Cerebral near-infrared spectroscopy in adult heart surgery: systematic review of its clinical efficacy

Wolf Creek XVII Part 6: Physiology-Guided CPR

Introduction

Physiology-guided cardiopulmonary resuscitation (CPR) offers the potential to optimize resuscitation and enable early prognosis.

Methods

Physiology-Guided CPR was one of six focus topic for the Wolf Creek XVII Conference held on June 14-17, 2023 in Ann Arbor, Michigan, USA. International thought leaders and scientists in the field of cardiac arrest resuscitation from academia and industry were invited. Participants submitted via online survey knowledge gaps, barriers to translation and research priorities for each focus topic. Expert panels used the survey results and their own perspectives and insights to create and present a preliminary unranked list for each category, which was then debated, revised and ranked by all attendees to identify the top 5 for each category.

Results

Top knowledge gaps include identifying optimal strategies for the evaluation of physiology-guided CPR and the optimal values for existing patients using patient outcomes. The main barriers to translation are the limited usability outside of critical care environments and the training and equipment required for monitoring. The top research priorities are the development of clinically feasible and reliable methods to continuously and non-invasively monitor physiology during CPR and prospective human studies proving targeting parameters during CPR improves outcomes.

Conclusion

Physiology-guided CPR has the potential to provide individualized resuscitation and move away from a one-size-fits-all approach. Current understanding is limited, and clinical trials are lacking. Future developments need to consider the clinical application and applicability of measurement to all healthcare settings. Therefore, clinical trials using physiology-guided CPR for individualisation of resuscitation efforts are needed.

Cerebral oximetry in adult cardiac surgery to reduce the incidence of neurological impairment and hospital length-of-stay: A prospective, randomized, controlled trial

BACKGROUND

Cerebral oximetry using near-infrared spectroscopy (NIRS) has been shown to reduce neurological dysfunction and hospital length-of-stay after adult cardiac surgery in some but not all studies. We audited maintaining cerebral saturations at or above baseline and showed improved neurological and length-of-stay outcomes. Our hypothesis for this study was that our NIRS protocol would improve neurological and length-of-stay outcomes.

METHODS

This prospective, single centre, double-blinded controlled study randomized 182 consecutive patients, scheduled for cardiac surgery using cardiopulmonary bypass. Participants were randomized by concealed envelope prior to anaesthesia. NIRS study group were managed perioperatively using our NIRS protocol of 8 interventions, increase cardiac output, normocapnia, increase mean arterial pressure, increase inspired oxygen, depth of anaesthesia, blood transfusion, correction of bypass cannula, change of surgical plan to restore levels equal to or above baseline. The control group had standard management without NIRS. Primary outcomes were neurological impairment (early and late) and hospital length-of-stay. Secondary outcomes were ventilation times, intensive care length-of-stay, major organ dysfunction and mortality.

RESULTS

91 patients entered each group. There was a significant improvement in self-reported six-month general functionality in the NIRS group (p = 0.016). Early neurological dysfunction and hospital length-of-stay was the same in both groups. Of the secondary outcomes only Intensive Care length-of-stay was statistically significant, being shorter in the NIRS group (p = 0.026).

CONCLUSION

Maintaining cerebral saturations above baseline reduces time spent in Intensive Care and may improve long term functional recovery but not stroke, major organ dysfunction and mortality.

Novel Mode of Near-Infrared Spectroscopy as a Continuous Cerebral Physiological Monitoring Device during Cardiopulmonary Resuscitation: Four Case Reports

Background: NIRO-Pulse is a novel mode of near-infrared spectroscopy that can be used to visually evaluate cerebral perfusion during cardiopulmonary resuscitation (CPR), providing real-time feedback as to the quality of the CPR. The aim of this report was to describe the several representative cases of NIRO-Pulse for physiological monitoring during CPR. Methods: We present several cases from out-of-hospital cardiac arrest (OHCA) patients for whom NIRO-Pulse was attached to the forehead after hospital arrival. Patients were subjected to continuous brain monitoring during CPR using NIRO-Pulse, which allows for the visualisation of ΔHb (Hb pulsation). NIRO-Pulse is capable of simultaneously measuring and displaying cerebral tissue oxygen saturation (SctO2) and Hb pulsation, providing real-time feedback during CPR in the form of physiological indicators, and assessing changes in SctO2 throughout the CPR procedure by post-mortem analysis. Results: We observed several representative cases that provided the following insights: (1) SctO2 increased after a change in the quality of chest compression, (2) SctO2 decreased during the ventilation phase of synchronised CPR, (3) SctO2 decreased during the interruption of chest compressions for the preparation of defibrillation, and (4) SctO2 gradually and continuously increased after return of spontaneous circulation. Conclusion: Displaying Hb pulsation in conjunction with SctO2 during CPR may be helpful for evaluating the quality of and patient responsiveness to CPR. Further studies investigating the association between the use of NIRO-Pulse during CPR and subsequent outcomes should be conducted.

Cerebral oximetry: a developing tool for monitoring cerebral oxygenation during cardiopulmonary resuscitation

Despite improvements in cardiopulmonary resuscitation (CPR), survival and neurologic recovery after cardiac arrest remain very poor because of the impact of severe ischemia and subsequent reperfusion injury. As the likelihood of survival and favorable neurologic outcome decreases with increasing severity of ischemia during CPR, developing methods to measure the magnitude of ischemia during resuscitation, particularly cerebral ischemia, is critical for improving overall outcomes. Cerebral oximetry, which measures regional cerebral oxygen saturation (rSO₂ ) by near-infrared spectroscopy, has emerged as a potentially beneficial marker of cerebral ischemia during CPR. In numerous preclinical and clinical studies, higher rSO₂ during CPR has been associated with improved cardiac arrest survival and neurologic outcome. In this narrative review, we summarize the scientific rationale and validation of cerebral oximetry across populations and pathophysiologic states, discuss the evidence surrounding its use to predict return of spontaneous circulation, rearrest, and neurologic outcome, and provide suggestions for incorporation of cerebral oximetry into CPR practice.

Cerebral Perfusion in Hemodialysis Patients: A Feasibility Study

Background

Patients on hemodialysis (HD) are known to exhibit low values of regional cerebral oxygenation (rSO2) and impaired cognitive functioning. The etiology of both is currently unknown.

Objective

To determine the feasibility of serially monitoring rSO2 in patients initiating HD. In addition, we sought to investigate how rSO2 is related to hemodynamic and dialysis parameters.

Design

Prospective observational study.

Setting

Single-center tertiary academic teaching hospital in Ontario, Canada.

Participants

Six patients initiating HD were enrolled in the study.

Methods

Feasibility was defined as successful study enrollment (>1 patient/month), successful consent rate (>70%), high data capture rates (>90%), and assessment tolerability. Regional cerebral oxygenation monitoring was performed 1 time/wk for the first year of dialysis. A neuropsychological battery was performed 3 times during the study: before dialysis initiation, 3 months, and 1 year after dialysis initiation. The neuropsychological battery included a traditional screening tool: the Repeatable Battery for the Assessment of Neuropsychological Status, and a robot-based assessment: Kinarm.

Results

Our overall consent rate was 33%, and our enrollment rate was 0.4 patients/mo. In total 243 rSO2 sessions were recorded, with a data capture rate of 91.4% (222/243) across the 6 patients. Throughout the study, no adverse interactions were reported. Correlations between rSO2 with hemodynamic and dialysis parameters showed individual patient variability. However, at the individual level, all patients demonstrated positive correlations between mean arterial pressure and rSO2. Patients who had more than 3 liters of fluid showed significant negative correlations with rSO2. Less cognitive impairment was detected after initiating dialysis.

Limitation

This small cohort limits conclusions that can be made between rSO2 and hemodynamic and dialysis parameters.

Conclusions

Prospectively monitoring rSO2 in patients was unfeasible in a single dialysis unit, due to low consent and enrollment rates. However, rSO2 monitoring may provide unique insights into the effects of HD on cerebral oxygenation that should be further investigated.

Trial Registration

Due to the feasibility nature of this study, no trial registration was performed.

