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Concept: Cerebral perfusion pressure

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Traumatic brain injury (TBI) has long been recognized as the leading cause of traumatic death and disability. Tremendous advances in surgical and intensive care unit management of the primary injury, including maintaining adequate oxygenation, controlling intracranial pressure, and ensuring proper cerebral perfusion pressure, have resulted in reduced mortality. However, the secondary injury phase of TBI is a prolonged pathogenic process characterized by neuroinflammation, excitatory amino acids, free radicals, and ion imbalance. There are no approved therapies to directly address these underlying processes. Here, we present a case that was intentionally treated with substantial amounts of omega-3 fatty acids (n-3FA) to provide the nutritional foundation for the brain to begin the healing process following severe TBI. Recent animal research supports the use of n-3FA, and clinical experience suggests that benefits may be possible from substantially and aggressively adding n-3FA to optimize the nutritional foundation of severe TBI patients and must be in place if the brain is to be given the opportunity to repair itself to the best possible extent. Administration early in the course of treatment, in the emergency department or sooner, has the potential to improve outcomes from this potentially devastating public health problem.

Concepts: Nutrition, Fatty acid, Traumatic brain injury, Intracranial pressure, Omega-3 fatty acid, Neurology, Cerebral perfusion pressure, Neurotrauma

4

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.

Concepts: Regression analysis, Traumatic brain injury, Intracranial pressure, Neurology, Cerebral perfusion pressure, Focal and diffuse brain injury, Neurotrauma, Brain Trauma Foundation

3

Our goal was to perform a systematic review of the literature on the use of ketamine in traumatic brain injury (TBI) and its effects on intracranial pressure (ICP). All articles from MEDLINE, BIOSIS, EMBASE, Global Health, HealthStar, Scopus, Cochrane Library, the International Clinical Trials Registry Platform (inception to November 2013), reference lists of relevant articles, and gray literature were searched. Two reviewers independently identified all manuscripts pertaining to the administration of ketamine in human TBI patients that recorded effects on ICP. Secondary outcomes of effect on cerebral perfusion pressure, mean arterial pressure, patient outcome, and adverse effects were recorded. Two reviewers independently extracted data including population characteristics and treatment characteristics. The strength of evidence was adjudicated using both the Oxford and GRADE methodology. Our search strategy produced a total 371 citations. Seven articles, six manuscripts and one meeting proceeding, were considered for the review with all utilizing ketamine, while documenting ICP in severe TBI patients. All studies were prospective studies. Five and two studies pertained to adults and pediatrics, respectively. Across all studies, of the 101 adult and 55 pediatric patients described, ICP did not increase in any of the studies during ketamine administration. Three studies reported a significant decrease in ICP with ketamine bolus. Cerebral perfusion pressure and mean blood pressure increased in two studies, leading to a decrease in vasopressors in one. No significant adverse events related to ketamine were recorded in any of the studies. Outcome data were poorly documented. There currently exists Oxford level 2b, GRADE C evidence to support that ketamine does not increase ICP in severe TBI patients that are sedated and ventilated, and in fact may lower it in selected cases.

Concepts: Blood, Hypertension, Traumatic brain injury, Blood pressure, Intracranial pressure, Cerebral perfusion pressure, Pulse pressure, Mean arterial pressure

2

Rigid cervical collars are known to increase intracranial pressure (ICP) in severe traumatic brain injury (TBI). Cerebral blood flow might decrease according to the Kellie Monroe doctrine. For this reason, the use of the collar in patients with severe TBI has been abandoned from several trauma protocols in the Netherlands. There is no evidence on the effect of a rigid collar on ICP in patients with mild or moderate TBI or indeed patients with no TBI. As a first step we tested the effect in healthy volunteers with normal ICPs and intact autoregulation of the brain.

Concepts: Brain, Traumatic brain injury, Intracranial pressure, Neurology, Physical trauma, Cerebral perfusion pressure, Cerebral blood flow, Cervical collar

2

Severe cases of traumatic brain injury (TBI) require neurocritical care, the goal being to stabilize hemodynamics and systemic oxygenation to prevent secondary brain injury. It is reported that approximately 45 % of dysoxygenation episodes during critical care have both extracranial and intracranial causes, such as intracranial hypertension and brain edema. For this reason, neurocritical care is incomplete if it only focuses on prevention of increased intracranial pressure (ICP) or decreased cerebral perfusion pressure (CPP). Arterial hypotension is a major risk factor for secondary brain injury, but hypertension with a loss of autoregulation response or excess hyperventilation to reduce ICP can also result in a critical condition in the brain and is associated with a poor outcome after TBI. Moreover, brain injury itself stimulates systemic inflammation, leading to increased permeability of the blood-brain barrier, exacerbated by secondary brain injury and resulting in increased ICP. Indeed, systemic inflammatory response syndrome after TBI reflects the extent of tissue damage at onset and predicts further tissue disruption, producing a worsening clinical condition and ultimately a poor outcome. Elevation of blood catecholamine levels after severe brain damage has been reported to contribute to the regulation of the cytokine network, but this phenomenon is a systemic protective response against systemic insults. Catecholamines are directly involved in the regulation of cytokines, and elevated levels appear to influence the immune system during stress. Medical complications are the leading cause of late morbidity and mortality in many types of brain damage. Neurocritical care after severe TBI has therefore been refined to focus not only on secondary brain injury but also on systemic organ damage after excitation of sympathetic nerves following a stress reaction.

