Reduced Brain/Serum Glucose Ratios Predict Cerebral Metabolic Distress and Mortality After Severe Brain Injury

Cerebral microdialysis demonstrates improvements in brain metabolism with cerebrospinal fluid diversion in spontaneous intracerebral hemorrhage

Background

Cerebral microdialysis (CMD) is an FDA-approved multimodal invasive monitoring technique that provides local brain metabolism measurements through continuous interstitial brain fluid sampling at the bedside. The past applications in traumatic brain injury and subarachnoid hemorrhage show that acute brain injury (ABI) can lead to a metabolic crisis reflected by changes in cerebral glucose, pyruvate, and lactate. However, limited literature exists on CMD in spontaneous intracerebral hemorrhage (ICH).

Case Description

A 45-year-old woman presented with a Glasgow Coma Scale of 8T and left frontal ICH with a 6 mm midline shift. She underwent craniotomy and ICH evacuation. Intraoperatively, CMD, brain tissue oxygenation (PbtO2), intracranial pressure (ICP), and cerebral blood flow (CBF) catheters were placed, targeted toward the peri-hematoma region. Postoperatively, ICP was normal; however, PbtO2, CBF, glucose, and lactate/ pyruvate ratio were abnormal. Due to concern for the metabolic crisis, poor examination, and hydrocephalus on computed tomography of the head (CTH), she underwent external ventricular drainage (EVD). Post-EVD, all parameters normalized (P < 0.05 on Student's t-test). Monitors were removed, and she was discharged to a nursing facility with a modified Rankin scale of 4.

Conclusion

Here, we demonstrate the safe implementation of CMD in ICH and the use of CMD in tandem with PbtO2/ICP/CBF to guide treatment in ICH. Despite a normal ICP, numerous cerebral metabolic derangements existed and improved after cerebrospinal fluid diversion. A normal ICP may not reflect underlying metabolic-substrate demands of the brain during ABI. CMD and PbtO2/CBF monitoring augment traditional ICP monitoring in brain injury. Further prospective studies will be needed to understand further the interplay between ICP, PbtO2, CBF, and CMD values in ABI.

Serum glucose/potassium ratio as a clinical risk factor for predicting the severity and prognosis of acute traumatic spinal cord injury

OBJECTIVE

Acute traumatic Spinal cord injury (TSCI) is a devastating event that causes severe sensory and motor impairments as well as autonomic dysfunction in patients, yet relevant clinical biomarkers have not been established. This study aimed to determine the significance of the serum glucose/potassium ratio (GPR) in evaluating TSCI severity and predicting prognosis.

METHODS

An analysis of 520 clinical records of acute TSCI patients from January 2012 to June 2022 was conducted. The relationships between serum GPR and The American Spinal Injury Association Impairment Scale (AIS) grade 6-month post-trauma prognosis and the admission AIS grade were analyzed. To evaluate the discriminatory ability, a receiver operating characteristic curve (ROC) analysis was used. All methods were performed in accordance with the relevant guidelines and regulations.

RESULTS

Based on the initial assessment of AIS grade, 256 (49.2%) patients were categorized into the severe TSCI group (AIS A-B), and there was a significant correlation between the severe TSCI group and serum GPR (p < 0.001). Serum GPR was reduced in an AIS grade-dependent manner (R = - 0.540, p < 0.001). Of the 520 patients, 262 (50.4%) patients were classified as having a poor prognosis according to the AIS grade at discharge. Serum GPR was also reduced in an AIS grade at discharge-dependent manner (R = - 0.599, p < 0.001), and was significantly higher in the poor prognosis group compared to the good prognosis group (p < 0.001). Poor prognosis was significantly associated with sex (p = 0.009), severity of TSCI (p < 0.001), location of TSCI (p < 0.001), surgical decompression (p < 0.018), body temperature (p < 0.001), heart rate (p < 0.001), systolic arterial pressure (SAP) (p < 0.001), diastolic arterial pressure (DAP) (p < 0.001), serum GPR (p < 0.001), serum glucose (p < 0.001), serum potassium (p < 0.001), and white blood cell count (p = 0.003). Multivariate logistic regression analysis showed a significant correlation between poor prognosis and serum GPR (p = 0.023). The ROC analysis showed the area under the curve of serum GPR to be a poor predictor of prognosis in TSCI patients at 0.842 (95% confidence interval, 0.808-0.875).

CONCLUSION

There was a significant relationship between serum GPR and admission injury severity and the 6-month prognosis of acute TSCI patients. Serum GPR serves as a readily available clinical risk factor for predicting the severity and 6-month prognosis of acute traumatic spinal cord injury, which holds potential clinical significance for patients with TSCI.

