Hyperglycemia, cerebrospinal fluid lactic acidosis, and cerebral blood flow in severely head-injured patients

Accurate and stable chronic in vivo voltammetry enabled by a replaceable subcutaneous reference electrode

In vivo sensing of neurotransmitters has provided valuable insight into both healthy and diseased brain. However, chronically implanted Ag/AgCl reference electrodes suffer from degradationgradation, resulting in errors in the potential at the working electrode. Here, we report a simple, effective way to protect in vivo sensing measurements from reference polarization with a replaceable subcutaneously implanted reference. We compared a brain-implanted reference and a subcutaneous reference and observed no difference in impedance or dopamine redox peak separation in an acute preparation. Chronically, peak background potential and dopamine oxidation potential shifts were eliminated for three weeks. Scanning electron microscopy shows changes in surface morphology and composition of chronically implanted Ag/AgCl electrodes, and postmortem histology reveals extensive cell death and gliosis in the surrounding tissue. As accurate reference potentials are critical to in vivo electrochemistry applications, this simple technique can improve a wide and diverse assortment of in vivo preparations.

Endoscopically Treated Subacute Subdural Hematoma Presenting Postoperative Cerebral Hyperperfusion Syndrome: Chronological Changes of Cerebral Blood Flow on Arterial Spin Labeling and Subcortical Low Intensity on Fluid-attenuated Inversion Recovery Images

Subacute subdural hematoma (SASDH) is a neurotraumatic entity. There are few reports of chronological changes of cerebral blood flow (CBF) on arterial spin labeling (ASL) and subcortical low intensity (SCLI) on fluid-attenuated inversion recovery (FLAIR) images of magnetic resonance imaging (MRI) observations from the injury onset, deterioration, to post-surgery. We reported a SASDH patient presenting postoperative cerebral hyperperfusion (CHP) syndrome with chronological changes of those findings. An 85-year-old woman fell and presented right ASDH. She was treated conservatively due to no neurological deficits. On day 3, ASL image revealed increased CBF against brain compression. On day 7, the CBF was normalized on ASL image, but SCLI was confirmed. On day 14, SCLI was strengthened. Then she developed left hemiparesis due to brain compression by SASDH. Considering age and comorbidities, we performed endoscopic hematoma removal under local anesthesia, and her neurological deficits improved after the surgery. On postoperative day 1, she newly presented left upper limb paresis. MRI revealed increased CBF and enhanced SCLI. We diagnosed CHP syndrome, and antihypertensive treatment improved the symptoms gradually. However, SCLI had been consistently observed, and CBF easily changed depending on the blood pressure, suggesting dysfunction of the CBF autoregulation. We showed the endoscopically treated SASDH patient with CBF’s chronological changes on ASL images and SCLI on FLAIR images. Long-time brain compression would lead to dysfunction of the CBF autoregulation, and we should be careful about CHP syndrome after the endoscopic surgery for SASDH.

Neurocritical Management of Traumatic Acute Subdural Hematomas

Acute subdural hematoma (ASDH) has been a major part of traumatic brain injury. Intracranial hypertension may be followed by ASDH and brain edema. Regardless of the complicated pathophysiology of ASDH, the extent of primary brain injury underlying the ASDH is the most important factor affecting outcome. Ongoing intracranial pressure (ICP) increasing lead to cerebral perfusion pressure (CPP) decrease and cerebral blood flow (CBF) decreasing occurred by CPP decrease. In additionally, disruption of cerebral autoregulation, vasospasm, decreasing of metabolic demand may lead to CBF decreasing. Various protocols for ICP lowering were introduced in neuro-trauma field. Usage of anti-epileptic drugs (AEDs) for ASDH patients have controversy. AEDs may reduce the risk of early seizure (<7 days), but, does not for late-onset epilepsy. Usage of anticoagulants/antiplatelets is increasing due to life-long medical disease conditions in aging populations. It makes a difficulty to decide the proper management. Tranexamic acid may use to reducing bleeding and reduce ASDH related death rate. Decompressive craniectomy for ASDH can reduce patient's death rate. However, it may be accompanied with surgical risks due to big operation and additional cranioplasty afterwards. If the craniotomy is a sufficient management for the ASDH, endoscopic surgery will be good alternative to a conventional larger craniotomy to evacuate the hematoma. The management plan for the ASDH should be individualized based on age, neurologic status, radiologic findings, and the patient's conditions.

Glucose transporters in brain in health and disease

Energy demand of neurons in brain that is covered by glucose supply from the blood is ensured by glucose transporters in capillaries and brain cells. In brain, the facilitative diffusion glucose transporters GLUT1-6 and GLUT8, and the Na⁺-d-glucose cotransporters SGLT1 are expressed. The glucose transporters mediate uptake of d-glucose across the blood-brain barrier and delivery of d-glucose to astrocytes and neurons. They are critically involved in regulatory adaptations to varying energy demands in response to differing neuronal activities and glucose supply. In this review, a comprehensive overview about verified and proposed roles of cerebral glucose transporters during health and diseases is presented. Our current knowledge is mainly based on experiments performed in rodents. First, the functional properties of human glucose transporters expressed in brain and their cerebral locations are described. Thereafter, proposed physiological functions of GLUT1, GLUT2, GLUT3, GLUT4, and SGLT1 for energy supply to neurons, glucose sensing, central regulation of glucohomeostasis, and feeding behavior are compiled, and their roles in learning and memory formation are discussed. In addition, diseases are described in which functional changes of cerebral glucose transporters are relevant. These are GLUT1 deficiency syndrome (GLUT1-SD), diabetes mellitus, Alzheimer’s disease (AD), stroke, and traumatic brain injury (TBI). GLUT1-SD is caused by defect mutations in GLUT1. Diabetes and AD are associated with changed expression of glucose transporters in brain, and transporter-related energy deficiency of neurons may contribute to pathogenesis of AD. Stroke and TBI are associated with changes of glucose transporter expression that influence clinical outcome.

Metabolic characterization of tuberculous meningitis in a South African paediatric population using 1H NMR metabolomics

OBJECTIVE

To better characterize the cerebrospinal fluid (CSF) metabolic profile of tuberculous meningitis (TBM) cases using a South African paediatric cohort.

METHODS

¹H NMR metabolomics was used to analyse the CSF of a South African paediatric cohort. Univariate and multivariate statistical analyses were performed to compare a homogeneous control group with a well-defined TBM group.

RESULTS

Twenty metabolites were identified to discriminate TBM cases from controls. As expected, reduced glucose and elevated lactate were the dominating discriminators. A closer investigation of the CSF metabolic profile yielded 18 metabolites of statistical significance. Ten metabolites (acetate, alanine, choline, citrate, creatinine, isoleucine, lysine, myo-inositol, pyruvate and valine) overlapped with two other prior investigations. Eight metabolites (2-hydroxybutyrate, carnitine, creatine, creatine phosphate, glutamate, glutamine, guanidinoacetate and proline) were unique to our paediatric TBM cohort.

CONCLUSIONS

Through strict exclusion criteria, quality control checks and data filtering, eight unique CSF metabolites associated with TBM were identified for the first time and linked to: uncontrolled glucose metabolism, upregulated proline and creatine metabolism, detoxification and disrupted glutamate-glutamine cycle in the TBM samples. Associated with oxidative stress and chronic neuroinflammation, our findings collectively imply destabilization, and hence increased permeability, of the blood-brain barrier in the TBM cases.

RS1 (Rsc1A1) deficiency limits cerebral SGLT1 expression and delays brain damage after experimental traumatic brain injury

Acute cerebral lesions are associated with dysregulation of brain glucose homeostasis. Previous studies showed that knockdown of Na⁺ -D-glucose cotransporter SGLT1 impaired outcome after middle cerebral artery occlusion and that widely expressed intracellular RS1 (RSC1A1) is involved in transcriptional and post-translational down-regulation of SGLT1. In the present study, we investigated whether SGLT1 is up-regulated during traumatic brain injury (TBI) and whether removal of RS1 in mice (RS1-KO) influences SGLT1 expression and outcome. Unexpectedly, brain SGLT1 mRNA in RS1-KO was similar to wild-type whereas it was increased in small intestine and decreased in kidney. One day after TBI, SGLT1 mRNA in the ipsilateral cortex was increased 160% in wild-type and 40% in RS1-KO. After RS1 removal lesion volume 1 day after TBI was reduced by 12%, brain edema was reduced by 28%, and motoric disability determined by a beam walking test was improved. In contrast, RS1 removal did neither influence glucose and glycogen accumulation 1 day after TBI nor up-regulation of inflammatory cytokines TNF-α, IL-1β and IL-6 or microglia activation 1 or 5 days after TBI. The data provide proof of principle that inhibition or down-regulation of SGLT1 by targeting RS1 in brain could be beneficial for early treatment of TBI.

