Prognostic value of admission laboratory parameters in traumatic brain injury: results from the IMPACT study

Anemia, red blood cell transfusion, and outcomes after severe traumatic brain injury

In the previous issue of Critical Care, Sekhon and colleagues report that mean 7-day hemoglobin concentration <90 g/l was associated with increased mortality among patients with severe traumatic brain injury (TBI). The adverse relationship between reduced hemoglobin concentrations and outcomes among those with TBI has been an inconsistent finding across available studies. However, as anemia is common among adults with severe TBI, and clinical equipoise may exist between specialists as to when to transfuse allogeneic red blood cells, randomized controlled trials of liberal versus restricted transfusion thresholds are indicated.

The clinical significance of platelet counts in the first 24 hours after severe injury

BACKGROUND

Admission platelet (PLT) counts are known to be associated with all-cause mortality for seriously injured patients admitted to a trauma center. The course of subsequent PLT counts, their implications, and the effects of PLT therapy are less well known.

STUDY DESIGN AND METHODS

Trauma center patients who were directly admitted from the scene of injury, received 1 or more units of uncrossmatched red blood cells in the first hour of care, survived for at least 15 minutes, and had a PLT count measured in the first hour were analyzed for the association of their admission and subsequent PLT counts in the first 24 hours with injury severity and hemorrhagic and central nervous system (CNS) causes of in-hospital mortality.

RESULTS

Over an 8.25-year period, 1292 of 45,849 direct trauma admissions met entry criteria. Admission PLT counts averaged 228×10(9) ±90×10(9) /L and decreased by 104×10(9) /L by the second hour and 1×10(9) /L each hour thereafter. The admission count was not related to time to admission. Each 1-point increase in the injury severity score was associated with a 1×10(9) /L decrease in the PLT count at all times in the first 24 hours of care. Admission PLT counts were strongly associated with hemorrhagic and CNS injury mortality and subsequent PLT counts. Effects of PLT therapy could not be ascertained.

DISCUSSION

Admission PLT counts in critically injured trauma patients are usually normal, decreasing after admission. Low PLT counts at admission and during the course of trauma care are strongly associated with mortality.

Outcome prediction within twelve hours after severe traumatic brain injury by quantitative cerebral blood flow

We measured quantitative cortical mantle cerebral blood flow (CBF) by stable xenon computed tomography (CT) within the first 12 h after severe traumatic brain injury (TBI) to determine whether neurologic outcome can be predicted by CBF stratification early after injury. Stable xenon CT was used for quantitative measurement of CBF (mL/100 g/min) in 22 cortical mantle regions stratified as follows: low (0-8), intermediate (9-30), normal (31-70), and hyperemic (>70) in 120 patients suffering severe (Glasgow Coma Scale [GCS] score ≤8) TBI. For each of these CBF strata, percentages of total cortical mantle volume were calculated. Outcomes were assessed by Glasgow Outcome Scale (GOS) score at discharge (DC), and 1, 3, and 6 months after discharge. Quantitative cortical mantle CBF differentiated GOS 1 and GOS 2 (dead or vegetative state) from GOS 3-5 (severely disabled to good recovery; p<0.001). Receiver operating characteristic (ROC) curve analysis for percent total normal plus hyperemic flow volume (TNHV) predicting GOS 3-5 outcome at 6 months for CBF measured <6 and <12 h after injury showed ROC area under the curve (AUC) cut-scores of 0.92 and 0.77, respectively. In multivariate analysis, percent TNHV is an independent predictor of GOS 3-5, with an odds ratio of 1.460 per 10 percentage point increase, as is initial GCS score (OR=1.090). The binary version of the Marshall CT score was an independent predictor of 6-month outcome, whereas age was not. These results suggest that quantitative cerebral cortical CBF measured within the first 6 and 12 h after TBI predicts 6-month outcome, which may be useful in guiding patient care and identifying patients for randomized clinical trials. A larger multicenter randomized clinical trial is indicated.

Principal component analysis of the cytokine and chemokine response to human traumatic brain injury

There is a growing realisation that neuro-inflammation plays a fundamental role in the pathology of Traumatic Brain Injury (TBI). This has led to the search for biomarkers that reflect these underlying inflammatory processes using techniques such as cerebral microdialysis. The interpretation of such biomarker data has been limited by the statistical methods used. When analysing data of this sort the multiple putative interactions between mediators need to be considered as well as the timing of production and high degree of statistical co-variance in levels of these mediators. Here we present a cytokine and chemokine dataset from human brain following human traumatic brain injury and use principal component analysis and partial least squares discriminant analysis to demonstrate the pattern of production following TBI, distinct phases of the humoral inflammatory response and the differing patterns of response in brain and in peripheral blood. This technique has the added advantage of making no assumptions about the Relative Recovery (RR) of microdialysis derived parameters. Taken together these techniques can be used in complex microdialysis datasets to summarise the data succinctly and generate hypotheses for future study.

Individual participant data meta-analysis of prognostic factor studies: state of the art?

Background

Prognostic factors are associated with the risk of a subsequent outcome in people with a given disease or health condition. Meta-analysis using individual participant data (IPD), where the raw data are synthesised from multiple studies, has been championed as the gold-standard for synthesising prognostic factor studies. We assessed the feasibility and conduct of this approach.

