Cerebral oxygenation measured by near-infrared spectroscopy: comparison with jugular bulb oximetry

Invasive Neuromonitoring Modalities in the Pediatric Population

Invasive neuromonitoring has become an important part of pediatric neurocritical care, as neuromonitoring devices provide objective data that can guide patient management in real time. New modalities continue to emerge, allowing clinicians to integrate data that reflect different aspects of cerebral function to optimize patient management. Currently, available common invasive neuromonitoring devices that have been studied in the pediatric population include the intracranial pressure monitor, brain tissue oxygenation monitor, jugular venous oximetry, cerebral microdialysis, and thermal diffusion flowmetry. In this review, we describe these neuromonitoring technologies, including their mechanisms of function, indications for use, advantages and disadvantages, and efficacy, in pediatric neurocritical care settings with respect to patient outcomes.

Hemodynamic assessment in children after cardiac surgery: A pilot study on the value of infrared thermography

Introduction

Low cardiac output syndrome in the postoperative period after cardiac surgery leads to an increase in tissue oxygen extraction, assessed by the oxygen extraction ratio. Measurement of the oxygen extraction ratio requires blood gases to be taken. However, the temperature of the skin and various parts of the body is a direct result of blood flow distribution and can be monitored using infrared thermography. Thus, we conducted a prospective clinical study to evaluate the correlation between the thermal gradient obtained by infrared thermography and the oxygen extraction ratio in children at risk for low cardiac output after cardiac surgery.

Methods

Children aged 0 to 18 years, having undergone cardiac surgery with cardio-pulmonary bypass in a pediatric intensive care unit were included in the study. One to 4 thermal photos were taken per patient using the FLIR One Pro thermal imaging camera. The thermal gradient between the central temperature of the inner canthus of the eye and the peripheral temperature was compared to the concomitant oxygen extraction ratio calculated from blood gases.

Results

41 patients were included with a median age of 6 months (IQR 3-48) with median Risk Adjustment for Congenital Heart Surgery-1 score was 2 (IQR 2-3). Eighty nine thermal photos were analyzed. The median thermal gradient was 2.5 °C (IQR 1,01-4.04). The median oxygen extraction ratio was 35% (IQR 26-42). Nine patients had an oxygen extraction ratio ≥ 50%. A significant but weak correlation was found between the thermal gradient and the oxygen extraction ratio (Spearman's test p = 0.25, p = 0.016). Thermal gradient was not correlated with any other clinical or biologic markers of low cardiac output. Only young age was an independent factor associated with an increase in the thermal gradient.

Conclusion

In this pilot study, which included mainly children without severe cardiac output decrease, a significant but weak correlation between thermal gradient by infrared thermography and oxygen extraction ratio after pediatric cardiac surgery was observed. Infrared thermography is a promising non-invasive technology that could be included in multimodal monitoring of postoperative cardiac surgery patients. However, a clinical trial including more severe children is needed.

Comparative Assessment of Propofol and Ketamine on Hemodynamic Indices and Cerebral Oximetry of Pediatric Patients Undergoing Cardiac Catheterization

Background

Propofol and ketamine are widely used in the induction and maintenance of anesthesia and sedation with different cardiovascular and respiratory effects. In cardiac anesthesia (including pediatric cardiac catheterization), due to the high risk of neurologic complications, cerebral oximetry can effectively monitor cerebral blood oxygen saturation to prevent neurological and respiratory complications.

Objectives

This study aimed to compare the effect of propofol and ketamine on hemodynamic indices and cerebral oxygenation results in children undergoing cardiac catheterization.

Methods

This clinical trial study was performed on 48 patients who were candidates for cardiac catheterization by easy and continuous sampling. Patients were randomly divided into 2 groups: ketamine and propofol. In the ketamine group, ketamine was injected at a dose of 1 - 2 mg/kg, and in the propofol group, propofol was injected at a dose of 0.5 - 1.5 mg/kg. In both groups, incremental doses were repeated as needed. The hemodynamic indices, including blood pressure, heart rate, and peripheral SpO₂, were recorded. Cerebral regional oxygen saturation (RSO₂) was recorded using infrared spectroscopic sensors. Data were analyzed using chi-square, independent t-test, paired t-test, and 1-way analysis of variance (ANOVA).

Results

The results showed that all demographic characteristics of patients and also the mean duration of catheterization were homogeneous between the 2 groups. Hemodynamic indices (such as systolic, diastolic, and mean arterial blood pressure) did not show a significant difference between the 2 groups; however, in the ketamine group compared to the propofol group, the heart rate was significantly higher, and mean RSO₂ was lower (P = 0.023).

Conclusions

Propofol has fewer complications than ketamine and is a good drug for sedating children undergoing cardiac catheterization.

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.

Anesthetic Considerations in Pediatric Patients With Acute Decompensated Heart Failure

Acute decompensated heart failure (ADHF) in pediatrics is a significant cause for morbidity and mortality in children. Congenital heart disease and cardiomyopathy are the leading etiologies of ADHF. It is common for these children to undergo diagnostic, therapeutic, or surgical procedure under anesthesia, which may be associated with significant morbidity and mortality. The importance of preanesthetic multidisciplinary planning with all involved teams, including anesthesia, cardiology, intensive care, perfusion, and cardiac surgery, cannot be emphasized enough. In order to safely manage these patients, it is imperative for the anesthesiologist to understand the complex pathophysiological interactions between cardiopulmonary systems and anesthesia during these procedures. This review discusses the etiology, pathophysiology, clinical manifestations, and perioperative management of these patients.

Integrative physiological assessment of cerebral hemodynamics and metabolism in acute ischemic stroke

Restoring perfusion to ischemic tissue is the primary goal of acute ischemic stroke care, yet only a small portion of patients receive reperfusion treatment. Since blood pressure (BP) is an important determinant of cerebral perfusion, effective BP management could facilitate reperfusion. But how BP should be managed in very early phase of ischemic stroke remains a contentious issue, due to the lack of clear evidence. Given the complex relationship between BP and cerebral blood flow (CBF)-termed cerebral autoregulation (CA)-bedside monitoring of cerebral perfusion and oxygenation could help guide BP management, thereby improve stroke patient outcome. The aim of INFOMATAS is to 'identify novel therapeutic targets for treatment and management in acute ischemic stroke'. In this review, we identify novel physiological parameters which could be used to guide BP management in acute stroke, and explore methodologies for monitoring them at the bedside. We outline the challenges in translating these potential prognostic markers into clinical use.

