Intensive insulin therapy reduces microdialysis glucose values without altering glucose utilization or improving the lactate/pyruvate ratio after traumatic brain injury*

Frequency and impact of intensive care unit complications on moderate-severe traumatic brain injury: early results of the Outcome Prognostication in Traumatic Brain Injury (OPTIMISM) Study

BACKGROUND

Known predictors of adverse outcomes in patients with moderate-severe TBI (msTBI) explain only a relatively small proportion of patient-related outcomes. The frequency and impact of intensive care unit complications (ICU-COMPL) on msTBI-associated outcomes are poorly understood.

METHODS

In 213 consecutive msTBI patients admitted to a Level I Trauma Center neuro trauma ICU, twenty-eight ICU-COMPL (21 medical and 7 neurological) were prospectively collected and adjudicated by group consensus, using pre-defined criteria. We determined frequencies, and explored associations of ICU-COMPL and hospital discharge outcomes using multivariable logistic regression.

RESULTS

The average age of the study sample was 53 years, and the median presenting Glasgow Coma Scale and Injury Severity Scores were 5 and 27, respectively. Hyperglycemia (79%), fever (62%), systemic inflammatory response syndrome (60%), and hypotension requiring vasopressors (42%) were the four most common medical ICU-COMPL. Herniation (39%), intracranial rebleed (39%), and brain edema requiring osmotherapy (37%) were the three most common neurological ICU-COMPL. After adjusting for admission variables, duration of ventilation, and ICU length-of-stay, patients with brain edema (OR 5.8; 95% CI 2, 16.7) had a significantly increased odds for dying during hospitalization whereas patients with hospital-acquired urinary tract infection (UTI) had a decreased odds (OR 0.05; 95% CI 0.005, 0.6). Sensitivity analysis revealed that UTI occurred later, suggesting a non-causal association with survival. Brain herniation (OR 15.7; 95% CI 2.6, 95.4) was associated with an unfavorable functional status (GOS 1-3).

CONCLUSION

ICU-COMPL are very common after msTBI, have a considerable impact on short-term outcomes, and should be considered in the prognostication of these high risk patients. Survival associations of time-dependent complications warrant cautious interpretation.

Prognosis in severe brain injury

BACKGROUND

The prediction of neurologic outcome is a fundamental concern in the resuscitation of patients with severe brain injury.

OBJECTIVE

To provide an evidence-based update on neurologic prognosis following traumatic brain injury and hypoxic-ischemic encephalopathy after cardiac arrest.

DATA SOURCE

Search of the PubMed database and manual review of bibliographies from selected articles to identify original data relating to prognostic methods and outcome prediction models in patients with neurologic trauma or hypoxic-ischemic encephalopathy.

DATA SYNTHESIS AND CONCLUSION

Articles were scrutinized regarding study design, population evaluated, interventions, outcomes, and limitations. Outcome prediction in severe brain injury is reliant on features of the neurologic examination, anatomical and physiological changes identified with CT and MRI, abnormalities detected with electroencephalography and evoked potentials, and physiological and biochemical derangements at both the brain and systemic levels. Use of such information in univariable association studies generally lacks specificity in classifying neurologic outcome. Furthermore, the accuracy of established prognostic classifiers may be affected by the introduction of outcome-modifying interventions, such as therapeutic hypothermia following cardiac arrest. Although greater specificity may be achieved with scoring systems derived from multivariable models, they generally fail to predict outcome with sufficient accuracy to be meaningful at the single patient level. Discriminative models which integrate knowledge of genetic determinants and biologic processes governing both injury and repair and account for the effects of resuscitative and rehabilitative care are needed.

Trauma and aggressive homeostasis management

Homeostasis refers to the capacity of the human body to maintain a stable constant state by means of continuous dynamic equilibrium adjustments controlled by a medley of interconnected regulatory mechanisms. Patients who sustain tissue injury, such as trauma or surgery, undergo a well-understood reproducible metabolic and neuroendocrine stress response. This review discusses 3 issues that concern homeostasis in the acute care of trauma patients directly related to the stress response: hyperglycemia, lactic acidosis, and hypothermia. There is significant reason to question the "conventional wisdom" relating to current approaches to restoring homeostasis in critically ill and trauma patients.

Tight glycemic control reduces infection and improves neurological outcome in critically ill neurosurgical and neurological patients

BACKGROUND

Tight glycemic control (TGC) may improve outcomes in hyperglycemic neurosurgical patients. The adoption of TGC has been limited by a lack of adequate data on optimal insulin delivery protocols and serum glucose concentration and by concerns about the risks of hypoglycemia.

OBJECTIVE

This study was designed as a meta-analysis of outcomes to compare intensive insulin therapy and TGC with conventional insulin therapy and conventional glucose control. The secondary objective was to determine retrospectively whether a particular glucose range correlates with better outcomes.

METHODS

Using electronic databases, we retrieved all English language studies published between January 1997 and December 2010 reporting outcomes in neurological and neurosurgical patients as a function of glucose levels and insulin protocols. We conducted a meta-analysis around 4 outcome measures: infection, neurological outcome, hypoglycemia, and mortality. Effect sizes in each study were individually correlated with target intensive insulin therapy glucose levels. Individual studies were assessed for quality by use of the Jadad scale.

RESULTS

Nine studies reporting on 1459 patients met the inclusion criteria. Five were restricted to neurosurgical patients. Four included neurological patients. Compared with conventional glucose control, TGC lowered infection rates (odds ratio, 0.59; 95% confidence interval, 0.47-0.76; P < .001) and yielded better neurological outcomes (odds ratio, 1.72; 95% confidence interval, 1.36-2.16; P < .001). Beneficial effects increased as glucose limits tightened and study quality improved (R > 0.9 for both). TGC resulted in a higher rate of hypoglycemic events (odds ratio, 8.04; 95% confidence interval, 4.85-13.31; P < .001). Mortality was not affected.

CONCLUSION

TGC reduced infection risk and improved neurological outcome despite increased rates of hypoglycemic events. An optimal target for serum glucose concentrations could not be determined.

Cerebral glucose and spreading depolarization in patients with aneurysmal subarachnoid hemorrhage

The pathogenesis of delayed cerebral ischemia (DCI) is multifactorial and not completely elucidated. Our objective was to determine if episodes of spreading depolarization (SD) are reflected in compromised levels of extracellular glucose monitored by bedside microdialysis (MD) in aneurysmal subarachnoid hemorrhage (aSAH) patients. Patients with aSAH, prospectively included in the COSBID (CoOperative Study on Brain Injury Depolarisations) protocol (Berlin, Heidelberg), had hourly monitoring of cerebral glucose by MD and in parallel electrocorticographic (ECoG) monitoring for SD detection on day of admission until days 10-14 after aSAH. Cerebral MD probes were placed in the vascular territory at risk for DCI. Twenty-one aSAH patients (53.3 ± 9.1 years; mean ± standard deviation), classified according to the World Federation of Neurosurgical Societies (WFNS) in low (I-III, 11) and high (IV-V, 10) grades, were studied. Of these, 13 patients (62%) presented with DCI. Median glucose was 1.48 (0.00-8.79). Median occurrence of SD was 7 (0-66)/patients. High WFNS grade (WFNS grades IV-V) patients had more SDs (p = 0.027), while the overall glucose level did not differ. In high-grade SAH patients, SDs were more frequent. Individually, the occurrence of SD was not linked to local deviations (neither high nor low) from the LOWESS (locally weighted scatterplot smoothing) trend curve for extracellular glucose concentrations. Rapid-sampling MD techniques and analyses of SD clusters may elucidate more detail of the relationship between SD and brain energy metabolism.