Methods

A systematic review to identify published IPD meta-analyses of prognostic factors studies, followed by detailed assessment of a random sample of 20 articles published from 2006. Six of these 20 articles were from the IMPACT (International Mission for Prognosis and Analysis of Clinical Trials in traumatic brain injury) collaboration, for which additional information was also used from simultaneously published companion papers.

Results

Forty-eight published IPD meta-analyses of prognostic factors were identified up to March 2009. Only three were published before 2000 but thereafter a median of four articles exist per year, with traumatic brain injury the most active research field. Availability of IPD offered many advantages, such as checking modelling assumptions; analysing variables on their continuous scale with the possibility of assessing for non-linear relationships; and obtaining results adjusted for other variables. However, researchers also faced many challenges, such as large cost and time required to obtain and clean IPD; unavailable IPD for some studies; different sets of prognostic factors in each study; and variability in study methods of measurement. The IMPACT initiative is a leading example, and had generally strong design, methodological and statistical standards. Elsewhere, standards are not always as high and improvements in the conduct of IPD meta-analyses of prognostic factor studies are often needed; in particular, continuous variables are often categorised without reason; publication bias and availability bias are rarely examined; and important methodological details and summary results are often inadequately reported.

Conclusions

IPD meta-analyses of prognostic factors are achievable and offer many advantages, as displayed most expertly by the IMPACT initiative. However such projects face numerous logistical and methodological obstacles, and their conduct and reporting can often be substantially improved.

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.

Hemorrhagic progression of a contusion after traumatic brain injury: a review

The magnitude of damage to cerebral tissues following head trauma is determined by the primary injury, caused by the kinetic energy delivered at the time of impact, plus numerous secondary injury responses that almost inevitably worsen the primary injury. When head trauma results in a cerebral contusion, the hemorrhagic lesion often progresses during the first several hours after impact, either expanding or developing new, non-contiguous hemorrhagic lesions, a phenomenon termed hemorrhagic progression of a contusion (HPC). Because a hemorrhagic contusion marks tissues with essentially total unrecoverable loss of function, and because blood is one of the most toxic substances to which the brain can be exposed, HPC is one of the most severe types of secondary injury encountered following traumatic brain injury (TBI). Historically, HPC has been attributed to continued bleeding of microvessels fractured at the time of primary injury. This concept has given rise to the notion that continued bleeding might be due to overt or latent coagulopathy, prompting attempts to normalize coagulation with agents such as recombinant factor VIIa. Recently, a novel mechanism was postulated to account for HPC that involves delayed, progressive microvascular failure initiated by the impact. Here we review the topic of HPC, we examine data relevant to the concept of a coagulopathy, and we detail emerging data elucidating the mechanism of progressive microvascular failure that predisposes to HPC after head trauma.

Multicenter evaluation of the course of coagulopathy in patients with isolated traumatic brain injury: relation to CT characteristics and outcome

This prospective multicenter study investigated the association of the course of coagulation abnormalities with initial computed tomography (CT) characteristics and outcome in patients with isolated traumatic brain injury (TBI). Patient demographics, coagulation parameters, CT characteristics, and outcome data of moderate and severe TBI patients without major extracranial injuries were prospectively collected. Coagulopathy was defined as absent, early but temporary, delayed, or early and sustained. Delayed/sustained coagulopathy was associated with a higher incidence of disturbed pupillary responses (40% versus 27%; p<0.001) and higher Traumatic Coma Data Bank (TCDB) CT classification (5 (2-5) versus 2 (1-5); p=0.003) than in patients without or with early, but short-lasting coagulopathy. The initial CT of patients with delayed/sustained coagulopathy more frequently showed intracranial hemorrhage and signs of raised intracranial pressure (ICP) compared to patients with early coagulopathy only. This was paralleled by higher in-hospital mortality rates (51% versus 33%; p<0.05), and poorer 6-month functional outcome in patients with delayed/sustained coagulopathy. The relative risk for in-hospital mortality was particularly related to disturbed pupillary responses (OR 8.19; 95% CI 3.15,21.32; p<0.001), early, short-lasting coagulopathy (OR 6.70; 95% CI 1.74,25.78; p=0.006), or delayed/sustained coagulopathy (OR 5.25; 95% CI 2.06,13.40; p=0.001). Delayed/sustained coagulopathy is more frequently associated with CT abnormalities and unfavorable outcome at 6 months after TBI than early, short-lasting coagulopathy. Our finding that not only the mere presence but also the time course of coagulopathy holds predictive value for patient outcome underlines the importance of systematic hemostatic monitoring over time in TBI.

A normal platelet count may not be enough: the impact of admission platelet count on mortality and transfusion in severely injured trauma patients

BACKGROUND

Platelets play a central role in hemostasis after trauma. However, the platelet count of most trauma patients does not fall below the normal range (100-450 × 10(9)/L), and as a result, admission platelet count has not been adequately investigated as a predictor of outcome. The purpose of this study was to examine the relationship between admission platelet count and outcomes after trauma.

METHODS

A retrospective cohort study of 389 massively transfused trauma patients. Regression methods and the Kruskal-Wallis test were used to test the association between admission platelet count and 24-hour mortality and units of packed red blood cells (PRBCs) transfused.