The role of non-invasive brain oximetry in adult critically ill patients without primary brain injury

A primary objective in intensive care and perioperative settings is to promote an adequate supply and delivery of oxygen to tissues and organs, particularly to the brain. Cerebral near infrared spectroscopy (NIRS) is a non-invasive, continuous monitoring technique, that can be used to assess cerebral oxygenation. Using NIRS to monitor cerebral oximetry is not new, and has been in widespread use in neonates and cardiac surgery for decades. In addition, it has become common to see NIRS being used in adult and pediatric cardiac surgery, acute neurological diseases, neurosurgical procedures, vascular surgery, severe trauma and other acute medical diseases. Furthermore, recent evidence suggests a role for NIRS in the perioperative settings; detecting and preventing episodes of cerebral desaturation aiming to reduce the development of post-operative delirium. NIRS is not without its limitations; these include the risk of extra-cranial contamination, spatial limitations and skin blood flow/volume changes, as well being a measure of localized blood oxygenation underneath the sensor. However, NIRS is a non-invasive technique and can, therefore, be used in those patients without indications or justification for invasive brain monitoring; non-neurosurgical procedures such as liver transplantation, major orthopedic surgery and critically illness where the brain is at risk. The aim of this manuscript was to discuss the physical principles of NIRS and to report the current evidence regarding its use in critically ill patients without primary non-anoxic brain injury.

Not Removing the Glossy White Cover from Adhesive INVOS Neonatal Sensors Affects the Oxygenation Measurement

The randomized clinical trial, SafeBoosC III, evaluates the effect of treatment guided by cerebral tissue oximetry monitoring in extremely preterm infants. Treatment should be considered, when cerebral oxygen saturation (StO₂) drops below a predefined hypoxic threshold. This threshold value differs between different brands of instruments. To achieve high external validity, in this pragmatic trial all commercially available cerebral tissue oximeters have been accepted, provided their specific hypoxic threshold value has been determined in phantom studies. Since most companies produce sensors with an adhesive surface on the patient-contacting side, in the phantom studies these sensors were applied according to the specifications, i.e., the glossy cover was removed from the sensor. However, since the skin of preterm infants is particularly fragile, some neonatologists keep this cover on the adhesive sensors, to avoid the risk of skin injury when removing the sensor. Therefore, the aim of this study was to determine whether keeping this cover on leads to different StO₂ values. To evaluate the effect of the cover, we performed multiple deoxygenations in a blood-lipid phantom and compared an INVOS neonatal sensor (Medtronic), with and without the cover, to a reference oximeter (OxiplexTS, ISS). As expected, the relationship of the StO₂ between the INVOS neonatal sensor and OxiplexTS was linear (r² = 0.999) with and without cover, but the cover influenced the linear equation: StO_{2_INVOS_cover} = 1.133*StO_{2_ISS} + 7.1 as opposed to StO_{2_INVOS_nocover} = 1.103*StO_{2_ISS} + 12.0. Furthermore, the hypoxic SafeBoosC III threshold differed as well: 60.3% with cover and 63.8% without cover. In conclusion, keeping the adhesive cover on an INVOS neonatal sensor results in lower measured values. At the hypoxic threshold, this is more than 3% (from 60.3% to 63.8%), and therefore, if clinicians keep the cover on the sensor, they need to be aware of this difference.

Comparison of manual and mechanical chest compression techniques using cerebral oximetry in witnessed cardiac arrests at the emergency department: A prospective, randomized clinical study

AIM

We aimed to compare regional cerebral oxygen saturation (rSO₂) levels during cardiopulmonary resuscitation (CPR), performed either manually or using a mechanical chest compression device (MCCD), in witnessed cardiac arrest cases in the emergency department (ED), and to evaluate the effects of both the CPR methods and perfusion levels on patient survival and neurological outcomes.

METHODS

This single-center, randomized study recruited patients aged ≥18 years who had witnessed a cardiopulmonary arrest in the ED. According to the relevant guidelines, CPR was performed either manually or using an MCCD. Simultaneously, rSO₂ levels were continually measured with near-infrared spectroscopy.

RESULTS

Seventy-five cases were randomly distributed between the MCCD (n = 40) and manual CPR (n = 35) groups. No significant difference in mean rSO₂ levels was found between the MCCD and manual CPR groups (46.35 ± 14.04 and 46.60 ± 12.09, respectively; p = 0.541). However, a significant difference in rSO₂ levels was found between patients without return of spontaneous circulation (ROSC) and those with ROSC (40.35 ± 10.05 and 50.50 ± 13.44, respectively; p < 0.001). In predicting ROSC, rSO₂ levels ≥24% provided 100% sensitivity (95% confidence interval [CI] 92-100), and rSO₂ levels ≥64% provided 100% specificity (95% CI 88-100). The area under the curve for ROSC prediction using rSO₂ levels during CPR was 0.74 (95% CI 0.62-0.83).

CONCLUSION

A relationship between ROSC and high rSO₂ levels in witnessed cardiac arrests exists. Monitoring rSO₂ levels during CPR would be useful in CPR management and ROSC prediction. During CPR, MCCD or manual chest compression has no distinct effect on oxygen delivery to the brain.

TRIAL REGISTRATION

clinicaltrials.gov identifier: NCT03238287.

Lawrence K. Optical monitoring of cerebral perfusion and metabolism in adults during cardiac surgery with cardiopulmonary bypass

During cardiac surgery with cardiopulmonary bypass (CPB), adequate maintenance of cerebral blood flow (CBF) is vital in preventing postoperative neurological injury - i.e. stroke, delirium, cognitive impairment. Reductions in CBF large enough to impact cerebral energy metabolism can lead to tissue damage and subsequent brain injury. Current methods for neuromonitoring during surgery are limited. This study presents the clinical translation of a hybrid optical neuromonitor for continuous intraoperative monitoring of cerebral perfusion and metabolism in ten patients undergoing non-emergent cardiac surgery with non-pulsatile CPB. The optical system combines broadband near-infrared spectroscopy (B-NIRS) to measure changes in the oxidation state of cytochrome c oxidase (oxCCO) - a direct marker of cellular energy metabolism - and diffuse correlation spectroscopy (DCS) to provide an index of cerebral blood flow (CBFi). As the heart was arrested and the CPB-pump started, increases in CBFi (88.5 ± 125.7%) and significant decreases in oxCCO (-0.5 ± 0.2 µM) were observed; no changes were noted during transitions off CPB. Fifteen hypoperfusion events, defined as large and sustained reductions in CPB-pump flow rate, were identified across all patients and resulted in significant decreases in perfusion and metabolism when mean arterial pressure dropped to 30 mmHg or below. The maximum reduction in cerebral blood flow preceded the corresponding metabolic reduction by 18.2 ± 15.0 s. Optical neuromonitoring provides a safe and non-invasive approach for assessing intraoperative perfusion and metabolism and has potential in guiding patient management to prevent adverse clinical outcomes.

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.

Regional cerebral oximetry is consistent across self-reported racial groups and predicts 30-day mortality in cardiac surgery: a retrospective analysis

Darker skin pigmentation appears to cause underestimation of regional oxygen saturation (rSO₂) for certain cerebral oximetry devices. This presents a risk of triggering unindicated interventions and may limit its utility for predicting adverse outcomes. Our goal was to quantify the impact of self-reported race on oximetry measurements during cardiac surgery and elucidate whether race has a mediating role in the association of rSO₂ with mortality. Data was extracted from our department's data warehouse for adult patients who underwent on-pump cardiac surgery between June 2014 and June 2018. Intraoperative rSO₂ was recorded every 15 s throughout all cases. After grouping patients by self-reported race, multiple linear regression modeling was utilized to assess the association between race and mean pre-bypass rSO₂ while controlling for various perioperative variables. The role of mean pre-bypass rSO₂ for predicting 30-day mortality was evaluated via multiple logistic regression, and the threshold for rSO₂ was selected by maximizing F1 score. There were 4267 patients included. Compared to Caucasian patients, the unadjusted difference in mean pre-bypass rSO₂ was - 0.6% (95% CI - 1.3 to 0.04) for African American patients, - 1.8% (- 2.7 to - 0.9) for Asian patients, 0.1% (- 0.8 to 1.0) for Hispanic patients, - 1.6% (- 3.0 to - 0.4) for Indian/South Asian patients, and - 1.4% (- 3.7 to 0.9) for Pacific Islander patients. After adjusting for perioperative variables, differences in rSO₂ readings less than 2% were observed between racial groups. Mean pre-bypass rSO₂ under 63% was an independent predictor of higher 30-day mortality risk (OR: 2.86, CI 1.39 to 5.53, p = 0.003), and the interaction variable between rSO₂ and race was not statistically significant (p = 0.299). Cerebral oximetry measurements are more consistent across racial groups than previously reported, supporting its utility for intraoperative monitoring and risk stratification. Pre-intervention rSO₂ is associated with increased 30-day mortality at a higher threshold than previously reported and was not significantly impacted by self-reported race.