Optimal glycemic control in neurocritical care patients: a systematic review and meta-analysis

INTRODUCTION

Hyper- and hypoglycemia are strongly associated with adverse outcomes in critical care. Neurologically injured patients are a unique subgroup, where optimal glycemic targets may differ, such that the findings of clinical trials involving heterogeneous critically ill patients may not apply.

METHODS

We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) comparing intensive insulin therapy with conventional glycemic control among patients with traumatic brain injury, ischemic or hemorrhagic stroke, anoxic encephalopathy, central nervous system infections or spinal cord injury.

RESULTS

Sixteen RCTs, involving 1248 neurocritical care patients, were included. Glycemic targets with intensive insulin ranged from 70-140 mg/dl (3.9-7.8 mmol/L), while conventional protocols aimed to keep glucose levels below 144-300 mg/dl (8.0-16.7 mmol/L). Tight glycemic control had no impact on mortality (RR 0.99; 95% CI 0.83-1.17; p = 0.88), but did result in fewer unfavorable neurological outcomes (RR 0.91; 95% CI 0.84-1.00; p = 0.04). However, improved outcomes were only observed when glucose levels in the conventional glycemic control group were permitted to be relatively high [threshold for insulin administration > 200 mg/dl (> 11.1 mmol/L)], but not with more intermediate glycemic targets [threshold for insulin administration 140-180 mg/dl (7.8-10.0 mmol/L)]. Hypoglycemia was far more common with intensive therapy (RR 3.10; 95% CI 1.54-6.23; p = 0.002), but there was a large degree of heterogeneity in the results of individual trials (Q = 47.9; p<0.0001; I2 = 75%). Mortality was non-significantly higher with intensive insulin in studies where the proportion of patients developing hypoglycemia was large (> 33%) (RR 1.17; 95% CI 0.79-1.75; p = 0.44).

CONCLUSIONS

Intensive insulin therapy significantly increases the risk of hypoglycemia and does not influence mortality among neurocritical care patients. Very loose glucose control is associated with worse neurological recovery and should be avoided. These results suggest that intermediate glycemic goals may be most appropriate.

Risk factors for hypoglycaemia in neurocritical care patients

PURPOSE

To identify risk factors for hypoglycaemia in neurocritical care patients receiving intensive insulin therapy (IIT).

METHODS

We performed a nested case-control study. All first episodes of hypoglycaemia (glucose <80 mg/dL, <4.4 mmol/L) in neurocritical care patients between 1 March 2006 and 31 December 2007 were identified. Patients were treated according to the local IIT protocol, with target blood glucose levels between 4.5 and 6.0 mmol/L (81.0-108.0 mg/dL). The first hypoglycaemic event of every patient (index moment) was used to match to a control patient. Possible risk factors preceding the index moment were scored using hospital records and analysed with conditional logistic regression.

RESULTS

Of 786 neurocritical care patients, 449 developed hypoglycaemia (57.1 %). Independent risk factors for hypoglycaemia were lowering nutrition 6 h before the index moment without insulin dose reduction (odds ratio (OR) 5.25, 95 % confidence interval (95 % CI) 1.32-20.88), mechanical ventilation (OR 2.59, 95 % CI 1.56-4.29), lowering the dosage of norepinephrine 3 h before the index moment (OR 2.44, 95 % CI 1.07-5.55), a hyperglycaemic event (>10 mmol/L, >180.0 mg/dL) in the 24 h preceding the index moment (OR 2.40, 95 % CI 1.26-4.58), gastric residual in the 6 h preceding the index moment without insulin dose reduction (OR 1.76, 95 % CI 1.05-2.96) and dosage of insulin at the index moment (OR 0.83, 95 % CI 0.76-0.90).

CONCLUSION

Hypoglycaemia occurs in a considerable proportion of neurocritical care patients. We recommend the identification of these risk factors in these patients to avoid the occurrence of hypoglycaemia.

Tight glycemic control increases metabolic distress in traumatic brain injury: a randomized controlled within-subjects trial

OBJECTIVE

To determine the effects of tight glycemic control on brain metabolism after traumatic brain injury using brain positron emission tomography and microdialysis.

DESIGN

Single-center, randomized controlled within-subject crossover observational trial.

SETTING

Academic intensive care unit.

METHODS

We performed a prospective, unblinded randomized controlled within-subject crossover trial of tight (80-110 mg/dL) vs. loose (120-150 mg/dL) glycemic control in patients with severe traumatic brain injury to determine the effects of glycemic control on brain glucose metabolism, as measured by [18F] deoxy-D-glucose brain positron emission tomography. Brain microdialysis was done simultaneously.

MEASUREMENTS AND MAIN RESULTS

Thirteen severely injured traumatic brain injury patients underwent the study between 3 and 8 days (mean 4.8 days) after traumatic brain injury. In ten of these subjects, global brain and gray matter tissues demonstrated higher glucose metabolic rates while glucose was under tight control as compared with loose control (3.2 ± 0.6 vs. 2.4 + 0.4, p = .02 [whole brain] and 3.8 ± 1.4 vs. 2.9 ± 0.8, p = .05 [gray matter]). However, the responses were heterogeneous with pericontusional tissue demonstrating the least state-dependent change. Cerebral microdialysis demonstrated more frequent critical reductions in glucose (p = .02) and elevations of lactate/pyruvate ratio (p = .03) during tight glycemic control.

CONCLUSION

Tight glycemic control results in increased global glucose uptake and an increased cerebral metabolic crisis after traumatic brain injury. The mechanisms leading to the enhancement of metabolic crisis are unclear, but delivery of more glucose through mild hyperglycemia may be necessary after traumatic brain injury.

Relationship between systemic glucose and cerebral glucose is preserved in patients with severe traumatic brain injury, but glucose delivery to the brain may become limited when oxidative metabolism is impaired: implications for glycemic control

OBJECTIVE

To clarify the dynamics of glucose delivery to the brain and the effects of changes in blood glucose after severe traumatic brain injury.

DESIGN

Retrospective analysis of a prospective observational cohort study.

SETTING

Neurosurgical intensive care unit of a university hospital.