Management Strategies Based on Multi-Modality Neuromonitoring in Severe Traumatic Brain Injury

Secondary brain injury after neurotrauma is comprised of a host of distinct, potentially concurrent and interacting mechanisms that may exacerbate primary brain insult. Multimodality neuromonitoring is a method of measuring multiple aspects of the brain in order to understand the signatures of these different pathomechanisms and to detect, treat, or prevent potentially reversible secondary brain injuries. The most studied invasive parameters include intracranial pressure (ICP), cerebral perfusion pressure (CPP), autoregulatory indices, brain tissue partial oxygen tension, and tissue energy and metabolism measures such as the lactate pyruvate ratio. Understanding the local metabolic state of brain tissue in order to infer pathology and develop appropriate management strategies is an area of active investigation. Several clinical trials are underway to define the role of brain tissue oxygenation monitoring and electrocorticography in conjunction with other multimodal neuromonitoring information, including ICP and CPP monitoring. Identifying an optimal CPP to guide individualized management of blood pressure and ICP has been shown to be feasible, but definitive clinical trial evidence is still needed. Future work is still needed to define and clinically correlate patterns that emerge from integrated measurements of metabolism, pressure, flow, oxygenation, and electrophysiology. Pathophysiologic targets and precise critical care management strategies to address their underlying causes promise to mitigate secondary injuries and hold the potential to improve patient outcome. Advancements in clinical trial design are poised to establish new standards for the use of multimodality neuromonitoring to guide individualized clinical care.

The blood glucose-potassium ratio at admission predicts in-hospital mortality in patients with acute type A aortic dissection

Acute type A aortic dissection (ATAAD) is a serious cardiovascular emergency with high risk and mortality after surgery. Recent studies have shown that serum glucose-potassium ratio (GPR) is associated with the prognosis of cerebrovascular diseases. The purpose of this study was to investigate the relationship between GPR and in-hospital mortality in patients with ATAAD. From June 2019 to August 2021, we retrospectively analyzed the clinical data of 272 patients who underwent ATAAD surgery. According to the median value of GPR (1.74), the patients were divided into two groups. Univariate and multivariate logistic regression analysis were used to determine the risk factors of in-hospital mortality after ATAAD. In-hospital death was significantly more common in the high GPR group (> 1.74) (24.4% vs 13.9%; P = 0.027). The incidence of renal dysfunction in the low GPR group was significantly higher than that in the high GPR group (26.3% vs 14.8%: P = 0.019). After controlling for potential confounding variables and adjusting for multivariate logistic regression analysis, the results showed a high GPR (> 1.74) (AOR 4.70, 95% confidence interval (CI) 2.13-10.40; P =  < 0.001), lactic acid (AOR 1.14, 95% CI 1.03-1.26; P = 0.009), smokers (AOR 2.45, 95% CI 1.18-15.07; P = 0.039), mechanical ventilation (AOR 9.47, 95% CI 4.00-22.38; P =  < 0.001) was independent risk factor for in-hospital mortality in ATAAD patients, albumin (AOR 0.90, 95% CI 0.83-0.98; P = 0.014) was a protective factor for in-hospital prognosis. High GPR is a good predictor of in-hospital mortality after ATAAD surgery.

Neuroprotective Effects of Milrinone on Acute Traumatic Brain Injury

BACKGROUND

Traumatic brain injury is still an important health problem worldwide. Traumatic brain injury not only causes direct mechanical damage to the brain but also induces biochemical changes that lead to secondary nerve cell loss. In this study, we investigated the neuroprotective effect of milrinone after traumatic brain injury (TBI) in a rat model.

METHODS

Forty male Wistar albino rats, were used. Rats were divided into 4 groups: 1) sham, 2) TBI, 3) TBI + Ringers, and 4) TBI + Milrinone. In group 1 (sham), only craniotomy was performed. In group 2 (TBI), TBI was performed after craniotomy. In group 3 (TBI + Ringer), TBI was performed after craniotomy and intraperitoneal Ringers solution was given immediately afterward. Group 4 (TBI + Milrinone), TBI was performed after craniotomy, and milrinone was given 1.0 mg/kg milrinone intraperitoneally directly (0.5 mg/kg milrinone intraperitoneally again 24 hours, 48 hours, and 72 hours after trauma). Tests were performed for neurological and neurobehavioral functions. Immunohistochemistry and histopathology studies were performed.

RESULTS

In group 4 compared with group 2 and group 3 groups, tests for neurological functions and neurobehavioral functions were significantly better. In the milrinone treatment used in group 4, plasma and brain tissue tumor necrosis factor, 8-OH 2-deoxyguanosine , and interleukin 6 levels were significantly decreased, and increased plasma and tissue IL-10 levels were detected. Histopathological spinal cord injury and apoptotic index increased in groups 2 and 3, while significantly decreasing in group 4.

CONCLUSIONS

This study shows for the first time that the anti-inflammatory, antioxidant and antiapoptotic properties of milrinone may be neuroprotective after TBI.

The prognostic value of hyperglycemia in aneurysmal subarachnoid hemorrhage: a systematic review and meta-analysis

Recent studies have demonstrated that hyperglycemia may result in a poor prognosis following aneurysmal subarachnoid hemorrhage (aSAH). However, the association between hyperglycemia and the clinical outcome of aSAH has not been clearly established thus far. Therefore, we performed a systematic review and meta-analysis to investigate the association between hyperglycemia and the development of aSAH. We completed a literature search in four databases (PubMed, EMBASE, Cochrane Library, and Web of Science) up to November 1, 2021, including all eligible studies investigating the prognostic value of hyperglycemia in patients with aSAH. We performed a quality assessment of included studies using the Newcastle-Ottawa Quality Assessment Scale. The pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were calculated to assess the association of hyperglycemia in aneurysmal subarachnoid hemorrhage. A total of 35 studies with 11,519 patients were finally included in the meta-analysis. Nineteen studies reported the association between hyperglycemia and poor outcome, 12 studies reported the association between hyperglycemia and all-cause mortality, 7 studies reported the association between hyperglycemia and cerebral vasospasm, and 9 studies reported the association between hyperglycemia and cerebral infarction. The pooled data of these studies suggested that hyperglycemia was significantly associated with poor functional outcomes (odds ratio [OR], 1.29; 95% confidence interval [CI], 1.17-1.42; P < 0.00001; I² = 83%), all-cause mortality (OR, 1.02; 95% CI, 1.01-1.04; P = 0.0006; I² = 89%), cerebral vasospasm (OR, 1.02; 95% CI, 1.01-1.02; P = 0.0002; I² = 35%), and cerebral infarction (OR, 1.16; 95% CI, 1.09-1.23; P < 0.00001; I² = 10%) in aSAH patients. These findings suggested that assessing for hyperglycemia at admission may help clinicians to identify critically ill patients and complete patient stratification early, which may achieve better management and improve the prognosis of patients with aSAH.

