Barbiturate therapy for patients with refractory intracranial hypertension following severe traumatic brain injury: its effects on tissue oxygenation, brain temperature and autoregulation

Association between EEG metrics and continuous cerebrovascular autoregulation assessment: a scoping review

OBJECTIVE

Cerebrovascular autoregulation is defined as the capacity of cerebral blood vessels to maintain stable cerebral blood flow despite changing blood pressure. It is assessed using the pressure reactivity index (the correlation coefficient between mean arterial blood pressure and intracranial pressure). The objective of this scoping review is to describe the existing evidence concerning the association of EEG and cerebrovascular autoregulation in order to identify key concepts and detect gaps in the current knowledge.

METHODS

Embase, MEDLINE, SCOPUS, and Web of Science were searched considering articles between their inception up to September 2023. Inclusion criteria were human (paediatric and adult) and animal studies describing correlations between continuous EEG and cerebrovascular autoregulation assessments.

RESULTS

Ten studies describing 481 human subjects (67% adult, 59% critically ill) were identified. Seven studies assessed qualitative (e.g. seizures, epileptiform potentials) and five evaluated quantitative (e.g. bispectral index, alpha-delta ratio) EEG metrics. Cerebrovascular autoregulation was evaluated based on intracranial pressure, transcranial Doppler, or near infrared spectroscopy. Specific combinations of cerebrovascular autoregulation and EEG metrics were evaluated by a maximum of two studies. Seizures, highly malignant patterns or burst suppression, alpha peak frequency, and bispectral index were associated with cerebrovascular autoregulation. The other metrics showed either no or inconsistent associations.

CONCLUSION

There is a paucity of studies evaluating the link between EEG and cerebrovascular autoregulation. The studies identified included a variety of EEG and cerebrovascular autoregulation acquisition methods, age groups, and diseases allowing for few overarching conclusions. However, the preliminary evidence for the presence of an association between EEG metrics and cerebrovascular autoregulation prompts further in-depth investigations.

Multimodal and autoregulation monitoring in the neurointensive care unit

Given the complexity of cerebral pathology in patients with acute brain injury, various neuromonitoring strategies have been developed to better appreciate physiologic relationships and potentially harmful derangements. There is ample evidence that bundling several neuromonitoring devices, termed "multimodal monitoring," is more beneficial compared to monitoring individual parameters as each may capture different and complementary aspects of cerebral physiology to provide a comprehensive picture that can help guide management. Furthermore, each modality has specific strengths and limitations that depend largely on spatiotemporal characteristics and complexity of the signal acquired. In this review we focus on the common clinical neuromonitoring techniques including intracranial pressure, brain tissue oxygenation, transcranial doppler and near-infrared spectroscopy with a focus on how each modality can also provide useful information about cerebral autoregulation capacity. Finally, we discuss the current evidence in using these modalities to support clinical decision making as well as potential insights into the future of advanced cerebral homeostatic assessments including neurovascular coupling.

Current status and outlook for the management of intracranial hypertension after traumatic brain injury: decompressive craniectomy, therapeutic hypothermia, and barbiturates

INTRODUCTION

Increased intracranial pressure (ICP) has been associated with poor neurological outcomes and increased mortality in patients with severe traumatic brain injury (TBI). Traditionally, ICP-lowering therapies are administered using an escalating approach, with more aggressive options reserved for patients showing no response to first-tier interventions, or with refractory intracranial hypertension.

DEVELOPMENT

The therapeutic value and the appropriate timing for the use of rescue treatments for intracranial hypertension have been a subject of constant debate in literature. In this review, we discuss the main management options for refractory intracranial hypertension after severe TBI in adults. We intend to conduct an in-depth revision of the most representative randomised controlled trials on the different rescue treatments, including decompressive craniectomy, therapeutic hypothermia, and barbiturates. We also discuss future perspectives for these management options.

CONCLUSIONS

The available evidence appears to show that mortality can be reduced when rescue interventions are used as last-tier therapy; however, this benefit comes at the cost of severe disability. The decision of whether to perform these interventions should always be patient-centred and made on an individual basis. The development and integration of different physiological variables through multimodality monitoring is of the utmost importance to provide more robust prognostic information to patients facing these challenging decisions.