Concepts: Immune system, Inflammation, Traumatic brain injury, Intracranial pressure, Neurology, Cerebrospinal fluid, Cerebral perfusion pressure, Neurotrauma

2

To investigate arterial spin-labelling (ASL) cerebral blood flow (CBF) changes in predementia stages of Alzheimer’s disease (AD).

Concepts: Alzheimer's disease, Blood, Neurology, Hematology, Artery, Apathy, Cerebral perfusion pressure, Cerebral blood flow

2

Widely varying published and presented analyses of the BEST TRIP randomized controlled trial of intracranial pressure (ICP) monitoring have suggested denying trial generalizability, questioning the need for ICP monitoring in severe traumatic brain injury (sTBI), re-assessing current clinical approaches to monitored ICP, and initiating a general ICP-monitoring moratorium. In response to this dissonance, 23 clinically-active, international opinion leaders in acute-care sTBI management met to draft a consensus statement to interpret this study. A Delphi-method-based approach employed iterative pre-meeting polling to codify the groups general opinions, followed by an in-person meeting wherein individual statements were refined. Statements required an agreement threshold of > 70% by blinded voting for approval. Seven precisely-worded statements resulted, with agreement levels of 83-100%. These statements, which should be read in toto to properly reflect the group’s consensus positions, conclude that this study: 1) studied protocols, not ICP-monitoring per se; 2) applies only to those protocols and specific study groups and should not be generalized to other treatment approaches or patient groups; 3) strongly calls for further research on ICP interpretation and use; 4) should be applied cautiously to regions with much different treatment milieu; 5) did not investigate the utility of treating monitored ICP in the specific patient group with established intracranial hypertension; 6) should not change the practice of those currently monitoring ICP; and 7) provided a protocol, used in non-monitored study patients, that should be considered when treating without ICP monitoring. Consideration of these statements can clarify study interpretation and avoid “collateral damage”.

Concepts: Randomized controlled trial, Traumatic brain injury, Intracranial pressure, Brain tumor, Intracranial hemorrhage, Cerebral perfusion pressure, Brain herniation, Decompressive craniectomy

2

Traumatic brain injury (TBI) is a significant cause of disability and death and a huge economic burden throughout the world. Much of the morbidity associated with TBI is attributed to secondary brain injuries resulting in hypoxia and ischemia after the initial trauma. Intracranial hypertension and decreased partial brain oxygen tension (PbtO2) are targeted as potentially avoidable causes of morbidity. Therapeutic hypothermia (TH) may be an effective intervention to reduce intracranial pressure (ICP), but could also affect cerebral blood flow (CBF). This is a retrospective analysis of prospectively collected data from 17 patients admitted to the Western General Hospital, Edinburgh. Patients with an ICP >20 mmHg refractory to initial therapy were randomized to standard care or standard care and TH (intervention group) titrated between 32°C and 35°C to reduce ICP. ICP and PbtO2 were measured using the Licox system and core temperature was recorded through rectal thermometer. Data were analyzed at the hour before cooling, the first hour at target temperature, 2 consecutive hours at target temperature, and after 6 hours of hypothermia. There was a mean decrease in ICP of 4.3±1.6 mmHg (p<0.04) from 15.7 to 11.4 mmHg, from precooling to the first epoch of hypothermia in the intervention group (n=9) that was not seen in the control group (n=8). A decrease in ICP was maintained throughout all time periods. There was a mean decrease in PbtO2 of 7.8±3.1 mmHg (p<0.05) from 30.2 to 22.4 mmHg, from precooling to stable hypothermia, which was not seen in the control group. This research supports others in demonstrating a decrease in ICP with temperature, which could facilitate a reduction in the use of hyperosmolar agents or other stage II interventions. The decrease in PbtO2 is not below the suggested treatment threshold of 20 mmHg, but might indicate a decrease in CBF.

Concepts: Oxygen, Traumatic brain injury, Intracranial pressure, Brain tumor, Hypoxia, Cerebral perfusion pressure, Focal and diffuse brain injury, Cerebral blood flow

1

In severe traumatic brain injury, cerebral perfusion pressure management based on cerebrovascular pressure reactivity index has the potential to provide a personalized treatment target to improve patient outcomes. So far, the methods have focused on identifying “one” autoregulation-guided cerebral perfusion pressure target-called “cerebral perfusion pressure optimal”. We investigated whether a cerebral perfusion pressure autoregulation range-which uses a continuous estimation of the “lower” and “upper” cerebral perfusion pressure limits of cerebrovascular pressure autoregulation (assessed with pressure reactivity index)-has prognostic value.

Concepts: Mathematics, Medical terms, Physiology, Traumatic brain injury, Intracranial pressure, Cerebral perfusion pressure, Cerebral blood flow, Neurotrauma

1

After traumatic brain injury (TBI), the ability of cerebral vessels to appropriately react to changes in arterial blood pressure (pressure reactivity) is impaired, leaving patients vulnerable to cerebral hypo- or hyperperfusion. Although, the traditional pressure reactivity index (PRx) has demonstrated that impaired pressure reactivity is associated with poor patient outcome, PRx is sometimes erratic and may not be reliable in various clinical circumstances. Here, we introduce a more robust transform-based wavelet pressure reactivity index (wPRx) and compare its performance with the widely used traditional PRx across 3 areas: its stability and reliability in time, its ability to give an optimal cerebral perfusion pressure (CPPopt) recommendation, and its relationship with patient outcome.

Concepts: Blood, Medical terms, Traumatic brain injury, Blood pressure, Intracranial pressure, Artery, Vein, Cerebral perfusion pressure