Effect of indomethacin pretreatment on acute mortality in experimental brain injury

Therapies targeting lipid peroxidation in traumatic brain injury

Lipid peroxidation can be broadly defined as the process of inserting a hydroperoxy group into a lipid. Polyunsaturated fatty acids present in the phospholipids are often the targets for peroxidation. Phospholipids are indispensable for normal structure of membranes. The other important function of phospholipids stems from their role as a source of lipid mediators - oxygenated free fatty acids that are derived from lipid peroxidation. In the CNS, excessive accumulation of either oxidized phospholipids or oxygenated free fatty acids may be associated with damage occurring during acute brain injury and subsequent inflammatory responses. There is a growing body of evidence that lipid peroxidation occurs after severe traumatic brain injury in humans and correlates with the injury severity and mortality. Identification of the products and sources of lipid peroxidation and its enzymatic or non-enzymatic nature is essential for the design of mechanism-based therapies. Recent progress in mass spectrometry-based lipidomics/oxidative lipidomics offers remarkable opportunities for quantitative characterization of lipid peroxidation products, providing guidance for targeted development of specific therapeutic modalities. In this review, we critically evaluate previous attempts to use non-specific antioxidants as neuroprotectors and emphasize new approaches based on recent breakthroughs in understanding of enzymatic mechanisms of lipid peroxidation associated with specific death pathways, particularly apoptosis. We also emphasize the role of different phospholipases (calcium-dependent and -independent) in hydrolysis of peroxidized phospholipids and generation of pro- and anti-inflammatory lipid mediators. This article is part of a Special Issue entitled SI:Brain injury and recovery.

Traumatic injury to the immature brain: inflammation, oxidative injury, and iron-mediated damage as potential therapeutic targets

Traumatic brain injury (TBI) is the leading cause of morbidity and mortality among children and both clinical and experimental data reveal that the immature brain is unique in its response and vulnerability to TBI compared to the adult brain. Current therapies for pediatric TBI focus on physiologic derangements and are based primarily on adult data. However, it is now evident that secondary biochemical perturbations play an important role in the pathobiology of pediatric TBI and may provide specific therapeutic targets for the treatment of the head-injured child. In this review, we discuss three specific components of the secondary pathogenesis of pediatric TBI-- inflammation, oxidative injury, and iron-induced damage-- and potential therapeutic strategies associated with each. The inflammatory response in the immature brain is more robust than in the adult and characterized by greater disruption of the blood-brain barrier and elaboration of cytokines. The immature brain also has a muted response to oxidative stress compared to the adult due to inadequate expression of certain antioxidant molecules. In addition, the developing brain is less able to detoxify free iron after TBI-induced hemorrhage and cell death. These processes thus provide potential therapeutic targets that may be tailored to pediatric TBI, including anti-inflammatory agents such as minocycline, antioxidants such as glutathione peroxidase, and the iron chelator deferoxamine.

The ability of paramedics to predict aspiration in patients undergoing prehospital rapid sequence intubation

