Documented reversal of global ischemia immediately after removal of an acute subdural hematoma. Report of two cases

Minimally invasive fibrinolytic treatment and drainage in patients with acute subdural hemorrhage and underlying comorbidities

The incidence of acute subdural hemorrhage (ASDH), which is often caused by head trauma, is steadily increasing due to an increase in the elderly population and the use of anticoagulants. Urgent surgical treatment is recommended if the patient has impaired consciousness, worsening neurological symptoms, or brain midline shift (MLS) due to large hematomas on brain computed tomography (CT). Although large craniotomy is traditionally recommended for ASDH removal, old age, comorbidities, and antiplatelet drugs are considered risk factors for surgical complications, many neurosurgeons hesitate to perform aggressive surgical procedures in these patients. In this study, we introduced a method that can quickly and effectively remove ASDH without general anesthesia. We retrospectively reviewed 11 cases of patients with ASDH who underwent hematoma drainage between June 2019 and December 2020. We measured the maximum subdural hematoma thickness and MLS on brain CT of patients and recorded the Glasgow Coma Scale scores before and after the surgical procedure. All patients had multiple comorbidities, and seven patients received anticoagulant or antiplatelet therapy. On initial brain CT, the median subdural hemorrhage thickness was 21.36 mm, median MLS was 10.09 mm, and mean volume of the subdural hematoma was 163.64 mL. The mean evacuation rate of the subdural hematoma after drainage was 83.57%. There was no rebleeding or operation-related infection during the aspiration procedure, and the median MLS correction after the procedure was 7.0 mm. Our treatment strategies can be a reliable, less invasive, and alternative treatment option for patients at high risk of complications due to general anesthesia or patients who are reluctant to undergo a large craniotomy due to a high bleeding tendency.

Bilateral Cerebral Ptosis in a Patient with Subdural Hemorrhage: a Case Report

Although cerebral ptosis is rare, it is commonly associated with unilateral right cerebral hemisphere lesions. We report a case of a 79-year-old woman who presented with bilateral complete ptosis after a traumatic right fronto-temporo-parietal subdural hemorrhage (SDH). Bilateral ptosis was the primary manifestation of the acute right SDH, and the patient had no parenchymal lesion. Her prognosis was good, and she made a complete recovery. Right hemispheric hypoperfusion, as demonstrated on brain perfusion single-photon emission computed tomography, implied that the lateralization of eyelid control was in the right hemisphere, in line with previous reports.

Overview of Monitoring of Cerebral Blood Flow and Metabolism after Severe Head Injury

The relationships between cerebral blood flow (CBF), cerebral metabolism (cerebral metabolic rate of oxygen, CMRO2) and cerebral oxygen extraction (arteriovenous difference of oxygen, AVDO2) are discussed, using the formula CMRO2 = CBF × AVDO2. Metabolic autoregulation, pressure autoregulation and viscosity autoregulation can all be explained by the strong tendency of the brain to keep AVDO2 constant. Monitoring of CBF, CMRO2 or AVDO2 very early after injury is impractical, but the available data indicate that cerebral ischemia plays a considerable role at this stage. It can best be avoided by not "treating" arterial hypertension and not using too much hyperventilation, while generous use of mannitol is probably beneficial. Once in the ICU, treatment can most practically be guided by monitoring of jugular bulb venous oxygen saturation. If saturation drops below 50%, the reason for this must be found (high intracranial pressure, blood pressure not high enough, too vigorous hyperventilation, arterial hypoxia, anemia) and must be treated accordingly.

Direct visualization of microcirculation impairment after acute subdural hemorrhage in a novel animal model

OBJECTIVE

Direct brain compression and secondary injury due to increased intracranial pressure are believed to be the pathognomic causes of a grave outcome in acute subdural hemorrhage (aSDH). However, ischemic damage from aSDH has received limited attention. The authors hypothesized that cerebral microcirculation is altered after aSDH. Direct visualization of microcirculation was conducted in a novel rat model.

METHODS

A craniectomy was performed on each of the 18 experimental adult Wistar rats, followed by superfusion of autologous arterial blood onto the cortical surface. Changes in microcirculation were recorded by capillary videoscopy. Blood flow and the partial pressure of oxygen in the brain tissue (P_btO₂) were measured at various depths from the cortex. The brain was then sectioned for pathological examination. The effects of aspirin pretreatment were also examined.

RESULTS

Instantaneous vasospasm of small cortical arteries after aSDH was observed; thrombosis also developed 120 minutes after aSDH. Reductions in blood flow and P_btO₂ were found at depths of 2-4 mm. Blood-brain barrier disruption and thrombi formation were confirmed using immunohistochemical staining, while aspirin pretreatment reduced thrombosis and the impairment of microcirculation.

CONCLUSIONS

Microcirculation impairment was demonstrated in this aSDH model. Aspirin pretreatment prevented the diffuse thrombosis of cortical and subcortical vessels after aSDH.

Rethinking Neuroprotection in Severe Traumatic Brain Injury: Toward Bedside Neuroprotection

Neuroprotection after traumatic brain injury (TBI) is an important goal pursued strenuously in the last 30 years. The acute cerebral injury triggers a cascade of biochemical events that may worsen the integrity, function, and connectivity of the brain cells and decrease the chance of functional recovery. A number of molecules acting against this deleterious cascade have been tested in the experimental setting, often with preliminary encouraging results. Unfortunately, clinical trials using those candidate neuroprotectants molecules have consistently produced disappointing results, highlighting the necessity of improving the research standards. Despite repeated failures in pharmacological neuroprotection, TBI treatment in neurointensive care units has achieved outcome improvement. It is likely that intensive treatment has contributed to this progress offering a different kind of neuroprotection, based on a careful prevention and limitations of intracranial and systemic threats. The natural course of acute brain damage, in fact, is often complicated by additional adverse events, like the development of intracranial hypertension, brain hypoxia, or hypoperfusion. All these events may lead to additional brain damage and worsen outcome. An approach designed for early identification and prompt correction of insults may, therefore, limit brain damage and improve results.

Hypocalcaemia as a prognostic factor of early mortality in moderate and severe traumatic brain injury

OBJECTIVES

Our main objective was to evaluate whether serum hypocalcaemia on the third day [defined as < 2.1 mmol/l (8.5 mg/dl)] is a prognostic factor for early mortality after moderate and severe traumatic brain injury (TBI).

METHODS

We developed an ambispective comparative case control study. We evaluated clinical profiles from included patients from January 2005 to July 2009 and we prospectively recruited additional patients from August 2009 to July 2011. Patients were between 1 and 89 years old and had a Glasgow Coma Scale of 3-12 points following TBI.

RESULTS

We calculated an Odds Ratio of 5.2 (Confidence Intervals 95%: 4.48 to 6.032) for hypocalcaemia on day three, which was associated with death. Retrospectively (January 2005 to July 2009) we compiled data from 81 patients. Prospectively (August 2009 to July 2011) we recruited 41 patients. The adjusted variables in the logistic regression final model were: serum calcium on day three (Odds Ratio 3.5, Confidence Intervals 95%: 1·12 to 13·61, P < 0·028) and anisocoria (Odds Ratio 8·24, Confidence Intervals 95%: 1·3 to 67·35, P < 0·019) obtaining an adjusted R2 of 0·22 (P < 0·005).

