Cytokines and metabolic dysfunction after severe head injury

Temporal profile of cerebrospinal fluid, plasma, and brain interleukin-6 after normothermic fluid-percussion brain injury: effect of secondary hypoxia

Interleukin-6 (IL-6) is a proinflammatory cytokine that may play multiple roles in the pathogenesis of traumatic brain injury (TBI). The present study determined time-dependent changes in IL-6 concentrations in vulnerable brain regions, cerebrospinal fluid (CSF) samples, and plasma after normothermic TBI. Because secondary insults are common in head injured patients, we also assessed the consequences of a post-traumatic secondary hypoxic insult on this pleiotropic cytokine. Male Sprague-Dawley rats were intubated, anesthetized, and underwent a moderate parasagittal fluid-percussion brain injury (1.8-2.1 atm, 37°C) followed by either 30 minutes of normoxic or hypoxic (pO₂ = 30-40 mmHg) gas levels. Rats were sacrificed 3, 6, or 24 hours after TBI or shamoperated procedures. Brain samples, including the ipsilateral cerebral cortex and hippocampus were dissected and analyzed. Plasma and CSF samples were collected at similar times and stored at -80°C until analysis. IL-6 levels were significantly increased ( p < 0.05) at 3, 6, and 24 hours in the cerebral cortex and at 6 hours in the hippocampus after TBI. IL-6 levels in the TBI normoxic group for both structures returned to control levels by 24 hours. Plasma levels of IL-6 were elevated at all time points, while CSF levels were high at 3 and 6 hours, but normalized by 24 hours. Post-traumatic hypoxia led to significantly elevated ( p < 0.05) IL-6 protein levels in the cerebral cortex at 24 hours compared to sham-operated controls. These findings demonstrate that moderate TBI leads to an early increase in IL-6 brain, plasma, and CSF protein levels. Secondary post-traumatic hypoxia, a common secondary injury mechanism, led to prolonged elevations in plasma IL-6 levels that may participate in the pathophysiology of this complicated TBI model.

Estimation of renal function in the intensive care unit: the covert concepts brought to light

Frantic efforts have been made up to this date to derive consensus for estimating renal function in critically ill patients, only to open the Pandora's box. This article tries to explore the various methods available to date, the newer concepts, and the uncared issues that may still prove to be useful in estimating renal function in intensive care unit patients. The concept of augmented renal clearance, which is frequently encountered in critically ill patients, should always be taken into account, as correct therapeutic dosage of drugs sounds vital which in turn depends on correctly calculated glomerular filtration rate. Serum creatinine and creatinine-based formulae have their own demerits that are well known and established. While Cockcroft-Gault and 4-variable modification of diet in renal diseases formulae are highly inadequate in the intensive care setup for estimating glomerular filtration rate, employing isotopic methods is impractical and cumbersome. The 6-variable modification of diet in renal diseases formula fairs better as it takes into account the serum albumin and blood urea nitrogen, too. Jelliffe's and modified Jelliffe's equations take into account the rate of creatinine production and volume of distribution which in turn fluctuates heavily in a critically ill patient. Twenty-four-hour and timed creatinine clearances offer values close to reality although not accurate and cannot provide immediate results. Cystatin C is a novel agent that offers a sure promise as it is least influenced by factors that affect serum creatinine to a major extent. Aminoglycoside clearance, although still in the dark area, may prove a simple yet precise way of estimating glomerular filtration rate in those patients in whom these drugs are therapeutically employed. Optic ratiometric method has emerged as the most sophisticated one in glomerular filtration rate estimation in critically ill patients.

Novel therapeutic strategies for traumatic brain injury: acute antioxidant reinforcement

Traumatic brain injury (TBI) is the most important cause of disability in individuals under the age of 45 years and thus represents a significant social and economic burden. Evidence strongly suggests that oxidative stress is a cornerstone event leading to and propagating secondary injury mechanisms such as excitotoxicity, mitochondrial dysfunction, apoptosis, autophagy, brain edema, and inflammation. TBI has defied conventional approaches to diagnosis and therapy development because of its heterogeneity and complexity. Therefore, it is necessary to explore alternative approaches to therapy development for TBI. The aim of this review is to present a therapeutic approach for TBI, taking into account the evidence supporting the role for oxidative stress in the pathophysiological processes of secondary brain injury. The role of agents such as mitochondria-targeted antioxidants (melatonin and new mitochondria-targeted antioxidants), nicotinamide adenine dinucleotide phosphate (NADPH) inhibitors (antioxidant vitamins and apocynin), and other compounds having mainly antioxidant properties (hydrogen-rich saline, sulforaphane, U-83836E, omega-3, and polyphenols) is covered. The rationale for innovative antioxidant therapies based on current knowledge and particularly the most recent studies regarding this field is discussed. Particular considerations and translational potential of new TBI treatments are examined and a novel therapeutic proposal for TBI is presented.

Effect of the systemic administration of methylprednisolone on the lungs of brain-dead donor rats undergoing pulmonary transplantation

OBJECTIVE

Most lung transplants are obtained from brain-dead donors. The physiopathology of brain death involves hemodynamics, the sympathetic nervous system, and inflammatory mechanisms. Administering methylprednisolone 60 min after inducing brain death in rats has been shown to modulate pulmonary inflammatory activity. Our objective was to evaluate the effects of methylprednisolone on transplanted rat lungs from donors treated 60 min after brain death.

METHODS

Twelve Wistar rats were anesthetized, and brain death was induced. They were randomly divided into two groups (n=6), namely a control group, which was administered saline solution, and a methylprednisolone group, which received the drug 60 min after the induction of brain death. All of the animals were observed and ventilated for 2 h prior to being submitted to lung transplantation. We evaluated the hemodynamic and blood gas parameters, histological score, lung tissue levels of thiobarbituric acid-reactive substances, level of superoxide dismutase, level of tumor necrosis factor-alpha, and level of interleukin-1 beta.

RESULTS

After transplantation, a significant reduction in the levels of tumor necrosis factor-alpha and IL-1β was observed in the group that received methylprednisolone (p=0.0084 and p=0.0155, respectively). There were no significant differences in tumor necrosis factor-alpha and superoxide dismutase levels between the control and methylprednisolone groups (p=0.2644 and p=0.7461, respectively). There were no significant differences in the blood gas parameters, hemodynamics, and histological alterations between the groups.

CONCLUSION

The administration of methylprednisolone after brain death in donor rats reduces inflammatory activity in transplanted lungs but has no influence on parameters related to oxidative stress.

Increased interleukin 1 and tumor necrosis factor alpha levels after thyroid surgery

OBJECTIVE

The aim of this study was to consider levels of the proinflammatory cytokines IL-1 and TNFα after thyroid surgery.

MATERIAL AND METHODS

A total of 200 patients who underwent total thyroidectomy enrolled in this study. Drain fluid samples were taken. IL-1 and TNFα results and their relationship with other factors were analyzed.

