Changes of sympatho-adrenal and hypothalamo-pituitary-adrenocortical system in patients with head injury

Experimental Models of Hospital-Acquired Infections After Traumatic Brain Injury: Challenges and Opportunities

Patients hospitalized after a moderate or severe traumatic brain injury (TBI) are at increased risk of nosocomial infections, including bacterial pneumonia and other upper respiratory tract infections. Infections represent a secondary immune challenge for vulnerable TBI patients that can lead to increased morbidity and poorer long-term prognosis. This review first describes the clinical significance of infections after TBI, delving into the known mechanisms by which a TBI can alter systemic immunological responses towards an immunosuppressive state, leading to promotion of increased vulnerability to infections. Pulmonary dysfunction resulting from respiratory tract infections is considered in the context of neurotrauma, including the bidirectional relationship between the brain and lungs. Turning to pre-clinical modeling, current laboratory approaches to study experimental TBI and lung infections are reviewed, to highlight findings from the limited key studies to date that have incorporated both insults. Then, practical decisions for the experimental design of animal studies of post-injury infections are discussed. Variables associated with the host animal, the infectious agent (e.g., species, strain, dose, and administration route), as well as the timing of the infection relative to the injury model are important considerations for model development. Together, the purpose of this review is to highlight the significant clinical need for increased pre-clinical research into the two-hit insult of a hospital-acquired infection after TBI to encourage further scientific enquiry in the field.

Association of Early Dexmedetomidine Utilization With Clinical and Functional Outcomes Following Moderate-Severe Traumatic Brain Injury: A Transforming Clinical Research and Knowledge in Traumatic Brain Injury Study

OBJECTIVE

To examine early sedation patterns, as well as the association of dexmedetomidine exposure, with clinical and functional outcomes among mechanically ventilated patients with moderate-severe traumatic brain injury (msTBI).

DESIGN

Retrospective cohort study with prospectively collected data.

SETTING

Eighteen Level-1 Trauma Centers, United States.

PATIENTS

Adult (age > 17) patients with msTBI (as defined by Glasgow Coma Scale < 13) who required mechanical ventilation from the Transforming Clinical Research and Knowledge in TBI (TRACK-TBI) study.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Using propensity-weighted models, we examined the association of early dexmedetomidine exposure (within the first 5 d of ICU admission) with the primary outcome of 6-month Glasgow Outcomes Scale Extended (GOS-E) and the following secondary outcomes: length of hospital stay, hospital mortality, 6-month Disability Rating Scale (DRS), and 6-month mortality. The study population included 352 subjects who required mechanical ventilation within 24 hours of admission. The initial sedative medication was propofol for 240 patients (68%), midazolam for 59 patients (17%), ketamine for 6 patients (2%), dexmedetomidine for 3 patients (1%), and 43 patients (12%) never received continuous sedation. Early dexmedetomidine was administered in 77 of the patients (22%), usually as a second-line agent. Compared with unexposed patients, early dexmedetomidine exposure was not associated with better 6-month GOS-E (weighted odds ratio [OR] = 1.48; 95% CI, 0.98-2.25). Early dexmedetomidine exposure was associated with lower DRS (weighted OR = -3.04; 95% CI, -5.88 to -0.21). In patients requiring ICP monitoring within the first 24 hours of admission, early dexmedetomidine exposure was associated with higher 6-month GOS-E score (OR 2.17; 95% CI, 1.24-3.80), lower DRS score (adjusted mean difference, -5.81; 95% CI, -9.38 to 2.25), and reduced length of hospital stay (hazard ratio = 1.50; 95% CI, 1.02-2.20).

CONCLUSION

Variation exists in early sedation choice among mechanically ventilated patients with msTBI. Early dexmedetomidine exposure was not associated with improved 6-month functional outcomes in the entire population, although may have clinical benefit in patients with indications for ICP monitoring.

Safety, Efficacy, and Clinical Outcomes of Dexmedetomidine for Sedation in Traumatic Brain Injury: A Scoping Review

Dexmedetomidine is a promising alternative sedative agent for moderate-severe Traumatic brain injury (TBI) patients. Although the data are limited, the posited benefits of dexmedetomidine in this population are a reduction in secondary brain injury compared with current standard sedative regimens. In this scoping review, we critically appraised the literature to examine the effects of dexmedetomidine in patients with moderate-severe TBI to examine the safety, efficacy, and cerebral and systemic physiological outcomes within this population. We sought to identify gaps in the literature and generate directions for future research. Two researchers and a librarian queried PubMed, Embase, Scopus, and APA PsycINFO databases. Of 920 studies imported for screening, 11 were identified for inclusion in the review. The primary outcomes in the included studied were cerebral physiology, systemic hemodynamics, sedation levels and delirium, and the presence of paroxysmal sympathetic hyperactivity. Dexmedetomidine dosing ranged from 0.2 to 1 ug/kg/h, with 3 studies using initial boluses of 0.8 to 1.0 ug/kg over 10 minutes. Dexmedetomidine used independently or as an adjunct seems to exhibit a similar hemodynamic safety profile compared with standard sedation regimens, albeit with transient episodes of bradycardia and hypotension, decrease episodes of agitation and may serve to alleviate symptoms of sympathetic hyperactivity. This scoping review suggests that dexmedetomidine is a safe and efficacious sedation strategy in patients with TBI. Given its rapid onset of action and anxiolytic properties, dexmedetomidine may serve as a feasible sedative for TBI patients.

Neural-Cardiac Inflammasome Axis after Traumatic Brain Injury

Traumatic brain injury (TBI) affects not only the brain but also peripheral organs like the heart and the lungs, which influences long-term outcomes. A heightened systemic inflammatory response is often induced after TBI, but the underlying pathomechanisms that contribute to co-morbidities remain poorly understood. Here, we investigated whether extracellular vehicles (EVs) containing inflammasome proteins are released after severe controlled cortical impact (CCI) in C57BL/6 mice and cause activation of inflammasomes in the heart that result in tissue damage. The atrium of injured mice at 3 days after TBI showed a significant increase in the levels of the inflammasome proteins AIM2, ASC, caspases-1, -8 and -11, whereas IL-1β was increased in the ventricles. Additionally, the injured cortex showed a significant increase in IL-1β, ASC, caspases-1, -8 and -11 and pyrin at 3 days after injury when compared to the sham. Serum-derived extracellular vesicles (EVs) from injured patients were characterized with nanoparticle tracking analysis and Ella Simple Plex and showed elevated levels of the inflammasome proteins caspase-1, ASC and IL-18. Mass spectrometry of serum-derived EVs from mice after TBI revealed a variety of complement- and cardiovascular-related signaling proteins. Moreover, adoptive transfer of serum-derived EVs from TBI patients resulted in inflammasome activation in cardiac cells in culture. Thus, TBI elicits inflammasome activation, primarily in the atrium, that is mediated, in part, by EVs that contain inflammasome- and complement-related signaling proteins that are released into serum and contribute to peripheral organ systemic inflammation, which increases inflammasome activation in the heart.

Association of Brain Injury Biomarkers and Circulatory Shock Following Moderate-Severe Traumatic Brain Injury: A TRACK-TBI Study

INTRODUCTION

Early circulatory shock following traumatic brain injury (TBI) is a multifactorial process; however, the impact of brain injury biomarkers on the risk of shock has not been evaluated. We examined the association between neuronal injury biomarker levels and the development of circulatory shock following moderate-severe TBI.

METHODS

In this retrospective cohort study, we examined adults with moderate-severe TBI (Glasgow Coma Scale score <13) enrolled in the TRACK-TBI study, an 18-center prospective TBI cohort study. The exposures were day-1 levels of neuronal injury biomarkers (glial fibrillary acidic protein, ubiquitin C-terminal hydrolase-L1 [UCH-L1], S100 calcium-binding protein B [S100B], neuron-specific enolase), and of an inflammatory biomarker (high-sensitivity C-reactive protein). The primary outcome was the development of circulatory shock, defined as cardiovascular Sequential Organ Failure Assessment Score ≥2 within 72 hours of admission. Association between day-1 biomarker levels and the development of circulatory shock was assessed with regression analysis.