Lactate Shuttles in Neuroenergetics-Homeostasis, Allostasis and Beyond

Understanding brain energy metabolism—neuroenergetics—is becoming increasingly important as it can be identified repeatedly as the source of neurological perturbations. Within the scientific community we are seeing a shift in paradigms from the traditional neurocentric view to that of a more dynamic, integrated one where astrocytes are no longer considered as being just supportive, and activated microglia have a profound influence. Lactate is emerging as the “good guy,” contrasting its classical “bad guy” position in the now superseded medical literature. This review begins with the evolution of the concept of “lactate shuttles”; goes on to the recent shift in ideas regarding normal neuroenergetics (homeostasis)—specifically, the astrocyte–neuron lactate shuttle; and progresses to covering the metabolic implications whereby homeostasis is lost—a state of allostasis, and the function of microglia. The role of lactate, as a substrate and shuttle, is reviewed in light of allostatic stress, and beyond—in an acute state of allostatic stress in terms of physical brain trauma, and reflected upon with respect to persistent stress as allostatic overload—neurodegenerative diseases. Finally, the recently proposed astrocyte–microglia lactate shuttle is discussed in terms of chronic neuroinflammatory infectious diseases, using tuberculous meningitis as an example. The novelty extended by this review is that the directionality of lactate, as shuttles in the brain, in neuropathophysiological states is emerging as crucial in neuroenergetics.

Review: Traumatic brain injury and hyperglycemia, a potentially modifiable risk factor

Hyperglycemia after severe traumatic brain injury (TBI) occurs frequently and is associated with poor clinical outcome and increased mortality. In this review, we highlight the mechanisms that lead to hyperglycemia and discuss how they may contribute to poor outcomes in patients with severe TBI. Moreover, we systematically review the proper management of hyperglycemia after TBI, covering topics such as nutritional support, glucose control, moderated hypothermia, naloxone, and mannitol treatment. However, to date, an optimal and safe glycemic target range has not been determined, and may not be safe to implement among TBI patients. Therefore, there is a mandate to explore a reasonable glycemic target range that can facilitate recovery after severe TBI.

Role of Metabolomics in Traumatic Brain Injury Research

Metabolomics is an important member of the omics community in that it defines which small molecules may be responsible for disease states. This article reviews the essential principles of metabolomics from specimen preparation, chemical analysis, to advanced statistical methods. Metabolomics in traumatic brain injury has so far been underutilized. Future metabolomics-based studies focused on the diagnoses, prognoses, and treatment effects need to be conducted across all types of traumatic brain injury.

Cerebrospinal fluid in tuberculous meningitis exhibits only the L-enantiomer of lactic acid

Background

The defining feature of the cerebrospinal fluid (CSF) collected from infants and children with tuberculous meningitis (TBM), derived from an earlier untargeted nuclear magnetic resonance (NMR) metabolomics study, was highly elevated lactic acid. Undetermined was the contribution from host response (L-lactic acid) or of microbial origin (D-lactic acid), which was set out to be determined in this study.

Methods

In this follow-up study, we used targeted ultra-performance liquid chromatography–electrospray ionization–tandem mass spectrometry (UPLC–ESI–MS/MS) to determine the ratio of the L and D enantiomers of lactic acid in these CSF samples.

Results

Here we report for the first time that the lactic acid observed in the CSF of confirmed TBM cases was in the L-form and solely a response from the host to the infection, with no contribution from any bacteria. The significance of elevated lactic acid in TBM appears to be that it is a crucial energy substrate, used preferentially over glucose by microglia, and exhibits neuroprotective capabilities.

Conclusion

These results provide experimental evidence to support our conceptual astrocyte–microglia lactate shuttle model formulated from our previous NMR-based metabolomics study — highlighting the fact that lactic acid plays an important role in neuroinflammatory diseases such as TBM. Furthermore, this study reinforces our belief that the determination of enantiomers of metabolites corresponding to infectious diseases is of critical importance in substantiating the clinical significance of disease markers.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1597-9) contains supplementary material, which is available to authorized users.

Traumatic brain injury: pathophysiology for neurocritical care

Severe cases of traumatic brain injury (TBI) require neurocritical care, the goal being to stabilize hemodynamics and systemic oxygenation to prevent secondary brain injury. It is reported that approximately 45 % of dysoxygenation episodes during critical care have both extracranial and intracranial causes, such as intracranial hypertension and brain edema. For this reason, neurocritical care is incomplete if it only focuses on prevention of increased intracranial pressure (ICP) or decreased cerebral perfusion pressure (CPP). Arterial hypotension is a major risk factor for secondary brain injury, but hypertension with a loss of autoregulation response or excess hyperventilation to reduce ICP can also result in a critical condition in the brain and is associated with a poor outcome after TBI. Moreover, brain injury itself stimulates systemic inflammation, leading to increased permeability of the blood–brain barrier, exacerbated by secondary brain injury and resulting in increased ICP. Indeed, systemic inflammatory response syndrome after TBI reflects the extent of tissue damage at onset and predicts further tissue disruption, producing a worsening clinical condition and ultimately a poor outcome.

Elevation of blood catecholamine levels after severe brain damage has been reported to contribute to the regulation of the cytokine network, but this phenomenon is a systemic protective response against systemic insults. Catecholamines are directly involved in the regulation of cytokines, and elevated levels appear to influence the immune system during stress. Medical complications are the leading cause of late morbidity and mortality in many types of brain damage. Neurocritical care after severe TBI has therefore been refined to focus not only on secondary brain injury but also on systemic organ damage after excitation of sympathetic nerves following a stress reaction.

Should the neurointensive care management of traumatic brain injury patients be individualized according to autoregulation status and injury subtype?

INTRODUCTION

The status of autoregulation is an important prognostic factor in traumatic brain injury (TBI), and is important to consider in the management of TBI patients. Pressure reactivity index (PRx) is a measure of autoregulation that has been thoroughly studied, but little is known about its variation in different subtypes of TBI. In this study, we examined the impact of PRx and cerebral perfusion pressure (CPP) on outcome in different TBI subtypes.

METHODS

107 patients were retrospectively studied. Data on PRx, CPP, and outcome were collected from our database. The first CT scan was classified according to the Marshall classification system. Patients were assigned to "diffuse" (Marshall class: diffuse-1, diffuse-2, and diffuse-3) or "focal" (Marshall class: diffuse-4, evacuated mass lesion, and non-evacuated mass lesion) groups. 2 × 2 tables were constructed calculating the proportions of favorable/unfavorable outcome at different combinations of PRx and CPP.

RESULTS

Low PRx was significantly associated with favorable outcome in the combined group (p = 0.002) and the diffuse group (p = 0.04), but not in the focal group (p = 0.06). In the focal group higher CPP values were associated with worse outcome (p = 0.02). In diffuse injury patients with disturbed autoregulation (PRx >0.1), CPP >70 mmHg was associated with better outcome (p = 0.03).

CONCLUSION

TBI patients with diffuse injury may differ from those with mass lesions. In the latter higher levels of CPP may be harmful, possibly due to BBB disruption. In TBI patients with diffuse injury and disturbed autoregulation higher levels of CPP may be beneficial.

