Review article: cerebral near-infrared spectroscopy in adults: a work in progress

Near-infrared spectroscopy to monitor cerebral and renal oxygen saturation during cardiopulmonary bypass surgery for paediatric congenital heart disease: study protocol for a prospective observational cohort trial

BACKGROUND

Current indicators for monitoring intraoperative organ function remain predominantly indirect, delayed and non-specific, particularly in paediatric populations undergoing congenital heart surgery, where multifactorial influences further complicate functional assessments. Emerging evidence suggests that the use of near-infrared spectroscopy (NIRS) technology to continuously monitor the regional oxygen saturation (rSO₂) of intraoperative organs can predict the postoperative organ functional status. This study aims to investigate the associations between intraoperative cerebral/renal rSO₂ fluctuations monitored by NIRS and postoperative neurological injury or acute kidney injury (AKI) in paediatric congenital heart disease (CHD) surgery.

METHODS AND ANALYSIS

In this prospective observational cohort study, patients ≤18 years, scheduled for CHD surgery under cardiopulmonary bypass (CPB), will be enrolled after obtaining written informed consent. Exclusion criteria include pre-existing neuropsychiatric disorders, chronic kidney disease or other related disorders. Dual-channel NIRS probes will be applied to simultaneously monitor cerebral and renal rSO₂ from anaesthesia induction until the patient is transferred to the cardiac care unit. Serum S100 calcium-binding protein B (S100B) levels will be measured before CPB, at the end of the surgery and on postoperative day 1 to quantify cerebral injury. AKI will be diagnosed using the paediatric risk, injury, failure, loss, end-stage renal disease (pRIFLE) criteria based on dynamic creatinine changes. Health-related quality of life will be assessed through the paediatric quality of life (PedsQL) inventory at preoperative baseline and postoperative day 30.

ETHICS AND DISSEMINATION

This study has been approved by the Institutional Review Board of Beijing Children's Hospital (approval number: [2024]-Y-093-D). Prior to enrolment, written informed consent will be obtained from the parents or legal guardians of all participating minors. The findings of this research will be disseminated through peer-reviewed publications and presentations at relevant conferences and shared with participating communities via lay summaries and social media platforms.

TRIAL REGISTRATION NUMBER

The study was registered with the Chinese Clinical Trial Registry on 18 April 2024 (ChiCTR2400083225).

Effects of noradrenaline and phenylephrine on cerebral oxygen saturation during cardiopulmonary bypass in cardiac surgery

Cardiopulmonary bypass (CPB) in cardiac surgery is associated with a high risk of postoperative neurological complications. Perioperative use of vasopressors is common to counteract arterial hypotension in this setting. However, use of α-agonist vasopressors has been associated with cerebral desaturations. Given that reductions in cerebral oxygen saturation (S c O 2 ${S_{{\mathrm{c}}{{\mathrm{O}}_2}}}$ ) can increase postoperative neurological dysfunction, we aimed to investigate the impact of noradrenaline (NA) and phenylephrine (PE) onS c O 2 ${S_{{\mathrm{c}}{{\mathrm{O}}_2}}}$ during the CPB period of a cardiac surgery in 36 patients scheduled for an elective cardiac surgery. Patients were randomized to the intra-operative use of either NA or PE. During CPB, mean arterial pressure (MAP) was elevated pharmacologically to predefined thresholds of 60 and 80 mmHg, while CPB flow was kept constant. TheS c O 2 ${S_{{\mathrm{c}}{{\mathrm{O}}_2}}}$ values were recorded for 5 min per MAP threshold. The MAP increased adequately between thresholds of 60 and 80 mmHg (NA, 59 ± 3 vs. 81 ± 3 mmHg and PE, 61 ± 4 vs. 81 ± 3 mmHg; P ˂ 0.01). TheS c O 2 ${S_{{\mathrm{c}}{{\mathrm{O}}_2}}}$ decreased between pressure thresholds of 60 and 80 mmHg (NA, 70 ± 11 vs. 69 ± 11 mmHg and PE, 64 ± 11 vs. 63 ± 11 mmHg; P ˂ 0.01). Reduction inS c O 2 ${S_{{\mathrm{c}}{{\mathrm{O}}_2}}}$ did not differ between vasopressors. The mean relative decrease inS c O 2 ${S_{{\mathrm{c}}{{\mathrm{O}}_2}}}$ across groups was 2.0% (95% confidence interval: 0.6 to 2.1). Elevation in MAP mediated solely by vasopressors induces significant decreases inS c O 2 ${S_{{\mathrm{c}}{{\mathrm{O}}_2}}}$ during cardiac surgery under CPB. However, their impact onS c O 2 ${S_{{\mathrm{c}}{{\mathrm{O}}_2}}}$ remains clinically non-significant according to current guidelines.

Prospective single-center study on the reliability of ipsilateral cerebral oximetry using near-infrared spectroscopy as a predictor for selective shunting during carotid endarterectomy

OBJECTIVE

Many techniques are available for the intraoperative assessment of brain perfusion during carotid endarterectomy, such as carotid stump pressure, near-infrared spectroscopy, somatosensory evoked potentials, transcranial Doppler, electroencephalography, and clinical assessment. The decision for selective carotid shunt insertion is dependent on clinical deterioration or the detection of cerebral hypoperfusion after cross-clamping of the internal carotid artery. Monitoring cerebral oximetry using near-infrared spectroscopy is a noninvasive technique for cerebral oxygen saturation measurement, reflecting changes in cerebral blood flow during carotid endarterectomy. The aim of this study was to evaluate the reliability of near-infrared spectroscopy as a predictor of selective shunting during carotid endarterectomy.

METHODS

In total, 47 conventional carotid endarterectomy surgeries were performed at our hospital between March 2016 and December 2021. All surgeries were performed under a regional cervical block supplemented with local infiltration anesthesia. All patients were monitored by cerebral oximetry using bilateral near-infrared spectroscopy probes and clinical assessment through communication with the patient (numerical, visual, and verbal) to indicate a selective shunt. Near-infrared spectroscopy values were recorded before and after internal carotid cross-clamping and after declamping. Any decrease in ipsilateral cerebral oximetry-near-infrared spectroscopy values equal to or more than 20% from the pre-clamping baseline reading associated with deterioration in neurological status (hemiparesis, aphasia, or deterioration in level of consciousness) after internal carotid artery cross-clamping was considered an indication for intraluminal carotid shunting.

RESULTS

After internal carotid artery cross-clamping, 5 of 47 patients (10.6%) developed a significant drop in cerebral oxygen saturation associated with obvious clinical assessment deterioration in verbal communication and weakness in contralateral arm power. A Pruitt-Inahara carotid shunt was subsequently inserted, and 42 patients remained stable throughout surgery. The average decline in ipsilateral near-infrared spectroscopy values was 23.8% in patients with clinical deterioration. The average decline was 8.6% in patients who remained stable.

CONCLUSIONS

Monitoring ipsilateral cerebral oximetry using near-infrared spectroscopy is an easy and reliable method for indicating selective shunting during carotid endarterectomy. A 20% decrease in ipsilateral brain tissue oximetry after internal carotid artery cross-clamping provides a reliable cut-off value for selective intraluminal carotid shunting during carotid endarterectomy.

