Cerebral blood flow and metabolism in children with severe head injury. Part 1: Relation to age, Glasgow coma score, outcome, intracranial pressure, and time after injury

Cerebral Blood Flow Measurement in Healthy Children and Children Suffering Severe Traumatic Brain Injury-What Do We Know?

Traumatic brain injury is the leading cause of death in children. Children with severe TBI are in need of neurointensive care where the goal is to prevent secondary brain injury by avoiding secondary insults. Monitoring of cerebral blood flow (CBF) and autoregulation in the injured brain is crucial. However, there are limited studies performed in children to investigate this. Current studies report on age dependent increase in CBF with narrow age range. Low initial CBF following TBI has been correlated to poor outcome and may be more prevalent than hyperemia as previously suggested. Impaired cerebral pressure autoregulation is also detected and correlated with poor outcome but it remains to be elucidated if there is a causal relationship. Current studies are few and mainly based on small number of patients between the age of 0–18 years. Considering the changes of CBF and cerebral pressure autoregulation with increasing age, larger studies with more narrow age ranges and multimodality monitoring are required in order to generate data that can optimize the therapy and clinical management of children suffering TBI.

Emergency Department Implementation of the Brain Trauma Foundation's Pediatric Severe Brain Injury Guideline Recommendations

The "Guidelines for the Management of Pediatric Severe Traumatic Brain Injury, Third Edition: Update of the Brain Trauma Foundation Guidelines" published in Pediatric Critical Care Medicine in 2019 provides new and updated recommendations applicable to the emergency department management of children with severe traumatic brain injury. Practice-changing takeaways include specific recommendations for administration of 3% hypertonic saline, administration of seizure prophylaxis, and avoiding hyperventilation.

Critical Update on the Third Edition of the Guidelines for Managing Severe Traumatic Brain Injury in Children

BACKGROUND

Severe traumatic brain injury (TBI) is associated with high rates of death and disability. As a result, the revised guidelines for the management of pediatric severe TBI address some of the previous gaps in pediatric TBI evidence and management strategies targeted to promote overall health outcomes.

OBJECTIVES

To provide highlights of the most important updates featured in the third edition of the guidelines for the management of pediatric severe TBI. These highlights can help critical care providers apply the most current and appropriate therapies for children with severe TBI.

METHODS AND RESULTS

After a brief overview of the process behind identifying the evidence to support the third edition guidelines, both relevant and new recommendations from the guidelines are outlined to provide critical care providers with the most current management approaches needed for children with severe TBI. Recommendations for neuroimaging, hyperosmolar therapy, analgesics and sedatives, seizure prophylaxis, ventilation therapies, temperature control/hypothermia, nutrition, and corticosteroids are provided. In addition, the complete guideline document and its accompanying algorithm for recommended therapies are available electronically and are referenced within this article.

CONCLUSIONS

The evidence base for treating pediatric TBI is increasing and provides the basis for high-quality care. This article provides critical care providers with a quick reference to the current evidence when caring for a child with a severe TBI. In addition, it provides direct access links to the comprehensive guideline document and algorithms developed to support critical care providers.

Translational approach towards determining the role of cerebral autoregulation in outcome after traumatic brain injury

Cerebral autoregulation is impaired after traumatic brain injury (TBI), contributing to poor outcome. In the context of the neurovascular unit, cerebral autoregulation contributes to neuronal cell integrity and clinically Glasgow Coma Scale is correlated to intactness of autoregulation after TBI. Cerebral Perfusion Pressure (CPP) is often normalized by use of vasoactive agents to increase mean arterial pressure (MAP) and thereby limit impairment of cerebral autoregulation and neurological deficits. However, current vasoactive agent choice used to elevate MAP to increase CPP after TBI is variable. Vasoactive agents, such as phenylephrine, dopamine, norepinephrine, and epinephrine, clinically have not sufficiently been compared regarding effect on CPP, autoregulation, and survival after TBI. The cerebral effects of these clinically commonly used vasoactive agents are incompletely understood. This review will describe translational studies using a more human like animal model (the pig) of TBI to identify better therapeutic strategies to improve outcome post injury. These studies also investigated the role of age and sex in outcome and mechanism(s) involved in improvement of outcome in the setting of TBI. Additionally, this review considers use of inhaled nitric oxide as a novel neuroprotective strategy in treatment of TBI.