Detailed statistical analysis plan for the SafeBoosC III trial: a multinational randomised clinical trial assessing treatment guided by cerebral oxygenation monitoring versus treatment as usual in extremely preterm infants

BACKGROUND

Infants born extremely preterm are at high risk of dying or suffering from severe brain injuries. Treatment guided by monitoring of cerebral oxygenation may reduce the risk of death and neurologic complications. The SafeBoosC III trial evaluates the effects of treatment guided by cerebral oxygenation monitoring versus treatment as usual. This article describes the detailed statistical analysis plan for the main publication, with the aim to prevent outcome reporting bias and data-driven analyses.

METHODS/DESIGN

The SafeBoosC III trial is an investigator-initiated, randomised, multinational, pragmatic phase III trial with a parallel group structure, designed to investigate the benefits and harms of treatment based on cerebral near-infrared spectroscopy monitoring compared with treatment as usual. Randomisation will be 1:1 stratified for neonatal intensive care unit and gestational age (lower gestational age (< 26 weeks) compared to higher gestational age (≥ 26 weeks)). The primary outcome is a composite of death or severe brain injury at 36 weeks postmenstrual age. Primary analysis will be made on the intention-to-treat population for all outcomes, using mixed-model logistic regression adjusting for stratification variables. In the primary analysis, the twin intra-class correlation coefficient will not be considered. However, we will perform sensitivity analyses to address this. Our simulation study suggests that the inclusion of multiple births is unlikely to significantly affect our assessment of intervention effects, and therefore we have chosen the analysis where the twin intra-class correlation coefficient will not be considered as the primary analysis.

DISCUSSION

In line with the Declaration of Helsinki and the International Conference on Harmonization Good Clinical Practice guidelines, we have developed and published this statistical analysis plan for the SafeBoosC III trial, prior to any data analysis.

TRIAL REGISTRATION

ClinicalTrials.org, NCT03770741. Registered on 10 December 2018.

Near-Infrared Spectroscopy Monitoring in Cardiac and Noncardiac Surgery: Pairwise and Network Meta-Analyses

Goal-directed therapy based on brain-oxygen saturation (bSo2) is controversial and hotly debated. While meta-analyses of aggregated data have shown no clinical benefit for brain near-infrared spectroscopy (NIRS)-based interventions after cardiac surgery, no network meta-analyses involving both major cardiac and noncardiac procedures have yet been undertaken. Randomized controlled trials involving NIRS monitoring in both major cardiac and noncardiac surgery were included. Aggregate-level data summary estimates of critical outcomes (postoperative cognitive decline (POCD)/postoperative delirium (POD), acute kidney injury, cardiovascular events, bleeding/need for transfusion, and postoperative mortality) were obtained. NIRS was only associated with protection against POCD/POD in cardiac surgery patients (pooled odds ratio (OR)/95% confidence interval (CI)/I2/number of studies (n): 0.34/0.14-0.85/75%/7), although a favorable effect was observed in the analysis, including both cardiac and noncardiac procedures. However, the benefit of the use of NIRS monitoring was undetectable in Bayesian network meta-analysis, although maintaining bSo2 > 80% of the baseline appeared to have the most pronounced impact. Evidence was imprecise regarding acute kidney injury, cardiovascular events, bleeding/need for transfusion, and postoperative mortality. There is evidence that brain NIRS-based algorithms are effective in preventing POCD/POD in cardiac surgery, but not in major noncardiac surgery. However, the specific target bSo2 threshold has yet to be determined.

Noninvasive Neuromonitoring of Hypothermic Circulatory Arrest in Aortic Surgery

BACKGROUND AND AIMS

Circulatory arrest carries a high risk of neurological damage, but modern monitoring methods lack reliability, and is susceptible to the generalized effects of both anesthesia and hypothermia. The objective of this prospective, explorative study was to research promising, reliable, and noninvasive methods of neuromonitoring, capable of predicting neurological outcome after hypothermic circulatory arrest.

MATERIALS AND METHODS

Thirty patients undergoing hypothermic circulatory arrest during surgery of the thoracic aorta were recruited in a single center and over the course of 4 years. Neuromonitoring was performed with a four-channel electroencephalogram montage and a near-infrared spectroscopy monitor. All data were tested off-line against primary neurological outcome, which was poor if the patient suffered a significant neurological complication (stroke, operative death).

RESULTS

A poor primary neurological outcome seen in 10 (33%) patients. A majority (63%) of the cases were emergency surgery, and thus, no neurological baseline evaluation was possible. The frontal hemispheric asymmetry of electroencephalogram, as measured by the brain symmetry index, predicted primary neurological outcome with a sensitivity of 79 (interquartile range; 62%-88%) and specificity of 71 (interquartile range; 61%-84%) during the first 6 h after end of circulatory arrest.

CONCLUSION

The hemispheric asymmetry of frontal electroencephalogram is inherently resistant to generalized dampening effects and is predictive of primary neurological outcome. The brain symmetry index provides an easy-to-use, noninvasive neuromonitoring method for surgery of the thoracic aorta and postoperative intensive care.

The physiological determinants of near-infrared spectroscopy-derived regional cerebral oxygenation in critically ill adults

Background

To maintain adequate oxygen delivery to tissue, resuscitation of critically ill patients is guided by assessing surrogate markers of perfusion. As there is no direct indicator of cerebral perfusion used in routine critical care, identifying an accurate strategy to monitor brain perfusion is paramount. Near-infrared spectroscopy (NIRS) is a non-invasive technique to quantify regional cerebral oxygenation (rSO₂) that has been used for decades during cardiac surgery which has led to targeted algorithms to optimize rSO₂ being developed. However, these targeted algorithms do not exist during critical care, as the physiological determinants of rSO₂ during critical illness remain poorly understood.

Materials and methods

This prospective observational study was an exploratory analysis of a nested cohort of patients within the CONFOCAL study (NCT02344043) who received high-fidelity vital sign monitoring. Adult patients (≥ 18 years) admitted < 24 h to a medical/surgical intensive care unit were eligible if they had shock and/or required mechanical ventilation. Patients underwent rSO₂ monitoring with the FORESIGHT oximeter for 24 h, vital signs were concurrently recorded, and clinically ordered arterial blood gas samples and hemoglobin concentration were also documented. Simultaneous multiple linear regression was performed using all available predictors, followed by model selection using the corrected Akaike information criterion (AICc).

Results

Our simultaneous multivariate model included age, heart rate, arterial oxygen saturation, mean arterial pressure, pH, partial pressure of oxygen, partial pressure of carbon dioxide (PaCO₂), and hemoglobin concentration. This model accounted for a significant proportion of variance in rSO₂ (R² = 0.58, p < 0.01) and was significantly associated with PaCO₂ (p < 0.05) and hemoglobin concentration (p < 0.01). Our selected regression model using AICc accounted for a significant proportion of variance in rSO₂ (R² = 0.54, p < 0.01) and was significantly related to age (p < 0.05), PaCO₂ (p < 0.01), hemoglobin (p < 0.01), and heart rate (p < 0.05).