One of the purported benefits to invasive prehospital airway management is the prevention of aspiration; however, aspiration events may occur before the arrival of prehospital personnel. We explore the timing of aspiration in patients with severe traumatic brain injury (TBI) undergoing paramedic rapid sequence intubation (RSI). Severely head-injured (Glasgow Coma Scale [GCS] score 3-8) adults were prospectively enrolled into the San Diego Paramedic RSI Trial. As part of the prehospital data collection tool, paramedics prospectively assessed for clinical evidence of aspiration before RSI (pre-intubation), aspiration events occurring during RSI (peri-RSI), and regurgitation of vomitus or blood after intubation (post-intubation). Data were abstracted from work sheets used during the RSI procedure, a telephone debriefing by one of the principal investigators immediately after delivery of the patient, and San Diego County prehospital and trauma databases. The incidence of pre-intubation aspiration, peri-RSI aspiration, and post-intubation regurgitation of vomitus or blood were determined. Patients with and without pre-intubation aspiration were compared with regard to pre- and post-intubation hypoxia and the rate of aspiration pneumonia. Logistic regression was used to explore the association between pre-intubation aspiration and various demographic and clinical factors. The results showed that pre-intubation aspiration was noted by paramedics in 72/269 patients in whom complete data were available. Peri-RSI aspiration was reported in one patient; there were no reported cases of post-intubation regurgitation of vomitus or blood. Patients in the pre-intubation aspiration group required more intubation attempts, had a higher incidence of desaturations and lower pre- and post-intubation SaO(2) values, and were more frequently diagnosed with aspiration pneumonia. Pre-intubation aspiration was associated with severe TBI, GCS score of 3, younger age, and the absence of alcohol intoxication despite controlling for age, gender, GCS, Head AIS (Abbreviated Injury Score), and serum ethanol. It is concluded that paramedics seem to be able to accurately assess for aspiration in patients undergoing prehospital RSI. The vast majority of aspiration events seem to occur before the arrival of prehospital personnel. Alteration in consciousness from TBI may carry a higher risk of aspiration than with other causes, such as alcohol intoxication.

Intracranial pressure response to severe head injury induced apnea and catecholamine surge

BACKGROUND

Apnea and catecholamine surge have been known sequelae in the first few minutes of postexperimentally induced severe head injury for over a century. However, the intracranial pressure (ICP) response to these two pathophysiologic processes is poorly understood.

METHODS

We used the rat fluid percussion head injury model to study apnea and catecholamine surge separately and in combination on measured ICP response

RESULTS

The three experimental groups of apnea, hypertensive surge, and both combined revealed significantly different ICP responses with markedly elevated pressures correlating closely with mean arterial blood pressure.

CONCLUSION

ICP and mean arterial blood pressure correlate closely in the first few minutes after head injury in the absence of space-occupying hematomas, and may initiate pathophysiologic sequelae that can only be treated by earlier medical intervention at the scene.

Cyclooxygenase inhibition as a strategy to ameliorate brain injury

Cyclooxygenase (COX) is the obligate, rate-limiting enzyme for the conversion of arachidonic acid into prostaglandins. Two COX enzymes have been identified: a constitutively expressed COX-1 and an inducible, highly regulated COX-2. Widely used to treat chronic inflammatory disorders, COX inhibitors have shown promise in attenuating inflammation associated with brain injury. However, the use of COX inhibition in the treatment of brain injury has met with mixed success. This review summarizes our current understanding of COX expression in the central nervous system and the effects of COX inhibitors on brain injury. Three major targets for COX inhibition in the treatment brain injury have been identified. These are the cerebrovasculature, COX-2 expression by vulnerable neurons, and the neuroinflammatory response. Evidence suggests that given the right treatment paradigm, COX inhibition can influence each of these three targets. Drug interactions and general considerations for administrative paradigms are also discussed. Although therapies targeted to specific prostaglandin species, such as PGE2, might prove more ameliorative for brain injury, at the present time non-specific COX inhibitors and COX-2 specific inhibitors are readily available to researchers and clinicians. We believe that COX inhibition will be a useful, ameliorative adjunct in the treatment of most forms of brain injury.

Activation of cyclo-oxygenase-2 contributes to motor and cognitive dysfunction following diffuse traumatic brain injury in rats

