Guidelines for the management of severe traumatic brain injury. VIII. Intracranial pressure thresholds

[Therapeutic hypothermia for severe traumatic brain injury]

Therapeutic hypothermia (TH) is considered a standard of care in the post-resuscitation phase of cardiac arrest. In experimental models of traumatic brain injury (TBI), TH was found to have neuroprotective properties. However, TH failed to demonstrate beneficial effects on neurological outcome in patients with TBI. The absence of benefits of TH uniformly applied in TBI patients should not question the use of TH as a second-tier therapy to treat elevated intracranial pressure. The management of all the practical aspects of TH is a key factor to avoid side effects and to optimize the potential benefit of TH in the treatment of intracranial hypertension. Induction of TH can be achieved with external surface cooling or with intra-vascular devices. The therapeutic target should be set at a 35°C using brain temperature as reference, and should be maintained at least during 48 hours and ideally over the entire period of elevated intracranial pressure. The control of the rewarming phase is crucial to avoid temperature overshooting and should not exceed 1°C/day. Besides its use in the management of intracranial hypertension, therapeutic cooling is also essential to treat hyperthermia in brain-injured patients. In this review, we will discuss the benefit-risk balance and practical aspects of therapeutic temperature management in TBI patients.

Marked reduction in mortality in patients with severe traumatic brain injury

OBJECT

In spite of evidence that use of the Brain Trauma Foundation Guidelines for the Management of Severe Traumatic Brain Injury (Guidelines) would dramatically reduce morbidity and mortality, adherence to these Guidelines remains variable across trauma centers. The authors analyzed 2-week mortality due to severe traumatic brain injury (TBI) from 2001 through 2009 in New York State and examined the trends in adherence to the Guidelines.

METHODS

The authors calculated trends in adherence to the Guidelines and age-adjusted 2-week mortality rates between January 1, 2001, and December 31, 2009. Univariate and multivariate logistic regression analyses were performed to evaluate the effect of time period on case-fatality. Intracranial pressure (ICP) monitor insertion was modeled in a 2-level hierarchical model using generalized linear mixed effects to allow for clustering by different centers.

RESULTS

From 2001 to 2009, the case-fatality rate decreased from 22% to 13% (p < 0.0001), a change that remained significant after adjusting for factors that independently predict mortality (adjusted OR 0.52, 95% CI 0.39-0.70; p < 0.0001). Guidelines adherence increased, with the percentage of patients with ICP monitoring increasing from 56% to 75% (p < 0.0001). Adherence to cerebral perfusion pressure treatment thresholds increased from 15% to 48% (p < 0.0001). The proportion of patients having an ICP elevation greater than 25 mm Hg dropped from 42% to 29% (p = 0.0001).

CONCLUSIONS

There was a significant reduction in TBI mortality between 2001 and 2009 in New York State. Increase in Guidelines adherence occurred at the same time as the pronounced decrease in 2-week mortality and decreased rate of intracranial hypertension, suggesting a causal relationship between Guidelines adherence and improved outcomes. Our findings warrant future investigation to identify methods for increasing and sustaining adherence to evidence-based Guidelines recommendations.

[Increased intracranial pressure and brain edema]

In primary and secondary brain diseases, increasing volumes of the three compartments of brain tissue, cerebrospinal fluid, or blood lead to a critical increase in intracranial pressure (ICP). A rising ICP is associated with typical clinical symptoms; however, during analgosedation it can only be detected by invasive ICP monitoring. Other neuromonitoring procedures are not as effective as ICP monitoring; they reflect the ICP changes and their complications by other metabolic and oxygenation parameters. The most relevant parameter for brain perfusion is cerebral perfusion pressure (CPP), which is calculated as the difference between the middle arterial pressure (MAP) and the ICP. A mixed body of evidence exists for the different ICP-reducing treatment measures, such as hyperventilation, hyperosmolar substances, hypothermia, glucocorticosteroids, CSF drainage, and decompressive surgery.

Perioperative management of traumatic brain injury

Traumatic brain injury (TBI) is a major public health problem and the leading cause of death and disability worldwide. Despite the modern diagnosis and treatment, the prognosis for patients with TBI remains poor. While severity of primary injury is the major factor determining the outcomes, the secondary injury caused by physiological insults such as hypotension, hypoxemia, hypercarbia, hypocarbia, hyperglycemia and hypoglycemia, etc. that develop over time after the onset of the initial injury, causes further damage to brain tissue, worsening the outcome in TBI. Perioperative period may be particularly important in the course of TBI management. While surgery and anesthesia may predispose the patients to new onset secondary injuries which may contribute adversely to outcomes, the perioperative period is also an opportunity to detect and correct the undiagnosed pre-existing secondary insults, to prevent against new secondary insults and is a potential window to initiate interventions that may improve outcome of TBI. For this review, extensive Pubmed and Medline search on various aspects of perioperative management of TBI was performed, followed by review of research focusing on intraoperative and perioperative period. While the research focusing specifically on the intraoperative and immediate perioperative TBI management is limited, clinical management continues to be based largely on physiological optimization and recommendations of Brain Trauma Foundation guidelines. This review is focused on the perioperative management of TBI, with particular emphasis on recent developments.