Multimodal brain monitoring following traumatic brain injury: A primer for intensive care practitioners

Traumatic brain injury (TBI) is common and potentially devastating. Traditional examination-based patient monitoring following TBI may be inadequate for frontline clinicians to reduce secondary brain injury through individualized therapy. Multimodal neurologic monitoring (MMM) offers great potential for detecting early injury and improving outcomes. By assessing cerebral oxygenation, autoregulation and metabolism, clinicians may be able to understand neurophysiology during acute brain injury, and offer therapies better suited to each patient and each stage of injury. Hence, we offer this primer on brain tissue oxygen monitoring, pressure reactivity index monitoring and cerebral microdialysis. This narrative review serves as an introductory guide to the latest clinically-relevant evidence regarding key neuromonitoring techniques.

Association of Age and Sex With Multi-Modal Cerebral Physiology in Adult Moderate/Severe Traumatic Brain Injury: A Narrative Overview and Future Avenues for Personalized Approaches

The impact of age and biological sex on outcome in moderate/severe traumatic brain injury (TBI) has been documented in large cohort studies, with advanced age and male sex linked to worse long-term outcomes. However, the association between age/biological sex and high-frequency continuous multi-modal monitoring (MMM) cerebral physiology is unclear, with only sparing reference made in guidelines and major literature in moderate/severe TBI. In this narrative review, we summarize some of the largest studies associating various high-frequency MMM parameters with age and biological sex in moderate/severe TBI. To start, we present this by highlighting the representative available literature on high-frequency data from Intracranial Pressure (ICP), Cerebral Perfusion Pressure (CPP), Extracellular Brain Tissue Oxygenation (PbtO₂), Regional Cerebral Oxygen Saturations (rSO₂), Cerebral Blood Flow (CBF), Cerebral Blood Flow Velocity (CBFV), Cerebrovascular Reactivity (CVR), Cerebral Compensatory Reserve, common Cerebral Microdialysis (CMD) Analytes and their correlation to age and sex in moderate/severe TBI cohorts. Then we present current knowledge gaps in the literature, discuss biological implications of age and sex on cerebrovascular monitoring in TBI and some future avenues for bedside research into the cerebrovascular physiome after TBI.

Serum glucose and potassium ratio as a predictive factor for prognosis of acute intracerebral hemorrhage

Objective

The serum glucose/potassium ratio (GPR) is a potential prognostic predictor for acute brain injury-related diseases. We calculated the serum GPR in patients with acute intracerebral hemorrhage (ICH) and explored its prognostic value for long-term prognoses and ICH severity.

Methods

This retrospective cohort study consecutively included 92 patients with ICH and 92 healthy controls. The National Institutes of Health Stroke Scale (NIHSS) score, Glasgow coma scale (GCS) score, and hematoma volume were used to assess severity. A modified Rankin Scale score > 2 at 90 days post-stroke was defined as a poor outcome.

Results

The serum GPR was significantly higher in patients than controls. The serum GPR was weakly correlated with the NIHSS score, GCS score, and hematoma volume. The serum GPR, GCS score, and hematoma volume were independently associated with poor outcomes. In the receiver operating characteristic curve analysis, the serum GPR remarkably discriminated patients at risk of poor outcomes at 90 days. The serum GPR significantly improved the prognostic predictive capability of hematoma volume and tended to increase that of the GCS score.

Conclusion

Serum GPR is an easily obtained clinical variable for predicting clinical outcomes after ICH.

Prognostic Nomogram of Predictors for Shunt-Dependent Hydrocephalus in Patients with Aneurysmal Subarachnoid Hemorrhage Receiving External Ventricular Drain Insertion: A Single-Center Experience and Narrative Review

OBJECTIVE

This study aimed to create a prediction model with a radiographic score, serum, and cerebrospinal fluid (CSF) values for the occurrence of shunt-dependent hydrocephalus (SDHC) in patients with aneurysmal subarachnoid hemorrhage (aSAH) and to review and analyze literature related to the prediction of the development of SDHC.

METHODS

Sixty-three patients with aSAH who underwent external ventricular drain insertion were included and separated into 2 subgroups: non-SDHC and SDHC. Patient characteristics, computed tomography scoring system, and serum and CSF parameters were collected. Multivariate logistic regression was conducted to illustrate a nomogram for determining the predictors of SDHC. Furthermore, we sorted and summarized previous meta-analyses for predictors of SDHC.