Extracorporeal Off-Pump Antegrade Cerebral Perfusion in Reconstructive Surgery for Type A Aortic Dissection With Cerebral Malperfusion

Introduction Type A aortic dissection (TAAD) is a life-threatening condition that often leads to cerebral malperfusion (CM), a severe complication that can result in permanent neurological damage. Traditionally, a cardiopulmonary bypass (CPB) with selective antegrade cerebral perfusion (ACP) is employed during aortic arch reconstruction to protect cerebral circulation. However, the use of CPB carries inherent higher risks, including embolic events, hypothermia, and interrupted cerebral perfusion, especially in patients with CM. This study evaluates an innovative off-pump extra-corporeal ACP technique using an axillo-axillary shunt to provide uninterrupted bihemispheric cerebral perfusion during branch-first stage total aortic arch replacement (BF-TAR) for TAAD with CM; the shunt depends on cardiac contradiction to transfuse blood from the donor axillary artery to the recipient axillary artery, which then flows to through the carotid and vertebral arteries to the brain. Methods Between 2021 and 2023, 18 patients with TAAD complicated by CM underwent BF-TAR; the novel axillo-axillary shunt technique was employed for ACP because of the risks of ischemic neurologic injury. Outcomes measured included operative mortality, neurological complications, cardiopulmonary bypass times (measured after completion of the branch-first stage), and overall morbidity. Results The axillo-axillary shunt provided stable, continuous ACP in all patients. No new permanent neurological deficits were observed. Five (27.8%) patients experienced transient neurological symptoms such as blurred vision, dizziness, and confusion, which resolved within 48 hours. Operative mortality was 5.6% (1 patient), and minor complications included transitory lower limbs ischemia in 3 patients (16.7%) and deep sternal wound infection in 1 patient (5.6%). All transitory complications were managed by "watchful waiting". The mean CPB time was 145.3 ± 48.6 minutes, while the mean cross-clamp time was 100.6 ± 17.4 minutes, which was better than the average of 227 ± 32 minutes and 147 ± 23 minutes reported in other studies. Postoperative imaging confirmed well-reconstructed aortic arches with no residual malperfusion or graft-related complications. Conclusion The off-pump axillo-axillary shunt technique provides a safe and effective method for maintaining continuous bihemispheric cerebral perfusion during total aortic arch replacement in patients with TAAD complicated by CM. This approach minimizes the risks associated with CPB, including embolic events and interrupted cerebral perfusion while achieving favorable neurological and surgical outcomes. Further studies with larger cohorts and longer follow-ups are warranted to validate the long-term benefits of this innovative technique.

Evaluation of cerebral autoregulation of oxygen by NIRS method during postnatal transition period in term and late preterm newborns without resuscitation requirement

BACKGROUND

Pulse oximetry is commonly used to monitor arterial oxygen saturation and heart rate during the transition period and reference intervals have been determined. However, the effect of the change in arterial oxygen saturation on tissue oxygenation does not seem to be the same. So, a non-invasive method for monitoring cerebral or regional tissue oxygenation will be potentially useful for vulnerable infants. This study aims to evaluate the effectiveness of cerebral autoregulation in the first 10 min after delivery in term and late preterm newborns without resuscitation requirement.

METHODS

Cerebral tissue oxygen saturation was measured in the first 10 min after birth with near-infrared spectroscopy (NIRS) from the left forehead. Peripheral oxygen saturation was measured with pulse oximetry from the right hand and cerebral fractional tissue oxygen extraction was calculated.

RESULTS

Nineteen late preterms and 20 term infants were included in the study. There was no statistically significant difference between median cerebral tissue oxygen saturation and cerebral fractional tissue oxygen extraction values of late preterm and term infants (p < 0.001). There was a strong inverse relationship between cerebral tissue oxygen saturation and cerebral fractional tissue oxygen extraction (p < 0.001).

CONCLUSIONS

In late preterm infants similar to term infants, arterial oxygen saturation and cerebral tissue oxygen saturation increased with time, but inverse reduction of cerebral fractional tissue oxygen extraction showed the presence of an active autoregulation in the brain. This can be interpreted as the ability of the brain to protect itself from hypoxia by regulating oxygen uptake during normal fetal-neonatal transition process. A larger scale multi-center randomized control trial is now needed to further inform practice.

Intraoperative monitoring of the central and peripheral nervous systems: a narrative review

The central and peripheral nervous systems are the primary target organs during anaesthesia. At the time of the inception of the British Journal of Anaesthesia, monitoring of the central nervous system comprised clinical observation, which provided only limited information. During the 100 yr since then, and particularly in the past few decades, significant progress has been made, providing anaesthetists with tools to obtain real-time assessments of cerebral neurophysiology during surgical procedures. In this narrative review article, we discuss the rationale and uses of electroencephalography, evoked potentials, near-infrared spectroscopy, and transcranial Doppler ultrasonography for intraoperative monitoring of the central and peripheral nervous systems.

Trends on Near-Infrared Spectroscopy Associated With Acute Brain Injury in Venoarterial Extracorporeal Membrane Oxygenation

We aimed to determine the association between cerebral regional oxygen saturation (rSO 2 ) trends from cerebral near-infrared spectroscopy (cNIRS) and acute brain injury (ABI) in adult venoarterial extracorporeal membrane oxygenation (VA-ECMO) patients. ABI was defined as intracranial hemorrhage, ischemic stroke, hypoxic ischemic brain injury, or brain death during ECMO. rSO 2 values were collected from left and right cerebral oximetry sensors every hour from ECMO cannulation. Cerebral desaturation was defined as consecutive hours of rSO 2 < 40%. rSO 2 asymmetry was determined by (a) averaging left/right rSO 2 difference over the entire ECMO run; (b) consecutive hours of rSO 2 asymmetry. Sixty-nine VA-ECMO patients (mean age 56 years, 65% male) underwent cNIRS. Eighteen (26%) experienced ABI. When the mean rSO 2 asymmetry was >8% there was significantly increased odds of ABI (aOR = 39.4; 95% CI = 4.1-381.4). Concurrent rSO 2 < 40% and rSO 2 asymmetry >10% for >10 consecutive hours (asymmetric desaturation) was also significantly associated with ABI (aOR = 5.2; 95% CI = 1.2-22.2), but neither criterion alone were. Mean rSO 2 asymmetry>8% exhibited 39% sensitivity and 98% specificity for detecting ABI, with an area under the curve (AUC) of 0.86, and asymmetric desaturation had 33% sensitivity and 88% specificity, with an AUC of 0.72. These trends on NIRS monitoring may help detect ABI in VA-ECMO patients.

Intraoperative application of regional cerebral oxygen saturation monitoring for geriatric patients in China: a survey

Background

Regional cerebral oxygen saturation (rSO2) monitoring is a real-time and non-invasive technique for estimating the balance of regional cerebral oxygen supply and consumption. Despite the growing popularity of this monitoring technique, data regarding outcome benefits remain sparse and contradictory. This study was conducted to explore the popularity and understanding of cerebral oxygen saturation monitoring during anesthesia in geriatric patients.

Methods

An online self-report questionnaire was distributed in March 2021 to various hospitals in China for dissemination to anesthesiologists. Questions surveyed cerebral oximetry equipment and utilization, demographics, and clinical practice of participants.

Results

In total, 447 anesthesiologists responded. Of these, 301 (67.3%) respondents reported that their hospitals were equipped with cerebral oximetry, which 274 anesthesiologists use during anesthesia. A high percentage of anesthesiologists chose to monitor rSO2 during cardiac surgery (77.4%, n = 212) and neurosurgery (40.5%, n = 111). Most anesthesiologists agreed that a 30% reduction from the rSO2 baseline requires intervention to avoid cerebral ischemia, mainly via elevating arterial pressure and fraction of inspired oxygen (FiO2). Of those without cerebral oximetry, 138 of 146 (94.5%) anesthesiologists were willing to monitor rSO2. In addition, 291 respondents believed that cerebral oxygen monitoring would help prevent postoperative cognitive dysfunction.

Conclusion

Our survey indicated that the prevalence of cerebral oximetry remains relatively low, while almost all anesthesiologists expressed their willingness to use rSO2 monitoring in geriatric anesthesia. Heterogeneity in clinical practice was identified, indicating relevant knowledge gaps that should encourage further clinical research to optimize treatment.

Development of a nomogram to predict negative postoperative behavioral changes based on a prospective cohort

BACKGROUND

It is believed that negative postoperative behavioral changes (NPOBC) is associated with negative perioperative outcomes in children. The importance of development of a predictive model of NPOBC was noted. This study aims to identify potential risk factors develop a nomogram to predict NPOBC on postoperative day 3 based on a prospective cohort.

METHODS

A prospective observational study was conducted on children(American Society of Anesthesiologists I ~ III) aged 2 ~ 12 years who underwent selective surgery under general anesthesia between September 2022 and February 2023. The patient's clinical data were analyzed. The method of measuring NPOBC is with the The Posthospital Behaviour Questionnaire (PHBQ), and all of children remained hospitalized at the time of assessment. The enrolled patients were categorized into the NPOBC group and the non-NPOBC group according to if children developed NPOBC on postoperative day 3. Univariate and multivariate logistic regression analyses were performed to identify independent risk factors and develop the nomogram to predict NPOBC. Internal validation was performed using the parametric bootstrapping method.