Lactate: brain fuel in human traumatic brain injury: a comparison with normal healthy control subjects

We evaluated the hypothesis that lactate shuttling helps support the nutritive needs of injured brains. To that end, we utilized dual isotope tracer [6,6-(2)H2]glucose, that is, D2-glucose, and [3-(13)C]lactate techniques involving arm vein tracer infusion along with simultaneous cerebral (arterial [art] and jugular bulb [JB]) blood sampling. Traumatic brain injury (TBI) patients with nonpenetrating brain injuries (n=12) were entered into the study following consent of patients' legal representatives. Written and informed consent was obtained from control volunteers (n=6). Patients were studied 5.7±2.2 (mean±SD) days post-injury; during periods when arterial glucose concentration tended to be higher in TBI patients. As in previous investigations, the cerebral metabolic rate for glucose (CMRgluc, i.e., net glucose uptake) was significantly suppressed following TBI (p<0.001). However, lactate fractional extraction, an index of cerebral lactate uptake related to systemic lactate supply, approximated 11% in both healthy control subjects and TBI patients. Further, neither the CMR for lactate (CMRlac, i.e., net lactate release), nor the tracer-measured cerebral lactate uptake differed between healthy controls and TBI patients. The percentages of lactate tracer taken up and released as (13)CO2 into the JB accounted for 92% and 91% for control and TBI conditions, respectively, suggesting that most cerebral lactate uptake was oxidized following TBI. Comparisons of isotopic enrichments of lactate oxidation from infused [3-(13)C]lactate tracer and (13)C-glucose produced during hepatic and renal gluconeogenesis (GNG) showed that 75-80% of (13)CO2 released into the JB was from lactate and that the remainder was from the oxidation of glucose secondarily labeled from lactate. Hence, either directly as lactate uptake, or indirectly via GNG, peripheral lactate production accounted for ∼70% of carbohydrate (direct lactate uptake+uptake of glucose from lactate) consumed by the injured brain. Undiminished cerebral lactate fractional extraction and uptake suggest that arterial lactate supplementation may be used to compensate for decreased CMRgluc following TBI.

Glycemia in Spontaneous Intracerebral Hemorrhage: Clinical Implications

Spontaneous cerebral hemorrhage or intracranial hemorrhage accounts for 10-15% of all strokes. Intracranial hemorrhage is much less common than ischemic stroke, but has higher mortality and morbidity, one of the leading causes of severe disability. Various alterations, among these the endocrine were identified when an intracerebral hemorrhage, these stress-mediated mechanisms exacerbate secondary injury. Deep knowledge of the injuries which are directly involved alterations of glucose, offers insight as cytotoxicity, neuronal death and metabolic dysregulations alter the prognosis of patients with spontaneous intracerebral hemorrhage.

A prospective, randomized Phase II clinical trial to evaluate the effect of combined hyperbaric and normobaric hyperoxia on cerebral metabolism, intracranial pressure, oxygen toxicity, and clinical outcome in severe traumatic brain injury

OBJECT

Preclinical and clinical investigations indicate that the positive effect of hyperbaric oxygen (HBO2) for severe traumatic brain injury (TBI) occurs after rather than during treatment. The brain appears better able to use baseline O2 levels following HBO2 treatments. In this study, the authors evaluate the combination of HBO2 and normobaric hyperoxia (NBH) as a single treatment.

METHODS

Forty-two patients who sustained severe TBI (mean Glasgow Coma Scale [GCS] score 5.7) were prospectively randomized within 24 hours of injury to either: 1) combined HBO2/NBH (60 minutes of HBO2 at 1.5 atmospheres absolute [ATA] followed by NBH, 3 hours of 100% fraction of inspired oxygen [FiO2] at 1.0 ATA) or 2) control, standard care. Treatments occurred once every 24 hours for 3 consecutive days. Intracranial pressure, surrogate markers for cerebral metabolism, and O2 toxicity were monitored. Clinical outcome was assessed at 6 months using the sliding dichotomized Glasgow Outcome Scale (GOS) score. Mixed-effects linear modeling was used to statistically test differences between the treatment and control groups. Functional outcome and mortality rates were compared using chi-square tests.

RESULTS

There were no significant differences in demographic characteristics between the 2 groups. In comparison with values in the control group, brain tissue partial pressure of O2 (PO2) levels were significantly increased during and following combined HBO2/NBH treatments in both the noninjured and pericontusional brain (p < 0.0001). Microdialysate lactate/pyruvate ratios were significantly decreased in the noninjured brain in the combined HBO2/NBH group as compared with controls (p < 0.0078). The combined HBO2/NBH group's intracranial pressure values were significantly lower than those of the control group during treatment, and the improvement continued until the next treatment session (p < 0.0006). The combined HBO2/NBH group's levels of microdialysate glycerol were significantly lower than those of the control group in both noninjured and pericontusional brain (p < 0.001). The combined HBO2/NBH group's level of CSF F2-isoprostane was decreased at 6 hours after treatment as compared with that of controls, but the difference did not quite reach statistical significance (p = 0.0692). There was an absolute 26% reduction in mortality for the combined HBO2/NBH group (p = 0.048) and an absolute 36% improvement in favorable outcome using the sliding dichotomized GOS (p = 0.024) as compared with the control group.

CONCLUSIONS

In this Phase II clinical trial, in comparison with standard care (control treatment) combined HBO2/NBH treatments significantly improved markers of oxidative metabolism in relatively uninjured brain as well as pericontusional tissue, reduced intracranial hypertension, and demonstrated improvement in markers of cerebral toxicity. There was significant reduction in mortality and improved favorable outcome as measured by GOS. The combination of HBO2 and NBH therapy appears to have potential therapeutic efficacy as compared with the 2 treatments in isolation. CLINICAL TRIAL REGISTRATION NO.: NCT00170352 (ClinicalTrials.gov).

Metabolomic analysis of cerebral spinal fluid from patients with severe brain injury

Proton nuclear magnetic resonance (H-NMR) spectroscopic analysis of cerebral spinal fluid provides a quick, non-invasive modality for evaluating the metabolic activity of brain-injured patients. In a prospective study, we compared the CSF of 44 TBI patients and 13 non-injured control subjects. CSF was screened for ten parameters: β-glucose (Glu), lactate (Lac), propylene glycol (PG), glutamine (Gln), alanine (Ala), α-glucose (A-Glu), pyruvate (PYR), creatine (Cr), creatinine (Crt), and acetate (Ace). Using mixed effects measures, we discovered statistically significant differences between control and trauma concentrations (mM). TBI patients had significantly higher concentrations of PG, while statistical trends existed for lactate, glutamine, and creatine. TBI patients had a significantly decreased concentration of total creatinine. There were no significant differences between TBI patients and non-injured controls regarding β- or α-glucose, alanine, pyruvate or acetate. Correlational analysis between metabolites revealed that the strongest significant correlations in non-injured subjects were between β- and α-glucose (r = 0.74), creatinine and pyruvate (r = 0.74), alanine and creatine (r = 0.62), and glutamine and α-glucose (r = 0.60). For TBI patients, the strongest significant correlations were between lactate and α-glucose (r = 0.54), lactate and alanine (r = 0.53), and α-glucose and alanine (r = 0.48). The GLM and multimodel inference indicated that the combined metabolites of PG, glutamine, α-glucose, and creatinine were the strongest predictors for CMRO2, ICP, and GOSe. By analyzing the CSF of patients with TBI, our goal was to create a metabolomic fingerprint for brain injury.

Angiopoietins as promising biomarkers and potential therapeutic targets in brain injury

Traumatic brain injury (TBI) and sub-arachnoid hemorrhage (SAH) are major causes of long-term disability, mortality, and enormous economic costs to society. The full spectrum of neurological damage created by TBI or SAH is not usually manifested at the time of injury, but evolves gradually over the course of hours to days (or weeks) following these injuries. Angiopoietins, important regulators of vascular structure and function, are hallmark indicators of vascular injury and may therefore represent promising targets in the treatment of SAH and TBI. In animal models and human tissues, normal intracerebral and pial vessels show strong expression of Angiopoietin-1 (Ang-1), but only minimal expression or presentation of Angiopoietin-2 (Ang-2). After several types of neurotrauma, the ratios of Ang-1 and Ang-2 expression in brain microvessel are disturbed and appear to contribute to the remarkable loss of blood-brain barrier (BBB) in these injuries. Angiopoietins levels, and perhaps more importantly, Angiopoietin ratios (1:2) may have novel and important diagnostic and prognostic uses in TBI and SAH brain injury. Ang-1/2 evaluation in plasma, serum and cerebrospinal fluid may provide new therapeutic modalities which can modify 'secondary' forms of brain injury after TBI and SAH.