RESULTS

The SDHC group had 42 cases. Stepwise logistic regression analysis revealed 3 independent predictive factors associated with a higher modified Graeb (mGraeb) score, lower level of estimated glomerular filtration rate group, and lower level of CSF glucose. The nomogram, based on these 3 factors, was presented with significant predictive performance (area under curve = 0.895) for SDHC development, compared with other scoring systems (AUC = 0.764-0.885). In addition, a forest plot was generated to present the 12 statistically significant predictors and odds ratio for correlations with the development of SDHC.

CONCLUSIONS

First, the development of a nomogram with combined significant factors had a good performance in estimating the risk of SDHC in primary patient evaluation and assisted in clinical decision making. Second, a narrative review, presented with a forest plot, provided the current published data on predicting SDHC.

Neuroprotective effects of metformin on traumatic brain injury in rats is associated with the AMP-activated protein kinase signaling pathway

Metformin is an activator of AMP-activated protein kinase (AMPK). Thus, it has the potential to restore energy in damaged neurons and attenuate secondary brain damage due to traumatic brain injury (TBI). This study aims to investigate the potential neuroprotective effects of metformin through the energy balance reestablishment in acute severe brain injury after TBI and explore the underlying mechanisms. Male Wistar rats were divided into eight groups. The veterinary coma scale (VCS) was used to assess short-term neurological deficits. Blood-Brain barrier (BBB) disruption was evaluated by Evans Blue method 6 h post-injury. Vestibulomotor function was evaluated by beam-walk and beam-balance methods. Brain water content and brain tissue phosphorylated and total AMPK were assessed by the wet/dry method and enzyme-linked immunosorbent assay (ELISA), respectively. In order to eliminate the effect of AMPK, compound C was used as an AMPK inhibitor. The presented study showed that TBI has led to significant brain edema, BBB disruption, neurological deficit, vestibulomotor dysfunction and decrease AMPK phosphorylation in the rat brain. Metformin (100 and 200 mg/kg doses) attenuated brain edema, improved BBB and vestibulomotor dysfunction compared to TBI or Vehicle groups (P < 0.001). Furthermore, the p-AMPK/AMPK ratio was increased by metformin administration compare to TBI or Vehicle groups (p < 0.0001). Inhibition of AMPK by compound C abolished Metformin neuroprotective effects (P < 0.05 compared to Met 200 group). This study suggests that metformin inhibits TBI-mediated secondary injury via phosphorylation of AMPK and improves neurobehavioral function following TBI, which provides a potential therapeutic opportunity in the treatment of TBI.

Assessment of serum glucose/potassium ratio as a predictor for delayed neuropsychiatric syndrome of carbon monoxide poisoning

INTRODUCTION

Carbon monoxide (CO) poisoning is a crucial cause of delayed neuropsychiatric syndrome (DNS). However, most biomarkers are not satisfactory for the prediction of DNS caused by CO poisoning. Thus, we evaluated the adequacy of the serum glucose/potassium (GLU/K) ratio, which may be an easy, quick, and readily available parameter that can be used in the emergency department for predicting DNS.

METHODS

We evaluated 281 patients who were admitted to our emergency department between January 2012 and December 2018. The patients were divided into two groups: DNS (+) and DNS (-). The GLU/K was compared for the groups.

RESULTS

Glucose, blood urea nitrogen, carboxyhemoglobin, and GLU/K ratios of patients in the DNS (+) group were statistically significantly higher than those patients in DNS (-) group (140 ± 34 vs. 110 ± 24, p < 0.001; 17.58 ± 6.14 vs. 14.27 ± 5.08, p = 0.003; 29 ± 5.1 vs. 18.9 ± 7.6, p < 0.001; and 38.35 ± 10.11 vs. 28.65 ± 6.53, p < 0.001, respectively). The area under the curve for GLU/K to predict DNS was measured as 0.791, and 35.9 as a cut-off value had 63.6% sensitivity and 89.6% specificity.

CONCLUSIONS

DNS development in CO poisoning is a serious and feared complication. We suggest that the GLU/K ratio has a high potential as a rapid, easy preliminary marker for the exclusion of patients who will not subsequently develop DNS.

Usefulness of serum glucose and potassium ratio as a predictor for 30-day death among patients with severe traumatic brain injury

BACKGROUND

Serum glucose and potassium ratio (GPR) was recently found to be related to outcome of aneurysmal subarachnoid hemorrhage. This retrospectively study was to investigate the association of serum GPR with mortality in severe traumatic brain injury (sTBI).

METHODS

Clinical data were retrospectively reviewed of isolated sTBI patients admitted within 12 h after trauma between January 2014 and January 2019. We analyzed relationships between admission serum GPR and post-traumatic 30-day mortality in addition to admission Glasgow coma scale (GCS) scores. Discriminative ability was evaluated using area under receiver operating characteristic curve (AUC).

RESULTS

A total of 146 patients, of whom 37 (25.3%) died within 30 days following trauma, were included. Admission serum GPR emerged as an independent predictor for 30-day mortality (odds ratio, 5.256; 95% confidence interval (CI), 1.111-14.856) and overall survival (hazard ratio, 4.822; 95% CI, 1.157-12.870), with an AUC of 0.777 (95% CI, 0.693-0.835), which was equivalent to that of GCS scores (AUC, 0.831; 95% CI, 0.760-0.888; P = 0.179). There was a significant correlation between admission serum GPR and GCS scores (r² = 0.293).

CONCLUSIONS

Serum GPR in cases of sTBI is substantially associated with trauma severity and 30-day mortality. Therefore, the potential value of serum GPR for predicting short-term mortality of sTBI patients is favorable.