DISCUSSION

The serum levels of calcium on day three could be useful for the prediction of mortality in patients with moderate and severe TBI.

Decompressive craniectomy with multi-dural stabs - A combined (SKIMS) technique to evacuate acute subdural hematoma with underlying severe traumatic brain edema

Context:

The decompressive craniotomy alone or with dural flap opening to evacuate acute subdural hematoma with underlying brain edema in severe traumatic brain injury has proved either insufficient in the first place or has fatal complications secondly.

Aims:

To reduce the fatality of conventional procedures and to evacuate acute subdural hematoma with severe brain edema by a combination of decompressive craniotomy and multi-dural stabs (SKIMS-Technique) without brain pouting and lacerations in low Glasgow coma scale (GCS) score patients.

Settings and Design:

The prospective study was conducted in the Department of Neurosurgery, from June, 2006 to June 2011, under a uniform protocol.

Materials and Methods:

A total of 225 patients of severe brain trauma were admitted to the accident and emergency unit of Neurosurgery and after initial resuscitation a CT brain was performed. All patients had a GCS score of 8 and below. All patients were ventilated postoperatively and ICP was monitored.

Statistical Analysis Used:

The data was analyzed and evaluated by the statistical methods like student's T-test. The analysis of Variance was used where-ever applicable.

Results:

The survival of multi-dural stab group was 77.31% (92/119) with good recovery in 42.02% (50/119) and a mortality of 22.69% (27/119) as compared with 46.23% (49/106) survival in open dural flap (control) group with 15.09% (16/106) good recovery and mortality of 53.77% (57/106).

Conclusions:

This new approach, known as SKIMS-Technique or Combined Technique i.e., “decompressive craniectomy with multi-dural stabs”, proved much effective in increasing survival of low GCS and severe traumatic brain edema patients with acute subdural hematoma.

Hyperemia beneath evacuated acute subdural hematoma is frequent and prolonged in patients with an unfavorable outcome: a xe-computed tomographic study

OBJECTIVE

To verify the values and the time course of regional cerebral blood flow (rCBF) in the cortex located beneath an evacuated acute subdural hematoma (SDH) and their relationship with neurological outcome.

METHODS

rCBF levels were measured in multiple regions of interest, by means of a Xe-computed tomographic technique, in the cortex underlying an evacuated SDH and contralaterally in 20 patients with moderate or severe traumatic brain injury and an evacuated acute SDH. Twenty-three patients with moderate or severe traumatic brain injury and an evacuated extradural hematoma or diffuse injury served as the control group. Outcome was evaluated by means of the Glasgow Outcome Scale at 12 months.

RESULTS

Values for the maximum (rCBFmax) and the mean of all rCBF levels in the cortex beneath the evacuated SDH were more frequently consistent with hyperemia. The side-to-side differences in the mean of all rCBF and rCBFmax levels between lesioned and nonlesioned hemispheres were greater in patients with evacuated SDH than in controls (P = 0.0013 and P = 0.0018, respectively). The side-to-side difference in the maximum rCBF value was higher in SDH patients with unfavorable outcomes than in controls at 24 to 96 hours and at 4 to 7 days and higher than in patients with favorable outcomes at 4 to 7 days. The widest side-to-side difference in rCBFmax value was more elevated in patients with an evacuated SDH with unfavorable outcome than in patients with a favorable outcome (P = 0.047), whereas no differences were found in controls. The SDH thickness and the associated midline shift were greater in patients with unfavorable outcomes than in those with favorable outcomes.

CONCLUSION

On average, hyperemic long-lasting rCBF values frequently occur in the cortex located beneath an evacuated SDH and seem to be associated with unfavorable outcome.

Hypertonic saline: a clinical review

Literature suggest that hypertonic saline (HTS) solution with sodium chloride concentration greater than the physiologic 0.9% can be useful in controlling elevated intracranial pressure (ICP) and as a resuscitative agent in multiple settings including traumatic brain injury (TBI). In this review, we discuss HTS mechanisms of action, adverse effects, and current clinical studies. Studies show that HTS administered during the resuscitation of patients with a TBI improves neurological outcome. HTS also has positive effects on elevated ICP from multiple etiologies, and for shock resuscitation. However, a prospective randomized Australian study using an aggressive resuscitation protocol in trauma patients showed no difference in amount of fluids administered during prehospital resuscitation, and no differences in ICP control or neurological outcome. The role of HTS in prehospital resuscitation is yet to be determined. The most important factor in improving outcomes may be prevention of hypotension and preservation of cerebral blood flow. In regards to control of elevated ICP during the inpatient course, HTS appears safe and effective. Although clinicians currently use HTS with some success, significant questions remain as to the dose and manner of HTS infusion. Direct protocol comparisons should be performed to improve and standardize patient care.

Multimodal monitoring during emergency hemicraniectomy for vein of Labbe thrombosis

INTRODUCTION

Cortical venous thrombosis is a rarely encountered mechanism for intracerebral hemorrhage. Multimodal monitoring may guide neurosurgical and critical care treatment in the setting of cerebral venous thrombosis.

METHODS

We report a 37-year-old service member who was admitted to a local field hospital for complaints of severe headache and left ear pain during Operation Iraqi Freedom. CT scan revealed a left temporal intracranial hematoma and subarachnoid hemorrhage. Angiogram revealed thrombosis of the vein of Labbe. Intracranial pressure (ICP), brain tissue oxygenation (PbO2), and cerebral blood flow (CBF) were monitored. There was a progressive increase in ICP despite ventricular drainage, sedation, and intubation. There was an ominous decrease in brain tissue oxygen and CBF became undetectable concomitantly with the increase in ICP. There was a dramatic decrease in ICP and improvement in brain tissue oxygenation and CBF after decompression and evacuation of the hematoma. Six weeks after the hemorrhage, the patient was able to follow simple commands and complete short sentences.

DISCUSSION

To our knowledge, this is the first description of the use of ICP, PbO2, and laser Doppler method for obtaining CBF in the same setting. Information obtained from monitoring may lead to timely decompression and avoidance of poor outcome.

Inner calvarial erosion from traumatic subdural haematoma in infancy

CASE REPORT

This is a report of a case of a subdural haematoma in infancy of possible non-accidental aetiology with raised pericerebral pressure, which we postulate has eroded the inner table of the cranial bones and resulted in leakage of marrow precursor cells into the extradural space.

RESULT

Subdural tapping via the fontanelle has created a channel allowing subsequent ingress of nucleated red cell precursors into the subdural space. This addition to the subdural collection has prolonged its course necessitating subduro-peritoneal shunting.