RESULTS

For every 50 × 10(9)/L increase in admission platelet count, the odds of death decreased 17% at 6 hours (p = 0.03; 95% confidence interval [CI], 0.70-0.99) and 14% at 24 hours (p = 0.02; 95% CI, 0.75-0.98). The probability of death at 24 hours decreased with increasing platelet count. For every 50 × 10(9)/L increase in platelet count, patients received 0.7 fewer units of blood within the first 6 hours (p = 0.01; 95% CI, -1.3 to -0.14) and one less unit of blood within the first 24 hours (p = 0.002; 95% CI, -1.6 to -0.36). The mean number of units of PRBCs transfused within the first 6 hours and 24 hours decreased with increasing platelet count.

CONCLUSIONS

Admission platelet count was inversely correlated with 24-hour mortality and transfusion of PRBCs. A normal platelet count may be insufficient after severe trauma, and as a result, these patients may benefit from a lower platelet transfusion threshold. Future studies of platelet number and function after injury are needed.

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.

Relationship between the hemoglobin level at hospital arrival and post-cardiac arrest neurologic outcome

BACKGROUND

The hemoglobin (Hb) level is an essential determinant of oxygen delivery. The restoration of blood perfusion to vital organs and the capacity for oxygen delivery may be associated with ischemia and reperfusion injuries during cardiac arrest and after cardiac arrest. However, whether the Hb level is associated with neurologic outcome in post-cardiac arrest patients remains unclear.

METHODS

Emergency medical service information and clinical demographics were compiled for witnessed out-of-hospital cardiac arrest patients with coma after the restoration of spontaneous circulation. The study end point was defined as a favorable neurologic outcome at 28 days. We evaluated the relationship between the Hb level at the time of hospital arrival and the neurologic outcome using univariate analyses and a multivariate logistic regression analysis.

RESULTS

There were 137 witnessed cardiac arrest patients: 49 (35.7%) survived and 34 (24.8%) achieved a favorable neurologic outcome. Univariate analyses showed that the favorable outcome group was characterized as having a higher Hb level, a younger age, a higher percentage of male patients, and ventricular fibrillation as the initial cardiac rhythm. In a multivariate analysis adjusting for potential confounding factors, the Hb level at the time of hospital arrival (odds ratio, 1.26; 95% confidence interval, 1.00-1.58) was an independent predictor of a favorable neurologic outcome.

CONCLUSION

A higher Hb level at the time of hospital arrival was associated with a favorable short-term neurologic outcome among post-cardiac arrest patients with a presumed cardiac etiology.

Monitoring of glucose in brain, adipose tissue, and peripheral blood in patients with traumatic brain injury: a microdialysis study

BACKGROUND

Episodes of hyperglycemia are considered to be a secondary insult in traumatically brain-injured patients and have been shown to be associated with impaired outcome. Intensive insulin therapy to maintain a strict glucose level has been suggested to decrease morbidity and mortality in critically ill patients but this aggressive insulin treatment has been challenged. One aspect of strict glucose control is the risk of developing hypoglycemia. Extracellular intracerebral hypoglycemia monitored by intracerebral microdialysis has been shown to correlate with poor outcome. Monitoring of blood glucose during neurointensive care is important because adequate glucose supply from the systemic circulation is crucial to maintain the brain's glucose demand after brain injury. This study investigates the correlation of glucose levels in peripheral blood, subcutaneous (SC) fat, and extracellular intracerebral tissue in patients with severe traumatic brain injury during neurointensive care.

METHODS

In this study, we included 12 patients with severe traumatic brain injury. All patients received one microdialysis catheter each, with a membrane length of 10 mm (CMA 70, CMA Microdialysis AB) in the injured hemisphere of the brain and in the noninjured hemisphere of the brain. An additional microdialysis catheter with a membrane length of 30 mm (CMA 60, CMA Microdialysis AB) was placed in the periumbilical subcutaneous adipose tissue. We studied the correlation among levels of glucose measured in peripheral blood, adipose tissue, and the noninjured hemisphere of the brain during the first 12 hours and during 3 consecutive days in neurointensive care.

RESULTS

We found a significant positive correlation between levels of glucose in peripheral blood, SC fat, and the noninjured brain during the initial 12 hours but not in injured brain. However, the result varied between the patients during the 3-day measurements. In 7 patients, there was a significant positive correlation between glucose in blood and noninjured brain, while in 4 patients this correlation was poor. In 4 patients, there was a significant positive correlation in injured brain and blood. Furthermore, there was a significant correlation between brain and adipose tissue glucose during the 3-day measurements in 11 out of 12 patients.

CONCLUSION

This study indicates that there is a good correlation between blood glucose and adipose tissue during initial and later time points in the neurointensive care unit whereas the correlation between blood and brain seems to be more individualized among patients. This emphasizes the importance of using intracerebral microdialysis to ensure adequate intracerebral levels of glucose in patients suffering from severe traumatic brain injury and to detect hypoglycemia in the brain despite normal levels of blood glucose.

A systematic review of factors contributing to outcomes in patients with traumatic brain injury

AIM AND OBJECTIVE

To review, systematically, factors contributing to outcomes in patients with traumatic brain injury.