1. Post-traumatic inflammation may play a significant role in the development of delayed secondary brain damage following traumatic brain injury. 2. During post-traumatic inflammation, metabolic products of arachidonic acid, known as prostanoids (prostaglandins and thromboxanes) are released and aggravate the injury process. Prostanoid synthesis is regulated by the enzyme cyclo-oxygenase (COX), which is present in at least two isoforms, COX-1 (the constitutive form) and COX-2 (the inducible form). 3. In the present study, we examine the temporal and spatial profiles of COX-2 expression and the effects of the COX-2 inhibitor nimesulide on motor and cognitive outcome following diffuse traumatic brain injury in rats. 4. Adult male Sprague-Dawley rats were injured using the 2 m impact acceleration model of diffuse traumatic brain injury. At preselected time points after injury, animals were killed and the expression of COX-2 was measured in the cortex and hippocampus by western blotting techniques. 5. Increased expression of COX-2 was found in the cortex at 3 days and in the hippocampus as early as 3 h postinjury and this persisted for at least 12 days. 6. Administration of nimesulide (6 mg/kg, i.p.) at 30 min after injury and daily over a 10 day post-traumatic neurological assessment period resulted in a significant improvement compared with vehicle (2% dimethylsulphoxide diluted in isotonic saline)-treated controls in cognitive deficits, as assessed by the Barnes circular maze. There was also a significant improvement in motor dysfunction as assessed by the rotarod test on days 1 and 2 post-trauma compared with vehicle-treated controls. 7. These results implicate the involvement of COX-2 in cognitive and motor dysfunction following diffuse traumatic brain injury.

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

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

Effects of ethanol on brain lactate in experimental traumatic brain injury with hemorrhagic shock

OBJECTIVE

Previous studies of traumatic brain injury (TBI) and hemorrhagic shock (HS) models, have shown cardiorespiratory depression in ethanol-treated animals. This study investigated the effects of ethanol (ET) on brain lactate concentrations and acidosis in a TBI/HS model.

METHODS

Anesthetized swine were instrumented and subjected to injury (INJ) consisting of fluid percussion TBI of 3 atm with concurrent 30 ml/kg graded hemorrhage over 30 min. Three groups were studied: Sham, INJ and INJ/ET. ET was given preinjury as a 2-g/kg i.v. bolus over 30 min, and an infusion of 0.4 g kg(-1) h(-1). Cardiorespiratory and cerebral physiologic data were monitored continuously for 150 min postinjury. Cerebral and renal blood flow was measured with colored microspheres. Brains were frozen in situ with liquid nitrogen. Lactate was measured with an enzymatic method.

RESULTS

ET levels at injury were 219+/-24 mg/dl. The INJ/ET group had increased mortality, impaired ventilation, and reduced renal blood flow. Brain (cortical) lactate levels were significantly higher and cerebral venous lactate concentrations were increased in the INJ/ET group during the postinjury period. Cerebral venous glucose was significantly higher in the INJ/ET group, and cerebral venous pH was significantly lower.

CONCLUSION

In this TBI/HS model, ethanol-induced increases in lactate concentrations in brain tissue and cerebral venous blood are associated with respiratory depression and reduced organ blood flow.

Acute ethanol intoxication in a model of traumatic brain injury with hemorrhagic shock: effects on early physiological response

OBJECT

Traumatic brain injury (TBI) is exacerbated by hypotension and hypoventilation. Because previous studies have shown a potentiating effect of ethanol (EtOH) on TBI and hemorrhagic shock (HS), the authors investigated the effects of EtOH on the early physiological response to TBI with and without HS.

METHODS

Anesthetized swine, weighing approximately 20 kg each, underwent fluid-percussion TBI of 3 atm with or without 30 ml/kg hemorrhage for a period of 30 minutes. The mean arterial blood pressure, intracranial pressure, cerebral perfusion pressure (CPP), cardiac output, cerebral venous oxygen saturation, and metabolic parameters were monitored for 3 hours postinjury. Ventilation and the response to hypercapnia were also measured. Regional cerebral blood flow and renal blood flow were measured using dye-labeled microspheres. Five groups were studied: control, TBI, TBI/EtOH, TBI/HS, and TBI/HS/EtOH. The EtOH (3.5 g) was given intragastrically 100 minutes preinjury. The TBI/HS/EtOH group demonstrated a 3-hour mortality rate of 56% and postinjury apnea requiring ventilation in 44% of animals compared with 0% in all other groups. Minute ventilation and the hypercapnic ventilatory response were significantly reduced in the postinjury period in the TBI/HS/EtOH group. The animals in this group had significantly lower CPP and cardiac output in the first 60 minutes postinjury, as well as lower renal and cerebral blood flow. Postinjury cerebral venous lactate levels were higher, and cerebral venous pH was lower in the TBI/HS/EtOH group.