RESULTS

The study included 392 subjects, with a mean age of 40 years; 314 (80%) were male and 165 (42%) developed circulatory shock. Median (interquartile range) day-1 levels of UCH-L1 (994.8 [518.7 to 1988.2] pg/mL vs. 548.1 [280.2 to 1151.9] pg/mL; P <0.0001) and S100B (0.47 μg/mL [0.25 to 0.88] vs. 0.27 [0.16 to 0.46] μg/mL; P <0.0001) were elevated in those who developed early circulatory shock compared with those who did not. In multivariable regression, there were associations between levels of both UCH-L1 (odds ratio, 1.63 [95% confidence interval, 1.25-2.12]; P <0.0005) and S100B (odds ratio, 1.73 [95% confidence interval 1.27-2.36]; P <0.0005) with the development of circulatory shock.

CONCLUSION

Neuronal injury biomarkers may provide the improved mechanistic understanding and possibly early identification of patients at risk for early circulatory shock following moderate-severe TBI.

Diet-microbiome-gut-brain nexus in acute and chronic brain injury

In recent years, appreciation for the gut microbiome and its relationship to human health has emerged as a facilitator of maintaining healthy physiology and a contributor to numerous human diseases. The contribution of the microbiome in modulating the gut-brain axis has gained significant attention in recent years, extensively studied in chronic brain injuries such as Epilepsy and Alzheimer’s Disease. Furthermore, there is growing evidence that gut microbiome also contributes to acute brain injuries like stroke(s) and traumatic brain injury. Microbiome-gut-brain communications are bidirectional and involve metabolite production and modulation of immune and neuronal functions. The microbiome plays two distinct roles: it beneficially modulates immune system and neuronal functions; however, abnormalities in the host’s microbiome also exacerbates neuronal damage or delays the recovery from acute injuries. After brain injury, several inflammatory changes, such as the necrosis and apoptosis of neuronal tissue, propagates downward inflammatory signals to disrupt the microbiome homeostasis; however, microbiome dysbiosis impacts the upward signaling to the brain and interferes with recovery in neuronal functions and brain health. Diet is a superlative modulator of microbiome and is known to impact the gut-brain axis, including its influence on acute and neuronal injuries. In this review, we discussed the differential microbiome changes in both acute and chronic brain injuries, as well as the therapeutic importance of modulation by diets and probiotics. We emphasize the mechanistic studies based on animal models and their translational or clinical relationship by reviewing human studies.

Risk Factors and Neurological Outcomes Associated With Circulatory Shock After Moderate-Severe Traumatic Brain Injury: A TRACK-TBI Study

BACKGROUND

Extracranial multisystem organ failure is a common sequela of severe traumatic brain injury (TBI). Risk factors for developing circulatory shock and long-term functional outcomes of this patient subset are poorly understood.

OBJECTIVE

To identify emergency department predictors of circulatory shock after moderate-severe TBI and examine long-term functional outcomes in patients with moderate-severe TBI who developed circulatory shock.

METHODS

We conducted a retrospective cohort study using the Transforming Clinical Research and Knowledge in TBI database for adult patients with moderate-severe TBI, defined as a Glasgow Coma Scale (GCS) score of <13 and stratified by the development of circulatory shock within 72 hours of hospital admission (Sequential Organ Failure Assessment score ≥2). Demographic and clinical data were assessed with descriptive statistics. A forward selection regression model examined risk factors for the development of circulatory shock. Functional outcomes were examined using multivariable regression models.

RESULTS

Of our moderate-severe TBI population (n = 407), 168 (41.2%) developed circulatory shock. Our predictive model suggested that race, computed tomography Rotterdam scores <3, GCS in the emergency department, and development of hypotension in the emergency department were associated with developing circulatory shock. Those who developed shock had less favorable 6-month functional outcomes measured by the 6-month GCS-Extended (odds ratio 0.36, P = .002) and 6-month Disability Rating Scale score (Diff. in means 3.86, P = .002) and a longer length of hospital stay (Diff. in means 11.0 days, P < .001).

CONCLUSION

We report potential risk factors for circulatory shock after moderate-severe TBI. Our study suggests that developing circulatory shock after moderate-severe TBI is associated with poor long-term functional outcomes.

Association of Early Multiple Organ Dysfunction With Clinical and Functional Outcomes Over the Year Following Traumatic Brain Injury: A Transforming Research and Clinical Knowledge in Traumatic Brain Injury Study

OBJECTIVES

Traumatic brain injury is a leading cause of death and disability in the United States. While the impact of early multiple organ dysfunction syndrome has been studied in many critical care paradigms, the clinical impact of early multiple organ dysfunction syndrome in traumatic brain injury is poorly understood. We examined the incidence and impact of early multiple organ dysfunction syndrome on clinical, functional, and disability outcomes over the year following traumatic brain injury.

DESIGN

Retrospective cohort study.

SETTING

Patients enrolled in the Transforming Clinical Research and Knowledge in Traumatic Brain Injury study, an 18-center prospective cohort study of traumatic brain injury patients evaluated in participating level 1 trauma centers.

SUBJECTS

Adult (age > 17 yr) patients with moderate-severe traumatic brain injury (Glasgow Coma Scale < 13). We excluded patients with major extracranial injury (Abbreviated Injury Scale score ≥ 3).

INTERVENTIONS

Development of early multiple organ dysfunction syndrome, defined as a maximum modified Sequential Organ Failure Assessment score greater than 7 during the initial 72 hours following admission.

MEASUREMENTS AND MAIN RESULTS

The main outcomes were: hospital mortality, length of stay, 6-month functional and disability domains (Glasgow Outcome Scale-Extended and Disability Rating Scale), and 1-year mortality. Secondary outcomes included: ICU length of stay, 3-month Glasgow Outcome Scale-Extended, 3-month Disability Rating Scale, 1-year Glasgow Outcome Scale-Extended, and 1-year Disability Rating Scale. We examined 373 subjects with moderate-severe traumatic brain injury. The mean (sd) Glasgow Coma Scale in the emergency department was 5.8 (3.2), with 280 subjects (75%) classified as severe traumatic brain injury (Glasgow Coma Scale 3-8). Among subjects with moderate-severe traumatic brain injury, 252 (68%) developed early multiple organ dysfunction syndrome. Subjects that developed early multiple organ dysfunction syndrome had a 75% decreased odds of a favorable outcome (Glasgow Outcome Scale-Extended 5-8) at 6 months (adjusted odds ratio, 0.25; 95% CI, 0.12-0.51) and increased disability (higher Disability Rating Scale score) at 6 months (adjusted mean difference, 2.04; 95% CI, 0.92-3.17). Subjects that developed early multiple organ dysfunction syndrome experienced an increased hospital length of stay (adjusted mean difference, 11.4 d; 95% CI, 7.1-15.8), with a nonsignificantly decreased survival to hospital discharge (odds ratio, 0.47; 95% CI, 0.18-1.2).

CONCLUSIONS

Early multiple organ dysfunction following moderate-severe traumatic brain injury is common and independently impacts multiple domains (mortality, function, and disability) over the year following injury. Further research is necessary to understand underlying mechanisms, improve early recognition, and optimize management strategies.

Multiorgan Dysfunction After Severe Traumatic Brain Injury: Epidemiology, Mechanisms, and Clinical Management

Traumatic brain injury (TBI) is a major global health problem and a major contributor to morbidity and mortality following multisystem trauma. Extracranial organ dysfunction is common after severe TBI and significantly impacts clinical care and outcomes following injury. Despite this, extracranial organ dysfunction remains an understudied topic compared with organ dysfunction in other critical care paradigms. In this review, we will: 1) summarize the epidemiology of extracranial multiorgan dysfunction following severe TBI; 2) examine relevant mechanisms that may be involved in the development of multi-organ dysfunction following severe TBI; and 3) discuss clinical management strategies to care for these complex patients.

Beyond the Brain: Peripheral Interactions after Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of death and disability, and there are currently no pharmacological treatments known to improve patient outcomes. Unquestionably, contributing toward a lack of effective treatments is the highly complex and heterogenous nature of TBI. In this review, we highlight the recent surge of research that has demonstrated various central interactions with the periphery as a potential major contributor toward this heterogeneity and, in particular, the breadth of research from Australia. We describe the growing evidence of how extracranial factors, such as polytrauma and infection, can significantly alter TBI neuropathology. In addition, we highlight how dysregulation of the autonomic nervous system and the systemic inflammatory response induced by TBI can have profound pathophysiological effects on peripheral organs, such as the heart, lung, gastrointestinal tract, liver, kidney, spleen, and bone. Collectively, this review firmly establishes TBI as a systemic condition. Further, the central and peripheral interactions that can occur after TBI must be further explored and accounted for in the ongoing search for effective treatments.