[Increased intracranial pressure and brain edema]

In primary and secondary brain diseases, increasing volumes of the three compartments of brain tissue, cerebrospinal fluid, or blood lead to a critical increase in intracranial pressure (ICP). A rising ICP is associated with typical clinical symptoms; however, during analgosedation it can only be detected by invasive ICP monitoring. Other neuromonitoring procedures are not as effective as ICP monitoring; they reflect the ICP changes and their complications by other metabolic and oxygenation parameters. The most relevant parameter for brain perfusion is cerebral perfusion pressure (CPP), which is calculated as the difference between the middle arterial pressure (MAP) and the ICP. A mixed body of evidence exists for the different ICP-reducing treatment measures, such as hyperventilation, hyperosmolar substances, hypothermia, glucocorticosteroids, CSF drainage, and decompressive surgery.

Emergency neurological life support: intracranial hypertension and herniation

Sustained intracranial hypertension and acute brain herniation are "brain codes," signifying catastrophic neurological events that require immediate recognition and treatment to prevent irreversible injury and death. As in cardiac arrest, evidence supports the organized implementation of a stepwise management algorithm. Because there are multiple etiologies and many treatments that can potentially reverse cerebral herniation, intracranial hypertension and herniation was chosen as an Emergency Neurological Life Support (ENLS) protocol.

Dobutamine-induced high cardiac index did not prevent vasospasm in subarachnoid hemorrhage patients: a randomized controlled pilot study

BACKGROUND

Prevention of vasospasm is a challenging issue in subarachnoid hemorrhage (SAH) patients and the objective is to compare high dobutamine-induced cardiac index (CI) and high norepinephrine-induced hypertension for the prevention of vasospasm in SAH patients.

METHODS

Single center, single blind, controlled randomized study. Patients hospitalized in intensive care unit (ICU) for a moderate to severe SAH (WFNS grade ≥2) were randomized to receive dobutamine to reach a 25 % increase in cardiac index or norepinephrine to reach a mean arterial pressure ≥100 mmHg. Norepinephrine could be used in the dobutamine group to maintain a cerebral pressure perfusion ≥60 mmHg. Primary endpoint was the incidence of angiographic vasospasm in the first 14 days in the ICU setting, which was upheld by a cerebral arteriography. Secondary endpoints were the incidence of delayed ischemic deficits, duration of mechanical ventilation, and ICU length of stay (LOS).

RESULTS

During the 3-year study, 41 patients were randomized. Six patients were excluded--3 because of consent withdrawal and 3 who did not receive the assigned treatment. Respectively, 17 and 18 patients in the dobutamine and the norepinephrine group were kept in analysis. Five (28 %) patients in the dobutamine group and 5 (27 %) patients in the norepinephrine group developed vasospasm in ICU (p = 1). Seven (41 %) patients presented a delayed ischemic deficit in the dobutamine group and 9 (50 %) in the norepinephrine group (p = 0.24). Duration of mechanical ventilation was 8 [0.5-11.5] days in the dobutamine group and 19 [2.7-23] days in the norepinephrine group (p = 0.01). ICU LOS was 11 [6-15] days in the dobutamine group and 21 [9-28] days in the norepinephrine group (p = 0.01).

CONCLUSION

As compared to norepinephrine-induced hypertension, dobutamine-induced high CI did not reduce the rate of vasospasm in SAH patients. Dobutamine may reduce durations of mechanical ventilation and ICU LOS.

Decompressive craniectomy and head injury: brain morphometry, ICP, cerebral hemodynamics, cerebral microvascular reactivity, and neurochemistry

There has been renewed interest in decompressive craniectomy as a surgical treatment for elevated intracranial pressure (ICP), although evidence-based clinical data are still lacking and some experimental results are conflicting. Ongoing clinical trials on the use of this operation after traumatic brain injury (TBI) may clarify the clinical application of this technique, however, some pathophysiological issues, such as the timing of this operation, its effect on brain edema formation, and its role for secondary brain damage, are still controversial. This review addresses recent clinical data on the influence of decompressive craniectomy on the brain pathophysiology in TBI. Decompressive craniectomy with dural augmentation enlarges intracranial space so that the swollen cerebral hemisphere could expand out of normal cranial limits, avoiding progression of brain herniation. The gain in intracranial volume results in both the improvement of cerebral compliance and a decrease in ICP; the latter favors a rise in both cerebral blood flow and cerebral microvascular perfusion, which can be accompanied by elevation in brain tissue oxygen tension (PbtO2) as well as the return of abnormal metabolic parameters to normal values in cases of cerebral ischemia. Enhancement of edema formation, impairment of cerebrovascular pressure reactivity, and non-restoration of brain aerobic metabolism due to metabolic crisis may occur after craniectomy and require further investigations. This review suggests that decompressive craniectomy as the sole treatment is likely to be insufficient; efforts must be made to maintain adequate brain hemodynamics, preferably coupled with brain metabolism, in addition to treating brain metabolic abnormalities, during postoperative stages.

The potential utility of blood-derived biochemical markers as indicators of early clinical trends following severe traumatic brain injury

OBJECTIVE

Severe traumatic brain injury (TBI) is a dynamic neuropathologic process in which a substantial proportion of patients die within the first 48-hours. The assessment of injury severity and prognosis are of primary concern in the initial management of severe TBI. Supplemental testing that aids in the stratification of patients at high risk for deterioration may significantly improve posttraumatic management in the acute setting.