PATIENTS

Seventeen patients with acute traumatic brain injury monitored with cerebral and subcutaneous microdialysis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

For continuous, accurate systemic monitoring, glucose was measured in the interstitial space of subcutaneous adipose tissue using microdialysis, and 39 specific episodes of spontaneous rises in glucose were identified. During these episodes, there was a significant positive linear relationship between systemic glucose levels and brain glucose concentrations measured by microdialysis (p < .0001). The basal lactate/pyruvate ratio, with a threshold of 25, was adopted to distinguish between disturbed and presumably preserved cerebral oxidative metabolism. Using normal vs. elevated lactate/pyruvate ratio as variable factor, the relationship between brain and systemic glucose during the episodes could be described by two significantly distinct parallel lines (p = .0001), which indicates a strong additive effect of subcutaneous glucose and lactate/pyruvate ratio in determining brain glucose. The line describing the relationship under disturbed metabolic conditions was lower than in presumably intact metabolic conditions, with a significant difference of 0.648 ± 0.192 mM (p = .002). This let us to accurately predict that in this situation systemic glucose concentrations in the lower range of normality would result in critical brain glucose levels.

CONCLUSIONS

The linear relationship between systemic and brain glucose in healthy subjects is preserved in traumatic brain-injured patients. As a consequence, in brain tissue where oxidative metabolism is disturbed, brain glucose concentrations might possibly drop below the critical threshold of 0.8 mM to 1.0 mM when there is a reduction in systemic glucose toward the lower limits of the "normal" range.

[Guidelines for specialized nutritional and metabolic support in the critically-ill patient. Update. Consensus of the Spanish Society of Intensive Care Medicine and Coronary Units-Spanish Society of Parenteral and Enteral Nutrition (SEMICYUC-SENPE): neurocritical patient]

Neurocritical patients require specialized nutritional support due to their intense catabolism and prolonged fasting. The preferred route of nutrient administration is the gastrointestinal route, especially the gastric route. Alternatives are the transpyloric route or mixed enteral-parenteral nutrition if an effective nutritional volume of more than 60% cannot be obtained. Total calore intake ranges from 20-30 kcal/kg/day, depending on the period of the clinical course, with protein intake higher than 20% of total calories (hyperproteic diet). Nutritional support should be initiated early. The incidence of gastrointestinal complications is generally higher to other critically-ill patients, the most frequent complication being an increase in gastric residual volume. As in other critically-ill patients, glycemia should be closely monitored and maintained below 150 mg/dL.

Implementation of cerebral microdialysis at a community-based hospital: A 5-year retrospective analysis

Background:

Cerebral microdialysis (MD) provides valuable information about brain metabolism under normal and pathologic conditions. The CMA 600 microdialysis analyzer received US Food and Drug Administration (FDA) approval for clinical use in the United States in 2005. Since then, cerebral MD has been increasingly utilized nationally in the multimodal monitoring of traumatic brain injury (TBI), stroke, aneurysmal subarachnoid hemorrhage, and brain tumors. We describe a 5-year, single-institutional experience using cerebral MD at a community-based hospital, Legacy Emanuel Medical Center (LEMC). Implications for the adoption and utility of MD in medical centers with limited resources are discussed.

Methods:

This is a retrospective chart review and data analysis of 174 consecutive patients who had cerebral MD as part of multimodal brain monitoring. All cerebral MD catheters were placed by board-certified, attending neurosurgeons at LEMC. Clinical severity in the TBI patients was reported using initial Glasgow Coma Scale (GCS); radiologic severity was graded with the Marshall CT grading scale. Measures of the risks of MD placement included post-placement hemorrhage, cerebral infection, and dislodgement.

Results:

Between July 2005 and July 2010, 248 cerebral MD catheters were placed in 174 patients undergoing multimodal brain monitoring. One hundred and eighty-five catheters were placed at the time of open craniotomy. None were associated with cranial infection. Patients ranged in age from 5 months to 90 years, with a mean of 49 years. The male to female ratio was 1.4:1. The underlying pathologies were: TBI (126), cerebral vascular accident (24), aneurysmal subarachnoid hemorrhage (17), and tumor (7).

Conclusions:

Cerebral MD was readily implemented in a community-based hospital. No cerebral hemorrhages or infections were attributed to cerebral MD. Examples of how MD may be a useful adjunct in the clinical decision making of patients with brain injuries are presented.

Intensive insulin therapy in brain injury: a meta-analysis

Many studies have addressed the question of whether intensive insulin therapy (IIT) provides better outcomes for brain-injured patients than does conventional insulin therapy (CIT), with conflicting results. We performed a systematic review and meta-analysis of the literature to estimate the effect of IIT on patients with brain injury. We searched MEDLINE, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and citations of key articles and selected "all randomized controlled trials" (RCTs) comparing the effect of IIT to CIT among adult patients with acute brain injury (traumatic brain injury, stroke, subarachnoid hemorrhage, and encephalitis). Of the 2807 studies, we identified 9 RCTs with a total of 1160 patients for analysis. IIT did not appear to decrease the risk of in-hospital or late mortality (RR=1.04, 95% CI=0.75, 1.43 and RR=1.07, 95%CI=0.91, 1.27 respectively). No significant heterogeneity was found (I(2)=0.0%). IIT also did not have a protective effect on long-term neurological outcomes (LTNO) (RR=1.10, 95% CI=0.96, 1.27). IIT, however, did decrease the rate of infections (RR=0.76, 95% CI=0.58, 0.98). Heterogeneity was present (I(2)=64%), which was eliminated upon sensitivity analysis bringing the RR to 0.66 (95% CI=0.55, 0.80, I(2)=0%). IIT increased the rate of hypoglycemic episodes (RR=1.72, 95% CI=1.20, 2.46) however there was intractable heterogeneity present (I(2)=89%), which did not resolve upon sensitivity analysis. We found no evidence of publication bias by Egger's test (p=0.50). To conclude, IIT has no mortality or LTNO benefit to patients with brain injury, but is beneficial at decreasing infection rates.

Potential non-hypoxic/ischemic causes of increased cerebral interstitial fluid lactate/pyruvate ratio: a review of available literature

Microdialysis, an in vivo technique that permits collection and analysis of small molecular weight substances from the interstitial space, was developed more than 30 years ago and introduced into the clinical neurosciences in the 1990s. Today cerebral microdialysis is an established, commercially available clinical tool that is focused primarily on markers of cerebral energy metabolism (glucose, lactate, and pyruvate) and cell damage (glycerol), and neurotransmitters (glutamate). Although the brain comprises only 2% of body weight, it consumes 20% of total body energy. Consequently, the ability to monitor cerebral metabolism can provide significant insights during clinical care. Measurements of lactate, pyruvate, and glucose give information about the comparative contributions of aerobic and anaerobic metabolisms to brain energy. The lactate/pyruvate ratio reflects cytoplasmic redox state and thus provides information about tissue oxygenation. An elevated lactate pyruvate ratio (>40) frequently is interpreted as a sign of cerebral hypoxia or ischemia. However, several other factors may contribute to an elevated LPR. This article reviews potential non-hypoxic/ischemic causes of an increased LPR.