Brain-gut axis dysfunction in the pathogenesis of traumatic brain injury

Traumatic brain injury (TBI) is a chronic and progressive disease, and management requires an understanding of both the primary neurological injury and the secondary sequelae that affect peripheral organs, including the gastrointestinal (GI) tract. The brain-gut axis is composed of bidirectional pathways through which TBI-induced neuroinflammation and neurodegeneration impact gut function. The resulting TBI-induced dysautonomia and systemic inflammation contribute to the secondary GI events, including dysmotility and increased mucosal permeability. These effects shape, and are shaped by, changes in microbiota composition and activation of resident and recruited immune cells. Microbial products and immune cell mediators in turn modulate brain-gut activity. Importantly, secondary enteric inflammatory challenges prolong systemic inflammation and worsen TBI-induced neuropathology and neurobehavioral deficits. The importance of brain-gut communication in maintaining GI homeostasis highlights it as a viable therapeutic target for TBI. Currently, treatments directed toward dysautonomia, dysbiosis, and/or systemic inflammation offer the most promise.

Multipotential and systemic effects of traumatic brain injury

Traumatic brain injury (TBI) is one of the leading causes of disability and mortality of people at all ages. Biochemical, cellular and physiological events that occur during primary injury lead to a delayed and long-term secondary damage that can last from hours to years. Secondary brain injury causes tissue damage in the central nervous system and a subsequent strong and rapid inflammatory response that may lead to persistent inflammation. However, this inflammatory response is not limited to the brain. Inflammatory mediators are transferred from damaged brain tissue to the bloodstream and produce a systemic inflammatory response in peripheral organs, including the cardiovascular, pulmonary, gastrointestinal, renal and endocrine systems. Complications of TBI are associated with its multiple and systemic effects that should be considered in the treatment of TBI patients. Therefore, in this review, an attempt was made to examine the systemic effects of TBI in detail. It is hoped that this review will identify the mechanisms of injury and complications of TBI, and open a window for promising treatment in TBI complications.

Association of Severe Acute Kidney Injury with Mortality and Healthcare Utilization Following Isolated Traumatic Brain Injury

BACKGROUND/OBJECTIVE

Traumatic brain injury (TBI) is a leading cause of morbidity, mortality, and disability in the USA. While cardiopulmonary dysfunction can result in poor outcomes following severe TBI, the impact of acute kidney injury (AKI) is poorly understood. We examined the association of severe AKI with hospital mortality and healthcare utilization following isolate severe TBI.

METHODS

We conducted a retrospective cohort study using the National Trauma Data Bank from 2007 to 2014. We identified a cohort of adult patients with isolated severe TBI and described the incidence of severe AKI, corresponding to Acute Kidney Injury Network stage 3 disease or greater. We examined the association of severe AKI with the primary outcome of hospital mortality using multivariable logistic regression models. In secondary analyses, we examined the association of severe AKI with dialysis catheter placement, tracheostomy and gastrostomy utilization, and hospital length of stay.

RESULTS

There were 37,851 patients who experienced isolated severe TBI during the study period. Among these patients, 787 (2.1%) experienced severe (Stage 3 or greater) AKI. In multivariable models, the development of severe AKI in the hospital was associated with in-hospital mortality (OR 2.03, 95% CI 1.64-2.52), need for tracheostomy (OR 2.10, 95% CI 1.52-2.89), PEG tube placement (OR 1.88, 95% CI 1.45-2.45), and increased hospital length of stay (p < 0.001).

CONCLUSIONS

The overall incidence of severe AKI is relatively low (2.1%), but is associated with increased mortality and multiple markers of increased healthcare utilization following severe TBI.

Decompressive Craniectomy Improves QTc Interval in Traumatic Brain Injury Patients

Background: Traumatic brain injury (TBI) is commonly associated with cardiac dysfunction, which may be reflected by abnormal electrocardiograms (ECG) and/or contractility. TBI-related cardiac disorders depend on the type of cerebral injury, the region of brain damage and the severity of the intracranial hypertension. Decompressive craniectomy (DC) is commonly used to reduce intra-cranial hypertension (ICH). Although DC decreases ICH rapidly, its effect on ECG has not been systematically studied. The aim of this study was to analyze the changes in ECG in patients undergoing DC. Methods: Adult patients without previously known cardiac diseases treated for isolated TBI with DC were studied. ECG variables, such as: spatial QRS-T angle (spQRS-T), corrected QT interval (QTc), QRS and T axes (QRS_ax and T_ax, respectively), STJ segment and the index of cardio-electrophysiological balance (iCEB) were analyzed before DC and at 12–24 h after DC. Changes in ECG were analyzed according to the occurrence of cardiac arrhythmias and 28-day mortality. Results: 48 patients (17 female and 31 male) aged 18–64 were studied. Intra-cranial pressure correlated with QTc before DC (p < 0.01, r = 0.49). DC reduced spQRS-T (p < 0.001) and QTc interval (p < 0.01), increased Tax (p < 0.01) and changed STJ in a majority of leads but did not affect QRS_ax and iCEB. The iCEB was relatively increased before DC in patients who eventually experienced cardiac arrhythmias after DC (p < 0.05). Higher post-DC iCEB was also noted in non-survivors (p < 0.05), although iCEB values were notably heart rate-dependent. Conclusions: ICP positively correlates with QTc interval in patients with isolated TBI, and DC for relief of ICH reduces QTc and spQRS-T. However, DC might also increase risk for life-threatening cardiac arrhythmias, especially in ICH patients with notably prolonged QTc before and increased iCEB after DC.

Dementia, Depression, and Associated Brain Inflammatory Mechanisms after Spinal Cord Injury

Evaluation of the chronic effects of spinal cord injury (SCI) has long focused on sensorimotor deficits, neuropathic pain, bladder/bowel dysfunction, loss of sexual function, and emotional distress. Although not well appreciated clinically, SCI can cause cognitive impairment including deficits in learning and memory, executive function, attention, and processing speed; it also commonly leads to depression. Recent large-scale longitudinal population-based studies indicate that patients with isolated SCI (without concurrent brain injury) are at a high risk of dementia associated with substantial cognitive impairments. Yet, little basic research has addressed potential mechanisms for cognitive impairment and depression after injury. In addition to contributing to disability in their own right, these changes can adversely affect rehabilitation and recovery and reduce quality of life. Here, we review clinical and experimental work on the complex and varied responses in the brain following SCI. We also discuss potential mechanisms responsible for these less well-examined, important SCI consequences. In addition, we outline the existing and developing therapeutic options aimed at reducing SCI-induced brain neuroinflammation and post-injury cognitive and emotional impairments.

The blockade of corticotropin-releasing factor 1 receptor attenuates anxiety-related symptoms and hypothalamus-pituitary-adrenal axis reactivity in mice with mild traumatic brain injury

Recent studies have shown that mild traumatic brain injury (mTBI) is associated with higher risk for anxiety-related disorders. Dysregulation in the hypothalamus-pituitary-adrenal (HPA) axis following mTBI has been proposed to be involved in the development of neurobehavioral abnormalities; however, the underlying mechanisms are largely unknown. The aim of this study was to determine whether the corticotropin-releasing-factor-1 (CRF-1) receptor is involved in the regulation of anxiety-related symptoms in a mouse model of mTBI. Animals with or without mTBI received intracerebroventricular injections of a CRF-1 receptor agonist (CRF; 0.01 nmol/mouse) or antagonist (antalarmin; 1 µg/mouse) for 5 days, and then the animals were subjected to anxiety tests (light-dark box and zero maze). The levels of adrenocorticotropic hormone and corticosterone, the most important markers of HPA axis, were also measured after behavioral tests. Our results indicated that mTBI-induced anxiety-related symptoms in mice through increased levels of adrenocorticotropic hormone and corticosterone, showing HPA axis hyperactivity. Interestingly, activation of CRF receptor by a subthreshold dose of CRF resulted in significant increases in anxiety-like behaviors and HPA axis response to stress, whereas blockade of CRF receptors by a subthreshold dose of antalarmin decreased anxiety-related symptoms and HPA axis response to stress in mTBI-induced mice. Collectively, these findings suggest that the CRF-1 receptor plays an important role in the regulation of anxiety-related behaviors following mTBI induction in mice and support the hypothesis that blockade of the CRF-1 receptor may be a promising therapeutic target for anxiety-related disorders in patients with TBI.