Evolution of Brain Tissue Injury after Evacuation of Acute Traumatic Subdural Hematomas

OBJECTIVE:

Acute traumatic subdural hematoma complicated by brain parenchymal injury is associated with a 60 to 90% mortality rate. Early surgical evacuation of the mass lesion is essential for a favorable outcome, but the severity of the underlying brain injury determines the outcome, even when surgery has been prompt. The purpose of this study was to analyze tissue biochemical patterns in the brain underlying an evacuated acute subdural hematoma to identify a characteristic pattern of changes that might indicate evolving brain injury.

METHODS:

Prospectively collected data from 33 patients after surgical evacuation of acute subdural hematoma were analyzed. Both a brain tissue oxygen tension probe and an intracerebral microdialysis probe were placed in brain tissue exposed at surgery. On the basis of the postoperative clinical course, the patients were divided into three groups: patients with early intractable intracranial hypertension, patients with evolution of delayed traumatic injury (DTI), and patients with an uncomplicated course (the no-DTI group).

RESULTS:

The overall mortality rate was 46%, with 100% mortality in the intracranial hypertension group (five patients). Mortality in the DTI group was 53% compared with only 9% in the no-DTI group (P = 0.002). There were no significant differences in the initial computed tomographic scan characteristics, such as thickness of the subdural hematoma or amount of midline shift, among the three groups. Physiological variables, as well as the microdialysate measures of brain biochemistry, were markedly different in the intracranial hypertension group compared with the other groups. Differences between the other two groups were more subtle but were significant. Significantly lower values of brain tissue oxygen tension (14 ± 8 mm Hg versus 27 ± 14 mm Hg) and higher dialysate values of lactate and pyruvate were documented in patients who developed a delayed injury compared with patients with uncomplicated courses (4.1 ± 2.3 mmol/L versus 1.7 ± 0.7 mmol/L for lactate, and 104 ± 47 μmol/L versus 73 ± 54 μmol/L for pyruvate at 24 h after injury).

CONCLUSION:

Evolution of DTI in the area of brain underlying an evacuated subdural hematoma is associated with a significant increase in mortality. Postoperatively decreasing brain tissue oxygen tension and increasing dialysate concentrations of lactate and pyruvate in this area may warn of evolving brain injury and evoke further diagnostic and therapeutic activity.

Laser Doppler Flow and Brain Tissue PO2 after Cortical Impact Injury Complicated by Secondary Ischemia in Rats Treated with Arginine

BACKGROUND

Traumatic brain injury (TBI) makes the brain susceptible to secondary insults such as ischemia. This study tested the hypothesis that L-arginine would increase regional CBF (rCBF) and brain tissue PO2 (PbtO2) at the injury site.

METHODS

A secondary insult model was employed in rodents. rCBF was measured with laser doppler flowmetry (LDF) and PbtO2 with a PO2 catheter at the impact site. Animals were randomized to receive L-arginine, D-arginine or saline intravenously, 5 minutes after impact.

RESULTS

In animals who received L-arginine, the percentage rCBF from baseline (%CBF) was higher at the impact site after impact (p < 0.001), during bilateral carotid occulation (BCO) (p = 0.001) and during reperfusion (p = 0.032). In contrast, PbtO2 was not significantly increased throughout the experiment for the L-arginine group.

CONCLUSIONS

Administration of L-arginine increased rCBF in the injured brain tissue, and resulted in better preservation of CBF during BCO than D-arginine and saline.

Admission Perfusion CT: Prognostic Value in Patients with Severe Head Trauma

PURPOSE

To assess the prognostic value of admission perfusion computed tomography (CT) in patients with severe head trauma.

MATERIALS AND METHODS

This prospective study included 130 patients with severe trauma, aged 19-86 years, admitted with a Glasgow Coma Scale score of 8 or less. They underwent perfusion CT as part of their admission CT survey. Clinical data, unenhanced cerebral CT findings, and perfusion CT scans were evaluated with respect to the Glasgow Outcome Scale (GOS) score at 3 months. Perfusion CT features were evaluated in patients with intracranial hypertension, cerebral contusions, and juxtadural hematomas. Ordered logistic regression was used to determine risk factors for an unfavorable GOS score at 3 months.

RESULTS

Perfusion CT was more sensitive than conventional unenhanced CT in the detection of cerebral contusions. Perfusion CT featured specific patterns with respect to patient outcome, with normal brain perfusion or hyperemia in patients with favorable outcome, and oligemia in patients with unfavorable outcome. The number of arterial territories with low regional cerebral blood volume at perfusion CT was an independent prognostic factor (P =.008), as were mean arterial pressure at the scene of accident (P =.083), base excess at admission (P =.002), presence of skull fractures (P =.041), and signs of herniation (P =.013) at admission unenhanced cerebral CT. Perfusion CT also showed a range of brain perfusion alterations in patients with juxtadural collections, cerebral edema, or intracranial hypertension.

CONCLUSION

Perfusion CT in patients with severe head trauma provides independent prognostic information regarding functional outcome.

Successful use of the new high-dose mannitol treatment in patients with Glasgow Coma Scale scores of 3 and bilateral abnormal pupillary widening: a randomized trial

OBJECT

The authors evaluated long-term clinical outcomes in selected acutely comatose patients with severe diffuse brain swelling and recent clinical signs of impending brain death who received a novel high-dose mannitol treatment compared with those who received conventional-dose mannitol in the emergency room.

METHODS

Forty-four adult patients with traumatic, nonmissile-inflicted, acute, severe diffuse brain swelling were prospectively and randomly evaluated. All patients were selected based on the presence of recent clinical signs of impending brain death on the first emergency room evaluation. These signs included bilateral abnormal pupillary widening and lack of motor responses to painful stimulation (Glasgow Coma Scale score of 3). The study group (23 patients) received ultra-early and fast intravenous high-dose mannitol treatment (approximately 1.4 g/kg), whereas the control group (21 patients) received half that dose (approximately 0.7 g/kg). Ultra-early improvement of bilateral abnormal pupillary widening was significantly more frequent in the high-dose mannitol group than in the conventional-dose group (p < 0.02). High-dose mannitol treatment in the emergency room was also associated with significantly better 6-month clinical outcomes (p < 0.02); the best rate of favorable outcomes was 43.5%, compared with only 9.5% in the conventional-dose mannitol group. The two groups of patients were well matched with respect to all emergency room and head computerized tomography findings, as well as the timing of initial mannitol treatment (approximately 80-90 minutes after the first evaluation at the scene of the injury). Comparative evaluation of bilateral pupillary widening between the scene of the injury and the emergency room showed no significant differences between groups, whereas mannitol dose dependence was statistically significant (p < 0.05), insofar as early pupillary improvement in the emergency room was concerned.

CONCLUSIONS

Ultra-early high-dose mannitol administration in the emergency room is the first known treatment strategy significantly to reverse recent clinical signs of impending brain death, and also to contribute directly to improved long-term clinical outcomes for these patients who have previously been considered unsalvageable.