METHODS

This retrospective study assessed the utility of both single-marker and multimarker models as predictive indicators of acute clinical status after severe TBI. Forty-four patients who sustained severe TBI (admission Glasgow Coma Scale [GCS] score ≤ 8) were divided into two cohorts according to a dichotomized clinical outcome at 72 hours after admission: Poor status (death or GCS score ≤ 8) and improved status (GCS score improved to >8). Threshold values for clinical status prediction were calculated for serum S-100B, matrix metalloproteinase-9, and plasma D-dimer, upon admission and at 24 hours after TBI by the use of receiver operating characteristic analysis. Performance characteristics of these single-marker predictors were compared with those derived from a multimarker logistic regression analysis.

RESULTS

Biomarkers with the greatest predictive value for poor status at 72 hours included serum S-100B on admission, as well as plasma D-dimer and serum S-100B at 24 hours, for which, associations were strongly significant. Multimarker analysis indicated no substantial improvement in prediction accuracy over the best single predictors during this time frame.

CONCLUSION

In conjunction with other clinical, physical, and radiologic evidence, blood-derived biochemical markers may serve to enhance prediction of early clinical trends after severe TBI.

Brain tissue oxygen monitoring after severe traumatic brain injury in children: relationship to outcome and association with other clinical parameters

OBJECT

Minimizing secondary brain injuries after traumatic brain injury (TBI) in children is critical to maximizing neurological outcome. Brain tissue oxygenation monitoring (as measured by interstitial partial pressure of O2 [PbO2]) is a new tool that may aid in guiding therapies, yet experience in children is limited. This study aims to describe the authors' experience of PbO2 monitoring after TBI. It was hypothesized that PbO2 thresholds could be established that were associated with favorable neurological outcome, and it was determined whether any relationships between PbO2 and other important clinical variables existed.

METHODS

Forty-six children with severe TBI (Glasgow coma scale score ≤ 8 after resuscitation) who underwent PbO2 and brain temperature monitoring between September 2004 and June 2008 were studied. All patients received standard neurocritical care, and 24 were concurrently enrolled in a trial of therapeutic early hypothermia (n = 12/group). The PbO2 was measured in the uninjured frontal cortex. Hourly recordings and calculated daily means of various variables including PbO2, intracranial pressure (ICP), cerebral perfusion pressure (CPP), mean arterial blood pressure, partial pressure of arterial O2, and fraction of inspired O2 were compared using several statistical approaches. Glasgow outcome scale scores were determined at 6 months after injury.

RESULTS

The mean patient age was 9.4 years (range 0.1-16.5 years; 13 girls) and 8554 hours of monitoring were analyzed (PbO2 range 0.0-97.2 mm Hg). A PbO2 of 30 mm Hg was associated with the highest sensitivity/specificity for favorable neurological outcome at 6 months after TBI, yet CPP was the only factor that was independently associated with favorable outcome. Surprisingly, instances of preserved PbO2 with altered ICP and CPP were observed in some children with unfavorable outcomes.

CONCLUSIONS

Monitoring of PbO2 demonstrated complex interactions with clinical variables reflecting intracranial dynamics using this protocol. A higher threshold than reported in studies in adults was suggested as a potential therapeutic target, but this threshold was not associated with improved outcomes. Additional studies to assess the utility of PbO2 monitoring after TBI in children are needed.

Variability of ICU use in adult patients with minor traumatic intracranial hemorrhage

STUDY OBJECTIVE

Patients with minor traumatic intracranial hemorrhage are frequently admitted to the ICU, although many never require critical care interventions. To describe ICU resource use in minor traumatic intracranial hemorrhage, we assess (1) the variability of ICU use in a cohort of patients with minor traumatic intracranial hemorrhage across multiple trauma centers, and (2) the proportion of adult patients with traumatic intracranial hemorrhage who are admitted to the ICU and never receive a critical care intervention during hospitalization. In addition, we evaluate the association between ICU admission and key independent variables.

METHODS

A structured, historical cohort study of adult patients (aged 18 years and older) with minor traumatic intracranial hemorrhage was conducted within a consortium of 8 Level I trauma centers in the western United States from January 2005 to June 2010. The study population included patients with minor traumatic intracranial hemorrhage, defined as an emergency department (ED) Glasgow Coma Scale (GCS) score of 15 (normal mental status) and an Injury Severity Score less than 16 (no other major organ injury). The primary outcome measure was initial ICU admission. The secondary outcome measure was a critical care intervention during hospitalization. Critical care interventions included mechanical ventilation, neurosurgical intervention, transfusion of blood products, vasopressor or inotrope administration, and invasive hemodynamic monitoring. ED disposition and the proportion of ICU patients not receiving a critical care intervention were compared across sites with descriptive statistics. The association between ICU admission and predetermined independent variables was analyzed with multivariable regression.

RESULTS

Among 11,240 adult patients with traumatic intracranial hemorrhage, 1,412 (13%) had minor traumatic intracranial hemorrhage and complete ED disposition data (mean age 48 years; SD 20 years). ICU use within this cohort across sites ranged from 50% to 97%. Overall, 847 of 888 patients (95%) with minor traumatic intracranial hemorrhage who were admitted to the ICU did not receive a critical care intervention during hospitalization (range between sites 80% to 100%). Three of 524 (0.6%) patients discharged home or admitted to the observation unit or ward received a critical care intervention. After controlling for severity of injury (age, blood pressure, and Injury Severity Score), study site was independently associated with ICU admission (odds ratios ranged from 1.5 to 30; overall effect P<.001).

CONCLUSION

Across a consortium of trauma centers in the western United States, there was wide variability in ICU use within a cohort of patients with minor traumatic intracranial hemorrhage. Moreover, a large proportion of patients admitted to the ICU never required a critical care intervention, indicating the potential to improve use of critical care resources in patients with minor traumatic intracranial hemorrhage.