Beta-adrenergic blockade for attenuation of catecholamine surge after traumatic brain injury: a randomized pilot trial

Background

Beta-blockers have been proven in multiple studies to be beneficial in patients with traumatic brain injury. Few prospective studies have verified this and no randomized controlled trials. Additionally, most studies do not titrate the dose of beta-blockers to therapeutic effect. We hypothesize that propranolol titrated to effect will confer a survival benefit in patients with traumatic brain injury.

Methods

A randomized controlled pilot trial was performed during a 24-month period. Patients with traumatic brain injury were randomized to propranolol or control group for a 14-day study period. Variables collected included demographics, injury severity, physiologic parameters, urinary catecholamines, and outcomes. Patients receiving propranolol were compared with the control group.

Results

Over the study period, 525 patients were screened, 26 were randomized, and 25 were analyzed. Overall, the mean age was 51.3 years and the majority were male with blunt mechanism. The mean Injury Severity Score was 21.8 and median head Abbreviated Injury Scale score was 4. Overall mortality was 20.0%. Mean arterial pressure was higher in the treatment arm as compared with control (p=0.021), but no other differences were found between the groups in demographics, severity of injury, severity of illness, physiologic parameters, or mortality (7.7% vs. 33%; p=0.109). No difference was detected over time in any variables with respect to treatment, urinary catecholamines, or physiologic parameters. Glasgow Coma Scale (GCS), Sequential Organ Failure Assessment, and Acute Physiology and Chronic Health Evaluation scores all improved over time. GCS at study end was significantly higher in the treatment arm (11.7 vs. 8.9; p=0.044). Finally, no difference was detected with survival analysis over time between groups.

Conclusions

Despite not being powered to show statistical differences between groups, GCS at study end was significantly improved in the treatment arm and mortality was improved although not at a traditional level of significance. The study protocol was safe and feasible to apply to an appropriately powered larger multicenter study.

Level of evidence

Level 2—therapeutic.

Traumatic brain injury induced neuroendocrine changes: acute hormonal changes of anterior pituitary function

PURPOSE

It is estimated that approximately 69 million individuals worldwide will sustain a TBI each year, which accounts for substantial morbidity and mortality in both children and adults. TBI may lead to significant neuroendocrine changes, if the delicate pituitary is ruptured. In this review, we focus on the anterior pituitary hormonal changes in the acute post-TBI period and we present the evidence supporting the need for screening of anterior pituitary function in the early post-TBI time along with current suggestions regarding the endocrine assessment and management of these patients.

METHODS

Original systematic articles with prospective and/or retrospective design studies of acute TBI were included, as were review articles and case series.

RESULTS

Although TBI may motivate an acute increase of stress hormones, it may also generate a wide spectrum of anterior pituitary hormonal deficiencies. The frequency of post-traumatic anterior hypopituitarism (PTHP) varies according to the severity, the type of trauma, the time elapsed since injury, the study population, and the methodology used to diagnose pituitary hormone deficiency. Early neuroendocrine abnormalities may be transient, but additional late ones may also appear during the course of rehabilitation.

CONCLUSIONS

Acute hypocortisolism should be diagnosed and managed promptly, as it can be life-threatening, but currently there is no evidence to support treatment of acute GH, thyroid hormones or gonadotropins deficiencies. However, a more comprehensive assessment of anterior pituitary function should be undertaken both in the early and in the post-acute phase, since ongoing hormone deficiencies may adversely affect the recovery and quality of life of these patients.

Initial free cortisol dynamics following blunt multiple trauma and traumatic brain injury: A clinical study

Objective

To determine free and total cortisol serum concentrations in the first 24 h after trauma and to evaluate the influence of traumatic brain injury (TBI) on their dynamics.

Methods

This prospective cohort study enrolled patients who had experienced multiple trauma and were admitted to a level 1 trauma centre. The patients were divided in two groups based on the presence of TBI according to clinical and radiological findings. Blood was collected initially as well as at 12 h and 24 h after the traumatic injury. Total cortisol, corticosteroid binding globulin (CBG) and free cortisol levels were determined.

Results

The study analysed data from 49 patients (36 males and 13 females) with a mean ± SD age of 45.0 ± 16.0 years. Of these, 36 presented with TBI and 13 had multiple injuries without TBI. Patients with TBI showed significantly lower concentrations of total cortisol and free cortisol compared with patients without TBI. Repeated measures analysis revealed different concentration dynamics in patients with TBI, with no increase in cortisol after trauma.

Conclusion

Multiple trauma patients with TBI are at risk of acute impaired cortisol secretion and show an attenuated stress response as early as 12 h after injury.

Brain-Heart Interactions in Traumatic Brain Injury

The cardiovascular manifestations associated with nontraumatic head disorders are commonly known. Similar manifestations have been reported in patients with traumatic brain injury (TBI); however, the underlying mechanisms and impact on the patient's clinical outcomes are not well explored. The neurocardiac axis theory and neurogenic stunned myocardium phenomenon could partly explain the brain-heart link and interactions and can thus pave the way to a better understanding and management of TBI. Several observational retrospective studies have shown a promising role for beta-adrenergic blockers in patients with TBI in reducing the overall TBI-related mortality. However, several questions remain to be answered in clinical randomized-controlled trials, including population selection, beta blocker type, dosage, timing, and duration of therapy, while maintaining the optimal mean arterial pressure and cerebral perfusion pressure in patients with TBI.

MANAGEMENT OF ENDOCRINE DISEASE: Neuroendocrine surveillance and management of neurosurgical patients

Advances in the management of traumatic brain injury, subarachnoid haemorrhage and intracranial tumours have led to improved survival rates and an increased focus on quality of life of survivors. Endocrine sequelae of the acute brain insult and subsequent neurosurgery, peri-operative fluid administration and/or cranial irradiation are now well described. Unrecognised acute hypopituitarism, particularly ACTH/cortisol deficiency and diabetes insipidus, can be life threatening. Although hypopituitarism may be transient, up to 30% of survivors of TBI have chronic hypopituitarism, which can diminish quality of life and hamper rehabilitation. Patients who survive SAH may also develop hypopituitarism, though it is less common than after TBI. The growth hormone axis is most frequently affected. There is also accumulating evidence that survivors of intracranial malignancy, who have required cranial irradiation, may develop hypopituitarism. The time course of the development of hormone deficits is varied, and predictors of pituitary dysfunction are unreliable. Furthermore, diagnosis of GH and ACTH deficiency require dynamic testing that can be resource intensive. Thus the surveillance and management of neuroendocrine dysfunction in neurosurgical patients poses significant logistic challenges to endocrine services. However, diagnosis and management of pituitary dysfunction can be rewarding. Appropriate hormone replacement can improve quality of life, prevent complications such as muscle atrophy, infection and osteoporosis and improve engagement with physiotherapy and rehabilitation.

Early stage alterations of catecholamine and adrenocorticotropic hormone levels in posttraumatic acute diffuse brain swelling

Posttraumatic acute diffuse brain swelling (PADBS) is characterized by serious brain bulk enlargement rapidly following trauma and is a major cause of elevated intracranial pressure and thus mortality. The pathogenesis of PADBS is not clearly understood, and the early stage alterations of catecholamine (CA) and adrenocorticotropic hormone (ACTH) levels in PADBS also remain largely unknown. The objective of this study was to investigate CA and ACTH levels in the patients with PADBS in the early stage and discuss the possible roles CA and ACTH in the pathogenesis of PADBS. It is a cross-sectional study. A group of patients with PADBS (n=10) was compared with a group of patients with severe brain injury (SBI) (n=33). A control group of healthy adults (n=25) was also included. Blood samples were obtained to measure levels of epinephrine (EPI), norepinephrine (NE), dopamine (DA), and ACTH as soon as the patients arrived at the neurosurgery department, which was done within 4h after trauma. Both SBI and PADBS groups of patients had higher levels of EPI, NE, DA, and ACTH than the control group. The PADBS group had significantly higher levels of EPI, NE, and ACTH than the SBI group. CA and ACTH levels are significantly increased in early stage PADBS. These results imply that CA and ACTH may play important roles in the pathogenesis of PADBS. To eliminate the effects of CA and ACTH at the early stage, and thereby protect the hypothalamus and brain stem, might be critical measures for treating patients with PADBS.