Studies of isolated global brain ischaemia: I. Overview of irreversible brain injury and evolution of a new concept - redefining the time of brain death

Despite advanced cardiac life support (ACLS), the mortality from sudden death after cardiac arrest is 85-95%, and becomes nearly 100% if ischaemia is prolonged, as occurs following unwitnessed arrest. Moreover, 33-50% of survivors following ACLS after witnessed arrest develop significant neurological dysfunction, and this rises to nearly 100% in the rare survivors of unwitnessed arrest. Although, whole body (cardiac) survival improves to 30% following recent use of emergency cardiopulmonary bypass, sustained neurological dysfunction remains a devastating and unresolved problem. Our studies suggest that both brain and whole body damage reflect an ischaemic/reperfusion injury that follows the present reperfusion methods that use normal blood, which we term 'uncontrolled reperfusion'. In contrast, we have previously introduced the term 'controlled reperfusion', which denotes controlling both the conditions (pressure, flow and temperature) as well as the composition (solution) of the reperfusate. Following prolonged ischaemia of the heart, lung and lower extremity, controlled reperfusion resulted in tissue recovery after ischaemic intervals previously thought to produce irreversible cellular injury. These observations underlie the current hypothesis that controlled reperfusion will become an effective treatment of the otherwise lethal injury of prolonged brain ischaemia, such as with unwitnessed arrest, and we tested this after 30 min of normothermic global brain ischaemia. This review, and the subsequent three studies will describe the evolution of the concept that controlled reperfusion will restore neurological function to the brain following prolonged (30 min) ischaemia. To provide a familiarity and rationale for these studies, this overview reviews the background and current treatment of sudden death, the concepts of controlled reperfusion, recent studies in the brain during whole body ischaemia, and then summarizes the three papers in this series on a new brain ischaemia model that endorses our hypothesis that controlled reperfusion allows complete neurological recovery following 30 min of normothermic global brain ischaemia. These findings may introduce innovative management approaches for sudden death, and perhaps stroke, because the brain is completely salvageable following ischaemic times thought previously to produce infarction.

Hyperglycemia in nondiabetic patients during the acute phase of stroke

OBJECTIVE

To determine patterns of hyperglycemic (HG) control in acute stroke.

METHODS

Anonymous survey through Internet questionnaire. Participants included Latin-American physicians specialized in neurocritical care.

RESULTS

The response rate was 74%. HG definition varied widely. Fifty per cent considered it when values were >140 mg/dL (7.8 mmol/L). Intravenous (IV) regular insulin was the drug of choice for HG correction. One fifth of the respondents expressed adherence to a protocol. Intensive insulin therapy (IIT) was used by 23%. Glucose levels were measured in all participants at admission. Routine laboratory test was the preferred method for monitoring. Reactive strips were more frequently used when monitoring was intensive. Most practitioners (56.7%) monitored glucose more than two times daily throughout the Intensive Care Unit stay.

CONCLUSIONS

There is considerable variability and heterogeneity in the management of elevated blood glucose during acute phase of stroke by the surveyed Latin-American physicians.

Contemporary view on neuromonitoring following severe traumatic brain injury

Evolving brain damage following traumatic brain injury (TBI) is strongly influenced by complex pathophysiologic cascades including local as well as systemic influences. To successfully prevent secondary progression of the primary damage we must actively search and identify secondary insults e.g. hypoxia, hypotension, uncontrolled hyperventilation, anemia, and hypoglycemia, which are known to aggravate existing brain damage. For this, we must rely on specific cerebral monitoring. Only then can we unmask changes which otherwise would remain hidden, and prevent adequate intensive care treatment. Apart from intracranial pressure (ICP) and calculated cerebral perfusion pressure (CPP), extended neuromonitoring (SjvO₂, ptiO₂, microdialysis, transcranial Doppler sonography, electrocorticography) also allows us to define individual pathologic ICP and CPP levels. This, in turn, will support our therapeutic decision-making and also allow a more individualized and flexible treatment concept for each patient. For this, however, we need to learn to integrate several dimensions with their own possible treatment options into a complete picture. The present review summarizes the current understanding of extended neuromonitoring to guide therapeutic interventions with the aim of improving intensive care treatment following severe TBI, which is the basis for ameliorated outcome.

Critical care management of severe traumatic brain injury in adults

Traumatic brain injury (TBI) is a major medical and socio-economic problem, and is the leading cause of death in children and young adults. The critical care management of severe TBI is largely derived from the "Guidelines for the Management of Severe Traumatic Brain Injury" that have been published by the Brain Trauma Foundation. The main objectives are prevention and treatment of intracranial hypertension and secondary brain insults, preservation of cerebral perfusion pressure (CPP), and optimization of cerebral oxygenation. In this review, the critical care management of severe TBI will be discussed with focus on monitoring, avoidance and minimization of secondary brain insults, and optimization of cerebral oxygenation and CPP.

Nutritional support and brain tissue glucose metabolism in poor-grade SAH: a retrospective observational study

Introduction

We sought to determine the effect of nutritional support and insulin infusion therapy on serum and brain glucose levels and cerebral metabolic crisis after aneurysmal subarachnoid hemorrhage (SAH).

Methods

We used a retrospective observational cohort study of 50 mechanically ventilated poor-grade (Hunt-Hess 4 or 5) aneurysmal SAH patients who underwent brain microdialysis monitoring for an average of 109 hours. Enteral nutrition was started within 72 hours of admission whenever feasible. Intensive insulin therapy was used to maintain serum glucose levels between 5.5 and 7.8 mmol/l. Serum glucose, insulin and caloric intake from enteral tube feeds, dextrose and propofol were recorded hourly. Cerebral metabolic distress was defined as a lactate to pyruvate ratio (LPR) > 40. Time-series data were analyzed using a general linear model extended by generalized estimation equations (GEE).

Results

Daily mean caloric intake received was 13.8 ± 6.9 cal/kg and mean serum glucose was 7.9 ± 1 mmol/l. A total of 32% of hourly recordings indicated a state of metabolic distress and < 1% indicated a state of critical brain hypoglycemia (< 0.2 mmol/l). Calories received from enteral tube feeds were associated with higher serum glucose concentrations (Wald = 6.07, P = 0.048), more insulin administered (Wald = 108, P < 0.001), higher body mass index (Wald = 213.47, P < 0.001), and lower body temperature (Wald = 4.1, P = 0.043). Enteral feeding (Wald = 1.743, P = 0.418) was not related to brain glucose concentrations after accounting for serum glucose concentrations (Wald = 67.41, P < 0.001). In the presence of metabolic distress, increased insulin administration was associated with a relative reduction of interstitial brain glucose concentrations (Wald = 8.26, P = 0.017), independent of serum glucose levels.

Conclusions

In the presence of metabolic distress, insulin administration is associated with reductions in brain glucose concentration that are independent of serum glucose levels. Further study is needed to understand how nutritional support and insulin administration can be optimized to minimize secondary injury after subarachnoid hemorrhage.