Relationships between cerebrospinal fluid markers of excitotoxicity, ischemia, and oxidative damage after severe TBI: the impact of gender, age, and hypothermia

Excitotoxicity and ischemia can result in oxidative stress after TBI. Female sex hormones are hypothesized to be neuroprotective after TBI by affecting multiple mechanisms of secondary injury, including oxidative damage, excitotoxicity and ischemia. Ca2+ mediated oxidative stress increases with age, and hypothermia is known to attenuate secondary injury. The purpose of this study was to determine if the relationship between cerebral spinal fluid (CSF) markers of excitotoxicity, ischemia, and oxidative damage are gender and age specific and the role of hypothermia in affecting these relationships. F2-isoprostane, glutamate, and lactate/pyruvate, were assessed in CSF from adults (n = 68) with severe TBI (Glasgow coma scale [GCS] score </= 8) using ventricular CSF samples (n = 207) collected on days 1, 2, and 3 post-injury. F2-isoprostane/glutamate and F2-isoprostane/lactate/pyruvate ratios were determined for patients at each time point. Six-month Glasgow Outcome Scores (GOS) were also obtained. Repeated measures multivariate analysis showed a significant gender effect (p < 0.002) and gender*time interaction (p = 0.012) on F2-isoprostane/glutamate ratios. A significant gender effect (p = 0.050) and gender*time interaction (p = 0.049) was also seen with F2-isoprostane/lactate/pyruvate. Hypothermia (p = 0.001) and age (p = 0.026) significantly increased F2-isoprostane/glutamate ratios. Females had a significant inverse relationship between day 1 F2-isoprostane/glutamate ratios and GOS scores (r =- 0.43; p = 0.05) as well as day 1 F2-isoprostane/lactate/pyruvate ratio (r =- 0.46; p = 0.04) and GOS scores. These results indicate that females have smaller oxidative damage loads than males for a given excitotoxic or ischemic insult and female gonadal hormones may play a role in mediating this neuroprotective effect. These results also suggest that susceptibility to glutamate mediated oxidative damage increases with age and that hypothermia differentially attenuates CSF glutamate versus F2-isoprostane production. Gender and age differences in TBI pathophysiology should be considered when conducting clinical trials in TBI.

Clinical Trials in Traumatic Brain Injury: Lessons for the Future

Thus far, none of the neuroprotective drugs that have been tested to reduce or prevent secondary ischemic brain damage have been shown clear benefit. We will attempt to identify factors that may be responsible for some of these failures. We also will give our thoughts on how to prevent these pitfalls in the usefulness and criteria for use of animal models for traumatic brain injury to depict human head injury are discussed. Clearly, mechanism-driven trials, in which individual pathophysiological mechanisms are targeted, are more likely to show benefit in this heterogeneous patient population. Other factors, such as the effect of brain penetration, safety and tolerability of the compound, and the interface between the pharmaceutical industry and academics are a major influence in the success of these trials. Furthermore, the way trials have been analyzes in the past may not always have been be the most appropriate to show benefits. It is clear that a multi-targeted approach is necessary to address the complicated and closely related mechanisms seen after traumatic and or ischemic brain damage.

Analysis of ischemic brain damage in cases of acute subdural hematomas

BACKGROUND

Ischemic damage of the brain is one of the most important factors for the sequelae of acute subdural hematomas (ASDHs). However, ischemic damage is infrequently addressed in a systematic manner in the clinical setting.

METHODS

The analysis of ischemic brain damage was performed based on serial computed tomography (CT) scans in 80 patients with traumatic ASDHs. Single photon emission computed tomography (SPECT) for regional blood flow and/or magnetic resonance imaging (MRI) were also performed.

RESULTS

Follow-up CT scans showed ischemic brain damage in 19 patients and no significant damage in 35 patients. The remaining 26 patients progressively deteriorated to the point of brain death. The ischemic brain damage was seen most frequently in the territory of the anterior cerebral artery (13 cases), followed by the territory of the posterior cerebral artery (12 cases). The ischemic damages in the pallidum, the hypothalamus and the thalamus were demonstrated in 4, 8, and 4 cases, respectively. The ischemic damage in the underlying brain that was probably because of the direct compression of the hematoma was seen in only two cases.

CONCLUSIONS

Most of the ischemic brain damage noted in this study was because of arterial compression secondary to the brain shift and brain herniation, rather than the direct effect of the hematoma upon the underlying brain. Ischemic brain damage adversely affects outcome morbidity, and the difficulty in preventing ischemic damage in cases with marked brain shift leads to poor outcome in patients with ASDHs.

Expensive cerebral blood flow measurements alone are useless and misinformative in comatose patients: a comprehensive alternative

Since the first report addressing quantification of cerebral blood flow (CBF), concomitant assessment of cerebral oxygen consumption was also carried out. Over the years, however, some investigators have emphatically and mistakenly addressed cerebral ischemia in comatose patients, on the basis of CBF measurements alone. In contrast, we have repeatedly reported that ischemia in these patients must be precisely evaluated based on CBF-metabolism coupling or uncoupling, rather than CBF alone. Based on these previous findings, we therefore propose a comprehensive alternative approach, namely the evaluation of brain ischemia in comatose patients based on cerebral metabolic parameters, such as cerebral extraction of oxygen or cerebral lactate release, without expensive CBF measurements.

Hyperacute measurement of intracranial pressure, cerebral perfusion pressure, jugular venous oxygen saturation, and laser Doppler flowmetry, before and during removal of traumatic acute subdural hematoma

OBJECT

The poor prognosis for traumatic acute subdural hematoma (ASDH) might be due to underlying primary brain damage, ischemia, or both. Ischemia in ASDH is likely caused by increased intracranial pressure (ICP) leading to decreased cerebral perfusion pressure (CPP), but the degree to which these phenomena occur is unknown. The authors report data obtained before and during removal of ASDH in five cases.

METHODS

Five patients who underwent emergency evacuation of ASDH were monitored. In all patients, without delaying treatment, a separate surgical team (including the senior author) placed an ICP monitor and a jugular bulb catheter, and in two patients a laser Doppler probe was placed. The ICP prior to removing the bone flap in the five patients was 85, 85, 50, 59, and greater than 40 mm Hg, resulting in CPPs of 25, 3, 25, 56, and less than 50 mm Hg, respectively. Removing the bone flap as well as opening the dura and removing the blood clot produced a significant decrease in ICP and an increase in CPP. Jugular venous oxygen saturation (SjvO2) increased in four patients and decreased in the other during removal of the hematoma. Laser Doppler flow also increased, to 217% and 211% compared with preevacuation flow.

CONCLUSIONS

Intracranial pressure is higher than previously suspected and CPP is very low in patients with ASDH. Removal of the bone flap yielded a significant reduction in ICP, which was further decreased by opening the dura and evacuating the hematoma. The SjvO2 as well as laser Doppler flow increased in all patients but one immediately after removal of the hematoma.

Improving clinical outcomes from acute subdural hematomas with the emergency preoperative administration of high doses of mannitol: a randomized trial

OBJECTIVE

To evaluate clinical outcomes and postoperative physiological findings for comatose patients with acute subdural hematomas who received preoperative high-dose mannitol (HDM) versus conventional-dose mannitol treatment.

METHODS

One hundred seventy-eight adult patients with non-missile, traumatic, acute, subdural hematomas were prospectively and randomly assigned to receive emergency, preoperative, intravenous HDM treatment (91 patients), compared with a control group treated with a lower preoperative mannitol dose (87 patients).