BACKGROUND

Traumatic brain injury is a leading cause of death and disability. Several studies have determined the significant predictors of outcomes after traumatic brain injury. The comprehensive identification of these reliable factors for traumatic brain injury is critical to both clinical practice and research.

DESIGN

Systematic literature review.

METHODS

Eligible studies that combined at least two variables to predict outcomes in patient with traumatic brain injury were identified via electronic database searches, footnote chasing and contact with clinical experts. Quality of selected studies was assessed in terms of internal and external validity using 15 questions. Two reviewers independently examined titles, abstracts and whether each met the predefined inclusion criteria.

RESULTS

A total of 46 studies which met review criteria were finally selected. Most studies satisfied internal validity in terms of validity of research variables and multivariate analysis, but few were validated externally. The following factors were significantly associated with unfavourable outcomes: sociodemographic factors such as older age, male gender, lower level of education; clinical factors such as lower Glasgow Coma Scale score, injury caused by motor vehicle crash, hypotension, hypoxia, increased intracranial pressure, no pupil reaction, hypo- or hyperglycaemia, anaemia, coagulopathy, hypo- or hyperthermia, abnormal level of electrolytes, duration of coma; higher level of computed tomography classification by Marshall category; type of intracerebral lesions.

CONCLUSION

Further studies on integrating the sociodemographic factors, the course of the clinical condition and a unified CT scoring system, are recommended for the evaluation and improvement of the prognosis of traumatic brain injury.

RELEVANCE TO CLINICAL PRACTICE

A systematic review of factors contributing to outcome for patients with traumatic brain injury will be invaluable in triage criteria, injury prognostication, care and discharge planning, resource use and patient and family counselling.

Anemia in the setting of traumatic brain injury: the arguments for and against liberal transfusion

Anemia is recognized as a possible cause of secondary injury following traumatic brain injury (TBI). Cogent arguments can be made for both liberal and restrictive blood transfusion practices in this setting. In this narrative review, we summarize available knowledge regarding the risks of anemia and transfusion in patients with TBI. Laboratory studies using animal models and healthy human subjects suggest that anemia below a hemoglobin (Hb) concentration of 7 g/dL results in impaired brain function and below 10 g/dL may be detrimental to recovery from TBI. Clinical studies that have evaluated the association of anemia with clinical outcomes have not consistently demonstrated harm, but they generally have important methodological weaknesses. Alternatively, studies that have analyzed transfusion as a predictor of worse outcome have consistently identified such an association, but these studies may involve residual confounding. What little information exists from randomized trials that have included patients with TBI and evaluated liberal versus restrictive transfusion strategies is inconclusive. Since anemia in the setting of TBI is relatively common and there is considerable variation in transfusion preferences, greater study of this topic - preferably with one or more rigorous, adequately powered, non-inferiority randomized trials - is desirable.

[Coagulation disorders after traumatic brain injury: pathophysiology and therapeutic implications]

Early activation of coagulation is common after traumatic brain injury. Its origin is probably mainly intracerebral, due to tissue factor release from the injured brain. Abnormalities in blood coagulation tests are associated with poor neurological prognosis. Coagulation activation may induce disseminated intravascular coagulation and fibrinolysis. Disseminated intravascular coagulation is linked to brain ischemia caused by intravascular microthrombosis. This review will focus on pathophysiology of coagulation disorders after traumatic brain injury, and on their implications for therapeutic approaches.

Hierarchical log linear analysis of admission blood parameters and clinical outcome following traumatic brain injury

PURPOSE

Numerous statistical methods have been utilised to generate predictive models that identify clinical and biochemical parameters of prognostic value following traumatic brain injury. While these methods provide an accurate statistical description between these variables and outcome, they are difficult to interpret intuitively. Hierarchical log linear analysis can be utilised to present the complex interactions between these variables and outcome visually.

METHODS

We compiled a database of 327 traumatic brain injury patients, their admission blood parameters, clinical admission parameters, and 6-month Glasgow Outcome Score. Seven variables (age, injury severity, Glasgow Coma Score, glucose, albumin, haemoglobin, white cell count) that correlated with outcome in a univariate analysis and two further variables, included on the basis of biological plausibility, (abnormal clotting and magnesium) were used to derive and present a hierarchical log linear model.

RESULTS

Seventeen (out of an original forty-five possible) inter-relationships between the chosen variables were identified as remaining in the hierarchical log linear model. This data is presented pictorially in a hierarchy demonstrating the directness of the statistical association between each of the variables and dichotomised outcome. Four variables within the hierarchical log linear model (age, raised serum glucose, low haemoglobin, Glasgow Coma Score) had a direct independent statistical relationship with outcome. The remaining five variables only had a statistical relationship with outcome via at least one other variable.

CONCLUSIONS

Hierarchical log linear analysis allows the presentation of multivariate, categorical data sets in a pictorial and more easily interpretable fashion.