RESULTS

There was a positive correlation between IL-1 and hyperthyroidism (rs=0.614, p<0.001), operative time (rs=0.770, p<0.001), and excised thyroid volume (rs=0.829, p<0.001). Moreover, there was a positive correlation between TNFα and hyperthyroidism (rs=0.430, p<0.001), operative time (rs=0.392, p<0.001), and excised thyroid volume (rs=0.398, p<0.001).

CONCLUSION

The results of this study showed us that the parameters related to increased proinflammatory cytokine levels after thyroid surgery were hyperthyroidism, operative time, and excised thyroid volume, but this increase did not show us any clinical outcomes related to these parameters.

Acute respiratory distress syndrome after spontaneous intracerebral hemorrhage*

OBJECTIVES

Acute respiratory distress syndrome develops commonly in critically ill patients in response to an injurious stimulus. The prevalence and risk factors for development of acute respiratory distress syndrome after spontaneous intracerebral hemorrhage have not been reported. We sought to determine the prevalence of acute respiratory distress syndrome after intracerebral hemorrhage, characterize risk factors for its development, and assess its impact on patient outcomes.

DESIGN

Retrospective cohort study at two academic centers.

PATIENTS

We included consecutive patients presenting from June 1, 2000, to November 1, 2010, with intracerebral hemorrhage requiring mechanical ventilation. We excluded patients with age less than 18 years, intracerebral hemorrhage secondary to trauma, tumor, ischemic stroke, or structural lesion; if they required intubation only during surgery; if they were admitted for comfort measures; or for a history of immunodeficiency.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Data were collected both prospectively as part of an ongoing cohort study and by retrospective chart review. Of 1,665 patients identified by database query, 697 met inclusion criteria. The prevalence of acute respiratory distress syndrome was 27%. In unadjusted analysis, high tidal volume ventilation was associated with an increased risk of acute respiratory distress syndrome (hazard ratio, 1.79 [95% CI, 1.13-2.83]), as were male sex, RBC and plasma transfusion, higher fluid balance, obesity, hypoxemia, acidosis, tobacco use, emergent hematoma evacuation, and vasopressor dependence. In multivariable modeling, high tidal volume ventilation was the strongest risk factor for acute respiratory distress syndrome development (hazard ratio, 1.74 [95% CI, 1.08-2.81]) and for inhospital mortality (hazard ratio, 2.52 [95% CI, 1.46-4.34]).

CONCLUSIONS

Development of acute respiratory distress syndrome is common after intubation for intracerebral hemorrhage. Modifiable risk factors, including high tidal volume ventilation, are associated with its development and in-patient mortality.

Oxidative burst of circulating neutrophils following traumatic brain injury in human

Besides secondary injury at the lesional site, Traumatic brain injury (TBI) can cause a systemic inflammatory response, which may cause damage to initially unaffected organs and potentially further exacerbate the original injury. Here we investigated plasma levels of important inflammatory mediators, oxidative activity of circulating leukocytes, particularly focusing on neutrophils, from TBI subjects and control subjects with general trauma from 6 hours to 2 weeks following injury, comparing with values from uninjured subjects. We observed increased plasma level of inflammatory cytokines/molecules TNF-α, IL-6 and CRP, dramatically increased circulating leukocyte counts and elevated expression of TNF-α and iNOS in circulating leukocytes from TBI patients, which suggests a systemic inflammatory response following TBI. Our data further showed increased free radical production in leukocyte homogenates and elevated expression of key oxidative enzymes iNOS, COX-2 and NADPH oxidase (gp91^phox) in circulating leukocytes, indicating an intense induction of oxidative burst following TBI, which is significantly greater than that in control subjects with general trauma. Furthermore, flow cytometry assay proved neutrophils as the largest population in circulation after TBI and showed significantly up-regulated oxidative activity and suppressed phagocytosis rate for circulating neutrophils following brain trauma. It suggests that the highly activated neutrophils might play an important role in the secondary damage, even outside the injured brain. Taken together, the potent systemic inflammatory response induced by TBI, especially the intensively increase oxidative activity of circulating leukocytes, mainly neutrophils, may lead to a systemic damage, dysfunction/damage of bystander tissues/organs and even further exacerbate secondary local damage. Controlling these pathophysiological processes may be a promising therapeutic strategy and will protect unaffected organs and the injured brain from the secondary damage.

Hypothermia reduces toll-like receptor 3-activated microglial interferon-β and nitric oxide production

Therapeutic hypothermia protects neurons after injury to the central nervous system (CNS). Microglia express toll-like receptors (TLRs) that play significant roles in the pathogenesis of sterile CNS injury. To elucidate the possible mechanisms involved in the neuroprotective effect of therapeutic hypothermia, we examined the effects of hypothermic culture on TLR3-activated microglial release of interferon (IFN)- β and nitric oxide (NO), which are known to be associated with neuronal cell death. When rat or mouse microglia were cultured under conditions of hypothermia (33°C) and normothermia (37°C) with a TLR3 agonist, polyinosinic-polycytidylic acid, the production of IFN- β and NO in TLR3-activated microglia at 48 h was decreased by hypothermia compared with that by normothermia. In addition, exposure to recombinant IFN- β and sodium nitroprusside, an NO donor, caused death of rat neuronal pheochromocytoma PC12 cells in a concentration-dependent manner after 24 h. Taken together, these results suggest that the attenuation of microglial production of IFN- β and NO by therapeutic hypothermia leads to the inhibition of neuronal cell death.

Use of biomarkers for diagnosis and management of traumatic brain injury patients

BACKGROUND

Advances in the understanding of human biochemistry and physiology have provided insight into new pathways by which we can understand traumatic brain injury (TBI). Increased sophistication of laboratory techniques and developments in the field of proteomics has led to the discovery and rapid detection of new biomarkers not previously available.

OBJECTIVE

To review recent advances in biomarker research for traumatic brain injury, describe the features of the ideal biomarker and to explore the potential role of these biomarkers in improving clinical management of brain injured patients.

METHODS

Through a literature review of recent research on TBI biomarkers and through experience with TBI research, important elements of biomarker development are described together with potential applications to patient care.

CONCLUSIONS

TBI biomarkers could have a significant impact on patient care by assisting in the diagnosis, risk stratification and management of TBI. Biomarkers could provide major opportunities for the conduct of clinical research, including confirmation of injury mechanism(s) and drug target identification. Continuing studies by the authors' group are now being conducted to elucidate more fully the relationships between new biomarkers and severity of injury and clinical outcomes in all severities of TBI patients.

Temperature-related effects of adenosine triphosphate-activated microglia on pro-inflammatory factors

BACKGROUND

Therapeutic hypothermia protects neurons after severe brain injury. Activated microglia produce several neurotoxic factors, such as pro-inflammatory cytokines and nitric oxide (NO), during neuron destruction. Hence, suppression of microglial release of these factors is thought to contribute partly to the neuroprotective effects of hypothermia. After brain insults, adenosine triphosphate (ATP) is released from injured cells and activates microglia. Here, we examined the acute effects of temperature on ATP-activated microglial production of inflammatory factors, and the possible involvement of p38 mitogen-activated protein kinase (p38) underlying such effects.