Conclusions

Known and established physiological determinants of oxygen delivery accounted for a significant proportion of the rSO₂ signal, which provides evidence that NIRS is a viable modality to assess cerebral oxygenation in critically ill adults. Further elucidation of the determinants of rSO₂ has the potential to develop a NIRS-guided resuscitation algorithm during critical illness.

Trial registration

This trial is registered on clinicaltrials.gov (Identifier: NCT02344043), retrospectively registered January 8, 2015.

Electronic supplementary material

The online version of this article (10.1186/s40635-019-0247-0) contains supplementary material, which is available to authorized users.

Tissue oximetry during cardiac surgery and in the cardiac intensive care unit: A prospective observational trial

Background:

Cerebral oximetry using near-infrared spectroscopy (NIRS) has well-documented benefits during cardiac surgery. The authors tested the hypothesis that NIRS technology can be used at other sites as a tissue oximeter during cardiac surgery and in the Intensive Care Unit (ICU).

Aims:

To establish feasibility of monitoring tissue oximetry during and after cardiac surgery, to examine the correlations between tissue oximetry values and cerebral oximetry values, and to examine correlations between oximetry values and mean arterial pressure (MAP) in order to test whether cerebral oximetry can be used as an index organ.

Settings and Designs:

A large, single-center tertiary care university hospital prospective observational trial of 31 patients undergoing cardiac surgery with cardiopulmonary bypass was conducted.

Materials and Methods:

Oximetry stickers were applied to both sides of the forehead, the nonarterial line forearm, and the skin above one paraspinal muscle. Data were collected from before anesthesia induction until extubation or for at least 24 h in patients who remained intubated.

Statistical Analysis:

Categorical variables were evaluated with Chi-square or Fisher's exact tests, while Wilcoxon rank-sum tests or student's t-tests were used for continuous variables.

Results:

The correlation between cerebral oximetry values and back oximetry values ranged from r = 0.37 to 0.40. The correlation between cerebral oximetry values and forearm oximetry values ranged from r = 0.11 to 0.13. None of the sites correlated with MAP.

Conclusions:

Tissue oximetry at the paraspinal muscle correlates with cerebral oximetry values while at the arm does not. Further research is needed to evaluate the role of tissue oximetry on outcomes such as acute renal failure, prolonged need for mechanical ventilation, stroke, vascular ischemic complications, prolonged ICU and hospital length of stay, and mortality in cardiac surgery.

Optical Fibre-Based Pulse Oximetry Sensor with Contact Force Detection

A novel optical sensor probe combining monitoring of blood oxygen saturation (SpO₂) with contact pressure is presented. This is beneficial as contact pressure is known to affect SpO₂ measurement. The sensor consists of three plastic optical fibres (POF) used to deliver and collect light for pulse oximetry, and a fibre Bragg grating (FBG) sensor to measure contact pressure. All optical fibres are housed in a biocompatible epoxy patch which serves two purposes: (i) to reduce motion artefacts in the photoplethysmogram (PPG), and (ii) to transduce transverse loading into an axial strain in the FBG. Test results show that using a combination of pressure measuring FBG with a reference FBG, reliable results are possible with low hysteresis which are relatively immune to the effects of temperature. The sensor is used to measure the SpO₂ of ten volunteers under different contact pressures with perfusion and skewness indices applied to assess the quality of the PPG. The study revealed that the contact force ranging from 5 to 15 kPa provides errors of <2%. The combined probe has the potential to improve the reliability of reflectance oximeters. In particular, in wearable technology, the probe should find use in optimising the fitting of garments incorporating this technology.

Cerebral near-infrared spectroscopy (NIRS) for perioperative monitoring of brain oxygenation in children and adults

BACKGROUND

Various techniques have been employed for the early detection of perioperative cerebral ischaemia and hypoxia. Cerebral near-infrared spectroscopy (NIRS) is increasingly used in this clinical scenario to monitor brain oxygenation. However, it is unknown whether perioperative cerebral NIRS monitoring and the subsequent treatment strategies are of benefit to patients.

OBJECTIVES

To assess the effects of perioperative cerebral NIRS monitoring and corresponding treatment strategies in adults and children, compared with blinded or no cerebral oxygenation monitoring, or cerebral oxygenation monitoring based on non-NIRS technologies, on the detection of cerebral oxygen desaturation events (CDEs), neurological outcomes, non-neurological outcomes and socioeconomic impact (including cost of hospitalization and length of hospital stay).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 12), Embase (1974 to 20 December 2016) and MEDLINE (PubMed) (1975 to 20 December 2016). We also searched the World Health Organization (WHO) International Clinical Trials Registry Platform for ongoing studies on 20 December 2016. We updated this search in November 2017, but these results have not yet been incorporated in the review. We imposed no language restriction.

SELECTION CRITERIA

We included all relevant randomized controlled trials (RCTs) dealing with the use of cerebral NIRS in the perioperative setting (during the operation and within 72 hours after the operation), including the operating room, the postanaesthesia care unit and the intensive care unit.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies, assessed risk of bias and extracted data. For binary outcomes, we calculated the risk ratio (RR) and its 95% confidence interval (CI). For continuous data, we estimated the mean difference (MD) between groups and its 95% CI. As we expected clinical and methodological heterogeneity between studies, we employed a random-effects model for analyses and we examined the data for heterogeneity (I2 statistic). We created a 'Summary of findings' table using GRADEpro.

MAIN RESULTS

We included 15 studies in the review, comprising a total of 1822 adult participants. There are 12 studies awaiting classification, and eight ongoing studies.None of the 15 included studies considered the paediatric population. Four studies were conducted in the abdominal and orthopaedic surgery setting (lumbar spine, or knee and hip replacement), one study in the carotid endarterectomy setting, and the remaining 10 studies in the aortic or cardiac surgery setting. The main sources of bias in the included studies related to potential conflict of interest from industry sponsorship, unclear blinding status or missing participant data.Two studies with 312 participants considered postoperative neurological injury, however no pooled effect estimate could be calculated due to discordant direction of effect between studies (low-quality evidence). One study (N = 126) in participants undergoing major abdominal surgery reported that 4/66 participants experienced neurological injury with blinded monitoring versus 0/56 in the active monitoring group. A second study (N = 195) in participants having coronary artery bypass surgery reported that 1/96 participants experienced neurological injury in the blinded monitoring group compared with 4/94 participants in the active monitoring group.We are uncertain whether active cerebral NIRS monitoring has an important effect on the risk of postoperative stroke because of the low number of events and wide confidence interval (RR 0.25, 95% CI 0.03 to 2.20; 2 studies, 240 participants; low-quality evidence).We are uncertain whether active cerebral NIRS monitoring has an important effect on postoperative delirium because of the wide confidence interval (RR 0.63, 95% CI 0.27 to 1.45; 1 study, 190 participants; low-quality evidence).Two studies with 126 participants showed that active cerebral NIRS monitoring may reduce the incidence of mild postoperative cognitive dysfunction (POCD) as defined by the original studies at one week after surgery (RR 0.53, 95% CI 0.30 to 0.95, I2 = 49%, low-quality evidence).Based on six studies with 962 participants, there was moderate-quality evidence that active cerebral oxygenation monitoring probably does not decrease the occurrence of POCD (decline in cognitive function) at one week after surgery (RR 0.62, 95% CI 0.37 to 1.04, I2 = 80%). The different type of monitoring equipment in one study could potentially be the cause of the heterogeneity.We are uncertain whether active cerebral NIRS monitoring has an important effect on intraoperative mortality or postoperative mortality because of the low number of events and wide confidence interval (RR 0.63, 95% CI 0.08 to 5.03, I2= 0%; 3 studies, 390 participants; low-quality evidence). There was no evidence to determine whether routine use of NIRS-based cerebral oxygenation monitoring causes adverse effects.

