Effect of Mechanogated Membrane Ion Channel Blockers on Experimental Traumatic Brain Oedema

Summary Traumatic head injury leads to marked swelling of endothelial cells, both in human patients and in Marmarou's rat model. We used this model to test the hypothesis of mechanogated ion channels being involved in the formation of traumatic brain oedema. All mechanogated channel blockers tested (gadolinium, amiloride, gentamicin) significantly reduced traumatic brain oedema evaluated by Evans blue extraction ratio, either when given 15 minutes before or 30 minutes after induction of trauma (evaluation 2 hours after trauma). These results clearly support our hypothesis, opening a new way for the investigation of the treatment of a clinical situation endowed with high morbidity and mortality.     

Influence of Aging on Blood-Brain Barrier Permeability and Free Radical Formation Following Experimental Brain Cold Injury

Summary.  The aim of this study is to investigate the effects of experimental cold brain injury on blood-brain barrier integrity, on brain oedema formation, and on lipid peroxidation and to compare the results between the aged and young rats. Cold brain injury was used to create a standard model of brain trauma in old and young rats. Disruption of the blood-brain barrier was analyzed by Evans blue method. The values of cerebral water content were calculated by using the fresh and dry weights of the cerebral hemispheres. Lipid peroxidation was assessed by measuring the tissue content of malonyl dialdehyde.  Blood-brain barrier was destroyed significantly in young and old rats, but it was more severe in old rats. Accordingly, cerebral water content was increased in both groups, however this increase was significantly more prominent in old rats. No significant difference was found on malonyl dialdehyde levels between young and old rats.  The blood-brain barrier was more easily disrupted in old rats, and this was supposed to be the basic event causing more secondary damage.     

Protective Effect of the N-Methyl-D-Aspartate Receptor Antagonists, MK-801 and CPP on Cold-Induced Brain Oedema

Summary  Cold injury model in rat was used to determine the effect of treatment with the competitive NMDA antagonists CPP and the non-competitive NMDA antagonist MK-801 in cerebral oedema. MK-801 was applied in doses of 1 mg/kg and CPP of 10 mg/kg, 15 min. after injury. Control animals received 1 ml saline at the same time interval after injury. Tissue samples from the core and periphery of the lesion of the injured hemisphere and from the symmetrical location of the undamaged contralateral hemisphere were removed 24 hours after injury. Blood brain barrier permeability, brain water content and tissue specific gravity values were determined. MK-801 was found beneficial for reducing the oedema and restore the blood brain barrier permeability at the penumbral zone of the lesion, whereas both MK-801 and CPP were found ineffective for prevention of oedema accumulation at the core of the lesion.     

The effect of intraventricular albumin in experimental brain oedema

Summary Therapy for vasogenic brain oedema (VBE) is still an unsolved problem. Experimental work with the aim of establishing an oncotherapeutic option is presented.VBE is performed by focal freeze injury in rats. Using a stereotactic head holder hypo- or hyperosmolar human serum albumin is administered via the intraventricular route. The goal is to enhance the migration of oedema fluid with the aid of oncotic pressures. Early and late results are obtained for each group respectively four and twenty-four hours after the infliction of cold injury. The efficacy of therapy is evaluated by cerebrospinal fluid (CSF) osmolality, cerebral water content, tissue specific gravity, and blood-brain barrier (BBB) permeability. Posttherapeutic values for CSF osmolality are obtained by cisterna magna puncture.Hyperosmolar CSF after performance of cold injury (p < 0.05) is thought to be a result of fluid accumulation in the traumatized region partially from the intraventricular space. Posttherapeutic values after hyperosmolar albumin administration have revealed iso-osmolar CSF, increase in specific gravity (p < 0.001), and decrease in BBB permeability (p < 0.05). These results are in accordance with withdrawal of oedema fluid into the ventricles which can be interpreted as a positive therapeutic effect. Late results in hyperosmolar group have disclosed a hypo-iso-osmolar CSF, persistent increase in specific gravity, and no regression. These values have shown that hyperosmolar albumin administration does not interfere with CSF circulation. Early results of hypo-osmolar albumin application are discouraging.This preliminary work of a therapeutic trial on VBE may be a basis for future investigations with different dosages and time modalities.     

