Cerebral oxygen saturation assessed by near-infrared spectroscopy during coronary artery bypass grafting and early postoperative cognitive function

A comprehensive review of cerebral oximetry in cardiac surgery

BACKGROUND

Patients who undergo cardiac surgery are at increased risk of stroke, postoperative cognitive decline, and delirium. These neurocognitive complications have led to increased costs, intensive care unit stays, morbidity, and mortality. As a result, there is a significant push to mitigate any neurological complications in cardiac surgery patients. Near-infrared spectroscopy to measure regional cerebral oxygen saturations has gained consideration due to its noninvasive and user-friendly nature. Cerebral oximetry desaturations during cardiac surgery have been linked to an array of adverse clinical outcomes. However, the most effective intraoperative interventions to protect this vulnerable patient population have yet to be ascertained.

AIM OF STUDY

To provide a comprehensive summary of the intraoperative management for cerebral oximetry desaturations during cardiac surgery. The review highlights clinical outcomes from cerebral oximetry use to quantify the importance of identifying cerebral desaturations during cardiac surgery. The review then interrogates possible interventions for cerebral oximetry desaturations in an effort to determine which interventions are most efficacious and to enlighten possible areas for further research.

METHODS

A narrative review of randomized controlled trials, observational studies, and systematic reviews with metanalyses was performed through August 2021.

RESULTS

There is significant heterogeneity among patient populations for which cerebral oximetry monitoring has been studied in cardiac surgery. Further, the definition of a clinically significant cerebral desaturation and the assessment of neurocognitive outcomes varied substantially across studies. As a result, metanalysis is challenging and few conclusions can be drawn. Cerebral oximetry use during cardiac surgery has not been associated with improvements in neurocognitive outcomes, morbidity, or mortality to date. The evidence to support a particular intervention for an acute desaturation is equivocal.

CONCLUSIONS

Future research is needed to quantify a clinically significant cerebral desaturation and to determine which interventions for an acute desaturation effectively improve clinical outcomes.

Neuromonitoring and Neurocognitive Outcomes in Cardiac Surgery: A Narrative Review

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

Cerebral oximetry and preventing neurological complication post-cardiac surgery: a systematic review

OBJECTIVES

This systematic review aims to provide an up-to-date summary of the current literature examining the relationship between intraoperative regional cerebral oxygen saturation and neurological complications after cardiac surgery.

METHODS

Observational and interventional studies investigating the link between regional cerebral oxygen saturation and postoperative delirium, cognitive dysfunction and stroke were included. After database searching and study screening, study characteristics and major findings were extracted.

RESULTS

Twenty-seven studies were identified. Of the observational studies (n = 17), 8 reported that regional cerebral oxygen desaturations were significantly associated with neurological complications after cardiac surgery. Of the interventional studies (n = 10), 3 provided evidence for monitoring cerebral oximetry during cardiac surgery as a means of reducing incidence of postoperative cognitive dysfunction or stroke. There was significant heterogeneity in the tools and rigor used to diagnose neurological complications.

CONCLUSIONS

Studies to date show an inconsistent relationship between regional cerebral oxygen saturation and neurological outcomes after cardiac surgery, and lack of clear benefit of targeting cerebral oximetry to minimize neurological complications. Standardized assessments, definitions of impairment and desaturation thresholds will help determine the benefits of cerebral oximetry monitoring during cardiac surgery.

Risk Factors for Delirium and Cognitive Decline Following Coronary Artery Bypass Grafting Surgery: A Systematic Review and Meta-Analysis

Background

Coronary artery bypass grafting (CABG) is known to improve heart function and quality of life, while rates of surgery‐related mortality are low. However, delirium and cognitive decline are common complications. We sought to identify preoperative, intraoperative, and postoperative risk or protective factors associated with delirium and cognitive decline (across time) in patients undergoing CABG.

Methods and Results

We conducted a systematic search of Medline, PsycINFO, EMBASE, and Cochrane (March 26, 2019) for peer‐reviewed, English publications reporting post‐CABG delirium or cognitive decline data, for at least one risk factor. Random‐effects meta‐analyses estimated pooled odds ratio for categorical data and mean difference or standardized mean difference for continuous data. Ninety‐seven studies, comprising data from 60 479 patients who underwent CABG, were included. Moderate to large and statistically significant risk factors for delirium were as follows: (1) preoperative cognitive impairment, depression, stroke history, and higher European System for Cardiac Operative Risk Evaluation (EuroSCORE) score, (2) intraoperative increase in intubation time, and (3) postoperative presence of arrythmia and increased days in the intensive care unit; higher preoperative cognitive performance was protective for delirium. Moderate to large and statistically significant risk factors for acute cognitive decline were as follows: (1) preoperative depression and older age, (2) intraoperative increase in intubation time, and (3) postoperative presence of delirium and increased days in the intensive care unit. Presence of depression preoperatively was a moderate risk factor for midterm (1–6 months) post‐CABG cognitive decline.