RESULTS

Preoperative improvement of abnormal pupillary widening was significantly more frequent in the study group than in the control group of patients (P < 0.0001). Preoperative HDM treatment was also associated with significantly better clinical outcomes at 6-month follow-up evaluations (P < 0.01). Postoperative physiological findings revealed statistically significant between-group differences, with higher intracranial pressure and lower cerebral extraction of oxygen (relative cerebral hyperperfusion) in the control group, compared with the HDM group. Postoperative global brain ischemia (abnormally low arteriojugular lactate difference values) was rare and was detected in 2.2 and 3.4% of the patients in the study and control groups, respectively.

CONCLUSION

Emergency preoperative HDM administration was associated with improved clinical outcomes for patients with acute subdural hematomas. Preoperative improvement of abnormal pupillary widening and better postoperative control of intracranial hypertension and associated relative cerebral hyperperfusion seemed to be relevant factors associated with improved outcomes.

Traumatic brain ischemia during neuro intensive care: myth rather than fact

In non-missile severe acute brain trauma, brain ischemia was a frequent finding in cadavers. Studies during neuro intensive care, however, have failed to disclose brain ischemia under most circumstances, except when cerebral hemodynamic and metabolic parameters have been misinterpreted, or when cerebral blood flow (CBF) alone has been addressed in a biased fashion, without mandatory metabolic data. Indeed, comprehensive and unbiased studies focusing on global cerebral metabolic activity have invariably revealed a condition of normal coupling between reduced CBF and oxygen consumption in the early postinjury hours, which is then followed by a prolonged, sustained pattern of relative cerebral hyperperfusion (the opposite of ischemia). Accordingly, traumatic brain ischemia during intensive care represents myth rather than fact.

Intracerebral microdialysis and its clinical application: a review

In vivo intracerebral microdialysis is an important neurochemical technique that has been used extensively in the experimental setting. Relatively recently, techniques have been developed to utilize this method in human subjects. The past decade has seen the advent of clinical investigations utilizing in vivo microdialysis in a number of neuropathological states. This review summarizes the principles of in vivo microdialysis techniques, as applied to humans, while discussing the significance of recent investigations for future clinical development.

[Uses and abuses of hyperventilation in severe traumatic brain injury]

A critical evaluation was done about the guidelines and effects of the hyperventilation maneuver on prevention and treatment of increased intracranial pressure (ICP) that follows severe traumatic brain injury (TBI). The prophylactic use of hyperventilation should be avoided after severe TBI acute phase, unless high venous O2 values are recorded at jugular bulb blood (SjO2), or to allow time when there are evidences of neurologic deterioration with posturing. The lack of cerebrovascular response to hyperventilation to low the ICP means that the blood brain barrier (BBB) function is extensively impaired. Then, hyperventilation may be used as a screening therapeutic test in acute severe TBI, since BBB impairment is the pointer that other available clinical procedures for high ICP control (sedation, paralysis and osmotic diuretics) are not workable. A new pathogenetic hypothesis about traumatic brain edema and its therapeutic approach is presented.

Current international trends in severe acute brain trauma

A comprehensive review is presented on current international trends regarding research and management of severe acute brain trauma. Controversial issues are thoroughly discussed and an attempt is made to clarify questionable aspects from pertinent publications in the international literature. A proposition is made to manage not only intracranial pressure and perfusion pressure, but also cerebral hemometabolic parameters in these critically ill patients. Currently available management guidelines are not evidence-based.

The Brain Trauma Foundation. The American Association of Neurological Surgeons. The Joint Section on Neurotrauma and Critical Care. Hyperventilation

Chronic prophylactic hyperventilation therapy should be avoided during the first 5 days after severe TBI and particularly during the first 24 h. CBF measurements in patients with severe TBI demonstrate that blood flow early after injury is low and strongly suggest that in the first few hours after injury the absolute values approach those consistent with ischemia. These findings are corroborated by AVdO2 and SjO2 and brain tissue O2 measurements. Hyperventilation will reduce CBF values even further, but will not consistently cause a reduction of ICP and may cause loss of autoregulation. The cerebral vascular response to hypocapnia is reduced in those with the most severe injuries (subdural hematomas and diffuse contusions), and there is substantial local variability in perfusion. While the CBF level at which irreversible ischemia occurs has not been clearly established, ischemic cell change has been demonstrated in 90% of those who die following TBI, and there is PET evidence that such damage is likely to occur when CBF drops below 15-20 cc/100 g/min. A prospective randomized clinical trial has determined that outcomes are worse when TBI patients are treated with chronic prophylactic hyperventilation therapy. Within the standard, guideline, and options, specific paCO2 thresholds have been described that are different for each of the three parameters. These individual thresholds were selected based on the preponderance of literature supporting those thresholds in the contexts of the statements which included them. With the exception of the threshold included for the standard in this guideline, it is emphasized that the paCO2 threshold is not as important as the general concept of hyperventilation. The preponderance of the physiologic literature concludes that hyperventilation during the first few days following severe traumatic brain injury, whatever the threshold, is potentially deleterious in that it can promote cerebral ischemia.

Effect of hypocapnea on CBF and extracellular intermediates of secondary brain injury

We examined the metabolic response of the brain underlying subdural hematomas or surrounding contusions to hyperventilation and looked for evidence of ischemia. Twelve consecutive patients with severe traumatic brain injury (TBI) (GCS < 8) who required surgery for evacuation of subdural hematoma or hemorrhagic contusion were studied. At surgery, a microdialysis catheter was placed into the cortex in a gyrus adjacent to the contusion or underlying the subdural hematoma. A thermal diffusion flow probe was placed on the cortex directly above the dialysis catheter. On days 1 and 3 post injury, two trials of hyperventilation were performed which dropped the patients' pCO2 10 mm Hg for 30 minutes. Monitoring of CBF and collection of dialysis fluid continued throughout each hyperventilation trial. Data was analyzed for a three hour window surrounding each hyperventilation. Brief periods of hyperventilation did not cause a significant elevation of the extracellular lactate/pyruvate ratio or glutamate level in areas of the brain likely to be the most vulnerable to secondary injury. In spite of hyperventilation leading to a significant decline in local CBF in 20% of the trials, there was no evidence of ischemia or excitatory amino acid release associated with hyperventilation.

Comparison of jugular venous oxygen saturation and brain tissue Po2 as monitors of cerebral ischemia after head injury

OBJECTIVE

To compare the characteristics of jugular venous oxygen saturation (Sjvo2) and brain tissue Po2 (Pbto2) as monitors for cerebral ischemia after severe head injury. Sjvo2 has been useful as a monitor for cerebral ischemia, but it is limited by its inability to identify regional cerebral ischemia. Pbto2 may be superior to Sjvo2 for this purpose, because oxygenation in localized areas of the brain can be monitored.

DESIGN

Sjvo2 and Pbto2 were successfully monitored in 58 patients with severe head injury. The changes in Sjvo2 and Pbto2 were compared during ischemic episodes.