Microenvironment changes in mild traumatic brain injury

Traumatic brain injury (TBI) is a major public-health problem for which mild TBI (MTBI) makes up majority of the cases. MTBI is a poorly-understood health problem and can persist for years manifesting into neurological and non-neurological problems that can affect functional outcome. Presently, diagnosis of MTBI is based on symptoms reporting with poor understanding of ongoing pathophysiology, hence precluding prognosis and intervention. Other than rehabilitation, there is still no pharmacological treatment for the treatment of secondary injury and prevention of the development of cognitive and behavioural problems. The lack of external injuries and absence of detectable brain abnormalities lend support to MTBI developing at the cellular and biochemical level. However, the paucity of suitable and validated non-invasive methods for accurate diagnosis of MTBI poses as a substantial challenge. Hence, it is crucial that a clinically useful evaluation and management procedure be instituted for MTBI that encompasses both molecular pathophysiology and functional outcome. The acute microenvironment changes post-MTBI presents an attractive target for modulation of MTBI symptoms and the development of cognitive changes later in life.

The effects of insulin, glucagon, glutamate, and glucose infusion on blood glutamate and plasma glucose levels in naive rats

BACKGROUND

Elevated levels of glutamate in brain fluids, in the context of several neurodegenerative conditions, are associated with a worsened neurological outcome. Because there is a clear relationship between brain glutamate levels and glutamate levels in the blood, and an association of the latter with stress, the purpose of this study was to investigate the effects of glucose, insulin, and glucagon on rat blood glutamate levels.

METHODS

Rats received either 1 mL/100 g of rat body weight (BW) intravenous isotonic saline (control), 150 mg/1 mL/100 g BW intravenous glucose, 75 mg/1 mL/100 g BW intravenous glutamate, 50 g/100 g BW intraparitoneal glucagon, or 0.2 UI/100 g BW intraparitoneal insulin. Blood samples were subsequently drawn at 0, 30, 60, 90, and 120 minutes for determination of blood glutamate and glucose levels.

RESULTS

We observed a significant decrease in blood glutamate levels at 30 minutes after injection of glucose (P<0.05), at 30 and 60 minutes after injection of insulin (P<0.05), and at 90 and 120 minutes after injection of glucagon. Plasma glucose levels were elevated after infusion of glutamate and glucose but were decreased after injection of insulin.

CONCLUSIONS

The results of this study demonstrate that glucose, insulin, and glucagon significantly reduce blood glutamate levels. The effect of insulin is immediate and transient, whereas the effect of glucagon is delayed but longer lasting, suggesting that the sensitivity of pancreatic glucagon and insulin-secreting cells to glutamate is dependent on glucose concentration. The results of this study provide insight into blood glutamate homeostasis and may assist in the implementation of new therapies for brain neuroprotection from excess glutamate.

Relationship between hyperglycemia and outcome in children with severe traumatic brain injury

OBJECTIVE

To determine the relationship between hyperglycemia and outcome in infants and children after severe traumatic brain injury.

DESIGN

Retrospective review of a prospectively collected Pediatric Neurotrauma Registry.

SETTING AND PATIENTS

Children admitted after severe traumatic brain injury (postresuscitation Glasgow Coma Scale ≤ 8) were studied (1999-2004). A subset of children (n = 28) were concurrently enrolled in a randomized, controlled clinical trial of early hypothermia for neuroprotection.

INTERVENTIONS

Demographic data, serum glucose concentrations, and outcome assessments were collected.

METHODS AND MAIN RESULTS

Children (n = 57) were treated with a standard traumatic brain injury protocol. Exogenous glucose was withheld for 48 hrs after injury unless hypoglycemia was observed (blood glucose <70 mg/dL). Early (first 48 hrs) and Late (49-168 hrs) time periods were defined and mean blood glucose concentrations were calculated. Additionally, children were categorized based on peak blood glucose concentrations during each time period (normal, blood glucose <150 mg/dL; mild hyperglycemia, blood glucose ≤ 200 mg/dL; severe hyperglycemia, blood glucose >200 mg/dL). In the Late period, an association between elevated mean serum glucose concentration and outcome was observed (133.5 ± 5.6 mg/dL in the unfavorable group vs. 115.4 ± 4.1 mg/dL in favorable group, p = .02). This association continued to be significant after correcting for injury severity, age, and exposure to insulin (p = .03). Similarly, in the Late period, children within the severe hyperglycemia group had decreased incidence of good outcome compared to children within the other glycemic groups (% good outcome: normal, 61.9%; mild hyperglycemia, 73.7%; severe hyperglycemia, 33.3%; p = .05). However, when adjusted for exposure to insulin, this relationship was no longer statistically significant.

CONCLUSIONS

In children with severe traumatic brain injury, hyperglycemia beyond the initial 48 hrs is associated with poor outcome. This relationship was observed in both our analysis of mean blood glucose concentrations as well as among the patients with episodic severe hyperglycemia. This observation suggests a relationship between hyperglycemia and outcome from traumatic brain injury. However, only a prospective study can answer the important question of whether manipulating serum glucose concentration can improve outcome after traumatic brain injury in children.

Glucose control and mortality in patients with severe traumatic brain injury

INTRODUCTION

The optimal glucose range in patients with severe traumatic brain injury (TBI) remains unclear. The goal of this study was to examine the association of serum glucose levels on mortality in patients with severe TBI. As a secondary endpoint, we determined the risk of hyperglycemic and hypoglycemic events, and their association with mortality.

METHODS

We conducted a retrospective cohort study of patients admitted to the ICU between May 2000 and March 2006 with severe TBI (Glasgow Coma Scale ≤ 8) who survived at least 12 h. Average daily morning glucose levels for the first 10 days of admission were calculated and divided into quintiles.

RESULTS

A total of 170 patients were included in the analysis. We found no association between quintiles of mean daily morning glucose and hospital mortality. Episodes of hyperglycemia ( ≥ 11.1 mmol/l or 200 mg/dl) during the first 10 days occurred in 65% of patients (5.4% of all glucose measurements). Using multivariable regression, a single episode of hyperglycemia was associated with 3.6-fold increased risk of hospital mortality (95%CI: 1.2-11.2, P = 0.02). Hypoglycemia ( ≤ 4.4 mmol/l or 80 mg/dl) was present in 48% of patients (4.3% of all glucose measurements), and was not associated with mortality.

CONCLUSION

Any episode of hyperglycemia ( ≥ 11.1 mmol/l or 200 mg/dl) was associated with 3.6-fold increased risk of hospital mortality in patients with severe TBI and thus, should be avoided. Maintaining serum glucose ≤ 10 mmol/l appears to be a reasonable balance to avoid extremes of glucose control, but further studies are needed to determine the optimal glucose range.

Relation between brain interstitial and systemic glucose concentrations after subarachnoid hemorrhage

OBJECT

The aim in the present investigation was to study the relation between brain interstitial and systemic blood glucose concentrations during the acute phase after subarachnoid hemorrhage (SAH). The authors also evaluated the effects of insulin administration on local brain energy metabolism.