Correlation of Near-Infrared Spectroscopy Oximetry and Corresponding Venous Oxygen Saturations in Children with Congenital Heart Disease

Invasive and non-invasive monitoring allow for early detection of hemodynamic compromise, facilitating timely intervention and avoidance of further decline. While venous oximetry is useful for assessing the adequacy of systemic oxygen delivery (DO₂), it is most often intermittent, invasive, and costly. Near-infrared spectroscopy (NIRS) oximetry allows for the non-invasive estimation of the adequacy of DO₂. We assessed the correlation between cerebral NIRS oximetry and superior vena cava (SVC) and jugular venous (JV) oxygen saturations and between renal NIRS oximetry and inferior vena cava (IVC) oxygen saturations. Systematic review of the literature was conducted to identify studies with data regarding near-infrared spectroscopy and venous saturation. The PubMed, EMBASE, Medline, and Cochrane databases were queried using the following terms in isolation and various combinations: "congenital heart disease," "near infrared spectroscopy," "venous saturation," and "pediatric." Pediatric studies in which simultaneous NIRS oximetry and corresponding venous oxygen saturations were simultaneously collected after cardiac surgery or catheterization were identified. Data were pooled from these studies to analyze the correlation between NIRS oximetry and the corresponding venous oxygen saturations. A total of 16 studies with 613 patients were included in the final analyses. Data were present to compare cerebral and renal NIRS oximetry with corresponding venous oxygen saturation. Cerebral NIRS and SVC and JV oxygen saturations and renal NIRS and IVC oxygen saturations demonstrated strong degrees of correlation (r-value 0.70 for each). However, cerebral NIRS and IVC oxygen saturation had a week degree of correlation (r-value of 0.38). Pooled analyses demonstrate that cerebral NIRS oximetry correlates strongly with SVC or JV oxygen saturation while renal NIRS oximetry correlates strongly with IVC oxygen saturations. A weak correlation was noted between cerebral NIRS oximetry and IVC oxygen saturations.

Cerebral hemoglobin oxygenation in children with congenital heart disease

BACKGROUND

It is important to identify the pathological characteristics of cerebral circulation and oxygen metabolism at the bedside in children with congenital heart disease (CHD) to prevent neurodevelopmental impairments. The brain regional oxygen saturation index (rSO₂ ) can be easily obtained at the bedside with near-infrared spectroscopy and has been widely used in the management of children with CHD in recent years.

METHODS

To determine if the rSO₂ before or after CHD surgery is a good predictor of cerebral oxygen metabolism, we investigated the impact of different clinical variables on the correlation between rSO₂ and reference values under steady ratios of hemoglobin oxygen saturation in the internal jugular vein (SjvO₂ ) or femoral artery (SaO₂ ) (0.75:0.25, 0.66:0.34, and 0.50:0.50) in 186 children with CHD undergoing cardiac catheterization.

RESULTS

In three patient groups-double ventricles before surgery, double ventricles after surgery, and single ventricle before surgery-there were significant relationships between rSO₂ and the reference values of SO₂ under all three steady ratios of SjvO₂ and SaO₂ . No relationship with the reference values was found for the single ventricle after surgery group.

CONCLUSIONS

Regional oxygen saturation index is useful for assessing cerebral oxygenation in children with CHD, but knowledge of the underlying cardiac pathology in CHD, especially in the case of a single ventricle after surgery, is important for the correct interpretation of rSO₂ measurements obtained using near-infrared spectroscopy.

Neuromonitoring and Neurocognitive Outcomes in Cardiac Surgery: A Narrative Review

Neurocognitive dysfunction after cardiac surgery can present with diverse clinical phenotypes, which include postoperative delirium, postoperative cognitive dysfunction, and stroke, and it presents a significant healthcare burden for both patients and providers. Neurologic monitoring during cardiac surgery includes several modalities assessing cerebral perfusion and oxygenation (near-infrared spectroscopy, transcranial Doppler and jugular venous bulb saturation monitoring) and those that measure cerebral function (processed and unprocessed electroencephalogram), reflecting an absence of a single, definitive neuromonitor. This narrative review briefly describes the technologic basis of these neuromonitoring modalities, before exploring their use in clinical practice, both as tools to predict neurocognitive dysfunction, and with a bundle of interventions designed to optimize cerebral oxygen supply, with the aim of reducing postoperative delirium and cognitive dysfunction following cardiac surgery.

Higher preoperative Qp/Qs ratio is associated with lower preoperative regional cerebral oxygen saturation in children with ventricular septal defect

PURPOSE

The relationship between regional cerebral oxygen saturation (rSO₂) and the amount of left-to-right shunt in ventricular septal defect (VSD) patients has not yet been investigated. The purpose of this study was to identify the association of preoperative pulmonary to systemic blood flow (Qp/Qs) ratio and preoperative rSO₂ in patients with VSD.

METHODS

We retrospectively evaluated 49 VSD surgical closure candidates at a single institution. Preoperative Qp/Qs ratio was compared with rSO₂ measurements at the time of VSD closure surgery.

RESULTS

Forty-nine were eligible for the final analysis. The median age at surgery was 6 (interquartile range [IQR]: 3, 12) months, and 36.7% were male. Atrial septal defects coexisted in 51.0%. There were no genetic abnormalities except trisomy 21 in 32.6% of the patients. Pulmonary hypertension was found in 42.8%. The median Qp/Qs ratio, calculated based on catheter testing results before the surgery, was 2.7 (IQR: 2.1, 3.7). Postoperative rSO₂ was significantly higher than preoperative values (52.2 ± 12.9, 63.5 ± 13.1%, p < 0.001). There was an inverse relationship of Qp/Qs and preoperative cerebral rSO₂ (r = - 0.11, p = 0.02).