Systemic manifestations of traumatic brain injury

Traumatic brain injury (TBI) affects functioning of various organ systems in the absence of concomitant non-neurologic organ injury or systemic infection. The systemic manifestations of TBI can be mild or severe and can present in the acute phase or during the recovery phase. Non-neurologic organ dysfunction can manifest following mild TBI or severe TBI. The pathophysiology of systemic manifestations following TBI is multifactorial and involves an effect on the autonomic nervous system, involvement of the hypothalamic-pituitary axis, release of inflammatory mediators, and treatment modalities used for TBI. Endocrine dysfunction, electrolyte imbalance, and respiratory manifestations are common following TBI. The influence of TBI on systemic immune response, coagulation cascade, cardiovascular system, gastrointestinal system, and other systems is becoming more evident through animal studies and clinical trials. Systemic manifestations can independently act as risk factors for mortality and morbidity following TBI. Some conditions like neurogenic pulmonary edema and disseminated intravascular coagulation can adversely affect the outcome. Early recognition and treatment of systemic manifestations may improve the clinical outcome following TBI. Further studies are required especially in the field of neuroimmunology to establish the role of various biochemical cascades, not only in the pathophysiology of TBI but also in its systemic manifestations and outcome.

Traumatic brain injury: endocrine consequences in children and adults

Traumatic brain injury (TBI) is a common cause of death and disability in young adults with consequences ranging from physical disabilities to long-term cognitive, behavioral, psychological and social defects. Recent data suggest that pituitary hormone deficiency is not infrequent among TBI survivors; the prevalence of reported hypopituitarism following TBI varies widely among published studies. The most common cause of TBI is motor vehicle accidents, including pedestrian-car and bicycle car encounters, falls, child abuse, violence and sports injuries. Prevalence of hypopituitarism, from total to isolated pituitary deficiency, ranges from 5 to 90 %. The time interval between TBI and pituitary function evaluation is one of the major factors responsible for variations in the prevalence of hypopituitarism reported. Endocrine dysfunction after TBI in children and adolescents is common. Adolescence is a time of growth, freedom and adjustment, consequently TBI is also common in this group. Sports-related TBI is an important public health concern, but many cases are unrecognized and unreported. Sports that are associated with an increased risk of TBI include those involving contact and/or collisions such as boxing, football, soccer, ice hockey, rugby, and the martial arts, as well as high velocity sports such as cycling, motor racing, equestrian sports, skiing and roller skating. The aim of this paper is to summarize the best evidence of TBI as a cause of pituitary deficiency in children and adults.

Impact of head trauma on pituitary function

There have been in the past decade a growing number of studies relating head trauma to hypopituitarism. This condition may affect the rehabilitation process, and identification of such patients is therefore required. However, the widely different methods used so far for this purpose have provided inconsistent results. The incidence rate of hypopituitarism has probably been overestimated. This review focuses on the impact of head trauma on pituitary function, the diagnostic method, risk factors, and treatment options.

Cortisol and adrenocorticotropic hormone dynamics in the acute phase of subarachnoid haemorrhage

OBJECTIVE

An adequate response of hypothalamic-pituitary-adrenal (HPA) axis is important for survival and recovery after a severe disease. The hypothalamus and the pituitary glands are at risk of damage after subarachnoid haemorrhage (SAH). A better understanding of the hormonal changes would be valuable for optimising care in the acute phase of SAH.

PATIENTS

Fifty-five patients with spontaneous SAH were evaluated regarding morning concentrations of serum (S)-cortisol and P-adrenocorticotropic hormone (ACTH) 7 days after the bleeding. In a subgroup of 20 patients, the diurnal changes of S-cortisol and P-ACTH were studied and urine (U)-cortisol was measured. The relationships of hormone concentrations to clinical and radiological parameters and to outcome were assessed.

RESULTS

S-cortisol and P-ACTH were elevated the day of SAH. S-cortisol concentrations below reference range were uncommon. Early global cerebral oedema was associated with higher S-cortisol concentrations at admission and a worse World Federation of Neurological Surgeons (WFNS) and Reaction Level Scale 85 grade. Global cerebral oedema was shown to be a predictor of S-cortisol at admittance. Patients in better WFNS grade displayed higher U-cortisol. All patients showed diurnal variations of S-cortisol and P-ACTH. A reversed diurnal variation of S-cortisol was more frequently found in mechanically ventilated patients. Periods of suppressed P-ACTH associated with S-cortisol peaks occurred especially in periods of secondary brain ischaemia.

CONCLUSION

There was an HPA response acutely after SAH with an increase in P-ACTH and S-cortisol. Higher U-cortisol in patients in a better clinical grade may indicate a more robust response of the HPA system. Global cerebral oedema was associated with higher S-cortisol at admission and was a predictor of S-cortisol concentrations. Global cerebral oedema may be the result of the stress response initiated by the brain injury. Periods of suppressed P-ACTH occurred particularly in periods of brain ischaemia, indicating a possible connection between brain ischaemia and ACTH suppression.

Endocrine changes in brain death and transplantation

Following brain death (BD) many hormonal changes occur. These include an increase and then a fall in the levels of circulating catecholamines, reduced levels of anti-diuretic hormone and cortisol as well as alterations in the hypothalamic-pituitary thyroid axis consistent with the non-thyroidal illness syndrome. In an era when the numbers of potential recipients listed for transplantation are greater than the number of donors, with an increasing donor age, a detailed knowledge of the endocrine changes and pathophysiological consequences of these is essential to optimise the management of the brain-stem dead organ donor. There still remains significant debate as to whether hormone replacement therapy to correct the observed changes is beneficial.

Pituitary dysfunction following traumatic brain injury or subarachnoid haemorrhage - in "Endocrine Management in the Intensive Care Unit"

Traumatic brain injury and subarachnoid haemorrhage are important causes of morbidity and mortality in the developed world. There is a large body of evidence that demonstrates that both conditions may adversely affect pituitary function in both the acute and chronic phases of recovery. Diagnosis of hypopituitarism and accurate treatment of pituitary disorders offers the opportunity to improve mortality and outcome in both traumatic brain injury and subarachnoid haemorrhage. In this article, we will review the history and pathophysiology of pituitary function in the acute phase following traumatic brain injury and subarachnoid haemorrhage, and we will discuss in detail three key aspects of pituitary dysfunction which occur in the early course of TBI; acute cortisol deficiency, diabetes insipidus and SIAD.

Successful use of inhaled nitric oxide to decrease intracranial pressure in a patient with severe traumatic brain injury complicated by acute respiratory distress syndrome: a role for an anti-inflammatory mechanism?

Use of inhaled nitric oxide in humans with traumatic brain injury and acute respiratory distress syndrome has twice previously been reported to be beneficial. Here we report a third case. We propose that INO may decrease the inflammatory response in patients with increased intracranial pressure caused by traumatic brain injury accompanied by acute respiratory distress syndrome thereby contributing to improved outcomes.

Cushing's ulcer in traumatic brain injury

Traumatic brain injury (TBI) remains a complicated and urgent disease in our modernized cities. It becomes now a public health disease. We have got more and more patients in Neurosurgery Intensive Care Unit following motor vehicle accidents and others causes. TBI brings multiple disorders, from the primary injury to secondary injury. The body received the disturbances in the brain, in the hypothalamo-pituitary-adrenocortical (HPA) axis, in the gastric mucosa, in the immune and neuroendocrine systems. The mortality of TBI is more than 50 000 deaths / year, the third of the mortality of all injuries. Cushing ulcer is one of the severe complications of TBI and its mortality rate is more than 50%. Many studies have improved the management of TBI and the associated complications to give patients a better outcome. Furthers studies need to be done based on the similar methodology to clarify the different steps of the HPA axis and the neuroendocrine change associated. The aim of the present review is to assess the clinical and endocrinal features of hypopituitarism and stress ulcer following TBI.