Conclusions

This meta‐analysis identified several key risk factors for delirium and cognitive decline following CABG, most of which are nonmodifiable. Future research should target preoperative risk factors, such as depression or cognitive impairment, which are potentially modifiable.

Registration

URL: https://www.crd.york.ac.uk/prosp​ero/; Unique identifier: CRD42020149276.

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.

Electroencephalography and Brain Oxygenation Monitoring in the Perioperative Period

Maintaining brain function and integrity is a pivotal part of anesthesiological practice. The present overview aims to describe the current role of the 2 most frequently used monitoring methods for evaluation brain function in the perioperative period, ie, electroencephalography (EEG) and brain oxygenation monitoring. Available evidence suggests that EEG-derived parameters give additional information about depth of anesthesia for optimizing anesthetic titration. The effects on reduction of drug consumption or recovery time are heterogeneous, but most studies show a reduction of recovery times if anesthesia is titrated along processed EEG. It has been hypothesized that future EEG-derived indices will allow a better understanding of the neurophysiological principles of anesthetic-induced alteration of consciousness instead of the probabilistic approach most often used nowadays.Brain oxygenation can be either measured directly in brain parenchyma via a surgical burr hole, estimated from the venous outflow of the brain via a catheter in the jugular bulb, or assessed noninvasively by near-infrared spectroscopy. The latter method has increasingly been accepted clinically due to its ease of use and increasing evidence that near-infrared spectroscopy-derived cerebral oxygen saturation levels are associated with neurological and/or general perioperative complications and increased mortality. Furthermore, a goal-directed strategy aiming to avoid cerebral desaturations might help to reduce these complications. Recent evidence points out that this technology may additionally be used to assess autoregulation of cerebral blood flow and thereby help to titrate arterial blood pressure to the individual needs and for bedside diagnosis of disturbed autoregulation.

Domain-specific cognitive dysfunction after cardiac surgery. A secondary analysis of a randomized trial

BACKGROUND

Brain injury and cognitive dysfunction are serious complications after cardiac surgery. In the perfusion pressure cerebral infarcts (PPCI) trial, we allocated cardiac surgery patients to a mean arterial pressure of either 70-80 mm Hg (high-target) or 40-50 mm Hg (low-target) during cardiopulmonary bypass. In this secondary analysis, we aimed to assess potential differences in domain-specific patterns of cognitive deterioration between allocation groups and to investigate any associations of postoperative cognitive dysfunction (POCD) with diffusion-weighted magnetic resonance imaging (DWI)-detected brain lesions.

METHODS

Of the 197 patients randomized in the PPCI trial, 89 in the low-target group and 80 in the high-target group had complete DWI datasets, and 92 and 80 patients had complete data for an evaluation of cognitive function at discharge respectively. Cognitive function was assessed prior to surgery, at discharge and at 3 months. DWI was obtained at baseline and on postoperative days 3 to 6.

RESULTS

We found no statistically significant differences between the two groups when comparing the proportion of patients with a domain-specific deterioration over the pre-defined critical level in seven individual test variables at discharge. Significant deterioration was most common in tests thought to assess cognitive flexibility and interference susceptibility and least common in the memory test. POCD at discharge was more frequent in patients with DWI-positive brain lesions (OR adjusted for age and group allocation: 2.24 [95% CI 1.48-3.00], P = 0.036).

CONCLUSIONS

Domain-specific patterns of POCD were comparable between groups. A significant association was seen between DWI-positive brain lesions and POCD.

The association between postoperative cognitive dysfunction and cerebral oximetry during cardiac surgery: a secondary analysis of a randomised trial

BACKGROUND

Postoperative cognitive dysfunction (POCD) occurs commonly after cardiac surgery. Near-infrared spectroscopy (NIRS) has been used to monitor regional cerebral oxygen saturation (rScO₂) in order to minimise the occurrence of POCD by applying dedicated interventions when rScO₂ decreases. However, the association between rScO₂ intraoperatively and POCD has not been clarified.