CONCLUSION

A higher Qp/Qs ratio was associated with a lower preoperative cerebral rSO₂ in pediatric patients with VSD.

Cerebral regional oxygen saturation during cardiopulmonary resuscitation and return of spontaneous circulation: A systematic review and meta-analysis

AIM

Predicting the return of spontaneous circulation (ROSC) during cardiopulmonary resuscitation in victims of cardiac arrest (CA) remains challenging. Cerebral regional oxygen saturation (rSO2) measured during resuscitation is feasible, and higher initial and overall values seem associated with ROSC. However, these observations were limited to the analysis of few small single-centre studies. There is a growing number of studies evaluating the role of cerebral rSO2 in the prediction of ROSC.

METHODS

We conducted an updated meta-analysis aimed at investigating the association of initial and overall values of cerebral rSO2 with ROSC after CA. We performed subgroups analyses according to the location of CA and conducted a secondary analysis according to the country where the study was conducted (resuscitation practice varies greatly for out-of-hospital CA).

RESULTS

We included 17 studies. Higher initial rSO2 values (11 studies, n = 2870, 16.6% achieved ROSC) were associated with ROSC: Mean Difference (MD) -11.54 [95%Confidence Interval (CI)-20.96, -2.12]; p = 0.02 (I2 = 97%). The secondary analysis confirmed this finding when pooling together European and USA studies, but did not for Japanese studies (p = 0.06). One multi-centre Japanese study was an outlier with large influence on 95%CI. Higher overall rSO2 values during resuscitation (9 studies, n = 894, 33.7% achieving ROSC) were associated with ROSC: MD-10.38; [-13.73, -7.03]; p < 0.00001 (I2 = 77%). All studies were conducted in Europe/USA.

CONCLUSIONS

This updated meta-analysis confirmed the association between higher initial and overall values of cerebral rSO2 and ROSC after CA. However, we found geographical differences, since this association was not present when Japanese studies were analysed separately.

The Association of Cerebral Desaturation During One-Lung Ventilation and Postoperative Recovery: A Prospective Observational Cohort Study

OBJECTIVES

This study was designed to investigate whether cerebral oxygen desaturations during thoracic surgery are predictive of patients' quality of recovery. As a secondary aim, the authors investigated the relationship among cerebral desaturations and postoperative delirium and hospital length of stay.

DESIGN

This study was a prospective observational cohort study.

SETTING

A single tertiary-care medical center from September 2012 through March 2014.

PATIENTS

Adult patients scheduled for elective pulmonary surgery requiring one-lung ventilation.

INTERVENTIONS

All patients were monitored with the ForeSight cerebral oximeter.

MEASUREMENTS AND MAIN RESULTS

The primary assessment tool was the Postoperative Quality of Recovery Scale. Delirium was assessed using the Confusion Assessment Method. Of the 117 patients analyzed in the study, 60 of the patients desaturated below a cerebral oximetry level of 65% for a minimum of 3 minutes (51.3%). Patients who desaturated were significantly less likely to have cognitive recovery in the immediate postoperative period (p = 0.012), which did not persist in the postoperative period beyond day 0. Patients who desaturated also were more likely to have delirium (p = 0.048, odds ratio 2.81 [95% CI 1.01-7.79]) and longer length of stay (relative duration 1.35, 95% CI 1.05-1.73; p = 0.020).

CONCLUSIONS

Intraoperative cerebral oxygen desaturations, frequent during one-lung ventilation, are associated significantly with worse early cognitive recovery, high risk of postoperative delirium, and prolonged length of stay. Large interventional studies on cerebral oximetry in the thoracic operating room are warranted.

Clinical and Technical Limitations of Cerebral and Somatic Near-Infrared Spectroscopy as an Oxygenation Monitor

Cerebral and somatic near-infrared spectroscopy monitors are commonly used to detect tissue oxygenation in various circumstances. This form of monitoring is based on tissue infrared absorption and can be influenced by several physiological and non-physiological factors that can induce error in the interpretation. This narrative review explores those clinical and technical limitations and proposes solutions and alternatives in order to avoid some of those pitfalls.

Non-invasive optical neuromonitoring of the temperature-dependence of cerebral oxygen metabolism during deep hypothermic cardiopulmonary bypass in neonatal swine

Management of deep hypothermic (DH) cardiopulmonary bypass (CPB), a critical neuroprotective strategy, currently relies on non-invasive temperature to guide cerebral metabolic suppression during complex cardiac surgery in neonates. Considerable inter-subject variability in temperature response and residual metabolism may contribute to the persisting risk for postoperative neurological injury. To characterize and mitigate this variability, we assess the sufficiency of conventional nasopharyngeal temperature (NPT) guidance, and in the process, validate combined non-invasive frequency-domain diffuse optical spectroscopy (FD-DOS) and diffuse correlation spectroscopy (DCS) for direct measurement of cerebral metabolic rate of oxygen (CMRO₂). During CPB, n = 8 neonatal swine underwent cooling from normothermia to 18℃, sustained DH perfusion for 40 min, and then rewarming to simulate cardiac surgery. Continuous non-invasive and invasive measurements of intracranial temperature (ICT) and CMRO₂ were acquired. Significant hysteresis (p < 0.001) between cooling and rewarming periods in the NPT versus ICT and NPT versus CMRO₂ relationships were found. Resolution of this hysteresis in the ICT versus CMRO₂ relationship identified a crucial insufficiency of conventional NPT guidance. Non-invasive CMRO₂ temperature coefficients with respect to NPT (Q₁₀ = 2.0) and ICT (Q₁₀ = 2.5) are consistent with previous reports and provide further validation of FD-DOS/DCS CMRO₂ monitoring during DH CPB to optimize management.

Near-Infrared Spectroscopy in Pediatric Congenital Heart Disease

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

Cerebral NIRS patterns in late preterm and very preterm infants becoming late preterm

BACKGROUND

Near Infrared Spectroscopy (NIRS) has been proposed as a useful, noninvasive monitoring technique providing reliable information about central nervous system (CNS) oximetry and function. Recently, brain damage has been reconsidered as a dynamic process evolving over the weeks of gestation. We therefore investigated NIRS cerebral pattern differences between healthy late preterm infants (LPTo) and very preterm infants becoming late preterm (LPT).