The beneficial effects of inhaled nitric oxide in patients with severe traumatic brain injury complicated by acute respiratory distress syndrome: a hypothesis

Background

The Iraq war has vividly brought the problem of traumatic brain injury to the foreground. The costs of death and morbidity in lost wages, lost taxes, and rehabilitative costs, let alone the emotional costs, are enormous. Military personnel with traumatic brain injury and acute respiratory distress syndrome may represent a substantial problem. Each of these entities, in and of itself, may cause a massive inflammatory response. Both presenting in one patient can precipitate an overwhelming physiological scenario. Inhaled nitric oxide has recently been demonstrated to have anti-inflammatory effects beyond the pulmonary system, in addition to its ability to improve arterial oxygenation. Furthermore, it is virtually without side effects, and can easily be applied to combat casualties or to civilian casualties.

Presentation of hypothesis

Use of inhaled nitric oxide in patients with severe traumatic brain injury and acute respiratory distress syndrome will show a benefit through improved physiological parameters, a decrease in biochemical markers of inflammation and brain injury, thus leading to better outcomes.

Testing of hypothesis

A prospective, randomized, non-blinded clinical trial may be performed in which patients meeting the case definition could be entered into the study. The hypothesis may be confirmed by: (1) demonstrating an improvement in physiologic parameters, intracranial pressure, and brain oxygenation with inhaled nitric oxide use in severely head injured patients, and (2) demonstrating a decrease in biochemical serum markers in such patients; specifically, glial fibrillary acidic protein, inflammatory cytokines, and biomarkers of the hypothalamic-pituitary-adrenal axis, and (3) documentation of outcomes.

Implications of hypothesis

Inhaled nitric oxide therapy in traumatic brain injury patients with acute respiratory distress syndrome could result in increased numbers of lives saved, decreased patient morbidity, decreased hospital costs, decreased insurance carrier and government rehabilitation costs, increased tax revenue secondary to occupational rehabilitation, and families could still have their loved ones among them.

Hypopituitarism following traumatic brain injury (TBI)

Traumatic brain injury (TBI) is the commonest cause of death and disability in young adults living in industrialised countries. Recently, several studies have shown that hypopituitarism is a common complication of head trauma, with a prevalence of at least 25% among patients who were studied months or years following injury. This remarkably high frequency has changed the traditional concept of hypopituitarism being a rare complication of TBI, and suggests that most cases of posttraumatic hypopituitarism remain undiagnosed and untreated in clinical practice. It is therefore reasonable to infer that posttraumatic hypopituitarism may have an important contribution to the high physical and neuropsychiatric morbidity seen in patients with head injury. This article discusses the published reports on neuroendocrine dysfunction in TBI patients and the natural history of this disorder. The potential impact of posttraumatic hypopituitarism on recovery and rehabilitation after injury will also be examined, as well as the need for the identification, and appropriate and timely management of hormone deficiencies in order to reduce morbidity, aid recovery, and avoid the long-term complications of pituitary failure.

Relationship between plasma adrenocorticotropin hormone and intensive care unit survival in early traumatic brain injury

BACKGROUND

Hypothalamic pituitary adrenal response has been recently evaluated in patients with traumatic brain injury (TBI) with different results. Our objective was to study this response and its relationship with outcome in the early stage after TBI.

METHODS

We conducted a prospective observational clinical study in the intensive care unit of a tertiary level university hospital. The study included 50 consecutive patients who suffered isolated TBI. Intracranial pressure (ICP) was measured by an intraparenchymal probe. All patients were sedated and mechanically ventilated. Second-level measures were provided as per protocol, when needed. We measured plasma adrenocorticotropin hormone (ACTH) levels, as well as baseline and stimulated serum cortisol after a high-dose corticotrophin stimulation test, within 2 days after TBI for all patients.

RESULTS

Mean age was 36 +/- 18 (range 16-77) years. Forty-four (88%) were male. Median Glasgow Coma Scale score was 7. Mean ACTH was 15.4 +/- 19.8 pg/mL. Mean baseline cortisol was 14.8 +/- 9.0 microg/dL and mean stimulated cortisol was 27.1 +/- 7.3 microg/dL and 30.5 +/- 7.2 microg/dL at 30 and 60 minutes, respectively. Baseline and stimulated cortisol were not correlated with mortality. Logistic regression analysis revealed that, either plasma ACTH levels <9 pg/mL or lack of indication to provide second-level measures to control ICP were significant independent predictors of survival.

CONCLUSIONS

The presence of a low plasma ACTH concentration at an early stage of TBI and lack of indication to provide second-level measures to control ICP were associated with a higher intensive care unit survival.

One-year follow-up of patients with mild traumatic brain injury: occurrence of post-traumatic stress-related symptoms at follow-up and serum levels of cortisol, S-100B and neuron-specific enolase in acute phase

OBJECTIVE

To investigate serum levels of cortisol (a biochemical marker of stress), S-100B and neuron-specific enolase (two biochemical markers of brain tissue injury), in acute phase in mild traumatic brain injury patients and the occurrence of post-traumatic stress-related symptoms 1 year after the trauma.

METHODS

Blood samples were taken in patients (n = 88) on admission and approximately 7 hours later for analysis. Occurrence of post-traumatic stress-related symptoms was assessed for 69 patients using items from the Impact of Event Scale questionnaire (IES) at follow-up at 15 +/- 4 months after the injury.

RESULTS

Serum levels of cortisol were more increased in the first sample (cortisol/1, 628.9 +/- 308.9 nmol L-1) than in the second blood sample (cortisol/2, 398.2 +/- 219.4 nmol L-1). The difference between these samples was statistically significant (p < 0.001). Altogether 12 patients (17%) showed post-traumatic stress related symptoms at the time of the follow-up. Stepwise forward logistic regression analysis of symptoms and serum concentrations of markers revealed that only S-100B in the second sample was statistically significantly (p < 0.05) associated to symptoms (three symptoms of the avoidance sub-set of IES).

CONCLUSION

A major increase in serum concentrations of cortisol indicates that high stress levels were reached by the patients, in particular shortly ( approximately 3 hours) after the trauma. The association between the occurrence of post-traumatic stress related symptoms and serum levels of S-100B (generally considered as a biochemical marker of brain injury) seem to reflect the complexity of interactions between brain tissue injury and the ensemble of stress reactions.

Anterior pituitary dysfunction following traumatic brain injury (TBI)

Traumatic brain injury (TBI) is the commonest cause of death and disability in young adults living in industrialized countries. Several recent studies have convincingly shown that anterior hypopituitarism is a common complication of head trauma with a prevalence of at least 25% among long-term survivors. This is a much higher frequency than previously thought and suggests that most cases of post-traumatic hypopituitarism (PTHP) remain undiagnosed and untreated. These findings raise important questions about the potential contribution of PTHP to the high physical and neuropsychiatric morbidity seen in this group of patients. In this review, we examine the published reports on the neuroendocrine abnormalities in TBI patients and highlight new data that give novel insights into the natural history of this disorder. We discuss the potential contribution of PTHP to recovery and rehabilitation after injury and the need for the identification and the appropriate and timely management of hormone deficiencies to optimize patient recovery from head trauma, improve quality of life and avoid the long-term adverse consequences of untreated hypopituitarism.

Acute secondary adrenal insufficiency after traumatic brain injury: a prospective study

OBJECTIVE

To determine the prevalence, time course, clinical characteristics, and effect of adrenal insufficiency (AI) after traumatic brain injury (TBI).

DESIGN

Prospective intensive care unit-based cohort study.

SETTING

Three level 1 trauma centers.

PATIENTS

A total of 80 patients with moderate or severe TBI (Glasgow Coma Scale score, 3-13) and 41 trauma patients without TBI (Injury Severity Score, >15) enrolled between June 2002 and November 2003.

MEASUREMENTS

Serum cortisol and adrenocorticotropic hormone levels were drawn twice daily for up to 9 days postinjury; AI was defined as two consecutive cortisols of < or =15 microg/dL (25th percentile for extracranial trauma patients) or one cortisol of < 5 microg/dL. Principal outcome measures included: injury characteristics, hemodynamic data, usage of vasopressors, metabolic suppressive agents (high-dose pentobarbital and propofol), etomidate, and AI status.