Nutrition Therapy, Glucose Control, and Brain Metabolism in Traumatic Brain Injury: A Multimodal Monitoring Approach

The goal of neurocritical care in patients with traumatic brain injury (TBI) is to prevent secondary brain damage. Pathophysiological mechanisms lead to loss of body mass, negative nitrogen balance, dysglycemia, and cerebral metabolic dysfunction. All of these complications have been shown to impact outcomes. Therapeutic options are available that prevent or mitigate their negative impact. Nutrition therapy, glucose control, and multimodality monitoring with cerebral microdialysis (CMD) can be applied as an integrated approach to optimize systemic immune and organ function as well as adequate substrate delivery to the brain. CMD allows real-time bedside monitoring of aspects of brain energy metabolism, by measuring specific metabolites in the extracellular fluid of brain tissue. Sequential monitoring of brain glucose and lactate/pyruvate ratio may reveal pathologic processes that lead to imbalances in supply and demand. Early recognition of these patterns may help individualize cerebral perfusion targets and systemic glucose control following TBI. In this direction, recent consensus statements have provided guidelines and recommendations for CMD applications in neurocritical care. In this review, we summarize data from clinical research on patients with severe TBI focused on a multimodal approach to evaluate aspects of nutrition therapy, such as timing and route; aspects of systemic glucose management, such as intensive vs. moderate control; and finally, aspects of cerebral metabolism. Research and clinical applications of CMD to better understand the interplay between substrate supply, glycemic variations, insulin therapy, and their effects on the brain metabolic profile were also reviewed. Novel mechanistic hypotheses in the interpretation of brain biomarkers were also discussed. Finally, we offer an integrated approach that includes nutritional and brain metabolic monitoring to manage severe TBI patients.

Glucose Variability as Measured by Inter-measurement Percentage Change is Predictive of In-patient Mortality in Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Critically ill aneurysmal subarachnoid hemorrhage (aSAH) patients suffer from systemic complications at a high rate. Hyperglycemia is a common intensive care unit (ICU) complication and has become a focus after aggressive glucose management was associated with improved ICU outcomes. Subsequent research has suggested that glucose variability, not a specific blood glucose range, may be a more appropriate clinical target. Glucose variability is highly correlated to poor outcomes in a wide spectrum of critically ill patients. Here, we investigate the changes between subsequent glucose values termed "inter-measurement difference," as an indicator of glucose variability and its association with outcomes in patients with aSAH.

METHODS

All SAH admissions to a single, tertiary referral center between 2002 and 2016 were screened. All aneurysmal cases who had more than 2 glucose measurements were included (n = 2451). We calculated several measures of variability, including simple variance, the average consecutive absolute change, average absolute change by time difference, within subject variance, median absolute deviation, and average or median consecutive absolute percentage change. Predictor variables also included admission Hunt and Hess grade, age, gender, cardiovascular risk factors, and surgical treatment. In-patient mortality was the main outcome measure.

RESULTS

In a multiple regression analysis, nearly all forms of glucose variability calculations were found to be correlated with in-patient mortality. The consecutive absolute percentage change, however, was most predictive: OR 5.2 [1.4-19.8, CI 95%] for percentage change and 8.8 [1.8-43.6] for median change, when controlling for the defined predictors. Survival to ICU discharge was associated with lower glucose variability (consecutive absolute percentage change 17% ± 9%) compared with the group that did not survive to discharge (20% ± 15%, p < 0.01). Interestingly, this finding was not significant in patients with pre-admission poorly controlled diabetes as indicated by HbA1c (OR 0.45 [0.04-7.18], by percentage change). The effect is driven mostly by non-diabetic patients or those with well-controlled diabetes.

CONCLUSIONS

Reduced glucose variability is highly correlated with in-patient survival and long-term mortality in aSAH patients. This finding was observed in the non-diabetic and well-controlled diabetic patients, suggesting a possible benefit for personalized glucose targets based on baseline HbA1c and minimizing variability. The inter-measure percentage change as an indicator of glucose variability is not only predictive of outcome, but is an easy-to-use tool that could be implemented in future clinical trials.

Serum Glucose and Potassium Ratio as Risk Factors for Cerebral Vasospasm after Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE

Cerebral vasospasm is associated with poor prognosis in patients with aneurysmal subarachnoid hemorrhage (SAH), and biomarkers for predicting poor prognosis have not yet been established. We attempted to clarify the relationship between serum glucose/potassium ratio and cerebral vasospasm in patients with aneurysmal SAH.

METHODS

We studied 333 of 535 aneurysmal SAH patients treated between 2006 and 2016 (123 males, 210 females; mean age 59.7 years; range 24-93). We retrospectively analyzed the relationship between cerebral vasospasm grade and clinical risk factors, including serum glucose/potassium ratio.

RESULTS

Postoperative angiography revealed cerebral vasospasm in 112 patients (33.6%). Significant correlations existed between the ischemic complication due to cerebral vasospasm and glucose/potassium ratio (P < .0001), glucose (P = .016), and potassium (P = .0017). Serum glucose/potassium ratio was elevated in the cerebral vasospasm grade dependent manner (Spearman's r = 0.1207, P = .0279). According to the Glasgow Outcome Scale (GOS) score at discharge, 185 patients (55.5%) had a poor outcome (GOS scores 1-3). Serum glucose/potassium ratio was significantly correlated between poor outcome (GOS scores 1-3) and age (P < .0001), serum glucose/potassium ratio (P < .0001), glucose (P < .0001), potassium (P = .0004), white blood cell count (P = .0012), and cerebral infarction due to cerebral vasospasm (P < .0001). Multivariate logistic regression analyzes showed significant correlations between cerebral infarction due to cerebral vasospasm and serum glucose/potassium ratio (P = .018), glucose (P = .027), and potassium (P = .052).