Technical Note: A new Model for Quantitative Analysis of Brain Oedema Resolution Into the Ventricles and the Subarachnoid Space

Summary  Objective. The aim of the current study was to develop an experimental animal model for quantitative analysis of oedema resolution via the subarachnoid space and the ventricular system using fluorescent oedema markers.  Methods. Artificial cerebrospinal fluid (CSF) containing TRITC-albumin (MW 67.000D) and Na⁺-fluorescein (MW 376D) was continuously infused into the white matter of the left frontal lobe of New Zealand white rabbits (n=6) at a rate of 100 μl/h for 3 hrs. A closed cranial window for superfusion of the brain surface with artificial CSF fluid (3 ml/h) was implanted above the left parietal cortex for measurement of the fluorescence markers in the subarachnoid space. Uptake of the fluorescence indicators into the ventricles was quantified by ventriculo-cisternal perfusion (3 ml/h). The effluates were collected at 30 min intervals for 3 hrs after the start of infusion. Clearance of the oedema fluid into the perfusates was measured by fluorescence spectrophotometry.  Results. At an intracranial pressure of 15.0±1.7 mm Hg (mean±SEM) both indicators started to accumulate in the subarachnoid and ventricular perfusates at 90 min following onset of oedema fluid infusion. The concentrations of the indicators in the ventricular system increased to 7.7±5.1% of Na⁺-fluorescein and 16.1±13.0% of TRITC-albumin of the total amount infused were recovered in the ventricular system at 3 hours after start of the oedema infusion, while 3.4±3.2% of Na⁺-fluorescein and 3.7%± 3.2 of TRITC-albumin, respectively, were found in the effluates of the subarachnoid space.  Conclusion. The present study demonstrates that resolution of vasogenic brain oedema into the cerebral ventricular system and the subarachnoid space following its entry into cerbral white matter can be quantitatively analysed using fluorescence markers, which serve as oedema fluid indicators. The results indicate that the oedema fluid is cleared not only into the ventricular system but also via the subarachnoid space.     

The importance of protein content in the Oedema fluid for the resolution of brain Oedema

Summary The infusion model of oedema is developed in the rat. Unilateral, constant volume, intracerebral infusions of oedema fluid of varying protein (bovine albumin) concentrations are performed. Brain tissue is analyzed for water content using the gravimetric technique. The authors find significant differences in the spatial distribution of brain water in the different infusion groups at 48 and 72 hours post infusion. The control infusate (mock cerebrospinal fluid) clears by 72 hours. However, infusates containing protein (32.5 and 65.0mg/ml albumin) are not completely cleared until 5 to 8 days post infusion, with the less concentrated solution clearing more rapidly in the area of infusion at 72 and 96 hours post infusion. The data support the hypothesis that the rate of clearance of vasogenic brain oedema is dependent on the amount of extravasated protein.This work was supported by NIH Grant 5RO1NS19235-03.     

Fast in Vivo Water Quantification in Rat Brain Oedema Based on T<Subscript>1</Subscript> Measurement at High Magnetic Field

Summary. Summary.   Background: In vivo water content determination based on magnetic resonance (MR) method is of importance in clinical practice as well as in animal studies to follow up the treatment given in order to reduce brain oedema. The methods proposed in the literature so far are largely time consuming. The aim of this study was to find a fast in vivo water quantification method having real advantage for patients suffering from critical conditions.   Method: Cold injury was applied to provoke brain oedema in fourteen rats. T₁ values of both the oedematous area and the contralateral normal cortex were determined by two independent methods 24 hours after the cold impact. First, from a series of images recorded by inversion recovery spin echo (IRSE) sequence and then by progressive saturation experiment performed by localised MR spectroscopy using stimulated echo acquisition mode (STEAM). To reduce the acquisition time, a two-element repetition time array was optimised for the STEAM experiment, whereas four inversion times were used for T₁ mapping. Both methods were validated against gel phantoms with known T₁ values. After the MR measurements the animals were sacrificed and the water contents of the regions of interest were determined by gravimetric wet-dry method.   Findings: The reciprocals of the in vivo measured T₁ values were correlated with the reciprocals of the brain water contents. STEAM experiment showed stronger correlation (r=0.96) than IRSE (r=0.93). In addition, STEAM provided more accurate T₁ values in the phantom study. Determination of brain water content based on T1 measurement does work also at high magnetic field. Determination of brain water content by Magnetic Resonance Spectroscopy is feasible within 2 minutes.   Interpretation: Using the presented fast method, water content can be determined within a couple of minutes in animal experiments as well as in the daily clinical practice. Published online August 12, 2002     

Behavioural and Morphological Outcome of Mild Cortical Contusion Trauma of the Rat Brain: Influence of NMDA-Receptor Blockade