Relationships between cerebral flow velocities and neurodevelopmental outcomes in children with moderate to severe traumatic brain injury

PURPOSE

This study aimed to determine relationships between cerebral blood flow and neurodevelopmental outcomes in children with moderate to severe traumatic brain injury (TBI).

METHODS

Children with TBI, a Glasgow Coma Score of 8-12, and abnormal brain imaging were enrolled prospectively. Cerebral blood flow velocity (CBFV) was assessed within 24 h of trauma and daily thereafter through death, discharge, or hospital day 8, whichever came first. Twelve months from injury, participants completed neurodevelopmental testing.

RESULTS

Sixty-nine patients were enrolled. Low flow velocities (< 2 SD below age/gender normal) were found in 6% (n = 4). No patient with a single low CBFV measurement had a good neurologic outcome (Pediatric Glasgow Outcome Scale (GOS-E Peds) ≤ 4)). Normal flow velocities (± 2 SD around age/gender normal) were seen in 43% of participants (n = 30). High flow velocities (> 2 SD above age and gender normal with a Lindegaard ratio (LR) < 3) were identified in 23% of children (n = 16), and vasospasm (> 2 SD above age/gender normal with LR ≥ 3) was identified in 28% (n = 19). Children with good outcomes based on GOS-E Peds scoring were more likely to have had normal flow velocity than other flow patterns. No other differences in neurodevelopmental outcomes were noted.

CONCLUSIONS

Individual patient responses to TBI in terms of CBFV alterations were heterogeneous. Low flow was uniformly associated with a poor outcome. Patients with good outcomes were more likely to have normal flow. This suggests CBFV may serve as a prognostic indicator in children with TBI. Future studies are needed to determine if aberrant CBFVs are also a therapeutic target.

Impact of the Timing of Placement of an Intracranial Pressure Monitor on Outcomes in Children with Severe Traumatic Brain Injury

BACKGROUND

Severe traumatic brain injury (sTBI) is the leading cause of morbidity and mortality from trauma. Brain Trauma Foundation guidelines recommend intracranial pressure (ICP) monitoring in sTBI. We hypothesized that early ICP monitor placement was associated with better outcomes in children.

METHODS

This was a retrospective study of children with sTBI admitted to the participating pediatric intensive care units (PICUs) and entered into the Virtual Pediatric Systems (VPS), LLC, database between 1 January 2010 and 31 December 2015. We compared outcomes of patients who had an ICP monitor placed early (≤6 h from PICU admission) to those with later placement (> 6 to < 72 h). We collected demographics, diagnoses, procedure data, illness severity scores, outcomes, and site data. Multivariable regression analysis was used to identify variables independently associated with outcomes.

RESULTS

Twenty-seven percent of 3,608 patients with sTBI underwent ICP monitoring, 355 in the early and 156 in the later ICP monitoring groups, respectively. A higher proportion of patients in the early ICP monitoring group had worse markers of illness/injury severity; unadjusted analysis showed higher mortality in this group (31.3 vs. 21.8%, p = 0.029). Multivariable regression analysis showed that ICP monitoring was not independently associated with any of the outcomes.

CONCLUSION

Time to ICP monitoring was not associated with outcomes after pediatric sTBI.

