Optimizing Mean Arterial Pressure in Acutely Comatose Patients Using Cerebral Autoregulation Multimodal Monitoring With Near-Infrared Spectroscopy.

OBJECTIVES: This study investigated whether comatose patients with greater duration and magnitude of clinically observed mean arterial pressure outside optimal mean arterial blood pressure have worse outcomes than those with mean arterial blood pressure closer to optimal mean arterial blood pressure calculated by bedside multimodal cerebral autoregulation monitoring using near-infrared spectroscopy. DESIGN: Prospective observational study. SETTING: Neurocritical Care Unit of the Johns Hopkins Hospital. SUBJECTS: Acutely comatose patients secondary to brain injury. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The cerebral oximetry index was continuously monitored with near-infrared spectroscopy for up to 3 days. Optimal mean arterial blood pressure was defined as that mean arterial blood pressure at the lowest cerebral oximetry index (nadir index) for each 24-hour period of monitoring. Kaplan-Meier analysis and proportional hazard regression models were used to determine if survival at 3 months was associated with a shorter duration of mean arterial blood pressure outside optimal mean arterial blood pressure and the absolute difference between clinically observed mean arterial blood pressure and optimal mean arterial blood pressure. A total 91 comatose patients were enrolled in the study. The most common etiology was intracerebral hemorrhage. Optimal mean arterial blood pressure could be calculated in 89 patients (97%), and the median optimal mean arterial blood pressure was 89.7 mm Hg (84.6-100 mm Hg). In multivariate proportional hazard analysis, duration outside optimal mean arterial blood pressure of greater than 80% of monitoring time (adjusted hazard ratio, 2.13; 95% CI, 1.04-4.41; p = 0.04) and absolute difference between clinically observed mean arterial blood pressure and optimal mean arterial blood pressure of more than 10 mm Hg (adjusted hazard ratio, 2.44; 95% CI, 1.21-4.92; p = 0.013) were independently associated with mortality at 3 months, after adjusting for brain herniation, admission Glasgow Coma Scale, duration on vasopressors and midline shift at septum. CONCLUSIONS: Comatose neurocritically ill adults with an absolute difference between clinically observed mean arterial blood pressure and optimal mean arterial blood pressure greater than 10 mm Hg and duration outside optimal mean arterial blood pressure greater than 80% had increased mortality at 3 months. Noninvasive near-infrared spectroscopy-based bedside calculation of optimal mean arterial blood pressure is feasible and might be a promising tool for cerebral autoregulation oriented-therapy in neurocritical care patients.

Determining the Upper and Lower Limits of Cerebral Autoregulation With Cerebral Oximetry Autoregulation Curves: A Case Series.

OBJECTIVE: Critical care guidelines recommend a single target value for mean arterial blood pressure in critically ill patients. However, growing evidence regarding cerebral autoregulation challenges this concept and supports individualizing mean arterial blood pressure targets to prevent brain and kidney hypo- or hyperperfusion. Regional cerebral oxygen saturation derived from near-infrared spectroscopy is an acceptable surrogate for cerebral blood flow and has been validated to measure cerebral autoregulation. This study suggests a novel mechanism to construct autoregulation curves based on near-infrared spectroscopy-measured cerebral oximetry. DESIGN: Case-series study. SETTING: Neurocritical care unit in a tertiary medical center. PATIENTS: Patients with acute neurologic injury and Glasgow coma scale score less than or equal to 8. MEASUREMENTS AND MAIN RESULTS: Autoregulation curves were plotted using the fractional-polynomial model in Stata after multimodal continuous monitoring of regional cerebral oxygen saturation and mean arterial blood pressure. Individualized autoregulation curves of seven patients exhibited varying upper and lower limits of autoregulation and provided useful clinical information on the autoregulation trend (curves moving to the right or left during the acute coma period). The median lower and upper limits of autoregulation were 86.5 mm Hg (interquartile range, 74-93.5) and 93.5 mm Hg (interquartile range, 83-99), respectively. CONCLUSIONS: This case-series study showed feasibility of delineating real trends of the cerebral autoregulation plateau and direct visualization of the cerebral autoregulation curve after at least 24 hours of recording without manipulation of mean arterial blood pressure by external stimuli. The integration of multimodal monitoring at the bedside with cerebral oximetry provides a noninvasive method to delineate daily individual cerebral autoregulation curves.