METHODS

This is a secondary analysis of a randomised trial with physician-blinded NIRS monitoring and cognitive testing at discharge from hospital and at 3 months after surgery. The association between intraoperative rScO₂ values and POCD at discharge from hospital and at 3 months after surgery was investigated. The prespecified candidate predictive variable of interest was cumulative time during surgery with rScO₂ ≥10% below its preoperative value.

RESULTS

One hundred and fifty-three patients had complete NIRS data and neurocognitive assessments at discharge, and 44 of these patients (29%) had POCD. At 3 months, 148 patients had complete data, and 12 (8%) of these patients had POCD. The median time with rScO₂ >10% below preoperative values did not differ for patients with and without POCD at discharge (difference=0.0 min; Hodges-Lehmann 95% confidence interval, -3.11-1.47, P=0.88). Other rScO₂ time thresholds that were assessed were also not significantly different between those with and without POCD at discharge. This applied both to absolute rScO₂ values and relative changes from preoperative values. Similar results were found in relation to POCD at 3 months.

CONCLUSIONS

No significant association was found between intraoperative rScO₂ values and POCD. These findings bring into question the rationale for attempting to avoid decreases in rScO₂ if the goal is to prevent POCD.

CLINICAL TRIAL REGISTRATION

NCT02185885.

Neurocognitive Function after Cardiac Surgery: From Phenotypes to Mechanisms

For half a century, it has been known that some patients experience neurocognitive dysfunction after cardiac surgery; however, defining its incidence, course, and causes remains challenging and controversial. Various terms have been used to describe neurocognitive dysfunction at different times after cardiac surgery, ranging from "postoperative delirium" to "postoperative cognitive dysfunction or decline." Delirium is a clinical diagnosis included in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Postoperative cognitive dysfunction is not included in the DSM-5 and has been heterogeneously defined, though a recent international nomenclature effort has proposed standardized definitions for it. Here, the authors discuss pathophysiologic mechanisms that may underlie these complications, review the literature on methods to prevent them, and discuss novel approaches to understand their etiology that may lead to novel treatment strategies. Future studies should measure both delirium and postoperative cognitive dysfunction to help clarify the relationship between these important postoperative complications.

Perioperative cognitive protection

There is significant evidence that many older surgical patients experience at least a transient decrease in cognitive function. Although there is still equipoise regarding the degree, duration, and mechanism of cognitive dysfunction, there is a concurrent need to provide best-practice clinical evidence. The two major cognitive disorders seen after surgery are postoperative delirium and postoperative cognitive dysfunction. Delirium is a public health problem; millions of dollars are spent annually on delirium-related medical resource use and prolonged hospital stays. Postoperative cognitive dysfunction is a research construct that historically signifies decline in performance on a neuropsychiatric test or group of tests and begins days to weeks after surgery. This review focuses on the current state of information gathered by several interdisciplinary stakeholder groups. Although there is still a need for high-level evidence to guide clinical practice, there is an emerging literature that can guide practitioners.

Brain natriuretic peptide (BNP) may play a major role in risk stratification based on cerebral oxygen saturation by near-infrared spectroscopy in patients undergoing major cardiovascular surgery

Purpose

A previous study reported that low baseline cerebral oxygen saturation (ScO₂) (≤50%) measured with near-infrared spectroscopy was predictive of poor clinical outcomes after cardiac surgery. However, such findings have not been reconfirmed by others. We conducted the current study to evaluate whether the previous findings would be reproducible, and to explore mechanisms underlying the ScO₂-based outcome prediction.

Methods

We retrospectively investigated 573 consecutive patients, aged 20 to 91 (mean ± standard deviation, 67.1 ± 12.8) years, who underwent major cardiovascular surgery. Preanesthetic baseline ScO₂, lowest intraoperative ScO₂, various clinical variables, and hospital mortality were examined.

Results

Bivariate regression analyses revealed that baseline ScO₂ correlated significantly with plasma brain natriuretic peptide concentration (BNP), hemoglobin concentration (Hgb), estimated glomerular filtration rate (eGFR), and left ventricular ejection fraction (LVEF) (p < 0.0001 for each). Baseline ScO₂ correlated with BNP in an exponential manner, and BNP was the most significant factor influencing ScO₂. Logistic regression analyses revealed that baseline and lowest intraoperative ScO₂ values, but not relative ScO₂ decrements, were significantly associated with hospital mortality (p < 0.05), independent of the EuroSCORE (p < 0.01). Receiver operating curve analysis of ScO₂ values and hospital mortality revealed an area under the curve (AUC) of 0.715 (p < 0.01) and a cutoff value of ≤50.5% for the baseline and ScO₂, and an AUC of 0.718 (p < 0.05) and a cutoff value of ≤35% for the lowest intraoperative ScO₂. Low baseline ScO₂ (≤50%) was associated with increases in intubation time, intensive care unit stay, hospital stay, and hospital mortality.