The first 72 hours of brain tissue oxygenation predicts patient survival with traumatic brain injury

BACKGROUND

Utilization of brain tissue oxygenation (pBtO(2)) is an important but controversial variable in the treatment of traumatic brain injury. We hypothesize that pBtO(2) values over the first 72 hours of monitoring are predictive of mortality.

METHODS

Consecutive, adult patients with severe traumatic brain injury and pBtO(2) monitors were retrospectively identified. Time-indexed measurements of pBtO(2), cerebral perfusion pressure (CPP), and intracranial pressure (ICP) were collected, and average values over 4-hour blocks were determined. Patients were stratified according to survival, and repeated measures analysis of variance was used to compare pBtO(2), CPP, and ICP. The pBtO(2) threshold most predictive for survival was determined.

RESULTS

There were 8,759 time-indexed data points in 32 patients. The mean age was 39 years ± 16.5 years, injury severity score was 27.7 ± 10.7, and Glasgow Coma Scale score was 6.6 ± 3.4. Survival was 68%. Survivors consistently demonstrated higher pBtO(2) values compared with nonsurvivors including age as a covariate (F = 12.898, p < 0.001). Individual pBtO(2) was higher at the time points 8 hours, 12 hours, 20 hours to 44 hours, 52 hours to 60 hours, and 72 hours of monitoring (p < 0.05). There was no difference in ICP (F = 1.690, p = 0.204) and CPP (F = 0.764, p = 0.389) values between survivors and nonsurvivors including age as a covariate. Classification and regression tree analysis identified 29 mm Hg as the threshold at which pBtO(2) was most predictive for mortality.

CONCLUSION

The first 72 hours of pBtO(2) neurologic monitoring predicts mortality. When the pBtO(2) monitor remains below 29 mm Hg in the first 72 hours of monitoring, mortality is increased. This study challenges the brain oxygenation threshold of 20 mm Hg that has been used conventionally and delineates a time for monitoring pBtO(2) that is predictive of outcome.

LEVEL OF EVIDENCE

III, prognostic study.

Brain hypoxia is associated with short-term outcome after severe traumatic brain injury independently of intracranial hypertension and low cerebral perfusion pressure

BACKGROUND

Brain hypoxia (BH) can aggravate outcome after severe traumatic brain injury (TBI). Whether BH or reduced brain oxygen (Pbto(2)) is an independent outcome predictor or a marker of disease severity is not fully elucidated.

OBJECTIVE

To analyze the relationship between Pbto(2), intracranial pressure (ICP), and cerebral perfusion pressure (CPP) and to examine whether BH correlates with worse outcome independently of ICP and CPP.

METHODS

We studied 103 patients monitored with ICP and Pbto(2) for > 24 hours. Durations of BH (Pbto(2) < 15 mm Hg), ICP > 20 mm Hg, and CPP < 60 mm Hg were calculated with linear interpolation, and their associations with outcome within 30 days were analyzed.

RESULTS

Duration of BH was longer in patients with unfavorable (Glasgow Outcome Scale score, 1-3) than in those with favorable (Glasgow Outcome Scale, 4-5) outcome (8.3 ± 15.9 vs 1.7 ± 3.7 hours; P < .01). In patients with intracranial hypertension, those with BH had fewer favorable outcomes (46%) than those without (81%; P < .01); similarly, patients with low CPP and BH were less likely to have favorable outcome than those with low CPP but normal Pbto(2) (39% vs 83%; P < .01). After ICP, CPP, age, Glasgow Coma Scale score, Marshall computed tomography grade, and Acute Physiology and Chronic Health Evaluation II score were controlled for, BH was independently associated with poor prognosis (adjusted odds ratio for favorable outcome, 0.89 per hour of BH; 95% confidence interval, 0.79-0.99; P = .04).

CONCLUSION

Brain hypoxia is associated with poor short-term outcome after severe traumatic brain injury independently of elevated ICP, low CPP, and injury severity. Pbto(2) may be an important therapeutic target after severe traumatic brain injury.

Traumatic brain injury in pediatric patients: evidence for the effectiveness of decompressive surgery

Traumatic brain injury (TBI) is the current leading cause of death in children over 1 year of age. Adequate management and care of pediatric patients is critical to ensure the best functional outcome in this population. In their controversial trial, Cooper et al. concluded that decompressive craniectomy following TBI did not improve clinical outcome of the analyzed adult population. While the study did not target pediatric populations, the results do raise important and timely clinical questions regarding the effectiveness of decompressive surgery in pediatric patients. There is still a paucity of evidence regarding the effectiveness of this therapy in a pediatric population, and there is an especially noticeable knowledge gap surrounding age-stratified interventions in pediatric trauma. The purposes of this review are to first explore the anatomical variations between pediatric and adult populations in the setting of TBI. Second, the authors assess how these differences between adult and pediatric populations could translate into differences in the impact of decompressive surgery following TBI.

Mortality and long-term functional outcome associated with intracranial pressure after traumatic brain injury

PURPOSE

Elevated intracranial pressure (ICP) has been associated with increased mortality in patients with severe traumatic brain injury (TBI). We have examined whether raised ICP is independently associated with mortality, functional status and neuropsychological functioning in adult TBI patients.