METHODS

We conducted an observational study in 40 healthy late preterm infants, matched for gestational age at monitoring, of whom 20 where LPTo and 20 LPT. Clinical, diagnostic and laboratory monitoring procedures and cerebral oximetry (crSO2) and function (cFTOE) were recorded on admission into the study.

RESULTS

No significant differences (p > .05, for all) were found between groups regarding clinical, diagnostic or laboratory parameters. Higher crSO2 and lower cFTOE (p < .001, for both) were found in the LPTo group.

CONCLUSIONS

Our results, showing impaired oximetry and function of CNS in LPT, offer additional support to NIRS parameters as a useful tool for longitudinal CNS monitoring of very preterm infants becoming LPT. Future studies correlating NIRS variables and long-term neurological outcome in LPT are needed to elucidate the concept of dynamic brain damage pathogenesis.

In vivo validation of cerebral near-infrared spectroscopy: a review

We summarize the available in vivo validation of cerebral near-infrared spectroscopy (NIRS) oximetry to inform future in vivo validation strategies. In particular, to establish a way forward in the assessment of NIRS instrumentation for future randomized trials, a systematic literature search is performed. The records are screened and abstracts are assessed to select studies fulfilling our inclusion criteria. Twenty-two pediatric and 28 adult studies are analyzed after exclusion of three articles in each group. All studies compare regional cerebral tissue oxygenation measured by cerebral NIRS to invasive measurement of central or jugular venous oxygen saturation. In studies without Bland-Altman plots, we extracted data from scatter plots enabling estimation of mean difference (MD), standard deviation (SD), and limits of agreement (LOA). To assess the agreement between rStO 2 (regional cerebral tissue oxygenation) estimated by NIRS and by blood samples, weighted averages of the MDs and SDs from each study are calculated. We found a fair agreement between the overall mean of cerebral tissue oxygenation and the mean of a reference value measured by co-oximetry whatever NIRS instrument or site of blood sampling used. Cerebral oxygenation overestimates the reference at low values, some instruments apparently more than others. Thus, a high degree of scatter and a lack of a good reference method complicate in vivo validation of NIRS. It is difficult to draw any firm conclusions despite the large number of studies, and the result of this review leaves us questioning if more of such validation studies of cerebral NIRS oximetry are really needed. Furthermore, the combination of lack of validation and poor repeatability is an important issue when designing a randomized clinical trial of implementing cerebral NIRS oximetry into clinical care.

Changes in Near-Infrared Spectroscopy After Congenital Cyanotic Heart Surgery

BACKGROUND

Since oxygen saturation from pulse oximetry (SpO₂) and partial pressure of arterial oxygen (PaO₂) are observed to improve immediately after surgical correction of cyanotic congenital heart disease (CHD), we postulate that cerebral (CrO₂) and somatic (SrO₂) oximetry also improves immediately post-correction. We aim to prospectively examine CrO₂ and SrO₂, before, during, and after surgical correction as well as on hospital discharge in children with cyanotic CHD to determine if and when these variables increase.

METHODS

This is a prospective observational trial. Eligibility criteria included children below 18 years of age with cyanotic CHD who required any cardiac surgical procedure. CrO₂ and SrO₂ measurements were summarized at six time-points for comparison: (1) pre-cardiopulmonary bypass (CPB); (2) during CPB; (3) post-CPB; (4) Day 1 in the pediatric intensive care unit (PICU); (5) Day 2 PICU; and (6) discharge. Categorical and continuous variables are presented as counts (percentages) and median (interquartile range), respectively.

RESULTS

Twenty-one patients were analyzed. 15 (71.4%) and 6 (28.6%) patients underwent corrective and palliative surgeries, respectively. In the corrective surgery group, SpO₂ increased immediately post-CPB compared to pre-CPB [99 (98, 100) vs. 86% (79, 90); p < 0.001] and remained in the normal range through to hospital discharge. Post-CPB CrO₂ did not change from pre-CPB [72.8 (58.8, 79.0) vs. 72.1% (63.0, 78.3); p = 0.761] and even decreased on hospital discharge [60.5 (53.6, 62.9) vs. 72.1% (63.0, 78.3); p = 0.005]. Post-CPB SrO₂ increased compared to pre-CPB [87.3 (77.2, 89.5) vs. 72.7% (65.6, 77.3); p = 0.001] but progressively decreased during PICU stay to a value lower than baseline at hospital discharge [66.9 (57.3, 76.9) vs. 72.7% (65.6, 77.3); p = 0.048].

CONCLUSION

CrO₂ and SrO₂ did not increase after corrective surgery of cyanotic CHD even up to hospital discharge. Future larger studies are required to validate these findings. (This study is registered with ClinicalTrials.gov ID: NCT02417259.).

Cerebral Oxygen Saturation in Children With Congenital Heart Disease and Chronic Hypoxemia

BACKGROUND

Increased hemoglobin (Hb) concentration accompanying hypoxemia is a compensatory response to maintain tissue oxygen delivery. Near infrared spectroscopy (NIRS) is used clinically to detect abnormalities in the balance of cerebral tissue oxygen delivery and consumption, including in children with congenital heart disease (CHD). Although NIRS-measured cerebral tissue O2 saturation (ScO2) correlates with arterial oxygen saturation (SaO2), jugular bulb O2 saturation (SjbO2), and Hb, little data exist on the interplay between these factors and cerebral O2 extraction (COE). This study investigated the associations of ScO2 and ΔSaO2-ScO2 with SaO2 and Hb and verified the normal range of ScO2 in children with CHD.

METHODS

Children undergoing cardiac catheterization for CHD were enrolled in a calibration and validation study of the FORE-SIGHT NIRS monitor. Two pairs of simultaneous arterial and jugular bulb samples were drawn for co-oximetry, calculation of a reference ScO2 (REF CX), and estimation of COE. Pearson correlation and linear regression were used to determine relationships between O2 saturation parameters and Hb. Data were also analyzed according to diagnostic group defined as acyanotic (SaO2 ≥ 90%) and cyanotic (SaO2 < 90%).