CONCLUSIONS

In this model of TBI, acute EtOH intoxication in the presence of HS potentiates the physiological and metabolic alterations that may contribute to secondary brain injury.

Effects of ethanol in an experimental model of combined traumatic brain injury and hemorrhagic shock

OBJECTIVES

Given that clinical and laboratory studies suggest that ethanol and hemorrhagic shock (HS) potentiate traumatic brain injury (TBI), the authors studied the effects of ethanol in a model of combined TBI and HS.

METHODS

A controlled porcine model of combined TBI and HS was evaluated for the effect of ethanol on survival time, hemodynamic function, and cerebral tissue perfusion. Anesthetized swine (17-24 kg) were instrumented, splenectomized, and subjected to fluid percussion TBI with concurrent 25-mL/kg graded hemorrhage over 30 minutes. Two groups were studied: control (n = 11) and ethanol (n = 11). Ethanol, 3.5 g/kg intragastric, was given 100 minutes prior to TBI/HS. Systemic and cerebral physiologic and metabolic parameters were monitored for 2 hours without resuscitation. Regional cerebral blood flow (rCBF) and renal blood flow were measured with dye-labeled microspheres. Data were analyzed with 2-sample t-test and repeated-measures ANOVA.

RESULTS

Ethanol levels at the time of injury were 162 +/- 68 mg/dL. Average TBI was 2.65 +/- 0.35 atm. Survival time was significantly shorter in the ethanol group (60 +/- 27 min vs 94 +/- 28 min, p = 0.011). The ethanol group had significantly lower mean arterial pressure, cerebral perfusion pressure, and cerebral venous O2 saturation in the postinjury period. Cerebral O2 extraction ratios and cerebral venous lactate levels were significantly higher in the ethanol group. A trend toward lower postinjury rCBF in all brain regions was observed in the ethanol group.

CONCLUSION

In this TBI/HS model, ethanol administration decreased survival time, impaired the hemodynamic response, and worsened measures of cerebral tissue perfusion.

Inhibition of NMDA-induced increase in brain temperature by N-omega-nitro-L-arginine and indomethacin in rats

Intracerebroventricular administration of N-methyl-D-aspartate (NMDA) caused an increase in brain temperature, which appeared rapidly and preceded that in rectal temperature, in urethane-anesthetized rats. The increase in brain temperature was divided into two phases, an early increase and a late increase. Intracerebroventricular indomethacin, a cyclooxygenase inhibitor, completely abolished the NMDA-induced late increase, but not the early increase, in brain temperature. On the other hand, intracerebroventricular N-omega-nitro-L-arginine, a potent inhibitor of nitric oxide synthase, strongly suppressed both the early and the late increases. These findings suggest that both nitric oxide and prostaglandins may be involved in the increase in brain temperature after NMDA receptor activation.

Alcohol, central nervous system injury, and time to death in fatal motor vehicle crashes

OBJECTIVES

Motor vehicle crash (MVC) studies have found that alcohol (ALC) is associated with increased mortality and decreased time to death (TTD). Clinical and experimental data suggest that ALC potentiates central nervous system injury (CNSI). We hypothesize that ALC-intoxicated, MVC fatalities with CNSI are more likely to die in the immediate postinjury period than are sober victims with CNSI. Methods;

DESIGN

A retrospective cohort of 401 MVC fatalities from four Michigan counties for the time period 1985 to 1991 was studied.

MEASUREMENTS

Medical examiner records were reviewed to determine age, blood alcohol concentration (BAC), and TTD. Injury severity was calculated with the Abbreviated injury Scale (1985 version). Anatomical profile scores and G scores were also calculated and used to identify CNSI subjects.

ANALYSIS

chi 2 and Student's t test were used, and odds ratios with 0.95 confidence intervals (CIs) were calculated.