Difference between brain temperature and core temperature in severe traumatic brain injury: a systematic review

INTRODUCTION

Intensive care management for traumatic brain injury (TBI) patients aims to prevent secondary cerebral damage. Targeted temperature management is one option to prevent cerebral damage, as hypothermia may have protective effects. By conducting a systematic literature review we evaluated: 1) the presence of a temperature difference (gradient) between brain temperature (Tb) and core temperature (Tc) in TBI patients; and 2) clinical factors associated with reported differences.

EVIDENCE ACQUISITION

The PubMed database was systematically searched using Mesh terms and key words, and Web of Sciences was assessed for additional article citations. We included studies that continuously and simultaneously measured Tb and Tc in severe TBI patients. The National Institutes of Health (NIH) quality assessment tool for observational cohort and cross-sectional studies was modified to fit the purpose of our study. Statistical data were extracted for further meta-analyses.

EVIDENCE SYNTHESIS

We included 16 studies, with a total of 480 patients. Clinical heterogeneity consisted of Tb/Tc measurement site, measurement device, physiological changes, local protocols, and medical or surgical interventions. The studies have a high statistical heterogeneity (I2). The pooled mean temperature gradient between Tb and Tc was +0.14 °C (95% confidence interval: 0.03 to 0.24) and ranged from -1.29 to +1.1 °C. Patients who underwent a decompressive (hemi)craniectomy showed lower Tb values compared to Tc found in three studies.

CONCLUSIONS

Studies on Tb and Tc are heterogeneous and show that, on average, Tb and Tc are not clinically significant different in TBI patients (<0.2 °C). Interpretations and interventions of the brain and central temperatures will benefit from standardization of temperature measurements.

The Effect of Electroencephalography Abnormalities on Cerebral Autoregulation in Sedated Ventilated Children

Purpose: To determine the effects of non-ictal electroencephalogram (EEG) changes on cerebrovascular autoregulation (AR) using the cerebral oximetry index (COx). Materials and Methods: Mean arterial blood pressure (MAP), cerebral tissue oxygenation (CrSO2), and EEG were acquired for 96 h. From all of the EEG recordings, 30 min recording segments were extracted using the endotracheal suction events as the guide. EEG recordings were classified as EEG normal and EEG abnormal groups. Each 30 min segment was further divided into six 5 min epochs. Continuous recordings of MAP and CrSO2 by near-infrared spectroscopy (NIRS) were extracted. The COx value was defined as the concordance (R) value of the Pearson correlation between MAP and CrSO2 in a 5 min epoch. Then, an Independent-Samples Mann-Whitney U test was used to analyze the number of epochs within the 30 min segments above various R cutoff values (0.2, 0.3, and 0.4) in normal and abnormal EEG groups. A p-value < 0.05 was considered significant, and all analyses were two-tailed. Results: Among 16 sedated, mechanically ventilated children, 382 EEG recordings of 30 min segments were analyzed. The proportions of epochs in each 30 min segment above the R cutoff values were similar between the EEG normal and EEG abnormal groups (p > 0.05). The median concordance values for CSrO2 and MAP in EEG normal and EEG abnormal groups were similar (0.26 (0.17−0.35) and 0.18 (0.12−0.31); p = 0.09). Conclusions: Abnormal EEG patterns without ictal changes do not affect cerebrovascular autoregulation in sedated and mechanically ventilated children.

Temporal effects of barbiturate coma on intracranial pressure and compensatory reserve in children with traumatic brain injury

Background

The aim was to study the effects of barbiturate coma treatment (BCT) on intracranial pressure (ICP) and intracranial compensatory reserve (RAP index) in children (< 17 years of age) with traumatic brain injury (TBI) and refractory intracranial hypertension (RICH).

Methods

High-resolution monitoring data were used to study the effects of BCT on ICP, mean arterial pressure (MAP), cerebral perfusion pressure (CPP), and RAP index. Four half hour long periods were studied: before bolus injection and at 5, 10, and 24 hours thereafter, respectively, and a fifth tapering period with S-thiopental between < 100 and < 30 μmol/L. S-thiopental concentrations and administered doses were registered.