Conclusion

Baseline ScO₂ was reflective of severity of systemic comorbidities and was predictive of clinical outcomes after major cardiovascular surgery. ScO₂ correlated most significantly with BNP in an exponential manner, suggesting that BNP plays a major role in the ScO₂-based outcome prediction.

Cerebral and tissue oximetry

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

A systematic review of cerebral oxygenation-monitoring devices in cardiac surgery

Objective:

Cerebral oxygenation monitoring via near-infrared spectroscopy (NIRS) during cardiopulmonary bypass (CPB) is increasingly becoming an accepted and valued component of intraoperative monitoring. In recent years, new devices have become available which all make different claims. The purpose of this study is to examine the research on these individual devices to establish the levels of evidence for each and formulate a research path for further evaluation of this technology in cardiac surgery.

Methods:

This study is a systematic review of published research on cerebral oximetry. We searched PubMed, CINAHL and Scopus for full-length, peer-reviewed articles containing original data resulting from the study of patient neurologic outcomes based on the use of FDA-approved near-infrared spectroscopy devices. The studies were then grouped and classified based on the device used and the levels of evidence each study provided.

Results:

Only a very limited number of high-level clinical evidence research papers are currently available, with nearly all of those papers based on the INVOS system. This is likely due to the different lengths of time each device has been on the market and its availability for use in clinical trials. Challenges to testing include the expense of testing various devices, the lack of a globally accepted gold standard for cerebral oxygenation saturation, the limited availability of patient frontal surface area and the gradual adoption of this technology. Despite these limitations, significant results have been identified in relation to patient outcomes.

Conclusion:

At this time, there is limited high-level evidence available for all of the NIRS devices on the market despite significant outcomes found in these studies. Additional prospective randomized studies should be conducted in order to establish the potential role NIRS may play in patient monitoring as well as assessing the efficacy of the multiple devices on the market.

Relationship between intraoperative regional cerebral oxygen saturation trends and cognitive decline after total knee replacement: a post-hoc analysis

Background

Bilateral regional brain oxygen saturation (rSO₂) trends, reflecting intraoperative brain oxygen imbalance, could warn of brain dysfunction. Various types of cognitive impairment, such as memory decline, alterations in executive function or subjective complaints, have been described three months after surgery. Our aim was to explore the potential utility of rSO₂ values as a warning sign for the development of different types of decline in postoperative psychological function.

Methods

Observational post-hoc analysis of data for the patient sample (n = 125) of a previously conducted clinical trial in patients over the age of 65 years undergoing total knee replacement under spinal anesthesia. Demographic, hemodynamic and bilateral rSO₂ intraoperative values were recorded. An absolute rSO₂ value of <50% or a reduction of >20% or >25% below baseline were chosen as relevant cutoffs. Composite function test scores were created from baseline to three months for each patient and adjusted for the mean (SD) score changes for a control group (n = 55). Tests were used to assess visual-motor coordination and executive function (VM-EF) (Wechsler Digit Symbol-Coding and Visual Reproduction, Trail Making Test) and memory (Auditory Verbal Learning, Wechsler Memory Scale); scales were used to assess psychological symptoms.

Results

We observed no differences in baseline rSO₂ values; rSO₂ decreased significantly in all patients during surgery (P < 0.0001). Seventy-five patients (60%) had no sign of cognitive decline or psychological symptoms. Twenty-one patients (16.8%) had memory decline, 3 (2.4%) had VM-EF decline, and 33 (26.4%) had psychological symptoms. Left and right rSO₂ values were asymmetric in patients who had memory decline (mean [SD] left-right ratio of 95.03 [8.51] vs 101.29 [6.7] for patients with no changes, P = 0.0012). The mean right-left difference in rSO₂ was also significant in these patients (-2.87% [4.73%], lower on the right, P = 0.0034).

Conclusions

Detection of a trend to asymmetry in rSO₂ values can warn of possible postoperative onset of memory decline. Psychological symptoms and memory decline were common three months after knee replacement in our patients over the age of 65 years.

