from NIRS monitoring, such as pediatric patients. Furthermore, a novel application of processed NIRS information for monitoring cerebral autoregulation and tissue oxygenation (e.g., kidneys and the gut) is promising.

Wireless monitoring of liver hemodynamics in vivo

Liver transplants have their highest technical failure rate in the first two weeks following surgery. Currently, there are limited devices for continuous, real-time monitoring of the graft. In this work, a three wavelengths system is presented that combines near-infrared spectroscopy and photoplethysmography with a processing method that can uniquely measure and separate the venous and arterial oxygen contributions. This strategy allows for the quantification of tissue oxygen consumption used to study hepatic metabolic activity and to relate it to tissue stress. The sensor is battery operated and communicates wirelessly with a data acquisition computer which provides the possibility of implantation provided sufficient miniaturization. In two in vivo porcine studies, the sensor tracked perfusion changes in hepatic tissue during vascular occlusions with a root mean square error (RMSE) of 0.135 mL/min/g of tissue. We show the possibility of using the pulsatile wave to measure the arterial oxygen saturation similar to pulse oximetry. The signal is also used to extract the venous oxygen saturation from the direct current (DC) levels. Arterial and venous oxygen saturation changes were measured with an RMSE of 2.19% and 1.39% respectively when no vascular occlusions were induced. This error increased to 2.82% and 3.83% when vascular occlusions were induced during hypoxia. These errors are similar to the resolution of a commercial oximetry catheter used as a reference. This work is the first realization of a wireless optical sensor for continuous monitoring of hepatic hemodynamics.

The state of affairs of neurologic monitoring by near-infrared spectroscopy in pediatric cardiac critical care

PURPOSE OF REVIEW

The decreasing postoperative mortality in patients with congenital heart disease has enabled an increasing interest in preventing morbidity, especially from the central nervous system. Near-infrared spectroscopy, a noninvasive technology that provides an estimate of tissue oxygenation, has been introduced in the intensive care unit and has gained popularity over the last decade. This review aims to ascertain its ability to affect outcome.

RECENT FINDINGS

Recent studies have started to incorporate cerebral near-infrared spectroscopy in the assessment, evolution, and outcomes of surgical patients with congenital heart disease. These studies often represent small single-center high-risk cohorts that are evaluated in a retrospective or an observational manner. Nevertheless, new data are starting to indicate that near-infrared spectroscopy may be helpful not only in the assessment of critical care parameters, such as cardiac output performance or likelihood of adverse events, but, most notably, in the long-term neurological outcome.

SUMMARY

In addition to additional corroborative trials from different centers, a critical question that remains to be answered is whether targeting cerebral near-infrared spectroscopy values, as part of goal-directed therapy protocols, can help to improve outcome overall.

Fiberoptic monitoring of central venous oxygen saturation (PediaSat) in small children undergoing cardiac surgery: continuous is not continuous

Background: Monitoring of superior vena cava saturation (ScvO ₂) has become routine in the management of pediatric patients undergoing cardiac surgery. The objective of our study was to evaluate the correlation between continuous ScvO ₂ by the application of a fiber-optic oximetry catheter (PediaSat) and intermittent ScvO ₂ by using standard blood gas measurements. These results were compared to those obtained by cerebral near infrared spectroscopy (cNIRS).

Setting: Tertiary pediatric cardiac intensive care unit (PCICU).

Methods and main results: A retrospective study was conducted in consecutive patients who were monitored with a 4.5 or 5.5 F PediaSat catheter into the right internal jugular vein. An  in vivo calibration was performed once the patient was transferred to the PCICU and re-calibration took place every 24 hours thereafter. Each patient had a NIRS placed on the forehead. Saturations were collected every 4 hours until extubation. Ten patients with a median age of 2.2 (0.13-8.5) years and a weight of 12.4 (3.9-24) kg were enrolled. Median sampling time was 32 (19-44) hours: 64 pairs of PediaSat and ScVO2 saturations showed a poor correlation (r=0.62, 95% CI 44-75; p<0.0001) and Bland Altman analysis for repeated measures showed an average difference of 0.34 with a standard deviation of 7,9 and 95% limits of agreement from -15 to 16. Thirty-six pairs of cNIRS and ScVO2 saturations showed a fair correlation (r=0.79, 95% CI 0.60-0.89; p<0.0001) an average difference of -1.4 with a standard deviation of 6 and 95% limits of agreement from -13 to 10. Analysis of median percentage differences between PediaSat and ScvO2 saturation over time revealed that, although not statistically significant, the change in percentage saturation differences was clinically relevant after the 8th hour from calibration (from -100 to +100%).

Conclusion: PediaSat catheters showed unreliable performance in our cohort. It should be further investigated whether repeating calibrations every 8 hours may improve the accuracy of this system. CNIRS may provide similar results with a lower invasiveness.

Temporary atrial pacing for cardiac output after pediatric cardiac surgery

Pediatric cardiothoracic surgery is often associated with low cardiac output in the postoperative period. This study sought to determine whether increasing heart rate via temporary atrial pacing is beneficial in augmenting cardiac output. Patients younger than 18 years who underwent cardiothoracic surgery and had no perioperative arrhythmias were eligible for the study. Patients not paced postoperatively were atrial paced at a rate of 15 % above the intrinsic sinus rate (not to exceed 170 beats per minute, less for older patients) for 15 min. Patients paced for cardiac output postoperatively had their pacemakers paused for 15 min. Markers of cardiac output were measured before and after the intervention. Of the 60 patients who consented to participate, 30 completed the study. Failure to complete the study was due to tachycardia (n = 13), lack of pacing wires (n = 7), junctional rhythm (n = 4), advanced atrioventricular block (n = 3), and other cause (n = 3). Three patients were paced at baseline. There was no change in arteriovenous oxygen saturation difference, mean arterial blood pressure, central venous pressure, toe temperature, or lactate with atrial pacing. Atrial pacing was associated with a decrease in head and flank near-infrared spectroscopy (p = 0.01 and <0.01 respectively). Secondary analysis found an inverse relationship between mean arterial pressure response to pacing and bypass time. Temporary atrial pacing does not improve cardiac output after pediatric cardiac surgery and may be deleterious. Future research may identify subsets of patients who benefit from this strategy. Practitioners considering this strategy should carefully evaluate each patient's response to atrial pacing before its implementation.