CONCLUSIONS

Serum glucose/potassium ratio in cases of aneurysmal SAH was significantly associated with cerebral infarction due to cerebral vasospasm and GOS at discharge. Therefore, this factor was useful to predict prognosis in patients with cerebral vasospasm and aneurysmal SAH.

Nutritional and Bioenergetic Considerations in Critically Ill Patients with Acute Neurological Injury

The brain, due to intensive cellular processes and maintenance of electrochemical gradients, is heavily dependent on a constant supply of energy. Brain injury, and critical illness in general, induces a state of increased metabolism and catabolism, which has been proven to lead to poor outcomes. Of all the biochemical interventions undertaken in the ICU, providing nutritional support is perhaps one of the most undervalued, but potentially among the safest, and most effective interventions. Adequate provisions of calories and protein have been shown to improve patient outcomes, and guidelines for the nutritional support of the critically ill patient are reviewed. However, there are no such specific guidelines for the critically ill patient with neurological injury. Patients with primary or secondary neurological disorders are frequently undernourished, while data suggest this population would benefit from early and adequate nutritional support, although comprehensive clinical evidence is lacking. We review the joint recommendations from the Society for Critical Care Medicine and the American Society for Parenteral and Enteral Nutrition, as they pertain to neurocritical care, and assess the recommendations for addressing nutrition in this patient population.

A systematic review of cerebral microdialysis and outcomes in TBI: relationships to patient functional outcome, neurophysiologic measures, and tissue outcome

OBJECTIVE

To perform a systematic review on commonly measured cerebral microdialysis (CMD) analytes and their association to: (A) patient functional outcome, (B) neurophysiologic measures, and (C) tissue outcome; after moderate/severe TBI. The aim was to provide a foundation for next-generation CMD studies and build on existing pragmatic expert guidelines for CMD.

METHODS

We searched MEDLINE, BIOSIS, EMBASE, Global Health, Scopus, Cochrane Library (inception to October 2016). Strength of evidence was adjudicated using GRADE.

RESULTS

(A) Functional Outcome: 55 articles were included, assessing outcome as mortality or Glasgow Outcome Scale (GOS) at 3-6 months post-injury. Overall, there is GRADE C evidence to support an association between CMD glucose, glutamate, glycerol, lactate, and LPR to patient outcome at 3-6 months. (B) Neurophysiologic Measures: 59 articles were included. Overall, there currently exists GRADE C level of evidence supporting an association between elevated CMD measured mean LPR, glutamate and glycerol with elevated ICP and/or decreased CPP. In addition, there currently exists GRADE C evidence to support an association between elevated mean lactate:pyruvate ratio (LPR) and low PbtO2. Remaining CMD measures and physiologic outcomes displayed GRADE D or no evidence to support a relationship. (C) Tissue Outcome: four studies were included. Given the conflicting literature, the only conclusion that can be drawn is acute/subacute phase elevation of CMD measured LPR is associated with frontal lobe atrophy at 6 months.

CONCLUSIONS

This systematic review replicates previously documented relationships between CMD and various outcome, which have driven clinical application of the technique. Evidence assessments do not address the application of CMD for exploring pathophysiology or titrating therapy in individual patients, and do not account for the modulatory effect of therapy on outcome, triggered at different CMD thresholds in individual centers. Our findings support clinical application of CMD and refinement of existing guidelines.

Serum glucose/potassium ratio as a clinical risk factor for aneurysmal subarachnoid hemorrhage

OBJECTIVE

Aneurysmal subarachnoid hemorrhage (SAH) can result in poor outcomes, and biomarkers for predicting poor prognosis have not yet been established. The aim of this study was to clarify the significance of the serum glucose/potassium ratio for predicting the prognosis of aneurysmal SAH.

METHODS

The authors retrospectively reviewed the records of 565 patients with aneurysmal SAH between 2006 and 2016. The patient group comprised 208 men and 357 women (mean age 61.5 years, range 10-95 years). A statistical analysis was conducted of the clinical and laboratory risk factors of poor outcome, including the serum glucose/potassium ratio.

RESULTS

On estimation of the initial assessment using Hunt and Kosnik (H-K) grading, 233 patients (41.2%) were classified as the severe SAH group (H-K Grade IV or V). There were significant correlations between the severe SAH group and serum glucose/potassium ratio (p < 0.0001). Serum glucose/potassium ratio was elevated in an H-K grade-dependent manner (Spearman's r = 0.5374, p < 0.0001). With the estimation of the Glasgow Outcome Scale (GOS) score at discharge, 355 patients (62.8%) were classified as poor outcome (GOS score 1-3). The serum glucose/potassium ratio was elevated in a GOS score at discharge-dependent manner (Spearman's r = 0.4006, p < 0.0001), and was significantly elevated in the poor outcome group compared with the good outcome group (GOS score 4 or 5; p = 0.0245). There were significant correlations between poor outcome and serum glucose/potassium ratio (p < 0.0001), age (p < 0.0001), brain natriuretic peptide levels (p = 0.011), cerebral infarction due to vasospasm (p < 0.0001), and H-K grade (p < 0.0001). Multivariate logistic regression analyses showed significant correlations between poor outcome and serum glucose/potassium ratio (p = 0.009).

