Dysfunctional cerebral autoregulation is associated with delirium in critically ill adults

Microvascular Autoregulation in Skeletal Muscle Using Near-Infrared Spectroscopy and Derivation of Optimal Mean Arterial Pressure in the ICU: Pilot Study and Comparison With Cerebral Near-Infrared Spectroscopy

IMPORTANCE

Microvascular autoregulation (MA) maintains adequate tissue perfusion over a range of arterial blood pressure (ABP) and is frequently impaired in critical illness. MA has been studied in the brain to derive personalized hemodynamic targets after brain injury. The ability to measure MA in other organs is not known, which may inform individualized management during shock.

OBJECTIVES

This study determines the feasibility of measuring MA in skeletal muscle using near-infrared spectroscopy (NIRS) as a marker of tissue perfusion, the derivation of optimal mean arterial pressure (MAPopt), and comparison with indices from the brain.

DESIGN

Prospective observational study.

SETTING

Medical and surgical ICU in a tertiary academic hospital.

PARTICIPANTS

Adult critically ill patients requiring vasoactive support on the first day of ICU admission.

MAIN OUTCOMES AND MEASURES

Fifteen critically ill patients were enrolled. NIRS was applied simultaneously to skeletal muscle (brachioradialis) and brain (frontal cortex) while ABP was measured continuously via invasive catheter. MA correlation indices were calculated between ABP and NIRS from skeletal muscle total hemoglobin (MVx), muscle tissue saturation index (MOx), brain total hemoglobin (THx), and brain tissue saturation index (COx). Curve fitting algorithms derive the MAP with the lowest correlation index value, which is the MAPopt.

RESULTS

MAPopt values were successfully calculated for each correlation index for all patients and were frequently (77%) above 65 mm Hg. For all correlation indices, median time was substantially above impaired MA threshold (24.5-34.9%) and below target MAPopt (9.0-78.6%). Muscle and brain MAPopt show moderate correlation (MVx-THx r = 0.76, p < 0.001; MOx-COx r = 0.69, p = 0.005), with a median difference of -1.27 mm Hg (-9.85 to -0.18 mm Hg) and 0.05 mm Hg (-7.05 to 2.68 mm Hg).

CONCLUSIONS AND RELEVANCE

This study demonstrates, for the first time, the feasibility of calculating MA indices and MAPopt in skeletal muscle using NIRS. Future studies should explore the association between impaired skeletal muscle MA, ICU outcomes, and organ-specific differences in MA and MAPopt thresholds.

Cerebral autoregulation-directed optimal blood pressure management reduced the risk of delirium in patients with septic shock

Background

When resuscitating patients with septic shock, cerebrovascular reactivity parameters are calculated by monitoring regional cerebral oxygen saturation (rSO2) using near-infrared spectroscopy to determine the optimal blood pressure. Here, we aimed to analyze the impact of cerebral autoregulation-directed optimal blood pressure management on the incidence of delirium and the prognosis of patients with septic shock.

Methods

This prospective randomized controlled clinical study was conducted in the Xiangya Hospital of Central South University, China. Fifty-one patients with septic shock (December 2020-May 2022) were enrolled and randomly allocated to the experimental (n=26) or control group (n=25). Using the ICM+ software, we monitored the dynamic changes in rSO2 and mean arterial pressure (MAP) and calculated the cerebrovascular reactivity parameter tissue oxygen reactivity index to determine the optimal blood pressure to maintain normal cerebral autoregulation function during resuscitation in the experimental group. The control group was treated according to the Surviving Sepsis Campaign Guidelines. Differences in the incidence of delirium and 28-day mortality between the two groups were compared, and the risk factors were analyzed.

Results

The 51 patients, including 39 male and 12 female, had a mean age of (57.0±14.9) years. The incidence of delirium was 40.1% (23/51), and the 28-day mortality rate was 29.4% (15/51). The mean MAP during the first 24 h of intensive care unit (ICU) admission was higher ([84.5±12.2] mmHg vs. [77.4±11.8] mmHg, P=0.040), and the incidence of delirium was lower (30.8% vs. 60.0%, P=0.036) in the experimental group than in the control group. The use of cerebral autoregulation-directed optimal blood pressure (odds ratio [OR]=0.090, 95% confidence interval [CI]: 0.009 to 0.923, P=0.043) and length of ICU stay (OR=1.473, 95% CI: 1.093 to 1.985, P=0.011) were risk factors for delirium during septic shock. Vasoactive drug dose (OR=8.445, 95% CI: 1.26 to 56.576, P=0.028) and partial pressure of oxygen (PaO2) (OR=0.958, 95% CI: 0.921 to 0.996, P=0.032) were the risk factors for 28-day mortality.

Conclusions

The use of cerebral autoregulation-directed optimal blood pressure management during shock resuscitation reduces the incidence of delirium in patients with septic shock.

Trial Registration

ClinicalTrials.gov ldentifer: NCT03879317.

Future of neurocritical care: Integrating neurophysics, multimodal monitoring, and machine learning

Multimodal monitoring (MMM) in the intensive care unit (ICU) has become increasingly sophisticated with the integration of neurophysical principles. However, the challenge remains to select and interpret the most appropriate combination of neuromonitoring modalities to optimize patient outcomes. This manuscript reviewed current neuromonitoring tools, focusing on intracranial pressure, cerebral electrical activity, metabolism, and invasive and noninvasive autoregulation monitoring. In addition, the integration of advanced machine learning and data science tools within the ICU were discussed. Invasive monitoring includes analysis of intracranial pressure waveforms, jugular venous oximetry, monitoring of brain tissue oxygenation, thermal diffusion flowmetry, electrocorticography, depth electroencephalography, and cerebral microdialysis. Noninvasive measures include transcranial Doppler, tympanic membrane displacement, near-infrared spectroscopy, optic nerve sheath diameter, positron emission tomography, and systemic hemodynamic monitoring including heart rate variability analysis. The neurophysical basis and clinical relevance of each method within the ICU setting were examined. Machine learning algorithms have shown promise by helping to analyze and interpret data in real time from continuous MMM tools, helping clinicians make more accurate and timely decisions. These algorithms can integrate diverse data streams to generate predictive models for patient outcomes and optimize treatment strategies. MMM, grounded in neurophysics, offers a more nuanced understanding of cerebral physiology and disease in the ICU. Although each modality has its strengths and limitations, its integrated use, especially in combination with machine learning algorithms, can offer invaluable information for individualized patient care.

