Committee on Surgical Combat Casualty Care Position Statement: Neurosurgical Capability for the Optimal Management of Traumatic Brain injury During Deployed Operations. Including Invited Commentaries

BACKGROUND

Experiences over the last 3 decades of war have demonstrated a high incidence of Traumatic Brain Injury (TBI) resulting in a persistent need for a neurosurgical capability within the deployed theatre of operations. Despite this, no doctrinal requirement for a deployed neurosurgical capability exists. Through an iterative process, the Joint Trauma System Committee on Surgical Combat Casualty Care (CoSCCC) developed a Position Statement to inform medical and non-medical military leaders about the risks of the lack of a specialized neurosurgical capability.

METHODS

The need for deployed neurosurgical capability Position Statement was identified during the spring 2021 CoSCCC meeting. A tri-service working group of experienced forward-deployed caregivers developed a preliminary statement. An extensive iterative review process was then conducted to ensure that the intended messaging was clear to senior medical leaders and operational commanders. To provide additional context and a civilian perspective, statement commentaries were solicited from civilian clinical experts including a recently retired military trauma surgeon boarded in Neurocritical Care, a trauma surgeon instrumental in developing the Brain Injury Guidelines (BIG), a practicing neurosurgeon with world-renowned expertise in TBI, and the Chair of the Committee on Trauma (COT).

RESULTS

After multiple revisions, Position Statement was finalized it was approved by the CoSCCC membership in February 2023. Challenges identified include: 1) military neurosurgeon attrition; 2) the lack of a doctrinal neurosurgical capabilities requirement during deployed combat operations; 3) the need for neurosurgical telemedicine capability and in-theatre CT scans to triage TBI casualties requiring neurosurgical care.

CONCLUSION

Challenges identified regarding neurosurgical capabilities within the deployed trauma system include military neurosurgeon attrition and the lack of a doctrinal requirement for neurosurgical capability during deployed combat operations. To mitigate risk to the force in a future peer-peer conflict several evidence-based recommendations are made. The solicited civilian commentaries strengthen these recommendations by putting them into the context of civilian TBI management. These neurosurgical capabilities position statement is intended to be a forcing function and a communication tool to inform operational commanders and military medical leaders on the use of these teams on current and future battlefields.

LEVEL OF EVIDENCE

Brief Report, 3.

Military Traumatic Brain Injury: The History, Impact, and Future

This review examines how lessons learned from United States military conflicts, beginning with the United States Civil War through the engagements in Iraq and Afghanistan, have shaped current traumatic brain injury (TBI) care in the United States military, influenced congressional mandates and directives, and led to best practices in caring for the warfighter. Prior to the most recent war, emphasis was placed on improving the surgical and medical care of service members (SM) with severe and especially penetrating brain injuries. However, during the Iraq and Afghanistan conflicts, also known as the Global War on Terrorism (GWOT), blast injury from improvised explosive devices most often caused mild TBI (mTBI), an injury that was not always recognized and was labelled the "signature wound" of the GWOT. This has led to extensive research on objective diagnostic technologies for mTBI, the association of mTBI with post-traumatic stress disorder (PTSD), and the long term consequences of mTBI. Here we summarize the key findings and most important advances from those efforts, and discuss the way forward regarding future military conflicts.

The Prehospital Evaluation and Care of Moderate/Severe TBI in the Austere Environment

Increased resource constraints secondary to a smaller medical footprint, prolonged evacuation times, or overwhelming casualty volumes all increase the challenges of effective management of traumatic brain injury (TBI) in the austere environment. Prehospital providers are responsible for the battlefield recognition and initial management of TBI. As such, targeted education is critical to efficient injury recognition, promoting both provider readiness and improved patient outcomes. When austere conditions limit or prevent definitive treatment, a comprehensive understanding of TBI pathophysiology can help inform acute care and enhance prevention of secondary brain injury. Field deployable, noninvasive TBI assessment and monitoring devices are urgently needed and are currently undergoing clinical evaluation. Evidence shows that the assessment, monitoring, and treatment in the first few hours and days after injury should focus on the preservation of cerebral perfusion and oxygenation. For cases where medical management is inadequate (eg, evidence of an enlarging intracranial hematoma), guidelines have been developed for the performance of cranial surgery by nonneurosurgeons. TBI management in the austere environment will continue to be a challenge, but research focused on improving evidence-based monitoring and therapeutic interventions can help to mitigate some of these challenges and improve patient outcomes.

Association of time to craniectomy with survival in patients with severe combat-related brain injury

OBJECTIVEIn combat and austere environments, evacuation to a location with neurosurgery capability is challenging. A planning target in terms of time to neurosurgery is paramount to inform prepositioning of neurosurgical and transport resources to support a population at risk. This study sought to examine the association of wait time to craniectomy with mortality in patients with severe combat-related brain injury who received decompressive craniectomy.METHODSPatients with combat-related brain injury sustained between 2005 and 2015 who underwent craniectomy at deployed surgical facilities were identified from the Department of Defense Trauma Registry and Joint Trauma System Role 2 Registry. Eligible patients survived transport to a hospital capable of diagnosing the need for craniectomy and performing surgery. Statistical analyses included unadjusted comparisons of postoperative mortality by elapsed time from injury to start of craniectomy, and Cox proportional hazards modeling adjusting for potential confounders. Time from injury to craniectomy was divided into quintiles, and explored in Cox models as a binary variable comparing early versus delayed craniectomy with cutoffs determined by the maximum value of each quintile (quintile 1 vs 2-5, quintiles 1-2 vs 3-5, etc.). Covariates included location of the facility at which the craniectomy was performed (limited-resource role 2 facility vs neurosurgically capable role 3 facility), use of head CT scan, US military status, age, head Abbreviated Injury Scale score, Injury Severity Score, and injury year. To reduce immortal time bias, time from injury to hospital arrival was included as a covariate, entry into the survival analysis cohort was defined as hospital arrival time, and early versus delayed craniectomy was modeled as a time-dependent covariate. Follow-up for survival ended at death, hospital discharge, or hospital day 16, whichever occurred first.RESULTSOf 486 patients identified as having undergone craniectomy, 213 (44%) had complete date/time values. Unadjusted postoperative mortality was 23% for quintile 1 (n = 43, time from injury to start of craniectomy 30-152 minutes); 7% for quintile 2 (n = 42, 154-210 minutes); 7% for quintile 3 (n = 43, 212-320 minutes); 19% for quintile 4 (n = 42, 325-639 minutes); and 14% for quintile 5 (n = 43, 665-3885 minutes). In Cox models adjusted for potential confounders and immortal time bias, postoperative mortality was significantly lower when time to craniectomy was within 5.33 hours of injury (quintiles 1-3) relative to longer delays (quintiles 4-5), with an adjusted hazard ratio of 0.28, 95% CI 0.10-0.76 (p = 0.012).CONCLUSIONSPostoperative mortality was significantly lower when craniectomy was initiated within 5.33 hours of injury. Further research to optimize craniectomy timing and mitigate delays is needed. Functional outcomes should also be evaluated.