Anatomical and Physiological Differences between Children and Adults Relevant to Traumatic Brain Injury and the Implications for Clinical Assessment and Care

General and central nervous system anatomy and physiology in children is different to that of adults and this is relevant to traumatic brain injury (TBI) and spinal cord injury. The controversies and uncertainties in adult neurotrauma are magnified by these differences, the lack of normative data for children, the scarcity of pediatric studies, and inappropriate generalization from adult studies. Cerebral metabolism develops rapidly in the early years, driven by cortical development, synaptogenesis, and rapid myelination, followed by equally dramatic changes in baseline and stimulated cerebral blood flow. Therefore, adult values for cerebral hemodynamics do not apply to children, and children cannot be easily approached as a homogenous group, especially given the marked changes between birth and age 8. Their cranial and spinal anatomy undergoes many changes, from the presence and disappearance of the fontanels, the presence and closure of cranial sutures, the thickness and pliability of the cranium, anatomy of the vertebra, and the maturity of the cervical ligaments and muscles. Moreover, their systemic anatomy changes over time. The head is relatively large in young children, the airway is easily compromised, the chest is poorly protected, the abdominal organs are large. Physiology changes—blood volume is small by comparison, hypothermia develops easily, intracranial pressure (ICP) is lower, and blood pressure normograms are considerably different at different ages, with potentially important implications for cerebral perfusion pressure (CPP) thresholds. Mechanisms and pathologies also differ—diffuse injuries are common in accidental injury, and growing fractures, non-accidental injury and spinal cord injury without radiographic abnormality are unique to the pediatric population. Despite these clear differences and the vulnerability of children, the amount of pediatric-specific data in TBI is surprisingly weak. There are no robust guidelines for even basics aspects of care in children, such as ICP and CPP management. This is particularly alarming given that TBI is a leading cause of death in children. To address this, there is an urgent need for pediatric-specific clinical research. If this goal is to be achieved, any clinician or researcher interested in pediatric neurotrauma must be familiar with its unique pathophysiological characteristics.

Time spent with impaired autoregulation is linked with outcome in severe infant/paediatric traumatic brain injury

BACKGROUND

It could be shown in traumatic brain injury (TBI) in adults that the functional status of cerebrovascular autoregulation (AR), determined by the pressure reactivity index (PRx), correlates to and even predicts outcome. We investigated PRx, cerebral perfusion pressure (CPP) and intracranial pressure (ICP) and their correlation to outcome in severe infant and paediatric TBI.

METHODS

Seventeen patients (range, 1 day to 14 years) with severe TBI (median GCS at presentation, 4) underwent long-term computerised ICP and mean arterial pressure (MAP) monitoring using dedicated software to determine CPP and PRx and optimal CPP (CPP level where PRx shows best autoregulation) continuously. Outcome was determined at discharge and at follow-up using the Glasgow Outcome Scale.

RESULTS

Favourable outcome was reached in eight patients, unfavourable outcome in seven patients. Two patients died. Nine patients underwent decompressive craniectomy to control ICP during Intensive Care Unit treatment. When dichotomised to outcome, no significant difference was found for overall ICP, CPP and PRx. The time with severely impaired AR (PRx >0.2) was significantly longer for patients with unfavourable outcome (64 h vs 6 h, p = 0.001). Continuously impaired AR of ≥24 h and age <1 year was associated to unfavourable outcome. Children with favourable outcome spent the entire monitoring time at or above the optimal CPP.

CONCLUSIONS

Integrity of AR has a similar role for outcome after TBI in the paediatric population as in adults. The amount of time spent with deranged AR seems to be associated with outcome; a factor especially critical for infant patients. The results of this preliminary study need to be validated in the future.

State of Cerebrovascular Autoregulation Correlates with Outcome in Severe Infant/Pediatric Traumatic Brain Injury

OBJECTIVE

It could be shown in adults with severe traumatic brain injury (TBI) that the functional status of cerebrovascular autoregulation (AR), determined by the pressure reactivity index (PRx), correlates with and even predicts outcome. We investigated PRx and its correlation with outcome in infant and pediatric TBI. Methods Ten patients (median age 2.8 years, range 1 day to 14 years) with severe TBI (Glasgow Coma Scale score <9 at presentation) underwent long-term computerized intracranial pressure (ICP) and mean arterial pressure (MAP) monitoring using dedicated software for continuous determination of cerebral perfusion pressure (CPP) and PRx. Outcome was determined at discharge and at follow-up at 6 months using the Glasgow Outcome Scale (GOS) score.