Diffuse optical tomography for mapping cerebral hemodynamics and functional connectivity in delirium

INTRODUCTION

Delirium is associated with mortality and new onset dementia, yet the underlying pathophysiology remains poorly understood. Development of imaging biomarkers has been difficult given the challenging nature of imaging delirious patients. Diffuse optical tomography (DOT) offers a promising approach for investigating delirium given its portability and three-dimensional capabilities.

METHODS

Twenty-five delirious and matched non-delirious patients (n = 50) were examined using DOT, comparing cerebral oxygenation and functional connectivity in the prefrontal cortex during and after an episode of delirium.

RESULTS

Total hemoglobin values were significantly decreased in the delirium group, even after delirium resolution. Functional connectivity between the dorsolateral prefrontal cortex and dorsomedial prefrontal cortex was strengthened post-resolution compared to during an episode; however, this relationship was still significantly weaker compared to controls.

DISCUSSION

These findings highlight DOT's potential as an imaging biomarker to measure impaired cerebral oxygenation and functional dysconnectivity during and after delirium. Future studies should focus on the role of cerebral oxygenation in delirium pathogenesis and exploring the etiological link between delirium and dementias.

HIGHLIGHTS

We developed a portable diffuse optical tomography (DOT) system for bedside three-dimensional functional neuroimaging to study delirium in the hospital. We implemented a novel DOT task-focused seed-based correlation analysis. DOT revealed decreased cerebral oxygenation and functional connectivity strength in the delirium group, even after resolution of delirium.

Cerebral autoregulation-based mean arterial pressure targets and delirium in critically ill adults without brain injury: a retrospective cohort study

PURPOSE

Cerebral autoregulation (CA) is a mechanism that acts to maintain consistent cerebral perfusion across a range of blood pressures, and impaired CA is associated with delirium. Individualized CA-derived blood pressure targets are poorly characterized in critically ill patients and the association with intensive care unit (ICU) delirium is unknown. Our objectives were to characterize optimal mean arterial pressure (MAPopt) ranges in critically ill adults without brain injury and determine whether deviations from these targets contribute to ICU delirium.

METHODS

We performed a retrospective cohort analysis of patients with shock of any etiology and/or respiratory failure requiring invasive mechanical ventilation, without a neurologic admitting diagnosis. Patients were screened daily for delirium. Cerebral oximetry and mean arterial pressure data were captured for the first 24 hr from enrolment.

RESULTS

Forty-two patients with invasive blood pressure monitoring data were analyzed. Optimal mean arterial pressure targets ranged from 55 to 100 mm Hg. Optimal mean arterial pressure values were not significantly different based on history of hypertension or delirium status, and delirium was not associated with deviations from MAPopt. Nevertheless, the majority (69%) of blood pressure targets exceeded the current 65 mm Hg Surviving Sepsis guidelines.

CONCLUSION

We observed that MAPopt targets across patients were highly variable, but did not observe an association with the incidence of delirium. Studies designed to evaluate the impact on neurologic outcomes are needed to understand the association with individualized mean arterial pressure targets in the ICU.

STUDY REGISTRATION

ClinicalTrials.gov (NCT02344043); first submitted 22 January 2015.

Determining Optimal Mean Arterial Blood Pressure Based on Cerebral Autoregulation in Children after Cardiac Surgery

To evaluate the feasibility of continuous determination of the optimal mean arterial blood pressure (opt-MAP) according to cerebral autoregulation and to describe the opt-MAP, the autoregulation limits, and the time spent outside these limits in children within 48 h of cardiac surgery. Cerebral autoregulation was assessed using the correlation coefficient (COx) between cerebral oxygenation and MAP in children following cardiac surgery. Plots depicting the COx according to the MAP were used to determine the opt-MAP using weighted multiple time windows. For each patient, we estimated (1) the time spent with MAP outside the autoregulation limits and (2) the burden of deviation, defined as the area between the MAP curve and the autoregulation limits when the MAP was outside these limits. Fifty-one patients with a median age of 7.1 (IQR 0.7-52.0) months old were included. The opt-MAP was calculated for 94% (IQR 90-96) of the monitored time. The opt-MAP was significantly lower in neonates < 1 month old. The patients spent 24% (18-31) of the time outside of the autoregulation limits, with no significant differences between age groups. Continuous determination of the opt-MAP is feasible in children within the first 48 h following cardiac surgery.

Neurologic complications after cardiopulmonary bypass - A narrative review

Neurologic complications, associated with cardiac surgery and cardiopulmonary bypass (CPB) in adults, are common and can be devastating in some cases. This comprehensive review will not only consider the broad categories of stroke and neurocognitive dysfunction, but it also summarises other neurological complications associated with CPB, and it provides an update about risks, prevention and treatment. Where appropriate, we consider the impact of off-pump techniques upon our understanding of the contribution of CPB to adverse outcomes.

Sevoflurane-induced hypotension causes cognitive dysfunction and hippocampal inflammation in mice

Sevoflurane commonly adopted for anesthetic in clinical practice, however, its influences on cerebral blood flow and cognitive function remain controversial. Herein, the sevoflurane-induced hypotension on arterial blood pressure, cerebral blood flow, cognitive function, and hippocampal inflammation was investigated in mice. A significant decrease in arterial blood pressure and cerebral blood flow was indicated by the sevoflurane anesthesia treatment. Moreover, sevoflurane-induced hypotension was associated with the impaired cognitive function and the increased levels of NLRP3 inflammasome activation and oxidative stress in hippocampus. These findings suggest that sevoflurane-induced hypotension may lead to the cognitive dysfunction and hippocampal inflammation.

Neurological Impairment in Critically Ill Patients on Dialysis: Research Letter for the INCOGNITO-AKI Feasibility Study

Background

Acute kidney injury (AKI) resulting in kidney replacement therapy is rising among critically ill adults. Long-term kidney replacement therapy and critical illness are independently linked to acute and prolonged cognitive impairment, and structural brain pathology. Poor regional cerebral oxygenation (rSO2) may be a contributing factor.

Objective

To assess the feasibility of testing the association between intradialytic rSO2 and acute and long-term neurological outcomes.

Design

Longitudinal observational study.

Setting and Participants

We enrolled patients initiating continuous kidney replacement therapy or intermittent hemodialysis in the Kingston Health Sciences Centre (KHSC) Intensive Care Unit (ICU).

Measurements and Methods

rSO2 was monitored during the first 72 hours of continuous kidney replacement therapy or throughout each intermittent hemodialysis session. We measured acute neurological impairment by daily delirium screening and long-term neurocognitive outcomes using the Kinarm robot, Repeatable Battery for the Assessment of Neuropsychological Status, and brain magnetic resonance imaging.