SETTING

Neurosurgical intensive care unit of a level I trauma center.

MEASUREMENTS AND MAIN RESULTS

During the monitoring period, which averaged 90 hrs/patient, there were 54 episodes during which Sjvo2 decreased to <50% and/or Pbto2 decreased to <8 torr. Two of these episodes were caused by an infarction in the area of the Po2 probe, leaving 52 episodes of global hypoxia/ischemia that were identified by one of the two monitors. The sensitivities of the two monitors for detecting ischemia, using the thresholds of 50% and 8 torr for Sjvo2 and Pbto2, respectively, were similar. The Sjvo2 catheter detected 69.7% of the episodes and the Pbto2 catheter detected 63.5% of the episodes. In most of the remaining episodes, both probes reflected a decrease in oxygenation, but not to levels below the defined thresholds. The major differences in the two measures of oxygenation included the following: a) Sjvo2 more consistently reflected a reduction in oxygenation during hyperventilation; b) Pbto2 was affected more by changes in arterial Po2; and c) during severe global ischemia, Pbto2 decreased to 0 and remained at 0, whereas Sjvo2 initially decreased but then increased again as cerebral blood flow ceased, and the only blood in the jugular bulb was of extracerebral origin.

CONCLUSIONS

The two monitors provide complimentary information, and neither monitor alone identifies all episodes of ischemia. The best strategy for using these monitors is to take advantage of the unique features of each monitor. Sjvo2 should be used as a monitor of global oxygenation; but Pbto2 should be used as a monitor of local oxygenation, ideally with the catheter placed in an area of the brain that is vulnerable to ischemia but that may be salvageable with appropriate treatment.

Current status of neuroprotection trials for traumatic brain injury: lessons from animal models and clinical studies

Laboratory studies have identified numerous potential therapeutic interventions that might have clinical application for the treatment of human traumatic brain injury. Many of these therapies have progressed into human clinical trials in severe traumatic brain injury. Numerous trials have been completed, and many others have been prematurely terminated or are currently in various phases of testing. The results of the completed Phase III trials have been generally disappointing, compared with the expectations produced by the successes of these interventions in animal laboratory studies. In this review, we summarize the current status of human traumatic brain injury clinical trials, as well as the animal laboratory studies that led to some of these trials. We summarize criteria for conducting clinical trials in severe traumatic brain injury, with suggestions for future improvements. We also attempt to identify factors that might contribute to the discrepancies between animal and human trials, and we propose recommendations that could help investigators avoid certain pitfalls in future clinical trials in traumatic brain injury.

Relationship between global and cortical cerebral blood flow in patients with head injuries

OBJECTIVE: The goal of this study was to analyze the use of thermal diffusion-cerebral blood flow (TD-CBF) monitoring as a continuous monitoring method for patients with head injuries in the intensive care unit. METHODS: The TD-CBF probe was placed on normal-appearing frontal or parietal cortex at the time of surgery to treat traumatic intracranial hematomas in 35 patients, and cortical cerebral blood flow (CBF) was monitored for up to 7 days after surgery. We compared TD-CBF values with global CBF values measured by the standard Kety-Schmidt technique, and we compared changes in TD-CBF with changes in jugular venous oxygen saturation observed during intracranial pressure elevations. RESULTS: The average value for the global CBF measurements was 50.5+/-0.9 ml/100 g/min and that for the TD-CBF measurements was 60.5+/-1.4 ml/100 g/min; the average difference was 9.3+/-1.2 ml/100 g/min. The overall slope of the regression between the global CBF and TD-CBF measurements (n = 206) was 0.636 (comparison of observed slope with a slope of 0, P < 0.001). The relationship between the TD-CBF and global CBF values during 546 episodes of increased intracranial pressure was examined by comparing the changes in TD-CBF with the changes in jugular venous oxygen saturation. When the change in TD-CBF was at least 10 ml/100 g/min during an intracranial pressure elevation, the TD-CBF change reflected the change in jugular venous oxygen saturation on 85% of the occasions. CONCLUSION: The TD-CBF method is very convenient because of the continuous and automatic nature of the measurements. Most of the time, a change in TD-CBF indicated a similar change in global CBF. However, the limitations of local measurements of CBF must be kept in mind during therapeutic decision-making.

Effect of glucose administration on contusion volume after moderate cortical impact injury in rats

Previous studies had shown that pre- and postinjury glucose administration increased brain injury caused by a mild cortical impact injury only when the traumatic injury was complicated by a secondary ischemic insult. The purpose of this study was to examine the effect of pre- and postinjury glucose administration on a more severe cortical impact injury, where primary ischemia occurs at the site of the impact. Long Evans rats who were fasted overnight and anesthetized with isoflurane were subjected to a 5-m/sec, 2.5-mm impact injury. The animals were randomly assigned one of the following treatments: (1) 2.2 g/kg glucose in 4 ml of saline, 20 min prior to injury; (2) 2.0 g/kg glucose in 4 ml of saline, 20 min after injury; or (3) 4 ml of saline either 20 min before injury or 20 min after the injury. At 2 weeks, the animals were sacrificed and the brains were examined for contusion volume and for neuronal loss in CA1 and CA3 regions of the hippocampus. Contusion volume was increased from a median value of 23 mm3 in the saline-infused animals to 34 mm3 in the preimpact glucose infusion animals (p=0.005). Postimpact glucose infusion had no effect on contusion volume. Neuron density in CA1 and CA3 regions of the hippocampus was similar in all three treatment groups. These studies support the hypothesis that glucose administration adversely affects experimental traumatic brain injury in those circumstances where the trauma is complicated by primary cerebral ischemia, such as around cortical contusions.

Early cerebral blood volume after severe traumatic brain injury in patients with early cerebral ischemia

Recent early cerebral blood flow (CBF) studies on severe head injury have revealed ischemia in a substantial number of patients with a variety of CT diagnoses. However, the underlying derangements causing this early ischemia are unknown, but cerebral blood volume (CBV) measurements might offer some insight into this pathology. Therefore, acute CBF and CBV measurements were performed in 51 adult severely head injured patients within 24 hours after injury. For this purpose the stable Xenon-CT procedure was used for assessment of CBF, and a dynamic CT imaging technique was used for determining CBV. All ischemic patients were found among 35 subjects studied within 4 hours after injury (31%). Based on the occurrence of regional ischemia seven patients with varying anatomical lesions on CT were selected for comparison between CBF and CBV in ischemic and non-ischemic areas. Both CBF (p < 0.02) and CBV (p < 0.02) exhibited significantly lower values in the ischemic zones. Ten patients showing a subdural hematoma (SDH) were studied preceding surgery and seven were ischemic in at least one lobe or brainstem. Ipsilateral CBF was lower than CBF in the contralateral side (p < 0.1). CBV at the ipsilateral side was significantly reduced compared to the contralateral side (p < 0.05). Follow-up studies were performed in three ischemic patients and in one borderline ischemic patient immediately after removal of SDH showing a striking increase in both CBF and CBV. In the remaining 26 subjects follow-up studies were obtained between day 2 and day 8 and all patients showed CBF values within the normal range. These data evidently support the suggestion that compromise of the microvasculature is the cause of early ischemia, rather than vasospasm of the larger conductance vessels. This has implications for acute post-traumatic therapeutical strategies and management of the severely head injured patient and may lead to testing of new drugs that are effective in interfering with processes causing this ischemia.