MRI in Management of Mild TBI/Concussion in the Deployed Setting

Magnetic resonance imaging (MRI) has specific limitations in theater and has unique requirements for its safe use with patients which require additional technician training and strict adherence to MRI-specific safety protocols. Neuroimaging is recommended for the evaluation of service members with clinical red flags new onset or persistent or worsening symptoms, and individuals whose recovery is not progressing as anticipated. This article is a brief discussion of when MRI is appropriate.

Revisiting therapeutic hypothermia for severe traumatic brain injury... again

Improved understanding of the molecular mechanisms of secondary brain injury has informed the optimum depth and duration of cooling and led to increased clinical interest in the therapeutic moderate hypothermia for severe traumatic brain injury over the past two decades. Although several large multi-center clinical trials have not found a treatment effect, multiple single-center trials have, and a recent meta-analysis by Crossley and colleagues now finds that the cumulative findings of those single-center trials dilute the multi-center trial results and show an overall reduction in mortality and poor outcomes associated with cooling. The need for consistent support of key physiologic parameters during cooling is emphasized by this finding.

Current recommendations for the diagnosis and treatment of concussion in sport: a comparison of three new guidelines

Currently, there is considerable debate within the sports medicine community about the role of concussion and the risk of chronic neurological sequelae. This concern has led to significant confusion among primary care providers and athletic trainers about how to best identify those athletes at risk and how to treat those with concussion. During the first quarter of 2013, several new or updated clinical practice guidelines and position statements were published on the diagnosis, treatment, and management of mild traumatic brain injury/concussion in sports. Three of these guidelines were produced by the American Medical Society for Sports Medicine, The American Academy of Neurology, and the Zurich Consensus working group. The goal of each group was to clearly define current best practices for the definition, diagnosis, and acute and post-acute management of sports-related concussion, including specific recommendations for return to play. In this article, we compare the recommendations of each of the three groups, and highlight those topics for which there is consensus regarding the definition of concussion, diagnosis, and acute care of athletes suspected of having a concussion, as well as return-to-play recommendations.

Effects of non-neurological complications on traumatic brain injury outcome

Traumatic brain injury (TBI) affects over 1.5 million Americans annually and consumes a significant amount of healthcare dollars. Identification of complications and factors that impact recovery from TBI is important in improving outcome and allocating appropriate resources. Understanding the role of non-neurologic complications such as sepsis, acute kidney injury, and respiratory problems on TBI outcome and mortality is critical.

Combat-related traumatic brain injury and its implications to military healthcare

Traumatic brain injury (TBI) is a known injury in today's combat arena. Improved screening and surveillance methods have diagnosed TBI with increasing frequency. Current treatment plans are based largely on information gleaned from sports injuries. However, these management paradigms fail to address the effect of physiologic stress (fatigue, dehydration) and psychological stress at the time of injury as well as the number of previous concussions that may affect recovery from combat-related TBI. This article presents current evaluation and management of combat-related injury and discusses other psychological conditions that may coexist with TBI.

Coma due to cardiac arrest: prognosis and contemporary treatment

Approximately 80% of patients who are successfully resuscitated from cardiac arrest do not regain consciousness immediately after return of spontaneous circulation, and may remain in a coma for hours or weeks, or even be in a persistent vegetative state. Recent investigations have focused on the identification of early clinical characteristics and biomarkers that can reliably predict emergence from coma in those who survive, and on therapies that might improve neurologic outcome from the ischemic brain injury that can be caused by cardiac arrest.

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.

Traumatic brain injury research priorities: the Conemaugh International Brain Injury Symposium

In 2005, an international symposium was convened with over 100 neuroscientists from 13 countries and major research centers to review current research in traumatic brain injury (TBI) and develop a consensus document on research issues and priorities. Four levels of TBI research were the focus of the discussion: basic science, acute care, post-acute neurorehabilitation, and improving quality of life (QOL). Each working group or committee was charged with reviewing current research, discussion and prioritizing future research directions, identifying critical issues that impede research in brain injury, and establishing a research agenda that will drive research over the next five years, leading to significantly improved outcomes and QOL for individuals suffering brain injuries. This symposium was organized at the request of the Congressional Brain Injury Task Force, to follow up on the National Institutes of Health Consensus Conference on TBI as mandated by the TBI ACT of 1996. The goal was to review what progress had been made since the National Institutes of Health (NIH) Consensus Conference, and also to follow up on the 1990's Decade of the Brain Project. The major purpose of the symposium was to provide recommendations to the U.S. Congress on a priority basis for research, treatment, and training in TBI over the next five years.

Sex and genetic associations with cerebrospinal fluid dopamine and metabolite production after severe traumatic brain injury

Object

Dopamine (DA) pathways have been implicated in cognitive deficits after traumatic brain injury (TBI). Both sex and the dopamine transporter (DAT) 3′ variable number of tandem repeat polymorphism have been associated with differences in DAT protein density, and DAT protein affects both presynaptic DA release, through reverse transport, and DA reuptake. Catecholamines and associated metabolites are subject to autooxidation, resulting in the formation of reactive oxygen species that may contribute to subsequent oxidative injury. The purpose of this study was to determine associations between factors that affect DAT expression and cerebrospinal fluid (CSF) DA and metabolite levels after severe TBI.