CONCLUSIONS

In this study, the serum glucose/potassium ratio of patients with aneurysmal SAH at admission was significantly correlated with H-K grade and GOS score at discharge. Therefore, this ratio was useful for predicting prognosis of aneurysmal SAH, especially in severe cases.

Cerebral Microdialysis Monitoring to Improve Individualized Neurointensive Care Therapy: An Update of Recent Clinical Data

Cerebral microdialysis (CMD) allows bedside semicontinuous monitoring of patient brain extracellular fluid. Clinical indications of CMD monitoring are focused on the management of secondary cerebral and systemic insults in acute brain injury (ABI) patients [mainly, traumatic brain injury (TBI), subarachnoid hemorrhage, and intracerebral hemorrhage (ICH)], specifically to tailor several routine interventions—such as optimization of cerebral perfusion pressure, blood transfusion, glycemic control and oxygen therapy—in the individual patient. Using CMD as clinical research tool has greatly contributed to identify and better understand important post-injury mechanisms—such as energy dysfunction, posttraumatic glycolysis, post-aneurysmal early brain injury, cortical spreading depressions, and subclinical seizures. Main CMD metabolites (namely, lactate/pyruvate ratio, and glucose) can be used to monitor the brain response to specific interventions, to assess the extent of injury, and to inform about prognosis. Recent consensus statements have provided guidelines and recommendations for CMD monitoring in neurocritical care. Here, we summarize recent clinical investigation conducted in ABI patients, specifically focusing on the role of CMD to guide individualized intensive care therapy and to improve our understanding of the complex disease mechanisms occurring in the immediate phase following ABI. Promising brain biomarkers will also be described.

Cerebral Metabolism and the Role of Glucose Control in Acute Traumatic Brain Injury

This article reviews key concepts of cerebral glucose metabolism, neurologic outcomes in clinical trials, the biology of the neurovascular unit and its involvement in secondary brain injury after traumatic brain insults, and current scientific and clinical data that demonstrate a better understanding of the biology of metabolic dysfunction in the brain, a concept now known as cerebral metabolic energy crisis. The use of neuromonitoring techniques to better understand the pathophysiology of the metabolic crisis is reviewed and a model that summarizes the triphasic view of cerebral metabolic disturbance supported by existing scientific data is outlined. The evidence is summarized and a template for future research provided.

Pathophysiology and the Monitoring Methods for Cardiac Arrest Associated Brain Injury

Cardiac arrest (CA) is a well-known cause of global brain ischemia. After CA and subsequent loss of consciousness, oxygen tension starts to decline and leads to a series of cellular changes that will lead to cellular death, if not reversed immediately, with brain edema as a result. The electroencephalographic activity starts to change as well. Although increased intracranial pressure (ICP) is not a direct result of cardiac arrest, it can still occur due to hypoxic-ischemic encephalopathy induced changes in brain tissue, and is a measure of brain edema after CA and ischemic brain injury. In this review, we will discuss the pathophysiology of brain edema after CA, some available techniques, and methods to monitor brain oxygen, electroencephalography (EEG), ICP (intracranial pressure), and microdialysis on its measurement of cerebral metabolism and its usefulness both in clinical practice and possible basic science research in development. With this review, we hope to gain knowledge of the more personalized information about patient status and specifics of their brain injury, and thus facilitating the physicians’ decision making in terms of which treatments to pursue.

Brain Monitoring in Critically Neurologically Impaired Patients

Assessment of neurologic injury and the evolution of severe neurologic injury is limited in comatose or critically ill patients that lack a reliable neurologic examination. For common yet severe pathologies such as the comatose state after cardiac arrest, aneurysmal subarachnoid hemorrhage (aSAH), and severe traumatic brain injury (TBI), critical medical decisions are made on the basis of the neurologic injury. Decisions regarding active intensive care management, need for neurosurgical intervention, and withdrawal of care, depend on a reliable, high-quality assessment of the true state of neurologic injury, and have traditionally relied on limited assessments such as intracranial pressure monitoring and electroencephalogram. However, even within TBI there exists a spectrum of disease that is likely not captured by such limited monitoring and thus a more directed effort towards obtaining a more robust biophysical signature of the individual patient must be undertaken. In this review, multimodal monitoring including the most promising serum markers of neuronal injury, cerebral microdialysis, brain tissue oxygenation, and pressure reactivity index to access brain microenvironment will be discussed with their utility among specific pathologies that may help determine a more complete picture of the neurologic injury state for active intensive care management and long-term outcomes. Goal-directed therapy guided by a multi-modality approach appears to be superior to standard intracranial pressure (ICP) guided therapy and should be explored further across multiple pathologies. Future directions including the application of optogenetics to evaluate brain injury and recovery and even as an adjunct monitoring modality will also be discussed.