Craniocerebral trauma: protection and retrieval of the neuronal population after injury

OBJECTIVE

To review the consequences of mechanical injury to the brain with an emphasis on factors that may explain the variability of outcomes and how this might be influenced.

METHODS

Information regarding the pathophysiology of traumatic brain damage contained in original scientific reports and in review articles published in recent years was reviewed from the perspective of a clinical neurosurgeon and a neuropathologist, each with major research interests in traumatic brain damage. The information was compiled on the basis of the knowledge of and personal selection of articles that were identified through selective literature searches and current awareness profiles. A systematic literature review was not conducted.

RESULTS

Mechanical input affects neuronal and vascular elements and is translated into biological effects on the brain through a complex series of interacting cellular and molecular events. Whether these lead to permanent structural damage or to resolution and recovery is determined by the balance between processes that, on the one hand, mediate the effects of initial injury and subsequent secondary insults and, on the other, are manifestations of the brain's protective, reparative response. Experimental and clinical research has identified opportunities for altering the balance in a way that might promote recovery, but data demonstrating that this can lead to substantial clinical benefit are lacking. Recent evidence of genetically determined, individual susceptibility to the effects of injury may explain some of the puzzling variability in outcome after apparently similar insults and may also provide new opportunities for treatment.

CONCLUSION

The understanding of traumatic brain damage that is being gained from recent research is widening and broadening perspectives from the traditional focus on mechanical, vascular, and metabolic effects to encompass wider, neurobiological issues, drawn from the fields of neurodevelopment, neuroplasticity, neurodegeneration, and neurogenetics. Neurotrauma is a fascinating area of neuroscience research, with promise for the translation of knowledge to improved clinical management and outcome.

Factors affecting excitatory amino acid release following severe human head injury

OBJECT

Recent animal studies demonstrate that excitatory amino acids (EAAs) play a major role in neuronal damage after brain trauma and ischemia. However, the role of EAAs in patients who have suffered severe head injury is not understood. Excess quantities of glutamate in the extracellular space may lead to uncontrolled shifts of sodium, potassium, and calcium, disrupting ionic homeostasis, which may lead to severe cell swelling and cell death. The authors evaluated the role of EEAs in human traumatic brain injury.

METHODS

In 80 consecutive severely head injured patients, a microdialysis probe was placed into the gray matter along with a ventriculostomy catheter or an intracranial pressure (ICP) monitor for 4 days. Levels of EAAs and structural amino acids were analyzed using high-performance liquid chromatography. Multifactorial analysis of the amino acid pattern was performed and its correlations with clinical parameters and outcome were tested. The levels of EAAs were increased up to 50 times normal in 30% of the patients and were significantly correlated to levels of structural amino acids both in each patient and across the whole group (p < 0.01). Secondary ischemic brain injury and focal contusions were most strongly associated with high EAA levels (27+/-22 micromol/L). Sustained high ICP and poor outcome were significantly correlated to high levels of EAAs (glutamate > 20 micromol/L; p < 0.01).

CONCLUSIONS

The release of EAAs is closely linked to the release of structural amino acids and may thus reflect nonspecific development of membrane micropores, rather than presynaptic neuronal vesicular exocytosis. The magnitude of EAA release in patients with focal contusions and ischemic events may be sufficient to exacerbate neuronal damage, and these patients may be the best candidates for treatment with glutamate antagonists in the future.

Factors affecting excitatory amino acid release following severe human head injury

Recent animal studies demonstrate that excitatory amino acids (EAAs) play a major role in neuronal damage after brain trauma and ischemia. However, the role of EAAs in patients who have suffered severe head injury is not understood. Excess quantities of glutamate in the extracellular space may lead to uncontrolled shifts of sodium, potassium, and calcium, disrupting ionic homeostasis, which may lead to severe cell swelling and cell death. The authors evaluated the role of EEAs in human traumatic brain injury.

In 80 consecutive severely head injured patients, a microdialysis probe was placed into the gray matter along with a ventriculostomy catheter or an intracranial pressure (ICP) monitor for 4 days. Levels of EAAs and structural amino acids were analyzed using high-performance liquid chromatography. Multifactorial analysis of the amino acid pattern was performed and its correlations with clinical parameters and outcome were tested. The levels of EAAs were increased up to 50 times normal in 30% of the patients and were significantly correlated to levels of structural amino acids both in each patient and across the whole group (p < 0.01). Secondary ischemic brain injury and focal contusions were most strongly associated with high EAA levels (27 ± 22 μmol/L). Sustained high ICP and poor outcome were significantly correlated to high levels of EAAs (glutamate > 20 μmol/L; p < 0.01).

The release of EAAs is closely linked to the release of structural amino acids and may thus reflect nonspecific development of membrane micropores, rather than presynaptic neuronal vesicular exocytosis. The magnitude of EAA release in patients with focal contusions and ischemic events may be sufficient to exacerbate neuronal damage, and these patients may be the best candidates for treatment with glutamate antagonists in the future.

Cerebral complications of nonaccidental head injury in childhood

Patterns of cerebral parenchymal injury and their relationship to outcome morbidity are evaluated in this retrospective study of 14 children with confirmed nonaccidental head injury (NAHI). The mean age at time of injury was 12 months 6 days, mean Children's Coma Score was 5.36, and mean postinjury follow-up was 17 months 12 days. All patients had acute subdural hematoma (interhemispheric or convexity) on initial CT imaging. Two major groups of children were identified from initial CT scans; those with diffuse cerebral hypoattenuation (n = 7) and those with focal cerebral hypoattenuation (n = 7). The two groups differed significantly by age (diffuse group, mean age 5 months 9 days +/- 36 days; focal group, mean age 19 months 3 days +/- 6 months 9 days; P < 0.01) and ultimate type and extent of parenchymal damage. Outcome was generally poor in both groups (mean Children's Outcome Score of III/IV). Cerebral infarction developed in all survivors. Most common were hemispheric necrosis after hemispheric swelling subjacent to an ipsilateral convexity acute subdural hematoma (n = 5); distribution of the posterior cerebral artery (n = 4) or callosomarginal branch of the anterior cerebral artery (n = 4); and borderzone infarctions (n = 4). Of 14 children, 11 (79%) had early posttraumatic seizures (EPTS). Clinical progression of symptoms was confirmed in nine patients (mean Childrens Coma Score was 4.0 +/- 0.33). None had a lucid interval. This is the first study using strict inclusion criteria that documents the range of infarction patterns and potential age-dependent differences in postinjury response cascades after nonaccidental head injury.

Regional cerebral blood volume after severe head injury in patients with regional cerebral ischemia

OBJECTIVE

Recent early cerebral blood flow (CBF) studies in cases of severe head injury have revealed ischemia in a substantial number of patients with a variety of computed tomographically demonstrated diagnoses. The underlying derangements causing this early ischemia are unknown, but cerebral blood volume (CBV) measurements might offer some insight into this pathological abnormality.