METHODS

Microglia were cultured with ATP at 33, 37, and 39°C, or with ATP in the presence of a p38 inhibitor, SB203580, at 37°C. Cytokine and NO levels, and p38 activation were measured.

RESULTS

Compared to 37°C, TNF-α was reduced at 33°C and augmented at 39°C for 1.5 h. IL-6 was reduced at 33°C for 6 h. NO was reduced at 33°C, but augmented at 39°C for 6 h. p38 was reduced at 33°C for 1 min. SB203580 inhibited ATP-induced TNF-α, IL-6, and NO production.

CONCLUSION

Lowering temperature rapidly reduced p38 activation and the subsequent p38-regulated production of pro-inflammatory cytokines and NO in ATP-activated microglia, suggesting that attenuation of early phase inflammatory responses via suppression of p38 in microglia is one possible neuroprotective mechanism of therapeutic hypothermia. Temperature elevation increased TNF-α and NO production in these cells. These temperature-dependent changes imply that monitoring of TNF-α and NO in the cerebrospinal fluid during the early phase might be useful as biomarkers for responses to therapeutic hypothermia and hyperthermia.

Pulmonary complications in patients with severe brain injury

Pulmonary complications are prevalent in the critically ill neurological population. Respiratory failure, pneumonia, acute lung injury and the acute respiratory distress syndrome (ALI/ARDS), pulmonary edema, pulmonary contusions and pneumo/hemothorax, and pulmonary embolism are frequently encountered in the setting of severe brain injury. Direct brain injury, depressed level of consciousness and inability to protect the airway, disruption of natural defense barriers, decreased mobility, and secondary neurological insults inherent to severe brain injury are the main cause of pulmonary complications in critically ill neurological patients. Prevention strategies and current and future therapies need to be implemented to avoid and treat the development of these life-threatening medical complications.

A review of neuroprotection pharmacology and therapies in patients with acute traumatic brain injury

Traumatic brain injury (TBI) affects 1.6 million Americans annually. The injury severity impacts the overall outcome and likelihood for survival. Current treatment of acute TBI includes surgical intervention and supportive care therapies. Treatment of elevated intracranial pressure and optimizing cerebral perfusion are cornerstones of current therapy. These approaches do not directly address the secondary neurological sequelae that lead to continued brain injury after TBI. Depending on injury severity, a complex cascade of processes are activated and generate continued endogenous changes affecting cellular systems and overall outcome from the initial insult to the brain. Homeostatic cellular processes governing calcium influx, mitochondrial function, membrane stability, redox balance, blood flow and cytoskeletal structure often become dysfunctional after TBI. Interruption of this cascade has been the target of numerous pharmacotherapeutic agents investigated over the last two decades. Many agents such as selfotel, pegorgotein (PEG-SOD), magnesium, deltibant and dexanabinol were ineffective in clinical trials. While progesterone and ciclosporin have shown promise in phase II studies, success in larger phase III, randomized, multicentre, clinical trials is pending. Consequently, no neuroprotective treatment options currently exist that improve neurological outcome after TBI. Investigations to date have extended understanding of the injury mechanisms and sites for intervention. Examination of novel strategies addressing both pathological and pharmacological factors affecting outcome, employing novel trial design methods and utilizing biomarkers validated to be reflective of the prognosis for TBI will facilitate progress in overcoming the obstacles identified from previous clinical trials.

The systemic response to brain injury and disease

The idea that the brain is immunologically privileged and displays an atypical leukocyte recruitment profile following injury has influenced our ideas about how signals might be carried between brain and the periphery. For many, this has encouraged a cerebrocentric view of immunological responses to CNS injury, with little reference to the potential contribution from other organs. However, it is clear that bidirectional pathways between the brain and the peripheral immune system are important in the pathogenesis of CNS disease. In recent years, we have begun to understand the signals that are carried to the periphery and discovered new functions for known chemokines, made by the liver in response to brain injury, as important regulators of the CNS inflammatory response.

Severe traumatic head injury affects systemic cytokine expression

BACKGROUND

The neuroimmunologic effect of traumatic head injury remains ill-defined. This study aimed to characterize systemic cytokine profiles among traumatically injured patients to assess the effect of traumatic head injury on the systemic inflammatory response.

STUDY DESIGN

For 5 years, 1,022 patients were evaluated from a multi-institutional Trauma Immunomodulatory Database. Patients were stratified by presence of severe head injury (SHI; head Injury Severity Score ≥4, n = 335) vs nonsevere head injury (NHI; head Injury Severity Score ≤3, n = 687). Systemic cytokine expression was quantified by ELISA within 72 hours of admission. Patient factors, outcomes, and cytokine profiles were compared by univariate analyses.

RESULTS

SHI patients were more severely injured with higher mortality, despite similar ICU infection and ventilator-associated pneumonia rates. Expression of early proinflammatory cytokines, interleukin-6 (p < 0.001) and tumor necrosis factor-α (p = 0.02), was higher among NHI patients, and expression of immunomodulatory cytokines, interferon-γ (p = 0.01) and interleukin-12 (p = 0.003), was higher in SHI patients. High tumor necrosis factor-α levels in NHI patients were associated with mortality (p = 0.01), increased mechanical ventilation (p = 0.02), and development of ventilator-associated pneumonia (p = 0.01). Alternatively, among SHI patients, high interleukin-2 levels were associated with survival, decreased mechanical ventilation, and absence of ventilator-associated pneumonia.

CONCLUSIONS

The presence of severe traumatic head injury significantly alters systemic cytokine expression and exerts an immunomodulatory effect. Early recognition of these profiles can allow for targeted intervention to reduce patient morbidity and mortality.

The systemic inflammatory response after spinal cord injury in the rat is decreased by α4β1 integrin blockade

Abstract The systemic inflammatory response syndrome (SIRS) follows spinal cord injury (SCI) and causes damage to the lungs, kidney, and liver due to an influx of inflammatory cells from the circulation. After SCI in rats, the SIRS develops within 12 h and is sustained for at least 3 days. We have previously shown that blockade of CD11d/CD18 integrin reduces inflammation-driven secondary damage to the spinal cord. This treatment reduces the SIRS after SCI. In another study we found that blockade of α4β1 integrin limited secondary cord damage more effectively than blockade of CD11d/CD18. Therefore we considered it important to assess the effects of anti-α4β1 treatment on the SIRS in the lung, kidney, and liver after SCI. An anti-α4 antibody was given IV at 2 h after SCI at the fourth thoracic segment and the effects on the organs were evaluated at 24 h post-injury. The migration of neutrophils into the lungs and liver was markedly reduced and all three organs contained fewer macrophages. In the lungs and liver, the activation of the oxidative enzymes myeloperoxidase (MPO), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and gp91(phox), the production of free radicals, lipid peroxidation, and cell death were substantially and similarly reduced. Treatment effects were less robust in the kidney. Overall, the efficacy of the anti-α4β1 treatment did not differ greatly from that of the anti-CD11d antibody, although details of the results differed. The SIRS after SCI impedes recovery, and attenuation of the SIRS with an anti-integrin treatment is an important, clinically-relevant finding.