Results

Seventeen children treated with BCT 2007–2017 with high-resolution data were included; median age 15 (range 6–17) and median Glasgow coma score 7 (range 3–8). Median time from trauma to start of BCT was 44.5 h (range 2.5–197.5) and from start to stop 99.0 h (range 21.0–329.0). Median ICP was 22 (IQR 20–25) in the half hour period before onset of BCT and 16 (IQR 11–20) in the half hour period 5 h later (p = 0.011). The corresponding figures for CPP were 65 (IQR 62–71) and 63 (57–71) (p > 0.05). The RAP index was in the half hour period before onset of BCT 0.6 (IQR 0.1–0.7), in the half hour period 5 h later 0.3 (IQR 0.1–0.7) (p = 0.331), and in the whole BCT period 0.3 (IQR 0.2–0.4) (p = 0.004). Eighty-two percent (14/17) had favorable outcome (good recovery = 8 patients and moderate disability = 6 patients).

Conclusion

BCT significantly reduced ICP and RAP index with preserved CPP. BCT should be considered in case of RICH.

Current status and outlook for the management of intracranial hypertension after traumatic brain injury: decompressive craniectomy, therapeutic hypothermia, and barbiturates

INTRODUCTION

Increased intracranial pressure has been associated with poor neurological outcomes and increased mortality in patients with severe traumatic brain injury. Traditionally, intracranial pressure-lowering therapies are administered using an escalating approach, with more aggressive options reserved for patients showing no response to first-tier interventions, or with refractory intracranial hypertension.

DEVELOPMENT

The therapeutic value and the appropriate timing for the use of rescue treatments for intracranial hypertension have been a subject of constant debate in literature. In this review, we discuss the main management options for refractory intracranial hypertension after severe traumatic brain injury in adults. We intend to conduct an in-depth revision of the most representative randomised controlled trials on the different rescue treatments, including decompressive craniectomy, therapeutic hypothermia, and barbiturates. We also discuss future perspectives for these management options.

CONCLUSIONS

The available evidence appears to show that mortality can be reduced when rescue interventions are used as last-tier therapy; however, this benefit comes at the cost of severe disability. The decision of whether to perform these interventions should always be patient-centred and made on an individual basis. The development and integration of different physiological variables through multimodality monitoring is of the utmost importance to provide more robust prognostic information to patients facing these challenging decisions.

Early prediction of neurological outcome after barbiturate coma therapy in patients undergoing brain tumor surgery

After a difficult brain tumor surgery, refractory intracranial hypertension (RICH) may occur due to residual tumor or post-operative complications such as hemorrhage, infarction, and aggravated brain edema. We investigated which predictors are associated with prognosis when using barbiturate coma therapy (BCT) as a second-tier therapy to control RICH after brain tumor surgery. The study included adult patients who underwent BCT after brain tumor surgery between January 2010 and December 2016. The primary outcome was neurological status upon hospital discharge, which was assessed using the Glasgow Outcome Scale (GOS). In the study period, 4,296 patients underwent brain tumor surgery in total. Of these patients, BCT was performed in 73 patients (1.7%). Among these 73 patients, 56 (76.7%) survived to discharge and 25 (34.2%) showed favorable neurological outcomes (GOS scores of 4 and 5). Invasive monitoring of intracranial pressure (ICP) was performed in 60 (82.2%) patients, and revealed that the maximal ICP within 6 h after BCT was significantly lower in patients with favorable neurological outcome as well as in survivors (p = 0.008 and p = 0.028, respectively). Uncontrolled RICH (ICP ≥ 22 mm Hg within 6 h of BCT) was an important predictor of mortality after BCT (adjusted hazard ratio 12.91, 95% confidence interval [CI] 2.788–59.749), and in particular, ICP ≥ 15 mm Hg within 6 h of BCT was associated with poor neurological outcome (adjusted odds ratio 9.36, 95% CI 1.664–52.614). Therefore, early-controlled ICP after BCT was associated with clinical prognosis. There were no significant differences in the complications associated with BCT between the two neurological outcome groups. No BCT-induced death was observed. The active and timely control of RICH may be beneficial for clinical outcomes in patients with RICH after brain tumor surgery.