Acute management of acquired brain injury part I: an evidence-based review of non-pharmacological interventions

PRIMARY OBJECTIVE

To review the literature on non-pharmacological interventions used in acute settings to manage elevated intracranial pressure (ICP) and minimize cerebral damage in patients with acquired brain injury (ABI).

MAIN OUTCOMES

A literature search of multiple databases (CINAHL, EMBASE, MEDLINE and PSYCHINFO) and hand-searched articles covering the years 1980-2008 was performed. Peer reviewed articles were assessed for methodological quality using the PEDro scoring system for randomized controlled trials (RCTs) and the Downs and Black tool for RCTs and non-randomized trials. Levels of evidence were assigned and recommendations made.

RESULTS

Five non-invasive interventions for acute ABI management were assessed: adjusting head posture, body rotation (continuous rotational therapy and prone positioning), hyperventilation, hypothermia and hyperbaric oxygen. Two invasive interventions were also reviewed: cerebrospinal fluid (CSF) drainage and decompressive craniectomy (DC).

CONCLUSIONS

There is a paucity of information regarding non-pharmacological acute management of patients with ABI. Strong levels of evidence were found for only four of the seven interventions (decompressive craniectomy, cerebrospinal fluid drainage, hypothermia and hyperbaric oxygen) and only for specific components of their use. Further research into all interventions is warranted.

Evidence of "regional hyperemia" in patients with severe closed head injury using single-photon emission computed tomography

Regional cerebral blood flow (rCBF) was assessed in 32 patients with acute/subacute (n = 18) or chronic (n = 14) head injury using single-photon emission computed tomography (SPECT) and (99m)Tc-hexamethylpropylenenamine oxime (HMPAO) (n = 20) or (123)I-IMP (n = 12). Twelve of the 18 patients with acute/subacute head injury were studied with a high-resolution three-head camera and (99m)Tc-HMPAO. Twenty-eight SPECT studies showed regional abnormalities of tracer uptake. In all cases in which computed tomography (CT) and/or magnetic resonance imaging (MRI) (n = 30) were available for comparison, SPECT showed similar or more extensive abnormalities with high agreement on the laterality of the lesions. Particularly in the 18 patients with acute/subacute head injury, SPECT revealed more and larger lesions than the anatomical scans. In 9 of the 12 patients, at least one region with increase in HMPAO uptake reflecting "hyperemia" was detected (mean study time after injury, 6.3 ± 2.7 days). Follow-up SPECT scans in two patients showed decreased tracer uptake in the previous hyperemic regions and encephalomalacia in the anatomical scan. Thus, hyperemia may reflect "luxury perfusion" in early phases of head injury. In three patients with diffuse axonal injury, a generalized reduction in cortical tracer activity, especially in occipital/parietal regions, was observed. The typical finding in chronic head injury was observation of lesions of similar sizes and high agreement in focal abnormalities between SPECT and CT and/or MRI. However, in nine patients with behavioral disturbances, a decrease in the cortical/basal ganglia was detected. Thus, our study confirms the presence of hyperemia in acute/subacute head injury and demonstrates the value of SPECT for assessing functional impairment in these patients.

A prospective, randomized clinical trial to compare the effect of hyperbaric to normobaric hyperoxia on cerebral metabolism, intracranial pressure, and oxygen toxicity in severe traumatic brain injury

Object

Oxygen delivered in supraphysiological amounts is currently under investigation as a therapy for severe traumatic brain injury (TBI). Hyperoxia can be delivered to the brain under normobaric as well as hyperbaric conditions. In this study the authors directly compare hyperbaric oxygen (HBO2) and normobaric hyperoxia (NBH) treatment effects.

Methods

Sixty-nine patients who had sustained severe TBIs (mean Glasgow Coma Scale Score 5.8) were prospectively randomized to 1 of 3 groups within 24 hours of injury: 1) HBO2, 60 minutes of HBO2 at 1.5 ATA; 2) NBH, 3 hours of 100% fraction of inspired oxygen at 1 ATA; and 3) control, standard care. Treatments occurred once every 24 hours for 3 consecutive days. Brain tissue PO2, microdialysis, and intracranial pressure were continuously monitored. Cerebral blood flow (CBF), arteriovenous differences in oxygen, cerebral metabolic rate of oxygen (CMRO2), CSF lactate and F2-isoprostane concentrations, and bronchial alveolar lavage (BAL) fluid interleukin (IL)–8 and IL-6 assays were obtained pretreatment and 1 and 6 hours posttreatment. Mixed-effects linear modeling was used to statistically test differences among the treatment arms as well as changes from pretreatment to posttreatment.

Results

In comparison with values in the control group, the brain tissue PO2 levels were significantly increased during treatment in both the HBO2 (mean ± SEM, 223 ± 29 mm Hg) and NBH (86 ± 12 mm Hg) groups (p < 0.0001) and following HBO2 until the next treatment session (p = 0.003). Hyperbaric O2 significantly increased CBF and CMRO2 for 6 hours (p ≤ 0.01). Cerebrospinal fluid lactate concentrations decreased posttreatment in both the HBO2 and NBH groups (p < 0.05). The dialysate lactate levels in patients who had received HBO2 decreased for 5 hours posttreatment (p = 0.017). Microdialysis lactate/pyruvate (L/P) ratios were significantly decreased posttreatment in both HBO2 and NBH groups (p < 0.05). Cerebral blood flow, CMRO2, microdialysate lactate, and the L/P ratio had significantly greater improvement when a brain tissue PO2 ≥ 200 mm Hg was achieved during treatment (p < 0.01). Intracranial pressure was significantly lower after HBO2 until the next treatment session (p < 0.001) in comparison with levels in the control group. The treatment effect persisted over all 3 days. No increase was seen in the CSF F2-isoprostane levels, microdialysate glycerol, and BAL inflammatory markers, which were used to monitor potential O2 toxicity.

Conclusions

Hyperbaric O2 has a more robust posttreatment effect than NBH on oxidative cerebral metabolism related to its ability to produce a brain tissue PO2 ≥ 200 mm Hg. However, it appears that O2 treatment for severe TBI is not an all or nothing phenomenon but represents a graduated effect. No signs of pulmonary or cerebral O2 toxicity were present.

Plasma glucose level in Nigerian Africans with head injury

Trauma is often associated with increased plasma glucose concentrations. This prospective study was designed to determine random plasma glucose concentrations in patients with head injury in our center and to determine if this is related to injury severity and outcome. Patients with head injury in whom the plasma glucose concentration could be determined at our accident and emergency unit during the study period were included. We obtained information on demographic data, diagnosis, injury severity using Glasgow Coma Scale scores, treatment with glucose-containing fluid prior to presentation in our center, plasma glucose on admission, 24 hours later and 72 hours later and outcome at discharge using the Glasgow Outcome Scale score. Hyperglycemia was defined as glucose concentrations above 11.1 mmol/L. Fifty eight patients were included in the study from October 2004 to December 2005. There were 46 males and 12 females (4:1). The mean age (+/- standard deviation [SD]) was 31.3 (16.4) years. Fourteen patients (24.1%) had mild head injury, 21 patients (36.2%) had moderate head injury and 23 patients (39.7%) had severe head injury. The outcome was good in 29 patients (50%), moderate disability in five patients (8.6%), severe disability in one (1.7%) and death in 10 (17.2%). Eighty percent of the patients who died had severe head injury. Most of the patients had a plasma glucose in the normal range irrespective of the severity of the head injury. Only one patient had a plasma glucose in the hyperglycemic range and that patient had a severe head injury. Fifty percent of the patients who died had a plasma glucose concentration in the normal range; none in the hyperglycemic range. This study shows that the plasma glucose is generally below hyperglycemic concentration in our patients irrespective of the severity of head injury.