Metallothionein (MT) -I and MT-II expression are induced and cause zinc sequestration in the liver after brain injury

Experiments with transgenic over-expressing, and null mutant mice have determined that metallothionein-I and -II (MT-I/II) are protective after brain injury. MT-I/II is primarily a zinc-binding protein and it is not known how it provides neuroprotection to the injured brain or where MT-I/II acts to have its effects. MT-I/II is often expressed in the liver under stressful conditions but to date, measurement of MT-I/II expression after brain injury has focused primarily on the injured brain itself. In the present study we measured MT-I/II expression in the liver of mice after cryolesion brain injury by quantitative reverse-transcriptase PCR (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) with the UC1MT antibody. Displacement curves constructed using MT-I/II knockout (MT-I/II(-/-)) mouse tissues were used to validate the ELISA. Hepatic MT-I and MT-II mRNA levels were significantly increased within 24 hours of brain injury but hepatic MT-I/II protein levels were not significantly increased until 3 days post injury (DPI) and were maximal at the end of the experimental period, 7 DPI. Hepatic zinc content was measured by atomic absorption spectroscopy and was found to decrease at 1 and 3 DPI but returned to normal by 7DPI. Zinc in the livers of MT-I/II(-/-) mice did not show a return to normal at 7 DPI which suggests that after brain injury, MT-I/II is responsible for sequestering elevated levels of zinc to the liver.

CONCLUSION

MT-I/II is up-regulated in the liver after brain injury and modulates the amount of zinc that is sequestered to the liver.

CD11d integrin blockade reduces the systemic inflammatory response syndrome after spinal cord injury

Traumatic injury to the spinal cord triggers a systemic inflammatory response syndrome (SIRS), in which inflammatory cells from the circulation invade organs such as the liver, lung and kidney, leading to damage of these organs. Our previous study (Gris, et al, Exp. Neurol, 2008) demonstrated that spinal cord injury (SCI) activates circulating neutrophils that then invade the lung and kidney from 2 to 24 h after injury, increasing myeloperoxidase activity, cyclooxygenase-2 and matrix metalloproteinase-9 expression and lipid peroxidation in these organs. The present study was designed to ascertain whether a treatment that limits the influx of leukocytes into the injured spinal cord would also be effective in reducing the SIRS after SCI. This treatment is intravenous delivery of a monoclonal antibody (mAb) against the CD11d subunit of the CD11d/CD18 integrin expressed by neutrophils and monocytes. We delivered the anti-CD11d mAb at 2 h post moderate clip compression SCI at the 4th or 12th thoracic segments and assessed inflammation, oxidative activity and cellular damage within the lung, kidney and liver at 12 h post-injury. In some analyses we compared high and low thoracic injuries to evaluate the importance of injury level on the intensity of the SIRS. After T4 injury, treatment with the anti-integrin mAb reduced the presence of neutrophils and macrophages in the lung, with associated decreases in expression of NF-κB and oxidative enzymes and in the concentration of free radicals in this organ. The treatment also reduced lipid peroxidation, protein nitration and cell death in the lung. The anti-CD11d treatment also reduced the inflammatory cells within the kidney after T4 injury, as well as the free radical concentration and amount of lipid peroxidation. In the liver, the mAb treatment reduced the influx of neutrophils but most of the other measures examined were unaffected by SCI. The inflammatory responses within the lung and kidney were often greater after T4 than T12 injury. Clinical studies show that SIRS, with its associated organ failure, contributes significantly to the morbidity and mortality of SCI patients. This anti-integrin treatment may block the onset of SIRS after SCI.

Acute lung injury in patients with severe brain injury: a double hit model

The presence of pulmonary dysfunction after brain injury is well recognized. Acute lung injury (ALI) occurs in 20% of patients with isolated brain injury and is associated with a poor outcome. The "blast injury" theory, which proposes combined "hydrostatic" and "high permeability" mechanisms for the formation of neurogenic pulmonary edema, has been challenged recently by the observation that a systemic inflammatory response may play an integral role in the development of pulmonary dysfunction associated with brain injury. As a result of the primary cerebral injury, a systemic inflammatory reaction occurs, which induces an alteration in blood-brain barrier permeability and infiltration of activated neutrophils into the lung. This preclinical injury makes the lungs more susceptible to the mechanical stress of an injurious ventilatory strategy. Tight CO2 control is a therapeutic priority in patients with acute brain injury, but the use of high tidal volume ventilation may contribute to the development of ALI. Establishment of a therapeutic regimen that allows the combination of protective ventilation with the prevention of hypercapnia is, therefore, required. Moreover, in patients with brain injury, hypoxemia represents a secondary insult associated with a poor outcome. Optimal oxygenation may be achieved by using an adequate FiO2 and by application of positive end-expiratory pressure (PEEP). PEEP may, however, affect the cerebral circulation by hemodynamic and CO2-mediated mechanisms and the effects of PEEP on cerebral hemodynamics should be monitored in these patients and used to titrate its application.

Lack of correlation among intracerebral cytokines, intracranial pressure, and brain tissue oxygenation in patients with traumatic brain injury and diffuse lesions

OBJECTIVES

To determine the evolution of cytokine patterns using microdialysis in patients with traumatic brain injury with diffuse lesions and to study the relationship between cytokines and intracranial pressure, brain tissue oxygenation and lesion type on the computed cranial tomography scan (patients with and without brain swelling).

DESIGN

Prospective and observational study.

SETTING

Third-level university hospital.

PATIENTS

Patients between 15 and 65 yrs with severe traumatic brain injury and a diffuse lesion requiring intracranial pressure and brain tissue oxygenation monitoring were eligible.

INTERVENTIONS

Microdialysis catheters with a high-cutoff membrane of 100 kDa were inserted.

RESULTS

Sixteen patients were included in the analysis. There was a substantial interindividual variability between cytokine values. The highest concentrations for the interleukin-1β, interleukin-6, and interleukin-8 were measured during the first 24 hrs followed by a gradual decline. The average concentration for interleukin-10 did not vary over time. This pattern is the most frequent in patients with traumatic brain injury with diffuse lesions. The intracranial pressure-cytokines correlation coefficients for the 16 patients varied substantially: interleukin-1β-intracranial pressure (-0.76 to 0.63); interleukin-6-intracranial pressure (-0.83 to 0.78); interleukin-8-intracranial pressure (-0.86 to 0.84); and interleukin-10-intracranial pressure (-0.36 to 0.65). The brain tissue oxygenation-cytokine correlation coefficients, like with intracranial pressure, also varied between patients: interleukin-1β-brain tissue oxygenation (-0.49 to 0.68), interleukin-6-brain tissue oxygenation (-0.99 to 0.84); interleukin-8-brain tissue oxygenation (-0.65 to 0.74); and interleukin-10-brain tissue oxygenation (-0.34 to 0.52). Similarly, we found no difference in the cytokine values inpatient microdialysis with and without swelling in the computed tomographic scan.