MAIN RESULTS

AI occurred in 42 TBI patients (53%). Adrenocorticotropic hormone levels were lower at the time of AI (median, 18.9 vs. 36.1 pg/mL; p = .0001). Compared with patients without AI, those with AI were younger (p = .01), had higher injury severity (p = .02), had a higher frequency of early ischemic insults (hypotension, hypoxia, severe anemia) (p = .02), and were more likely to have received etomidate (p = .049). Over the acute postinjury period, patients with AI had lower trough mean arterial pressure (p = .001) and greater vasopressor use (p = .047). Mean arterial pressure was lower in the 8 hrs preceding a low (< or =15 microg/dL) cortisol level (p = .003). There was an inverse relationship between cortisol levels and vasopressor use (p = .0005) and between cortisol levels within 24 hrs of injury and etomidate use (p = .002). Use of high-dose propofol and pentobarbital was strongly associated with lower cortisol levels (p < .0001).

CONCLUSIONS

Approximately 50% of patients with moderate or severe TBI have at least transient AI. Younger age, greater injury severity, early ischemic insults, and the use of etomidate and metabolic suppressive agents are associated with AI. Because lower cortisol levels were associated with lower blood pressure and higher vasopressor use, consideration should be given to monitoring cortisol levels in intubated TBI patients, particularly those receiving high-dose pentobarbital or propofol. A randomized trial of stress-dose hydrocortisone in TBI patients with AI is underway.

Hypothalamic-pituitary dysfunction in critically ill patients with traumatic and nontraumatic brain injury

BACKGROUND

A significant number of studies have shown that critically ill patients with brain injury (BI) frequently exhibit abnormal pituitary hormonal responses during the immediate postinjury period.

DISCUSSION

The elucidation of endocrine alterations depends on the criteria used, the diagnostic tests applied, and the timing of testing in relation to BI. The pattern of the detected hormonal abnormalities shows considerable variability. Altered endocrine responses are due mostly to hypothalamic changes rather than to pituitary dysfunction. Several studies have examined the correlation between hormonal alterations and BI severity, but the results are inconsistent. Furthermore, it remains currently unclear whether and how pituitary abnormalities adversely affect the clinical course of BI patients during the period of critical illness. On the basis of current knowledge, with the exception of clinically significant relative adrenal deficiency and diabetes insipidus, the other endocrine alterations do not seem to require any therapeutic intervention in severely ill BI patients. It is also uncertain whether hormonal abnormalities detected in the early post-BI period persist for the rest of these patients' lives.

CONCLUSIONS

In view of current evidence indicating a high incidence of pituitary dysfunction even years following BI it is recommended that repetition of endocrine evaluation should be performed during the rehabilitation phase in all patients.

Hypothalamic-pituitary-adrenal axis dysfunction in critically ill patients with traumatic brain injury: incidence, pathophysiology, and relationship to vasopressor dependence and peripheral interleukin-6 levels

OBJECTIVE

To investigate hypothalamic-pituitary-adrenal axis function in patients requiring mechanical ventilation for traumatic brain injury and to assess the relation of hypothalamic-pituitary-adrenal axis abnormalities with vasopressor dependence and peripheral cytokine levels.

DESIGN

Prospective study.

SETTING

General intensive care unit in a university teaching hospital.

PATIENTS

Forty patients (33 men and 7 women) with moderate to severe traumatic brain injury (mean age, 37 +/- 16 yrs) were studied the day after termination of mechanical ventilation (7-60 days after trauma).

INTERVENTIONS

First, a morning blood sample was obtained to measure baseline cortisol, corticotropin, interleukin-6, and tumor necrosis factor alpha. Subsequently, 1 microg of synthetic corticotropin was injected intravenously, and 30 mins later, a second blood sample was drawn to determine stimulated plasma cortisol. Based on data derived from healthy volunteers, patients having stimulated cortisol levels <18 microg/dL were defined as nonresponders to the low-dose stimulation test. Thirty-one patients underwent also a human corticotropin releasing hormone test.

MEASUREMENTS AND MAIN RESULTS

In traumatic brain injury patients, mean baseline and low-dose stimulation test-stimulated cortisol levels were 17.2 +/- 5.4 microg/dL and 24.0 +/- 6.6 microg/dL, respectively. The median increment in cortisol was 5.9 microg/dL. Basal corticotropin levels ranged from 3.9 to 118.5 pg/mL. Six of the 40 patients (15%) failed the low-dose stimulation test. The human corticotropin releasing hormone test (performed in 26 responders and five nonresponders) revealed diminished cortisol release only in the low-dose stimulation test nonresponder patients. Corticotropin responses to corticotropin releasing hormone were consistent with both primary (three patients) and/or secondary (two patients) adrenal dysfunction. In retrospect, nonresponders to the low-dose stimulation test more frequently required vasopressors (6/6 [100%] vs. 16/34 [47%]; p =.02) and for a longer time interval (median, 0 vs. 293 hrs; p =.006) compared with responders. Furthermore, nonresponders had higher interleukin-6 levels compared with responders (56.03 vs. 28.04 pg/mL; p =.01), whereas tumor necrosis factor alpha concentrations were similar in the two groups (2.42 vs. 1.55 pg/mL; p =.53).

CONCLUSIONS

Adrenal cortisol secretion after dynamic stimulation is deficient in a subset of critically ill patients with moderate to severe head injury. This disorder is associated with prior vasopressor dependency and higher interleukin-6 levels.

Effects of early and late intravenous norepinephrine infusion on cerebral perfusion, microcirculation, brain-tissue oxygenation, and edema formation in brain-injured rats

OBJECTIVES

Reduction of cerebral perfusion during the early phase after traumatic brain injury is followed by a later phase of normal to increased perfusion. Thus, pharmacologically elevating mean arterial blood pressure with the aim of improving cerebral perfusion may exert different time-dependent effects on cortical perfusion, microcirculation, tissue oxygenation and brain edema formation after traumatic brain injury.

DESIGN

Randomized, placebo-controlled trial.

SETTING

Experimental laboratory at a university hospital.

SUBJECTS

A total of 37 male Sprague-Dawley rats subjected to a focal cortical contusion.

INTERVENTIONS

At 4 or 24 hrs after focal traumatic brain injury, mean arterial blood pressure was increased to 120 mm Hg for 90 mins by infusing norepinephrine. In rats receiving physiologic saline, mean arterial blood pressure remained unchanged. In the first series, pericontusional cortical perfusion was measured using the laser Doppler flowmetry scanning technique before injury and before, during, and after the infusion period. In a second series, intracranial and cerebral perfusion pressure and intraparenchymal perfusion and tissue oxygen measured within the contused and pericontusional cortex were recorded continuously before, during, and after norepinephrine infusion. Changes in cortical microcirculation were investigated by orthogonal polarization spectral imaging. At the end of each experiment, hemispheric swelling and water content were determined gravimetrically.

MEASUREMENTS AND MAIN RESULTS

At 4 and 24 hrs after traumatic brain injury, intravenous norepinephrine significantly increased pericontusional cortical perfusion, which was also reflected by an increase in diameters and flow velocities of pericontusional arterioles and venules. Cerebral perfusion pressure and intraparenchymal perfusion and tissue oxygen were significantly increased during norepinephrine infusion at 4 and 24 hrs. Hemispheric swelling and water content showed no difference between the groups.

CONCLUSIONS

After cortical impact injury, early and late intravenous norepinephrine infusion pressure-dependently increased cerebral perfusion and tissue oxygenation without aggravating or reducing brain edema formation. Future studies are warranted to determine long-term changes of short and prolonged norepinephrine-induced increases in mean arterial blood pressure and cerebral perfusion pressure.

Impact of a unilateral brain lesion on cortisol secretion and emotional state: anterior/posterior dissociation in humans

The main goal of this study was to evaluate whether a unilateral brain lesion in a human population is associated with a modification of the circadian cortisol secretion profile, and/or patient's emotional state. The second goal of this study was to assess whether there would be differences in both the pattern of cortisol secretion and emotional state in brain-damaged patients as a function of side of lesion, and localization (anterior vs posterior) of lesion. Eight patients with a left cortical lesion, six patients with a right cortical lesion, four patients with basal ganglia lesions (2 left and 2 right) and ten healthy volunteers were evaluated daily on measures of salivary cortisol levels and subjective feelings of joy and sadness at 0700, 1200, 1600 and 1900 hours over a 15-day period. Patients with cortical brain lesions presented higher cortisol levels and higher scores of sadness at the time of the morning peak (7:00 am), when compared to healthy volunteers and patients with basal ganglia lesions. Laterality of the lesion was not related to cortisol secretion, but frontal damage (anterior lesion) was associated with higher cortisol levels at the time of the morning peak (7:00 am) when compared to more posterior damage. There was no significant correlation between basal circulating levels of cortisol and emotional states in patients and healthy subjects. The results of this study suggest that hypothalamic-pituitary-adrenal (HPA) axis dysregulation is associated with unilateral injury particularly in frontal areas. These results, obtained in a human population, go along with recent animal studies reporting an implication of frontal regions in HPA activity.