RESULTS

One hundred ninety-two patients were enrolled in the study, 44.8% (86/192 patients) of children developed NPOBC on postoperative day 3. Univariate and multivariate logistic regression analysis demonstrated that the Pediatric Anesthesia Behavior (PAB) score (OR: 1.23, 95%CI: 1.14-1.33), cerebral desaturation (OR: 1.16, 95%CI: 1.02-1.32), and postoperative pain score (OR: 1.07, 95%CI: 1.02-1.13) were independent predictors for NPOBC on postoperative day 3 (P < 0.05). They were used to develop the prediction model. The calibration curve demonstrated satisfied discrimination and calibration of the prediction model. The model presented with good discriminative ability (area under the receiver operating characteristic curve: 0.762 [95%CI: 0.691-0.833]). The decision curve analysis also revealed the great clinical utility of the nomogram.

CONCLUSION

Based on our prospective observational study, pre-anesthesia patients with higher PAB scores, presence of cerebral desaturation, and higher postoperative pain score were more likely to develop NPOBC on postoperative day 3. We established and validated a nomogram for predicting NPOBC, which could help assess patients individually, identify high-risk groups of NPOBC and improve patient prognosis.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR-2,200,059,776. Registered 11 May 2022.

Reduced regional cerebral oxygen saturation increases risk for emergence delirium in pediatric patients

Objectives

To assess whether decreased regional cerebral oxygen saturation (rScO₂) is associated with the emergence delirium (ED) following general anesthesia in the pediatric population.

Methods

A retrospective observational cohort study was conducted on 113 children (ASA I-III) aged 2-14 years who underwent selective surgery under general anesthesia between 2022-01 and 2022-04. Intraoperatively, the rScO₂ was monitored using a cerebral oximeter. The Pediatric Anesthesia Emergence Delirium (PAED) score was used to evaluate the patients for ED.

Results

The incidence of ED was 31%. Low rScO₂ was reported in 41.6% of patients, who had a higher incidence of ED (P < 0.001) than those who did not experience desaturation. Logistic regression analysis revealed that decreased rScO₂ was significantly associated with incident ED events [odds ratio (OR), 10.77; 95% confidence interval, 3.31-35.05]. Children under 3 years of age had a higher incidence of ED after rScO₂ desaturation during anesthesia compared to older children (OR, 14.17 vs. 4.64).

Conclusion

Intraoperative rScO₂ desaturation significantly increased the incidence of ED following general anesthesia. Monitoring should be enhanced to improve the oxygen balance in vital organs to improve the quality and safety of anesthesia.

Cerebral tissue oximeter suitable for real-time regional oxygen saturation monitoring in multiple clinical settings

Maintenance of adequate blood perfusion and oxygen delivery is essential for cerebral metabolism. Cerebral oximeters based on near-infrared spectroscopy (NIRS) have been used for noninvasive, continuous, real-time monitoring of cerebral oxygen saturation and management of cerebral oxygen adequacy perioperatively and intraoperatively in various clinical situations, such as cardiac surgery, anesthesia, and cerebral auto-regulation. In this study, a portable and modular cerebral tissue oximeter (BRS-1) was designed for real-time detection of regional oxygen saturation over the brain, finger, or other targeted body tissues, as well as for wireless cerebral oxygenation monitoring. The compact and lightweight design of the system makes it easy to use during ambulance transport, in an emergency cart, or in an intensive care unit. The system performance of the BRS-1 oximeter was evaluated and compared with two US FDA-cleared cerebral oximeters during a controlled hypoxia experiment. The results showed that the BRS-1 oximeter can be used for real-time detection of cerebral desaturation with an accuracy similar to the two commercial oximeters. More importantly, the BRS-1 oximeter is capable of capturing cerebral oxygen saturation wirelessly. The BRS-1 cerebral oximeter can provide valuable insights for clinicians for real-time monitoring of cerebral/tissue perfusion and management of patients in prehospital and perioperative periods.

Editorial Special Section on Biomedical Diffuse Optics for the Brain

This special section collects four articles on the application of diffuse optics to measure cerebral hemodynamics and oxygenation. The possibility of using near-infrared light to collect cerebral hemodynamic and metabolic information through the intact scalp and skull was first proposed in the 1970s [1]. Commercial cerebral oximeters were developed in the 1990s, and functional measurements of brain activation, which signaled the birth of functional near-infrared spectroscopy (fNIRS), were first reported in 1993 [2], [3], [4], [5]. Oscillatory cerebral hemodynamics were also investigated in relation to functional and diagnostic applications [6], [7], [8], [9]. Journal special issues were published to celebrate the 20th [10] and 30th [11] anniversaries of fNIRS, and numerous review articles have provided overviews of the field of noninvasive optical measurements of the brain [12], [13], [14], [15].

Traumatic Brain Injury: Intraoperative Management and Intensive Care Unit Multimodality Monitoring

Traumatic brain injury is a devastating event associated with substantial morbidity. Pathophysiology involves the initial trauma, subsequent inflammatory response, and secondary insults, which worsen brain injury severity. Management entails cardiopulmonary stabilization and diagnostic imaging with targeted interventions, such as decompressive hemicraniectomy, intracranial monitors or drains, and pharmacological agents to reduce intracranial pressure. Anesthesia and intensive care requires control of multiple physiologic variables and evidence-based practices to reduce secondary brain injury. Advances in biomedical engineering have enhanced assessments of cerebral oxygenation, pressure, metabolism, blood flow, and autoregulation. Many centers employ multimodality neuromonitoring for targeted therapies with the hope to improve recovery.

Monitoring of Cerebral Oxygen Saturation in Interhospital Transport of Patients Receiving Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) in acute respiratory distress syndrome (ARDS) is used to achieve oxygenation and protect lung ventilation. Near infrared spectroscopy (NIRS) measures cerebral regional tissue oxygenation (rSO 2 ) and may contribute to patient safety during interhospital transport under ECMO support. We evaluated 16 adult ARDS patients undergoing interhospital ECMO transport by measuring cerebral rSO 2 before and after initiation of ECMO support and continuously during transport. To compare peripheral oxygen saturation (SpO 2 ) measurement with rSO 2 , both parameters were analyzed. NIRS monitoring for initiation of ECMO and interhospital transport under ECMO support was feasible, and there was no significant difference in the percentage of achievable valid measurements over time between cerebral rSO 2 (88.4% [95% confidence interval {CI}, 81.3-95.0%]) and standard SpO 2 monitoring 91.7% (95% CI, 86.1-94.2%), p = 0.68. No change in cerebral rSO 2 was observed before 77% (73.5-81%) (median [interquartile range {IQR}]) and after initiation of ECMO support 78% (75-81%), p = 0.2. NIRS for cerebral rSO 2 measurement is feasible during ECMO initiation and interhospital transport. Achievement of valid measurements of cerebral rSO 2 was not superior to SpO 2 . In distinct patients ( e.g. , shock), measurement of cerebral rSO 2 may contribute to improvement of patient safety during interhospital ECMO transport.

Comparison of cerebral oxygen desaturation events between children under general anesthesia and chloral hydrate sedation - a randomized controlled trial

BACKGROUND

During pediatric general anesthesia (GA) and sedation, clinicians aim to maintain physiological parameters within normal ranges. Accordingly, regional cerebral oxygen saturation (rScO2) should not drop below preintervention baselines. Our study compared rScO2 desaturation events in children undergoing GA or chloral hydrate sedation (CHS).

METHODS

Ninety-two children undergoing long auditory assessments were randomly assigned to two study arms: CHS (n = 40) and GA (n = 52). Data of 81 children (mean age 13.8 months, range 1-36 months) were analyzed. In the GA group, we followed a predefined 10 N concept (no fear, no pain, normovolemia, normotension, normocardia, normoxemia, normocapnia, normonatremia, normoglycemia, and normothermia). In this group, ENT surgeons performed minor interventions in 29 patients based on intraprocedural microscopic ear examinations. In the CHS group, recommendations for monitoring and treatment of children undergoing moderate sedation were met. Furthermore, children received a double-barreled nasal oxygen cannula to measure end-tidal carbon dioxide (etCO2) and allow oxygen administration. Chloral hydrate was administered in the parent's presence. Children had no intravenous access which is an advantage of sedation techniques. In both groups, recommendations for fasting were followed and an experienced anesthesiologist was present during the entire procedure. Adverse event (AE) was a decline in cerebral oxygenation to below 50% or below 20% from the baseline for ≥1 min. The primary endpoint was the number of children with AE across the study arms. Secondary variables were: fraction of inspired oxygen (FIO2), oxygen saturation (SpO2), etCO2, systolic and mean blood pressure (BP), and heart rate (HR); these variables were analyzed for their association with drop in rScO2 to below baseline (%drop_rScO2).