Methods

Sixty-three patients with severe TBI (Glasgow Coma Scale score ≤ 8) were evaluated. The patients' genotypes were obtained using previously banked samples of CSF, and serial CSF samples (416 samples) were used to evaluate DA and metabolite levels. High-performance liquid chromatography was used to determine CSF levels of DA, 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) during the first 5 days after injury.

Mixed-effects multivariate regression modeling revealed that patients with the DAT 10/10 genotype had higher CSF DA levels than patients with either the DAT 9/9 or DAT 9/10 genotypes (p = 0.009). Females with the DAT 10/10 genotype had higher CSF DA levels than females with the DAT 9/9 or DAT 9/10 genotypes, and sex was associated with higher DOPAC levels (p = 0.004). Inotrope administration also contributed to higher DA levels (p = 0.002).

Conclusions

In addition to systemic administration of DA, inherent factors such as sex and DAT genotype affect post-TBI CSF DA and DA metabolite levels, a phenomenon that may modulate susceptibility to DA-mediated oxidative injury.

Proteolysis consistent with activation of caspase-7 after severe traumatic brain injury in humans

The expression and proteolysis of caspase family proteins are involved in the initiation and execution of apoptosis, which has been reported to occur in human and experimental traumatic brain injury (TBI). Caspase-3, -6, and -7 belong to the group of executioner caspases, which are cleaved and activated at the late, irreversible stage of apoptosis. Our previous studies demonstrated roles for caspase-1, -3, and -8 in humans after severe TBI. Here we report expression of caspase-7 mRNA and protein in humans after TBI (n = 16) and control brain-bank tissue (n = 6). Semiquantitative reverse transcription polymerase chain reaction showed no differences between caspase-7 mRNA in TBI patients versus controls (73 +/- 24 vs. 85 +/- 56 relative optical density [ROD], respectively). In contrast, Western blot analysis showed increased pro-caspase-7 in TBI patients versus controls (214 +/- 30 vs. 1 +/- 1 ROD, respectively), as well as an increase in the approximately 20 kD proteolytic fragment in TBI patients versus controls (86 +/- 13 vs. 22 +/- 12 ROD, respectively), consistent with activation of caspase-7 after TBI in humans. Immunohistochemical analysis showed that cells expressing caspase-7 included astrocytes and neurons and possibly other glial cell types and infiltrated inflammatory cells. These data show that caspase-7 and its cleavage product are increased in human brain after TBI in many central nervous system, as well as noncentral nervous system, cell types. Thus, caspase-7 may play a role in the glial and inflammatory responses, and possibly neuronal death, after TBI in humans.

Increased phosphorylation of protein kinase B and related substrates after traumatic brain injury in humans and rats

Activation of protein kinase B (PKB, also known as Akt) by phosphorylation at serine-473 and threonine-308 promotes cell survival in multiple in vitro and in vivo models where neuronal death is seen, including traumatic brain injury (TBI); however, whether PKB is activated in humans after TBI was heretofore unknown. Activated PKB inhibits apoptogenic factors and is involved in the regulation of several transcription factors. Accordingly, we examined phosphorylation of the PKB signaling pathway in humans as well as rats after TBI using phosphospecific antibodies. Increased phosphorylation of PKB and PKB substrates was detected in injured brain from both humans and rats. In humans, increased phosphorylation of the PKB signaling pathway-related proteins Bad and forkhead transcription factor (FKHR) was detected in patients with TBI versus controls. In rats, increased phosphorylation of FKHR, inhibitor of kappaBalpha, and cyclic adenosine monophosphate responsive element binding protein (CREB) was detected after TBI versus controls. The deoxyribonucleic acid-binding activity of CREB was also enhanced after TBI in rats. Increased phosphorylation of PKB and PKB substrates was identified in neurons and other cell types by immunohistochemistry in both humans and rats. These data show increased phosphorylation of PKB, PKB substrates, and related proteins after both experimental and clinical TBI, suggesting either activation of the PKB signaling pathway or reduced phosphatase activity in both species.

Evidenced-based guidelines for traumatic brain injuries

An enormous amount of clinical and basic science brain injury research has been undertaken during the last several decades in an effort to improve outcomes following severe traumatic brain injury, but to date there still are no new therapies that have been clearly shown to be beneficial. There is, however, increasing evidence to suggest that evidence-based, protocol-driven, acute care can lead to improved outcomes. Evidence based guidelines for the medical and surgical management of severe brain injury, and for penetrating and pediatric brain injury, as well as for the pre-hospital management of brain injury, have all been published. In this chapter the conclusions of those guidelines is reviewed. In addition, the studies that demonstrate improved outcomes as a result of implementation of the guidelines are summarized.

Early Glasgow Outcome Scale Scores Predict Long-Term Functional Outcome in Patients with Severe Traumatic Brain Injury

Patients sustaining severe traumatic brain injury (TBI) have variable long-term outcomes. We examined the association between Glasgow Outcome Scale (GOS) assessed at 3 months and long-term outcomes at 12 months after TBI. We studied 159 patients with severe, closed traumatic brain injuries (Glasgow Coma Scale [GCS] <or= 8) who were treated at an academic medical center and survived for a minimum of 3 months after TBI. Demographics and admission clinical data and GOS at 3 and 12 months were analyzed. Multivariate logistic regression was used to asses the relationship between 3-month GOS, demographics, and clinical data and a poor outcome, defined as GOS 1-3 assessed at 12 months after injury. The patient population was predominantly male (77%), with a median age of 30 years and a median admission GCS of 6. The logistic regression model showed that the GOS at 3 months was the best predictor of 12-month outcomes (odds ratio = 15.22, p < 0.001). The presence of prolonged hypotension, diffuse axonal injury (DAI), and fixed and dilated pupils on admission were also significant independent predictors of poor 12-month outcome (for all, p <or= 0.047). The adjusted logistic model showed a steep gradient of long-term recovery potential depending upon GOS at 3 months, ranging from an 89.4% chance of poor outcome for patients with a GOS of 2, to a 0.11% chance of poor outcome for those with a GOS of 5. The 3-month GOS is a powerful independent predictor of long-term outcome for patients with severe TBI. Prolonged hypotension, DAI, and the presence of fixed and dilated pupils were also independent predictors of poor outcome.