RESULTS

ALC(+) cases (BAC > or = 100 mg/dl) (n = 99) were significantly younger and more frequently had TTD < 1 hr than ALC(-) cases (n = 233): odds ratio 1.62[0.95 CI (1.02 to 2.58)]. Overall, CNSI cases (n = 297) were significantly younger and had fewer thoracic injuries, but did not have significantly shorter TTD, compared with non-CNSI cases. However, ALC(+) CNSI cases (n = 77) were over twice as likely to have TTD < 1 hr ¿odds ratio 2.04 [0.95 CI (1.13 to 3.70)]¿. For ALC(+) isolated CNSI cases, the odds ratio for TTD < 1 hr, compared with nonisolated CNSI cases was 8.25 (0.95; CI 0.66 to 102.5). Injury Severity Score, anatomical profile, and G scores were not significantly different for ALC(+) CNSI cases, compared with ALC(-) CNSI cases, whether isolated or nonisolated.

CONCLUSIONS

These data suggest that alcohol intoxication is associated with increased frequency of early death in MVC victims with CNSI, despite there being no detectable difference in anatomical injury scoring.

Use of indomethacin in brain-injured patients with cerebral perfusion pressure impairment: preliminary report

The effect of indomethacin, a cyclooxygenase inhibitor, was studied in the treatment of 10 patients with head injury and one patient with spontaneous subarachnoid hemorrhage, each of whom presented with high intracranial pressure (ICP) (34.4 +/- 13.1 mm Hg) and cerebral perfusion pressure (CPP) impairment (67.0 +/- 15.4 mm Hg), which did not improve with standard therapy using mannitol, hyperventilation, and barbiturates. The patient had Glasgow Coma Scale scores of 8 or less. Recordings were made of the patients' ICP and mean arterial blood pressure from the nurse's end-hour recording at the bedside, as well as of their CPP, rectal temperature, and standard therapy regimens. The authors assessed the effects of an indomethacin bolus (50 mg in 20 minutes) on ICP and CPP; an indomethacin infusion (21.5 +/- 11 mg/hour over 30 +/- 9 hours) on ICP, CPP, rectal temperature, and standard therapy regimens (matching the values before and during infusion in a similar time interval); and discontinuation of indomethacin treatment on ICP, CPP, and rectal temperature. The indomethacin bolus was very effective in lowering ICP (p < 0.0005) and improving CPP (p < 0.006). The indomethacin infusion decreased ICP (p < 0.02), but did not improve CPP and rectal temperature. The effects of standard therapy regimens before and during indomethacin infusion showed no significant changes, except in three patients in whom mannitol reestablished its action on ICP and CPP. Sudden discontinuation of indomethacin treatment was followed by significant ICP rebound. The authors suggest that indomethacin may be considered one of the frontline agents for raised ICP and CPP impairment.

Effects of ethanol on respiratory function in traumatic brain injury

It has been observed that traumatic brain injury (TBI) increases the susceptibility of the brain to subsequent hypoxia, and prolonged apnea occurs in ethanol (EtOH)-treated animals following brain injury. This investigation tests the hypothesis that EtOH suppresses ventilation and hypercapnic respiratory drive following TBI. Immature pigs were anesthetized with halothane and received a 2 to 3 atm fluid-percussion brain injury. Respiratory parameters, including tidal volume, frequency, ventilation (VE), and arterial blood gases were measured on 100% O2 and on 5% to 6% inspired CO2 in O2 prior to and at 10, 60, 120, and 180 minutes after TBI. Hypercapnic response sensitivity (S) was measured as the change in VE per mm Hg increase in PaCO2. Intracranial pressure, mean arterial blood pressure, heart rate, brain temperature, glucose, and EtOH levels were also monitored. Three groups were studied: the first group of six received EtOH (3.5 gm/kg, intragastrically) without brain injury; the second group of six received TBI without EtOH; the third group of eight received EtOH and TBI. Ethanol levels were 121 +/- 13 (standard error of the mean) mg/dl in the EtOH/TBI group (136 +/- 25 in the EtOH group) at the time of injury, and 175 +/- 12 mg/dl in the EtOH/TBI group (200 +/- 20 mg/dl in the EtOH group) at 120 minutes after injury. The EtOH/TBI animals had significantly lower VE and S, and higher PaCO2 following brain injury (p < 0.05, repeated-measures analysis of variance). No significant differences were identified between groups for pH, PaCO2, intracranial pressure, heart rate, brain temperature, or glucose levels. Ethanol intoxication leads to significant impairment of respiratory control following traumatic brain injury and may contribute to brain injury in intoxicated trauma victims.