METHODS

For this purpose, stable xenon-enhanced computed tomography was used for assessment of CBF, and a dynamic computed tomographic imaging technique was used for determining CBV. Based on the occurrence of regional ischemia (CBF < 20 ml/100 g/min), seven patients with varying anatomic lesions revealed by computed tomography were identified for comparison between CBF and CBV in ischemic and nonischemic areas.

RESULTS

Both CBF (15+/-4.3 versus 34+/-11 g/min, P < 0.002) and CBV (2.5+/-1.0 versus 4.9+/-1.9 ml/100 g) exhibited significantly lower values in the ischemic zones than in the nonischemic zones (means+/-standard deviations). Among 26 patients with or without ischemia observed during their initial follow-up studies, which were conducted between Days 2 and 8, all patients showed CBF and CBV values within the low-normal range.

CONCLUSION

These data evidently support the suggestion that compromise of the microvasculature is the cause of early ischemia, rather than vasospasm of the larger conductance vessels.

Increased free radical production due to subdural hematoma in the rat: effect of increased inspired oxygen fraction

Acute subdural hematoma (ASDH) complicates about 15%-20% of severe head injury patients and is one of the major causes for bad outcome, yet the pathomechanisms involved are not well understood. This study has employed a recently developed technique to determine whether ASDH induces free radicals in the underlying brain. We also studied the effect of increased inspired oxygen fraction (FiO2) on free radical production, both in the normal rat brain and after ASDH induction. Twelve male Sprague Dawley rats were studied over 5 h (2 h of FiO2 = 30%, 3 h of FiO2 = 100%). Hydroxyl radical production was measured with microdialysis using the salicylate trapping technique by quantitating the 2,3 dihydroxy benzoic acid (2,3 DHBA) and 2,5 dihydroxy benzoic acid (2,5 DHBA), degradation products, in either noninjured brain (n = 6) or after ASDH (n = 6). Both 2,3 DHBA and 2,5 DHBA increased significantly by 39% and 108%, respectively, after the induction of the SDH (p < 0.05). By increasing the FiO2 to 100%, 2 h after ASDH induction, the 2,3 DHBA and 2,5 DHBA further increased only slightly (ns). After increasing the FiO2 to 100% in the noninjured group, the mean level of 2,3 DHBA increased by 56% (p = 0.06, ns). The level of 2,5 DHBA in the dialysate increased significantly by 56% (p < 0.05), when the FiO2 was increased to 100% ASDH results in a significant increase in free radical production. At the same time, prolonged increase in FiO2 does not lead to further increase in free radical production in the injured brain.

Intraoperative monitoring of substrate delivery during aneurysm and hematoma surgery: initial experience in 16 patients

The effects of proximal occlusion of the parent artery during aneurysm surgery in humans are not fully understood, although this method is widely used. The reduction in substrate that can be tolerated by normal and subarachnoid hemorrhage (SAH)-affected brain is unknown. Therefore, the authors measured brain oxygen tension (brain PO2), carbon dioxide tension (brain PCO2), pH, and hemoglobin oxygen (HbO2) saturation before and after temporary occlusion in 12 patients with aneurysms. The effect of removal of a traumatic intracranial hematoma on cerebral oxygenation was also studied in four severely head injured patients. A multiparameter sensor was placed in the cortex of interest and locked by means of a specially designed skull bolt. The mean arterial blood pressure, inspired O2 fraction, and end-tidal PCO2 were analyzed. Brain PO2 and HbO2 saturation data were collected every 10 seconds. Descriptive and nonparametric analyses were used to analyze the data. A wide range in baseline PO2 was seen, although a decrease from baseline in brain PO2 was found in all patients. During temporary occlusion, brain PO2 in patients with unruptured aneurysm (seven patients) dropped significantly, from 60 +/- 31 to 27 +/- 17 mm Hg (p < 0.05). In the SAH group (five patients), the brain PO2 dropped from 106 +/- 74 to 87 +/- 73 mm Hg (not significant). Removal of intracranial hematomas in four severely head injured patients resulted in a significant increase in brain PO2, from 13 +/- 9 to 34 +/- 13 mm Hg (p < 0.05). The duration of safe temporary occlusion could not be determined from this group of patients, because none developed postoperative deterioration in their neurological status. However, the data indicate that this technique is useful to detect changes in substrate delivery during intraoperative maneuvers. This study also reemphasizes the need for emergency removal of intracranial hematomas to improve substrate delivery in severely head injured patients.

Clinical trials in traumatic brain injury. What can we learn from previous studies?

Many compounds have now been tested that were expected to ameliorate the secondary ischemic brain damage after severe head injury. Thus far, none of these have been clearly successful. This review is an attempt to identify factors that could be responsible for some of these failures. Recommendations are made that could help to avoid these pitfalls in the future. The usefulness and criteria for use of animal models for traumatic brain injury to depict human head injury are discussed. Clearly, it has now become widely accepted that mechanism-driven trials, in which individual pathophysiological mechanisms are targeted, are preferable in this heterogeneous patient population. Other factors, such as the effect of brain penetration, safety and tolerability of the compound, and the interface between the pharmaceutical industry and academics are a major influence in the success of these trials. Furthermore, different ways of analyzing trials such as sequential analysis and newer, alternative end points should be considered. Pharmacological agents will never be the "magic bullet" for a process as heterogenous in pathophysiological mechanisms as traumatic brain injury. This does not imply that the role of neuroprotective compounds will not be important in the future. New approaches in developing, conducting and analyzing these expensive clinical trials must be devised in the future.

Intraoperative jugular desaturation during surgery for traumatic intracranial hematomas

Traumatic intracranial hematomas which are present on hospital admission or which develop during the hospital course are associated with a worse neurological outcome than diffuse injuries. The purpose of this study was to monitor jugular venous oxygen saturation (Sjvo2) during surgery for evacuation of traumatic intracranial mass lesions, to determine the incidence and the causes of jugular venous desaturation, and to assess the usefulness of Sjvo2 monitoring in this setting. Twenty-five severely head injured patients were monitored during 27 surgical procedures. At the start of the surgical procedure, the median Sjvo2 was 47% (range 25%-89%). Seventeen (63%) of the patients had a Sjvo2 less than 50%. Five patients had extremely low Sjvo2 values (< or = 30%). Upon evacuation of the intracranial hematoma, there was a significant (P < 0.001) increase in the median Sjvo2 to 65% (range 50%-88%). Intracranial hypertension was the primary cause of the low Sjvo2, as confirmed by the response to surgical evacuation. Hypotension (mean arterial pressure < 80 mm Hg) was a contributing factor in seven of the cases of jugular desaturation. The definitive treatment of a traumatic intracranial hematoma is surgical evacuation. However, during the period prior to evacuation of the hematoma, jugular venous desaturation was common, suggesting that monitoring Sjvo2 might provide useful information about the adequacy of cerebral perfusion.