Early prognosis in traumatic brain injury: from prophecies to predictions

Traumatic brain injury (TBI) is a heterogeneous condition that encompasses a broad spectrum of disorders. Outcome can be highly variable, particularly in more severely injured patients. Despite the association of many variables with outcome, prognostic predictions are notoriously difficult to make. Multivariable analysis has identified age, clinical severity, CT abnormalities, systemic insults (hypoxia and hypotension), and laboratory variables as relevant factors to include in models to predict outcome in individual patients. Advances in statistical modelling and the availability of large datasets have facilitated the development of prognostic models that have greater performance and generalisability. Two prediction models are currently available, both of which have been developed on large datasets with state-of-the-art methods, and offer new opportunities. We see great potential for their use in clinical practice, research, and policy making, as well as for assessment of the quality of health-care delivery. Continued development, refinement, and validation is advocated, together with assessment of the clinical impact of prediction models, including treatment response.

Low hemoglobin is associated with poor functional outcome after non-traumatic, supratentorial intracerebral hemorrhage

Introduction

The impact of anemia on functional outcome and mortality in patients suffering from non-traumatic intracerebral hemorrhage (ICH) has not been investigated. Here, we assessed the relationship between hemoglobin (HB) levels and clinical outcome after ICH.

Methods

One hundred and ninety six patients suffering from supratentorial, non-traumatic ICH were extracted from our local stroke database (June 2004 to June 2006). Clinical and radiologic computed tomography data, HB levels on admission, mean HB values and nadir during hospital stay were recorded. Outcome was assessed at discharge and 3 months using the modified Rankin score (mRS).

Results

Forty six (23.5%) patients achieved a favorable functional outcome (mRS ≤ 3) and 150 (76.5%) had poor outcome (mRS 4 - 6) at discharge. Patients with poor functional outcome had a lower mean HB (12.3 versus 13.7 g/dl, P < 0.001) and nadir HB (11.5 versus 13.0 g/dl, P < 0.001). Ten patients (5.1%) received red blood cell (RBC) transfusions. In a multivariate logistic regression model, the mean HB was an independent predictor for poor functional outcome at three months (odds ratio (OR) 0.73, 95% confidence interval (CI) 0.58-0.92, P = 0.007), along with National Institute of Health Stroke Scale (NIHSS) at admission (OR 1.17, 95% CI 1.11 - 1.24, P < 0.001), and age (OR 1.08, 95% CI 1.04 - 1.12, P < 0.001).

Conclusions

We report an association between low HB and poor outcome in patients with non-traumatic, supratentorial ICH. While a causal relationship could not be proven, previous experimental studies and studies in brain injured patients provide evidence for detrimental effects of anemia on brain metabolism. However, the potential risk of anemia must be balanced against the risk of harm from red blood cell infusion.

Increasing hematocrit above 28% during early resuscitative phase is not associated with decreased mortality following severe traumatic brain injury

BACKGROUND

To prevent iatrogenic damage, transfusions of red blood cells should be avoided. For this, specific and reliable transfusion triggers must be defined. To date, the optimal hematocrit during the initial operating room (OR) phase is still unclear in patients with severe traumatic brain injury (TBI). We hypothesized that hematocrit values exceeding 28%, the local hematocrit target reached by the end of the initial OR phase, resulted in more complications, increased mortality, and impaired recovery compared to patients in whom hematocrit levels did not exceed 28%.

METHODS

Impact of hematocrit (independent variable) reached by the end of the OR phase on mortality and morbidity determined by the extended Glasgow outcome scale (eGOS; dependent variables) was investigated retrospectively in 139 TBI patients. In addition, multiple logistic regression analysis was performed to identify additional important variables.

FINDINGS

Following severe TBI, mortality and morbidity were neither aggravated by hematocrit above 28% reached by the end of the OR phase nor worsened by the required transfusions. Upon multiple logistic regression analysis, eGOS was significantly influenced by the highest intracranial pressure and the lowest cerebral perfusion pressure values during the initial OR phase.

CONCLUSIONS

Based on this retrospective observational analysis, increasing hematocrit above 28% during the initial OR phase following severe TBI was not associated with improved or worsened outcome. This questions the need for aggressive transfusion management. Prospective analysis is required to determine the lowest acceptable hematocrit value during the OR phase which neither increases mortality nor impairs recovery. For this, a larger caseload and early monitoring of cerebral metabolism and oxygenation are indispensable.

IMPACT recommendations for improving the design and analysis of clinical trials in moderate to severe traumatic brain injury

Clinical trials in traumatic brain injury (TBI) pose complex methodological challenges, largely related to the heterogeneity of the population. The International Mission on Prognosis and Clinical Trial Design in TBI study group has explored approaches for dealing with this heterogeneity with the aim to optimize clinical trials in TBI. Extensive prognostic analyses and simulation studies were conducted on individual patient data from eight trials and three observational studies. Here, we integrate the results of these studies into the International Mission on Prognosis and Clinical Trial Design in TBI recommendations for design and analysis of trials in TBI: Details of the major baseline prognostic characteristics should be provided in every report on a TBI study; in trials they should be differentiated per treatment group. We also advocate the reporting of the baseline prognostic risk as determined by validated prognostic models. Inclusion criteria should be as broad as is compatible with the current understanding of the mechanisms of action of the intervention being evaluated. This will maximize recruitment rates and enhance the generalizability of the results. The statistical analysis should incorporate prespecified covariate adjustment to mitigate the effects of the heterogeneity. The statistical analysis should use an ordinal approach, based on either sliding dichotomy or proportional odds methodology. Broad inclusion criteria, prespecified covariate adjustment, and an ordinal analysis will promote an efficient trial, yielding gains in statistical efficiency of more than 40%. This corresponds to being able to detect a 7% treatment effect with the same number of patients needed to demonstrate a 10% difference with an unadjusted analysis based on the dichotomized Glasgow outcome scale.