Intracranial Pressure Increases During Rewarming Period After Mild Therapeutic Hypothermia in Postcardiac Arrest Patients

Elevation of intracranial pressure (ICP) may worsen brain injury and neurological outcome. Studies on the use of therapeutic hypothermia (TH) for traumatic brain injury suggests that rapid rewarming from TH is associated with elevated ICP and poorer outcomes. However, few studies describe the time course of ICP changes during TH/rewarming after cardiac arrest (CA). In this study, we observed the changes in ICP during mild TH and rewarming after CA. Secondarily, we examined whether ICP is related to outcome. We studied comatose patients resuscitated from CA, who were treated with TH and who had ICP monitored. Target core temperature was 34°C for 24 h and target rewarming rate was 0.25°C/h. ICP and cerebral perfusion pressure (CPP) were monitored during the period. Outcome was rated as cerebral performance category. In nine patients, ICP increased during TH and rewarming (6.0 [4.0-9.0] mmHg to 16.0 [12.0-26.0] mmHg, p = 0.008). CPP did not change during the period (83.3 [80.1-91.0] mmHg to 74.3 [52.0-87.3] mmHg). Higher ICP was associated with worse outcomes (p = 0.009). All the cases with ICP >25 mmHg or CPP <40 mmHg died. Major ICP increment was observed during the rewarming period, although, some increase of ICP occurred even during the mild TH. ICP increment was higher in patients with worse outcomes.

Cerebral Glucose Metabolism and Sedation in Brain-injured Patients: A Microdialysis Study

BACKGROUND

Disturbed brain metabolism is a signature of primary damage and/or precipitates secondary injury processes after severe brain injury. Sedatives and analgesics target electrophysiological functioning and are as such well-known modulators of brain energy metabolism. Still unclear, however, is how sedatives impact glucose metabolism and whether they differentially influence brain metabolism in normally active, healthy brain and critically impaired, injured brain. We therefore examined and compared the effects of anesthetic drugs under both critical (<1 mmol/L) and noncritical (>1 mmol/L) extracellular brain glucose levels.

METHODS

We performed an explorative, retrospective analysis of anesthetic drug administration and brain glucose concentrations, obtained by bedside microdialysis, in 19 brain-injured patients.

RESULT

Our investigations revealed an inverse linear correlation between brain glucose and both the concentration of extracellular glutamate (Pearson r=-0.58, P=0.01) and the lactate/glucose ratio (Pearson r=-0.55, P=0.01). For noncritical brain glucose levels, we observed a positive linear correlation between midazolam dose and brain glucose (P<0.05). For critical brain glucose levels, extracellular brain glucose was unaffected by any type of sedative.

CONCLUSIONS

These findings suggest that the use of anesthetic drugs may be of limited value in attempts to influence brain glucose metabolism in injured brain tissue.

Increased platelet mitochondrial respiration after cardiac arrest and resuscitation as a potential peripheral biosignature of cerebral bioenergetic dysfunction

Cardiac arrest (CA) results in a sepsis-like syndrome with activation of the innate immune system and increased mitochondrial bioenergetics.

OBJECTIVE

To determine if platelet mitochondrial respiration increases following CA in a porcine pediatric model of asphyxia-associated ventricular fibrillation (VF) CA, and if this readily obtained biomarker is associated with decreased brain mitochondrial respiration. CA protocol: 7 min of asphyxia, followed by VF, protocolized titration of compression depth to systolic blood pressure of 90 mmHg and vasopressor administration to a coronary perfusion pressure greater than 20 mmHg.

PRIMARY OUTCOME

platelet integrated mitochondrial electron transport system (ETS) function evaluated pre- and post-CA/ROSC four hours after return of spontaneous circulation (ROSC). Secondary outcome: correlation of platelet mitochondrial bioenergetics to cerebral bioenergetic function. Platelet maximal oxidative phosphorylation (OXPHOSCI+CII), P < 0.02, and maximal respiratory capacity (ETSCI+CII), P < 0.04, were both significantly increased compared to pre-arrest values. This was primarily due to a significant increase in succinate-supported respiration through Complex II (OXPHOSCII, P < 0.02 and ETSCII, P < 0.03). Higher respiration was not due to uncoupling, as the LEAKCI + CII respiration (mitochondrial respiration independent of ATP-production) was unchanged after CA/ROSC. Larger increases in platelet mitochondrial respiratory control ratio (RCR) compared to pre-CA RCR were significantly correlated with lower RCRs in the cortex (P < 0.03) and hippocampus (P < 0.04) compared to sham respiration. Platelet mitochondrial respiration is significantly increased four hours after ROSC. Future studies will identify mechanistic relationships between this serum biomarker and altered cerebral bioenergetics function following cardiac arrest.

What's new in the management of traumatic brain injury on neuro ICU?

PURPOSE OF REVIEW

In recent years, we have begun to better understand how to monitor the injured brain, look for less common complications and importantly, reduce unnecessary and potentially harmful intervention. However, the lack of consensus regarding triggers for intervention, best neuromonitoring techniques and standardization of therapeutic approach is in need of more careful study. This review covers the most recent evidence within this exciting and dynamic field.

RECENT FINDINGS

The role of intracranial pressure monitoring has been challenged; however, it still remains a cornerstone in the management of the severely brain-injured patient and should be used to compliment other techniques, such as clinical examination and serial imaging.The use of multimodal monitoring continues to be refined and it may be possible to use them to guide novel brain resuscitation techniques, such as the use of exogenous lactate supplementation in the future.

SUMMARY

Neurocritical care management of traumatic brain injury continues to evolve. However, it is important not to use a 'one-treatment-fits-all' approach, and perhaps look to use targeted therapies to individualize treatment.