RESULTS

The incidence of AE across groups was not different. The analysis of secondary endpoints showed evidence that %drop_rScO2 is more dependent on HR and FIO2 than on BP and etCO2.

CONCLUSIONS

This study highlights the strong association between HR and rScO2 in children aged < 3 years, whereas previous studies had primarily discussed the role of BP and etCO2. Prompt HR correction may result in shorter periods of cerebral desaturation.

TRIAL REGISTRATION

The study was retrospectively registered with the German Clinical Trials Registry (DRKS00024362, 04/02/2021).

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.

The Quantitative Associations Between Near Infrared Spectroscopic Cerebrovascular Metrics and Cerebral Blood Flow: A Scoping Review of the Human and Animal Literature

Cerebral blood flow (CBF) is an important physiologic parameter that is vital for proper cerebral function and recovery. Current widely accepted methods of measuring CBF are cumbersome, invasive, or have poor spatial or temporal resolution. Near infrared spectroscopy (NIRS) based measures of cerebrovascular physiology may provide a means of non-invasively, topographically, and continuously measuring CBF. We performed a systematically conducted scoping review of the available literature examining the quantitative relationship between NIRS-based cerebrovascular metrics and CBF. We found that continuous-wave NIRS (CW-NIRS) was the most examined modality with dynamic contrast enhanced NIRS (DCE-NIRS) being the next most common. Fewer studies assessed diffuse correlation spectroscopy (DCS) and frequency resolved NIRS (FR-NIRS). We did not find studies examining the relationship between time-resolved NIRS (TR-NIRS) based metrics and CBF. Studies were most frequently conducted in humans and animal studies mostly utilized large animal models. The identified studies almost exclusively used a Pearson correlation analysis. Much of the literature supported a positive linear relationship between changes in CW-NIRS based metrics, particularly regional cerebral oxygen saturation (rSO2), and changes in CBF. Linear relationships were also identified between other NIRS based modalities and CBF, however, further validation is needed.

Non-Invasive Intracranial Pressure Monitoring and Its Applicability in Spaceflight

INTRODUCTION: Neuro-ophthalmic findings collectively defined as Spaceflight-Associated Neuro-ocular Syndrome (SANS) are one of the leading health priorities in astronauts engaging in long duration spaceflight or prolonged microgravity exposure. Though multifactorial in etiology, similarities to terrestrial idiopathic intracranial hypertension (IIH) suggest these changes may result from an increase or impairing in intracranial pressure (ICP). Finding a portable, accessible, and reliable method of monitoring ICP is, therefore, crucial in long duration spaceflight. A review of recent literature was conducted on the biomedical literature search engine PubMed using the search term “non-invasive intracranial pressure”. Studies investigating accuracy of noninvasive and portable methods were assessed. The search retrieved different methods that were subsequently grouped by approach and technique. The majority of publications included the use of ultrasound-based methods with variable accuracies. One of which, noninvasive ICP estimation by optical nerve sheath diameter measurement (nICP_ONSD), presented the highest statistical correlation and prediction values to invasive ICP, with area under the curve (AUC) ranging from 0.75 to 0.964. One study even considers a combination of ONSD with transcranial Doppler (TCD) for an even higher performance. Other methods, such as near-infrared spectroscopy (NIRS), show positive and promising results [good statistical correlation with invasive techniques when measuring cerebral perfusion pressure (CPP): r = 0.83]. However, for its accessibility, portability, and accuracy, ONSD seems to present itself as the up to date, most reliable, noninvasive ICP surrogate and a valuable spaceflight asset.Félix H, Santos Oliveira E. Non-invasive intracranial pressure monitoring and its applicability in spaceflight. Aerosp Med Hum Perform. 2022; 93(6):517–531.

Cerebral oxygen desaturation events during and functional outcomes after prehospital anaesthesia: A prospective pilot study

Background

During prehospital anaesthesia, oxygen delivery to the brain might be inadequate to match the oxygen consumption, with unknown long‐term functional outcomes. We aimed to evaluate the feasibility of monitoring cerebral oxygenation during prehospital anaesthesia and determining the long‐term outcomes.

Methods

We performed a prospective observational feasibility study in two helicopter emergency medical services units. Frontal lobe regional oxygen saturation (rSO₂) of adult patients undergoing prehospital anaesthesia was monitored with near‐infrared spectroscopy (NIRS) by a Nonin H500 oximeter. The outcome was evaluated with a modified Rankin Scale (mRS) at 30 days and 1 year. Health‐related quality of life (HRQoL) was measured with a 15D instrument at 1 year.

Results

Of 101 patients enrolled, 83 were included. The mean baseline rSO₂ was 79% (73–84). Desaturation for at least 5 min to rSO₂ below 50% or a decrease of 10% from baseline occurred in four (5%, 95% CI 2%–12%) and 19 (23%, 95% CI 15–93) patients. At 1 year, 32 patients (53%, 95% CI 41–65) achieved favourable neurological outcomes. The median 15D score was 0.889 (Q1–Q3, 0.796–0.970).

Conclusion

Monitoring cerebral oxygenation with a hand‐held oximeter during prehospital anaesthesia and collecting data on functional outcomes and HRQoL are feasible. Only half of the patients achieved a favourable functional outcome. The effects of cerebral oxygenation on outcomes during prehospital critical care need to be assessed in future studies.

Non-invasive intracranial pressure assessment using shear-wave elastography in neuro-critical care patients

OBJECTIVE

To determine if Young's modulus of the optic nerve (ON) structure as measured by shear-wave elastography can suggest changes in intracranial pressure (ICP) in neuro-critical care patients.

MATERIALS AND METHODS

Thirty-one healthy volunteers and twenty-two neuro-critical care patients were enrolled. ON sheath (ONS) diameter (ONSD) values and Young's modulus measurements of volunteers were collected in a calm state and during a Valsalva maneuver (VM). Ultrasound measurements and ICP values of patients were collected on operation day and at 24 and 48 h after the operation; measurements were thereafter assigned to three groups: severely elevated (ICP greater than 22 mmHg), mildly elevated (ICP = 14-22 mmHg), and normal (ICP ≤ 13 mmHg).

RESULTS

ONSD and Young's modulus for the ON and ONS of volunteers during VM were higher than those in the calm state (all P < 0.001). In contrast to ONSD, Young's modulus for ON and ONS did not correlate with age, body mass index, or sex. The best cutoff values of Young's modulus for ON for predicting elevated and severely elevated ICP were 16.67 kPa and 22.74 kPa, respectively. Accordingly, the sensitivity values were 96.7% and 88.9%, and the specificity values were 86.1% and 73.7%, which had the same diagnostic performance as ONSD.

CONCLUSION

Young's modulus of the ON accurately reflects changes in ICP. It is not confounded by age, sex, or body mass index compared to ONSD.

The Predictive Power of Near-Infrared Spectroscopy in Improving Cognitive Problems in Patients Undergoing Brain Surgeries: A Systematic Review

One of the main objectives in neurosurgical procedures is the prevention of cerebral ischemia and hypoxia leading to secondary brain injury. Different methods for early detection of intraoperative cerebral ischemia and hypoxia have been used. Near-infrared spectroscopy (NIRS) is a simple, non-invasive method for monitoring cerebral oxygenation increasingly used today. The aim of this study was to systematically review the brain monitoring with NIRS in neurosurgery. The search process resulted in the detection of 324 articles using valid keywords on the electronic databases, including Embase, PubMed, Scopus, Web of Science, and Cochrane Library. Subsequently, the full texts of 34 studies were reviewed, and finally 11 articles (seven prospective studies, three retrospective studies, and one randomized controlled trial) published from 2005 to 2020 were identified as eligible for systematic review. Meta-analysis was not possible due to high heterogeneity in neurological and neurosurgical conditions of patients, expression of different clinical outcomes, and different standard reference tests in the studies reviewed. The results showed that NIRS is a non-invasive cerebral oximetry that provides continuous and measurable cerebral oxygenation information and can be used in a variety of clinical settings.