METHODS

Nineteen patients with spontaneous SAH were prospectively monitored with intracerebral microdialysis (MD). The relation between plasma glucose and MD-measured interstitial brain glucose concentrations as well as the temporal pattern of MD glucose, lactate, pyruvate, glutamate, and glycerol was studied for 7 days after SAH. Using a target plasma glucose concentration of 5-10 mmol/L, the effect of insulin injection was also evaluated.

RESULTS

The mean (± SD) correlation coefficient between plasma glucose and MD glucose was 0.27 ± 0.27 (p = 0.0005), with a high degree of individual variation. Microdialysis glucose, the MD/plasma glucose ratio, and MD glutamate concentrations decreased in parallel with a gradual increase in MD pyruvate and MD lactate concentrations. There were no significant changes in the MD L/P ratio or MD glycerol levels. Insulin administration induced a decrease in MD glucose and MD pyruvate.

CONCLUSIONS

After SAH, there was a positive correlation between plasma and MD glucose concentrations with a high degree of individual variation. A gradual decline in MD glucose and the MD/plasma glucose ratio and an increase in MD pyruvate and MD lactate concentrations during the 1st week after SAH suggest a transition to a hyperglycolytic state with increased cerebral glucose consumption. The administration of insulin was related to a lowering of MD glucose and MD pyruvate, often to low levels even though plasma glucose values remained above 6 mmol/L. After SAH, the administration of insulin could impede the glucose supply of the brain.

Multimodal Cerebral Monitoring in Traumatic Brain Injury

Traumatic brain injury presents a significant impact on patients in terms of morbidity and mortality. Pathology is heterogeneous and is often associated with secondary deterioration. This paper reviews both clinical and research modes of monitoring to detect deterioration and compares what is available to the ideal. Intracranial pressure measurement, jugular venous oxygen saturation, microdialysis and cerebral oxygen monitoring are among the variables described and future research-based modalities are explored.

Detection of Cerebral Compromise With Multimodality Monitoring in Patients With Subarachnoid Hemorrhage

BACKGROUND:

Studies in traumatic brain injury suggest that monitoring techniques such as brain tissue oxygen (Pbto2) and cerebral microdialysis may complement conventional intracranial pressure (ICP) and cerebral perfusion pressure (CPP) measurements.

OBJECTIVE:

In this study of poor-grade (Hunt and Hess grade IV and V) subarachnoid hemorrhage (SAH) patients, we examined the prevalence of brain hypoxia and brain energy dysfunction in the presence of normal and abnormal ICP and CPP.

METHODS:

SAH patients who underwent multimodal neuromonitoring and cerebral microdialysis were studied. We examined the frequency of brain hypoxia and energy dysfunction in different ICP and CPP ranges and the relationship between Pbto2 and the lactate/pyruvate ratio (LPR).

RESULTS:

A total of 2394 samples from 19 patients were analyzed. There were 149 samples with severe brain hypoxia (Pbto2 ≤10 mm Hg) and 347 samples with brain energy dysfunction (LPR &gt;40). The sensitivities of abnormal ICP or CPP for elevated LPR and reduced Pbto2 were poor (21.2% at best), and the LPR or Pbto2 was abnormal in many instances when ICP or CPP was normal. Severe brain hypoxia was often associated with an LPR greater than 40 (86% of samples). In contrast, mild brain hypoxia (≤20 mm Hg) and severe brain hypoxia were observed in only 53% and 36% of samples with brain energy dysfunction, respectively.

CONCLUSION:

Our data demonstrate that ICP and CPP monitoring may not always detect episodes of cerebral compromise in SAH patients. Our data suggest that several complementary monitors may be needed to optimize the care of poor-grade SAH patients.

Treating hyperglycemia in neurocritical patients: benefits and perils

There is growing debate over the value of intensive insulin therapy (IIT) in critically ill patients. Available trials have been performed in general medical or surgical intensive care units, and the results may not be directly applicable to patients with severe acute brain disease because these patients may have heightened susceptibility to hyperglycemia (HyperG) and hypoglycemia. Our objective was to review the pathophysiology and effects of HyperG and hypoglycemia in neurocritical patients and to analyze the potential role of IIT in this population. Source data were obtained from a PubMed search of the medical literature combining the terms HyperG, hypoglycemia, insulin, stroke, intracerebral hemorrhage (ICH), subarachnoid hemorrhage (SAH), traumatic brain injury (TBI), spinal cord injury (SCI), and related diagnoses. Brain metabolism is highly dependent on constant supply of glucose. As a consequence, the acutely injured brain is particularly sensitive to hypoglycemia, which can induce a state of energy failure (metabolic crisis). Meanwhile, neurocritical patients have a high prevalence of HyperG, and its occurrence is associated with poor outcome after acute ischemic stroke, ICH, SAH, and TBI. It is unclear whether this association is due to direct detrimental effects exerted by HyperG or simply represents a marker of severe brain injury. Insulin has been shown to have various potentially pleiotropic neuroprotective properties in experimental models. However, the safety and efficacy of IIT in patients with critical brain disease have not been well studied. Available results do not support the use of IIT to maintain strict normoglycemia in this population. Patients with critical brain disease should have frequent glucose monitoring because severe HyperG and even modest hypoglycemia may be detrimental. Careful use of insulin infusion protocols appears advisable, but maintenance of strict normoglycemia cannot be recommended. Rigorous studies must be conducted to assess the value of insulin therapy and to determine the optimal blood glucose targets in patients with the most common acute vascular and traumatic brain insults.

The molecular pathophysiology of concussive brain injury

Concussion or mild traumatic brain injury (mTBI) is a condition that affects hundreds of thousands of patients worldwide. Understanding the pathophysiology of this disorder can help manage its acute and chronic repercussions. Immediately following mTBI, there are several metabolic, hemodynamic, structural, and electric changes that alter normal cerebral function. These alterations can increase the brain's vulnerability to repeat injury and long-term disability. This review evaluates current studies from the bench to the bedside of mTBI. Acute and chronic effects of concussion are measured in both animal and clinical studies. Also, the effect of repeat concussions is analyzed. Concussion-induced pathophysiology with regards to glucose metabolism changes, mitochondrial dysfunction, axonal injury, and structural damage are evaluated. Translational studies such as functional magnetic resonance imaging, magnetic resonance spectroscopy and diffusion tensor imaging prove to be effective clinical tools for both prognostic and treatment parameters. Understanding the neurobiology of concussion will lead to development and validation of physiological biomarkers of this common injury. These biomarkers (eg, laboratory tests, imaging, electrophysiology) will then allow for improved detection, better functional assessment and evidence-based return to play recommendations.