RESULTS

Of 65 children studied, acceptable jugular bulb samples (SjbO2 absolute difference between samples ≤10%) were obtained in 57 (88%). The ΔSaO2-SjbO2, ΔSaO2-ScO2, and ΔSaO2-REF CX were positively correlated with SaO2 and negatively correlated with Hb (all P < .001). Although by diagnostic group ScO2 differed statistically (P = .002), values in the cyanotic patients were within the range considered normal (69% ± 6%). COE estimated by the difference between arterial and jugular bulb O2 content (ΔCaO2-CjbO2, mL O2/100 mL) was not different for cyanotic and acyanotic patients (P = .10), but estimates using ΔSaO2-SjbO2, ΔSaO2-ScO2, or ΔSaO2-ScO2/SaO2 were significantly different between the cyanotic and acyanotic children (P < .001).

CONCLUSIONS

Children with adequately compensated chronic hypoxemia appear to have ScO2 values within the normal range. The ΔSaO2-ScO2 is inversely related to Hb, with the implication that in the presence of reduced Hb, particularly if coupled with a decreased cardiac output, the ScO2 can fall to values associated with brain injury in laboratory studies.

Cerebral Oximetry for Cardiac and Vascular Surgery

The technology of transcranial near-infrared spectroscopy (NIRS) for the measurement of cerebral oxygen balance was introduced 25 years ago. Until very recently, there has been only occasional interest in its use during surgical monitoring. Now, however, substantial technologic advances and numerous clinical studies have, at least partly, succeeded in overcoming long-standing and widespread misunderstanding and skepticism regarding its value. Our goals are to clarify common misconceptions about near-infrared spectroscopy and acquaint the reader with the substantial literature that now supports cerebral oximetric monitoring in cardiac and major vascular surgery.

Perfusion indices revisited

Monitoring of tissue perfusion is an essential step in the management of acute circulatory failure. The presence of cellular dysfunction has been a basic component of shock definition even in the absence of hypotension. Monitoring of tissue perfusion includes biomarkers of global tissue perfusion and measures for assessment of perfusion in non-vital organs. The presence of poor tissue perfusion in a shocked patient is usually associated with worse outcome. Persistently impaired perfusion despite adequate resuscitation is also associated with worse outcome. Thus, normalization of some perfusion indices has become one of the resuscitation targets in patients with septic shock. Although the collective evidence shows the clear relation between impaired peripheral perfusion and mortality, the use of different perfusion indices as a resuscitation target needs more research.

Non-invasive Assessment of Cerebral Blood Flow and Oxygen Metabolism in Neonates during Hypothermic Cardiopulmonary Bypass: Feasibility and Clinical Implications

The neonatal brain is extremely vulnerable to injury during periods of hypoxia and/or ischemia. Risk of brain injury is increased during neonatal cardiac surgery, where pre-existing hemodynamic instability and metabolic abnormalities are combined with long periods of low cerebral blood flow and/or circulatory arrest. Our understanding of events associated with cerebral hypoxia-ischemia during cardiopulmonary bypass (CPB) remains limited, largely due to inadequate tools to quantify cerebral oxygen delivery and consumption non-invasively and in real-time. This pilot study aims to evaluate cerebral blood flow (CBF) and oxygen metabolism (CMRO₂) intraoperatively in neonates by combining two novel non-invasive optical techniques: frequency-domain near-infrared spectroscopy (FD-NIRS) and diffuse correlation spectroscopy (DCS). CBF and CMRO₂ were quantified before, during and after deep hypothermic cardiopulmonary bypass (CPB) in nine neonates. Our results show significantly decreased CBF and CMRO₂ during hypothermic CPB. More interestingly, a change of coupling between both variables is observed during deep hypothermic CPB in all subjects. Our results are consistent with previous studies using invasive techniques, supporting the concept of FD-NIRS/DCS as a promising technology to monitor cerebral physiology in neonates providing the potential for individual optimization of surgical management.

Brain oxygen saturation assessment in neonates using T2-prepared blood imaging of oxygen saturation and near-infrared spectroscopy

Although near-infrared spectroscopy is increasingly being used to monitor cerebral oxygenation in neonates, it has a limited penetration depth. The T₂-prepared Blood Imaging of Oxygen Saturation (T₂-BIOS) magnetic resonance sequence provides an oxygen saturation estimate on a voxel-by-voxel basis, without needing a respiratory calibration experiment. In 15 neonates, oxygen saturation measured by T₂-prepared blood imaging of oxygen saturation and near-infrared spectroscopy were compared. In addition, these measures were compared to cerebral blood flow and venous oxygen saturation in the sagittal sinus. A strong linear relation was found between the oxygen saturation measured by magnetic resonance imaging and the oxygen saturation measured by near-infrared spectroscopy ( R²= 0.64, p < 0.001). Strong linear correlations were found between near-infrared spectroscopy oxygen saturation, and magnetic resonance imaging measures of frontal cerebral blood flow, whole brain cerebral blood flow and venous oxygen saturation in the sagittal sinus ( R²= 0.71, 0.50, 0.65; p < 0.01). The oxygen saturation obtained by T₂-prepared blood imaging of oxygen saturation correlated with venous oxygen saturation in the sagittal sinus ( R²= 0.49, p = 0.023), but no significant correlations could be demonstrated with frontal and whole brain cerebral blood flow. These results suggest that measuring oxygen saturation by T₂-prepared blood imaging of oxygen saturation is feasible, even in neonates. Strong correlations between the various methods work as a cross validation for near-infrared spectroscopy and T₂-prepared blood imaging of oxygen saturation, confirming the validity of using of these techniques for determining cerebral oxygenation.

Monitoring Cerebral Oxygenation in Neonates: An Update

Cerebral oxygenation is not always reflected by systemic arterial oxygenation. Therefore, regional cerebral oxygen saturation (rScO₂) monitoring with near-infrared spectroscopy (NIRS) is of added value in neonatal intensive care. rScO₂ represents oxygen supply to the brain, while cerebral fractional tissue oxygen extraction, which is the ratio between rScO₂ and systemic arterial oxygen saturation, reflects cerebral oxygen utilization. The balance between oxygen supply and utilization provides insight in neonatal cerebral (patho-)physiology. This review highlights the potential and limitations of cerebral oxygenation monitoring with NIRS in the neonatal intensive care unit.