METHODS

Data from a randomized trial of 499 participants were secondarily analyzed. The primary endpoints were mortality and a composite measure of functional status and neuropsychological function (memory, speed of information processing, executive function) over a 6-month period. The area under the curve of the ICP profile (average ICP) during the first 48 h of monitoring was the main predictor of interest. Multivariable regression was used to adjust for a priori defined confounders: age, Glasgow Coma Score, Abbreviated Injury Scale-head and hypoxia.

RESULTS

Of the participants, 365 patients had complete 48-h ICP data. The overall 6-month mortality was 18 %. The adjusted odds ratio of mortality comparing 10-mmHg increases in average ICP was 3.12 (95 % confidence interval 1.79, 5.44; p < 0.01). Overall, higher average ICP was associated with decreased functional status and neuropsychological functioning (p < 0.01). Importantly, among survivors, increasing average ICP was not independently associated with worse performance on neuropsychological testing (p = 0.46).

CONCLUSIONS

Average ICP in the first 48 h of monitoring was an independent predictor of mortality and of a composite endpoint of functional and neuropsychological outcome at the 6-month follow-up in moderate or severe TBI patients. However, there was no association between average ICP and neuropsychological functioning among survivors.

Early induction of hypothermia for evacuated intracranial hematomas: a post hoc analysis of two clinical trials

OBJECT

The authors hypothesized that cooling before evacuation of traumatic intracranial hematomas protects the brain from reperfusion injury and, if so, further hypothesized that hypothermia induction before or soon after craniotomy should be associated with improved outcomes.

METHODS

The National Acute Brain Injury Study: Hypothermia I (NABIS:H I) was a randomized multicenter clinical trial of 392 patients with severe brain injury treated using normothermia or hypothermia for 48 hours with patients reaching 33°C at 8.4 ± 3 hours after injury. The National Acute Brain Injury Study: Hypothermia II (NABIS:H II) was a randomized, multicenter clinical trial of 97 patients with severe brain injury treated with normothermia or hypothermia for 48 hours with patients reaching 35°C within 2.6 ± 1.2 hours and 33°C within 4.4 ± 1.5 hours of injury. Entry and exclusion criteria, management, and outcome measures in the 2 trials were similar.

RESULTS

In NABIS:H II among the patients with evacuated intracranial hematomas, outcome was poor (severe disability, vegetative state, or death) in 5 of 15 patients in the hypothermia group and in 9 of 13 patients in the normothermia group (relative risk 0.44, 95% CI 0.22-0.88; p = 0.02). All patients randomized to hypothermia reached 35°C within 1.5 hours after surgery start and 33°C within 5.55 hours. Applying these criteria to NABIS:H I, 31 of 54 hypothermia-treated patients reached a temperature of 35°C or lower within 1.5 hours after surgery start time, and the remaining 23 patients reached 35°C at later time points. Outcome was poor in 14 (45%) of 31 patients reaching 35°C within 1.5 hours of surgery, in 14 (61%) of 23 patients reaching 35°C more than 1.5 hours of surgery, and in 35 (60%) of 58 patients in the normothermia group (relative risk 0.74, 95%, CI 0.49-1.13; p = 0.16). A meta-analysis of 46 patients with hematomas in both trials who reached 35°C within 1.5 hours of surgery start showed a significantly reduced rate of poor outcomes (41%) compared with 94 patients treated with hypothermia who did not reach 35°C within that time and patients treated at normothermia (62%, p = 0.009).

CONCLUSIONS

Induction of hypothermia to 35°C before or soon after craniotomy with maintenance at 33°C for 48 hours thereafter may improve outcome of patients with hematomas and severe traumatic brain injury. Clinical trial registration no.: NCT00178711.

Decompressive Craniectomy in Acute Brain Injury – Lifting the lid on Neurosurgical Practice

Decompressive craniectomy (DC) is an effective method of controlling rising intracranial pressure (ICP) refractory to medical treatment in a range of conditions: traumatic brain injury in both adults and children, malignant middle cerebral artery infarction and following subarachnoid haemorrhage. Herein, we describe its indications, prognosis, current operative methods and postoperative management.

Perioperative management of adult traumatic brain injury

This article presents an overview of the management of traumatic brain injury (TBI) as relevant to the practicing anesthesiologist. Key concepts surrounding the pathophysiology and anesthetic principles are used to describe potential ways to reduce secondary insults and improve outcomes after TBI.

Intracranial Pressure Monitoring: Invasive versus Non-Invasive Methods-A Review

Monitoring of intracranial pressure (ICP) has been used for decades in the fields of neurosurgery and neurology. There are multiple techniques: invasive as well as noninvasive. This paper aims to provide an overview of the advantages and disadvantages of the most common and well-known methods as well as assess whether noninvasive techniques (transcranial Doppler, tympanic membrane displacement, optic nerve sheath diameter, CT scan/MRI and fundoscopy) can be used as reliable alternatives to the invasive techniques (ventriculostomy and microtransducers). Ventriculostomy is considered the gold standard in terms of accurate measurement of pressure, although microtransducers generally are just as accurate. Both invasive techniques are associated with a minor risk of complications such as hemorrhage and infection. Furthermore, zero drift is a problem with selected microtransducers. The non-invasive techniques are without the invasive methods' risk of complication, but fail to measure ICP accurately enough to be used as routine alternatives to invasive measurement. We conclude that invasive measurement is currently the only option for accurate measurement of ICP.