Accuracy of regional cerebral oxygen saturation in predicting postoperative cognitive dysfunction after total hip arthroplasty: regional cerebral oxygen saturation predicts POCD

To estimate the accuracy of regional cerebral oxygen saturation (rSO(2)) in predicting postoperative cognitive dysfunction (POCD) for patients undergoing total hip arthroplasty, 46 patients aged more than 50years old were enrolled. We measured the patients' cognitive function by using a battery of six neuropsychological tests before surgery and then 7days after surgery again. rSO(2) was continuously monitored by near-infrared spectroscopy during surgery. POCD was present in 9 (19.6%) patients 1week after surgery. Logistic regression analysis showed that increasing age [OR=1.224, P=0.035] and maximum percentage drop in rSO(2) (rSO(2%max)) [OR=1.618, P=0.011] were significant risk factors for POCD. The area under the receiver operating characteristic curve of rSO(2%max) was 0.833 [95% confidence interval (CI) 0.615-1.051] at cutoff value of 11%. The specificity and sensitivity of rSO(2%max) >11% in predicting POCD were 77.8% and 86.5%, respectively. rSO(2%max) more than 11% was a potential predictor for POCD.

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.

Changes in cerebral oximetry during peritoneal insufflation for laparoscopic procedures

Background:

Changes in cardiac output may occur during insufflation for laparoscopic procedures. However, there are limited data regarding its potential effects on cerebral oxygenation.

Materials and Methods:

Cerebral oxygenation (ScO₂), end tidal CO₂, heart rate, blood pressure and oxygen saturation by pulse oximetry were recorded every 5 minutes prior to insufflation, during insufflation and after desufflation. Minute ventilation was increased to maintain normocapnia and the depth of anesthesia was adjusted or fluids/phenylephrine administered to maintain the blood pressure within 20% of the baseline.

Results:

The cohort for the study included 70 adults for laparoscopic herniorrhaphy, gastric bypass or cholecystectomy. A total of 1004 ScO₂ values were obtained during laparoscopy. The ScO₂ decreased from the baseline in 758 of the 1004 data points. The ScO₂ was 0–9 less than the baseline in 47.8% of the values, 10–19 less than the baseline in 24.9% of the values and 20–29 less than the baseline in 26 values (2.6%). Eighty-two (8.2%) of the values were less than 80% of the baseline value, while 25 values (2.5%) were less than 75% of the baseline value. Twelve patients had at least one ScO₂ value that was less than 80% of the baseline and 6 had at least one ScO₂ value that was less than 75% of the baseline. Four patients of the cohort had ScO₂ values less than 80% of the baseline for more than 50% of the laparoscopic procedure.

Conclusions:

Although relatively uncommon, significant changes in cerebral oxygenation do occur in some patients during insufflation for laparoscopic surgery.

Effect of olprinone, a phosphodiesterase III inhibitor, on balance of cerebral oxygen supply and demand during cardiopulmonary bypass

Neuropsychological dysfunction with cardiopulmonary bypass (CPB) may be facilitated by inadequate cerebral oxygen balance during CPB. Olprinone, a phosphodiesterase III inhibitor, augments cerebral blood flow by a direct vasodilator effect on cerebral arteries. We conducted the present randomized study in patients undergoing cardiac surgery with CPB to investigate whether olprinone improved the balance of cerebral oxygen supply and demand during the rewarming period of CPB. After anesthesia, a 5.5 F fiberoptic oximeter catheter was inserted into the right jugular bulb retrogradely for monitoring the jugular venous oxyhemoglobin saturation (SjO2), and a probe of transcranial near-infrared spectroscopy was placed over the forehead for monitoring the bilateral regional cerebral oxygen saturation (rSO2). Patients were randomly assigned to 3 groups, and olprinone was administered at 0, 0.2, or 0.4 μg·kg(-1)·min(-1) after establishment of hypothermic CPB. Olprinone significantly prevented the reduction of the SjO2 at 5 and 10 minutes after the start of rewarming, although it did not alter rSO2. Furthermore, there was a minor reduction of the bilateral rSO2 at low doses of olprinone (0.2 μg·kg(-1)·min(-1)). We conclude that olprinone prevents the decrease of the SjO2 at the rewarming period and improves the balance of cerebral oxygen supply and demand during the rewarming period of CPB. In addition, a future extended study may be required to elucidate the effect of low dose of olprinone.

Noninvasive control of adequate cerebral oxygenation during low-flow antegrade selective cerebral perfusion on adults and infants in the aortic arch surgery

Real-time readings of the regional oxygen saturation (rSO(2)) using near-infrared spectroscopy (NIRS) during the aortic arch surgery can provide an early detection of perfusion or oxygenation abnormalities.