High blood glucose does not adversely affect outcome in moderately brain-injured rodents

In a number of clinical studies researchers have reported that acute hyperglycemia is associated with increased mortality and worsened neurological outcome in patients with traumatic brain injury (TBI). In contrast, it has been demonstrated that intensive insulin therapy to lower blood glucose can lead to an increased frequency of hypoglycemic episodes and poor outcome. Consistent with this, experimental and clinical studies have shown that TBI causes a "metabolic crisis" in the injured brain, suggesting that a reduction in glucose availability may exacerbate brain damage. We therefore examined the consequences of hyperglycemia on cognitive and pathological measures. Using a rodent model of TBI, we find that when acute hyperglycemia is induced in animals prior to injury, there is little to no change in motor and cognitive performance, contusion volume, or cerebral edema. To examine the consequences of persistent hyperglycemia (as seen in diabetic patients), animals were treated with streptozotocin (STZ) to induce type 1 diabetes. We find that the presence of persistent STZ-induced hyperglycemia results in a reduction of brain edema. Insulin therapy to reduce blood glucose reverses this beneficial effect of hyperglycemia. Taken together, our results indicate that an acute increase in blood glucose levels may not be harmful, and that intervention with insulin therapy to lower blood glucose levels in TBI patients may increase secondary brain damage.

Neuromonitoring for Traumatic Brain Injury in Neurosurgical Intensive Care

The primary aim of neuromonitoring in patients with traumatic brain injury is early detection of secondary brain insults so that timely interventions can be instituted to prevent or treat secondary brain injury. Intracranial pressure monitoring has been a stalwart in neuromonitoring and is still very much the main parameter to guide therapy in brain injured patients in many centres. Cerebral oxygenation is also established as an important parameter for monitoring: global cerebral oxygenation is reliably measured using jugular venous oxygen saturation while brain tissue oxygen tension measurement allows focal brain oxygenation to be monitored. Near-infrared spectroscopy allows a non-invasive option for monitoring of regional cerebral oxygenation. Cerebral microdialysis makes focal measurements of markers of cellular metabolism and cellular injury and death possible, and it is in transition from being a research tool to being an important clinical tool in neuromonitoring. Multimodal monitoring allows different parameters of brain physiology and function to be monitored and can improve identification and prediction of secondary cerebral insults. Multimodal monitoring can potentially improve outcomes in patients with traumatic brain injury by promoting customised treatment strategies for individual patients in place of the commonplace practice of strict adherence to achieving the same standard physiological targets for every patient.

Intensive versus conventional insulin therapy in critically ill neurologic patients

BACKGROUND

Previous studies of glycemic control in non-neurologic ICU patients have shown conflicting results. The purpose was to investigate whether intensive insulin therapy (IIT) to keep blood glucose levels from 80 to 110 mg/dl or conventional treatment to keep levels less than 151 mg/dl was associated with a reduction of mortality and improved functional outcome in critically ill neurologic patients.

METHODS

Within 24 h of ICU admission, mechanically ventilated adult neurologic patients were enrolled after written informed consent and randomized to intensive or conventional control of blood glucose levels with insulin. Primary outcome measure was death within 3 months. Secondary outcome measures included 90-day modified Rankin scale (mRS) score, ICU, and hospital LOS.

RESULTS

81 patients were enrolled. The proportion of deaths was higher among IIT patients but this was not statistically significant (36 vs. 25%, P = 0.34). When good versus poor outcome at 3 months was dichotomized to mRS score 0-2 versus 3-6, respectively, there was no difference in outcome between the two groups (76.2 vs. 75% had a poor 3-month outcome, P = 1.0). There was also no difference in ICU or hospital LOS. Hypoglycemia (<60 mg/dl) and severe hypoglycemia (<40 mg/dl) were more common in the intensive arm (48 vs. 11%, P = 0.0006; and 4 vs. 0%, P = 0.5, respectively).

CONCLUSION

There was no benefit to IIT in this small critically ill neurologic population. This is the first glycemic control study to specifically examine both critically ill stroke and traumatic brain injury (TBI) patients and functional outcome. Given these results, IIT cannot be recommended over conventional control.

Analytic review: glucose controversies in the ICU

Hyperglycemia is common in critical illness and has been associated with increased morbidity and mortality. An era of tight glucose control began when intensive insulin therapy was shown to improve outcomes in a single-center randomized trial. More recently, with the publication of additional studies, questions have been raised regarding the efficacy and safety of intensive glycemic management. This article will review the biologic mechanisms that may help us understand why and how hyperglycemia and insulin are relevant in critical illness. We will then explore insights gleaned from available clinical trials. Finally, we will discuss specific areas of controversy that relate to the implementation of glycemic control in the intensive care unit, such as the ideal glucose target and the importance of hypoglycemia.

Astrocyte oxidative metabolism and metabolite trafficking after fluid percussion brain injury in adult rats

Despite various lines of evidence pointing to the compartmentation of metabolism within the brain, few studies have reported the effect of a traumatic brain injury (TBI) on neuronal and astrocyte compartments and/or metabolic trafficking between these cells. In this study we used ex vivo ¹³C NMR spectroscopy following an infusion of [1-¹³C] glucose and [1,2-¹³C₂] acetate to study oxidative metabolism in neurons and astrocytes of sham-operated and fluid percussion brain injured (FPI) rats at 1, 5, and 14 days post-surgery. FPI resulted in a decrease in the ¹³C glucose enrichment of glutamate in neurons in the injured hemisphere at day 1. In contrast, enrichment of glutamine in astrocytes from acetate was not significantly decreased at day 1. At day 5 the ¹³C enrichment of glutamate and glutamine from glucose in the injured hemisphere of FPI rats did not differ from sham levels, but glutamine derived from acetate metabolism in astrocytes was significantly increased. The ¹³C glucose enrichment of the C3 position of glutamate (C3) in neurons was significantly decreased ipsilateral to FPI at day 14, whereas the enrichment of glutamine in astrocytes had returned to sham levels at this time point. These findings indicate that the oxidative metabolism of glucose is reduced to a greater extent in neurons compared to astrocytes following a FPI. The increased utilization of acetate to synthesize glutamine, and the acetate enrichment of glutamate via the glutamate-glutamine cycle, suggests an integral protective role for astrocytes in maintaining metabolic function following TBI-induced impairments in glucose metabolism.

Microdialysis for assessing intratumoral drug disposition in brain cancers: a tool for rational drug development

IMPORTANCE OF THE FIELD

many promising targeted agents and combination therapies are being investigated for brain cancer. However, the results from recent clinical trials have been disappointing. A better understanding of the disposition of drug in the brain early in drug development would facilitate appropriate channeling of new drugs into brain cancer clinical trials.

AREAS COVERED IN THIS REVIEW

barriers to successful drug activity against brain cancer and issues affecting intratumoral drug concentrations are reviewed. The use of the microdialysis technique for extracellular fluid (ECF) sampling and its application to drug distribution studies in brain are reviewed using published literature from 1995 to the present. The benefits and limitations of microdialysis for performing neuorpharmacokinetic (nPK) and neuropharmacodynamic (nPD) studies are discussed.

WHAT THE READER WILL GAIN

the reader will gain an appreciation of the challenges involved in identifying agents likely to have efficacy in brain cancer, an understanding of the general principles of microdialysis, and the power and limitations of using this technique in early drug development for brain cancer therapies.