AUTHORS' CONCLUSIONS

The effects of perioperative active cerebral NIRS monitoring of brain oxygenation in adults for reducing the occurrence of short-term, mild POCD are uncertain due to the low quality of the evidence. There is uncertainty as to whether active cerebral NIRS monitoring has an important effect on postoperative stroke, delirium or death because of the low number of events and wide confidence intervals. The conclusions of this review may change when the eight ongoing studies are published and the 12 studies awaiting assessment are classified. More RCTs performed in the paediatric population and high-risk patients undergoing non-cardiac surgery (e.g. neurosurgery, carotid endarterectomy and other surgery) are needed.

A Multicenter Pilot Study Assessing Regional Cerebral Oxygen Desaturation Frequency During Cardiopulmonary Bypass and Responsiveness to an Intervention Algorithm

BACKGROUND

The purpose of this multicenter pilot study was to: (1) determine the frequency of regional cerebral oxygen saturation (rScO2) desaturations during cardiac surgery involving cardiopulmonary bypass (CPB); (2) evaluate the accuracy of clinician-identified rScO2 desaturations compared with those recorded continuously during surgery by the near-infrared spectroscopy (NIRS) monitor; and (3) assess the effectiveness of an intervention algorithm for reversing rScO2 desaturations.

METHODS

Two hundred thirty-five patients undergoing coronary artery bypass graft and/or valvular surgery were enrolled at 8 US centers in this prospective observational study. NIRS (Invos™ 5100C; Covidien) was used to monitor rScO2 during surgery. The frequency and magnitude of rScO2 decrements >20% from preanesthesia baseline were documented, and the efficacy of a standard treatment algorithm for correcting rScO2 was determined. The data from the NIRS monitor were downloaded at the conclusion of surgery and sent to the coordinating center where the number of clinician-identified rScO2 desaturation events was compared with the number detected by the NIRS monitor.

RESULTS

The average rScO2 obtained at baseline (mean ± SD, 61% ± 11%; 99% confidence interval, 57%-65%) and during CPB (62% ± 14%; 57%-67%) was not different. However, rScO2 after separation from CPB (56% ± 11%; 53%-60%) was lower than measurements at baseline and during CPB (P < 0.001). During CPB, rScO2 desaturations occurred in 61% (99% confidence interval, 50%-75%) of patients. The area under the curve for product of magnitude and duration of the rScO2 was (mean ± SD, 145.2; 384.8% × min). Clinicians identified all patients with an rScO2 desaturation but identified only 340 (89.5%) of the 380 total desaturation events. Of the 340 clinician-identified rScO2 desaturation events, 115 resolved with usual clinical care before implementation of the treatment algorithm. For the remaining 225 events, the treatment algorithm resulted in resolution of the rScO2 desaturation in all but 18 patients.

CONCLUSIONS

This multicenter pilot study found that 50% to 75% of patients undergoing cardiac surgery experience one or more rScO2 desaturations during CPB. Nearly 10% of desaturation events were not identified by clinicians, suggesting that appropriate alarming systems should be adopted to alert clinicians of such events. The intervention algorithm was effective in reversing clinically identified rScO2 desaturations in the majority of events.

Classification of somatosensory cortex activities using fNIRS

The ability of the somatosensory cortex in differentiating various tactile sensations is very important for a person to perceive the surrounding environment. In this study, we utilize a lab-made multi-channel functional near-infrared spectroscopy (fNIRS) to discriminate the hemodynamic responses (HRs) of four different tactile stimulations (handshake, ball grasp, poking, and cold temperature) applied to the right hand of eight healthy male subjects. The activated brain areas per stimulation are identified with the t-values between the measured data and the desired hemodynamic response function. Linear discriminant analysis is utilized to classify the acquired data into four classes based on three features (mean, peak value, and skewness) of the associated oxy-hemoglobin (HbO) signals. The HRs evoked by the handshake and poking stimulations showed higher peak values in HbO than the ball grasp and cold temperature stimulations. For comparison purposes, additional two-class classifications of poking vs. temperature and handshake vs. ball grasp were performed. The attained classification accuracies were higher than the corresponding chance levels. Our results indicate that fNIRS can be used as an objective measure discriminating different tactile stimulations from the somatosensory cortex of human brain.

Broadband near-infrared spectroscopy can detect cyanide-induced cytochrome aa3 inhibition in rats: a proof of concept study

PURPOSE

Clinically available near-infrared spectroscopy (NIRS) devices use two to five wavelengths of light to measure the relative amounts of oxyhemoglobin and deoxyhemoglobin in tissue to determine tissue hemoglobin oxygen saturation (StO₂). In addition to StO₂, broadband NIRS devices (using hundreds of wavelengths of light) may be able to measure the oxidation state of mitochondrial cytochrome aa₃ (Cyt_ox) which reflects the subcellular energetic state. We hypothesize that broadband NIRS devices can measure Cyt_ox independent of changes in hemoglobin saturation.

METHODS

In this prospective non-randomized study, 20 male Sprague-Dawley rats (300 g) were anesthetized with isoflurane, tracheally intubated, and ventilated with 100% O₂ containing 2% isoflurane. They were subsequently instrumented with a broadband NIRS device that used a halogen light source coupled to an emitting fibreoptic cable. Three receiving fibreoptic cables were utilized; one analyzed the light source and the other two were directed at the base of the skull. Each receiving fibre was connected to a spectrometer to measure light intensity. Sodium cyanide (NaCN) 5 mg·kg^-1 iv was injected in order to produce cytochrome aa₃ reduction. Two to three minutes after injection, oxygen was eliminated and 100% nitrogen (i.e., anoxia) was used for ventilation in order to induce a reduction in both cytochrome aa₃ and hemoglobin desaturation. Changes in the cytochrome oxidation state and hemoglobin oxygenation were calculated using a broadband algorithm and compared before and after both the NaCN and anoxia interventions.

RESULTS

The NaCN injection resulted in a decrease in median [interquartile range (IQR)] deoxyhemoglobin (-0.014 [-0.29 to -0.005] arbitrary units [AU]; P < 0.001), an increase in oxyhemoglobin (0.013 [-0.011 to 0.031] AU; P < 0.001), and a reduction in cytochrome aa₃ (-0.015 [-0.020 to -0.011] AU; P < 0.001). Anoxia resulted in an increase in median [IQR] deoxyhemoglobin (0.13 [0.11 to 0.18] AU; P < 0.001), a decrease in oxyhemoglobin (-0.17 [-0.22 to -0.15] AU; P < 0.001), and a reduction in cytochrome aa₃ (-0.04 [-0.06 to -0.03] AU; P < 0.001).

CONCLUSION

Broadband NIRS can effectively measure the directionality of changes in both Cyt_ox and StO₂ by uncoupling the cytochrome and hemoglobin signals through inhibition of the electron transport chain and anoxia.

The Correlation of Two Cerebral Saturation Monitors With Jugular Bulb Oxygen Saturation in Children Undergoing Cardiopulmonary Bypass for Congenital Heart Surgery

Background:

Near-infrared spectroscopy (NIRS) is a noninvasive monitoring technique that measures regional cerebral oxygen saturation (rSO2).

Objectives:

The primary aim was to compare the output of 2 NIRS-based cerebral oximetry devices, FORESIGHT (CAS Medical Systems Inc, Branford, Connecticut) and INVOS (Covidien, Boulder, Colorado), to venous oxygen saturations from the jugular venous bulb at cannulation and decannulation of the superior vena cava (SVC). Secondary objectives included evaluating correlations of cerebral saturation, as measured by the NIRS devices, with mean arterial blood pressure (MAP), measured by an invasive arterial line, and end-tidal CO2 (ETCO2).

Methods:

Near-infrared spectroscopy, MAP, and ETCO2 data were collected at 13 defined events during each case when hemodynamic instability was expected. At SVC cannulation and decannulation, a 0.1 mL sample of blood was collected from the jugular bulb by the surgeon using a long angiocatheter. The oxygen saturation of these blood samples was measured using an AVOX device and compared with contemporaneous readings from the NIRS probes. Mixed-effects linear regression was used to correlate MAP or ETCO2 with cerebral oxygen saturation (by NIRS) at each time point.