Results

Of 484 ICU patients, 26 met the screening criteria. Two declined, and 13 met at least one exclusion criteria. Eleven patients were enrolled. Eight died in ICU, one died 2 months after discharge, and one declined follow-up. Data capture rates were high: rSO2/vitals (91.3%), and delirium screening and demographics (100%). Longitudinal testing was completed in 50% (1 of 2) of survivors.

Limitations

Enrollment was low due to a variety of factors, limiting our ability to evaluate long-term outcomes.

Conclusion

rSO2 and delirium data collection is feasible in critically ill patients undergoing kidney replacement therapy; high mortality limits follow-up.

Monitoring the Cerebral Oximetry Index Along With In-line Cardiopulmonary Bypass Parameters in a High-Risk Patient Undergoing Cardiac Surgery: A Case Report

The quest to minimize the morbidity and mortality of patients undergoing cardiac surgery is ongoing. Impaired cerebral autoregulation and tissue malperfusion are linked with neurological complications. The cerebral oximetry index (COx) has been introduced as an index of cerebral autoregulation, while in-line monitoring enables the detection and prevention of metabolic disturbances during cardiopulmonary bypass (CPB). This report presents the case of a 58-year-old female patient scheduled for aortic valve replacement under minimally invasive extracorporeal circulation (MiECC). Her medical history consisted of epilepsy, multiple ischemic strokes, heavy smoking, and brachiocephalic artery stenosis. We sought to investigate the limits of autoregulation and the role of metabolic indices of perfusion on COx. Mean arterial blood pressure (ABP), cerebral oximetry (rSO₂), and in-line perfusion data during CPB were recorded at 10s intervals. The lower limit of autoregulation was 44mmHg on both sides and the upper limit was 98mmHg on the right and 107mmHg on the left side. A multiple linear regression analysis was performed to identify any potential predictors of COx values. Hemoglobin (Hb), PCO₂, flow, DO₂ index (DO₂i), Ο₂ extraction ratio (O₂ER), and perfusion ratio (PR) were included in the analysis. Significant equations were found on both sides. Predicted COx left was equal to 5.8 - 11.04O₂ER - 0.04Hb (p=0.001, R²= 0.15). Predicted COx right was equal to 3.06 - 0.3flow - 6.8O₂ER -0.03Hb + 0.02PCO₂ + 0.004DO₂i(p=0.03, R²=0.13). Targeting physiological perfusion and monitoring perfusion during CPB may have an additional impact on cerebral autoregulation and should be studied further.

Multimodal and autoregulation monitoring in the neurointensive care unit

Given the complexity of cerebral pathology in patients with acute brain injury, various neuromonitoring strategies have been developed to better appreciate physiologic relationships and potentially harmful derangements. There is ample evidence that bundling several neuromonitoring devices, termed "multimodal monitoring," is more beneficial compared to monitoring individual parameters as each may capture different and complementary aspects of cerebral physiology to provide a comprehensive picture that can help guide management. Furthermore, each modality has specific strengths and limitations that depend largely on spatiotemporal characteristics and complexity of the signal acquired. In this review we focus on the common clinical neuromonitoring techniques including intracranial pressure, brain tissue oxygenation, transcranial doppler and near-infrared spectroscopy with a focus on how each modality can also provide useful information about cerebral autoregulation capacity. Finally, we discuss the current evidence in using these modalities to support clinical decision making as well as potential insights into the future of advanced cerebral homeostatic assessments including neurovascular coupling.

Diaphragm Neurostimulation Mitigates Ventilation-Associated Brain Injury in a Preclinical Acute Respiratory Distress Syndrome Model

In a porcine healthy lung model, temporary transvenous diaphragm neurostimulation (TTDN) for 50 hours mitigated hippocampal apoptosis and inflammation associated with mechanical ventilation (MV).

HYPOTHESIS

Explore whether TTDN in combination with MV for 12 hours mitigates hippocampal apoptosis and inflammation in an acute respiratory distress syndrome (ARDS) preclinical model.

METHODS AND MODELS

Compare hippocampal apoptosis, inflammatory markers, and serum markers of neurologic injury between never ventilated subjects and three groups of mechanically ventilated subjects with injured lungs: MV only (LI-MV), MV plus TTDN every other breath, and MV plus TTDN every breath. MV settings in volume control were tidal volume 8 mL/kg and positive end-expiratory pressure 5 cm H₂O. Lung injury, equivalent to moderate ARDS, was achieved by infusing oleic acid into the pulmonary artery.

RESULTS

Hippocampal apoptosis, microglia, and reactive-astrocyte percentages were similar between the TTDN-every-breath and never ventilated groups. The LI-MV group had a higher percentage of these measures than all other groups (p < 0.05). Transpulmonary driving pressure at study end was lower in the TTDN-every-breath group than in the LI-MV group; systemic inflammation and lung injury scores were not significantly different. The TTDN-every-breath group had considerably lower serum concentration of homovanillic acid (cerebral dopamine production surrogate) at study end than the LI-MV group (p < 0.05). Heart rate variability declined in the LI-MV group and increased in both TTDN groups (p < 0.05).

INTERPRETATIONS AND CONCLUSIONS

In a moderate-ARDS porcine model, MV is associated with hippocampal apoptosis and inflammation, and TTDN mitigates that hippocampal apoptosis and inflammation.

Automated machine learning-based model for the prediction of delirium in patients after surgery for degenerative spinal disease

OBJECTIVE

This study used machine learning algorithms to identify critical variables and predict postoperative delirium (POD) in patients with degenerative spinal disease.

METHODS

We included 663 patients who underwent surgery for degenerative spinal disease and received general anesthesia. The LASSO method was used to screen essential features associated with POD. Clinical characteristics, preoperative laboratory parameters, and intraoperative variables were reviewed and were used to construct nine machine learning models including a training set and validation set (80% of participants), and were then evaluated in the rest of the study sample (20% of participants). The area under the receiver-operating characteristic curve (AUROC) and Brier scores were used to compare the prediction performances of different models. The eXtreme Gradient Boosting algorithms (XGBOOST) model was used to predict POD. The SHapley Additive exPlanations (SHAP) package was used to interpret the XGBOOST model. Data of 49 patients were prospectively collected for model validation.