Summary  The authors studied the effect of a mild cortical contusion to the rat brain on behavioural and morphological outcome and the influence of NMDA-receptor blockade (MK-801, 0.5 mg/kg i.v. 30 min prior to trauma). Spontaneous motor activity was assessed 16–18 days post trauma. Saline treated traumatised rats showed a significant (p<0.01) hyperactive behaviour compared to animals without injury. MK-801 treated rats performed significantly better than the saline treated animals (p<0.05). For histopathological evaluation hippocampal hilar neurons were counted, cortical thickness under the impact was measured and microtubule-associated protein 2 (MAP2) immunoreactivity in the dentate hilus was quantified 1, 3 and 21 days post trauma. In traumatised rats scattered loss of nerve cells, oedema and minute haemorrhages were present at the site of the impact one and three days after injury. At day 21 there was a significant reduction of cortical thickness at the site of impact. One day after trauma there was a bilateral, significant loss of neurons and MAP2 immunostaining in the dentate hilus of the hippocampus. MK-801 pretreated rats showed similar morphological changes. The disturbed spontaneous motor behaviour may be caused by hippocampal damage and a reduction of somatosensory cortical neurons. NMDA-receptor blockade improved the outcome assessed by the functional tests but failed to influence the morphological changes, suggesting that this behavioural test is a more sensitive indicator of outcome after mild traumatic brain injury (TBI).     

A New and Easier Way to Anastomose Microvessels: An Experimental Study in Rats

A new technique for microvascular anastomosis, telescoping one vessel into the other requiring only 2 sutures, is described. In 28 arterial and 15 venous anastomoses no failures were seen as recorded 3 weeks postoperatively by micro dissection, micro angiography, light microscopy and scanning electron microscopy. It is concluded, from this experimental study in rats, that the new anastomosis is faster and easier to perform and at least as reliable as the conventional end to end anastomosis.     

Angiogenesis and Brain Oedema in Intracranial Meningiomas: Influence of Vascular Endothelial Growth Factor

Summary The correlation between angiographic neovascularization, peritumoural brain oedema (PTBOe) and the expression of vascular endothelial growth factor (VEGF) , was analysed in 30 patients with intracranial meningiomas. Pre-operative angiograms were examined for the existence of either an exclusively dural tumour blush or an additionally pial tumour supply from cerebral arteries. Furthermore the presence of macroscopic tumour-neovascularization and dysplastic changes of tumour-draining cerebral veins was evaluated. VEGF expression was investigated on histological tissue samples, using immunohistochemical techniques. VEGF immunohistochemistry and neuroradiological evaluations were performed in double blind fashion. Tumour volume and the amount of oedema were calculated by computerized tomography (CT) or magnetic resonance imaging (MRI). The oedema-tumour volume ratio was defined as oedema index (OeI). Compared to VEGF-negative meningiomas, tumours with striking VEGF staining revealed a significant higher mean oedema index (OeI=4,2 vs. OeI=1,5; p<0.018), and a higher oedema incidence (91,7% vs. 44,4%; p<0.046). Equally, meningiomas with additionally tumour supply from cerebral arteries were associated with a significant higher mean OeI (OeI=4.1 vs. OeI=1.2; p<0.01) and oedema incidence (94,7% vs. 20,0%; p<0,0023) than meningiomas with exclusively tumour supply from dural arteries. All meningiomas with striking VEGF-expression were associated with vascular tumour supply from cerebral arteries, but VEGF-negative tumours only in 50% (p<0.029). These data suggest a link between VEGF-expression, arterial tumour supply and peritumoural brain oedema. The development of tumour supply from cerebral arteries may be important for formation of meningioma-related oedema. Therefore, VEGF may represent a potent mediator in the evolution of this type of vascularization in meningiomas.     

Traumatic Brain Contusions: A Clinical Role for the Kinin Antagonist CP-0127

Summary  Focal cerebral contusions can be dynamic and expansive, leading to delayed neurological deterioration. Due to the high mortality associated with such cerebral contusions, our standard practice had evolved into evacuating contusions in patients who had a deterioration in level of consciousness, lesions>30 cc and CT suggestion of raised ICP. Experimental brain edema studies have implicated kinins in causing 2° brain swelling. CP-0127 (Bradycor ^TM), a specific bradykinin antagonist, has been found to reduce cerebral edema in a cold lesion model in rats. In a randomized, single blind pilot study, a 7 day infusion of CP-0127 (3.0 ug/kg/min) was compared to placebo in patients with focal cerebral contusions presenting within 24–96 hours of closed head injury with an initial GCS 9–14. The ICP, GCS, and vital signs were monitored hourly. The total lesion burden (TLB) was measured on serial CT scans.  There were no differences in age, baseline GCS, TLB, initial ICP, or laboratory findings between the two groups (n=20). The mean (±s.d) rise in peak ICP from baseline was greater in the placebo group than with CP-0127 (21.9±4.7 vs 9.5±2.0, P=0.018). In addition, the mean reduction in GCS in the placebo group was significantly greater than in the CP-0127 group (4±1.0 vs 0.6±0.4, P=0.002). Significantly raised ICP and clinically significant neurological deterioration occurred in 7/9 patients on placebo (77%) and only in 1 patient (9%; n=11) on CP-0127, mandating surgery (P=0.005). There were no adverse drug reactions, significant changes in vital signs or variations in the laboratory values. The cerebral perfusion pressure was adequately maintained in all patients irrespective of therapy.  These preliminary results with CP-0127 provide supporting evidence that the kinin-kallikrein system could be involved in cerebral edema. In this study, treatment with CP-0127 appeared to alter the natural history of traumatic brain contusions by preventing the 2° brain swelling. In addition, CP-0127 obviated the need for surgery in the majority of treated patients. CP-0127 could act on the cerebral vasculature to limit dys-autoregulation and brain swelling or on the blood brain barrier to reduce cerebral edema.     