Intracranial Hypertension and Cerebral Autoregulation: A Systematic Review and Meta-Analysis

OBJECTIVE

To present a systematic review and meta-analysis to establish the relation between cerebral autoregulation (CA) and intracranial hypertension.

METHODS

An electronic search using the term "Cerebral autoregulation and intracranial hypertension" was designed to identify studies that analyzed cerebral blood flow autoregulation in patients undergoing intracranial pressure (ICP) monitoring. The data were used in meta-analyses and sensitivity analyses.

RESULTS

A static CA technique was applied in 10 studies (26.3%), a dynamic technique was applied in 25 studies (65.8%), and both techniques were used in 3 studies (7.9%). Static CA studies using the cerebral blood flow technique revealed impaired CA in patients with an ICP ≥20 (standardized mean difference [SMD] 5.44%, 95% confidence interval [CI] 0.25-10.65, P = 0.04); static CA studies with transcranial Doppler revealed a tendency toward impaired CA in patients with ICP ≥20 (SMD -7.83%, 95% CI -17.52 to 1.85, P = 0.11). Moving correlation studies reported impaired CA in patients with ICP ≥20 (SMD 0.06, 95% CI 0.07-0.14, P < 0.00001). A comparison of CA values and mean ICP revealed a correlation between greater ICP and impaired CA (SMD 5.47, 95% CI 1.39-10.1, P = 0.01). Patients with ICP ≥20 had an elevated risk of impaired CA (OR 2.27, 95% CI 1.20-4.31, P = 0.01).

CONCLUSIONS

A clear tendency toward CA impairment was observed in patients with increased ICP.

Cerebral Perfusion Pressure Targets Individualized to Pressure-Reactivity Index in Moderate to Severe Traumatic Brain Injury: A Systematic Review

Traumatic brain injury (TBI) frequently triggers a disruption of cerebral autoregulation. The cerebral perfusion pressure (CPP) at which autoregulation is optimal ("CPPopt") varies between individuals, and can be calculated based on fluctuations between arterial blood pressure and intracranial pressure. This review assesses the effect of individualizing CPP targets to pressure reactivity index (a measure of autoregulation) in patients with TBI. Cochrane Central Register of Controlled Trials, MEDLINE®, Embase, and Cumulative Index of Nursing and Allied Health Literature were searched in March 2015 for studies assessing the effect of targeting CPPopt in TBI. We included all studies that assessed the impact of targeting CPPopt on outcomes including mortality, neurological outcome, and physiological changes. Risk of bias was assessed using the RTI Item Bank and evidence quality was considered using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria. Eight cohort studies (based on six distinct data sets) assessing the association between CPPopt and mortality, Glasgow Outcome Scale and physiological measures in TBI were included. The quality of evidence was deemed very low based on the GRADE criteria. Although the data suggest an association between variation from CPPopt and poor clinical outcome at 6 months, the quality of evidence prevents firm conclusions, particularly regarding causality, from being drawn. Available data suggest that targeting CPPopt might represent a technique to improve outcomes following TBI, but currently there is insufficient high-quality data to support a recommendation for use in clinical practice. Further prospective, randomized controlled studies should be undertaken to clarify its role in the acute management of TBI.

Monitoring of cerebral autoregulation

Pressure autoregulation is an important hemodynamic mechanism that protects the brain against inappropriate fluctuations in cerebral blood flow in the face of changing cerebral perfusion pressure (CPP). Static autoregulation represents how far cerebrovascular resistance changes when CPP varies, and dynamic autoregulation represents how fast these changes happen. Both have been monitored in the setting of neurocritical care to aid prognostication and contribute to individualizing CPP targets in patients. Failure of autoregulation is associated with a worse outcome in various acute neurological diseases. Several studies have used transcranial Doppler ultrasound, intracranial pressure (ICP with vascular reactivity as surrogate measure of autoregulation), and near-infrared spectroscopy to continuously monitor the impact of spontaneous fluctuations in CPP on cerebrovascular physiology and to calculate derived variables of autoregulatory efficiency. Many patients who undergo such monitoring demonstrate a range of CPP in which autoregulatory efficiency is optimal. Management of patients at or near this optimal level of CPP is associated with better outcomes in traumatic brain injury. Many of these studies have utilized the concept of the pressure reactivity index, a correlation coefficient between ICP and mean arterial pressure. While further studies are needed, these data suggest that monitoring of autoregulation could aid prognostication and may help identify optimal CPP levels in individual patients.