High-frequency oscillation as a rescue strategy for brain-injured adult patients with acute lung injury and acute respiratory distress syndrome

Acute lung injury and acute respiratory distress syndrome (ARDS) occur frequently in brain-injured patients. Single organ dysfunction ventilator strategies result in a conflict between lung protective ventilation and the prevention of secondary neurological insult(s). The objectives of this study were to determine if clinical and physiological benefits of high-frequency oscillatory ventilation (HFOV) exist compared to conventional ventilation and to determine what data there are on the effects of HFOV on cerebral perfusion pressure and intracranial pressure. Systematic review was designed. An optimally sensitive search strategy was used that included; OVID MEDLINE, OVID EMBASE, Cochrane Clinical Trials Register, and hand searching of references of retrieved articles and proceedings of meetings. Study selection includes published randomized controlled trials comparing HFOV with conventional ventilation in adults with ARDS and observational studies of the use of HFOV in adults with ARDS and traumatic brain injury (TBI). Both authors reviewed all trials. A data extraction form was used. In adults with ARDS no mortality benefit has been shown with HFOV, oxygenation improves, arterial partial pressure of CO(2) may increase and there is no change in mean arterial blood pressure. There are few data describing HFOV in adults with TBI. In the small, low quality, studies that have been reported there have not been uncontrollable changes in intracranial pressure. HFOV has not been shown to have any mortality benefit in adults with ARDS. There are insufficient data to clarify the role, or safety, of HFOV in adults with TBI and concurrent ARDS.

Pulsatile intracranial pressure and cerebral autoregulation after traumatic brain injury

BACKGROUND

Strong correlation between mean intracranial pressure (ICP) and its pulse wave amplitude (AMP) has been demonstrated in different clinical scenarios. We investigated the relationship between invasive mean arterial blood pressure (ABP) and AMP to explore its potential role as a descriptor of cerebrovascular pressure reactivity after traumatic brain injury (TBI).

METHODS

We retrospectively analyzed data of patients suffering from TBI with brain monitoring. Transcranial Doppler blood flow velocity, ABP, ICP were recorded digitally. Cerebral perfusion pressure (CPP) and AMP were derived. A new index-pressure-amplitude index (PAx)-was calculated as the Pearson correlation between (averaged over 10 s intervals) ABP and AMP with a 5 min long moving average window. The previously introduced transcranial Doppler-based autoregulation index Mx was evaluated in a similar way, as the moving correlation between blood flow velocity and CPP. The clinical outcome was assessed after 6 months using the Glasgow outcome score.

RESULTS

293 patients were studied. The mean PAx was -0.09 (standard deviation 0.21). This negative value indicates that, on average, an increase in ABP causes a decrease in AMP and vice versa. PAx correlated strong with Mx (R (2) = 0.46, P < 0.0002). PAx also correlated with age (R (2) = 0.18, P < 0.05). PAx was found to have as good predictive outcome value (area under curve 0.71, P < 0.001) as Mx (area under curve 0.69, P < 0.001).

CONCLUSIONS

We demonstrated significant correlation between the known cerebral autoregulation index Mx and PAx. This new index of cerebrovascular pressure reactivity using ICP pulse wave information showed to have a strong association with outcome in TBI patients.

Bench-to-bedside and bedside back to the bench; coordinating clinical and experimental traumatic brain injury studies

Traumatic brain injury (TBI) is one of the leading cause of death and long-term disability in virtually every country. Advances in neurointensive care have resulted in steadily decreasing morbidity, but the number of individuals with severe long-term disability have not changed significantly and the number of moderate disability has shown steady increase over the last 3 decades. Despite years of intensive preclinical research – and millions spent – there are virtually no drugs specifically developed to mitigate the consequences of TBI. Here we discuss some of the existing gaps between clinical and experimental TBI studies that may have contributed to the current status. We do this hoping that clinical, basic, and translational scientists will design and coordinate studies in order to achieve maximum benefits for TBI patients. In conclusion, we suggest to: (1) Develop consensus-based guidelines for experimental TBI research, similar to “best practices” in the clinic; (2) Generate a consensus-based template for clinical data collection and deposition as well as for experimental TBI data collection and deposition; (3) Use a systems biology approach and create a database for integrating existing data from basic and clinical research.

US estimates of hospitalized children with severe traumatic brain injury: implications for clinical trials

OBJECTIVES

To estimate sample sizes available for clinical trials of severe traumatic brain injury (TBI) in children, we described the patient demographics and hospital characteristics associated with children hospitalized with severe TBI in the United States.

METHODS

We analyzed the 2006 Kids' Inpatient Database. Severe TBI hospitalizations were defined as children discharged with TBI who required mechanical ventilation or intubation. Types of high-volume severe TBI hospitals were categorized based on the numbers of discharged patients with severe TBI in 2006. National estimates of demographics and hospital characteristics were calculated for pediatric severe TBI. Simulation analyses were performed to assess the potential number of severe TBI cases from randomly selected hospitals for inclusion in future clinical trials.

RESULTS

The majority of children with severe TBI were discharged from either a children's unit in general hospitals (41%) or a nonchildren's hospital (34%). Less than 5% of all hospitals were high-volume TBI hospitals, which discharged >78% of severe TBI cases and were more likely to be a children's unit in a general hospital or a children's hospital. Simulation analyses indicate that there is a saturation point after which the benefit of adding additional recruitment sites decreases significantly.

CONCLUSIONS

Children with severe TBI are infrequent at any one hospital in the United States, and few hospitals treat large numbers of children with severe TBI. To effectively plan trials of therapies for severe TBI, much attention has to be paid to selecting the right types of centers to maximize enrollment efficiency.