CONCLUSIONS

No clear relationship was found between the temporal pattern of cytokines and the behavior of the intracranial pressure, brain tissue oxygenation, and the presence or absence of swelling in the computed tomography scan. This study demonstrates the feasibility of microdialysis in recovering cytokines for a prolonged time, although there may be some nonresolved methodologic problems with this technique when we try to study the inflammation during traumatic brain injury that could affect the results and make interpretation of microdialysis data prone to difficulties.

Augmented creatinine clearance in traumatic brain injury

BACKGROUND

Hypertonic saline and/or norepinephrine infusion are routinely used to achieve a desired cerebral perfusion pressure (CPP) in the management of traumatic brain injury (TBI). We hypothesized that creatinine clearances (CrCls) would be significantly augmented in this setting.

METHODS

This was an observational cohort study in TBI patients older than 16 years with normal serum creatinine concentrations, requiring maintenance of CPP. Eight-hour urinary CrCl collections were performed while on and off active management. Demographic data, use of vasoactive medications, fluid balance, feeding regimen, and hemodynamic variables were recorded throughout the study period. Augmented CrCl was defined as >150 mL/min/1.73 m(2) in women and >160 mL/min/1.73 m(2) in men.

RESULTS

Twenty patients were enrolled, and augmented clearances were demonstrated in 17 (85%). The mean maximum CrCl was 179 mL/min/1.73 m(2) while receiving CPP therapy (95% confidence interval [CI], 159-198), returning to a mean of 111 mL/min/1.73 m(2) (95% CI, 91-131; P < 0.001) when measured after discharge from the intensive care unit. The mean CrCl in the intensive care unit while not receiving CPP therapy was 150 mL/min/1.73 m(2) (95% CI, 134-167; P = 0.03). The mean time to reach peak CrCl while receiving active treatment was 4.7 days (95% CI, 3.0-6.4). In a multivariate analysis, norepinephrine use, saline loading, mean arterial blood pressure, and central venous pressure were associated with augmented CrCl on the day of measurement.

CONCLUSIONS

Augmented CrCls are common in TBI patients receiving active management of CPP and persist even after discontinuation of such therapy. Further work is needed to clarify the impact of such clearances on renally excreted drugs in this setting.

A breath of fresh air for lung transplant recipients

Lung transplantation is a definitive therapy for the treatment of many end-stage lung diseases. However, because of donor-related morbidities, only 15% of donor lungs are suitable for transplantation, which leads to an increased risk of death for prospective patients waiting for this lifesaving procedure. A technique reported by Keshavjee's group in this issue of Science Translational Medicine may help address this problem, not only by repairing donor lungs before transplant, but also by possibly preventing lung injury after transplantation.

Traumatic stress and hepatocyte apoptosis

Trauma can cause stress in organisms and may promote cell apoptosis and lead to pathological damage. A variety of factors are involved in this process. The mechanisms responsible for traumatic stress-induced apoptosis are complex and controversial, especially in non-nervous organs. The liver plays a key role in metabolism and is one of the target organs of severe stress. Stress-induced hyperglycemia, calcium overload, oxidative stress, ischemia/reperfusion, inflammatory response, and immunosuppression caused by traumatic stress may lead to hepatocyte apoptosis. Thus, it is of great significance to explore the relationship between traumatic stress and hepatocyte apoptosis.

Brain death and its implications for management of the potential organ donor

The systemic physiologic changes that occur during and after brain death affect all organs suitable for transplantation. Major changes occur in the cardiovascular, pulmonary, endocrine, and immunological systems, and, if untreated may soon result in cardiovascular collapse and somatic death. Understanding these complex physiologic changes is mandatory for developing effective strategies for donor resuscitation and management in such a way that the functional integrity of potentially transplantable organs is maintained. This review elucidates these physiological changes and their consequences, and based on these consequences the rationale behind current medical management of brain-dead organ donors is discussed.

Broad DNA repair responses in neural injury are associated with activation of the IL-6 pathway in cholesterol-fed rabbits

The importance of DNA repair in the pathogenic mechanism of Alzheimer's Disease (AD) is still poorly understood. Here, we report that a broad range of responses by DNA repair proteins plays a critical role in the regulation of inflammatory response in rabbits fed with cholesterol-rich diet, a model system for AD. We found accumulation of oxodG DNA adduct in the brain of rabbits fed with cholesterol-enriched diets compared to control diets, which subsequently induced a broad range of DNA repair protein activities. Also, the hippocampus was identified as the primary site of oxidative DNA damage and elevated OGG1 activity. In addition, a physical interaction between XPB and OGG1 may account for a potential mechanism involving these DNA repair responses. DNA repair proteins also impact activation of various signaling cascades, including Src in response to cholesterol oxidation. Furthermore, OGG1 deficient mice showed no IL-6 activation as seen in wt mice but a drastic increase of TNF-alpha, a pro-inflammatory cytokine. Thus, OGG1 may be associated with cytokine production induced by high cholesterol levels, impacting neurodegeneration. Together, our studies suggest that critical DNA repair proteins are associated with development of AD, and may serve as potential targets for the treatment of AD.

Psychoneuroimmunology of stroke

Stroke is the major cause of disability in the Western world and is the third greatest cause of death, but there are no widely effective treatments to prevent the devastating effects of stroke. Extensive and growing evidence implicates inflammatory and immune processes in the occurrence of stroke and particularly in the subsequent injury. Several inflammatory mediators have been identified in the pathogenesis of stroke including specific cytokines, adhesion molecules, matrix metalloproteinases, and eicosanoids. An early clinical trial suggests that inhibiting interleukin-1 may be of benefit in the treatment of acute stroke.

Acute lung injury in patients with severe brain injury: a double hit model

The presence of pulmonary dysfunction after brain injury is well recognized. Acute lung injury (ALI) occurs in 20% of patients with isolated brain injury and is associated with a poor outcome. The "blast injury" theory, which proposes combined "hydrostatic" and "high permeability" mechanisms for the formation of neurogenic pulmonary edema, has been challenged recently by the observation that a systemic inflammatory response may play an integral role in the development of pulmonary dysfunction associated with brain injury. As a result of the primary cerebral injury, a systemic inflammatory reaction occurs, which induces an alteration in blood-brain barrier permeability and infiltration of activated neutrophils into the lung. This preclinical injury makes the lungs more susceptible to the mechanical stress of an injurious ventilatory strategy. Tight CO2 control is a therapeutic priority in patients with acute brain injury, but the use of high tidal volume ventilation may contribute to the development of ALI. Establishment of a therapeutic regimen that allows the combination of protective ventilation with the prevention of hypercapnia is, therefore, required. Moreover, in patients with brain injury, hypoxemia represents a secondary insult associated with a poor outcome. Optimal oxygenation may be achieved by using an adequate FiO2 and by application of positive end-expiratory pressure (PEEP). PEEP may, however, affect the cerebral circulation by hemodynamic and CO2-mediated mechanisms and the effects of PEEP on cerebral hemodynamics should be monitored in these patients and used to titrate its application.