A different view of lactate in trauma patients: protecting the injured brain

BACKGROUND

The relationship between lactate and head injury is controversial. We sought to determine the relationship between initial serum lactate, severity of head injury, and outcome. We hypothesized that lactate is elevated in head injured patients, and that initial serum lactate increases as the severity of head injury increases. Furthermore, lactate may be neuroprotective and improve neurologic outcomes.

MATERIALS AND METHODS

We identified normotensive adult patients over a 6-y period at our university-based urban trauma center with isolated blunt head injury. We performed univariate and multivariate analysis to examine the relationship between lactate and Glasgow coma scale (GCS). The correlation of admission lactate with survival and neurologic function was also examined.

RESULTS

There were 555 patients who met study criteria. While controlling for injury severity score and age, increased lactate was associated with more severe head injury (P<0.0001). The admission lactate was 2.2+/-0.07, 3.7+/-0.7, and 4.7+/-0.8 mmol/L in patients with mild, moderate, and severe head injury respectively (P<0.01). Patients with moderate or severe head injury and an admission lactate>5 were more likely to have a normal mental status on discharge (P<0.0001).

CONCLUSIONS

In normotensive isolated head injured patients, there was an increase in serum lactate as head injuries became more severe. Since lactate is a readily available fuel source of the injured brain, this may be a mechanism by which brain function is preserved in trauma patients. Elevations in lactate due to anaerobic metabolism in trauma patients may have beneficial effects by protecting the brain during injury.

Incidence and risk factors for perioperative hyperglycemia in children with traumatic brain injury

BACKGROUND

Hyperglycemia after traumatic brain injury (TBI) is associated with poor outcome. In this study, we examined the incidence and risk factors for perioperative hyperglycemia in children with TBI.

METHODS

A retrospective cohort study of children <or=13 yr who underwent urgent or emergent craniotomy for TBI at Harborview Medical Center (level I Adult and Pediatric Trauma Center) between 1994 and 2004 was performed. Preoperative (emergency department to general anesthesia start), intraoperative (during general anesthesia), and immediate postoperative (first 24 h after surgery) glucose values for each patient were retrieved. The incidence of hyperglycemia (glucose >or=200 mg/dL) and hypoglycemia (glucose <60 mg/dL) was determined. Persistent hyperglycemia was defined as hyperglycemia during any 2/3 (preoperative, intraoperative, and immediate postoperative) study periods, whereas transient hyperglycemia was defined as hyperglycemia during any one study period. Multivariate logistic regression analysis was used to determine the independent predictors of perioperative hyperglycemia. Data are presented as adjusted odds ratio (AOR) (95% CI) and P < 0.05 reflects significance.

RESULTS

At least one serum glucose value was recorded during each study period: preoperative (86 [82%]), intraoperative (94 [89%]), and postoperative (101 [97%]). Sixty-four percent of children had less than one glucose recorded per anesthetic hour. Forty-seven (45%) children had hyperglycemia during at least one study period. Transient hyperglycemia occurred in 29 (28%) and persistent hyperglycemia occurred in 18 (17%) children. Independent predictors of perioperative hyperglycemia were age <4 yr (AOR [95% CI]; 3.5 [1.2-10.6]), Glasgow Coma Scale <or=8 (AOR 95% CI; 7.2 [2.4-21.5]) and the presence of multiple lesions including subdural hematoma (AOR 95% CI; 34.7 [2.3-525.5]). Six children were treated with insulin, and two children had hypoglycemia, unrelated to insulin treatment.

CONCLUSIONS

Perioperative hyperglycemia was common and intraoperative hypoglycemia was not rare, but more frequent intraoperative glucose sampling may be needed to better determine the incidence of hypo and hyperglycemia during the perioperative period. Age <4 yr, severe TBI and the presence of multiple lesions, including subdural hematoma, were risk factors for perioperative hyperglycemia.

Intensive glycemic control in traumatic brain injury: what is the ideal glucose range?

Intensive glycemic control has become standard practice. Existing data, however, suggest this practice may have adverse consequences for traumatic brain injury. The recent paper by Meier and colleagues suggests that intensive glycemic control may be deleterious. The present article explores existing literature surrounding this controversy, and outlines the literature that raises concern. Finally, I suggest an alternative course of action that may enable control of glucose in an optimal range.

Hyperbaric oxygen therapy for consciousness disturbance following head injury in subacute phase

BACKGROUND

Hyperbaric oxygen (HBO) therapy has been shown to improve outcome after brain injury, however its mechanisms are not understood. The purpose of the present study was to investigate the effect of hyperbaric oxygen (HBO) therapy on the cerebral circulation and metabolism of patients with disturbances in consciousness after head injury in the subacute phase.

METHODS

Seven head injury patients underwent HBO treatment after leaving the intensive care unit. Oxygen (100% O2, 2.7 atm absolute) was delivered to patients in a hyperbaric chamber for 60 min every 24 h (total five treatments/patient). Cerebral circulation monitoring (mean flow velocity: mFV, and pulsatility index: PI at horizontal portion of middle cerebral artery by transcranial Doppler) and cerebral metabolism monitoring (arterio-jugular venous difference of oxygen: AJDO2 and jugular venous lactate: lac-JV) before and after the series of treatments were evaluated.

FINDINGS

Both PI and lac-JV were significantly decreased after HBO theatment, while there were no significant changes in mFV and AJDO2. The decreased PI and lac-JV after HBO therapy might indicate that this treatment couples cerebral circulation and metabolism.

CONCLUSIONS

The measurement of cerebral circulation and metabolism parameters, especially PI and lac-JV, is useful for estimation of effect of HBO therapy in patients with distubances in consciousness after head injury in the subacute phase.

Hyperbaric oxygen in traumatic brain injury

OBJECTIVES

This critical literature review examines historical and current investigations on the efficacy and mechanisms of hyperbaric oxygen (HBO) treatment in traumatic brain injury (TBI). Potential safety risks and oxygen toxicity, as well as HBO's future potential, are also discussed.

METHODS

Directed literature review.

RESULTS

Historically, cerebral vasoconstriction and increased oxygen availability were seen as the primary mechanisms of HBO in TBI. HBO now appears to be improving cerebral aerobic metabolism at a cellular level, namely, by enhancing damaged mitochondrial recovery. HBO given at the ideal treatment paradigm, 1.5 ATA for 60 minutes, does not appear to produce oxygen toxicity and is relatively safe.

DISCUSSION

The use of HBO in TBI remains controversial. Growing evidence, however, shows that HBO may be a potential treatment for patients with severe brain injury. Further investigations, including a multicenter prospective randomized clinical trial, will be required to definitively define the role of HBO in severe TBI.

Identifying traumatic brain injury in patients with isolated head trauma: are arterial lactate and base deficit as helpful as in polytrauma?

BACKGROUND

Increase in lactate (LAC) within the central nervous system after head trauma is an established marker of traumatic brain injury (TBI).

OBJECTIVE

To investigate the utility of arterial base deficit (BD) and LAC in identifying TBI in patients with isolated head injury (IHI).

MATERIALS AND METHODS

TBI was defined as Glasgow Coma Scale < or =8, head Abbreviated Injury Severity Score >2 or brain haematoma on CT scan. Patients were divided into two groups: IHI with and without TBI. Data were reported as means (SDs). 131 patients with IHI were studied (mean (SD) age 39 (19) years, 78% male).

RESULTS

17% of the patients sustained TBI. The mean differences for arterial BD (0.65 mmol/l, 95% CI -0.8 to 2.1) and LAC (0.34 mmol/l, 95% CI -0.7 to 1.4) in patients with and without TBI were not significant. Analysis of receiver operating characteristic curves confirmed that arterial BD and LAC were unable to detect TBI in patients with IHI.

CONCLUSION

Arterial BD and LAC are poor predictors of TBI in isolated head trauma.