RESULTS

Median monitoring time was 182 h (range 22-355 h). Seven patients underwent decompressive craniectomy to control ICP during treatment in the intensive care unit. Favorable outcome (GOS 4 and 5) was reached in 4 patients, an unfavorable outcome (GOS 1-3) in 6 patients. When dichotomized to outcome, no correlation was found with ICP and CPP, but median PRx correlated well with outcome (r = -0.79, p = 0.006) and tended to be lower for GOS 4 and 5 (-0.04) than for GOS 1-3 (0.32; p = 0.067).

CONCLUSION

The integrity of AR seems to play the same fundamental role after TBI in the pediatric population as in adults and should be determined routinely. It carries an important prognostic value. PRx seems to be an ideal candidate parameter to guide treatment in the sense of optimizing CPP, aiming at improvement of cerebrovascular autoregulation (CPPopt concept).

Noninvasive screening for intracranial hypertension in children with acute, severe traumatic brain injury

OBJECT

The aim of this study was to determine the relationship between transcranial Doppler (TCD) derived pulsatility index (PI), end diastolic flow velocity (Vd), and intracranial pressure (ICP). The subjects in this study were 36 children admitted after severe traumatic brain injury (TBI) (postresuscitation Glasgow Coma Scale ≤ 8) undergoing invasive ICP monitoring.

METHODS

Subjects underwent a total of 148 TCD studies. TCD measurements of systolic flow velocity (Vs), Vd, and mean flow velocity (Vm) were performed on the middle cerebral artery (MCA) ipsilateral to the ICP monitor. The PI was calculated by the TCD software (Vs-Vd/Vm). ICP registrations were made in parallel with TCD measurements.

RESULTS

Using a PI threshold of 1.3, postinjury Day 0-1 PI had 100% sensitivity and 82% specificity at predicting an ICP ≥ 20 mm Hg (n = 8). During this time frame, a moderately strong relationship was observed between the MCA PI and actual ICP (r = 0.611, p = 0.01). When using a threshold of < 25 cm/sec, postinjury Day 0-1 Vd had a 56% sensitivity to predict an ICP ≥ 20 mm Hg. Beyond the initial 24 hours from injury, the sensitivity of an MCA PI of 1.3 to detect an ICP ≥ 20 mm Hg was 47%, and a weak relationship between actual ICP values and MCA PI (r = 0.376, p = 0.01) and MCA Vd (r = -0.284, p = 0.01) was found.

CONCLUSIONS

Postinjury Day 0-1 MCA PI > 1.3 has good sensitivity and specificity at predicting an ICP ≥ 20 mm Hg. In those children with TBI who initially do not meet clear criteria for invasive ICP monitoring but who are at risk for development of intracranial hypertension, TCD may be used as a noninvasive tool to screen for the development of elevated ICP in the first 24 hours following injury.

Photoacoustic computed microscopy

Photoacoustic microscopy (PAM) is emerging as a powerful technique for imaging microvasculature at depths beyond the ~1 mm depth limit associated with confocal microscopy, two-photon microscopy and optical coherence tomography. PAM, however, is currently qualitative in nature and cannot quantitatively measure important functional parameters including oxyhemoglobin (HbO2), deoxyhemoglobin (HbR), oxygen saturation (sO2), blood flow (BF) and rate of oxygen metabolism (MRO2). Here we describe a new photoacoustic microscopic method, termed photoacoustic computed microscopy (PACM) that combines current PAM technique with a model-based inverse reconstruction algorithm. We evaluate the PACM approach using tissue-mimicking phantoms and demonstrate its in vivo imaging ability of quantifying HbO2, HbR, sO2, cerebral BF and cerebral MRO2 at the small vessel level in a rodent model. This new technique provides a unique tool for neuroscience research and for visualizing microvasculature dynamics involved in tumor angiogenesis and in inflammatory joint diseases.