RESULTS

The XGBOOST model outperformed the other classifier models in the training set (area under the curve [AUC]: 92.8%, 95% confidence interval [CI]: 90.7%-95.0%), validation set (AUC: 87.0%, 95% CI: 80.7%-93.3%). This model also achieved the lowest Brier Score. Twelve vital variables, including age, serum albumin, the admission-to-surgery time interval, C-reactive protein level, hypertension, intraoperative blood loss, intraoperative minimum blood pressure, cardiovascular-cerebrovascular disease, smoking, alcohol consumption, pulmonary disease, and admission-intraoperative maximum blood pressure difference, were selected. The XGBOOST model performed well in the prospective cohort (accuracy: 85.71%).

CONCLUSION

A machine learning model and a web predictor for delirium after surgery for the degenerative spinal disease were successfully developed to demonstrate the extent of POD risk during the perioperative period, which could guide appropriate preventive measures for high-risk patients.

Comparison of logistic regression and machine learning methods for predicting postoperative delirium in elderly patients: A retrospective study

AIMS

To compare the performance of logistic regression and machine learning methods in predicting postoperative delirium (POD) in elderly patients.

METHOD

This was a retrospective study of perioperative medical data from patients undergoing non-cardiac and non-neurology surgery over 65 years old from January 2014 to August 2019. Forty-six perioperative variables were used to predict POD. A traditional logistic regression and five machine learning models (Random Forest, GBM, AdaBoost, XGBoost, and a stacking ensemble model) were compared by the area under the receiver operating characteristic curve (AUC-ROC), sensitivity, specificity, and precision.

RESULTS

In total, 29,756 patients were enrolled, and the incidence of POD was 3.22% after variable screening. AUCs were 0.783 (0.765-0.8) for the logistic regression method, 0.78 for random forest, 0.76 for GBM, 0.74 for AdaBoost, 0.73 for XGBoost, and 0.77 for the stacking ensemble model. The respective sensitivities for the 6 aforementioned models were 74.2%, 72.2%, 76.8%, 63.6%, 71.6%, and 67.4%. The respective specificities for the 6 aforementioned models were 70.7%, 99.8%, 96.5%, 98.8%, 96.5%, and 96.1%. The respective precision values for the 6 aforementioned models were 7.8%, 52.3%, 55.6%, 57%, 54.5%, and 56.4%.

CONCLUSIONS

The optimal application of the logistic regression model could provide quick and convenient POD risk identification to help improve the perioperative management of surgical patients because of its better sensitivity, fewer variables, and easier interpretability than the machine learning model.

Cerebral Autoregulation Assessment Using the Near Infrared Spectroscopy ‘NIRS-Only’ High Frequency Methodology in Critically Ill Patients: A Prospective Cross-Sectional Study

Impairments in cerebral autoregulation (CA) are related to poor clinical outcome. Near infrared spectroscopy (NIRS) is a non-invasive technique applied to estimate CA. Our general purpose was to study the clinical feasibility of a previously published ‘NIRS-only’ CA methodology in a critically ill intensive care unit (ICU) population and determine its relationship with clinical outcome. Bilateral NIRS measurements were performed for 1–2 h. Data segments of ten-minutes were used to calculate transfer function analyses (TFA) CA estimates between high frequency oxyhemoglobin (oxyHb) and deoxyhemoglobin (deoxyHb) signals. The phase shift was corrected for serial time shifts. Criteria were defined to select TFA phase plot segments (segments) with ‘high-pass filter’ characteristics. In 54 patients, 490 out of 729 segments were automatically selected (67%). In 34 primary neurology patients the median (q1–q3) low frequency (LF) phase shift was higher in 19 survivors compared to 15 non-survivors (13° (6.3–35) versus 0.83° (−2.8–13), p = 0.0167). CA estimation using the NIRS-only methodology seems feasible in an ICU population using segment selection for more robust and consistent CA estimations. The ‘NIRS-only’ methodology needs further validation, but has the advantage of being non-invasive without the need for arterial blood pressure monitoring.

Association of blood pressure variability with short- and long-term cognitive outcomes in patients with critical illness

BACKGROUND

Blood pressure variability (BPV), a modifiable risk factor, can compromise cerebral perfusion in critically ill patients. We studied the association between BPV in the intensive care unit (ICU) and short- and long-term cognitive outcomes.

METHODS

All patients were ≥50 years old. The short-term cognitive end points were delirium and depressed alertness without delirium. The long-term outcome was change in the slope of longitudinal cognitive scores. Primary BPV measure was average real variability (ARV) of systolic blood pressure. Associations were assessed with multivariable multinominal logistic regression and linear mixed effects models.

RESULTS

Of 794 patients (1130 admissions) 185 developed delirium and 274 developed depressed alertness. There was a dose-response association of 24-h systolic ARV with delirium (adjusted OR, 95% CI 2.15 per 5 mm Hg increase, 1.31-3.06, P < 0.017) and with depressed alertness (OR 1.89, 95% CI 1.18-3.03, P < 0.008). For 371 patients with available longitudinal cognitive scores, the decline in cognitive trajectory was accelerated after discharge (annual change OR -0.097, 95% CI -0.122 to -0.073). This acceleration increased with delirium (additional decline -0.132 [-0.233 to 0.030], P = 0.011). We found no significant association between BPV and post-ICU cognitive trajectory.

CONCLUSIONS

BPV was associated with increased likelihood of delirium in the ICU. Delirium, but not BPV, was associated with long-term cognitive decline.

Perioperative neurocognitive disorders: A narrative review focusing on diagnosis, prevention, and treatment

Perioperative neurocognitive disorders (NCDs) refer to neurocognitive abnormalities detected during the perioperative periods, including preexisting cognitive impairment, preoperative delirium, delirium occurring up to 7 days after surgery, delayed neurocognitive recovery, and postoperative NCD. The Diagnostic and Statistical Manual of Mental Disorders‐5th edition (DSM‐5) is the golden standard for diagnosing perioperative NCDs. Given the impracticality of using the DSM‐5 by non‐psychiatric practitioners, many diagnostic tools have been developed and validated for different clinical scenarios. The etiology of perioperative NCDs is multifactorial and includes predisposing and precipitating factors. Identifying these risk factors is conducive to preoperative risk stratification and perioperative risk reduction. Prevention for perioperative NCDs should include avoiding possible contributors and implementing nonpharmacologic and pharmacological interventions. The former generally includes avoiding benzodiazepines, anticholinergics, prolonged liquid fasting, deep anesthesia, cerebral oxygen desaturation, and intraoperative hypothermia. Nonpharmacologic measures include preoperative cognitive prehabilitation, comprehensive geriatric assessment, implementing fast‐track surgery, combined use of regional block, and sleep promotion. Pharmacological measures including dexmedetomidine, nonsteroidal anti‐inflammatory drugs, and acetaminophen are found to have beneficial effects. Nonpharmacological treatments are the first‐line measures for established perioperative NCDs. Pharmacological treatments are still limited to severely agitated or distressed patients.