Chronic Thromboembolic Pulmonary Hypertension and Pulmonary Thromboendarterectomy

Chronic thromboembolic pulmonary hypertension results from incomplete resolution of a pulmonary embolus or from recurrent pulmonary emboli. Its incidence is underappreciated, and it is currently an undertreated phenomenon. Pulmonary thromboendarterectomy is currently the safest and most effective treatment for this condition. The surgery involves midline sternotomy, profound hypothermic circulatory arrest, and complete endarterectomy of the pulmonary vascular tree. Success depends on effective coordination of multiple medical teams, including pulmonary medicine, anesthesiology, and surgery. This review, based on the past 30 years of experience at University of California San Diego Medical Center, includes information about the clinical history, diagnostic workup, anesthesia, surgical approach, and postoperative care. Outcome data are discussed, as are avenues for future research.

Hemodynamic Monitoring

OBJECTIVES

In this review, we discuss hemodynamic monitoring modalities, including their application, the interpretation of data, limitations, and impact on outcomes.

DATA SOURCE

MEDLINE, PubMed.

CONCLUSIONS

One of the tenets of critical care medicine is to ensure adequate tissue oxygenation. This assessment must be timely and accurate to optimize outcomes. The clinical assessment of cardiac function, cardiac output, and tissue oxygenation based on the physical examination and standard hemodynamic variables, although an indispensable part of this exercise, has significant limitations. The use of adjunctive hemodynamic monitoring modalities provides a much more objective, accurate, and timely assessment of the patient's hemodynamic profile and is invaluable for assessing the patient's clinical status, clinical trajectory, and response to interventions.

Effect of controlled hypotension on regional cerebral oxygen saturation during rhinoplasty: a prospective study

The aim of this study was to investigate the effect of controlled hypotension on cerebral oxygen saturation (rSO2) using near infrared spectroscopy (NIRS) and evaluation of postoperative cognitive function in patients undergoing rhinoplasty. Fifty adult patients who were scheduled for elective rhinoplasty surgery and required controlled hypotension were enrolled in this prospective study. Controlled hypotension was provided using a combination of propofol and remifentanil infusion supplemented with nitroglycerin infusion as necessary. rSO2 was evaluated during controlled hypotension by NIRS. Cerebral desaturation was observed in 5 out of 50 patients (10 %) during hypotensive anesthesia. The greatest decrease from baseline was 28 % when MAP was 57 mmHg. In both non-desaturated and desaturated patients, postoperative MMSE scores were significantly lower than preoperative scores. There was a 4 % decrease in the non-desaturated patients and a 7 % decrease in the desaturated patients when preoperative and postoperative MMSE scores were compared. A decline in cognitive function 1 day after surgery was observed in 23 patients (46 %) and in all patients with intraoperative cerebral desaturation. The current study showed that even if SpO2 is in the normal range, there might be a decrease of more than 20 % in cerebral oxygen saturation during controlled hypotension.

Near-Infrared Spectroscopy in the Monitoring of Adult Traumatic Brain Injury: A Review

Cerebral near-infrared spectroscopy (NIRS) has long represented an exciting prospect for the noninvasive monitoring of cerebral tissue oxygenation and perfusion in the context of traumatic brain injury (TBI), although uncertainty still exists regarding the reliability of this technology specifically within this field. We have undertaken a review of the existing literature relating to the application of NIRS within TBI. We discuss current "state-of-the-art" NIRS monitoring, provide a brief background of the technology, and discuss the evidence regarding the ability of NIRS to substitute for established invasive monitoring in TBI.

Sevoflurane anesthesia and brain perfusion

OBJECTIVE/AIM

To assess the impact of sevoflurane and anesthesia-induced hypotension on brain perfusion in children younger than 6 months.

BACKGROUND

Safe lower limit of blood pressure during anesthesia in infant is unclear, and inadequate anesthesia can lead to hypotension, hypocapnia, and low cerebral perfusion. Insufficient cerebral perfusion in infant during anesthesia is an important factor of neurological morbidity. In two previous studies, we assessed the impact of sevoflurane anesthesia on cerebral blood flow (CBF) by transcranial Doppler (TCD) and on brain oxygenation by NIRS, in children ≤2 years. As knowledge about consequences of anesthesia-induced hypotension on cerebral perfusion in children ≤6 months is scarce, we conducted a retrospective analysis to compare the data of CBF and brain oxygenation, in this specific population.

METHODS

We performed a retrospective analysis of data collected from our two previous studies. Baseline values of TCD or NIRS were recorded and then during sevoflurane anesthesia. From a database of 338 patients, we excluded all patients older than 6 months. Then, we compared physiological variables of TCD and NIRS population to ensure that the two groups were comparable. We compared rSO2 c and TCD measurements variation according to MAP value during sevoflurane anesthesia, using anova and Student-Newman-Keuls for posthoc analysis.

RESULTS

One hundred and eighty patients were included in the analysis. TCD and NIRS groups were comparable. CBF velocities (CBFV) or rSO2 c reflects a good cerebral perfusion when MAP is above 45 mmHg. When MAP is between 35 and 45 mmHg, CBFV variation reflects a reduction of CBF, but rSO2 c increase is the consequence of a still positive balance between CMRO2 and O2 supply. Below 35 mmHg of MAP during anesthesia, CBFV decrease and rSO2 c variation from baseline is low. For each category of MAP and for the two groups, etCo2 and expired fraction of sevoflurane (FeSevo) were comparable (anova P > 0.05).

CONCLUSION

In a healthy infant without dehydration, with normal PaCO2 and hemoglobin value, scheduled for short procedures, MAP is a good proxy of cerebral perfusion as we found that CBF assessed by CBFV and rSO2 c decreased proportionally with cerebral perfusion pressure. During 1 MAC sevoflurane anesthesia, maintaining MAP beyond 35 mmHg during anesthesia is probably safe and sufficient. But when MAP decreases below 35 mmHg, CBF decreases and rSO2 c variation from baseline is low despite CMRO2 reduction. In this situation, cerebral metabolic reserve is low and further changes of systemic conditions may be poorly tolerated by the brain.