Gender associations with cerebrospinal fluid glutamate and lactate/pyruvate levels after severe traumatic brain injury

OBJECTIVE

Female sex hormones appear to be neuroprotective after traumatic brain injury by attenuating multiple mechanisms of secondary insult, including excitotoxicity and ischemia. The purpose of this study was to evaluate associations between gender and cerebrospinal fluid glutamate and lactate/pyruvate production and the role of hypothermia with gender in attenuating these markers.

DESIGN

Prospectively collected data were analyzed for adult patients with severe traumatic brain injury. Gender comparisons for cerebrospinal fluid glutamate and lactate/pyruvate production were determined using ventricular samples obtained over the first 48 hrs postinjury.

SETTING

University-based level I trauma center.

PATIENTS

There were 123 patients, male n = 93 and female n = 30 (n = 686 cerebrospinal fluid samples), with severe traumatic brain injury (Glasgow Coma Scale score < or =8).

INTERVENTIONS

A portion of these patients were part of a randomized controlled trial evaluating the effect of (48 hrs) therapeutic hypothermia after severe traumatic brain injury. The remainder received hypothermia (24 hrs) if they met clinical care criteria. Patients were cooled to 32-33 degrees C (within approximately 8 hrs) for either 24 or 48 hrs and then were rewarmed or remained normothermic.

MEASUREMENTS AND MAIN RESULTS

Regression analyses using generalized estimating equations for repeated measures showed significant increases in cerebrospinal fluid glutamate production for males compared with females (p = .0023) and a significant interaction between glutamate concentration, gender, and time (p = .0035) by 24 hrs postinjury. Females had lower lactate/pyruvate ratios than males (p = .0006), and there was a significant interaction between lactate/pyruvate, gender, and time (p = .0045) throughout the first 48 hrs postinjury. Hypothermia attenuated glutamate levels, particularly for males, over the time course studied.

CONCLUSIONS

These data suggest significant gender differences with glutamate and lactate/pyruvate production after severe traumatic brain injury. Gender- and hormone-mediated differences in central nervous system pathophysiology should be considered with clinical trials in traumatic brain injury.

Alzheimer's pathology in human temporal cortex surgically excised after severe brain injury

Traumatic brain injury (TBI) is a risk factor for the development of Alzheimer's disease (AD). This immunohistochemical study determined the extent of AD-related changes in temporal cortex resected from individuals treated surgically for severe TBI. Antisera generated against Abeta species (total Abeta, Abeta(1-42), and Abeta(1-40)), the C-terminal of the Abeta precursor protein (APP), apolipoprotein E (apoE), and markers of neuron structure and degeneration (tau, ubiquitin, alpha-, beta-, and gamma-synuclein) were used to examine the extent of Abeta plaque deposition and neurodegenerative changes in 18 TBI subjects (ages 18-64 years). Diffuse cortical Abeta deposits were observed in one third of subjects (aged 35-62 years) as early as 2 h after injury, with only one (35-year old) individual exhibiting "mature", dense-cored plaques. Plaque-like deposits, neurons, glia, and axonal changes were also immunostained with APP and apoE antibodies. In plaque-positive cases, the only statistically significant change in cellular immunostaining was increased neuronal APP (P = 0.013). There was no significant correlation between the distribution of Abeta plaques and markers of neuronal degeneration. Diffuse tau immunostaining was localized to neuronal cell soma, axons or glial cells in a larger subset of individuals. Tau-positive, neurofibrillary tangle (NFT)-like changes were detected in only two subjects, both of more advanced age and who were without Abeta deposits. Other neurodegenerative changes, evidenced by ubiquitin- and synuclein-immunoreactive neurons, were abundant in the majority of cases. Our results demonstrate a differential distribution and course of intra- and extra-cellular AD-like changes during the acute phase following severe TBI in humans. Abeta plaques and early evidence of neuronal degenerative changes can develop rapidly after TBI, while fully developed NFTs most likely result from more chronic disease- or injury-related processes. These observations lend further support to the hypothesis that head trauma significantly increases the risk of developing pathological and clinical symptoms of AD, and provide insight into the molecular mechanisms that initiate these pathological cascades very early during severe brain injury.

The Effects of Admission Alcohol Level on Cerebral Blood Flow and Outcomes after Severe Traumatic Brain Injury

This study examined the relationship between admission serum alcohol level (ETOH) and cerebral blood flow (CBF) and outcomes in the adult traumatic brain injured (TBI) population. We hypothesized that individuals with ETOH > 100 mg/dL will have decreased blood flow on admission and poorer outcomes. Eighty subjects, age 16-65, with severe TBI (Glasgow Coma Score [GCS] </= 8) were entered into the study. Correlational analysis assessed the relationship between ETOH and admission severity of injury scores as measured by Marshall and APACHE III scores, CBF, and outcomes. Comparison of CBF and outcomes between groups based on admission serum ETOH level was conducted with analysis of variance and post hoc Scheffé analyses as well as regression analysis. There was a significant relationship between serum ETOH level and GCS (p = 0.02), but not APACHE III scores (p = 0.12) or Marshall scores (p = 0.27). There was a significant correlation between global CBF and serum ETOH level (p = 0.02). There was no statistically significant association between serum ETOH level and GOS at 3 (p = 0.97), 6 (p= 0.56), or 12 (p = 0.73) months after injury. The data indicated that serum ETOH levels > 100 mg/dL at the time of admission after a TBI were associated with a decrease in global CBF. Elevated serum ETOH level at time of injury did not, however, impact outcomes.

Controlled normothermia in neurologic intensive care

Preclinical studies of cerebral ischemia and trauma find increased brain tissue injury and worsened functional outcomes if the brain temperature exceeds 39 degrees C. Several retrospective studies of patients with new-onset stroke, intracerebral hemorrhage, or subarachnoid hemorrhage support these observations. However, fever is very common among these patients early after the onset of their disease, particularly if they are in the ICU for a week or more, and brain temperatures are likely to be as much as 2 degrees C higher than rectal temperatures. Finally, intravascular temperature modulation has been shown to be more effective for preventing fever than conventional methods, such as antipyretic medications or surface-cooling techniques. Further study is needed to establish if such better control of temperature will lead to improved outcomes.