Results:

Children undergoing cardiopulmonary bypass for congenital heart surgery (n = 34) were enrolled in the study. At SVC cannulation, both INVOS ( r = .78) and FORESIGHT ( r = .59) were correlated with AVOX data at P < .001, although the correlation with INVOS was significantly stronger ( P = .003). At SVC decannulation, INVOS ( r = .68; P < .001) and FORESIGHT ( r = .60; P < .001) were similarly correlated with jugular venous rSO2. Correlations of rSO2 (by NIRS) with MAP and ETCO2 levels were stronger than correlations between rSO2 change and change in MAP or ETCO2.

Conclusion:

INVOS correlated more strongly than FORESIGHT with the jugular bulb rSO2 at SVC cannulation but may have underestimated oxygen saturation at low rSO2 values. Data from both NIRS devices were correlated with MAP and ETCO2 over the case duration.

Cerebral Oximetry Monitoring to Maintain Normal Cerebral Oxygen Saturation during High-risk Cardiac Surgery: A Randomized Controlled Feasibility Trial

BACKGROUND

Cerebral oxygen desaturation during cardiac surgery has been associated with adverse perioperative outcomes. Before a large multicenter randomized controlled trial (RCT) on the impact of preventing desaturations on perioperative outcomes, the authors undertook a randomized prospective, parallel-arm, multicenter feasibility RCT to determine whether an intervention algorithm could prevent desaturations.

METHODS

Eight Canadian sites randomized 201 patients between April 2012 and October 2013. The primary outcome was the success rate of reversing cerebral desaturations below 10% relative to baseline in the intervention group. Anesthesiologists were blinded to the cerebral saturation values in the control group. Intensive care unit personnel were blinded to cerebral saturation values for both groups. Secondary outcomes included the area under the curve of cerebral desaturation load, enrolment rates, and a 30-day follow-up for adverse events.

RESULTS

Cerebral desaturations occurred in 71 (70%) of the 102 intervention group patients and 56 (57%) of the 99 control group patients (P = 0.04). Reversal was successful in 69 (97%) of the intervention group patients. The mean cerebral desaturation load (SD) in the operating room was smaller for intervention group patients compared with control group patients (104 [217] %.min vs. 398 [869] %.min, mean difference, -294; 95% CI, -562 to -26; P = 0.03). This was also true in the intensive care unit (P = 0.02). There were no differences in adverse events between the groups.

CONCLUSIONS

Study sites were successful in reversal of desaturation, patient recruitment, randomization, and follow-up in cardiac surgery, supporting the feasibility of conducting a large multicenter RCT.

Lower Extremity Near-infrared Spectroscopy After Popliteal Block For Orthopaedic Foot Surgery

Background:

Noninvasive measurement of cutaneous tissue oxygenation using near-infrared spectroscopy (NIRS) has become common in peri-operative care. Following institution of peripheral nerve blocks, neurovascular alterations in the blocked region have been described.

Objective:

The primary aim of this study encompassed the assessment of the influence of a popliteal block on changes in regional oxygen saturation (SrO₂), and the location of most prominent changes.

Method:

We conducted a prospective randomised controlled trial. Hundred twenty patients who received a popliteal block for foot surgery were included. Popliteal block was performed under echographic guidance. The patients were randomized in 3 groups according to the location of the SrO₂ electrodes on the legs. Bilateral SrO₂ measurements were performed simultaneously. SrO₂ in the operated leg and in the control leg was measured at baseline and 1, 5, 10, 15, and 30 minutes after the perineural injection. We quantified the evolution in SrO₂ by calculating over time the differences in SrO₂ values between the operated and control leg (=ΔSrO₂).

Results:

At 30 minutes, ΔSrO₂ increased significantly (p<0.05) at the plantar side of the foot (11.3% ± 2.9%), above the ankle (4.9% ± 1.3%) and the popliteal fossa (3.6% ± 1.2%).

Conclusion:

At 30 minutes after institution of the popliteal block, ΔSrO₂ was most prominent at the plantar side of the foot as compared with measurement performed above the ankle or under the knee.

The Effect of Compression Stockings on Cerebral Desaturation Events in Obese Patients Undergoing Shoulder Arthroscopy in the Beach-Chair Position

PURPOSE

To determine if the use of thigh-high compression stockings could decrease the incidence of cerebral desaturation events (CDEs) in patients with a body mass index (BMI) of 30 kg/m(2) or greater undergoing shoulder arthroscopy in the beach-chair position (BCP).

METHODS

Between December 2013 and May 2014, 23 patients aged 18 years or older with a BMI of 30 kg/m(2) or greater undergoing shoulder arthroscopy in the BCP were monitored intraoperatively using near-infrared spectroscopy while wearing thigh-high compression stockings. Data obtained on these patients were compared with data from a previous cohort at our institution comprising 24 patients with a BMI of 30 kg/m(2) or greater who underwent elective shoulder arthroscopy in the BCP with the same monitoring but without wearing compression stockings. The incidence of CDEs was identified in each group.

RESULTS

The incidence of CDEs in the group with compression stockings was 4% (1 of 23) compared with 18% (7 of 24) in the group without compression stockings (P = .048). There were no statistically significant differences in mean age (53.0 years v 53.3 years, P = .91), mean BMI (34.5 kg/m(2)v 36.2 kg/m(2), P = .21), or various medical comorbidities between the treatment group and control group. There was a significant difference in the operative time between the treatment group (156.6 minutes) and control group (94.1 minutes) (P < .001).

CONCLUSIONS

The use of thigh-high compression stockings may decrease the incidence of CDEs in obese patients undergoing shoulder arthroscopy in the BCP.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

The Effects of Near-Infrared Spectroscopy on the Neurocognitive Functions in the Patients Undergoing Coronary Artery Bypass Grafting with Asymptomatic Carotid Artery Disease: A Randomized Prospective Study

PURPOSE

The purpose of this study was to research the use of near-infrared spectroscopy (NIRS) on the neurocognitive functions in the patients undergoing coronary artery bypass grafting (CABG) with asymptomatic carotid artery disease.

METHODS

The study design was carried out with the participation of 79 patients in a prospective, randomized and double blind control method. The patients were separated into two groups as NIRS (n = 43) and no NIRS (n = 36). A neurocognitive test was applied preoperatively and postoperatively to all patients before discharge. Cognitive functions were evaluated by applying the Montreal Cognitive Assessment test (MoCA).

RESULTS

The decrease in the postoperative score of mean MoCA in no NIRS group was statistically significant when compared to preoperatively (p <0.001). Postoperative mean MoCA score was found to be significantly higher in NIRS group (NIRS: 26.8 ± 1.9 vs. no NIRS: 23.6 ± 2.5, p <0.001). It has been determined that there was a moderately positive significant correlation between the increase in the NIRS used patients (%) and increase in the MoCA score of the patients (r = 0.59, p <0.001).

CONCLUSION

Intraoperative NIRS usage in the patients undergoing CABG with carotid artery disease might be useful due to its postoperative positive effects on the cognitive functions.

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.

Single-trial lie detection using a combined fNIRS-polygraph system

Deception is a human behavior that many people experience in daily life. It involves complex neuronal activities in addition to several physiological changes in the body. A polygraph, which can measure some of the physiological responses from the body, has been widely employed in lie-detection. Many researchers, however, believe that lie detection can become more precise if the neuronal changes that occur in the process of deception can be isolated and measured. In this study, we combine both measures (i.e., physiological and neuronal changes) for enhanced lie-detection. Specifically, to investigate the deception-related hemodynamic response, functional near-infrared spectroscopy (fNIRS) is applied at the prefrontal cortex besides a commercially available polygraph system. A mock crime scenario with a single-trial stimulus is set up as a deception protocol. The acquired data are classified into “true” and “lie” classes based on the fNIRS-based hemoglobin-concentration changes and polygraph-based physiological signal changes. Linear discriminant analysis is utilized as a classifier. The results indicate that the combined fNIRS-polygraph system delivers much higher classification accuracy than that of a singular system. This study demonstrates a plausible solution toward single-trial lie-detection by combining fNIRS and the polygraph.