Review of studies on dynamic cerebral autoregulation in the acute phase of stroke and the relationship with clinical outcome

Acute stroke is associated with high morbidity and mortality. In the last decades, new therapies have been investigated with the aim of improving clinical outcomes in the acute phase post stroke onset. However, despite such advances, a large number of patients do not demonstrate improvement, furthermore, some unfortunately deteriorate. Thus, there is a need for additional treatments targeted to the individual patient. A potential therapeutic target is interventions to optimize cerebral perfusion guided by cerebral hemodynamic parameters such as dynamic cerebral autoregulation (dCA). This narrative led to the development of the INFOMATAS (Identifying New targets FOr Management And Therapy in Acute Stroke) project, designed to foster interventions directed towards understanding and improving hemodynamic aspects of the cerebral circulation in acute cerebrovascular disease states. This comprehensive review aims to summarize relevant studies on assessing dCA in patients suffering acute ischemic stroke, intracerebral haemorrhage, and subarachnoid haemorrhage. The review will provide to the reader the most consistent findings, the inconsistent findings which still need to be explored further and discuss the main limitations of these studies. This will allow for the creation of a research agenda for the use of bedside dCA information for prognostication and targeted perfusion interventions.

The use of cerebral oximetry in cardiac surgery: A systematic review and meta-analysis of randomized controlled trials

High prevalence of cerebral desaturation is associated with postoperative neurological complications in cardiac surgery. However, the evidence use of cerebral oximetry by correcting cerebral desaturation in the reduction of postoperative complications remains uncertain in the literature. This systematic review and meta-analysis aimed to examine the effect of cerebral oximetry on the incidence of postoperative cognitive dysfunction in cardiac surgery. Databases of MEDLINE, EMBASE, and CENTRAL were searched from their inception until April 2021. All randomized controlled trials comparing cerebral oximetry and blinded/no cerebral oximetry in adult patients undergoing cardiac surgery were included. Observational studies, case series, and case reports were excluded. A total of 14 trials (n = 2,033) were included in this review. Our pooled data demonstrated that patients with cerebral oximetry were associated with a lower incidence of postoperative cognitive dysfunction than the control group (studies = 4, n = 609, odds ratio [OR]: 0.15, 95% confidence interval [CI]: 0.04 to 0.54, P = 0.003, I² = 88%; certainty of evidence = very low). In terms of postoperative delirium (OR: 0.75, 95%CI: 0.50-1.14, P = 0.18, I² = 0%; certainty of evidence = low) and postoperative stroke (OR: 0.81 95%CI: 0.37-1.80, P = 0.61, I² = 0%; certainty of evidence = high), no significant differences (P > 0.05) were reported between the cerebral oximetry and control groups. In this meta-analysis, the use of cerebral oximetry monitoring in cardiac surgery demonstrated a lower incidence of postoperative cognitive dysfunction. However, this finding must be interpreted with caution due to the low level of evidence, high degree of heterogeneity, lack of standardized cognitive assessments, and cerebral desaturation interventions.

Role of Near-infrared Spectroscopy in the Diagnosis and Assessment of Necrotizing Enterocolitis

Near-infrared spectroscopy (NIRS) is a noninvasive, bedside diagnostic tool that could assist in the early diagnosis of necrotizing enterocolitis (NEC) in preterm neonates. NIRS is a safe and effective clinical tool in the neonatal intensive care unit to detect abnormal alterations in tissue perfusion and oxygenation. In addition, NIRS could also detect the complications of NEC, such as bowel necrosis and perforation. NEC is the most common gastrointestinal complication associated with preterm birth and critically ill infants. It is observed in 6-10% of preterm neonates, weighing below 1500 g, leading to considerable morbidity, mortality, and healthcare cost burden. The mortality rate ranges from 20 to 30%, highest in NEC infants undergoing surgery. NIRS is a promising diagnostic modality that could facilitate the early diagnosis of NEC and early detection of complications alone or with the imaging modalities.

Could Near Infrared Spectroscopy (NIRS) be the new weapon in our fight against Necrotising Enterocolitis?

There is no ideal single gut tissue or inflammatory biomarker available to help to try and identify Necrotising Enterocolitis (NEC) before its clinical onset. Neonatologists are all too familiar with the devastating consequences of NEC, and despite many advances in neonatal care the mortality and morbidity associated with NEC remains significant. In this article we review Near Infrared Spectroscopy (NIRS) as a method of measuring regional gut tissue oxygenation. We discuss its current and potential future applications, including considering its effectiveness as a possible new weapon in the early identification of NEC.

Performance Assessment of a Commercial Continuous-Wave Near-Infrared Spectroscopy Tissue Oximeter for Suitability for Use in an International, Multi-Center Clinical Trial

Despite the wide range of clinical and research applications, the reliability of the absolute oxygenation measurements of continuous wave near-infrared spectroscopy sensors is often questioned, partially due to issues of standardization. In this study, we have compared the performances of 13 units of a continuous wave near-infrared spectroscopy device (PortaMon, Artinis Medical Systems, NL) to test their suitability for being used in the HEMOCOVID-19 clinical trial in 10 medical centers around the world. Detailed phantom and in vivo tests were employed to measure the precision and reproducibility of measurements of local blood oxygen saturation and total hemoglobin concentration under different conditions: for different devices used, different operators, for probe repositioning over the same location, and over time (hours/days/months). We have detected systematic differences between devices when measuring phantoms (inter-device variability, <4%), which were larger than the intra-device variability (<1%). This intrinsic variability is in addition to the variability during in vivo measurements on the forearm muscle resulting from errors in probe positioning and intrinsic physiological noise (<9%), which was also larger than the inter-device differences (<3%) during the same test. Lastly, we have tested the reproducibility of the protocol of the HEMOCOVID-19 clinical trial; that is, forearm muscle oxygenation monitoring during vascular occlusion tests over days. Overall, our conclusion is that these devices can be used in multi-center trials but care must be taken to characterize, follow-up, and statistically account for inter-device variability.

The Use of Cerebral Oximetry in Surgery: A Systematic Review and Meta-analysis of Randomized Controlled Trials

OBJECTIVE

The evidence on the use of cerebral oximetry during surgery to minimize postoperative neurologic complications remains uncertain in the literature. The present authors aimed to assess the value of cerebral oximetry in the prevention of postoperative cognitive dysfunction, postoperative delirium, and postoperative stroke in adults undergoing surgery.

DESIGN

A systematic review and meta-analysis.

SETTING

The surgery room.

PARTICIPANTS

Adult patients (ages ≥18 years) undergoing surgery.

INTERVENTIONS

Cerebral oximetry monitoring.

MEASUREMENTS AND MAIN RESULTS

Databases of Ovid MEDLINE, Ovid EMBASE, and CENTRAL were systematically searched from their inception until December 2020 for randomized controlled trials comparing cerebral oximetry monitoring with either blinded or no cerebral oximetry monitoring in adults undergoing surgery. Observational studies, case reports, and case series were excluded. Seventeen studies (n = 2,120 patients) were included for quantitative meta-analysis. Patients who were randomized to cerebral oximetry monitoring had a lower incidence of postoperative cognitive dysfunction (studies = seven, n = 969, odds ratio [OR] 0.23, 95% confidence interval [CI] 0.11-0.48, p = 0.0001; evidence = very low). However, no significant differences were observed in the incidence of postoperative delirium (studies = five, n = 716, OR 0.81, 95% CI 0.53-1.25, p = 0.35; evidence = high), and postoperative stroke (studies = seven, n = 1,087, OR 0.72, 95% CI 0.30-1.69, p = 0.45; evidence = moderate).

CONCLUSION

Adult patients with cerebral oximetry monitoring were associated with a significant reduction of postoperative cognitive dysfunction. However, given the low certainty of evidence and substantial heterogeneity, more randomized controlled trials using standardized assessment tools for postoperative cognitive dysfunction and interventions of correcting cerebral desaturation are warranted to improve the certainty of evidence and homogeneity.

Cerebral oximetry monitoring in non-intubated patients undergoing endoscopic retrograde cholangiopancreatography under propofol-induced sedation: a prospective observational study

Background

Prolonged propofol-induced deep sedation increases the risk for sedation-related complications. Cerebral oximetry enables prompt assessment of tissue oxygenation by demonstrating the regional hemoglobin oxygen saturation (rSO₂) of the cerebral cortex. This study aimed to: evaluate cerebral oxygenation under deep sedation during an endoscopic retrograde cholangiopancreatography (ERCP) procedure; determine the cerebral desaturation event (CDE) rate; and assess the predictive capacity of CDEs for sedation-related complications.