BACKGROUND

Aortic arch repair techniques using low-flow antegrade selective cerebral perfusion have been standardized to a certain degree. However, some of the often-stated beneficial effects have never been proven. Especially, the existence of an adequate continuous flow in both cerebral hemispheres during the surgical procedure still remains unclear as the monitoring of an effective perfusion remains a nonstandardized technique.

METHODS

Seventeen patients underwent surgical reconstruction of the aortic arch due to aortic aneurysm surgery (adult group n = 8 patients) or of the hypoplastic aortic arch due to hypoplastic left heart syndrome (HLHS) or aortic coarctation (infant group n = 9 patients) under general anesthesia and mild hypothermia (adult group 28 degrees C; infant group 25 degrees C). Mean weights were 92.75 +/- 14.00 kg and 4.29 +/- 1.32 kg, and mean ages were 58.25 +/- 10.19 years and 55.67 +/- 51.11 days in the adult group and the infant group, respectively. The cerebral O(2) saturation measurement was performed by continuous plotting of the somatic reflectance oximetry of the frontal regional tissue on both cerebral hemispheres (rSO(2), INVOS; Somanetics Corporation, Troy, MI, USA).

RESULTS

During low-flow antegrade perfusion via innominate artery, continuous plots with similar values of O(2) saturation (rSO(2)) in both cerebral hemispheres were observed, whereas a decrease in the rSO(2) values below the desaturation threshold correlated with a displacement or an incorrect positioning of the arterial cannula in the right subclavian artery.

CONCLUSIONS

Continuous monitorization of the cerebral O(2) saturation during aortic arch surgery in adults and infants is a feasible technique to control an adequate cannula positioning and to optimize clinical outcomes avoiding neurological complications related to cerebral malperfusion.

Significant decrease of cerebral oxygen saturation during single-lung ventilation measured using absolute oximetry

BACKGROUND

Single-lung ventilation (SLV) during thoracic surgery causes important cardiopulmonary disturbances. Absolute cerebral oximetry was used to determine the incidence and magnitude of the decrease in cerebral oxygen saturation (Sct(o(2))) in patients undergoing SLV during thoracic surgery.

METHODS

Data were obtained from 20 consecutive patients undergoing thoracic surgery and necessitating SLV of more than 1 h. The FORESIGHTtrade mark (CASMED, USA) absolute oximeter was used to measure left, right, and average absolute Sct(o(2)) every 5 min from the awake state to extubation. Bispectral index and standard monitoring parameters were also recorded every 5 min. Blood gas analysis was performed every 15 min. Data median (IQR) (range) were analysed using repeated-measures anova and Spearman's correlation test, P<0.05.

RESULTS

Patients [median age 65 yr (range 46-75)] showed an absolute Sct(o(2)) of 80% (78, 82) (74-87) in the awake state, which decreased to a minimum Sct(o(2)) value of 63% (57, 65) (53-73) during SLV to recover to an Sct(o(2)) of 71% immediately after extubation. During SLV, all patients had a decrease of more than 15% of the initial Sct(o(2)) and 70% of patients had a decrease of more than 20%. The decrease in Sct(o(2)) was not correlated with any standard clinical parameters, for example, arterial pressure, blood loss, peripheral oxygen saturation, or Pa(o(2)).

CONCLUSIONS

Thoracic surgery with SLV seems to be associated with a significant decrease of Sct(o(2)) in the majority of patients. Parameters such as peripheral oxygen saturation or Po(2) which are used to guide SLV during thoracic surgery are not sufficient to detect significant cerebral oxygen desaturations.

Recent Advances in Application of Cerebral Oximetry in Adult Cardiovascular Surgery

Cerebral oximetry is a noninvasive technology that continuously monitors cerebral tissue oxygen saturation, which is a sensitive index of global cerebral hypoperfusion. On the basis of near-infrared spectroscopy technology, information is provided on the availability of oxygen in brain tissue at risk during numerous pathological conditions. Complementary to the arterial oxygen saturation measured by pulse oximetry, cerebral tissue oxygen saturation reflects regional cerebral metabolism and the balance of local cerebral oxygen supply/demand. Recently, patient management with the guidance of cerebral oximetry has resulted in improved patient outcomes. This review will briefly describe the physics behind cerebral oximetry and will provide an overview of the literature focusing primarily on articles published within the past 5 years.

Anesthesia management in a child with PHACE syndrome and agenesis of bilateral internal carotid arteries

This is the first case report of successful anesthesia management in a high-risk neurological procedure in a patient with PHACE syndrome. PHACE syndrome is rare but an important clinical entity. Anesthesiologists should be aware of the neurological, otolaryngogical, and vascular risk associated with this syndrome.