Noninvasive regional cerebral oxygen saturation for neurological prognostication of patients with out-of-hospital cardiac arrest: a prospective multicenter observational study

AIM

To investigate the association between regional brain oxygen saturation (rSO2) at hospital arrival and neurological outcomes at 90 days in patients with out-of-hospital cardiac arrest (OHCA).

METHODS

The Japan-Prediction of neurological Outcomes in patients post cardiac arrest (J-POP) registry is a prospective, multicenter, cohort study to test whether rSO2 predicts neurological outcomes after OHCA. We measured rSO2 in OHCA patients immediately after hospital arrival using a near-infrared spectrometer placed on the forehead with non-blinded fashion. The primary endpoint was "neurological outcomes" at 90 days after OHCA.

RESULTS

EMS providers are not permitted to terminate CPR in the field in Japan, and so most patients with OHCA who are treated by EMS personnel are transported to emergency hospitals. Among 1017 OHCA patients, 672 patients including 52 comatose patients with pulses detectable (8%) and 620 cardiac arrest patients (92%) at hospital arrival were enrolled prospectively and consecutively. Twenty-nine patients with good neurological outcome had a significantly higher value of rSO2 at hospital arrival than 643 patients with poor neurological outcome (mean [±SD] 55.6±20.8% vs. 19.7±11.0%, p<0.001). Receiver operating curve analysis indicated an optimal rSO2 cutoff point of >42% for predicting good neurological outcome, with sensitivity 0.79 (95% confidence interval [CI], 0.60-0.92), specificity 0.95 (95% CI, 0.93-0.96), positive predictive value, 0.41 (95% CI, 0.28-0.55), negative predictive value, 0.99 (95% CI, 0.98-1.00), and area under the curve 0.90 (95% CI, 0.88-0.92).

CONCLUSION

The rSO2 at hospital arrival can predict good neurological outcome at 90 days after OHCA.

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

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

Brain monitoring in children

Applying scalp sensors in the operating theater, intensive care, or resuscitation scenarios to detect and monitor brain function is achievable, practical, and affordable. The modalities are complex and the output of the monitor needs careful interpretation. The monitor may have technical problems, and a single reading must be considered with caution. These monitors may have a use for monitoring trends in specific situations, but evidence does not support their widespread use. Nevertheless, research should continue to investigate their role. Future techniques and treatments may show that these monitors can monitor brain function and prevent harm.

Cardiac critical care: what really makes a difference

PURPOSE OF REVIEW

The sustained decline in mortality following congenital heart surgery, while important, also has resulted in an emerging focus upon the use of processes and technological developments to reduce early postoperative morbidity. We summarize here recent efforts within the field of pediatric cardiac intensive care to optimize outcomes associated with the perioperative management of the child with congenital heart disease.

RECENT FINDINGS

Goal-directed and protocol-driven therapy targeting optimization of oxygen delivery improves outcomes in the management of many populations of critically ill patients, and is now increasingly used following congenital heart surgery with a low associated incidence of organ failure and favorable early survival. Restrictive blood product transfusion practices following congenital heart surgery are showing promise in reducing donor exposures and transfusion-associated morbidities without a resulting increase in end organ dysfunction. Technological developments are affording noninvasive opportunities for earlier recognition and intervention in the deteriorating child, while also providing means for support of the failing myocardium, both in an acute setting during cardiopulmonary resuscitation, and among patients with end-stage heart failure requiring longer-term mechanical circulatory support.

SUMMARY

Multi-institutional, prospective evaluation of perioperative management practices, along with patient-specific, integrated electronic health information, provides unique opportunities for investigators to identify and test both processes and technological tools in confronting the most challenging aspects of early postoperative management following congenital heart surgery.

Neonatal brain protection in cardiac surgery and the role of intraoperative neuromonitoring

Improving mortality rates in children undergoing surgery for congenital heart disease has enabled a shift in focus to improving morbidity, particularly with respect to neurological complications. Various factors have been implicated in influencing neurological outcomes. We share our experience in formulating a customized cardiopulmonary bypass (CPB) protocol based on currently available evidence. Theoretical advantages of intraoperative neuromonitoring during CPB, specifically use of near-infrared spectroscopy, will be discussed in the context of methodologies to monitor cerebral perfusion during surgery.

Calibration of a prototype NIRS oximeter against two commercial devices on a blood-lipid phantom

In a blood-lipid liquid phantom the prototype near-infrared spectroscopy oximeter OxyPrem was calibrated against the INVOS® 5100c adult sensor in respect to values of regional tissue oxygen haemoglobin saturation (rStO2) for possible inclusion in the randomised clinical trial - SafeBoosC. In addition different commercial NIRS oximeters were compared on changing haemoglobin oxygen saturation and compared against co-oximetry. The best calibration was achieved with a simple offset and a linear scaling of the OxyPrem rStO2 values. The INVOS adult and pediatric sensor gave systematically different values, while the difference between the NIRO® 300 and the two INVOS sensors were magnitude dependent. The co-oximetry proved unreliable on such low haemoglobin and high Intralipid levels.

Near-Infrared Laser Spectroscopy as a Screening Tool for Detecting Hematoma in Patients with Head Trauma

Introduction:

Among imaging techniques, computed tomography (CT) is a reliable method for detecting intracranial hematomas in patients with head trauma, but it is not generally available in special circumstances like prehospital situations and harsh conditions such as those following an earthquake.

Objective:

The objective of this study is to determine if near-infrared spectroscopy (NIRS) is useful for performing CT scans on patients with closed head trauma that present to medical centers that do not have the ability to perform a CT scan or in prehospital or harsh situations. Near-infrared spectroscopy and CT scan were compared according to sensitivity and specificity.