Prostaglandins modulate alterations of microvascular permeability, blood flow, edema and serotonin levels following spinal cord injury: an experimental study in the rat

The possibility that prostaglandins influence edema formation, microvascular permeability increase and reduction of blood flow following spinal cord trauma was examined in a rat model. In addition, the influence of prostaglandins on serotonin metabolism of the traumatized spinal cord was evaluated. Trauma to spinal cord (2-mm-deep and 5-mm-long incision in the right dorsal horn of T10-11 segments) resulted in a profound increase of the water content 5 h after injury. At this time, the microvascular permeability to Evans Blue and [131I]sodium was increased by 457 and 394%, respectively. The blood flow was reduced by 30%. The serotonin (5-hydroxytryptamine) content of the spinal cord increased by 205%. The plasma serotonin level rose by 152% in the injured group of rats. Pretreatment with indomethacin (10 mg/kg, i.p.) 30 min before trauma significantly reduced the edema and microvascular permeability increase. The local spinal cord blood flow of traumatized animals was partially restored. The increases of serotonin levels of the spinal cord and plasma were significantly attenuated. These beneficial effects of indomethacin were not present in rats given a lower dose (5 mg/kg). Indomethacin in either dose did not influence these parameters of control rats without trauma to the cord. Since indomethacin is a potential inhibitor of prostaglandins synthesis our observations indicate: (i) that prostaglandins participate in many microvascular responses (permeability changes, edema, blood flow) occurring after a trauma to the spinal cord; (ii) that these effects of the drug seem to be dose dependent, and (iii) that the prostaglandins may influence the serotonin metabolism following trauma to the spinal cord.

The effect of indomethacin upon cerebral blood flow in healthy volunteers. The influence of moderate hypoxia and hypercapnia

In a randomized study of healthy volunteers indomethacin bolus injection followed by continuous infusion decreased CBF from normal levels ranging from 45 to 80 ml/100 g/min to levels ranging from 24 to 57 ml/100 g/min. These low levels were sustained during a six hour infusion period. Periods of hypoxia during inhalation of 17% oxygen and hypercapnia during inhalation of 2-4% CO2 normalized CBF.

Brain injury and repair mechanisms: the potential for pharmacologic therapy in closed-head trauma

Rotational acceleration from closed-head trauma produces shear-strain brain injury at the interface of gray and white matter. The initial injury is followed by progressive damage involving three key phenomena: progression of subtle focal axonal damage to axonal transection between six and 12 hours after injury, progressive development of tissue microhemorrhages between 12 and 96 hours after injury, and development of tissue and cerebral spinal fluid lactic acidosis that does not appear to be explained by trauma-induced tissue depolarization, activation of phospholipases and the release of free arachidonic acid, radical generation by metabolism of arachidonate, and lipid peroxidation with consequent membrane degradation and partial mitochondrial uncoupling. Because of terminal differentiation, neurons may have a limited membrane repair capability that might be stimulated by growth factors. Other potential therapeutic interventions include calmodulin inhibitors, iron chelators, and free radical scavengers.