Percutaneous superior vena cava drainage during minimally invasive mitral valve surgery: a randomized, crossover study

OBJECTIVE

Minimally invasive techniques commonly are applied to mitral valve surgery; however, there has been little research investigating the optimal methods of cardiopulmonary bypass for the right minithoracotomy approach. Controversy exists as to whether a percutaneous superior vena cava drainage cannula (PSVC) is necessary during these operations. The authors, therefore, sought to determine the effect of using a percutaneous superior vena cava catheter on brain near-infrared spectroscopy, blood lactate levels, hemodynamics and surgical parameters.

DESIGN

Randomized, blinded, crossover trial.

SETTING

Tertiary care university hospital.

PARTICIPANTS

Patients undergoing minimally invasive mitral valve surgery via a right minithoracotomy.

INTERVENTIONS

Twenty minutes of either clamped or unclamped percutaneous superior vena cava neck catheter drainage, during mitral valve repair.

MEASUREMENT AND MAIN RESULTS

For the primary outcome of brain near-infrared spectroscopy, there were no differences between the two groups (percutaneous superior vena cava clamped 55.0%±11.6% versus unclamped 56.1%±10.2%) (p = 0.283). For the secondary outcomes pH (clamped 7.35±0.05 versus unclamped 7.37±0.05 p = 0.015), surgical score (clamped 1.96±1.14 versus unclamped 1.22±0.51 p = 0.002) and CVP (clamped 11.6 mmHg±4.8 mmHg versus unclamped 6.1 mmHg±6.1 mmHg p<0.001) were significantly different.

CONCLUSIONS

The use of a percutaneous superior vena cava drainage improved surgical visualization and lowered CVP, but had no effect on brain near infrared spectroscopy during minimally invasive mitral valve surgery. (ClinicalTrials.gov Identifier: NCT01166841).

Innovative approaches in the perioperative care of the cardiac surgical patient in the operating room and intensive care unit

Perioperative care for cardiac surgery is undergoing rapid evolution. Many of the changes involve the application of novel technologies to tackle common challenges in optimizing perioperative management. Herein, we illustrate recent advances in perioperative management by focusing on a number of novel components that we judge to be particularly important. These include: the introduction of brain and somatic oximetry; transesophageal echocardiographic hemodynamic monitoring and bedside focused ultrasound; ultrasound-guided vascular access; point-of-care coagulation surveillance; right ventricular pressure monitoring; novel inhaled treatment for right ventricular failure; new approaches for postoperative pain management; novel approaches in specialized care procedures to ensure quality control; and specific approaches to optimize the management for postoperative cardiac arrest. Herein, we discuss the reasons that each of these components are particularly important in improving perioperative care, describe how they can be addressed, and their impact in the care of patients who undergo cardiac surgery.

Comparison of R2' measurement methods in the normal brain at 3 Tesla

PURPOSE

R2', the reversible component of transverse relaxation, is an important susceptibility measurement for studies of brain physiology and pathologies. In existing literature, different R2' measurement methods are used with assumption of equivalency. This study explores the choice of measurement method in healthy, young subjects at 3T.

METHODS

In this study, a modified gradient-echo sampling of free induction decay and echo (GESFIDE) sequence was used to compare four standard R2' measurement methods: asymmetric spin echo (ASE), standard GESFIDE, gradient echo sampling of the spin echo (GESSE), and separate R2 and R2* mapping.

RESULTS

GESSE returned lower R2' measurements than other methods (P < 0.05). Intersubject mean R2' in gray matter was found to be 2.7 s(-1) using standard GESFIDE and GESSE, versus 3.4-3.8 s(-1) using other methods. In white matter, mean R2' from GESSE was 2.3 s(-1) while other methods produced 3.7-4.3 s(-1) . R2 correction was applied to partially reduce the discrepancies between the methods, but significant differences remained, likely due to violation of the fundamental assumption of a single-compartmental tissue model, and hence monoexponential decay.

CONCLUSION

R2' measurements are influenced significantly by the choice of method. Awareness of this issue is important when designing and interpreting studies that involve R2' measurements.

Survey of the clinical assessment and utility of near-infrared cerebral oximetry in cardiac surgery

OBJECTIVES

Near-infrared cerebral oximetry increasingly is used for monitoring during cardiac surgery. Nonetheless, the scientific basis for incorporating this technology into clinical practice, the indications for when to do so, and standard diagnostic and treatment algorithms for defining abnormal values are yet to be rigorously defined. The authors hypothesized that there would be (1) variation in clinical use and practices for near-infrared spectroscopy (NIRS), and (2) variation in management of patients when clinicians are provided with NIRS information. In order to test this hypothesis, they sought to assess the nature and strength of response heterogeneity among anesthesiologists and cardiac perfusionists when provided with cardiac surgery patient scenarios and cerebral oximetry data.

DESIGN

A prospectively collected survey.

SETTING

A hospital-based, multi-institutional, multinational study.

PARTICIPANTS

By e-mail, the authors surveyed the membership of the Society of Cardiovascular Anesthesiologists and the online Cardiovascular Perfusion Forum.

INTERVENTIONS

This survey was focused on ascertaining what actions clinicians would take in each scenario, given case information and cerebral oximetry tracings. Questions were based on 11 patient scenarios selected to represent small, large, symmetric, or asymmetric decreases in measured regional cerebral oxygen saturation (rScO2) encountered during cardiac surgery. Information on the respondents' (n = 796; 73% anesthesiologists) clinical practice, demography, and cerebral oximetry utilization was collected. An index of dispersion was used to assess response heterogeneity overall and within demographic subgroups.

MEASUREMENTS AND MAIN RESULTS

The majority of respondents indicated that cerebral oximetry monitoring was either useful or an essential monitor, especially perfusionists and clinicians who used cerebral oximetry most frequently. There were marked differences in responses between perfusionists and anesthesiologists for 4 of the 6 scenarios (p<0.005 for each of these 4 scenarios) occurring during cardiopulmonary bypass. Scenarios having greatest rScO2 reduction or asymmetry in rScO2 were associated with the highest dispersion, indicating least agreement in management. Scenarios with mild or moderate rScO2 reduction were associated with the lowest dispersion, indicating greater agreement in management.

CONCLUSIONS

Although experimental data gradually are accumulating to support the role for cerebral oximetry monitoring during cardiac surgery, the results of the present survey support the view that its role remains poorly defined, and consensus for its appropriate use is lacking. Importantly, the authors observed marked variation in the use, perceived utility, and management of patients for 4 of the 6 CPB scenarios between perfusionists and anesthesiologists who share the management of CPB. These findings support the need for well-designed, adequately-powered clinical trials examining the value of this technology.

Fast optical signals in the sensorimotor cortex: General Linear Convolution Model applied to multiple source-detector distance-based data

In this study, we applied the General Linear Convolution Model to detect fast optical signals (FOS) in the somatosensory cortex, and to study their dependence on the source-detector separation distance (2.0 to 3.5 cm) and irradiated light wavelength (690 and 830 nm). We modeled the impulse response function as a rectangular function that lasted 30 ms, with variable time delay with respect to the stimulus onset. The model was tested in a cohort of 20 healthy volunteers who underwent supra-motor threshold electrical stimulation of the median nerve. The impulse response function quantified the time delay for the maximal response at 70 ms to 110 ms after stimulus onset, in agreement with classical somatosensory-evoked potentials in the literature, previous optical imaging studies based on a grand-average approach, and grand-average based processing. Phase signals at longer wavelength were used to identify FOS for all the source-detector separation distances, but the shortest one. Intensity signals only detected FOS at the greatest distance; i.e., for the largest channel depth. There was no activation for the shorter wavelength light. Correlational analysis between the phase and intensity of FOS further confirmed diffusive rather than optical absorption changes associated with neuronal activity in the activated cortical volume. Our study demonstrates the reliability of our method based on the General Linear Convolution Model for the detection of fast cortical activation through FOS.

Reversal of decreases in cerebral saturation in high-risk cardiac surgery

OBJECTIVES

To measure the incidence of cerebral desaturation during high-risk cardiac surgery and to evaluate strategies to reverse cerebral desaturation.