Correlations Between Brain Tissue Oxygen Tension, Carbon Dioxide Tension, pH, and Cerebral Blood Flow-A Better Way of Monitoring The Severely Injured Brain?

Background

The ideal method for monitoring the acutely injured brain would measure substrate delivery and brain function continuously, quantitatively, and sensitively. We have tested the hypothesis that brain pO₂, pCO₂, and pH, which can now be measured continuously using a single sensor, are valid indicators of regional cerebral blood flow (CBF) and oxidative metabolism, by measuring its product, brain pCO₂.

Methods

Twenty-five patients (Glasgow Coma Score ≤ 8) were studied. A Clark electrode, combined with a fiber optic system (Paratrend 7, Biomedical Sensors, Malvern, PA) was used to measure intraparenchymal brain pO₂, pCO₂, and pH. Data were averaged over a 1-h period before and after CBF studies. Regional CBF was measured around the probe, using stable xenon computed tomography. Regression analyses and Spearman Rank tests were used for data analysis.

Results

Regional CBF and mean brain pO₂ were strongly correlated (r = 0.74, p = 0.0001). CBF values < 18 mL/100 g/min were all accompanied by brain pO₂ ≤ 26 mm Hg. The four patients with a brain pO₂ < 18 mm Hg died. Brain pCO₂ and pH, however, were not correlated with CBF (r = 0.36, p = 0.24 and r = 0.30, p = 0.43, respectively).

Conclusions

Until recently, substrate supply to the severely injured brain could only be intermittently estimated by measuring CBF. The excellent intra-regional correlation between CBF and brain pO₂, suggests that this method does allow continuous monitoring of true substrate delivery, and offers the prospect that measures to increase O₂ delivery (e.g., increasing CBF, CPP, perfluorocarbons etc.) can be reliably tested by brain pO₂ monitoring.     

Brain swelling and brain oedema in acute head injury

Summary Chronological changes in diffuse brain swelling and brain oedema were studied in repeated CT studies following a closed head injury. These findings were compared with changes in intracranial pressure (ICP). The grades of diffuse brain swelling were classified into mild, moderate and marked according to the CT findings. Planimetry of low density areas of brain oedema was carried out on repeated CT images. Diffuse brain swelling was recognized in 71 of patients shortly after the head injury and subsided within days 3–5. Brain oedema first appeared 24 hours post injury and did not reach its maximum size and distribution before days 5–8. Thus, these two events can be clearly separated. The intracranial pressure reflected the course of the brain swelling and was not very high during the presence of maximum oedema.     

Brain death and intraocular pressure

The authors report on the behavior of the intraocular pressure of 20 patients who had sustained severe head injury. The 8 patients who retained normal intraocular pressure all survived. The 12 patients who developed intraocular hypotony all suffered brain death. Although optic disc edema was not noted in any brain-dead patients, we did find signs of fundus ischemia in most.     

Cerebral physiological and biochemical changes during vasogenic brain oedema induced by intrathecal injection of bacterial lipopolysaccharides in piglets