Current concepts of cerebral oxygen transport and energy metabolism after severe traumatic brain injury

Before energy metabolism can take place, brain cells must be supplied with oxygen and glucose. Only then, in combination with normal mitochondrial function, sufficient energy (adenosine tri-phosphate (ATP)) can be produced. Glucose is virtually the sole fuel for the human brain. The brain lacks fuel stores and requires a continuous supply of glucose and oxygen. Therefore, continuous cerebral blood flow (CBF), cerebral oxygen tension and delivery, and normal mitochondrial function are of vital importance for the maintenance of brain function and tissue viability. This review focuses on three main issues: (1) Cerebral oxygen transport (CBF, and oxygen partial pressure (PO2) and delivery to the brain); (2) Energy metabolism (glycolysis, mitochondrial function: citric acid cycle and oxidative phosphorylation); and (3) The role of the above in the pathophysiology of severe head injury. Basic understanding of these issues in the normal as well as in the traumatized brain is essential in developing new treatment strategies. These issues also play a key role in interpreting data collected from monitoring techniques such as cerebral tissue PO2, jugular bulb oxygen saturation (SjvO2), near infra red spectroscopy (NIRS), microdialysis, intracranial pressure monitoring (ICP), laser Doppler flowmetry, and transcranial Doppler flowmetry--both in the experimental and in the clinical setting.

Hyperglycemia Has a Stronger Relation with Outcome in Trauma Patients than in Other Critically Ill Patients

BACKGROUND

Acute hyperglycemia is associated with adverse outcome in critically ill patients. Glucose control with insulin improves outcome in surgical intensive care unit (SICU) patients, but the effect in trauma patients is unknown. We investigated hyperglycemia and outcome in SICU patients with and without trauma.

METHODS

A 12-year retrospective study was performed at a 12-bed SICU. We collected the reason for admission, Injury Severity Scores (ISS), and 30-day mortality rates. Glucose measurements were used to calculate the hyperglycemic index (HGI), a measure indicative of overall hyperglycemia during the entire SICU stay.

RESULTS

In all, 5234 nontrauma and 865 trauma patients were studied. Trauma patients were younger, more frequently male, and had both lower median admission glucose (123 versus 133 mg/dL) and HGI levels (8.9 vs. 18.4 mg/dL) than nontrauma patients (p < 0.001). Mortality was 12% in both groups. Area under the receiver-operator characteristic for HGI and mortality was 0.76 for trauma patients and 0.58 for nontrauma patients (p < 0.001). In multivariate analysis, HGI correlated better with mortality in trauma patients than in nontrauma patients (p < 0.001). Head-injury and nonhead-injury trauma patients showed similar glucose levels and relation between glucose and mortality.

CONCLUSIONS

The relation of hyperglycemia and mortality is more pronounced in trauma patients than in SICU patients admitted for other reasons. The different behavior of hyperglycemia in these patients underscores the need for evaluation of intensive insulin therapy in these patients.

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

OBJECTIVE

To determine that intensive glycemic control does not reduce microdialysis glucose concentration brain metabolism of glucose.

DESIGN

Prospective monitoring followed by retrospective data analysis of cerebral microdialysis and global brain metabolism.

SETTING

Single center, academic neurointensive care unit.

PATIENTS

Forty-seven moderate to severe traumatic brain injury patients.

INTERVENTIONS

A nonrandomized, consecutive design was used for glycemic control with loose insulin (n=33) for the initial 2 yrs or intensive insulin therapy (n=14) for the last year.

MEASUREMENTS AND MAIN RESULTS

In 14 patients treated with intensive insulin therapy, there was a reduction in microdialysis glucose by 70% of baseline concentration compared with a 15% reduction in 33 patients treated with a loose insulin protocol. Despite this reduction in microdialysis glucose, the global metabolic rate of glucose did not change. However, intensive insulin therapy was associated with increased incidence of microdialysis markers of cellular distress, namely elevated glutamate (38+/-37% vs. 10+/-17%, p<.01), elevated lactate/pyruvate ratio (38+/-37% vs. 19+/-26%, p<.03) and low glucose (26+/-17% vs. 11+/-15%, p<.05, and increased global oxygen extraction fraction. Mortality was similar in the intensive and loose insulin treatment groups (14% vs. 15%, p=.9), as was 6-month clinical outcome (p=.3).

CONCLUSIONS

Intensive insulin therapy results in a net reduction in microdialysis glucose and an increase in microdialysis glutamate and lactate/pyruvate without conveying a functional outcome advantage.

Hyperglycemia and Brain Tissue pH after Traumatic Brain Injury

OBJECTIVE

Hyperglycemia occurring after head injury is associated with poor neurological outcome. We tested the hypothesis that blood glucose levels are associated with brain tissue pH (pH(b)) and that the correction of hyperglycemia would result in an improvement in pH(b).

METHODS

This is a retrospective analysis of a prospectively collected database. Thirty-four patients in a tertiary care neuroscience critical care unit with major traumatic brain injury underwent pH(b) monitoring.

RESULTS

A total of 428 glucose measurements were recorded during pH(b) monitoring. Mean glucose level was 7.1 mmol/L (range, 2.8-21.7 mmol/L) and median (interquartile range) pH(b) was 7.11 mmol/L (7.00-7.19 mmol/L). To account for the correlated, unbalanced nature of the data, a linear generalized estimating equation model was created. This model predicted that for each 1 mmol/L increase in blood glucose, pH(b) changed by -0.011 mmol/L (95% confidence interval, -0.016 to -0.005 mmol/L; P < 0.001). This relationship remained significant in a multivariable model that included cerebral perfusion pressure, brain tissue oxygen and carbon dioxide tension, and brain temperature. Twenty-one episodes of significant hyperglycemia (>or=11.1 mmol/L) treated with intravenous insulin were identified. Insulin therapy significantly reduced blood glucose concentration from a median (interquartile range) of 11.9 mmol/L (range, 11.4-13.6 mmol/L) to 8.8 mmol/L (range, 7.3-9.6 mmol/L; P < 0.001). Baseline pH(b) was not significantly different from pH(b) associated with the subsequent glucose reading of less than 11.1 mmol/L (P = 0.29), but there was a suggestion of improvement if the change in blood glucose was large.

CONCLUSION

Blood glucose is associated with brain tissue acidosis in patients with major head injury. Prospective studies are required to confirm these results and to determine whether treatment of hyperglycemia improves outcome.

Assessment of jugular blood oxygen and lactate indices for detection of cerebral ischemia and prognosis

Levels of jugular blood oxygen saturation (SjvO2) and lactate have been proposed as indicators of cerebral ischemia and prognosis. However, sensitivity and specificity of these markers remain unknown. We retrospectively analyzed records of a series of 43 comatose patients at risk for cerebral ischemia, mainly after head injuries or subarachnoidal hemorrhage. Their SjvO2, jugulo-arterial lactate difference (VADLactate), and lactate-oxygen index (LOI) were determined every 8 hours. An increase in VADLactate and LOI was found, indicative of ischemia on CT scan, with threshold values of 0.30 mmol/L and 0.15, respectively. Sensitivity and specificity were 100% and 64%, respectively, for the VADLactate threshold, and 90% and 55%, respectively, for the LOI threshold. Regarding prediction of a poor outcome, only an increase in VADLactate had a predictive value with a sensitivity of 100% and specificity of 67%. No threshold value with sufficient sensitivity and specificity was found for SjvO2, as indicator of either ischemia or outcome. During progression to brain death, VADLactate and LOI reached abnormal levels earlier than cerebral perfusion pressure or SjvO2. They reacted markedly to focal ischemia due to vasospasm. Hyperlactacidemia rendered VADLactate and LOI uninterpretable by causing a brain lactate influx. Present data, if confirmed by a prospective study, would justify inclusion of intermittent VADLactate and LOI determinations in the multimodal cerebral monitoring.