Changes in serum levels of receptor activator of nuclear factor-kappaB ligand, osteoprotegerin, IL-6 and TNF-alpha in patients with a concomitant head injury and fracture

INTRODUCTION

Several reports indicated that interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF- alpha) play important regulatory roles in bone remodeling and homeostasis. In addition, receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) have been shown to be important regulators of osteoclastogenesis during bone remodeling, and their expressions were examined during fracture healing in a mouse model of tibial fracture. However, studies linking RANKL, OPG, IL-6 and TNF-alpha in patients with head injury and fracture are lacking.

PATIENTS AND METHODS

Within the first few hours of admission to hospital and at 4, 8, and 12 weeks after the injury, we evaluated changes in serum levels of RANKL, OPG, IL-6 and TNF-alpha in 24 male patients with a concomitant head injury and fracture and in 26 male patients with fracture only. These levels were compared with those found in 36 healthy controls.

RESULTS

The RANKL/OPG ratios were found to significantly lower in patients with a concomitant head injury and fracture than in the controls immediately after admission and at 4, 8, and 12 weeks after the injury. In addition, RANKL/OPG ratios were significantly lower in patients with a concomitant head injury and fracture than in those with fracture at 8 and 12 weeks after the injury. The serum IL-6 levels were significantly higher in patients with a concomitant head injury and fracture than in the controls upon admission, and at 4, 8, and 12 weeks after the injury. Moreover, the serum IL-6 levels were significantly higher in patients with a head injury and fracture than in those with just a fracture at 4, 8, and 12 weeks after the injury.

CONCLUSIONS

Based on these changes in the profiles of RANKL, OPG, and IL-6 and the RANKL/OPG ratio, altered repair of a fracture can occur in patients with a concomitant head injury and fracture.

Systemic inflammation in the brain-dead organ donor

Brain death itself impairs organ function in the potential donor, thereby limiting the number of suitable organs for transplantation. In addition, graft survival of kidneys obtained from brain-dead (BD) donors is inferior to that of kidneys obtained from living donors. Experimental studies confirm an inferior graft survival for the heart, liver and lungs from BD compared with living donors. The mechanism underlying the deteriorating effect of brain death on the organs has not yet been fully established. We know that brain death triggers massive circulatory, hormonal and metabolic changes. Moreover, the past 10 years have produced evidence that brain death is associated with a systemic inflammatory response. However, it remains uncertain whether the inflammation is induced by brain death itself or by events before and after becoming BD. The purpose of this study is to discuss the risk factors associated with brain death in general and the inflammatory response in the organs in particular. Special attention will be paid to the heart, lung, liver and kidney and evidence will be presented from clinical and experimental studies.

CYP4Fs expression in rat brain correlates with changes in LTB4 levels after traumatic brain injury

Cytochrome P450 (CYP) 4Fs constitute a subgroup of the cytochrome P450 superfamily and are involved in cellular protection and metabolism of numerous molecules, including drugs, toxins, and eicosanoids. CYP4Fs are widely distributed in rat brain with each isoform having a unique distribution pattern throughout different brain regions. The present study shows that traumatic brain injury (TBI) triggers inflammation and elicits changes in mRNA expression of CYP4Fs in the frontal and occipital lobes and the hippocampus. At 24 h post-injury, almost all CYP4F mRNA expression is suppressed compared with sham control throughout these three regions, while at 2 weeks post-injury, all CYP4F mRNAs increase, reaching levels higher than those at 24 h post-injury or uninjured controls. These changes in CYP4F levels inversely correlate with levels of leukotriene B4 (LTB4) levels in the brain following injury at the same time points. TBI also causes changes in CYP4F protein expression and localization around the injury site. CYP4F1 and CYP4F6 immunoreactivity increases in surrounding astrocytes, while CYP4F4 immunoreactivity shifts from endothelia of cerebral vessels to astrocytes.

Increased oxidative activity in human blood neutrophils and monocytes after spinal cord injury

Traumatic injury can cause a systemic inflammatory response, increasing oxidative activity of circulating leukocytes and potentially exacerbating the original injury, as well as causing damage to initially unaffected organs. Although the importance of intraspinal inflammation after human spinal cord injury is appreciated, the role of the systemic inflammatory response to this injury is not widely recognised. We investigated oxidative activity of blood leukocytes from nine cord-injured subjects and six trauma controls (bone fractures without CNS injury) at 6 h-2 weeks after injury, comparing values to those of ten uninjured subjects. Neutrophil and monocyte free radical production, evaluated by flow cytometry, increased significantly more in cord injury subjects than in trauma controls (6-fold vs 50% increases). In leukocyte homogenates, the concentration of free radicals increased significantly more in cord injury subjects (2-fold) than in the trauma controls (1.6-fold) as did activity of myeloperoxidase (2.3-fold vs. 1.7-fold). Moreover, in homogenates and blood smears, expression of the NADPH oxidase subunit gp91(phox) and of the oxidative enzyme, inducible nitric oxide synthetase was 20-25% greater in cord injury subjects than in trauma controls. Expression of the pro-inflammatory transcription factor NF-kappaB and of cyclooxygenase-2 increased similarly after both injuries. Finally, aldehyde products of tissue-damaging lipid peroxidation also increased significantly more in the plasma of spinal cord injury subjects than in trauma controls (2.6 fold vs. 1.9-fold). Spinal cord injury causes a particularly intense systemic inflammatory response. Limiting this response briefly after cord injury should protect the spinal cord and tissues/organs outside the CNS from secondary damage.

The systemic inflammatory response after spinal cord injury damages lungs and kidneys

Spinal cord injury (SCI) triggers a well characterized, acute, local inflammation leading to secondary damage at the lesion site. Another little recognized problem may be the activation of circulating inflammatory cells that potentially damage tissues outside the cord. We investigated this problem using severe clip-compression SCI in rats. We studied systemic inflammation after SCI and its effects on lungs and kidneys, as dysfunction of these organs is a frequent, early complication after SCI. From 2-24 h after SCI, the number of circulating neutrophils (especially immature cells) significantly increased by 3-10 fold. Flow cytometry experiments revealed that SCI transiently activates these neutrophils, causing increased oxidative responses to phorbolmyristic acid at 2 h after SCI; then, from 4-24 h, the neutrophils were less responsive. Neutrophil longevity was increased (30-50% decrease in apoptosis) at 2-8 h after SCI. Immunohistochemical analyses demonstrated the invasion of neutrophils into lungs and kidneys (2 h-7 d after SCI) and more phagocytic macrophages in lungs (12 h, 3 d after SCI). Myeloperoxidase and matrix metalloproteinase-9 activity in lung and kidney homogenates increased (12 h-7 d after SCI). Expression of COX-2 increased and lipid peroxidation also occurred within this time. Control experiments inducing local cord damage by excitotoxic quisqualate injection verified that SCI per se is sufficient to trigger systemic inflammation and organ damage. In summary, SCI mobilizes and activates neutrophils that then migrate into visceral organs, a phenomenon occurring in parallel with their well-known entry into the cord injury site. The systemic inflammatory response to SCI should be targeted in the development of new therapeutic strategies to treat SCI.