Monitoring of brain and systemic oxygenation in neurocritical care patients

Maintenance of adequate oxygenation is a mainstay of intensive care, however, recommendations on the safety, accuracy, and the potential clinical utility of invasive and non-invasive tools to monitor brain and systemic oxygenation in neurocritical care are lacking. A literature search was conducted for English language articles describing bedside brain and systemic oxygen monitoring in neurocritical care patients from 1980 to August 2013. Imaging techniques e.g., PET are not considered. A total of 281 studies were included, the majority described patients with traumatic brain injury (TBI). All tools for oxygen monitoring are safe. Parenchymal brain oxygen (PbtO2) monitoring is accurate to detect brain hypoxia, and it is recommended to titrate individual targets of cerebral perfusion pressure (CPP), ventilator parameters (PaCO2, PaO2), and transfusion, and to manage intracranial hypertension, in combination with ICP monitoring. SjvO2 is less accurate than PbtO2. Given limited data, NIRS is not recommended at present for adult patients who require neurocritical care. Systemic monitoring of oxygen (PaO2, SaO2, SpO2) and CO2 (PaCO2, end-tidal CO2) is recommended in patients who require neurocritical care.

Cerebrovascular Pressure Reactivity in Children With Traumatic Brain Injury

OBJECTIVE

Traumatic brain injury is a significant cause of morbidity and mortality in children. Cerebral autoregulation disturbance after traumatic brain injury is associated with worse outcome. Pressure reactivity is a fundamental component of cerebral autoregulation that can be estimated using the pressure-reactivity index, a correlation between slow arterial blood pressure, and intracranial pressure fluctuations. Pressure-reactivity index has shown prognostic value in adult traumatic brain injury, with one study confirming this in children. Pressure-reactivity index can identify a cerebral perfusion pressure range within which pressure reactivity is optimal. An increasing difference between optimal cerebral perfusion pressure and cerebral perfusion pressure is associated with worse outcome in adult traumatic brain injury; however, this has not been investigated in children. Our objective was to study pressure-reactivity index and optimal cerebral perfusion pressure in pediatric traumatic brain injury, including associations with outcome, age, and cerebral perfusion pressure.

DESIGN

Prospective observational study.

SETTING

ICU, Royal Children's Hospital, Melbourne, Australia.

PATIENTS

Patients with traumatic brain injury who are 6 months to 16 years old, are admitted to the ICU, and require arterial blood pressure and intracranial pressure monitoring.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Arterial blood pressure, intracranial pressure, and end-tidal CO2 were recorded electronically until ICU discharge or monitoring cessation. Pressure-reactivity index and optimal cerebral perfusion pressure were computed according to previously published methods. Clinical data were collected from electronic medical records. Outcome was assessed 6 months post discharge using the modified Glasgow Outcome Score. Thirty-six patients were monitored, with 30 available for follow-up. Pressure-reactivity index correlated with modified Glasgow Outcome Score (Spearman ρ = 0.42; p = 0.023) and was higher in patients with unfavorable outcome (0.23 vs -0.09; p = 0.0009). A plot of pressure-reactivity index averaged within 5 mm Hg cerebral perfusion pressure bins showed a U-shape, reaffirming the concept of cerebral perfusion pressure optimization in children. Optimal cerebral perfusion pressure increased with age (ρ = 0.40; p = 0.02). Both the duration and magnitude of negative deviations in the difference between cerebral perfusion pressure and optimal cerebral perfusion pressure were associated with unfavorable outcome.