Methods

All consecutive patients who underwent ERCP between September and December 2019 were included prospectively. Propofol monotherapy was used and sedation level was assessed using the bispectral index (BIS). The target level of sedation was deep sedation, defined by BIS values 40-60. Participants were monitored with arterial blood gas analysis and INVOS 5100C cerebral oximeter. RSO₂ values were registered prior to sedation (baseline value), every 5 min during the sedation period and at recovery of consciousness. BIS values were recorded simultaneously. CDE was defined as a drop >10% from individual baseline rSO₂.

Results

Sixty patients were enrolled. Mean baseline rSO₂ was 65.1% and BIS values ranged from 18-85. No significant correlation was observed between mean rSO₂ measurements and mean BIS values throughout the recordings (P = 0.193). Data from patients aged ≥65 years were analyzed separately and the results were similar. The CDE rate was 2.7%, but no CDE was associated with clinical manifestations. Twelve sedation-related complications occurred without the presence of cerebral desaturation.

Conclusion

Cerebral oxygenation remained independent of changes in sedation depth and cerebral oximetry monitoring did not detect complications earlier than standard monitors.

A Review of Monitoring Methods for Cerebral Blood Oxygen Saturation

In recent years, cerebral blood oxygen saturation has become a key indicator during the perioperative period. Cerebral blood oxygen saturation monitoring is conducive to the early diagnosis and treatment of cerebral ischemia and hypoxia. The present study discusses the three most extensively used clinical methods for cerebral blood oxygen saturation monitoring from different aspects: working principles, relevant parameters, current situations of research, commonly used equipment, and relative advantages of different methods. Furthermore, through comprehensive comparisons of the methods, we find that near-infrared spectroscopy (NIRS) technology has significant potentials and broad applications prospects in terms of cerebral oxygen saturation monitoring. Despite the current NIRS technology, the only bedside non-invasive cerebral oxygen saturation monitoring technology, still has many defects, it is more in line with the future development trend in the field of medical and health, and will become the main method gradually.

From head micro-motions towards CSF dynamics and non-invasive intracranial pressure monitoring

Continuous monitoring of the intracranial pressure (ICP) is essential in neurocritical care. There are a variety of ICP monitoring systems currently available, with the intraventricular fluid filled catheter transducer currently representing the “gold standard”. As the placement of catheters is associated with the attendant risk of infection, hematoma formation, and seizures, there is a need for a reliable, non-invasive alternative. In the present study we suggest a unique theoretical framework based on differential geometry invariants of cranial micro-motions with the potential for continuous non-invasive ICP monitoring in conservative traumatic brain injury (TBI) treatment. As a proof of this concept, we have developed a pillow with embedded mechanical sensors and collected an extensive dataset (> 550 h on 24 TBI coma patients) of cranial micro-motions and the reference intraparenchymal ICP. From the multidimensional pulsatile curve we calculated the first Cartan curvature and constructed a ”fingerprint” image (Cartan map) associated with the cerebrospinal fluid (CSF) dynamics. The Cartan map features maxima bands corresponding to a pressure wave reflection corresponding to a detectable skull tremble. We give evidence for a statistically significant and patient-independent correlation between skull micro-motions and ICP time derivative. Our unique differential geometry-based method yields a broader and global perspective on intracranial CSF dynamics compared to rather local catheter-based measurement and has the potential for wider applications.

Cerebral Autoregulation in Ischemic Stroke: From Pathophysiology to Clinical Concepts

Ischemic stroke (IS) is one of the most impacting diseases in the world. In the last decades, new therapies have been introduced to improve outcomes after IS, most of them aiming for recanalization of the occluded vessel. However, despite this advance, there are still a large number of patients that remain disabled. One interesting possible therapeutic approach would be interventions guided by cerebral hemodynamic parameters such as dynamic cerebral autoregulation (dCA). Supportive hemodynamic therapies aiming to optimize perfusion in the ischemic area could protect the brain and may even extend the therapeutic window for reperfusion therapies. However, the knowledge of how to implement these therapies in the complex pathophysiology of brain ischemia is challenging and still not fully understood. This comprehensive review will focus on the state of the art in this promising area with emphasis on the following aspects: (1) pathophysiology of CA in the ischemic process; (2) methodology used to evaluate CA in IS; (3) CA studies in IS patients; (4) potential non-reperfusion therapies for IS patients based on the CA concept; and (5) the impact of common IS-associated comorbidities and phenotype on CA status. The review also points to the gaps existing in the current research to be further explored in future trials.

Combined mental task and metaboreflex impair cerebral oxygenation in patients with type 2 diabetes mellitus

Cardiovascular regulation is altered by type 2 diabetes mellitus (DM2), producing an abnormal response to muscle metaboreflex. During physical exercise, cerebral blood flow is impaired in patients with DM2, and this phenomenon may reduce cerebral oxygenation (COX). We hypothesized that the simultaneous execution of a mental task (MT) and metaboreflex activation would reduce COX in patients with DM2. Thirteen individuals suffering from DM2 (6 women) and 13 normal age-matched controls (CTL, 6 women) participated in this study. They underwent five different tests, each lasting 12 min: postexercise muscle ischemia (PEMI) to activate the metaboreflex, control exercise recovery (CER), PEMI + MT, CER + MT, and MT alone. COX was evaluated using near-infrared spectroscopy with sensors applied to the forehead. Central hemodynamics was assessed using impedance cardiography. We found that when MT was superimposed on the PEMI-induced metaboreflex, patients with DM2 could not increase COX to the same extent reached by the CTL group (101.13% ± 1.08% vs. 104.23% ± 2.51%, P < 0.05). Moreover, patients with DM2 had higher mean blood pressure and systemic vascular resistance as well as lower stroke volume and cardiac output levels compared with the CTL group, throughout our experiments. It was concluded that patients with DM2 had reduced capacity to enhance COX when undertaking an MT during metaboreflex. Results also confirm that patients with DM2 had dysregulated hemodynamics during metaboreflex, with exaggerated blood pressure response and vasoconstriction. This may have implications for these patients' lack of inclination to exercise.

Validation of a Novel NeurOs Cerebral Oximetry Monitor Against the INVOS Monitor During Cardiac Surgery

OBJECTIVES

To compare the performance of a novel NeurOs cerebral oximetry monitor against the INVOS monitor during the entire intraoperative phase of cardiac surgery, including periods of known fluctuation in brain oxygenation, such as preoxygenation, induction, cannulation, and cardiopulmonary bypass.

DESIGN

This study was a prospective, nonrandomized, healthcare-provider and outcome-assessor blinded study.

SETTING

Tertiary care university hospital; single institutional study.

PARTICIPANTS

Twenty-three patients who underwent cardiac surgery with cardiopulmonary bypass.

INTERVENTIONS

Both self-adhesive INVOS sensors and the assembled NeurOs sensors were placed accordingly when the patient arrived in the operating room.

MEASUREMENTS AND MAIN RESULTS

Ten out of 13 cases under the normal mode and eight out of the 10 cases under the high- sensitivity mode showed significant correlations between the NeurOs and INVOS groups (p < 0.05, r value from 0.24-0.88). When all cases were combined, NeurOs demonstrated significant correlation with INVOS (r = 0.5, 95% confidence interval [CI] 0.44-0.56, p < 0.01 for normal mode; r = 0.69, 95% CI 0.64 to 0.74, p < 0.01 for high-sensitivity mode) in both modes. To evaluate the data diversity, the authors performed a cluster analysis and found much less variation existed in the NeurOs normal mode when compared with INVOS (standard deviation [SD] 16.6% in INVOS, 4% in NeurOs normal mode) but similar patterns in the high-sensitivity mode (SD 17.6% in INVOS, 15.2% in NeurOs high-sensitivity mode). Bland-Altman plot analysis showed that most of the data fell between ± 1.96 SD lines, which demonstrated good consistency between these two methods under both modes of NeurOs (-28.8 to 30.8 in the normal mode; -36.6 to 32.7 in high-sensitivity mode). In the normal mode of NeurOs monitoring, receiver operating characteristic analysis suggested a 2% cutoff point was most optimal from the baseline for detecting hyperoxia (sensitivity 73%; specificity 66%) and minus 1% (sensitivity 66%; specificity 67%) for detecting hypoxia. Whereas in the high-sensitivity mode, the optimal cutoff point was 3% from baseline for detecting hyperoxia (sensitivity 75%; specificity 68%), and minus 3% for detecting hypoxia (sensitivity 90%; specificity 45%).

CONCLUSIONS

In conclusion, the novel NeurOs system was found to correlate with INVOS cerebral oximetry measurements during cardiac surgery.