Effect of neonatal capsaicin treatment on neurogenic pulmonary edema from fluid-percussion brain injury in the adult rat

The frequent occurrence of acute death from pulmonary failure in experimental head injury studies on Sprague-Dawley rats prompted an investigation into the manner in which acute neurogenic pulmonary edema develops in these animals as a result of an applied fluid pressure pulse to the cerebral hemispheres. Studies were performed in adult animals using histamine H1 and H2 blocking agents, or in adult animals treated as neonates with capsaicin to destroy unmyelinated C-fibers. Recordings were made of either the pulmonary arterial or the right ventricular pressure, and the left atrial and femoral arterial pressures before, during, and after injury to provide a record of the hemodynamic response throughout the development of neurogenic pulmonary edema. Head injury triggered the almost immediate development of pressure transients with and without neurogenic pulmonary edema. All rats, regardless of treatment, reacted with nearly identical systemic arterial pressure responses; however, the pulmonary responses followed a time course that was independent of systemic arterial pressure changes. Acute neurogenic pulmonary edema was always associated with a substantial increase in pulmonary arterial and left atrial pressures; conversely, pressure increases of similar magnitude were not always associated with edema. Histamine H1 and H2 blockers significantly reduced the pulmonary pressure surges only in rats free of neurogenic pulmonary edema. All capsaicin-treated rats showed suppressed pulmonary pressure responses, normal lung water content, elevated lung surface tension, and significantly reduced levels of immunoreactive substance P in the spinal cord and vagus nerve. While the pressures cannot clarify how edema influences the observed hemodynamics, they do not support the view that edema is the direct consequence of pulmonary hypertension. It is proposed that neurogenic pulmonary edema is a functional disturbance provoked by adverse stimuli from outside the lungs and that in the rat the primary afferent fiber is essential to the production of this entity.

Indomethacin, an inhibitor of prostaglandin synthesis attenuates alteration in spinal cord evoked potentials and edema formation after trauma to the spinal cord: an experimental study in the rat

The potential efficacy of indomethacin (a potent inhibitor of endogenous prostaglandin synthesis) on spinal cord-evoked potentials and edema formation occurring after a focal trauma to the spinal cord was examined in a rat model. The spinal cord evoked potentials were recorded in urethane-anesthetized male rats using monopolar electrodes placed epidurally over the T9 (rostral) and T12 (caudal) segments after stimulation of the ipsilateral right tibial and sural nerves. Reference electrodes were placed in the corresponding paravertebral muscles. The spinal cord evoked potential consisted of a small positive peak followed by a broad and high negative peak. Amplitudes and latencies of the maximal positive peak and the maximal negative peak were measured. The latencies and amplitudes 30 min before injury were used as references (100%). A complete loss was denoted as 0%. All the potentials were quite stable during 30 min of recording before injury. Infliction of trauma to the T10-T11 segments of the spinal cord with a sterile scalpel blade (about 5 mm longitudinal and 2 mm deep incision into the right dorsal horn extending to Rexed's laminae VII) in untreated animals resulted in an immediate depression of the rostral maximal negative peak amplitude (60-100%) which persisted during 5 h of recording. The latencies of the rostral as well as caudal maximal negative and positive peaks increased successively from 2 h post-trauma. In this group of animals, 5 h after injury the spinal cord water content in the traumatized segments was increased by more than 6% as compared with a group of uninjured animals. Pretreatment with indomethacin (10 mg/kg body weight i.p. 30 min before injury) markedly attenuated the immediate decrease in the maximal negative peak amplitude after injury, but did not influence the successive latency increase. However, the increase in the water content of the traumatized cord after 5 h was less pronounced compared with untreated injured rats. Our results show a beneficial effect of indomethacin on trauma-induced spinal cord evoked potential changes and edema formation. Prostaglandins may thus influence early bioelectrical changes occurring in traumatized spinal cord not reported earlier. The findings support the view that early recording of spinal cord evoked potential may be useful to predict the outcome in some forms of spinal cord injuries.