Regional cerebral saturation monitoring with near-infrared spectroscopy during selective antegrade cerebral perfusion: Diagnostic performance and relationship to postoperative stroke

OBJECTIVE

To investigate whether regional cerebral tissue oxygen saturation monitoring during hypothermic selective antegrade cerebral perfusion in surgery involving the aortic arch can predict neurologic sequelae and to evaluate the diagnostic performance of near-infrared spectroscopy monitoring in this setting.

METHODS

Data from 46 consecutive patients were analyzed. Selective antegrade cerebral perfusion was established by perfusion of the right subclavian artery (with or without left carotid artery perfusion) or by separate concomitant perfusion of the innominate and the left carotid arteries. The bilateral regional cerebral tissue oxygen saturation index was monitored by using near-infrared spectroscopy equipment (INVOS 4100). Stroke was the primary clinical end point, along with the indices of diagnostic performance.

RESULTS

Six patients died in the hospital, and 6 patients (13%) experienced a perioperative stroke. In patients with stroke, regional cerebral tissue oxygen saturation values were significantly lower during selective antegrade cerebral perfusion, and regional cerebral tissue oxygen saturation tended to be lower in the affected hemisphere. In receiver operating characteristic curve analysis, the area under the curve for relative regional cerebral tissue oxygen saturation values ranged from 0.72 to 0.87. During selective antegrade cerebral perfusion, regional cerebral tissue oxygen saturation between 76% and 86% of baseline had a sensitivity up to 83% and a specificity up to 94% in identifying individuals with stroke. The associated odds ratio for stroke was 5.6 (95% confidence interval, 0.5-144) to 21 (95% confidence interval, 1.8-566).

CONCLUSIONS

Monitoring of regional cerebral tissue oxygen saturation by using near-infrared spectroscopy during selective antegrade cerebral perfusion allows detection of clinically important cerebral desaturation. It can help predict perioperative neurologic sequelae. Its performance as a diagnostic instrument is satisfying and supports its use as a noninvasive trend monitor of cerebral saturation.

Advanced neurologic monitoring for cardiac surgery

Cardiac surgery (CS) with cardiopulmonary bypass (CPB) is currently the most common surgery in the United States. Understanding, avoiding, and preventing postoperative complications, including neurologic deficits following CS, represents a great public and economic benefit for society, especially considering our aging population. There is a critical need to identify new strategies that will prevent harmful events during and after CS. At present, experience with neurophysiologic techniques includes the ability to measure cerebral blood flow velocity/emboli and regional cerebral venous oxygen saturation by transcranial Doppler ultrasound, and by near-infrared spectroscopy, respectively. Continuous monitoring of these variables along with systemic hemodynamics will provide a better understanding of mechanisms of brain and other organ injury during CPB. Neuroprotective interventions based on multimodality neurologic monitoring would ideally eliminate postoperative complications and improve patient outcomes.

Neural correlates of cognitive dysfunction after cardiac surgery

Patients who underwent cardiac surgery and their relatives often complain on postoperative memory impairment. Most prospective neuropsychological studies also found postoperative cognitive decline early after surgery. Nevertheless, recently several reports questioned the existence of long-term brain alterations in these patient cohorts. The present review was aimed to clear up the true cardiac surgery effects on brain and cognitive functions. The reviewed data evidence that cardiac surgery interventions induce persistent localized brain ischemic lesions along with rapidly reversing global brain swelling and decreased metabolism. A range of studies showed that left temporal region was especially prone to perioperative ischemic injury, and these findings might explain persistent verbal short-term memory decline in a considerable proportion of cardiac surgery patient cohorts. Speed/time of cognitive performance is commonly decreased early after on-pump surgery either. Nevertheless, no association between psychomotor speed slowing and intraoperative embolic load was found. The rapid recovery of the latter cognitive domain might be better explained by surgery related acute global brain metabolism changes rather than ischemic injury effects. Hence, analyses of performance on separate cognitive tests rather than summarized cognitive indexes are strongly recommended for future neuropsychological studies of cardiac surgery outcomes.

Hypothermic circulatory arrest is not a risk factor for neurologic morbidity in aortic surgery: A propensity score analysis

OBJECTIVE

Hypothermic circulatory arrest has been an important tool in aortic arch surgery, even though its use has recently been discussed controversially. We sought to clarify the role of hypothermic circulatory arrest as a risk factor for mortality and neurologic morbidity in aortic surgery by using a propensity score-matching analysis.