Summary. Summary.   Background: The objective of the study was to evaluate biochemical and physiological changes in an experimental model of vasogenic brain oedema utilising techniques also used in routine neuro-intensive care.   Method: 32 piglets were randomised to control or experimental group. The latter received an intrathecal injection of lipopolysaccharide (LPS) from E.coli (LPS group). Intracranial pressure (ICP) and mean arterial pressure (MAP) were measured continuously. Intracerebral microdialysis was used for analysing interstitial levels of glucose, pyruvate, lactate, glutamate, glycerol and urea every 30 min. Repeated calculations of mean hemispheric CBF were performed utilising an extra-cranial scintillation detector and intracarotid injection of ¹³³Xe. Cerebral specific gravity was measured and the brains were fixed for histological examinations.   Findings: After LPS injection ICP increased reaching a plateau phase after 4–7 hours and CBF increased by 46%. Histological examination showed inflammation with pronounced extravasation of granulocytes. A significant decrease in brain specific gravity (p= 0.022) was obtained. LPS caused a significant decrease in cerebral interstitial concentration of glucose (p=0.0035), and significant increases in lactate concentration (p=0.002) and lactate/pyruvate ratio (p=0.0017). A small but significant increase in glutamate was obtained (p=0.0219). Glycerol did not change significantly.   Interpretation: Intrathecal LPS caused an inflammatory reaction with extravasation of granulocytes, increased blood-brain barrier permeability and cerebral oedema. Biochemical analyses indicate increased glycolysis but no signs of cell membrane degradation. Published online June 20, 2002     

Pupillary Abnormality on Admission and Brain Bulging During Surgery as Unfavourable Predictors in Patients Treated with Hypothermia: A Retrospective Review of 81 Patients with Severe Head Injury

Summary. Background: To determine factors predicting outcome of patients with severe head injury, the authors retrospectively analyzed 81 patients, 3 to 70 years of age, who were treated by hypothermia. Method: The initial Glasgow Coma Scale scores of the 81 patients ranged from 3 to 8. Outcome in each case was determined at six months after injury and was retrospectively analyzed with respect to patient characteristics, initial clinical status, laboratory data, computed tomographic findings, data from monitoring, intra-operative findings, and treatment methods. The significance of clinical and neuroradiological factors for predicting unfavorable outcome was analyzed by univariate logistic regression. Stepwise multiple logistic regression analysis was then used to identify independent predictors of outcome. Findings: Favorable outcome was observed in 27 of 81 patients treated by hypothermia. Independent factors predicting unfavorable outcome included pupillary abnormality on admission and brain bulging during surgery. Interpretation: Therapeutic effectiveness of hypothermia was thus limited in patients who presented with these grave symptoms.     

Traumatic brain swelling studied by computerized tomography and densitometry

Two-hundred and fifty-two computerized tomography (CT) scans of 107 patients with head injuries were analyzed. The most frequent consequence of trauma was a diffuse swelling of the brain in 91% of the cases. The severity of brain swelling and its course can be estimated by the compression of (or absence of) the intracranial cerebrospinal fluid space. These observations may be of prognostic value as well.By measurement of theHounsfield units (HU) in 52 cases the blood or water content in the brain tissues was assessed. An increase in blood content of the tissues (hyperaemia) can account for an increase in Hounsfield values. A decrease in HU suggests brain edema.The density measurements showed that in the first hours and days following head injury, the diffuse brain swelling was caused by severe cerebrovascular congestion in the majority (53%) of the cases. Immediate brain edema without a preceeding hyperaemic phase occurs less frequently (32%).Between the 1st and 4th day after injury, edema started to prevail, and between the 5th and 8th day the edematous type of brain swelling was present almost exclusively.     

The Role of Neuroinflammation in Traumatic Brain Injury

Abstract In industrialized countries, traumatic brain injury (TBI) still represents the leading cause of death and persisting neurologic impairment among young individuals < 45 years of age. Patients who survive the initial injury are susceptible to sustaining secondary cerebral insults which are initiated by the release of neurotoxic and inflammatory endogenous mediators by resident cells of the central nervous system (CNS). The presence of hypoxia and hypotension in the early resuscitative period further aggravates the inflammatory response due to ischemia/reperfusion-mediated injuries. These are induced by the intrathecal generation of free radicals and activation of the complement cascade. Posttraumatic neuroinflammation is further exacerbated by the subsequent intracranial recruitment of blood-derived immunocompetent cells, leading to secondary cerebral edema and increased intracranial pressure. The profound endogenous neuroinflammatory response after TBI, which is phylogenetically aimed at defending the CNS from invading pathogens and repairing lesioned tissue, is, in large part, responsible for the development of secondary brain damage and adverse outcome. However, aside from these deleterious effects, posttraumatic inflammation mediates neuroreparative mechanisms after TBI as well. This dual effect of neuroinflammation has been the focus of extensive experimental and clinical research in the past years and has led to an expanded basic knowledge on the cellular and molecular mechanisms which regulate the intracranial inflammatory response after trauma. The present article provides an up-to-date overview on the pathophysiological mechanisms of neuroinflammation after TBI. New potential therapeutic strategies for reducing the extent of secondary brain damage after neurotrauma are discussed.