Marked Gender Effect on Lipid Peroxidation after Severe Traumatic Brain Injury in Adult Patients

Striking gender differences have been reported in the pathophysiology and outcome of acute neurological injury. Greater neuroprotection in females versus males may be due, in part, to direct and indirect sex hormone-mediated antioxidant mechanisms. Progesterone administration decreases brain levels of F(2)-isoprostane, a marker of lipid peroxidation, after experimental traumatic brain injury (TBI) in male rats, and estrogen is neuroprotective in experimental neurological injury. In this study, we evaluated the effect of gender on lipid peroxidation, as assessed by cerebrospinal fluid (CSF) levels of F(2)-isoprostane, after severe TBI in humans. Lipid peroxidation was assessed in CSF from 68 adults enrolled in two randomized controlled trials evaluating the effect of therapeutic hypothermia after severe TBI (Glasgow coma scale [GCS] score </= 8). Patients treated with hypothermia (n = 41, 12 females, 29 males) were cooled to 32-33 degrees C (within approximately 6 h) for either 24 or 48 h and then re-warmed. F(2)-isoprostane levels were assessed by ELISA in ventricular CSF samples (n = 199) on day 1, 2, and 3. The association between age, GCS score, time, gender, treatment, duration of treatment, core temperature at the time of CSF sampling, secondary hypoxemia, and CSF F(2)-isoprostane level was assessed by multivariate and dichotomous analyses. F(2)-isoprostane was approximately 2-fold higher in males than females (145.8 +/- 39.6 versus 75.4 +/- 16.6 pg/mL, day 1 p = 0.018). An effect of time after injury (p = 0.007) was reflected by a marked early peak in F(2)-isoprostane (day 1). CSF F(2)-isoprostane was also associated with hypoxemia (p = 0.04). Hypothermia tended to decrease F(2)-isoprostane levels only in males on d1 after TBI. To our knowledge, this is the first study showing gender differences in lipid peroxidation after clinical TBI. Lipid peroxidation occurs early after severe TBI in adults and is more prominent in males vs females. These results established that gender is an important consideration in clinical trial design, particularly in the case of antioxidant strategies.

Relationship between apoE4 allele and excitatory amino acid levels after traumatic brain injury

OBJECTIVE

Apolipoprotein E isoform (E4) has been posited to affect outcomes after central nervous system injury. This project sought to determine the relationship between the apoE4 allele and the recovery of amino acid neurotransmitters (aspartate, glutamate, and lactate/pyruvate ratio [L/P]) following a traumatic brain injury (TBI) after controlling for patient characteristics.

DESIGN

This prospective clinical study examined neurotransmitters and L/P within the cerebrospinal fluid and compared the trends by apoE genotypes.

SETTING

Adults with TBI were recruited from a neurotrauma intensive care unit within a trauma I university medical center.

PATIENTS

Ninety-one patients were enrolled into the study after a severe TBI (Glasgow Coma Scale [GCS] score, </=8). Cerebrospinal fluid was serially sampled from a ventriculostomy every 4 hrs for the first 24 hrs and every 6 hrs for 25-120 hrs after injury.

MEASUREMENTS AND MAIN RESULTS

Hierarchical linear modeling analyses were used to compare the change of glutamate, aspartate, and L/P over time by the presence or absence of the apoE4 allele, with GCS score, sex, race, and therapeutic hypothermias included as covariates. There was a significant apoE4 allele group effect on both the linear and quadratic slopes in aspartate. In glutamate, the rate of change in glutamate was statistically related to GCS score. There was no significant difference in the glutamate response over time by the presence of the apoE4 allele. There was a significant difference in the change in L/P across time, with faster recovery when the apoE4 allele was absent.

CONCLUSIONS

Recovery of aspartate and L/P differed depending on the presence of the apoE4 allele. Patients with the allele had significant increased and sustained levels of aspartate and L/P after TBI. Changes in glutamate were related to severity of illness and were independent of the presence of the apoE4 allele.

Acute etomidate treatment reduces cognitive deficits and histopathology in rats with traumatic brain injury

OBJECTIVE

To test the hypothesis that etomidate treatment improves functional, cognitive, and histologic outcome after experimental traumatic brain injury.

DESIGN

Controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Traumatic brain injury was produced by controlled cortical impact injury (4 m/sec, 2.6 mm of tissue deformation). Etomidate (2 mg/kg) was administered intravenously immediately before injury (n = 13) or 5 mins after injury (n = 12). Additional rats received saline treatment 5 mins after injury (n = 12) or served as sham controls (n = 10).

MEASUREMENTS AND MAIN RESULTS

Rats were evaluated on beam balance and beam walk tasks on postoperative days 1-5 and then trained in the Morris water maze on postoperative days 14-18. On day 28, the rats were killed, and hippocampal CA1 and CA3 neuron counts and cortical lesion volume were measured in histologic brain sections. Preinjury etomidate attenuated beam balance deficits, water maze deficits, hippocampal CA3 neuronal loss, and cortical tissue loss but did not attenuate beam walk deficits or hippocampal CA1 neuronal loss. Postinjury etomidate attenuated water maze deficits, but it did not affect any other outcome measure.

CONCLUSIONS

Administration of etomidate both before and after injury attenuates secondary injury resulting from traumatic brain injury, but the effect is more pronounced with pretreatment. The ineffectiveness of postinjury etomidate on motor and histologic tasks suggests a brief therapeutic treatment window in rats. However, the treatment window in humans is unknown. Lastly, postinjury etomidate did not exacerbate neurologic or histologic outcome.

Physical medicine and rehabilitation consultation: relationships with acute functional outcome, length of stay, and discharge planning after traumatic brain injury

OBJECTIVE

Patients hospitalized with traumatic brain injury comprise a large portion of the population treated at trauma centers, and physiatry consultants evaluate many traumatic brain injury patients in this setting. The purpose of this study was to delineate relationships between physical medicine and rehabilitation consultation in this population and acute functional outcome, length of stay, and discharge planning.

DESIGN

Data were obtained for 1866 adult patients hospitalized with nonfatal traumatic brain injury. Functional outcome was determined using a modification of the FIM trade mark. Descriptive and regression analyses were used to determine the relationship of physical medicine and rehabilitation consultation to acute discharge FIM score, length of stay, and discharge disposition.