Biomarkers in neurocritical care

The gold standard for assessing neurological function is the bedside clinical examination. However, in neurocritical patients, the signs and symptoms related to the severity of illness can often be ambiguous. It can be hard to distinguish between a severe but stable disease state and one that is dynamic and in a critical decline. Clinicians and family members alike may struggle with the uncertainty of functional outcome prediction. Intermediate biomarkers of brain injury can assist with ongoing clinical management of patients, and in some circumstances can guide prognosis. Used in the right setting, biomarkers in neurocritical care can also aid with decisions to intensify treatment or avoid prolonged and unnecessary therapy. The term biomarker is used in various ways, and here we use it to refer to 3 general types: 1) circulating blood macromolecules, 2) brain imaging, and 3) continuous invasive monitors. Despite its promise, biomarkers have several limitations and should be interpreted in the context of the overall clinical assessment.

Effect of osmotic agents on regional cerebral blood flow in traumatic brain injury

PURPOSE

Cerebral blood flow (CBF) is reduced after severe traumatic brain injury (TBI) with considerable regional variation. Osmotic agents are used to reduce elevated intracranial pressure (ICP), improve cerebral perfusion pressure, and presumably improve CBF. Yet, osmotic agents have other physiologic effects that can influence CBF. We sought to determine the regional effect of osmotic agents on CBF when administered to treat intracranial hypertension.

MATERIALS AND METHODS

In 8 patients with acute TBI, we measured regional CBF with positron emission tomography before and 1 hour after administration of equi-osmolar 20% mannitol (1 g/kg) or 23.4% hypertonic saline (0.686 mL/kg) in regions with focal injury and baseline hypoperfusion (CBF <25 mL per 100 g/min).

RESULTS

The ICP fell (22.4 ± 5.1 to 15.7 ± 7.2 mm Hg, P = .007), and cerebral perfusion pressure rose (75.7 ± 5.9 to 81.9 ± 10.3 mm Hg, P = .03). Global CBF tended to rise (30.9 ± 3.7 to 33.1 ± 4.2 mL per 100 g/min, P = .07). In regions with focal injury, baseline flow was 25.7 ± 9.1 mL per 100 g/min and was unchanged; in hypoperfused regions (15% of regions), flow rose from 18.6 ± 5.0 to 22.4 ± 6.4 mL per 100 g/min (P < .001). Osmotic therapy reduced the number of hypoperfused brain regions by 40% (P < .001).

CONCLUSION

Osmotic agents, in addition to lowering ICP, improve CBF to hypoperfused brain regions in patients with intracranial hypertension after TBI.

Intracranial pressure: why we monitor it, how to monitor it, what to do with the number and what's the future?

PURPOSE OF REVIEW

The review touches upon the current physiopathological concepts relating to the field of intracranial pressure (ICP) monitoring and offers an up-to-date overview of the ICP monitoring technologies and of the signal-analysis techniques relevant to clinical practice.

RECENT FINDINGS

Improved ICP probes, antibiotic-impregnated ventricular catheters and multimodality, computerized systems allow ICP monitoring and individualized optimization of brain physiology. Noninvasive technologies for ICP and cerebral perfusion pressure assessment are being tested in the clinical arena. Computerized morphological analysis of the ICP pulse-waveform can provide an indicator of global cerebral perfusion.

SUMMARY

Current recommendations for the management of traumatic brain injury indicate ICP monitoring in patients who remain comatose after resuscitation if the admission computed tomography scan reveals intracranial abnormalities such as haematomas, contusions and cerebral oedema. The most reliable methods of ICP monitoring are ventricular catheters and intraparenchymal systems. A growing number of these devices are being safely placed by neurointensivists. The consensus is to treat ICP exceeding the 20 mmHg threshold, and to target cerebral perfusion pressure between 50 and 70 mmHg. Recent evidence suggests that such thresholds should be optimized based on multimodality monitoring and individual brain physiology. Noninvasive ICP estimation using transcranial Doppler can have a role as a screening tool in patients with low to intermediate risk of developing intracranial hypertension. However, the technology remains insufficiently accurate and too cumbersome for continuous ICP monitoring.

Response to intracranial hypertension treatment as a predictor of death in patients with severe traumatic brain injury

Object

The normalization of increased intracranial pressure (ICP) in patients with severe traumatic brain injury (TBI) is assumed to limit secondary brain injury and improve outcome. Despite evidence-based recommendations for monitoring and treatment of elevated ICP, there are few studies that show an association between response to ICP-directed therapeutic regimens and adjusted mortality rate. This study utilizes a large prospective database to examine the effect of response to ICP-lowering therapy on risk of death within the first 2 weeks of injury in patients who sustained TBI and are older than 16 years.

Methods

The current study is based on 1426 patients with severe TBI (Glasgow Coma Scale [GCS] score < 9) of whom 388 were treated for elevated ICP (> 25 mm Hg) between 2000 and 2008 at 22 trauma centers enrolled in a New York State quality improvement program. This prospectively collected database also contains information including age, admission GCS score, pupillary status, CT scanning parameters, and hypotension, which are all known early prognostic indicators of death. Treatment of elevated ICP consisted of administration of mannitol, hypertonic saline, barbiturates, and/or drainage of CSF or decompressive craniectomy. The factors predicting ICP response to treatment and predicting death at 2 weeks were evaluated using logistic regression analyses.

Results

Increasing age and fewer hours of elevated ICP on Day 1 were found to be significant predictors (p = 0.001 and 0.0003, respectively) of a positive response to treatment. Response to ICP-lowering therapy (p = 0.03), younger age (p < 0.0001), fewer hours of elevated ICP (p < 0.0001), and absence of arterial hypotension on Day 1 (p = 0.001) significantly predicted reduced risk of death.