Classification and prediction of outcome in traumatic brain injury based on computed tomographic imaging

Traumatic brain injury (TBI) is a common and potentially devastating problem. The classification of TBI is necessary for accurate diagnosis and the prediction of outcomes. The increased use of early sedation, intubation and ventilation in more severely injured patients has decreased the value of the Glasgow Coma Scale for the purposes of classification. An alternative is the classification of TBI according to morphological criteria based on computed tomography (CT) investigations. This article reviews the current classification and prediction of outcomes in TBI based on CT imaging. Classifications based on the presence or absence of intracranial local lesions, diffuse injury, signs of subarachnoid or intra-ventricular haemorrhage and fractures or foreign bodies are considered, and their predictive value is discussed. Future studies should address the complicated issue of how optimally to combine CT characteristics for prognostic purposes and how to improve on currently used CT classifications to predict outcomes more accurately.

Year in review 2008: Critical Care--trauma

Eleven papers on trauma published in Critical Care during 2008 addressed traumatic brain injury (TBI), burns, diagnostic concerns and immunosuppression. In regard to TBI, preliminary results indicate the utility of either magnetic resonance imaging (MRI) or ultrasound in measuring optic nerve sheath diameter to identify elevated intracranial pressure (ICP) as well as the potential benefit of thiopental for refractory ICP. Another investigaticc7960on demonstrated that early extubation of TBI patients whose Glasgow Coma Scale score was 8 or less did not result in additional incidence of nosocomial pneumonia. Another study indicated that strict glucose control resulted in worse outcomes during the first week after TBI, but improved outcomes after the second week. Another paper showed the prolonged neuroprotective advantages of proges-terone administration in TBI patients. There was also guidance on improved classifications of renal complications in burn patients. Another study found that patients with inhalation injuries and increased interleukin-6 (IL-6) and IL-10 and decreased IL-7 had increased mortality rates. One literature review described the disadvantages of prolonged immobilization or additional use of MRI for ruling out cervical spine injuries in obtunded TBI patients already cleared by computerized tomography scans. Other investigators found that higher N-terminal pro B-type natriuretic peptide (NT-proBNP) levels may be useful markers for post-traumatic cardiac impairment. Finally, an experimental model showed that both splenic apoptosis and lymphocytopenia may occur shortly after severe hemorrhage, thus increasing the threat of immunosuppression in those with severe blood loss.

The relation between the incidence of hypernatremia and mortality in patients with severe traumatic brain injury

Introduction

The study was aimed at verifying whether the occurrence of hypernatremia during the intensive care unit (ICU) stay increases the risk of death in patients with severe traumatic brain injury (TBI). We performed a retrospective study on a prospectively collected database including all patients consecutively admitted over a 3-year period with a diagnosis of TBI (post-resuscitation Glasgow Coma Score ≤ 8) to a general/neurotrauma ICU of a university hospital, providing critical care services in a catchment area of about 1,200,000 inhabitants.

Methods

Demographic, clinical, and ICU laboratory data were prospectively collected; serum sodium was assessed an average of three times per day. Hypernatremia was defined as two daily values of serum sodium above 145 mmol/l. The major outcome was death in the ICU after 14 days. Cox proportional-hazards regression models were used, with time-dependent variates designed to reflect exposure over time during the ICU stay: hypernatremia, desmopressin acetate (DDAVP) administration as a surrogate marker for the presence of central diabetes insipidus, and urinary output. The same models were adjusted for potential confounding factors.

Results

We included in the study 130 TBI patients (mean age 52 years (standard deviation 23); males 74%; median Glasgow Coma Score 3 (range 3 to 8); mean Simplified Acute Physiology Score II 50 (standard deviation 15)); all were mechanically ventilated; 35 (26.9%) died within 14 days after ICU admission. Hypernatremia was detected in 51.5% of the patients and in 15.9% of the 1,103 patient-day ICU follow-up. In most instances hypernatremia was mild (mean 150 mmol/l, interquartile range 148 to 152). The occurrence of hypernatremia was highest (P = 0.003) in patients with suspected central diabetes insipidus (25/130, 19.2%), a condition that was associated with increased severity of brain injury and ICU mortality. After adjustment for the baseline risk, the incidence of hypernatremia over the course of the ICU stay was significantly related with increased mortality (hazard ratio 3.00 (95% confidence interval: 1.34 to 6.51; P = 0.003)). However, DDAVP use modified this relation (P = 0.06), hypernatremia providing no additional prognostic information in the instances of suspected central diabetes insipidus.

Conclusions

Mild hypernatremia is associated with an increased risk of death in patients with severe TBI. In a proportion of the patients the association between hypernatremia and death is accounted for by the presence of central diabetes insipidus.