RESULTS

Patients receiving physical medicine and rehabilitation consultation had more severe injuries, lower acute discharge FIM scores, and longer length of stay. However, multivariate analysis showed that earlier (<48 hr after admission) physical medicine and rehabilitation consultation resulted in significantly better FIM scores with transfers (odds ratio, 2.61; 95% confidence interval, 1.06-6.40) and locomotion (odds ratio, 3.54; 95% confidence interval, 1.34-9.32) and a significantly shorter acute length of stay (P = 0.001).

CONCLUSIONS

Early physical medicine and rehabilitation consultation may positively impact functional status and length of stay for patients with traumatic brain injury during acute hospitalization. Additional work is needed to determine how physical medicine and rehabilitation consultation impacts rehabilitation-specific medical issues, long-term functional outcome, and healthcare costs.

Caspase-8 expression and proteolysis in human brain after severe head injury

Programmed cell death involves a complex and interrelated cascade of cysteine proteases termed caspases that are synthesized as inactive zymogens, which are proteolytically processed to active enzymes. Caspase-8 is an initiator caspase that becomes activated when Fas death receptor-Fas ligand (FasL) coupling on the cell surface leads to coalescence of a "death complex" perpetuating the programmed cell death cascade. In this study, brain tissue samples removed from adult patients during the surgical management of severe intracranial hypertension after traumatic brain injury (TBI; n=17) were compared with postmortem control brain tissue samples (n=6). Caspase-8 mRNA was measured by semiquantitative reverse transcription and polymerase chain reaction, and caspase-8 protein was examined by Western blot and immunocytochemistry. Fas and FasL were also examined using Western blot. Caspase-8 mRNA and protein were increased in TBI patients vs. controls, and caspase-8 protein was predominately expressed in neurons. Proteolysis of caspase-8 to 20-kDa fragments was seen only in TBI patients. Fas was also increased after TBI vs. control and was associated with relative levels of caspase-8, supporting formation of a death complex. These data identify additional steps in the programmed cell death cascade involving Fas death receptors and caspase-8 after TBI in humans.

Amantadine improves water maze performance without affecting motor behavior following traumatic brain injury in rats

Amantadine, a dopamine agonist, is reported to have beneficial effects on the neurobehavioral sequelae of clinical brain injury. However, there are currently no published laboratory reports on its use in the assessment of functional or histopathological outcome following experimental traumatic brain injury (TBI). To this end, we examined the effects of daily amantadine treatment on functional recovery (motor and Morris water maze performance) and hippocampal neuronal survival following controlled cortical impact (CCI) injury (4 meters/sec, 2.7 mm tissue deformation). Male Sprague-Dawley rats were pretrained on motor performance tasks (beam balance and beam walking) one day prior to injury and tested on post-operative days 1-5. Additionally, all subjects were trained on the Morris water maze on post-operative days 14-18. Beginning one day after CCI injury or sham surgery, animals were injected once daily for 18 days with either amantadine (10 mg/kg, i.p.) or saline. The amantadine treatment regimen was ineffective in promoting motor recovery and increasing survival of hippocampal neurons in both the CA1 and CA3 regions following TBI, but did show improved swim latencies during the five days of water maze testing (Day 14 vs. Day 18, p < 0.01) when compared to saline controls. Mean (+/- SE) swim latencies on Day 18 were 15.12 +/- 2.8, 13.25 +/- 4.18, 70.83 +/- 11.1, and 38.5 +/- 3.55 sec for the sham/saline, sham/amantadine, injured/saline, and injured/amantadine treatment groups, respectively. Thus, while the daily administration of amantadine exhibited a neutral effect on motor behavior, it produced a modest attenuation of water maze performance deficits. This latter finding is consistent with published clinical data suggesting a beneficial effect on functional outcome with amantadine therapy.

Moderate hypothermia may be detrimental after traumatic brain injury in fentanyl-anesthetized rats

OBJECTIVES

To determine whether transient, moderate hypothermia is beneficial after traumatic brain injury in fentanyl-anesthetized rats.

DESIGN

Prospective, randomized study.

SETTING

University-based animal research facility.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

All rats were intubated, mechanically ventilated, and anesthetized with fentanyl (10 microg/kg intravenous bolus and then 50 microg.kg(-1).hr(-1) infusion). Controlled cortical impact was performed to the left parietal cortex, followed immediately by 1 hr of either normothermia (brain temperature 37 +/- 0.5 degrees C) or hypothermia (brain temperature 32 +/- 0.5 degrees C). Hypothermic rats were rewarmed gradually over 1 hr. Fentanyl anesthesia and mechanical ventilation were continued in both groups until the end of rewarming (2 hrs after traumatic brain injury).

MEASUREMENTS AND MAIN RESULTS

Histologic assessment performed 72 hrs after traumatic brain injury was the primary outcome variable. Secondary outcome variables were physiologic variables monitored during the first 2 hrs after traumatic brain injury and plasma catecholamine and serum fentanyl concentrations measured at the end of both hypothermia and rewarming (1 and 2 hrs after traumatic brain injury). Contusion volume was larger in hypothermic vs. normothermic rats (44.3 +/- 4.2 vs. 28.6 +/- 4.0 mm, p <.05), but hippocampal neuronal survival did not differ between groups. Physiologic variables did not differ between groups. Plasma dopamine and norepinephrine concentrations were increased at the end of hypothermia in hypothermic (vs. normothermic) rats (p <.05), indicating that hypothermia augmented the systemic stress response. Similarly, serum fentanyl concentrations were higher in hypothermic (vs. normothermic) rats at the end of both hypothermia and rewarming (p <.05), demonstrating that hypothermia reduced the clearance and/or metabolism of fentanyl.

CONCLUSIONS

Moderate hypothermia was detrimental after experimental traumatic brain injury in fentanyl-anesthetized rats. Since treatment with hypothermia has provided reliable benefit in experimental traumatic brain injury with inhalational anesthetics, these results indicate that the choice of anesthesia/analgesia after traumatic brain injury may dramatically influence response to other therapeutic interventions, such as hypothermia. Given that narcotics commonly are administered to patients after severe traumatic brain injury, this study may have clinical implications.