Role of epinephrine in acute stress

This article presents the likely pathway of stimuli generated by the recognition of high-intensity stressors to ultimately produce a fight-or-flight response. A key element is the recognition that psychological stressors that do not directly alter the internal environment represent the most important etiology of a fight-or-flight response. Adrenomedullary secretion is a critical component of that response; impromptu stimulation of the adrenal medulla can produce plasma epinephrine concentrations greater than 10,000 pg/mL. When these plasma levels reach the hypothalamus to act on the CNS, the result is facilitation of the decision making, and decision execution processes (fight-or-flight), and perhaps further sympathetic stimulation and vasopressin release. Subjects with underlying cardiovascular and/or metabolic pathology may be particularly susceptible to potentially lethal reactions to this neuroendocrine response. Additionally, since this biological reaction may be triggered by sudden changes in the social environment, the coordinated actions of epinephrine, sympathetic stimulation and vasopressin must be directed at not only optimizing the chances for survival, but also at attaining maximal preservation of the individual environmental and social domains.

The hypothalamo-pituitary-adrenal axis response to experimental traumatic brain injury

Alterations in the hypothalamo-pituitary-adrenal (HPA) axis following traumatic brain injury have not been documented in detail. We used fluid percussion injury (FPI) to evaluate the early changes in components of the HPA axis following experimental traumatic brain injury. Wistar rats were sacrificed at 2 or 4 h following sham or FPI surgery. In situ hybridization histochemistry was used to determine the expression of mRNAs of corticotrophin releasing hormone (CRH) and arginine vasopressin (AVP) in the hypothalamus and pro-opiomelanocortin (POMC) in the pituitary. A group of animals undergoing no surgery were used as control. Repeated blood sampling from an indwelling catheter demonstrated that plasma corticosterone (CORT) levels peaked 30 min following surgery in sham and FPI animals but there was no significant difference in CORT concentration between these groups at any time. Pituitary POMC expression was increased following sham and FPI surgery (compared with control non-operated animals) but with no significant difference between the two groups undergoing surgery. Hypothalamic CRH mRNA expression was significantly higher in animals undergoing FPI compared with sham surgery. Hypothalamic AVP mRNA expression was not significantly increased when compared with control nonoperated animals. These data indicate that the anaesthesia and/or surgery associated with FPI or sham surgery induces a generalised activation of the HPA axis. The selective increase in CRH mRNA in animals undergoing FPI may be due to specific effects of traumatic brain injury rather than a general stress response and may suggest an additional neurotransmitter role for CRH following head injury. The absence of an AVP response suggests that the effects of FPI may be mediated through the CRH-alone-containing subpopulation of neurons.

Traumatic brain injury reduces hippocampal alpha7 nicotinic cholinergic receptor binding

Changes in the expression of central nervous system (CNS) neurotransmitter receptors may contribute to behavioral and physiological deficits that occur following traumatic brain injury (TBI). Studies investigating the neurochemical basis for the protracted cognitive dysfunction that follows TBI have focused in part on cholinergic mechanisms. The present study compared the effects of mild and moderate cortical contusion injury (CCI) on the density of cholinergic receptor subtypes, NMDA-type glutamate receptors, and calcium channel expression. Quantitative autoradiography was used to determine the effects of CCI on receptor expression, 48 h following injury. The most robust and consistent change in receptor binding was in the density of alpha7 nicotinic receptors as determined by alpha-[125I]-bungarotoxin (BTX) binding. Bilateral deficits in BTX binding were present following both mild and moderate levels of injury. In contrast, changes in the density of alpha3/alpha4 nAChr's, muscarinic AChr's, NMDA-type glutamate receptors, and L-type calcium channel expression were more regionally restricted and lower in magnitude, as compared to changes in BTX binding. The high calcium permeability of the alpha7 nAChr may be related to the extensive decrease in BTX binding that occurs following TBI.

The neglected prehospital phase of head injury: apnea and catecholamine surge

The prehospital phase of head injury, also called the critical phase, consists of trauma-induced apnea and stress catecholamine release. This immediate period after head injury remains poorly summarized in the literature and essentially ignored with respect to treatment. A MEDLINE search of the literature on apneustic response and catecholamine surge after head injury and a review of literature from my acquired references revealed 116 references (from more than 600) that were pertinent. Apnea induced by head injury produces hypoxia, hypercarbia, and subsequent cardiac failure and hypotension, which, along with substantially elevated catecholamine values, promote secondary mechanisms of organ injury. Treatment for this immediate period after head injury requires a rapid response to the scene of trauma and development of treatment options that can be instituted at the scene of injury.

Does splanchnic ischemia occur in isolated neurotrauma? A prospective observational study

OBJECTIVE

To characterize the incidence and severity of splanchnic ischemia, as defined by gastric tonometry, in patients with isolated severe head injury and to examine the relationship between cerebral hemodynamics and splanchnic ischemia.

DESIGN

Prospective observational study.

SETTING

Neurosurgical intensive care unit in a tertiary referral center.

PATIENTS

Ten patients with severe neurotrauma.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The mean arterial pressure, intracranial pressure, and gastric mucosal P(CO2) measurements were recorded at 15-min intervals. Intramucosal pH was calculated every 3 hrs. All patients received stress ulcer prophylaxis. Nine patients received noradrenaline infusions to maintain a target cerebral perfusion pressure of 70 mm Hg. The mean baseline gastric mucosal P(CO2) and intramucosal pH were 38+/-10 torr and 7.38+/-0.1 pH units, respectively. Nine patients manifested low intramucosal pH during the study period. Gastric mucosal P(CO2) values ranged from 36 to 132 torr. Intramucosal pH measurements ranged from 6.9 to 7.47. The mucosal gap ranged from -12 to +93 torr (mean +/- SD, 17+/-17 torr). The pH gap ranged from -0.1 to +0.54 pH units (mean +/- SD, 0.14+/-0.11 pH units). There was no statistically significant relationship between cerebral hemodynamics, the use of inotropes, and gastric mucosal P(CO2), or intramucosal pH.

CONCLUSIONS

Splanchnic ischemia (intramucosal pH, <7.3) occurs commonly in isolated neurotrauma, with a statistically nonsignificant trend toward development of mucosal ischemia with decreased cerebral perfusion.

Regulation of the hypothalamic-pituitary-adrenal axis by cytokines: actions and mechanisms of action

Glucocorticoids are hormone products of the adrenal gland, which have long been recognized to have a profound impact on immunologic processes. The communication between immune and neuroendocrine systems is, however, bidirectional. The endocrine and immune systems share a common "chemical language," with both systems possessing ligands and receptors of "classical" hormones and immunoregulatory mediators. Studies in the early to mid 1980s demonstrated that monocyte-derived or recombinant interleukin-1 (IL-1) causes secretion of hormones of the hypothalamic-pituitary-adrenal (HPA) axis, establishing that immunoregulators, known as cytokines, play a pivotal role in this bidirectional communication between the immune and neuroendocrine systems. The subsequent 10-15 years have witnessed demonstrations that numerous members of several cytokine families increase the secretory activity of the HPA axis. Because this neuroendocrine action of cytokines is mediated primarily at the level of the central nervous system, studies investigating the mechanisms of HPA activation produced by cytokines take on a more broad significance, with findings relevant to the more fundamental question of how cytokines signal the brain. This article reviews published findings that have documented which cytokines have been shown to influence hormone secretion from the HPA axis, determined under what physiological/pathophysiological circumstances endogenous cytokines regulate HPA axis activity, established the possible sites of cytokine action on HPA axis hormone secretion, and identified the potential neuroanatomic and pharmacological mechanisms by which cytokines signal the neuroendocrine hypothalamus.