Anemia and red blood cell transfusion in neurocritical care

INTRODUCTION

Anemia is one of the most common medical complications to be encountered in critically ill patients. Based on the results of clinical trials, transfusion practices across the world have generally become more restrictive. However, because reduced oxygen delivery contributes to 'secondary' cerebral injury, anemia may not be as well tolerated among neurocritical care patients.

METHODS

The first portion of this paper is a narrative review of the physiologic implications of anemia, hemodilution, and transfusion in the setting of brain-injury and stroke. The second portion is a systematic review to identify studies assessing the association between anemia or the use of red blood cell transfusions and relevant clinical outcomes in various neurocritical care populations.

RESULTS

There have been no randomized controlled trials that have adequately assessed optimal transfusion thresholds specifically among brain-injured patients. The importance of ischemia and the implications of anemia are not necessarily the same for all neurocritical care conditions. Nevertheless, there exists an extensive body of experimental work, as well as human observational and physiologic studies, which have advanced knowledge in this area and provide some guidance to clinicians. Lower hemoglobin concentrations are consistently associated with worse physiologic parameters and clinical outcomes; however, this relationship may not be altered by more aggressive use of red blood cell transfusions.

CONCLUSIONS

Although hemoglobin concentrations as low as 7 g/dl are well tolerated in most critical care patients, such a severe degree of anemia could be harmful in brain-injured patients. Randomized controlled trials of different transfusion thresholds, specifically in neurocritical care settings, are required. The impact of the duration of blood storage on the neurologic implications of transfusion also requires further investigation.

Optimum serum glucose levels for patients with severe traumatic brain injury

Tight glucose control during the acute care of patients with severe traumatic brain injury has recently been advocated based on experimental concerns about deleterious effects of presenting the injured brain with a high glucose load, however, there is little or no clinical evidence that hyperglycemia worsens neurologic injury. The majority of the clinical studies of tight glucose control find that it is associated with an increased risk of hypoglycemic episodes and cellular injury, when compared to conventional glucose control protocols.

Risk index for peri-operative atrial fibrillation in patients undergoing open intracranial neurosurgical procedures

The aim of this prospective study was to determine the prevalence of pre-operative atrial fibrillation and the incidence of postoperative atrial fibrillation in patients undergoing elective or emergency intracranial neurosurgical procedures and the relation to survival and neurological outcome at 6-months follow-up compared to patients with sinus rhythm. A total of 2020 patients were enrolled; 1540 patients underwent elective procedures and 480 underwent emergency procedures. Prevalence of pre-operative atrial fibrillation was 3.7% in elective and 7.2% in emergency procedures (p = 0.0012). In patients undergoing elective cerebral procedures with pre-operative atrial fibrillation, compared to patients with sinus rhythm, 6-month neurological outcome and survival rate are similar. In patients undergoing emergency neurosurgical cerebral procedures, the presence of pre-operative atrial fibrillation is related to an increased risk of poor neurological outcome but with similar survival rate.

New approaches to increase statistical power in TBI trials: insights from the IMPACT study

INTRODUCTION

None of the multi-centre phase III randomized controlled trials (RCTs) performed in TBI have convincingly demonstrated efficacy. Problems in clinical trial design and analysis may have contributed to these failures. Clinical trials in the TBI population pose several complicated methodological challenges, related especially to the heterogeneity of the population. In this paper we examine the issue of heterogeneity within the IMPACT (International Mission on Prognosis and Clinical Trial design in TBI) database and investigate the application of conventional and innovative methods for the statistical analysis of trials in TBI.

METHODS AND RESULTS

Simulation studies in the IMPACT database (N = 9205) showed substantial gains in efficiency with covariate adjustment. Adjusting for 7 important predictors yielded up to a 28% potential reduction in trial size. Ongoing analyses on the potential benefit of ordinal analysis, such as proportional odds and sliding dichotomy, gave promising results with even larger potential reductions in trial size.

CONCLUSION

The statistical power of RCTs in TBI can be considerably increased by applying covariate adjustment and by ordinal analysis methods of the GOS. These methods need to be considered for optimizing future TBI trials.

Classification of traumatic brain injury for targeted therapies

The heterogeneity of traumatic brain injury (TBI) is considered one of the most significant barriers to finding effective therapeutic interventions. In October, 2007, the National Institute of Neurological Disorders and Stroke, with support from the Brain Injury Association of America, the Defense and Veterans Brain Injury Center, and the National Institute of Disability and Rehabilitation Research, convened a workshop to outline the steps needed to develop a reliable, efficient and valid classification system for TBI that could be used to link specific patterns of brain and neurovascular injury with appropriate therapeutic interventions. Currently, the Glasgow Coma Scale (GCS) is the primary selection criterion for inclusion in most TBI clinical trials. While the GCS is extremely useful in the clinical management and prognosis of TBI, it does not provide specific information about the pathophysiologic mechanisms which are responsible for neurological deficits and targeted by interventions. On the premise that brain injuries with similar pathoanatomic features are likely to share common pathophysiologic mechanisms, participants proposed that a new, multidimensional classification system should be developed for TBI clinical trials. It was agreed that preclinical models were vital in establishing pathophysiologic mechanisms relevant to specific pathoanatomic types of TBI and verifying that a given therapeutic approach improves outcome in these targeted TBI types. In a clinical trial, patients with the targeted pathoanatomic injury type would be selected using an initial diagnostic entry criterion, including their severity of injury. Coexisting brain injury types would be identified and multivariate prognostic modeling used for refinement of inclusion/exclusion criteria and patient stratification. Outcome assessment would utilize endpoints relevant to the targeted injury type. Advantages and disadvantages of currently available diagnostic, monitoring, and assessment tools were discussed. Recommendations were made for enhancing the utility of available or emerging tools in order to facilitate implementation of a pathoanatomic classification approach for clinical trials.