Cerebral Autoregulation-oriented Therapy at the Bedside: A Comprehensive Review.

This comprehensive review summarizes the evidence regarding use of cerebral autoregulation-directed therapy at the bedside and provides an evaluation of its impact on optimizing cerebral perfusion and associated functional outcomes. Multiple studies in adults and several in children have shown the feasibility of individualizing mean arterial blood pressure and cerebral perfusion pressure goals by using cerebral autoregulation monitoring to calculate optimal levels. Nine of these studies examined the association between cerebral perfusion pressure or mean arterial blood pressure being above or below their optimal levels and functional outcomes. Six of these nine studies (66%) showed that patients for whom median cerebral perfusion pressure or mean arterial blood pressure differed significantly from the optimum, defined by cerebral autoregulation monitoring, were more likely to have an unfavorable outcome. The evidence indicates that monitoring of continuous cerebral autoregulation at the bedside is feasible and has the potential to be used to direct blood pressure management in acutely ill patients.

Relation between bispectral index measurements of anesthetic depth and postoperative mortality: a meta-analysis of observational studies.

INTRODUCTION: The association between anesthesia depth and mortality is still controversial. There are a number of narrative reviews on this topic that affirm this association, but their conclusions were based only on qualitative analyses. The aim of this meta-analysis of observational studies was to examine the potential association between depth of anesthesia as a low bispectral index (BIS) and mortality using appropriate quantitative methods. METHODS: The literature was systematically reviewed in three main electronic databases (MEDLINE, EMBASE, Google Scholar) to identify all articles from inception through December 2015 regarding the association between depth of anesthesia and mortality. Inclusion criteria were restricted to observational studies that used multivariable Cox proportional regression methodology and reported adjusted hazard ratios (aHR). Pooled effect size was measured using a random effects model. Subgroup analysis was performed post hoc based on follow-up duration (30 days and ≥ one year). RESULTS: Eight observational studies that included 40,317 patients were evaluated in this meta-analysis. The results showed a statistically significant association between the depth of anesthesia as measured by low BIS (< 40-45), and mortality (pooled aHR, 1.21; 95% CI, 1.07 to 1.38; P = 0.003). Subgroup analysis showed that the association between depth of anesthesia (measured by low BIS) and mortality was significant for studies with a follow-up duration of ≥ one year (n = 23,347; pooled aHR, 1.10; 95% CI, 1.00 to 1.21; P = 0.04) but was not significant for studies with a follow-up duration of 30 days (n = 16,970; pooled aHR, 1.38; 95% CI = 0.81 to 2.36; P = 0.24). CONCLUSION: Existing observational studies support a significant association between depth of anesthesia (as measured by BIS) and long-term mortality (≥ one year), although it was without statistical significance at 30 days. Larger prospective, randomized trials are necessary to establish a definitive conclusion about whether this association represents true causality or is an epiphenomenon.

Glasgow Coma Scale Score Fluctuations are Inversely Associated With a NIRS-based Index of Cerebral Autoregulation in Acutely Comatose Patients.

BACKGROUND: The Glasgow Coma Scale (GCS) is an essential coma scale in critical care for determining the neurological status of patients and for estimating their long-term prognosis. Similarly, cerebral autoregulation (CA) monitoring has shown to be an accurate technique for predicting clinical outcomes. However, little is known about the relationship between CA measurements and GCS scores among neurological critically ill patients. This study aimed to explore the association between noninvasive CA multimodal monitoring measurements and GCS scores. METHODS: Acutely comatose patients with a variety of neurological injuries admitted to a neurocritical care unit were monitored using near-infrared spectroscopy-based multimodal monitoring for up to 72 hours. Regional cerebral oxygen saturation (rScO2), cerebral oximetry index (COx), GCS, and GCS motor data were measured hourly. COx was calculated as a Pearson correlation coefficient between low-frequency changes in rScO2 and mean arterial pressure. Mixed random effects models with random intercept was used to determine the relationship between hourly near-infrared spectroscopy-based measurements and GCS or GCS motor scores. RESULTS: A total of 871 observations (h) were analyzed from 57 patients with a variety of neurological conditions. Mean age was 58.7±14.2 years and the male to female ratio was 1:1.3. After adjusting for hemoglobin and partial pressure of carbon dioxide in arterial blood, COx was inversely associated with GCS (ß=-1.12, 95% confidence interval [CI], -1.94 to -0.31, P=0.007) and GCS motor score (ß=-1.06, 95% CI, -2.10 to -0.04, P=0.04). In contrast rScO2 was not associated with GCS (ß=-0.002, 95% CI, -0.01 to 0.01, P=0.76) or GCS motor score (ß=-0.001, 95% CI, -0.01 to 0.01, P=0.84). CONCLUSIONS: This study showed that fluctuations in GCS scores are inversely associated with fluctuations in COx; as COx increases (impaired autoregulation), more severe neurological impairment is observed. However, the difference in COx between high and low GCS is small and warrants further studies investigating this association. CA multimodal monitoring with COx may have the potential to be used as a surrogate of neurological status when the neurological examination is not reliable (ie, sedation and paralytic drug administration).