Arterio-Jugular Difference of Oxygen Content and Outcome After Head Injury

This study investigated AJDO2 (arterio-jugular difference of oxygen content) in a large sample of severely head-injured patients to identify its pattern during the first days after injury and to describe the relationship of AJDO2 with acute neurological severity and with outcome 6 mo after trauma. In 229 comatose head-injured patients, we monitored intracranial pressure, cerebral perfusion pressure, and AJDO2. Outcome was defined 6 mo after injury. Jugular hemoglobin oxygen saturation (SjO2) averaged 68%. The mean AJDO2 was 4.24 vol% (SD, 1.3 vol%). There were 80 measurements (4.6%) with SjO2 <55% and 304 (17.6%) with saturation >75%. AJDO2 was higher than 8.7 vol% in 8 measurements (0.4%) and was lower than 3.9 vol% in 718 (42%) measurements. AJDO2 was higher during the first tests and decreased steadily over the next few days. Cases with a favorable outcome had a higher mean AJDO2 (4.3 vol%; SD, 0.3 vol%) than patients with severe disability or vegetative status (3.8 vol%; SD, 1.3 vol%) and patients who died (3.6 vol%; SD, 1 vol%). This difference was significant (P < 0.001). We conclude that low levels of AJDO2 are correlated with a poor prognosis, whereas normal or high levels of AJDO2 are predictive of better results.

Effect of Gamma-Hydroxybutyric Acid on Lipid Peroxidation and Tissue Lactate Level in Experimental Head Trauma

BACKGROUND

This study was designed to determine the effects of gamma-hydroxybutyric acid (GHB) on tissue lactate and malondialdehyde (MDA) levels in rabbit brain after experimental head trauma.

METHODS

Thirty New Zealand rabbits were divided equally into three groups: group S was the sham-operated group, group C, and group GHB received head trauma, where group C was the untreated and group GHB was the treated group. Head trauma was delivered by performing a craniectomy over the right hemisphere and dropping a weight of 10 g from a height of 80 cm. GHB was administered 400 mg/kg intravenously for 10 minutes after the head trauma to group GHB. The nontraumatized side was named "1" and the traumatized side was named "2." One hour after trauma, brain cortices were resected from both sides and the concentrations of lactate and MDA were determined.

RESULTS

There were significant differences between lactate and MDA levels of group S and all other groups (C1, C2, GHB1, and GHB2) except between lactate levels of group S and group GHB1, the nontraumatized and traumatized sides of groups C and group GHB, group C2 versus group GHB2, and group C1 versus group GHB1 (p < 0.05). Rectal temperature after the administration of GHB in group GHB was found lower than in groups S and C (p < 0.05).

CONCLUSION

These results demonstrate that head trauma leads to an increase in brain tissue lactate and MDA levels, and GHB effectively suppresses the increase of lactate and MDA.

Lack of improvement in cerebral metabolism after hyperoxia in severe head injury: a microdialysis study

OBJECT

The authors investigated the effects of hyperoxia on brain tissue PO2 and on glucose metabolism in cerebral and adipose tissue after traumatic brain injury (TBI).

METHODS

After 3 hours of ventilation with pure O2, 18 tests were performed on different days in eight comatose patients with TBI. Lactate, pyruvate, glucose, glutamate, and brain tissue PO2 were measured in the cerebral extracellular fluid (ECF) by using microdialysis. Analytes were also measured in the ECF of abdominal adipose tissue. After 3 hours of increase in the fraction of inspired O2, brain tissue PO2 rose from the baseline value of 32.7 +/- 18 to 122.6 +/- 45.2 mm Hg (p < 0.0001), whereas brain lactate dropped from its baseline (3.21 +/- 2.77 mmol/L), reaching its lowest value (2.90 +/- 2.58 mmol/L) after 3 hours of hyperoxia (p < 0.01). Pyruvate dropped as well, from 153 +/- 56 to 141 +/- 56 micromol/L (p < 0.05), so the lactate/pyruvate ratio did not change. No significant changes were observed in glucose and glutamate. The arteriovenous difference in O2 content dropped, although not significantly, from a baseline of 4.52 +/- 1.22 to 4.15 +/- 0.76 m/100 ml. The mean concentration of lactate in adipose tissue fell significantly as well (p < 0.01), but the lactate/pyruvate ratio did not change.

CONCLUSIONS

Hyperoxia slightly reduced lactate levels in brain tissue after TBI. The estimated redox status of the cells, however, did not change and cerebral O2 extraction seemed to be reduced. These data indicate that oxidation of glucose was not improved by hyperoxia in cerebral and adipose tissue, and might even be impaired.

Delayed changes in regional brain energy metabolism following cerebral concussion in rats

Traumatic brain injury (TBI) results in an acute altered metabolic profile of brain tissue which resolves within hours of initial insult and yet some of the functional deficits and cellular perturbations persist for days. It is hypothesized that a delayed change in energy status does occur and is a factor in the neural tissue's ability to survive and regain function. Regional metabolic profile and glucose consumption were determined at either 1 or 3 days following two different intensities of parasagittal fluid-percussion (F-P). A significant decrease in both 1CMRgluc and levels of ATP and P-creatine was evident in the hemisphere ipsilateral to the trauma at 1 day after the insult. The effect was greater in the cortical than the subcortical regions and was more pronounced at the higher trauma intensity. Normalization of glucose consumption and energy levels was essentially complete by 3 days. It would appear that the delayed metabolic changes at 1 day postinsult cannot be explained by a secondary ischemia since the changes in the metabolite profile do not elicit an increase in the consumption of glucose. These changes in energy metabolites may account for and contribute to the chronic neurological deficits following TBI.

Increased adenosine in cerebrospinal fluid after severe traumatic brain injury in infants and children: association with severity of injury and excitotoxicity

OBJECTIVES

To measure adenosine concentration in the cerebrospinal fluid of infants and children after severe traumatic brain injury and to evaluate the contribution of patient age, Glasgow Coma Scale score, mechanism of injury, Glasgow Outcome Score, and time after injury to cerebrospinal fluid adenosine concentrations. To evaluate the relationship between cerebrospinal fluid adenosine and glutamate concentrations in this population.

DESIGN

Prospective survey.

SETTING

Pediatric intensive care unit in a university-based children's hospital.

PATIENTS

Twenty-seven critically ill infants and children who had severe traumatic brain injury (Glasgow Coma Scale < 8), who required placement of an intraventricular catheter and drainage of cerebrospinal fluid as part of their neurointensive care.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients ranged in age from 2 months to 14 yrs. Cerebrospinal fluid samples (n = 304) were collected from 27 patients during the first 7 days after traumatic brain injury. Control cerebrospinal fluid samples were obtained from lumbar puncture on 21 infants and children without traumatic brain injury or meningitis. Adenosine concentration was measured by using high-pressure liquid chromatography. Adenosine concentration was increased markedly in cerebrospinal fluid of children after traumatic brain injury vs. controls (p < .001). The increase in cerebrospinal fluid adenosine was independently associated with Glasgow Coma Scale < or = 4 vs. > 4 and time after injury (both p < .005). Cerebrospinal fluid adenosine concentration was not independently associated with either age (< or = 4 vs. > 4 yrs), mechanism of injury (abuse vs. other), or Glasgow Outcome Score (good/moderately disabled vs. severely disabled, vegetative, or dead). Of the 27 patients studied, 18 had cerebrospinal fluid glutamate concentration previously quantified by high-pressure liquid chromatography. There was a strong association between increases in cerebrospinal fluid adenosine and glutamate concentrations (p < .005) after injury.

CONCLUSIONS

Cerebrospinal fluid adenosine concentration is increased in a time- and severity-dependent manner in infants and children after severe head injury. The association between cerebrospinal fluid adenosine and glutamate concentrations may reflect an endogenous attempt at neuroprotection against excitotoxicity after severe traumatic brain injury.

Effects of nimodipine on tissue lactate and malondialdehyde levels in experimental head trauma

We studied the effects of nimodipine on brain tissue lactate and malondialdehyde (MDA) levels one hour after experimental head trauma in 25 New Zealand rabbits. Group 1 (n=5) was the sham operated group. Group 2 (n=10) received head trauma without treatment and in group 3 (n=10) nimodipine was administered for 30 minutes intravenously (2 microg/kg/min) immediately after head trauma. In groups 2 and 3, tissue samples from the non-traumatized side was named as "a" and traumatized side as "b". The lactate and malondialdehyde contents were significantly higher in groups 2a, 2b, 3a and 3b when compared with to group 1 (P<0.05). The differences between non-treated groups (2a, 2b) and nimodipine treated groups (3a, 3b) were not significant (P>0.05). The differences between the traumatized sides (2b, 3b) and non-traumatized sides (2a, 3a) were significant (P<0.05). These results demonstrated that nimodipine is ineffective in suppressing the increase of tissue lactate and malondialdehyde levels in the early period of experimental head trauma.