Clinical values of cerebral oxygen saturation monitoring in patients with septic shock

OBJECTIVES

Sepsis associated encephalopathy (SAE) is a common neurological complication of sepsis. Delirium is a common symtom of SAE. The pathophysiology of SAE is still unclear, but several likely mechanisms have been proposed, such as mitochondrial and endothelial dysfunction, neurotransmission disturbances, derangements of calcium homeostasis, cerebral microcirculation dysfunction, and brain hypoperfusion. Near-infrared spectroscopy (NIRS) is a non-invasive measure for regional cerebral oxygen saturation (rSO2), which has attracted more attention these years. Previous studies have reported that abnormal NIRS values were associated with delirium in critically ill patients. Blood pressure management according to NIRS monitoring improved the organ perfusion and prognosis of patients. This study aimed to observe the dynamic changes of rSO2 using NIRS in septic shock patients, and analyze the relationship between them.

METHODS

A total of 48 septic patients who admitted to the intensive care unit (ICU) of Xiangya Hospital, Central South University from August 2017 to May 2018, were retrospectively study. Septic shock was diagnosed according to the criteria of sepsis 3.0 defined by the American Association of Critical Care Medicine and the European Society of Critical Care Medicine. NIRS monitoring was performed during the first 6 hours admitted to ICU with sensors placed on the bilateral forehead of patients. The maximum (rSO2max), minimum (rSO2min), mean value, and the variation rate during the first 6 hours of monitor were recorded. The following data were collected upon the first 24 h after admission to the ICU: The baseline data of patients, laboratory examination results (routine blood test, liver and renal function, blood gas analysis, indicators of infection, and coagulation function), scoring system results [Glasgow Coma Scale (GCS), Acute Physiology and Chronic Health Evaluation II (APACHE II) and Sequential Organ Failure Assessment (SOFA)]. Delirium was screened with the Confusion Assessment Method for ICU (CAM-ICU). The length of time on mechanical ventilation (MV), length of ICU-stay, length of hospital-stay, and 28-day mortality were also recorded. The primary outcome was 28-day mortality, and the secondary outcomes were the incidence of delirium, length of ICU-stay, and length of hospital-stay. The differences between survivors and non-survivors, and patients with or without delirium were analyzed, and the risk factors for delirium were assessed. The performance of rSO2-related indexes (rSO2max, rSO2min, the mean value, and the variation rate of rSO2) in predicting 28-day mortality and delirium was analyzed and the cutoff values were determined.

RESULTS

The overall 28-day mortality of septic shock patients was 47.92% (23/48), and the incidence of delirium was 18.75% (9/48). The rSO2min was significantly lower in the non-survivors than the survivors (P=0.042). The variation rate of rSO2 was higher in patients with delirium than those without delirium (P=0.006). The independent risk factors for delirium were rSO2max, the level of direct bilirubin (DBIL), and whether achieved the 6-hour bundle. To predict the 28-day mortality of septic shock patients, the area under the receiver operating characteristic curve (AUROC) for rSO2max, rSO2min, the mean value and the variation rate of rSO2 were 0.616, 0.606, 0.623, and 0.504, respectively. To predict the incidence of delirium, AUROC for rSO2max, rSO2min, the mean value and the variation rate of rSO2 were 0.682, 0.617, 0.580, and 0.501, respectively. The best cutoff value for rSO2max in predicting delirium was 77.5% (sensitivity was 0.444, specificity was 0.897). The best cutoff value for rSO2min in predicting delirium was 65.5% (sensitivity was 0.556, specificity was 0.744).

CONCLUSIONS

Cerebral anoxia and hyperoxia, as well as the large fluctuation of cerebral oxygen saturation are important factors that affect the outcomes and the incidence of delirium in septic shock patients, which should be paid attention to in clinical practice. Dynamic monitoring of cerebral oxygen saturation and maintain its stability may be of great significance in patients with septic shock.

Urinary albumin creatinine ratio associated with postoperative delirium in elderly patients undergoing elective non-cardiac surgery: A prospective observational study

Introduction

The blood‐brain barrier (BBB) disruption contributes to postoperative delirium, but cost‐effective and non‐invasive assessment of its permeability is not practicable in the clinical settings. Urine albumin to creatinine ratio (UACR), reflecting systemic vascular endothelial dysfunction, may be a prognostic and predictive factor associated with postoperative delirium. The aim was to analyze the relationship between UACR and postoperative delirium in elderly patients undergoing elective non‐cardiac surgery.

Materials and methods

Through stratified random sampling, a cohort of 408 individuals aged 60 years and older scheduled for elective non‐cardiac surgery were included between February and August 2019 in the single‐center, prospective, observational study. The presence of delirium was assessed using the Confusion Assessment Method (CAM) or Confusion Assessment Method for the ICU (CAM‐ICU) on the day of surgery, at 2 h after the surgery ending time and on the first 3 consecutive days with repeated twice‐daily, with at least 6‐h intervals between assessments. Urine samples were collected on one day before surgery, and 1st day and 3rd day after surgery. The primary outcome was the presence of postoperative delirium, and association of the level of UACR with postoperative delirium was evaluated with unadjusted/adjusted analyses and multivariable logistic regression.

Results

Postoperative delirium was observed in 26.75% (107 of 400) of patients within 3 days post‐surgery. UACR‐Pre (OR, 1.30; 95% CI, 1.14–1.49, p < 0.001), UACR‐POD1 (OR, 1.20; 95% CI, 1.13–1.27, p < 0.001), and UACR‐POD3 (OR, 1.14; 95% CI, 1.08–1.20, p < 0.001) between the delirium and non‐delirium groups show a significant difference, even after adjusting for age, education levels, and other factors.

Conclusion

As the marker of endothelial dysfunction, the high perioperative UACR value may be linked to the postoperative delirium in elderly patients undergoing elective non‐cardiac surgery.

Identifying neurocognitive outcomes and cerebral oxygenation in critically ill adults on acute kidney replacement therapy in the intensive care unit: the INCOGNITO-AKI study protocol

INTRODUCTION

Initiation of acute kidney replacement therapy (KRT) is common in critically ill adults admitted to the intensive care unit (ICU), and associated with increased morbidity and mortality. KRT has been linked to poor neurocognitive outcomes, leading to reduced quality of life and increased utilisation of healthcare resources. Adults on dialysis in the ICU may be particularly at risk of neurocognitive impairment, as survivors of critical illness are already predisposed to developing cerebrovascular disease and cognitive dysfunction long-term relative to healthy controls. Regional cerebral oxygen saturation may provide a critical early marker of long-term neurocognitive impairment in this population. This study aims to understand cerebral oxygenation in patients undergoing KRT (continuous or intermittent) in the ICU. These findings will be correlated with long-term cognitive and functional outcomes, and structural brain pathology.