Epidemiology of septic meningitis associated with neuraxial anesthesia: a historical review and meta-analysis.

INTRODUCTION: Neuraxial anesthesia in the form of spinal and epidural are two of the most frequent forms of regional anesthesia. We aimed to describe and compare the relevant epidemiological, clinical and microbiological characteristics of all reported cases of septic meningitis associated with the use of spinal and epidural anesthetics. EVIDENCE ACQUISITION: We performed a systematic review of septic meningitis associated with neuraxial anesthesia. We included all relevant case-reports and observational studies in which authors described septic meningitis in association with spinal, epidural or combined neuraxial anesthesia using local anesthetics. EVIDENCE SYNTHESIS: A total of 234 cases of septic meningitis were reported following review of 71 case-report articles and 22 epidemiological studies. In total, there have been 199, 25 and 10 reported cases of septic meningitis associated to spinal, epidural and combined neuraxial anesthesia, respectively. The lack of use of surgical masks was the most common risk factor (41, 16.7%). Streptococcus salivarius was the most common bacteria (17.0%) related to spinal anesthesia and Staphylococcus aureus (26.7%) was the most common one related to epidural. The time to symptom onset was significantly reduced in spinal (median time, 24 hours IQR [8-72] vs. 96 hours IQR [84-240]; P=0.003) compared to epidural anesthesia. The overall mortality rate is 15.3% and 13.3% for reported cases related to spinal and epidural anesthesia, respectively. CONCLUSIONS: While the true incidence remains speculative, this review suggests that given increasing indications for spinals and epidurals, septic meningitis remains an important associated with neuraxial anesthesia.

A Comparison of Regional Versus General Anesthesia for Lumbar Spine Surgery: A Meta-Analysis of Randomized Studies.

BACKGROUND: General anesthesia (GA) is commonly used for lumbar spine surgery. The advantages of regional anesthesia (RA) for lumbar spine surgery, as compared with GA, remain unclear. The aim of this meta-analysis was to determine the impact of the type of anesthesia on intraoperative events, incidence of postoperative complications, and recovery time of patients undergoing lumbar spine surgery. METHODS: Major databases (PubMed, EMBASE, Cochrane library, ISI Web of Science, and Google Scholar) were systematically searched for randomized clinical trials comparing regional versus GA for lumbar spine surgery. Study-level characteristics, intraoperative events, and postoperative complications were extracted from the articles. Meta-analysis was performed using random-effect models. RESULTS: Fifteen randomized clinical trials comprising 961 patients were included in this meta-analysis. The use of RA for lumbar spine surgery was significantly associated with lower incidence of postoperative nausea and vomiting at 24 hours (risk ratio [RR]=0.42; 95% confidence interval [CI]=0.23-0.77, P=0.005), as well as lower length of stay (standardized mean difference [SMD]=-0.73; 95% CI=-1.17 to -0.29, P=0.001) and intraoperative blood loss (SMD=-1.24; 95% CI=-2.27 to -0.21, P=0.02). There was no statistically significant association with lower pain score (SMD=-0.47; 95% CI=-2.13 to 1.19, P=0.58), lower incidence of urinary retention (RR=1.16; 95% CI=0.73-1.86, P=0.53) or analgesic requirement (RR=0.87; 95% CI=0.64-1.18, P=0.37). CONCLUSIONS: In summary, RA has several advantageous characteristics, including lower incidence of postoperative nausea and vomiting, length of stay, and blood loss. Further well-designed studies with more sample size are needed to clarify the associations with possible neurological complications.