Conclusions

Patients who responded to ICP-lowering treatment had a 64% lower risk of death at 2 weeks than those who did not respond after adjusting for factors that independently predict risk of death.

Decompressive craniectomy in diffuse traumatic brain injury

BACKGROUND

It is unclear whether decompressive craniectomy improves the functional outcome in patients with severe traumatic brain injury and refractory raised intracranial pressure.

METHODS

From December 2002 through April 2010, we randomly assigned 155 adults with severe diffuse traumatic brain injury and intracranial hypertension that was refractory to first-tier therapies to undergo either bifrontotemporoparietal decompressive craniectomy or standard care. The original primary outcome was an unfavorable outcome (a composite of death, vegetative state, or severe disability), as evaluated on the Extended Glasgow Outcome Scale 6 months after the injury. The final primary outcome was the score on the Extended Glasgow Outcome Scale at 6 months.

RESULTS

Patients in the craniectomy group, as compared with those in the standard-care group, had less time with intracranial pressures above the treatment threshold (P<0.001), fewer interventions for increased intracranial pressure (P<0.02 for all comparisons), and fewer days in the intensive care unit (ICU) (P<0.001). However, patients undergoing craniectomy had worse scores on the Extended Glasgow Outcome Scale than those receiving standard care (odds ratio for a worse score in the craniectomy group, 1.84; 95% confidence interval [CI], 1.05 to 3.24; P=0.03) and a greater risk of an unfavorable outcome (odds ratio, 2.21; 95% CI, 1.14 to 4.26; P=0.02). Rates of death at 6 months were similar in the craniectomy group (19%) and the standard-care group (18%).

CONCLUSIONS

In adults with severe diffuse traumatic brain injury and refractory intracranial hypertension, early bifrontotemporoparietal decompressive craniectomy decreased intracranial pressure and the length of stay in the ICU but was associated with more unfavorable outcomes. (Funded by the National Health and Medical Research Council of Australia and others; DECRA Australian Clinical Trials Registry number, ACTRN012605000009617.).

Multimodal Cerebral Monitoring in Traumatic Brain Injury

Traumatic brain injury presents a significant impact on patients in terms of morbidity and mortality. Pathology is heterogeneous and is often associated with secondary deterioration. This paper reviews both clinical and research modes of monitoring to detect deterioration and compares what is available to the ideal. Intracranial pressure measurement, jugular venous oxygen saturation, microdialysis and cerebral oxygen monitoring are among the variables described and future research-based modalities are explored.

Intracanal pressure in compressive spinal cord injury: reduction with hypothermia

Most cases of human spinal cord injury (SCI) are accompanied by continuing cord compression. Experimentally, compression results in rapid neurological decline over hours, suggesting a rise in intracanal pressure local to the site of injury. The aim of this study was to measure the rise in local intracanal pressure accompanying progressive canal occlusion and to determine the relationship between raised intracanal pressure and neurological outcome. We also aimed to establish whether hypothermia was able to reduce raised intracanal pressure. We demonstrate that, following SCI in F344 rats, local intracanal pressure remains near normal until canal occlusion exceeds 30% of diameter, whereupon a rapid increase in pressure occurs. Intracanal pressure appears to be an important determinant of neurological recovery, with poor long-term behavioural and histological outcomes in animals subject to 8 h of 45% canal occlusion, in which intracanal pressure is significantly elevated. In contrast, good neurological recovery occurs in animals with near normal intracanal pressure (animals undergoing 8 h of 30% canal occlusion or those undergoing immediate decompression). We further demonstrate that hypothermia is an effective therapy to control raised intracanal pressure, rapidly reducing elevated intracanal pressure accompanying critical (45%) canal occlusion to near normal. Overall these data indicate that following SCI only limited canal narrowing is tolerated before local intracanal pressure rapidly rises, inducing a sharp decline in neurological outcome. Raised intracanal pressure can be controlled with hypothermia, which may be a useful therapy to emergently decompress the spinal cord prior to surgical decompression.

In vivo accuracy of two intraparenchymal intracranial pressure monitors

PURPOSE

To evaluate the in vivo accuracy of the new Pressio(®) device for intraparenchymal monitoring of intracranial pressure (ICP) versus the Codman(®) device and intraventricular measurement external ventricular drainage (EVD).

METHODS

Data were collected retrospectively for 30 consecutive patients admitted into a 25-bed neurosurgical intensive care unit of a university hospital between January and December 2009. Patients received both intraventricular and intraparenchymal ICP monitoring with Pressio(®) (n = 15) or Codman(®) (n = 15).

RESULTS

We obtained 3,089 data points from the 30 patients. Mean difference between intraparenchymal and EVD pressure (bias) was -0.6 mmHg, and limits of agreement (1.96 SD of the bias) were -8.1 to 6.9 mmHg with Pressio(®) and 0.3 mmHg with limits of agreement of -6.7 to 7.1 mmHg with Codman(®) (NS). The temporal difference was -0.7 ± 1.6 mmHg/100 h of monitoring with Pressio(®) and 0.1 ± 1.6 mmHg/100 h of monitoring with Codman(®) over the study period (NS).

CONCLUSIONS

Intraparenchymal pressure measured with both transducers approximates intraventricular cerebrospinal fluid pressure with an accuracy of ±7 mmHg.