DESIGN

Prospective observational study followed by a randomized controlled study with 1 intervention group and 1 control group.

SETTING

Tertiary care center specialized in cardiac surgery.

PARTICIPANTS

All patients were scheduled for high-risk cardiac surgery, 279 consecutive patients in the prospective study and 48 patients in the randomized study.

INTERVENTIONS

An algorithmic approach of strategies to reverse cerebral desaturation. In the control group, no attempts were made to reverse cerebral desaturation.

MEASUREMENTS AND MAIN RESULTS

Cerebral saturation was measured using near-infrared reflectance spectroscopy. A decrease of 20% from baseline for 15 seconds defined cerebral desaturation. The success or failure of the interventions was noted. Demographic data were collected. Models for predicting the probability and the reversal of cerebral desaturation were based on multiple logistic regressions. In the randomized study, 12 hours of measurements were continued in the intensive care unit without interventions. Differences in desaturation load (% desaturation × time) were compared between groups. Half of the high-risk patients had cerebral desaturation that could be reversed 88% of the time. Interventions resulted in smaller desaturation loads in the operating room and in the intensive care unit.

CONCLUSIONS

Cerebral desaturation in high-risk cardiac surgery is frequent but can be reversed most of the time resulting in a smaller desaturation load. A large randomized study will be needed to measure the impact of reversing cerebral desaturation on patient's outcome.

Cerebral near-infrared spectroscopy monitoring and neurologic outcomes in adult cardiac surgery patients: a systematic review

BACKGROUND

Near-infrared spectroscopy is used during cardiac surgery to monitor the adequacy of cerebral perfusion. In this systematic review, we evaluated available data for adult patients to determine (1) whether decrements in cerebral oximetry during cardiac surgery are associated with stroke, postoperative cognitive dysfunction (POCD), or delirium; and (2) whether interventions aimed at correcting cerebral oximetry decrements improve neurologic outcomes.

METHODS

We searched PubMed, Cochrane, and Embase databases from inception until January 31, 2012, without restriction on languages. Each article was examined for additional references. A publication was excluded if it did not include original data (e.g., review, commentary) or if it was not published as a full-length article in a peer-reviewed journal (e.g., abstract only). The identified abstracts were screened first, and full texts of eligible articles were reviewed independently by 2 investigators. For eligible publications, we recorded the number of subjects, type of surgery, and criteria for diagnosis of neurologic end points.

RESULTS

We identified 13 case reports, 27 observational studies, and 2 prospectively randomized intervention trials that met our inclusion criteria. Case reports and 2 observational studies contained anecdotal evidence suggesting that regional cerebral O(2) saturation (rSco(2)) monitoring could be used to identify cardiopulmonary bypass cannula malposition. Six of 9 observational studies reported an association between acute rSco(2) desaturation and POCD based on the Mini-Mental State Examination (n = 3 studies) or more detailed cognitive testing (n = 6 studies). Two retrospective studies reported a relationship between rSco(2) desaturation and stroke or type I and II neurologic injury after surgery. The observational studies had many limitations, including small sample size, assessments only during the immediate postoperative period, and failure to perform risk adjustments. Two randomized studies evaluated the efficacy of interventions for treating rSco(2) desaturation during surgery, but adherence to the protocol was poor in one. In the other study, interventions for rSco(2) desaturation were associated with less major organ injury and shorter intensive care unit hospitalization compared with nonintervention.

CONCLUSIONS

Reductions in rSco(2) during cardiac surgery may identify cardiopulmonary bypass cannula malposition, particularly during aortic surgery. Only low-level evidence links low rSco(2) during cardiac surgery to postoperative neurologic complications, and data are insufficient to conclude that interventions to improve rSco(2) desaturation prevent stroke or POCD.

Fast optical signal in visual cortex: Improving detection by General Linear Convolution Model

In this study we applied the General Linear Convolution Model to fast optical signals (FOS). We modeled the Impulse Response Function (IRF) as a rectangular function lasting 30ms, with variable time delay with respect to the stimulus onset. Simulated data confirmed the feasibility of this approach and its capability of detecting simulated activations in case of very unfavorable Signal to Noise Ratio (SNR), providing better results than the grand average method. The model was tested in a cohort of 10 healthy volunteers who underwent to hemi-field visual stimulation. Experimental data quantified the IRF time delay at 80-100ms after the stimulus onset, in agreement with classical visual evoked potential literature and previous optical imaging studies based on grand average approach and a larger number of trails. FOS confirmed the expected contralateral activation in the occipital region. Correlational analysis between hemodynamic intensity signal, phase and intensity FOS supports diffusive rather than optical absorption changes associated with neuronal activity in the activated cortical volume. Our study provides a feasible method for detecting fast cortical activations by means of FOS.

Near infrared spectroscopy (NIRS) of the thenar eminence in anesthesia and intensive care

Near infrared spectroscopy of the thenar eminence (NIRS_th) is a noninvasive bedside method for assessing tissue oxygenation. The NIRS probe emits light with several wavelengths in the 700- to 850-nm interval and measures the reflected light mainly from a predefined depth. Complex physical models then allow the measurement of the relative concentrations of oxy and deoxyhemoglobin, and thus tissue saturation (StO₂), as well as an approximation of the tissue hemoglobin, given as tissue hemoglobin index.

Here we review of current knowledge of the application of NIRS_th in anesthesia and intensive care.

We performed an analytical and descriptive review of the literature using the terms “near-infrared spectroscopy” combined with “anesthesia,” “anesthesiology,” “intensive care,” “critical care,” “sepsis,” “bleeding,” “hemorrhage,” “surgery,” and “trauma” with particular focus on all NIRS studies involving measurement at the thenar eminence.

We found that NIRS_th has been applied as clinical research tool to perform both static and dynamic assessment of StO₂. Specifically, a vascular occlusion test (VOT) with a pressure cuff can be used to provide a dynamic assessment of the tissue oxygenation response to ischemia. StO₂ changes during such induced ischemia-reperfusion yield information on oxygen consumption and microvasculatory reactivity. Some evidence suggests that StO₂ during VOT can detect fluid responsiveness during surgery. In hypovolemic shock, StO₂ can help to predict outcome, but not in septic shock. In contrast, NIRS parameters during VOT increase the diagnostic and prognostic accuracy in both hypovolemic and septic shock. Minimal data are available on static or dynamic StO₂ used to guide therapy.

Although the available data are promising, further studies are necessary before NIRS_th can become part of routine clinical practice.

A feasibility study evaluating the role of cerebral oximetry in predicting return of spontaneous circulation in cardiac arrest

To date there has been no reliable noninvasive real time monitoring available to determine cerebral perfusion during cardiac arrest.

OBJECTIVES

To investigate the feasibility of using a commercially available cerebral oximeter during in-hospital cardiac arrest, and determine whether this parameter predicts return of spontaneous circulation (ROSC).

METHODS

Cerebral oximetry was incorporated in cardiac arrest management in 19 in-hospital cardiac arrest cases, five of whom had ROSC. The primary outcome measure was the relationship between rSO(2) and ROSC.

RESULTS

The use of cerebral oximetry was found to be feasible during in hospital cardiac arrest and did not interfere with management. Patients with ROSC had a significantly higher overall mean ± SE rSO(2) (35 ± 5 vs. 18 ± 0.4, p<0.001). The difference in mean rSO(2) between survivors and non-survivors was most pronounced in the final 5 min of cardiac arrest (48 ± 1 vs. 15 ± 0.2, p<0.0001) and appeared to herald imminent ROSC. Although spending a significantly higher portion of time with an rSO(2)>40% was found in survivors (p<0.0001), patients with ROSC had an rSO(2) above 30% for >50% of the duration of cardiac arrest, whereas non-survivors had an rSO(2) that was below 30%>50% of their cardiac arrest. Patients with ROSC also had a significantly higher change in rSO(2) from baseline compared to non-survivors (310% ± 60% vs. 150% ± 27%, p<0.05).

CONCLUSION

Cerebral oximetry may have a role in predicting ROSC and the optimization of cerebral perfusion during cardiac arrest.