Methods:

This was an observational, prospective study. One hundred forty-eight patients admitted to Rasool Akram General Hospital in Tehran, Iran with head injuries during a one-month period were studied using NIRS and CT. The observational, prospective study was conducted and sensitivity, specificity, positive and negative predictive values of NIRS were calculated. Chi-square and Kappa analysis was performed, and a p-value <0.05 was considered significant.

Results:

According to the CT scan findings, 54 (36.5%) of the patients developed intracranial hematoma. The NIRS examination showed that 69 patients (46.6%) might have intracranial hematoma. The number of true negatives was 73 and the number of false negatives was six patients. The sensitivity and specificity of NIRS examination was 88.9% and 77.7%, respectively.

Conclusions:

This study speculates that NIRS may be a useful screening tool to detect intracranial hematoma. This capability could be useful in special situations like in a deprived area, medical centers without CT scan capabilities, prehospital situations, and in harsh conditions like those after an earthquake or other disasters that causes increased numbers of victims with closed head trauma.

Does Near-Infrared Spectroscopy Provide an Early Warning of Low Haematocrit following the Initiation of Hypothermic Cardiopulmonary Bypass in Cardiac Surgery?

This study investigated 151 patients undergoing cardiac surgery to determine whether measurement of regional cerebral oxygen saturation (rScO2) using near-infrared spectroscopy (NIRS) can indicate a low haematocrit after initiation of hypothermic cardiopulmonary bypass (CPB). Haematocrit, rScO2, haemoglobin level, arterial partial pressures of carbon dioxide and oxygen, systemic blood pressure, and nasopharyngeal and rectal temperatures were determined 5 min after the initial administration of heparin for CPB and 90 s after completion of the first cardioplegic solution injection. Immediately after initiation of hypothermic CPB, rScO2, haemoglobin and haematocrit values were significantly lower than those before CPB. No significant correlations were found between the change in haematocrit and changes in left, right and mean rScO2; thus, changes in rScO2 before and after initiation of hypothermic CPB did not reflect changes in haematocrit values. This indicates that NIRS cannot provide early warning of a low haematocrit immediately after initiation of hypothermic CPB in cardiac surgery.

Cerebral tissue oxygenation and regional oxygen saturation can be used to study cerebral autoregulation in prematurely born infants

The coupling of cerebral intravascular oxygenation (dHbD) with mean arterial blood pressure (MABP) was taken as a reflection of autoregulation assuming constant arterial oxygen content. However, this method is sensitive to movement artifacts. We examined whether the cerebral tissue oxygenation index (cTOI) and regional oxygen saturation (rScO2) may replace dHbD and changes in total Hb (dHbT), respectively. Correlation (COR) and coherence (COH) were used to measure the agreement of MABP with rScO2/dHbT and cTOI/dHbD. dHbD/cTOI and dHbT/rScO2 recordings of, respectively, 34 and 20 preterm infants in need for intensive care were studied during the first days of life. dHbD and cTOI were obtained with the NIRO300 and rScO2 and dHbT with the INVOS4100. Invasive MABP was measured continuously. COR and COH scores of MABP versus dHbD/dHbT were compared with the corresponding ones by replacing dHbD/dHbT by cTOI/rScO2, respectively. Generally, no significant score differences were found for dHbD/cTOI. Differences for dHbT/rScO2 were slightly larger but still within the normal variation of the parameters. Differences become insignificant when restricting calculations to epochs of larger variation in MABP (>10 mm Hg). Hence, we suggest that cTOI and rScO2 can be used to study cerebral autoregulation in newborns.

Cerebral oximetry for pediatric anesthesia: why do intelligent clinicians disagree?

Reflectance near-infrared spectroscopy has been used to measure cortical tissue oximetry for more than 30 years. In that time, many centers have adopted the routine use of the cerebral oximeter for children having repair of congenital heart lesions, while some prominent academic centers have resisted routine use of these monitors citing lack of definitive evidence for outcome benefit. In this review, we provide an overview of the method used to measure cerebral oximetry, as well as validation and clinical outcome data that have accrued from the use of cerebral oximeters. We discuss the peculiarities of evidentiary review for monitoring devices, and the confounding errors that occur when a monitor is evaluated as a therapeutic intervention. We outline the physiologic basis of cerebral desaturation and the shifts in practice that have occurred with implementation of NIRS monitoring.

Hemodynamics and cerebral oxygenation following repair of tetralogy of Fallot: the effects of converting from positive pressure ventilation to spontaneous breathing

PURPOSE

Following corrective surgery for tetralogy of Fallot (TOF), approximately one-third of these patients develop low cardiac output (CO) due to right ventricular (RV) diastolic heart failure. Extubation is beneficial in these patients because the fall in intrathoracic pressure that occurs with conversion from positive pressure breathing to spontaneous breathing improves venous return, RV filling and CO. We hypothesized that if CO were to increase but remain limited following extubation, the obligatory increase in perfusion to the respiratory pump that occurs with loading of the respiratory musculature may occur at the expense of other vital organs, including the brain.

MATERIALS AND METHODS

We conducted a retrospective analysis of all patients undergoing repair of TOF and monitoring of cerebral oxygenation using near infrared spectroscopy. We evaluated the following parameters two hours prior to and following extubation: mean and systolic arterial blood pressure (MBP, SBP), right atrial pressure (RAP), heart rate (HR) and cerebral oxygenation.

RESULTS

The study included 22 patients. With extubation, MBP and SBP increased significantly from 67.3 ± 6.5 to 71.1 ± 8.4 mm Hg (P= 0.004) and from 87.2 ± 8.6 to 95.9 ± 10.9 mm Hg (P= 0.001), respectively, while the HR remained unchanged (145 vs. 146 bpm). The RAP remained unchanged following extubation (11.9 vs. 12.0 mm Hg). Following extubation, cerebral oxygen saturations increased significantly from 68.5 ± 8.4 to 74.2 ± 7.9% (P < 0.0001). Cerebral oxygen saturations increased by ≥5% in 11 of 22 patients and by ≥10% in 5 of 22 patients.

CONCLUSION

We conclude that converting from positive pressure ventilation to spontaneous negative pressure breathing following repair of TOF significantly improves arterial blood pressure and cerebral oxygenation.