Extracranial complications in patients with acute brain injury: a post-hoc analysis of the SOAP study

OBJECTIVE

To assess the incidence and severity of nonneurological organ dysfunction and its effect on outcome in acute neurological patients in an international cohort observational study.

DESIGN AND SETTING

Analysis of database from the observational Sepsis Occurrence in Acutely Ill Patients (SOAP) study in 198 intensive care units (ICUs) in 24 European countries.

PATIENTS

All adult patients admitted to the participating ICUs between 1 and 15 May 2002. Of the 3,147 patients in the SOAP database 373 (12%) were admitted with a neurological diagnosis, including 154 (41%) with traumatic brain injury and 186 (50%) with cerebrovascular accident.

MEASUREMENTS AND RESULTS

Patients were followed until death, hospital discharge, or for 60 days. Neurological patients were younger and had a higher incidence of trauma and fewer comorbidities than nonneurological patients. Neurological patients developed ICU-acquired sepsis and respiratory failure more frequently than the other patients. ICU and hospital mortality rates were higher and ICU length of stay longer in neurological than in nonneurological patients. Multivariate logistic analysis showed that, in addition to the Glasgow Coma Score (GCS) and the presence of nontraumatic brain injury, cardiovascular failure, hepatic failure, and ALI/ARDS were the only factors independently associated with a higher risk of death in the ICU in patients with a neurological diagnosis.

CONCLUSIONS

Although neurological patients were younger and had fewer comorbidities, they developed ICU-acquired sepsis and respiratory failure more frequently than other patients. Efforts should be oriented to reduce cardiovascular, hepatic, and respiratory complications.

High tidal volume is associated with the development of acute lung injury after severe brain injury: an international observational study

OBJECTIVE

Although a significant number of patients with severe brain injury develop acute lung injury, only intracranial risk factors have previously been studied. We investigated the role of extracranial predisposing factors, including hemodynamic and ventilatory management, as independent predictors of acute lung injury in brain-injured patients.

DESIGN

Prospective multicenter observational study.

SETTING

Four European intensive care units in university-affiliated hospitals.

PATIENTS

Eighty-six severely brain-injured patients enrolled in 13 months.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

All patients with severe brain injury (Glasgow Coma Scale score <9) were studied for 8 days from admission. Ventilatory pattern, respiratory system compliance, blood gas analysis, and hemodynamic profile were recorded and entered in a stepwise regression model. Length of stay in the intensive care unit, ventilator-free days, and mortality were collected. Eighteen patients (22%) developed acute lung injury on day 2.8 +/- 1. They were initially ventilated with significantly higher tidal volume per predicted body weight (9.5 +/- 1 vs. 10.4 +/- 1.1), respiratory rate, and minute ventilation and more often required vasoactive drugs (p < .05). In addition to a lower Pao2/Fio2 (odds ratio 0.98, 95% confidence interval 0.98-0.99), the use of high tidal volume (odds ratio 5.4, 95% confidence interval 1.54-19.24) and relatively high respiratory rate (odds ratio 1.8, 95% confidence interval 1.13-2.86) were independent predictors of acute lung injury (p < .01). After the onset of acute lung injury, patients remained ventilated with similar tidal volumes to maintain mild hypocapnia and had a longer length of stay in the intensive care unit and fewer ventilator-free days (p < .05).

CONCLUSIONS

In addition to a lower Pao2/Fio2, the use of high tidal volume and high respiratory rate are independent predictors of acute lung injury in patients with severe brain injury. In this patient population, alternative ventilator strategies should be considered to protect the lung and guarantee a tight CO2 control.

Effect of time, injury, age and ethanol on interpatient variability in valproic acid pharmacokinetics after traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) results in an increase in hepatic metabolism. The increased metabolism is in significant contrast to a large body of in vitro and in vivo data demonstrating that activation of the host-defence response downregulates hepatic metabolism. Theoretically, this occurs because of activation of the pro-inflammatory cytokines tumour necrosis factor-alpha, interferon-gamma, interleukin (IL)-1 and IL-6. As part of a large double-blind, placebo-controlled clinical trial evaluating the use of valproic acid for prophylaxis of post-traumatic seizures, we obtained extensive valproic acid concentration-time data. Valproic acid is a hepatically metabolised, low extraction-ratio drug. Therefore, unbound clearance (CL(u)) is equal to intrinsic or metabolic clearance.

OBJECTIVE

The objective of this study was to evaluate the time-dependent effects of TBI on the pharmacokinetics of total and unbound valproic acid with the goal of identifying patient factors that may predict changes in total clearance (CL) and CL(u). In addition, by determining the factors that influence the magnitude and time course of induction of hepatic metabolism and understanding their interaction with the host-defence mediators, we can further our insight into the mechanism(s) responsible for the changes in CL and CL(u).

STUDY DESIGN

Valproic acid plasma concentration data were obtained from 158 TBI patients. Unbound valproic acid plasma concentrations were estimated using total valproic acid plasma and albumin concentrations following a Scatchard equation binding model previously developed in a subset of TBI patients. The effect of 13 patient factors on CL and CL(u) was evaluated initially in a univariate analysis. The significant factors were then included in a multiple linear regression analysis by use of step-wise selection and forward selection procedures.

RESULTS

CL and CL(u) were significantly increased after TBI in a time-dependent manner. The average increase was >75% by weeks 2 and 3 post-injury. The magnitude of the induction of CL was increased with decreased albumin concentrations, in addition to the presence of ethanol on admission, increased severity of head injury, tube feeding and total parenteral nutrition (TPN). The magnitude of induction of CL(u) was increased by older age, presence of ethanol on admission, increased severity of head injury, tube feeding, TPN, and if the patient had a post-injury neurosurgical procedure. The time to normalisation of CL(u) was significantly longer in patients with head injury plus other injuries compared with those with head injury alone.