METHODS

Five hundred eleven patients (60 +/- 13 years, 349 male patients) who underwent replacement of the ascending aorta with (n = 273) or without (n = 238) arch involvement were analyzed by means of multivariate analysis. Using propensity score matching, we identified comparable patient groups: HCA(+) group and HCA(-) group (n = 110 each). For aortic arch replacement, hypothermic circulatory arrest was used with a mean duration of 14 +/- 9 minutes: 12 +/- 7 minutes or 26 +/- 8 minutes for partial or total arch replacement, respectively.

RESULTS

In the entire cohort multivariate analysis identified acute dissection and duration of cardiopulmonary bypass as significant predictors for hospital death. Predictors for stroke were acute dissection, diabetes mellitus, peripheral arterial disease, and concomitant mitral valve surgery, and predictors for temporary neurologic dysfunction were peripheral arterial disease and age. After propensity score matching, the incidence of death (HCA[+]: 0.9% vs HCA[-]: 2.7%), stroke (0% vs 1.8%, respectively), and temporary neurologic dysfunction (15.5% vs 13.6%, respectively) was comparable between the 2 groups. Multivariate analysis identified age, diabetes mellitus, peripheral arterial disease, and concomitant coronary artery bypass grafting as the independent risk factors for temporary neurologic dysfunction.

CONCLUSIONS

In a standard clinical setting (hypothermic circulatory arrest of <30 minutes and nasopharyngeal temperature of <20 degrees C), hypothermic circulatory arrest constitutes no significant risk for mortality or neurologic morbidity and thus appears clinically safe. Patient-related risk factors primarily determine clinical outcome.

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

PURPOSE

This systematic review is aimed at answering the following questions: 1) Is near-infrared spectroscopy (NIRS) clinically effective in detecting cerebral desaturation during heart surgery? 2) Are these results based on studies with solid methodology?

SOURCES

MEDLINE, internet, and hand searches up to February 2004 for English and French papers on NIRS.

PRINCIPAL FINDINGS

Forty-eight papers were retrieved, with a total of 5,931 cardiac surgery patients monitored by NIRS. More than 83% of patients underwent coronary artery bypass graft surgery. The majority of studies were prospective for the monitored group. Clinically, NIRS monitoring appears to detect brain desaturation episodes encountered during surgery. However, the majority of studies retrieved suffered from major methodological limitations and a low level of evidence. NIRS validity vs jugular bulb oximetry is questioned together with its predictive value in identifying those who will suffer postoperatively from neurological deficits. The sole randomized controlled trial appears to have recorded negative results in this respect.

CONCLUSION

The clinical application of NIRS in heart surgery as a brain-monitoring device seems interesting. However, NIRS has to be investigated more rigorously to prove its clinical utility in cardiac surgery.

Neurologic Injury Associated with CABG Surgery: Outcomes, Mechanisms, and Opportunities for Improvement

Neurologic injuries, whether subtle or overt, are a major source of morbidity secondary to coronary artery bypass graft (CABG) surgery. A comprehensive review of research in the area of neurologic injury is provided. We conclude this article by providing insight regarding areas requiring further investigation in order to reduce sustainably the risk of these iatrogenic events among patient undergoing CABG surgery.

Regional cerebral oxygen saturation is a sensitive marker of cerebral hypoperfusion during orthotopic liver transplantation

Neurological complications contribute significantly to morbidity and mortality of patients after orthotopic liver transplantation (OLT). One possible cause of postoperative neurological complications is cerebral ischemia during the surgical procedure. In this study, we investigated the relationship between intraoperative changes in regional cerebral oxygen saturation (rSo(2)) and postoperative values of neuron-specific enolase (NSE) and S-100, which are specific variables that indicate cerebral disturbances due to hypoxia/ischemia. The rSo(2) was monitored continuously by near-infrared spectroscopy in 16 patients undergoing OLT. In addition, NSE and S-100 were determined in arterial blood before surgery and 24 h after reperfusion of the donor liver. Interestingly, clamping of the recipient's liver led to a significant decline in rSo(2) in eight patients, whereas the others tolerated clamping without major changes in rSo(2). The decrease in rSo(2) after clamping correlated significantly with postoperative increases in NSE (r(2) = 0.57) and S-100 (r(2) = 0.52). However, there were no significant differences between patients with and without rSo(2) decline concerning hemodynamic variables. There were no significant correlations between DeltarSo(2) and cardiac output (r(2) = 0.20), NSE and cardiac output (r(2) = 0.37), or S-100 and cardiac output (r(2) = 0.24). Monitoring of rSo(2) may be a useful noninvasive tool to estimate disturbances in rSo(2) during OLT.