Early perifocal cell changes and edema in traumatic injury of the spinal cord are reduced by indomethacin, an inhibitor of prostaglandin synthesis. Experimental study in the rat

The possibility that prostaglandins participate in the formation of perifocal edema and cell changes following a localized trauma to the spinal cord was investigated in a rat model. A laminectomy was performed in urethane-anesthetized animals at the thoracic T10-11 segment. Using a scalpel blade a unilateral lesion, about 2 mm deep and 5 mm long was made 1 mm to the right of the midline. The deepest part of the injury occupied Rexed's lamina VII of the dorsal horn. Animals were pretreated with the prostaglandin synthesis inhibitor, indomethacin (10 mg/kg, i.p. 30 min prior to trauma). Five hours after the injury the water content was determined and cell changes in and around the primary lesion were examined by light and electron microscopy. Normal and injured rats without indomethacin pretreatment served as controls. Untreated injured rats showed a profound increase of water content in the traumatized T10-11, the rostral (T9) and caudal (T12) segments compared with normal rats. These segments also exhibited marked cell changes in ipsilateral and contralateral dorsal and ventral horns. The gray matter had a spongy appearance and some nerve cells were condensed and distorted. The white matter contained many distorted fibers. Immunostaining for myelin basic protein showed a marked reduction of reaction product in the injured animals compared with normal rats. Ultrastructurally widened extracellular spaces, cytoplasmic vacuolation, swollen and condensed neurons, swollen astrocytes and vesiculation of myelin were frequent findings. Pretreatment of rats with indomethacin significantly reduced the accumulation of water in the traumatized and in the rostral and caudal segments. The structural changes were less pronounced particularly in the cranial and caudal segments.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of indomethacin on intracranial pressure, cerebral blood flow and cerebral metabolism in patients with severe head injury and intracranial hypertension

In five head-injured patients with cerebral contusion and oedema in whom it was not possible to control intracranial pressure (ICP) (ICP greater than 20 mmHg) by artificial hyperventilation (PaCO2 level 3.5-4.0 kPa) and barbiturate sedation, indomethacin was used as a vasoconstrictor drug. In all patients, indomethacin (a bolus injection of 30 mg, followed by 30 mg/h for seven hours) reduced ICP below 20 mmHg for several hours. Studies of cerebral circulation and metabolism during indomethacin treatment showed a decrease in CBF at 2 h. After 7 h, ICP remained below 20 mmHg in three patients, and these still had reduced CBF. In the other patients a return of ICP and CBF to pretreatment levels was observed. In all patients indomethacin treatment was followed by a fall in rectal temperature. These results suggest that indomethacin due to its cerebral vasoconstrictor and antipyretic effect should be considered as an alternative for treatment of ICP-hypertension in head-injured patients.

Combined effect of respirator-induced ventilation and superoxide dismutase in experimental brain injury

The function-specific enzyme superoxide dismutase (SOD) was tested for its protective effect in severe experimental fluid-percussion brain injury (4.45 +/- 0.10 atm) in 30 of 60 randomly selected male Sprague-Dawley rats. A respirator was used only in the event of need. The number of animals with permanent resumption of spontaneous breathing (Type I respiratory response) remained essentially the same in each group. However, when Type II apnea (cannot maintain recovery) and Type III apnea (never recovers from the initial apnea) were terminated with a respirator, all rats with Type II responses from each group were successfully converted to a state of sustained spontaneous breathing. In contrast, only five (41.7%) of the 12 rats with Type III response were salvaged in the control group while five (83.3%) of six Type III rats in the SOD-treated group were saved. The results reveal the nature of the therapeutic effectiveness of superoxide radical scavengers in the overall outcome of head injury in this animal model. While SOD alone did not increase the number of spontaneous survivors, the drug shifted a number of animals from the critically injured rats with Type III respiratory response to the less critical Type II condition. Whereas induced respiration as the sole therapy in the control group lowered the mortality rate to 23.3%, respiratory assistance together with SOD treatment reduced the "mortality" to a single animal with Type III apnea (3.3%) which was alive but still required the respirator after 2 hours (p less than 0.001). The results show that respiratory assistance alone accounted for a 33% decrease in mortality rate and that SOD, given in addition to induced ventilation, further decreased mortality by 20%. Since SOD enzymes are reactively specific for superoxide, the increased survival rate of the brain-injured rat must have been due either to preventing or to minimizing pathophysiological changes, probably in the brain stem, caused by oxygen free radicals.