Alterations in inducible 72-kDa heat shock protein and the chaperone cofactor BAG-1 in human brain after head injury

The stress response in injured brain is well characterized after experimental ischemic and traumatic brain injury (TBI); however, the induction and regulation of the stress response in humans after TBI remains largely undefined. Accordingly, we examined injured brain tissue from adult patients (n = 8) that underwent emergent surgical decompression after TBI, for alterations in the inducible 72-kDa heat shock protein (Hsp70), the constitutive 73-kDa heat shock protein (Hsc70), and isoforms of the chaperone cofactor BAG-1. Control samples (n = 6) were obtained postmortem from patients dying of causes unrelated to CNS trauma. Western blot analysis showed that Hsp70, but not Hsc70, was increased in patients after TBI versus controls. Both Hsp70 and Hsc70 coimmunoprecipitated with the cofactor BAG-1. The 33 and 46, but not the 50-kDa BAG-1 isoforms were increased in patients after TBI versus controls. The ratio of the 46/33-kDa isoforms was increased in TBI versus controls, suggesting negative modulation of Hsp70/Hsc70 protein refolding activity in injured brain. These data implicate induction of the stress response and its modulation by the chaperone cofactor and Bcl-2 family member BAG-1, after TBI in humans.

Validating the Functional Capacity Index as a measure of outcome following blunt multiple trauma

BACKGROUND

The validity of the Functional Capacity Index (FCI) is evaluated by examining its distributional characteristics, its correlation with other well-known measures of outcome and its ability to discriminate among persons with injuries of varying type and severity.

METHODS

A telephone survey which included the FCI and the SF-36 was administered 1 year post-injury to 1240 blunt trauma patients discharged from 12 trauma centers. A subsample of 656 patients also completed the Sickness Impact Profile (SIP) by mail.

RESULTS

FCI scores correlated well with the physical health subscores of the SIP and SF-36. They also correlated well with self-reported change in health status and return to work. The FCI, when compared to either the SF-36 or the SIP, however, appears to discriminate better among patients according to the presence and severity of head trauma.

CONCLUSIONS

While further testing of the FCI is needed, it holds promise as a preference based measure for assessing the physical impact of trauma.

Effect of hyperventilation on extracellular concentrations of glutamate, lactate, pyruvate, and local cerebral blood flow in patients with severe traumatic brain injury

OBJECTIVE

To determine the potential adverse effects of brief periods of hyperventilation commonly used for acute neurologic deterioration.

DESIGN

Prospective clinical trial.

SETTING

University medical school.

PATIENTS

Twenty patients with severe traumatic brain injury.

INTERVENTIONS

The effect of 30 mins of hyperventilation (mean PaCO2, 24.6 mm Hg) on the extracellular metabolites associated with ischemia, and on local cerebral blood flow was studied by using microdialysis and local cerebral blood flow techniques. Normal appearing brain adjacent to evacuated hemorrhagic contusions or underlying evacuated subdural hematomas was studied. Hyperventilation trials were done 24-36 hrs after injury and again at 3-4 days after injury. Dialysate concentrations of glutamate, lactate, and pyruvate were measured before and for 4 hrs after the hyperventilation trials.

MEASUREMENTS AND MAIN RESULTS

At 24-36 hrs, hyperventilation led to a >or=10% increase in the extracellular concentrations of glutamate in 14 of 20 patients, with concentrations in those 14 patients 13.7-395% above baseline; a >or=10% increase in lactate in 7 of 20 patients (11.6-211% above baseline); and a >or=10% increase in the lactate/pyruvate ratio in eight of 20 patients (10.8-227% above baseline). At 3-4 days after injury, ten of 13 patients had an increase in glutamate of >or=10%, while only three of 13 patients had an increase in extracellular lactate and two of 13 patients had an increase in the lactate/pyruvate ratio of this magnitude. The hyperventilation associated increases in extracellular glutamate and lactate concentrations were significant ( P<.05; one-sample Student's -test) at both time points after injury, as was the lactate/pyruvate ratio at 24-36 hrs. A >or=10% decline in local cerebral blood flow was observed with hyperventilation in five of 20 patients at 24-36 hrs (range, 10.2-18.7% below baseline), and in ten of 13 patients studied at 3-4 days (11.3-54% below baseline). There was no correlation with the presence or absence of local CO2 vasoresponsivity and increases in the extracellular metabolites at either the early or late time points.

CONCLUSIONS

In brain tissue adjacent to cerebral contusions or underlying subdural hematomas, even brief periods of hyperventilation can significantly increase extracellular concentrations of mediators of secondary brain injury. These hyperventilation-induced changes are much more common during the first 24-36 hrs after injury than at 3-4 days.

Changes in expression of amyloid precursor protein and interleukin-1beta after experimental traumatic brain injury in rats

There is increasing evidence linking neurodegenerative mechanisms in Alzheimer's disease (AD) and traumatic brain injury (TBI), including increased production of amyloid precursor protein (APP), and amyloid-beta (Abeta) peptide. In vitro data indicate that expression of APP may be regulated in part by the inflammatory cytokine IL-1beta. To further investigate the mechanisms involved, we measured APP and IL-1beta protein levels and examined immunohistochemical localization of APP in brain tissue from rats subjected to controlled cortical impact (CCI) injury. Animals were examined at time intervals ranging from 3 h to 4 weeks after TBI. The 24-h time point revealed a dramatic increase in APP immunoreactivity, detected with both N- and C-terminal antibodies, in the hippocampus and cortex ipsilateral to injury. This finding was sustained up to 3 days post-injury. At these early time points, APP increase was particularly robust in the white matter axonal tracts. By 14 days after injury, APP immunoreactivity was not significantly different from sham controls in cortex, but remained slightly elevated in hippocampus. Western blot data corroborated early increases in hippocampal and cortical APP in injured versus control animals. Despite profound APP changes, no Abeta deposits were observed at any time after injury. Hippocampal and cortical IL-1beta increases were even more robust, with IL-1beta levels peaking by 6 h post-injury and returning to baseline by 24-72 h. Our results demonstrate that both APP and IL-1beta are rapidly elevated after injury. Because of the rapidity in the IL-1beta peak increase, it may serve a role in regulation of APP expression after TBI.