CONCLUSIONS

In pediatric patients with traumatic brain injury, pressure-reactivity index has prognostic value and can identify cerebral perfusion pressure targets that may differ from treatment protocols. Our results suggest but do not confirm that cerebral perfusion pressure targeting using pressure-reactivity index as a guide may positively impact on outcome. This question should be addressed by a prospective clinical study.

Brain tissue oxygenation, lactate-pyruvate ratio, and cerebrovascular pressure reactivity monitoring in severe traumatic brain injury: systematic review and viewpoint

BACKGROUND

Prevention and detection of secondary brain insults via multimodality neuromonitoring is a major goal in patients with severe traumatic brain injury (TBI).

OBJECTIVE

Explore the underlying pathophysiology and clinical outcome correlates as it pertains to combined monitoring of ≥2 from the following variables: partial brain tissue oxygen tension (PbtO(2)), pressure reactivity index (PRx), and lactate pyruvate ratio (LPR).

METHODS

Data sources included Medline, EMBASE, and evidence-based databases (Cochrane DSR, ACP Journal Club, DARE, and the Cochrane Controlled Trials Register). The PRISMA recommendations were followed. Two authors independently selected articles meeting inclusion criteria. Studies enrolled adults who required critical care and monitoring in the setting of TBI. Included studies reported on correlations between the monitored variables and/or reported on correlations of the variables with clinical outcomes.

RESULTS

Thirty-four reports were included (32 observational studies and 2 randomized controlled trials) with a mean sample size of 34 patients (range 6-223), and a total of 1,161 patient-observations. Overall methodological quality was moderate. Due to inter-study heterogeneity in outcomes of interest, study design, and in both number and type of covariates included in multivariable analyses, quantitative synthesis of study results was not undertaken.

CONCLUSION

Several literature limitations were identified including small number of subjects, lack of clinical outcome correlations, inconsistent probe location, and overall moderate quality among the included studies. These limitations preclude any firm conclusions; nevertheless we suggest that the status of cerebrovascular reactivity is not only important for cerebral perfusion pressure optimization but should also inform interpretation and interventions targeted on PbtO(2) and LPR. Assessment of reactivity can be the first step in approaching the relations among cerebral blood flow, oxygen delivery, demand, and cellular metabolism.

Energy expenditure during barbiturate coma

BACKGROUND

Barbiturate coma may have a significant effect on metabolic rate, but the phenomenon is not extensively studied. The primary purpose of the current study was to compare the metabolic rate of general critical care patients with those requiring barbiturate coma. A secondary purpose was to evaluate the accuracy of the Penn State prediction equation between these 2 groups of patients.

MATERIALS AND METHODS

Indirect calorimetry was used to measure the resting metabolic rate of mechanically ventilated, critically ill patients in a barbiturate coma and those of similar height, weight, and age but not in a barbiturate coma. Measurements of resting metabolic rate were compared with predictions using the Penn State equation accounting for body size, body temperature, and minute ventilation.

RESULTS

The barbiturate coma group had a lower resting metabolic rate than the control group that remained lower even after adjustment for predicted healthy metabolic rate and maximum body temperature (1859 ± 290 vs 2037 ± 289 kcal/d, P = .020). When minute ventilation was also included in the analysis, the resting metabolic rate between the groups became statistically insignificant (1929 ± 229 vs 2023 ± 226 kcal/d, P = .142). The Penn State equation, which uses these variables, was accurate in 73% of the control patients and also the barbiturate coma patients.

CONCLUSION

Resting metabolic rate is moderately reduced in barbiturate coma, but the decrease is out of proportion with changes in body temperature. However, if both body temperature and minute ventilation are considered, then the change is predictable.

Parenchymal brain oxygen monitoring in the neurocritical care unit

Patients admitted to the neurocritical care unit (NCCU) often have serious conditions that can be associated with high morbidity and mortality. Pharmacologic agents or neuroprotectants have disappointed in the clinical environment. Current NCCU management therefore is directed toward identification, prevention, and treatment of secondary cerebral insults that evolve over time and are known to aggravate outcome. This strategy is based on a variety of monitoring techniques including use of intraparenchymal monitors. This article reviews parenchymal brain oxygen monitors, including the available technologies, practical aspects of use, the physiologic rationale behind their use, and patient management based on brain oxygen.