METHODS AND ANALYSIS

108 patients scheduled to undergo treatment for acute kidney injury with KRT in the Kingston Health Sciences Centre ICU will be recruited into this prospective observational study. Enrolled patients will be assessed with intradialytic cerebral oximetry using near infrared spectroscopy. Delirium will be assessed daily with the Confusion Assessment Method-ICU (CAM-ICU) and severity quantified as cumulative CAM-ICU-7 scores. Neurocognitive impairment will be assessed at 3 and 12 months after hospital discharge using the Kinarm and Repeatable Battery for the Assessment of Neuropsychological Status. Structural brain pathology on MRI will also be measured at the same timepoints. Driving safety, adverse events and medication adherence will be assessed at 12 months to evaluate the impact of neurocognitive impairment on functional outcomes.

ETHICS AND DISSEMINATION

This study is approved by the Queen's University Health Sciences/Affiliated Teaching Hospitals Research Ethics Board (DMED-2424-20). Results will be presented at critical care conferences, and a lay summary will be provided to patients in their preferred format.

TRIAL REGISTRATION NUMBER

NCT04722939.

Delirium, Cerebral Perfusion, and High-Frequency Vital-Sign Monitoring in the Critically Ill. The CONFOCAL-2 Feasibility Study

Rationale: Studies suggest that reduced cerebral perfusion may contribute to delirium development in the intensive care unit (ICU). However, evidence is limited because of factors including small sample size and limited inclusion of covariates.Objectives: To assess the feasibility of a multicenter prospective observational study using a multimodal data collection platform. Feasibility was assessed by enrollment, data-capture, and follow-up rates. The full study will aim to assess the association between noninvasively derived surrogate markers of cerebral perfusion, delirium development, and long-term cognitive outcomes in critically ill patients.Methods: Adult patients in the ICU were enrolled if they had shock and/or respiratory failure requiring invasive mechanical ventilation for >24 hours. For the first 72 hours, a near-infrared spectroscopic sensor was placed on the forehead to continuously monitor regional cerebral oxygenation (rSo₂) and high-frequency (1 Hz) vital signs were concurrently captured via an arterial line. Cerebral perfusion was estimated using three variables, including mean rSo₂, duration of disturbed autoregulation, and time/magnitude away from optimal mean arterial pressure (MAP). Patients were screened for delirium in the ICU and ward daily for up to 30 days. Cognitive function was assessed 3 and 12 months after ICU admission to identify cognitive impairment.Results: Fifty-nine patients were enrolled across four sites in 1 year. Data-capture rates varied across modalities but exceeded 80% for rSo₂, blood gas, and delirium data capture. Vital-sign capture and 3-month follow-up rates were lower at 53% and 55%, respectively. Eighty-three percent (49 of 59) of patients experienced delirium, with a median severity of 0.56 in the ICU. Mean physiological (±standard deviation) values were: rSo₂ (70.4% ± 7.0%), heart rate (83.9 ± 16.45 beats/min), MAP (76.4 ± 12.8 mm Hg), peripheral oxygenation saturation (96.5% ± 2.1%), proportion of recording time spent with disturbed autoregulation (10.1% ± 7.3%) and proportion of area under the curve outside optimal MAP (39.6% ± 22.4%). Thirty-two (54%) individuals had cerebral autoregulation curves where a targeted optimal MAP was identified. Barriers to data collection included missing vital-sign data and low follow-up rates.Conclusions: Given our current protocol, a multicenter study examining the association between cerebral oxygenation, delirium, and long-term cognitive impairment is not feasible. However, by performing an early assessment of feasibility, we identified strategies to increase capture rates to ensure success as the study begins the next phase of study recruitment.Clinical trial registered with clinicaltrials.gov (NCT03141619).

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

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

Cerebral autoregulation in the operating room and intensive care unit after cardiac surgery

BACKGROUND

Cerebral autoregulation monitoring is a proposed method to monitor perfusion during cardiac surgery. However, limited data exist from the ICU as prior studies have focused on intraoperative measurements. Our objective was to characterise cerebral autoregulation during surgery and early ICU care, and as a secondary analysis to explore associations with delirium.

METHODS

In patients undergoing cardiac surgery (n=134), cerebral oximetry values and arterial BP were monitored and recorded until the morning after surgery. A moving Pearson's correlation coefficient between mean arterial proessure (MAP) and near-infrared spectroscopy signals generated the cerebral oximetry index (COx). Three metrics were derived: (1) globally impaired autoregulation, (2) MAP time and duration outside limits of autoregulation (MAP dose), and (3) average COx. Delirium was assessed using the 3-Minute Diagnostic Interview for CAM-defined Delirium (3D-CAM) and the Confusion Assessment Method for the ICU (CAM-ICU). Autoregulation metrics were compared using χ² and rank-sum tests, and associations with delirium were estimated using regression models, adjusted for age, bypass time, and logEuroSCORE.

RESULTS

The prevalence of globally impaired autoregulation was higher in the operating room vs ICU (40% vs 13%, P<0.001). The MAP dose outside limits of autoregulation was similar in the operating room and ICU (median 16.9 mm Hg×h; inter-quartile range [IQR] 10.1-38.8 vs 16.9 mm Hg×h; IQR 5.4-35.1, P=0.20). In exploratory adjusted analyses, globally impaired autoregulation in the ICU, but not the operating room, was associated with delirium. The MAP dose outside limits of autoregulation in the operating room and ICU was also associated with delirium.

CONCLUSIONS

Metrics of cerebral autoregulation are altered in the ICU, and may be clinically relevant with respect to delirium. Further studies are needed to investigate these findings and determine possible benefits of autoregulation-based MAP targeting in the ICU.

The Use of Near-Infrared Spectroscopy and/or Transcranial Doppler as Non-Invasive Markers of Cerebral Perfusion in Adult Sepsis Patients With Delirium: A Systematic Review

Background:

Several studies have previously reported the presence of altered cerebral perfusion during sepsis. However, the role of non-invasive neuromonitoring, and the impact of altered cerebral perfusion, in sepsis patients with delirium remains unclear.