Alterations in cerebral energy metabolism induced by traumatic brain injury

Energy metabolism of the brain is unique, possessing high aerobic metabolism with no significant capacity for anaerobic glycolysis and limited tissue stores of glucose. A steady supply of oxygen and glucose is essential in order to maintain cerebral function and integrity. Extensive research in experimental and human head injury has been conducted regarding the delivery of oxygen and outcome. This research has provided evidence which indicates that in addition to the availability of oxygen and glucose, other factors, such as perturbation of mitochondrial energy transducing processes which also follow head trauma, play significant roles. In this paper, the salient findings from biochemical studies of experimental and clinical brain injury are summarized and indicate that the mitochondrial respiratory chain-linked oxidative phosphorylation and calcium transport are compromised by trauma-induced brain injury and support the idea that oxidative stress and perturbation of cellular calcium homeostasis play significant roles in traumatic brain injury.

Effects of hyperbaric oxygenation therapy on cerebral metabolism and intracranial pressure in severely brain injured patients

OBJECT

Hyperbaric oxygenation (HBO) therapy has been shown to reduce mortality by 50% in a prospective randomized trial of severely brain injured patients conducted at the authors' institution. The purpose of the present study was to determine the effects of HBO on cerebral blood flow (CBF), cerebral metabolism, and intracranial pressure (ICP), and to determine the optimal HBO treatment paradigm.

METHODS

Oxygen (100% O2, 1.5 atm absolute) was delivered to 37 patients in a hyperbaric chamber for 60 minutes every 24 hours (maximum of seven treatments/patient). Cerebral blood flow, arteriovenous oxygen difference (AVDO2), cerebral metabolic rate of oxygen (CMRO2), ventricular cerebrospinal fluid (CSF) lactate, and ICP values were obtained 1 hour before and 1 hour and 6 hours after a session in an HBO chamber. Patients were assigned to one of three categories according to whether they had reduced, normal, or raised CBF before HBO. In patients in whom CBF levels were reduced before HBO sessions, both CBF and CMRO2 levels were raised 1 hour and 6 hours after HBO (p < 0.05). In patients in whom CBF levels were normal before HBO sessions, both CBF and CMRO2 levels were increased at 1 hour (p < 0.05), but were decreased by 6 hours after HBO. Cerebral blood flow was reduced 1 hour and 6 hours after HBO (p < 0.05), but CMRO2 was unchanged in patients who had exhibited a raised CBF before an HBO session. In all patients AVDO2 remained constant both before and after HBO. Levels of CSF lactate were consistently decreased 1 hour and 6 hours after HBO, regardless of the patient's CBF category before undergoing HBO (p < 0.05). Intracranial pressure values higher than 15 mm Hg before HBO were decreased 1 hour and 6 hours after HBO (p < 0.05). The effects of each HBO treatment did not last until the next session in the hyperbaric chamber.

CONCLUSIONS

The increased CMRO2 and decreased CSF lactate levels after treatment indicate that HBO may improve aerobic metabolism in severely brain injured patients. This is the first study to demonstrate a prolonged effect of HBO treatment on CBF and cerebral metabolism. On the basis of their data the authors assert that shorter, more frequent exposure to HBO may optimize treatment.

Impaired cerebral mitochondrial function after traumatic brain injury in humans

OBJECT

Oxygen supply to the brain is often insufficient after traumatic brain injury (TBI), and this results in decreased energy production (adenosine triphosphate [ATP]) with consequent neuronal cell death. It is obviously important to restore oxygen delivery after TBI; however, increasing oxygen delivery alone may not improve ATP production if the patient's mitochondria (the source of ATP) are impaired. Traumatic brain injury has been shown to impair mitochondrial function in animals; however, no human studies have been previously reported.

METHODS

Using tissue fractionation procedures, living mitochondria derived from therapeutically removed brain tissue were analyzed in 16 patients with head injury (Glasgow Coma Scale Scores 3-14) and two patients without head injury. Results revealed that in head-injured patients mitochondrial function was impaired, with subsequent decreased ATP production.

CONCLUSIONS

Decreased oxygen metabolism due to mitochondrial dysfunction must be taken into account when clinically defining ischemia and interpreting oxygen measurements such as jugular venous oxygen saturation, arteriovenous difference in oxygen content, direct tissue oxygen tension, and cerebral blood oxygen content determined using near-infrared spectroscopy. Restoring mitochondrial function might be as important as maintaining oxygen delivery.

Role of glycemia in acute spinal cord injury. Data from a rat experimental model and clinical experience

While experimental and clinical evidence indicates that in brain injury blood glucose increases with injury severity and hyperglycemia worsens neurological outcome, the role of blood glucose in secondary mechanisms of neuronal damage after acute spinal cord injury has not yet been investigated. Data from spinal cord ischemia models suggests a deleterious effect of hyperglycemia, likely due to enhanced lactic acidosis, which is primarily dependent on the amount of glucose available to be metabolized. The purpose of this study is to summarize preliminary experimental and clinical observations on the role of blood glucose in acute spinal cord injury. Between 1995 and 1996 we used the New York University (NYU) rat spinal cord injury model to test the following hypotheses: 1) Blood glucose levels increase with injury severity. 2) Fasting protects from hyperglycemia and prevents secondary damage to the spinal cord. 3) Postinjury-induced hyperglycemia (dextrose 5% 2 gm/Kg) enhances spinal lesion volume. From a clinical perspective, we reviewed blood glucose records of 47 patients admitted to the Department of Neurosrgery in Verona, between 1991 and 1995, within 24 hours of acute spinal cord injury in order to determine: a) the incidence of hyperglycemia (> 140 mg/dl); b) the correlation between blood glucose and injury severity; and c) the role of methylprednisolone in affecting blood glucose. Results indicate that in a graded spinal cord injury model: 1) Early after injury, more severe contusions support significantly higher blood glucose levels. 2) Fasting overnight does not directly affect spinal cord lesion volume but influences blood gases, and we observed that a slightly systemic acidosis plays a minor neuroprotective role. Fasting also ensures more consistent normoglycemic baseline blood glucose values. 3) Postinjury-induced moderate hyperglycemia (160-190 mg/dl) does not significantly affect spinal cord injury. In the clinical study, we observed that during the first 24 hours after spinal cord injury: a) Glycemia ranges between 90 and 243 mg/dl (mean value 143 mg/dl), and close to 50% of the patients present blood glucose values higher than normal. b) Methylprednisolone administration is not associated to significantly higher blood glucose levels. c) There is a trend for larger glucose rises with more severe injury.

The influence of hyperglycemia on neurological outcome in patients with severe head injury

OBJECTIVE

Traumatic brain injury is associated with a stress response that includes hyperglycemia, which has been shown to worsen neurological outcome during cerebral ischemia and hypoxia. To better examine the relationship between hyperglycemia and outcome after head injury, we studied the clinical course of 267 head-injured patients who were admitted for treatment in the neurosurgical department of Asclepeion Hospital of Athens between January 1993 and November 1997.

METHODS

We prospectively studied 267 patients with moderate or severe craniocerebral injury (Glasgow Coma Scale scores, 3-12) who were treated surgically for evacuation of an intracranial hematoma and/or placement of a device for intracranial pressure monitoring under general anesthesia to determine the relationship between serum glucose levels, severity of injury, and neurological outcome.

RESULTS

Patients with severe head injury had significantly higher serum glucose levels than did those with moderate injury. Patients who subsequently had an unfavorable outcome had significantly higher glucose levels than did those with a better prognosis. Among the patients with more severe head injury, a glucose level greater than 200 mg/dl was associated with a worse outcome. In the same group of patients, a significant relationship was found between postoperative glucose levels, pupillary reaction, and maximum intracranial pressure during the first 24 hours. Multivariate analysis showed that postoperative glucose levels were an independent predictor of outcome.

CONCLUSION

Early hyperglycemia is a frequent component of the stress response to head injury, a significant indicator of its severity, and a reliable predictor of outcome.