Brain oxygen tension monitoring following penetrating ballistic-like brain injury in rats

While brain oxygen tension (PbtO(2)) monitoring is an important parameter for evaluating injury severity and therapeutic efficiency in severe traumatic brain injury (TBI) patients, many factors affect the monitoring. The goal of this study was to identify the effects of FiO(2) (fraction of inspired oxygen) on PbtO(2) in uninjured anesthetized rats and measure the changes in PbtO(2) following penetrating ballistic-like brain injury (PBBI). Continuous PbtO(2) monitoring in uninjured anesthetized rats showed that PbtO(2) response was positively correlated with FiO(2) (0.21-0.35) but PbtO(2) remained stable when FiO(2) was maintained at ∼0.26. Importantly, although increasing FiO(2) from 0.21 to 0.35 improved P(a)O(2), it concomitantly reduced pH levels and elevated P(a)CO(2) values out of the normal range. However, when the FiO(2) was maintained between 0.26 and 0.30, the pH and P(a)O(2) levels remained within the normal or clinically acceptable range. In PBBI rats, PbtO(2) was significantly reduced by ∼40% (16.9 ± 1.2 mm Hg) in the peri-lesional region immediately following unilateral, frontal 10% PBBI compared to sham rats (28.6 ± 1.7 mm Hg; mean ± SEM, p<0.05) and the PBBI-induced reductions in PbtO(2) were sustained for at least 150 min post-PBBI. Collectively, these results demonstrate that FiO(2) affects PbtO(2) and that PBBI produces acute and sustained hypoxia in the peri-lesional region of the brain injury. This study provides important information for the management of PbtO(2) monitoring in this brain injury model and may offer insight for therapeutic strategies targeted to improve the hypoxia/ischemia state in the penetrating-type brain injury.

Pediatric traumatic brain injury: an update

PURPOSE OF REVIEW

The developing brain is particularly vulnerable to traumatic brain injury (TBI), leading to frequent disability or death. This article is an update of the pediatric specificities of TBI management.

RECENT FINDINGS

We review the evidences with regards to general management and therapeutic goals to prevent secondary injuries in pediatric TBI patients. Recent controversies in neurocritical care, such as multimodal neuromonitoring, hyperventilation, barbiturate coma, hypothermia, and decompressive surgery, are also highlighted.

SUMMARY

Many therapeutic modalities in pediatric TBI have a low level of evidence. Further research is needed to establish clear resuscitation goals. Universal objectives may not be suitable for all patients; intensive neuromonitoring may help in identifying individual therapeutic goals and guiding the selection of treatments.

Contemporary management of traumatic intracranial hypertension: is there a role for therapeutic hypothermia?

OBJECTIVE

Intracranial hypertension (ICH) remains the single most difficult therapeutic challenge for the acute management of severe traumatic brain injury (TBI). We reviewed the published trials of therapeutic moderate hypothermia to determine its effect on ICH and compared its efficacy to other commonly used therapies for ICH.

METHODS

A PubMed database search was done using various combinations of the search terms "brain injury," "therapeutic hypothermia," "intracranial hypertension," "barbiturates," "mannitol," "hypertonic saline," "hyperventilation," "decompressive craniectomy," and "CSF drainage."

RESULTS

We identified 11 prospective randomized clinical TBI trials comparing hypothermia vs. normothermia treatment for which intracranial pressure (ICP) data was provided, and 6 prospective cohort studies that provided ICP data before and during hypothermia treatment. In addition, we identified 37 clinical TBI studies of lumbar CSF drainage, mannitol, hyperventilation, barbiturates, hypertonic saline, and decompressive craniectomy that provided pre- and posttreatment ICP data. Hypothermia was at least as effective as the traditional therapies for ICH (hyperventilation, mannitol, and barbiturates), but was less effective than hypertonic saline, lumbar CSF drainage, and decompressive craniectomy. Ultimately, however, therapeutic hypothermia does appear to have a favorable risk/benefit profile.