Methods:

We performed a systematic review of studies that used near-infrared spectroscopy (NIRS) and/or transcranial Doppler (TCD) to assess adults (≥18 years) with sepsis and delirium. From study inception to July 28, 2020, we searched the following databases: Ovid MedLine, Embase, Cochrane Library, and Web of Science.

Results:

Of 1546 articles identified, 10 met our inclusion criteria. Although NIRS-derived regional cerebral oxygenation was consistently lower, this difference was only statistically significant in one study. TCD-derived cerebral blood flow velocity was inconsistent across studies. Importantly, both impaired cerebral autoregulation during sepsis and increased cerebrovascular resistance were associated with delirium during sepsis. However, the heterogeneity in NIRS and TCD devices, duration of recording (from 10 seconds to 72 hours), and delirium assessment methods (e.g., electronic medical records, confusion assessment method for the intensive care unit), precluded meta-analysis.

Conclusion:

The available literature demonstrates that cerebral perfusion disturbances may be associated with delirium in sepsis. However, future investigations will require consistent definitions of delirium, delirium assessment training, harmonized NIRS and TCD assessments (e.g., consistent measurement site and length of recording), as well as the quantification of secondary and tertiary variables (i.e., Cox, Mxa, MAP_OPT), in order to fully assess the relationship between cerebral perfusion and delirium in patients with sepsis.

Cerebral Blood Flow Deviations in Critically Ill Patients: Potential Insult Contributing to Ischemic and Hyperemic Injury

Background: Ischemic and hyperemic injury have emerged as biologic mechanisms that contribute to cognitive impairment in critically ill patients. Spontaneous deviations in cerebral blood flow (CBF) beyond ischemic and hyperemic thresholds may represent an insult that contributes to this brain injury, especially if they accumulate over time and coincide with impaired autoregulation.

Methods: We used transcranial Doppler to measure the proportion of time that CBF velocity (CBFv) deviated beyond previously reported ischemic and hyperemic thresholds in a cohort of critically ill patients with respiratory failure and/or shock within 48 h of ICU admission. We also assessed whether these CBFv deviations were more common during periods of impaired dynamic autoregulation, and whether they are explained by concurrent variations in mean arterial pressure (MAP) and end-tidal PCO₂ (PetCO₂).

Results: We enrolled 12 consecutive patients (three females) who were monitored for a mean duration of 462.6 ± 39.8 min. Across patients, CBFv deviated by more than 20–30% from its baseline for 17–24% of the analysis time. These CBFv deviations occurred equally during periods of preserved and impaired autoregulation, while concurrent variations in MAP and PetCO₂ explained only 13–21% of these CBFv deviations.

Conclusion: CBFv deviations beyond ischemic and hyperemic thresholds are common in critically ill patients with respiratory failure or shock. These deviations occur irrespective of the state of dynamic autoregulation and are not explained by changes in MAP and CO₂. Future studies should explore mechanisms responsible for these CBFv deviations and establish whether their cumulative burden predicts poor neurocognitive outcomes.

Near-Infrared Spectroscopy to Assess Cerebral Autoregulation and Optimal Mean Arterial Pressure in Patients With Hypoxic-Ischemic Brain Injury: A Prospective Multicenter Feasibility Study

Supplemental Digital Content is available in the text.

We provide preliminary multicenter data to suggest that recruitment and collection of physiologic data necessary to quantify cerebral autoregulation and individualized blood pressure targets are feasible in postcardiac arrest patients. We evaluated the feasibility of a multicenter protocol to enroll patients across centers, as well as collect continuous recording (≥ 80% of monitoring time) of regional cerebral oxygenation and mean arterial pressure, which is required to quantify cerebral autoregulation, using the cerebral oximetry index, and individualized optimal mean arterial pressure thresholds. Additionally, we conducted an exploratory analysis to assess if an increased percentage of monitoring time where mean arterial pressure was greater than or equal to 5 mm Hg below optimal mean arterial pressure, percentage of monitoring time with dysfunctional cerebral autoregulation (i.e., cerebral oximetry index ≥ 0.3), and time to return of spontaneous circulation were associated with an unfavorable neurologic outcome (i.e., 6-mo Cerebral Performance Category score ≥ 3).

Pathomechanisms of Non-Traumatic Acute Brain Injury in Critically Ill Patients

Delirium, an acute alteration in mental status characterized by confusion, inattention and a fluctuating level of arousal, is a common problem in critically ill patients. Delirium prolongs hospital stay and is associated with higher mortality. The pathophysiology of delirium has not been fully elucidated. Neuroinflammation and neurotransmitter imbalance seem to be the most important factors for delirium development. In this review, we present the most important pathomechanisms of delirium in critically ill patients, such as neuroinflammation, neurotransmitter imbalance, hypoxia and hyperoxia, tryptophan pathway disorders, and gut microbiota imbalance. A thorough understanding of delirium pathomechanisms is essential for effective prevention and treatment of this underestimated pathology in critically ill patients.

Effect of Targeting Mean Arterial Pressure During Cardiopulmonary Bypass by Monitoring Cerebral Autoregulation on Postsurgical Delirium Among Older Patients: A Nested Randomized Clinical Trial

Importance

Delirium occurs in up to 52% of patients after cardiac surgery and may result from changes in cerebral perfusion. Using intraoperative cerebral autoregulation monitoring to individualize and optimize cerebral perfusion may be a useful strategy to reduce the incidence of delirium after cardiac surgery.

Objective

To determine whether targeting mean arterial pressure during cardiopulmonary bypass (CPB) using cerebral autoregulation monitoring reduces the incidence of delirium compared with usual care.

Design, Setting, and Participants

This randomized clinical trial nested within a larger trial enrolled patients older than 55 years who underwent nonemergency cardiac surgery at a single US academic medical center between October 11, 2012, and May 10, 2016, and had a high risk for neurologic complications. Patients, physicians, and outcome assessors were masked to the assigned intervention. A total of 2764 patients were screened, and 199 were eligible for analysis in this study.

Intervention

In the intervention group, the patient's lower limit of cerebral autoregulation was identified during surgery before CPB. On CPB, the patient's mean arterial pressure was targeted to be greater than that patient's lower limit of autoregulation. In the control group, mean arterial pressure targets were determined according to institutional practice.

Main Outcomes and Measures

The main outcome was any incidence of delirium on postoperative days 1 through 4, as adjudicated by a consensus expert panel.