Current state of noninvasive, continuous monitoring modalities in pediatric anesthesiology

PURPOSE OF REVIEW

The last decades, anesthesia has become safer, partly due to developments in monitoring. Advanced monitoring of children under anesthesia is challenging, due to lack of evidence, validity and size constraints. Most measured parameters are proxies for end organ function, in which an anesthesiologist is actually interested. Ideally, monitoring should be continuous, noninvasive and accurate. This present review summarizes the current literature on noninvasive monitoring in noncardiac pediatric anesthesia.

RECENT FINDINGS

For cardiac output (CO) monitoring, bolus thermodilution is still considered the gold standard. New noninvasive techniques based on bioimpedance and pulse contour analysis are promising, but require more refining in accuracy of CO values in children. Near-infrared spectroscopy is most commonly used in cardiac surgery despite there being no consensus on safety margins. Its place in noncardiac anesthesia has yet to be determined. Transcutaneous measurements of blood gases are used mainly in the neonatal intensive care unit, and is finding its way to the pediatric operation theatre. Especially CO2 measurements are accurate and useful.

SUMMARY

New techniques are available to assess a child's hemodynamic and respiratory status while under anesthesia. These new monitors can be used as complementary tools together with standard monitoring in children, to further improve perioperative safety.

Effects of low- and high-pressure carbon dioxide pneumoperitoneum on intracranial pressure during laparoscopic cholecystectomy

BACKGROUND

Laparoscopic surgeries are a risk factor for raised intracranial **pressure and neurological complications. Even though rare, the consequences may be severe.

METHODS

One hundred and one patients of laparoscopic cholecystectomy were enrolled and were randomized into two groups: low-pressure 8 mm Hg (Group A) and high-pressure 14 mm Hg (Group B) carbon dioxide pneumoperitoneum during surgery. Fifty patients were in group A and 51 patients were in group B. Intracranial pressure was measured by measuring the optic nerve sheath diameter (ONSD) using ultrasound examination. Baseline ONSD was recorded followed by ONSD recording at various intervals: at the induction of anesthesia; 30 min, 45 min, at the end of surgery; and 30 min post surgery.

RESULTS

The groups were comparable in terms of demographics and comorbidities. The mean age of group A was 45 years and for group B it was 45.75 years. Most common indication for surgery was symptomatic gall stone disease. Baseline ONSD in group A was 0.427 ± 0.0459 mm, whereas it was 0.412 ± 0.0412 mm in group B. There was a significant rise of ONSD (p < 0.05) 30 min after induction of pneumoperitoneum and up to 30 min post anesthesia. In the low-pressure group 7 (14%) patients had a significant rise of ICP, whereas in the high-pressure group 20 (39%) patients had a significant rise of ICP (p < 0.05).

CONCLUSIONS

High-pressure pneumoperitoneum causes significant rise in intracranial pressure in comparison to low-pressure pneumoperitoneum during laparoscopic cholecystectomy, which can be monitored by ONSD measurement by ultrasound examination and is totally non-invasive.

Laser speckle contrast imaging of forehead cutaneous blood flow during carotid endarterectomy as a potential non-invasive method for surrogate monitoring of cerebral perfusion

Monitoring cerebral perfusion is important for goal-directed anesthesia. Taking advantage of the supply of the supraorbital region and Glabella from the internal carotid artery (ICA), we evaluated changes in cutaneous blood flow using laser speckle contrast imagining (LSCI) as a potential method for indirect real-time monitoring of cerebral perfusion. Nine patients (8 men, mean age 70 years) underwent eversion carotid endarterectomy under local anesthesia. Cutaneous blood flow of the forehead was monitored using LSCI. During clamping of the common carotid artery (CCA), ipsilateral supraorbital region and Glabellas cutaneous blood flow dropped from 334 ± 135 to 221 ± 109 AU (p = 0.023) (AU: arbitrary flux units) and from 384 ± 151 to 276 ± 107 AU (p = 0.023), respectively, whilst the contralateral supraorbital region cutaneous blood flow remained unchanged. The supraorbital cutaneous blood flow did not change significantly following reperfusion of the external carotid artery (ECA) (221 ± 109 to 281 ± 154 AU; p = 0.175) and ICA (281 ± 154 to 310 ± 184 AU; p = 01). A comparable trend for Glabella followed ECA (276 ± 107 to 342 ± 170 AU; p = 0.404) and ICA (342 ± 170 to 352 ± 191 AU; p = 01) reperfusion. In patients undergoing carotid endarterectomy under local anesthesia, LSCI of the supraorbital and Glabella regions reflected clamping of the CCA but did not distinguish reperfusion of the ICA from that of the ECA.

Validation of Noninvasive Absolute Intracranial Pressure Measurements in Traumatic Brain Injury and Intracranial Hemorrhage

BACKGROUND

Increased intracranial pressure (ICP) causes secondary damage in traumatic brain injury (TBI), and intracranial hemorrhage (ICH). Current methods of ICP monitoring require surgery and carry risks of complications.

OBJECTIVE

To validate a new instrument for noninvasive ICP measurement by comparing values obtained from noninvasive measurements to those from commercial implantable devices through this pilot study.

METHODS

The ophthalmic artery (OA) served as a natural ICP sensor. ICP measurements obtained using noninvasive, self-calibrating device utilizing Doppler ultrasound to evaluate OA flow were compared to standard implantable ICP measurement probes.

RESULTS

A total of 78 simultaneous, paired, invasive, and noninvasive ICP measurements were obtained in 11 ICU patients over a 17-mo period with the diagnosis of TBI, SAH, or ICH. A total of 24 paired data points were initially excluded because of questions about data independence. Analysis of variance was performed first on the 54 remaining data points and then on the entire set of 78 data points. There was no difference between the 2 groups nor was there any correlation between type of sensor and the patient (F[10, 43] = 1.516, P = .167), or the accuracy and precision of noninvasive ICP measurements (F[1, 43] = 0.511, P = .479). Accuracy was [-1.130; 0.539] mm Hg (CL = 95%). Patient-specific calibration was not needed. Standard deviation (precision) was [1.632; 2.396] mm Hg (CL = 95%). No adverse events were encountered.

CONCLUSION

This pilot study revealed no significant differences between invasive and noninvasive ICP measurements (P < .05), suggesting that noninvasive ICP measurements obtained by this method are comparable and reliable.

Review: pathophysiology of intracranial hypertension and noninvasive intracranial pressure monitoring

Measurement of intracranial pressure (ICP) is crucial in the management of many neurological conditions. However, due to the invasiveness, high cost, and required expertise of available ICP monitoring techniques, many patients who could benefit from ICP monitoring do not receive it. As a result, there has been a substantial effort to explore and develop novel noninvasive ICP monitoring techniques to improve the overall clinical care of patients who may be suffering from ICP disorders. This review attempts to summarize the general pathophysiology of ICP, discuss the importance and current state of ICP monitoring, and describe the many methods that have been proposed for noninvasive ICP monitoring. These noninvasive methods can be broken down into four major categories: fluid dynamic, otic, ophthalmic, and electrophysiologic. Each category is discussed in detail along with its associated techniques and their advantages, disadvantages, and reported accuracy. A particular emphasis in this review will be dedicated to methods based on the use of transcranial Doppler ultrasound. At present, it appears that the available noninvasive methods are either not sufficiently accurate, reliable, or robust enough for widespread clinical adoption or require additional independent validation. However, several methods appear promising and through additional study and clinical validation, could eventually make their way into clinical practice.

Effect of Combined Mental Task and Metaboreflex Activation on Hemodynamics and Cerebral Oxygenation in Patients With Metabolic Syndrome

Objective: The hemodynamic response to muscle metaboreflex has been reported to be significantly altered by metabolic syndrome (MS), with exaggerated systemic vascular resistance (SVR) increments and reduced cardiac output (CO) in comparison to healthy controls (CTLs). Moreover, patients with metabolic disorders, such as type 2 diabetes, have proven to have impaired cerebral blood flow in response to exercise. Thus, we hypothesized that contemporary mental task (MT) and metaboreflex would result in reduced cerebral oxygenation (COX) in these patients.

Methods: Thirteen MS patients (five women) and 14 normal age-matched CTLs (six women) were enrolled in this study. All the participants underwent five different tests, each lasting 12 min: post-exercise muscle ischemia (PEMI) to activate the metaboreflex, control exercise recovery (CER), PEMI + MT, CER + MT, and MT alone. Cerebral oxygenation was evaluated using near-infrared spectroscopy with sensors applied to the forehead. Hemodynamics were measured using impedance cardiography.