Predicting outcome after traumatic brain injury: development and international validation of prognostic scores based on admission characteristics

BACKGROUND

Traumatic brain injury (TBI) is a leading cause of death and disability. A reliable prediction of outcome on admission is of great clinical relevance. We aimed to develop prognostic models with readily available traditional and novel predictors.

METHODS AND FINDINGS

Prospectively collected individual patient data were analyzed from 11 studies. We considered predictors available at admission in logistic regression models to predict mortality and unfavorable outcome according to the Glasgow Outcome Scale at 6 mo after injury. Prognostic models were developed in 8,509 patients with severe or moderate TBI, with cross-validation by omission of each of the 11 studies in turn. External validation was on 6,681 patients from the recent Medical Research Council Corticosteroid Randomisation after Significant Head Injury (MRC CRASH) trial. We found that the strongest predictors of outcome were age, motor score, pupillary reactivity, and CT characteristics, including the presence of traumatic subarachnoid hemorrhage. A prognostic model that combined age, motor score, and pupillary reactivity had an area under the receiver operating characteristic curve (AUC) between 0.66 and 0.84 at cross-validation. This performance could be improved (AUC increased by approximately 0.05) by considering CT characteristics, secondary insults (hypotension and hypoxia), and laboratory parameters (glucose and hemoglobin). External validation confirmed that the discriminative ability of the model was adequate (AUC 0.80). Outcomes were systematically worse than predicted, but less so in 1,588 patients who were from high-income countries in the CRASH trial.

CONCLUSIONS

Prognostic models using baseline characteristics provide adequate discrimination between patients with good and poor 6 mo outcomes after TBI, especially if CT and laboratory findings are considered in addition to traditional predictors. The model predictions may support clinical practice and research, including the design and analysis of randomized controlled trials.

Differential temporal profile of lowered blood glucose levels (3.5 to 6.5 mmol/l versus 5 to 8 mmol/l) in patients with severe traumatic brain injury

INTRODUCTION

Hyperglycaemia is detrimental, but maintaining low blood glucose levels within tight limits is controversial in patients with severe traumatic brain injury, because decreased blood glucose levels can induce and aggravate underlying brain injury.

METHODS

In 228 propensity matched patients (age, sex and injury severity) treated in our intensive care unit (ICU) from 2000 to 2004, we retrospectively evaluated the influence of different predefined blood glucose targets (3.5 to 6.5 versus 5 to 8 mmol/l) on frequency of hypoglycaemic and hyperglycaemic episodes, insulin and norepinephrine requirement, changes in intracranial pressure and cerebral perfusion pressure, mortality and length of stay on the ICU.

RESULTS

Mortality and length of ICU stay were similar in both blood glucose target groups. Blood glucose values below and above the predefined levels were significantly increased in the 3.5 to 6.5 mmol/l group, predominantly during the first week. Insulin and norepinephrine requirements were markedly increased in this group. During the second week, the incidences of intracranial pressure exceeding 20 mmHg and infectious complications were significantly decreased in the 3.5 to 6.5 mmol/l group.

CONCLUSION

Maintaining blood glucose within 5 to 8 mmol/l appears to yield greater benefit during the first week. During the second week, 3.5 to 6.5 mmol/l is associated with beneficial effects in terms of reduced intracranial hypertension and decreased rate of pneumonia, bacteraemia and urinary tract infections. It remains to be determined whether patients might profit from temporally adapted blood glucose limits, inducing lower values during the second week, and whether concomitant glucose infusion to prevent hypoglycaemia is safe in patients with post-traumatic oedema.

Multivariable Prognostic Analysis in Traumatic Brain Injury: Results from The IMPACT Study

We studied the prognostic value of a wide range of conventional and novel prognostic factors on admission after traumatic brain injury (TBI) using both univariate and multivariable analysis. The outcome measure was Glasgow Outcome Scale at 6 months after injury. Individual patient data were available on a cohort of 8686 patients drawn from eight randomized controlled trials and three observational studies. The most powerful independent prognostic variables were age, Glasgow Coma Scale (GCS) motor score, pupil response, and computerized tomography (CT) characteristics, including the Marshall CT classification and traumatic subarachnoid hemorrhage. Prothrombin time was also identified as a powerful independent prognostic factor, but it was only available for a limited number of patients coming from three of the relevant studies. Other important prognostic factors included hypotension, hypoxia, the eye and verbal components of the GCS, glucose, platelets, and hemoglobin. These results on prognostic factors will underpin future work on the IMPACT project, which is focused on the development of novel approaches to the design and analysis of clinical trials in TBI. In addition, the results provide pointers to future research, including further analysis of the prognostic value of prothrombin time, and the evaluation of the clinical impact of intervening aggressively to correct abnormalities in hemoglobin, glucose, and coagulation.