Results

Among the 199 participants in this study, mean (SD) age was 70.3 (7.5) years and 150 (75.4%) were male. One hundred sixty-two (81.4%) were white, 26 (13.1%) were black, and 11 (5.5%) were of other race. Of 103 patients randomized to usual care, 94 were analyzed, and of 102 patients randomized to the intervention 105 were analyzed. Excluding 5 patients with coma, delirium occurred in 48 of the 91 patients (53%) in the usual care group compared with 39 of the 103 patients (38%) in the intervention group (P = .04). The odds of delirium were reduced by 45% in patients randomized to the autoregulation group (odds ratio, 0.55; 95% CI, 0.31-0.97; P = .04).

Conclusions and Relevance

The results of this study suggest that optimizing mean arterial pressure to be greater than the individual patient's lower limit of cerebral autoregulation during CPB may reduce the incidence of delirium after cardiac surgery, but further study is needed.

Trial Registration

ClinicalTrials.gov identifier: NCT00981474.

Road to recovery: a study protocol quantifying neurological outcome in cardiac surgery patients and the role of cerebral oximetry

INTRODUCTION

Patients undergoing cardiac surgery may experience both short-term and long-term postoperative neurological problems. However, the underlying cause of this impairment is unclear. Regional cerebral oxygen saturation (rSO₂) levels may play a role in the development of acute dysfunction, known as postoperative delirium, in addition to longer term outcomes after cardiac surgery. Yet the degree of impairment has been difficult to define, partly due to subjective methods of assessments. This study aims to fill this knowledge gap by determining the relationship between rSO₂, postoperative delirium and long-term neurological outcome after cardiac surgery using quantitative robotic technology.

METHODS AND ANALYSIS

95 patients scheduled for elective cardiac surgery will be recruited for this single-centre prospective observational study. Patients will be assessed before as well as 3 and 12 months after their surgery using the Kinarm End-Point Lab and standardised tasks. Intraoperatively, rSO₂ and other haemodynamic data will be collected for the duration of the procedure. Following their operation, patients will also be screened daily for delirium during their hospital stay.

ETHICS AND DISSEMINATION

This study has been approved by the Health Sciences Research Ethics Board at Queen's University (DMED-1672-14). The results of this study will be published in a peer-review journal and presented at international and/or national conferences as poster or oral presentations. Participants wishing to know the results of this study will be contacted directly on data publication.

TRIAL REGISTRATION NUMBER

NCT04081649.

Effect of Targeting Mean Arterial Pressure During Cardiopulmonary Bypass by Monitoring Cerebral Autoregulation on Postsurgical Delirium Among Older Patients: A Nested Randomized Clinical Trial

Importance

Delirium occurs in up to 52% of patients after cardiac surgery and may result from changes in cerebral perfusion. Using intraoperative cerebral autoregulation monitoring to individualize and optimize cerebral perfusion may be a useful strategy to reduce the incidence of delirium after cardiac surgery.

Objective

To determine whether targeting mean arterial pressure during cardiopulmonary bypass (CPB) using cerebral autoregulation monitoring reduces the incidence of delirium compared with usual care.

Design, Setting, and Participants

This randomized clinical trial nested within a larger trial enrolled patients older than 55 years who underwent nonemergency cardiac surgery at a single US academic medical center between October 11, 2012, and May 10, 2016, and had a high risk for neurologic complications. Patients, physicians, and outcome assessors were masked to the assigned intervention. A total of 2764 patients were screened, and 199 were eligible for analysis in this study.

Intervention

In the intervention group, the patient's lower limit of cerebral autoregulation was identified during surgery before CPB. On CPB, the patient's mean arterial pressure was targeted to be greater than that patient's lower limit of autoregulation. In the control group, mean arterial pressure targets were determined according to institutional practice.

Main Outcomes and Measures

The main outcome was any incidence of delirium on postoperative days 1 through 4, as adjudicated by a consensus expert panel.

Results

Among the 199 participants in this study, mean (SD) age was 70.3 (7.5) years and 150 (75.4%) were male. One hundred sixty-two (81.4%) were white, 26 (13.1%) were black, and 11 (5.5%) were of other race. Of 103 patients randomized to usual care, 94 were analyzed, and of 102 patients randomized to the intervention 105 were analyzed. Excluding 5 patients with coma, delirium occurred in 48 of the 91 patients (53%) in the usual care group compared with 39 of the 103 patients (38%) in the intervention group (P = .04). The odds of delirium were reduced by 45% in patients randomized to the autoregulation group (odds ratio, 0.55; 95% CI, 0.31-0.97; P = .04).

Conclusions and Relevance

The results of this study suggest that optimizing mean arterial pressure to be greater than the individual patient's lower limit of cerebral autoregulation during CPB may reduce the incidence of delirium after cardiac surgery, but further study is needed.

Trial Registration

ClinicalTrials.gov identifier: NCT00981474.

Assessing the relationship between near-infrared spectroscopy-derived regional cerebral oxygenation and neurological dysfunction in critically ill adults: a prospective observational multicentre protocol, on behalf of the Canadian Critical Care Trials Group

INTRODUCTION

Survivors of critical illness frequently exhibit acute and chronic neurological complications. The underlying aetiology of this dysfunction remains unknown but may be associated with cerebral ischaemia. This study will use near-infrared spectroscopy to non-invasively quantify regional cerebral oxygenation (rSO₂) to assess the association between poor rSO₂ during the first 72 hours of critical illness with delirium severity, as well as long-term sensorimotor and cognitive impairment among intensive care unit (ICU) survivors. Further, the physiological determinants of rSO₂ will be examined.

METHODS AND ANALYSIS

This multicentre prospective observational study will consider adult patients (≥18 years old) eligible for enrolment if within 24 hours of ICU admission, they require mechanical ventilation and/or vasopressor support. For 72 hours, rSO₂ will be continuously recorded, while vital signs (eg, heart rate) and peripheral oxygenation saturation will be concurrently captured with data monitoring software. Arterial and central venous gases will be sampled every 12 hours for the 72 hours recording period and will include: pH, PaO2, PaCO2, and haemoglobin concentration. Participants will be screened daily for delirium with the confusion assessment method (CAM)-ICU, whereas the brief-CAM will be used on the ward. At 3 and 12 months post-ICU discharge, neurological function will be assessed with the Repeatable Battery for the Assessment of Neuropsychological Status and KINARM sensorimotor and cognitive robot-based behavioural tasks.

ETHICS AND DISSEMINATION

The study protocol has been approved in Ontario by a central research ethics board (Clinical Trials Ontario); non-Ontario sites will obtain local ethics approval. The study will be conducted under the guidance of the Canadian Critical Care Trials Group (CCCTG) and the results of this study will be presented at national meetings of the CCCTG for internal peer review. Results will also be presented at national/international scientific conferences. On completion, the study findings will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03141619.