Results: The main results show that MS patients had higher SVR and lower CO levels compared to the CTL group during metaboreflex activation. Stroke volume and ventricular filling and emptying rates were also significantly reduced. Moreover, when MT was added to PEMI, COX was significantly increased in the CTL group with respect to the baseline (103.46 ± 3.14%), whereas this capacity was reduced in MS patients (102.37 ± 2.46%).

Conclusion: It was concluded that (1) patients with MS showed hemodynamic dysregulation during the metaboreflex, with exaggerated vasoconstriction and that (2) as compared to CTL, MS patients had reduced capacity to enhance COX when an MT superimposed the metaboreflex.

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.

Measuring intracranial pressure by invasive, less invasive or non-invasive means: limitations and avenues for improvement

Sixty years have passed since neurosurgeon Nils Lundberg presented his thesis about intracranial pressure (ICP) monitoring, which represents a milestone for its clinical introduction. Monitoring of ICP has since become a clinical routine worldwide, and today represents a cornerstone in surveillance of patients with acute brain injury or disease, and a diagnostic of individuals with chronic neurological disease. There is, however, controversy regarding indications, clinical usefulness and the clinical role of the various ICP scores. In this paper, we critically review limitations and weaknesses with the current ICP measurement approaches for invasive, less invasive and non-invasive ICP monitoring. While risk related to the invasiveness of ICP monitoring is extensively covered in the literature, we highlight other limitations in current ICP measurement technologies, including limited ICP source signal quality control, shifts and drifts in zero pressure reference level, affecting mean ICP scores and mean ICP-derived indices. Control of the quality of the ICP source signal is particularly important for non-invasive and less invasive ICP measurements. We conclude that we need more focus on mitigation of the current limitations of today's ICP modalities if we are to improve the clinical utility of ICP monitoring.

Regional perfusion monitoring in shock

PURPOSE OF REVIEW

Despite restoration of adequate systemic blood flow in patients with shock, single organs may remain hypoperfused. In this review, we summarize the results of a literature research on methods to monitor single organ perfusion in shock. We focused on methods to measure heart, brain, kidney, and/or visceral organ perfusion. Furthermore, only methods that can be used in real-time and at the bedside were included.

RECENT FINDINGS

We identified studies on physical examination techniques, electrocardiography, echocardiography, contrast-enhanced ultrasound, near-infrared spectroscopy, and Doppler sonography to assess single organ perfusion.

SUMMARY

Physical examination techniques have a reasonable negative predictive value to exclude single organ hypoperfusion but are nonspecific to detect it. Technical methods to indirectly measure myocardial perfusion include ECG and echocardiography. Contrast-enhanced ultrasound can quantify myocardial perfusion but has so far only been used to detect regional myocardial hypoperfusion. Near-infrared spectroscopy and transcranial Doppler sonography can be used to assess cerebral perfusion and determine autoregulation thresholds of the brain. Both Doppler and contrast-enhanced ultrasound techniques are novel methods to evaluate renal and visceral organ perfusion. A key limitation of most techniques is the inability to determine adequacy of organ blood flow to meet the organs' metabolic demands.

Lack of agreement between optimal mean arterial pressure determination using pressure reactivity index versus cerebral oximetry index in hypoxic ischemic brain injury after cardiac arrest

INTRODUCTION

Invasive monitoring of cerebral autoregulation using the pressure reactivity index (PRx) allows for the determination of optimal mean arterial pressure (MAP_OPT) in hypoxic ischemic brain injury (HIBI) patients following cardiac arrest. However, the utility of non-invasive surrogates to determine MAP_OPT has not been addressed. We aimed to determine the agreement between PRx-derived MAP_OPT versus MAP_OPT determined by the near-infrared spectroscopy (NIRS) based cerebral oximetry index (COx).

METHODS

Ten HIBI patients were enrolled. PRx-derived MAP_OPT, lower (LLA) and upper limits of autoregulation (ULA) were compared against COx-derived MAP_OPT, LLA and ULA. Multimodal neuromonitoring included mean arterial pressure, intracranial pressure, brain tissue oxygenation, jugular venous oxygen saturation, and NIRS-derived regional cerebral oxygen saturation.

RESULTS

Repeated measures Bland-Altman plots demonstrated limited agreement between MAP_OPT derived from COx and PRx (mean bias: 1.4 mmHg; upper limit of agreement: 25.9 mmHg; lower limit of agreement: -23.0 mmHg). Similarly, there was limited agreement between the absolute values of PRx and COx. Mean bias was 0.26 and the upper and lower limits of agreement were 1.05 and -0.53, respectively. Systematic bias was apparent, whereby at low PRx values COx overestimated PRx and at high PRx values, COx underestimated PRx. COx was limited in its ability to determine impaired autoregulation defined by PRx (receiver operator characteristic area under the curve was 0.488).

CONCLUSION

Collectively, we demonstrate that COx-based determination of MAP_OPT lacks agreement with MAP_OPT derived from PRx. Further research must be done to evaluate the physiologic and clinical efficacy of PRx derived MAP_OPT in HIBI.

Association between Cerebral Oxygen Saturation with Outcome in Cardiac Surgery: Brain as an Index Organ

While both baseline regional cerebral oxygen saturation (rSO₂) and intraoperative rSO₂ decreases have prognostic importance in cardiac surgery, evidence is limited in patients who received interventions to correct rSO₂ decreases. The primary aim was to examine the association between rSO₂ values (both baseline rSO₂ and intraoperative decrease in rSO₂) with the composite of morbidity endpoints. We retrospectively analyzed 356 cardiac surgical patients having continuously recorded data of intraoperative rSO₂ values. Per institutional guidelines, patients received interventions to restore the rSO₂ value to ≥80% of the baseline value. Analyzed rSO₂ variables included baseline value, and area under the threshold below an absolute value of 50% (AUT50). Their association with outcome was analyzed with multivariable logistic regression. AUT50 (odds ratio, 1.05; 95% confidence interval; 1.01–1.08; p = 0.015) was shown to be an independent risk factor (along with age, chronic kidney disease, and cardiopulmonary bypass time) of adverse outcomes. In cardiac surgical patients who received interventions to correct decreases in rSO₂, increased severity of intraoperative decrease in rSO₂ as reflected by AUT below an absolute value of 50% was associated with a composite of adverse outcomes, implicating the importance of cerebral oximetry to monitor the brain as an index organ.

Impact of CPAP on Forehead Near-infrared Spectroscopy Measurements in Patients With Acute Respiratory Failure: Truth or Illusion

BACKGROUND

Critically ill patients with acute respiratory failure admitted to an intensive care unit are at high risk for cerebral hypoxia. We investigated the impact of continuous positive airway pressure (CPAP) therapy on regional cerebral tissue oxygenation (rSO2).

MATERIALS AND METHODS

In total, 40 extubated surgical intensive care unit patients requiring classic oxygen therapy (COT) for acute respiratory failure were examined. Near-infrared spectroscopy (INVOS 5100C, Covidien) was used for 30 minutes to detect bilateral rSO2 during COT via facemask (6 L/min) and CPAP therapy (40% fraction of inspired oxygen, 8 cm H2O CPAP) using a randomized crossover study design. Patients served as their own control. Continuous hemodynamic routine monitoring and blood gas analysis were performed. The effect of CPAP therapy on rSO2 and influence of assessed covariables were investigated using a mixed linear model.

RESULTS

Median rSO2 increased from 57.9% (95% confidence interval [CI], 54.2-61.5) during COT to 62.8% (95% CI, 59.2-66.5) during CPAP therapy (P<0.0001). The estimated difference from the mixed model between COT and CPAP is -5.0 (95% CI, -6.3 to -3.7). Median arterial partial pressure of carbon dioxide decreased from 47.8±5.1 mm Hg during COT to 43.1±5 mm Hg during CPAP (P<0.001), whereas arterial partial pressure of oxygen remained unchanged (P=0.329). In total, 23% of patients had SO2 levels <50%, with a higher prevalence under COT.

CONCLUSIONS

Our results reveal that CPAP therapy compared with COT may influence rSO2 in patients with acute respiratory failure. However, the cause of the rSO2 increase following CPAP application remains to be elucidated, and the accuracy of cerebral oximetry during CPAP therapy in patients with acute respiratory failure remains questionable.