TAKE HOME MESSAGE

a major factor preventing efficacy of anti-brain cancer drugs is limited access to tumor. Intracerebral microdialysis allows sampling of drug in the brain ECF. The resulting nPK/nPD data can aid in the rational selection of drugs for investigation in brain tumor clinical trials.

The neurosurgical and acute care management of tuberculous meningitis: evidence and current practice

Tuberculous meningitis (TBM) is the most lethal form of tuberculosis; mortality is high and survivors are often left neurologically disabled. Several factors contribute to this poor outcome, including cerebrovascular involvement with ensuing brain ischemia, hydrocephalus and raised intracranial pressure, direct parenchymal injury, hyponatremia, and seizures. However, there is little standardisation of management with respect to these aspects of care across different centers, largely because the evidence base for much of the supportive treatment of patients with TBM is poor, leading to substantial differences in management protocols. This review emphasizes some of the uncertainties and controversies pertinent to the surgical treatment of hydrocephalus in TBM and the medical supportive management of the patient during the acute phase of the illness, with the aims of raising awareness and stimulating debate. The focus is on the management of hyponatremia, cerebral hemodynamics and intracranial pressure, medical and surgical treatment for hydrocephalus, and the intensive care management of patients in the acute severe stage of the illness. Very little data are available to address these issues with good evidence and so institutional preferences are common; this is perhaps most notable for the management of hydrocephalus, and so in this the review highlights our personal practice. The brain needs protection while the source of the illness is addressed. Without attention to these aspects of management there will always be a limit to the effectiveness of antimicrobial therapy in TBM, so there is a strong imperative for the controversies to be resolved and the limitations of our current care to be addressed. Existing protocols should be rigorously examined and novel strategies to protect the brain should be explored. To this end, a prospective, multi-disciplinary and multi-centered approach may yield answers to the questions raised in this review.

The effects of age and ketogenic diet on local cerebral metabolic rates of glucose after controlled cortical impact injury in rats

Previous studies from our laboratory have shown the neuroprotective potential of ketones after TBI in the juvenile brain. It is our premise that acutely after TBI, glucose may not be the optimum fuel and decreasing metabolism of glucose in the presence of an alternative substrate will improve cellular metabolism and recovery. The current study addresses whether TBI will induce age-related differences in the cerebral metabolic rates for glucose (CMRglc) after cortical controlled impact (CCI) and whether ketone metabolism will further decrease CMRglc after injury. Postnatal day 35 (PND35; n = 48) and PND70 (n = 42) rats were given either sham or CCI injury and placed on either a standard or a ketogenic (KG) diet. CMRglc studies using (14)C-2 deoxy-D-glucose autoradiography were conducted on days 1, 3, or 7 post-injury. PND35 and PND70 standard-fed CCI-injured rats exhibited no significant neocortical differences in CMRglc magnitude or time course compared to controls. Measurement of contusion volume also indicated no age differences in response to TBI. However, PND35 subcortical structures showed earlier metabolic recovery compared to controls than PND70. Ketosis induced by the KG diet was shown to affect CMRglc in an age-dependent manner after TBI. The presence of ketones after injury further reduced CMRglc in PND35 and normalized CMRglc in PND70 rats at 7 days bilaterally after injury. The changes in CMRglc seen in PND35 TBI rats on the KG diet were associated with decreased contusion volume. These results suggest that conditions of reduced glucose utilization and increased alternative substrate metabolism may be preferable acutely after TBI in the younger rat.

Hyperglycemia in aneurysmal subarachnoid hemorrhage: a potentially modifiable risk factor for poor outcome

Hyperglycemia after aneurysmal subarachnoid hemorrhage (aSAH) occurs frequently and is associated with delayed cerebral ischemia (DCI) and poor clinical outcome. In this review, we highlight the mechanisms that cause hyperglycemia after aSAH, and we discuss how hyperglycemia may contribute to poor clinical outcome in these patients. As hyperglycemia is potentially modifiable with intensive insulin therapy (IIT), we systematically reviewed the literature on IIT in aSAH patients. In these patients, IIT seems to be difficult to achieve in terms of lowering blood glucose levels substantially without an increased risk of (serious) hypoglycemia. Therefore, before initiating a large-scale randomized trial to investigate the clinical benefit of IIT, phase II studies, possibly with the help of cerebral blood glucose monitoring by microdialysis, will first have to improve this therapy in terms of both safety and adequacy.

Hyponatremia and brain injury: absence of alterations of serum brain natriuretic peptide and vasopressin

OBJECTIVE

To study any possible relation between hyponatremia following brain injury and the presence of cerebral salt-wasting syndrome (CSWS) or the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), and if vasopressin, brain natriuretic peptide (BNP) and aldosterone have a role in its mechanism.

METHOD

Patients with brain injury admitted to the intensive care unit were included and had their BNP, aldosterone and vasopressin levels dosed on day 7.

RESULTS

Twenty six adult patients were included in the study. Nine (34.6%) had hyponatremia and presented with a negative water balance and higher values of urinary sodium, serum potassium and diuresis than patients with normonatremia. The serum levels of BNP, aldosterone, and vasopressin were normal and no relation was observed between plasma sodium and BNP, aldosterone or vasopressin.

CONCLUSION

The most likely cause of hyponatremia was CSWS and there was no correlation between BNP, aldosterone and vasopressin with serum sodium level.

Current and future treatment considerations in the management of aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a type of hemorrhagic stroke that can cause significant morbidity and mortality. Although guidelines have been published to help direct the care of these patients, there is insufficient quality literature regarding the medical and pharmacological management of patients with aSAH. Treatment is divided into 3 categories: supportive therapy, prevention of complications, and treatment of complications. There are numerous pharmacological therapies that are targeted at prevention and treatment of the neurological and medical complications that may arise. Rebleeding, hydrocephalus, cerebral vasospasm, and seizures are the most common neurological complications while the most common medical complications include hyponatremia, pulmonary edema, cardiac arrhythmias, neurogenic stunned myocardium, fever, anemia, infection, hyperglycemia, and venous thromboembolism. Risk factors, clinical presentation, diagnosis, pathophysiology, as well as initial management, prevention, and treatment of complications will be the focus of this discussion.

Management of spontaneous nontraumatic intracranial hemorrhage

Intracerebral hemorrhage (ICH) is one of the most devastating subtypes of stroke and is characterized by spontaneous extravasation into the parenchymal tissue of the brain. Although advances in critical care have improved, there is no intervention currently available that has shown to alter the outcome of patients who have suffered acute ICH. Therefore, management is largely supportive. Treatment strategies are aimed at limiting hematoma enlargement, seizures, and cerebral edema, as well as other ICU-related complications such as deep venous thrombosis, hyperglycemia, and fever. This review will outline the key pharmacological management strategies in patients with ICH and highlight the most current American Heart Association/American Stroke Association (AHA/ASA) guidelines for management published in 2007.