CONCLUSION

Therapeutic moderate hypothermia is as effective, or more effective, than most other treatments for ICH. If used for 2-3 days or less there is no evidence that it causes clinically significant adverse events. The lack of consistent evidence that hypothermia improves long-term neurologic outcome should not preclude consideration of its use for the primary treatment of ICH since no other ICP therapy is held to this standard.

Favorable Outcome in Traumatic Brain Injury Patients With Impaired Cerebral Pressure Autoregulation When Treated at Low Cerebral Perfusion Pressure Levels

BACKGROUND:

Cerebral pressure autoregulation (CPA) is defined as the ability of the brain vasculature to maintain a constant blood flow over a range of different systemic blood pressures by means of contraction and dilatation.

OBJECTIVE:

To study CPA in relation to physiological parameters, treatment, and outcome in a series of traumatic brain injury patients.

METHODS:

In this prospective observational study, 44 male and 14 female patients (age, 15–72 years; mean, 38.7 years; Glasgow Coma Scale score, 4-13; median, 7) were analyzed. Patients were divided into groups on the basis of status of CPA (more pressure active vs more pressure passive) and level of cerebral perfusion pressure (CPP; low vs high CPP). The proportions of favorable outcome in the groups were assessed. Differences in physiological variables in the different groups were analyzed.

RESULTS:

Patients with more impaired CPA treated at CPP levels below median had a significantly higher proportion of favorable outcome compared with patients with more impaired CPA treated at CPP levels above median. No significant difference in outcome was seen between patients with more intact CPA when divided by level of CPP. In patients with more impaired CPA, CPP &lt; 50 mm Hg and CPP &lt; 60 mm Hg were associated with favorable outcome, whereas CPP &gt; 70 mm Hg and CPP &gt; 80 mm Hg were associated with unfavorable outcome. In patients with more intact CPA, no difference in physiological variables was seen between patients with favorable and unfavorable outcomes.

CONCLUSION:

Our results support that in traumatic brain injury patients with impaired CPA, CPP should not be elevated.

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

PRIMARY OBJECTIVE

To review the research literature on pharmacological interventions used in the acute phase of acquired brain injury (ABI) to manage ICP and improve neural recovery.

MAIN OUTCOMES

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

RESULTS

In total, 11 pharmacological interventions used in the acute management of ABI were evaluated. These included propofol, barbiturates, opioids, midazolam, mannitol, hypertonic saline, corticosteroids, progesterone, bradykinin antagonists, dimethyl sulphoxide and cannabinoids. Of these interventions, corticosteroids were found to be contraindicated and cannabinoids were reported as ineffective. The other nine interventions demonstrated some benefit for treatment of acute ABI. However, rarely did these benefits result in improved long-term patient outcomes.

CONCLUSIONS

Substantial research has been devoted to evaluating the use of pharmacological interventions in the acute management of ABI. However, much of this research has focused on the application of individual interventions in small single-site trials. Future research will need to establish larger patient samples to evaluate the benefits of combined interventions within specific patient populations.

Management of intracranial pressure

Although intracranial hypertension may arise from diverse pathology, several basic principles remain paramount to understanding its dynamics; however, the management of elevated intracranial pressure (ICP) may be very complex. Initial management of common ICP exacerbants is important, such as addressing venous outflow obstruction with upright midline head positioning and treating agitation and pain with sedation and analgesia. Surgical decompression of mass effect may rapidly improve ICP elevation, but the impact on outcome is unclear. Considerable effort has been put forth to understand the roles of multimodal intensive care monitoring, osmolar therapy, cerebral metabolic suppression, and temperature augmentation in the advanced management of elevated ICP. Establishing a protocol-driven approach to the management of ICP enables the rapid bedside assessment of multiple physiologic variables to implement appropriate treatments, which limit the risk of developing secondary brain injury.

Barbiturates for the treatment of intracranial hypertension after traumatic brain injury

In their article on the use of barbiturates for the treatment of intracranial hypertension after traumatic brain injury, Perez-Barcena and colleagues conclude that thiopental was more effective than pentobarbital in decreasing intracranial pressure. Here we discuss the limitations of this study and review areas of controversy surrounding barbiturate use in neurocritical care.