CONCLUSIONS

As has been reported with other drugs, TBI results in a significant increase in the metabolism of valproic acid. The patient factors identified in this study that resulted in an increase in the magnitude and time course of the induction of CL(u) (ethanol, older age, presence of a neurosurgical procedure, severity of TBI and presence of multiple non-TBI injuries) have all been reported to cause a shift to the anti-inflammatory mediators IL-4 and IL-10. This suggests that the increase in hepatic metabolism after TBI may be due to the increased presence of anti-inflammatory mediators in contrast to the inhibition effect of the pro-inflammatory mediators in non-TBI inflammation and infection.

Systemic complications after head injury: a clinical review

Non-neurological organ dysfunction is common after traumatic brain injury and is an independent contributor to morbidity and mortality. It represents a risk factor that is potentially amenable to treatment, and early recognition and prompt intervention may improve outcome. This article reviews the current evidence for the mechanisms and treatment of non-neurological organ dysfunction after head injury.

Systemic metabolic effects of combined insulin-like growth factor-I and growth hormone therapy in patients who have sustained acute traumatic brain injury

OBJECT

Hypermetabolism, hypercatabolism, refractory nitrogen wasting, hyperglycemia, and immunosuppression accompany traumatic brain injury (TBI). Pituitary dysfunction occurs, affecting growth hormone (GH) and plasma insulin-like growth factor-I (IGF-I) concentrations. The authors evaluated whether combination IGF-I/GH therapy improved metabolic and nutritional parameters after moderate to severe TBI.

METHODS

The authors conducted a prospective, randomized, double-blind study comparing combination IGF-I/GH therapy and a placebo treatment. Ninety-seven patients with TBI were enrolled in the study within 72 hours of injury and were assigned to receive either combination IGF-I/GH therapy or placebo. All patients received concomitant nutritional support. Insulin-like growth factor-I was administered by continuous intravenous infusion (0.01 mg/kg/hr), and GH (0.05 mg/kg/day) was administered subcutaneously. Placebo control group patients received normal saline solution in place of both agents. Nutritional and metabolic monitoring continued throughout the 14-day treatment period. The two groups did not differ in energy expenditure, nutrient intake, or use of insulin treatment. The mean daily serum glucose concentration was higher in the treatment group (123 +/- 24 mg/dl) than in the control group (104 +/- 11 mg/dl) (p < 0.03). A positive nitrogen balance was achieved within the first 24 hours in the treatment group and remained positive in that group throughout the treatment period (p < 0.05). This pattern was not observed in the control group. Plasma IGF-I concentrations were above 350 ng/ml in the treatment group throughout the study period. Overall, the mean plasma IGF-I concentrations were 1003 +/- 480.6 ng/ml in the treatment group and 192 +/- 46.2 ng/ml in the control group (p < 0.01).

CONCLUSIONS

The combination of IGF-I and GH produced sustained improvement in metabolic and nutritional endpoints after moderate to severe acute TBI.

Neurogenic pulmonary edema

Neurogenic pulmonary edema (NPE) is usually defined as an acute pulmonary edema occurring shortly after a central neurologic insult. It has been reported regularly for a long time in numerous and various injuries of the central nervous system in both adults and children, but remains poorly understood because of the complexity of its pathophysiologic mechanisms involving hemodynamic and inflammatory aspects. NPE seems to be under-diagnosed in acute neurologic injuries, partly because the prevention and detection of non-neurologic complications of acute cerebral insults are not at the forefront of the strategy of physicians. The presence of NPE should be high on the list of diagnoses when patients with central neurologic injury suddenly become dyspneic or present with a decreased P(a)o(2)/F(i)o(2) ratio. The associated mortality rate is high, but recovery is usually rapid with early and appropriate management. The treatment of NPE should aim to meet the oxygenation needs without impairing cerebral hemodynamics, to avoid pulmonary worsening and to treat possible associated myocardial dysfunction. During brain death, NPE may worsen myocardial dysfunction, preventing heart harvesting.

Psychoneuroimmunology of stroke

There is now considerable evidence from both experimental and clinical studies that immune and inflammatory processes can contribute to the onset of stroke and the neurologic and psychologic outcomes. Several specific therapeutic targets have been identified that may significantly improve the devastating impact of stroke.

An apolipoprotein E-based therapeutic improves outcome and reduces Alzheimer's disease pathology following closed head injury: evidence of pharmacogenomic interaction

Apolipoprotein E (apoE) modifies glial activation and the CNS inflammatory response in an isoform-specific manner. Peptides derived from the receptor-binding region of apoE have been demonstrated to maintain the functional activity of the intact protein, and to improve histological and functional deficits after closed head injury. In the current study, APOE2, APOE3, and APOE4 targeted replacement (TR) mice expressing the human apoE protein isoforms (apoE2, apoE3 and apoE4) were used in a clinically relevant model of closed head injury to assess the interaction between the humanized apoE background and the therapeutic apoE mimetic peptide, apoE(133-149). Treatment with the apoE-mimetic peptide reduced microglial activation and early inflammatory events in all of the targeted replacement animals and was associated with histological and functional improvement in the APOE2TR and APOE3TR animals. Similarly, brain beta amyloid protein (Abeta)(1-42) levels were increased as a function of head injury in all of the targeted replacement mice, while treatment with apoE peptide suppressed Abeta(1-42) levels in the APOE2TR and APOE3TR animals. These results suggest a pharmacogenomic interaction between the therapeutic effects of the apoE mimetic peptide and the human apoE protein isoforms. Furthermore, they suggest that administration of apoE-mimetic peptides may serve as a novel therapeutic strategy for the treatment of acute and chronic neurological disease.

Recombinant human TNFalpha induces concentration-dependent and reversible alterations in the electrophysiological properties of axons in mammalian spinal cord

Increased expression of the proinflammatory cytokine tumor necrosis factor-alpha (TNFalpha) and its soluble receptors is evident within the central nervous system (CNS) following traumatic brain injury and spinal cord injury. TNFalpha is integral to the acute inflammatory cascade that follows neurotrauma and has been shown to have both beneficial and detrimental properties. We examined the effects of varying concentrations (1-5000 ng/mL) of recombinant human TNFalpha (rhTNFalpha) on select electrophysiological properties of excised guinea pig spinal cord tissue. Pulsed electrical stimuli (0.33 Hz) were delivered to strips of isolated ventral white matter in a double sucrose gap chamber. Recordings were made of the compound action potential (CAP) and membrane potential before, during, and after bathing the tissue with rhTNFalpha for 30 min. Increasing concentrations of rhTNFalpha yielded progressively greater reductions in amplitude of the CAP that were temporally associated with depolarization of the resting compound membrane potential. These effects were largely reversed on washout of rhTNFalpha and were not present when heat-denatured rhTNFalpha was introduced. The results provide evidence that elevated concentrations of TNFalpha induce reversible depolarization of the compound membrane potential and reduction in CAP amplitude, sometimes to the point of extinction of the CAP, suggestive of impaired axonal conduction. These observations point to a new mechanism of immune-mediated central conduction deficit. Cytokine-induced alterations in membrane properties and axonal conduction may contribute to neurological deficits following CNS injury by compounding trauma-induced myelinopathy and axonopathy.