Absence of a diastolic velocity notch does not indicate hyperemia in traumatic brain injured patients without elevated cerebral blood flow velocity

Elevated blood flow velocity (BFV), measured by transcranial Doppler (TCD), has been associated with hyperemia and cerebral vasospasm. This study examined whether the lack of a diastolic notch within the TCD waveform was associated with relative hyperemia within 5 days after injury in 35 traumatic brain injured (TBI) patients. Hyperemia (avD(O2) of < 4 ml/dL) was present in 16 patients and absent in 19 patients. Two clinicians independently coded TCD waveforms based on the presence of a diastolic notch (88% agreement). There was no significant difference in the presence of a diastolic notch by group; a diastolic notch was present in 57% (11/19) of patients without hyperemia and 81% (13/16) of patients with hyperemia. Sensitivity and specificity of detecting hyperemia using the diastolic notch was 18.7% and 57.9% respectively. The results showed that relative hyperemia was present without an elevation in blood flow velocities, and that the lack of a diastolic notch did not detect the presence of hyperemia in the TBI patient.

Regulation of interstitial excitatory amino acid concentrations after cortical contusion injury

Increases in brain interstitial excitatory amino acid (EAA(I)) concentrations after ischemia are ameliorated by use-dependent Na+ channel antagonists and by supplementing interstitial glucose, but the regulation of EAA(I) after traumatic brain injury (TBI) is unknown. We studied the regulation of EAA(I) after TBI using the controlled cortical impact model in rats. To monitor changes in EAA(I), microdialysis probes were placed in the cortex adjacent to the contusion and in the ipsilateral hippocampus. Significant increases in dialysate EAA(I) after TBI were found compared to levels measured in sham controls. Treatment with the use-dependent Na+ channel antagonist 619C89 (30 mg/kg i.v.) did not significantly decrease dialysate glutamate compared to vehicle controls in hippocampus (10.4+/-2.4 vs. 11.9+/-1.6 microM), but there was significant decrease in dialysate glutamate in cortex after 619C89 treatment (19.3+/-3 vs. 12.6+/-1.1 microM, P<0.05). Addition of 30 mM glucose to the dialysate, a treatment that decreases EAA(I) after ischemia, had no significant effect upon dialysate glutamate after TBI in cortex (20.0+/-4.9 vs. 11.7+/-3.4 microM) or in hippocampus (10.9+/-2.0 vs. 8.9+/-2.4 microM). These results suggest that neither increased release of EAAs due to Na+ channel-mediated depolarization nor failure of glutamate reuptake due to glucose deprivation can explain the majority of the increase in EAA(I) following TBI.

Conventional and functional proteomics using large format two-dimensional gel electrophoresis 24 hours after controlled cortical impact in postnatal day 17 rats

Conventional and functional proteomics have significant potential to expand our understanding of traumatic brain injury (TBI) but have not yet been used. The purpose of the present study was to examine global hippocampal protein changes in postnatal day (PND) 17 immature rats 24 h after moderate controlled cortical impact (CCI). Silver nitrate stains or protein kinase B (PKB) phosphoprotein substrate antibodies were used to evaluate high abundance or PKB pathway signal transduction proteins representing conventional and functional proteomic approaches, respectively. Isoelectric focusing was performed over a nonlinear pH range of 3-10 with immobilized pH gradients (IPG strips) using supernatant from the most soluble cellular protein fraction of hippocampal tissue protein lysates from six paired sham and injured PND 17 rats. Approximately 1,500 proteins were found in each silver stained gel with 40% matching of proteins. Of these 600 proteins, 52% showed a twofold, 20% a fivefold, and 10% a 10-fold decrease or increase. Spot matching with existing protein databases revealed changes in important cytoskeletal and cell signalling proteins. PKB substrate protein phosphorylation was best seen in large format two-dimensional blots and known substrates of PKB such as glucose transporter proteins 3 and 4 and forkhead transcription factors, identified based upon molecular mass and charge, showed altered phosphorylation 24 h after injury. These results suggest that combined conventional and functional proteomic approaches are powerful, complementary and synergistic tools revealing multiple protein changes and posttranslational protein modifications that allow for more specific and comprehensive functional assessments after pediatric TBI.

Acute systemic administration of interleukin-10 suppresses the beneficial effects of moderate hypothermia following traumatic brain injury in rats

Traumatic injury to the central nervous system initiates inflammatory processes such as the synthesis of proinflammatory mediators that contribute to secondary tissue damage. Hence, administration of anti-inflammatory cytokines, such as interleukin-10 (IL-10) may be neuroprotective. Moderate hypothermia (30-32 degrees C) also decreases the pro-inflammatory response to traumatic brain injury (TBI). Thus, we hypothesized that the combination of IL-10 and hypothermia would provide synergistic neuroprotective effects after TBI. To test this hypothesis, fifty isoflurane-anesthetized rats underwent a controlled cortical impact (2.7 mm tissue deformation at 4 m/s) or sham injury and then were randomly assigned to one of five conditions (TBI/VEH Normothermia (37 degrees C), TBI/VEH Hypothermia (32 degrees C for 3 h), TBI/IL-10 Normothermia, TBI/IL-10 Hypothermia, and Sham/VEH Normothermia). Human IL-10 (5 microg) or VEH was administered (i.p.) 30 min after surgery. Function was assessed by established motor and cognitive tests on post-operative days 1-5 and 14-18, respectively. Cortical lesion volume and hippocampal CA(1)/CA(3) cell survival were quantified at 4 weeks. Brain sections from 15 additional rats were immunohistochemically assessed (MoAB RP-3) to determine neutrophil accumulation at 5 h after TBI. The administration of IL-10 after TBI produced an approximately 75% reduction in the number of RP-3-positive cells in both the normothermic and hypothermic groups vs. the normothermic vehicle-treated group (P<0.05), but did not improve functional outcome. In contrast, hypothermia alone enhanced both motor and cognitive function and increased CA(3) neuronal survival after TBI. Contrary to our hypothesis, systemic administration of IL-10 combined with hypothermia did not provide synergistic neuroprotective effects after TBI. Rather, IL-10 administration suppressed the beneficial effects produced by hypothermia alone after TBI. The mechanism(s) for the negative effects of IL-10 combined with hypothermia after TBI remain to be determined.