A neurovascular perspective for long-term changes after brain trauma

Traumatic brain injury (TBI) affects all age groups in a population and is an injury generating scientific interest not only as an acute event, but also as a complex brain disease with several underlying neurobehavioral and neuropathological characteristics. We review early and long-term alterations after juvenile and adult TBI with a focus on changes in the neurovascular unit (NVU), including neuronal interactions with glia and blood vessels at the blood-brain barrier (BBB). Post-traumatic changes in cerebral blood-flow, BBB structures and function, as well as mechanistic pathways associated with brain aging and neurodegeneration are presented from clinical and experimental reports. Based on the literature, increased attention on BBB changes should be integrated in studies characterizing TBI outcome and may provide a meaningful therapeutic target to resolve detrimental post-traumatic dysfunction.

Vascular neural network phenotypic transformation after traumatic injury: potential role in long-term sequelae

The classical neurovascular unit (NVU), composed primarily of endothelium, astrocytes, and neurons, could be expanded to include smooth muscle and perivascular nerves present in both the up- and downstream feeding blood vessels (arteries and veins). The extended NVU, which can be defined as the vascular neural network (VNN), may represent a new physiological unit to consider for therapeutic development in stroke, traumatic brain injury, and other brain disorders (Zhang et al., Nat Rev Neurol 8(12):711-716, 2012). This review is focused on traumatic brain injury and resultant post-traumatic changes in cerebral blood flow, smooth muscle cells, matrix, blood-brain barrier structures and function, and the association of these changes with cognitive outcomes as described in clinical and experimental reports. We suggest that studies characterizing TBI outcomes should increase their focus on changes to the VNN, as this may yield meaningful therapeutic targets to resolve posttraumatic dysfunction.

The frequency of cerebral ischemia/hypoxia in pediatric severe traumatic brain injury

INTRODUCTION

The frequency of adverse events, such as cerebral ischemia, following traumatic brain injury (TBI) is often debated. Point-in-time monitoring modalities provide important information, but have limited temporal resolution.

PURPOSE

This study examines the frequency of an adverse event as a point prevalence at 24 and 72 h post-injury, compared with the cumulative burden measured as a frequency of the event over the full duration of monitoring.

METHODS

Reduced brain tissue oxygenation (PbtO(2) < 10 mmHg) was the adverse event chosen for examination. Data from 100 consecutive children with severe TBI who received PbtO(2) monitoring were retrospectively examined, with data from 87 children found suitable for analysis. Hourly recordings were used to identify episodes of PbtO(2) less than 10 mmHg, at 24 and 72 h post-injury, and for the full duration of monitoring.

RESULTS

Reduced PbtO(2) was more common early than late after injury. The point prevalence of reduced PbtO(2) at the selected time points was relatively low (10 % of patients at 24 h and no patients at the 72-h mark post-injury). The cumulative burden of these events over the full duration of monitoring was relatively high: 50 % of patients had episodes of PbtO(2) less than 10 mmHg and 88 % had PbtO(2) less than 20 mmHg.

CONCLUSION

Point-in-time monitoring in a dynamic condition like TBI may underestimate the overall frequency of adverse events, like reduced PbtO(2), particularly when compared with continuous monitoring, which also has limitations, but provides a dynamic assessment over a longer time period.

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.

Pediatric sports-related concussion produces cerebral blood flow alterations

OBJECTIVES

The pathophysiology of sports-related concussion (SRC) is incompletely understood. Human adult and experimental animal investigations have revealed structural axonal injuries, decreases in the neuronal metabolite N-acetyl aspartate, and reduced cerebral blood flow (CBF) after SRC and minor traumatic brain injury. The authors of this investigation explore these possibilities after pediatric SRC.

PATIENTS AND METHODS

Twelve children, ages 11 to 15 years, who experienced SRC were evaluated by ImPACT neurocognitive testing, T1 and susceptibility weighted MRI, diffusion tensor imaging, proton magnetic resonance spectroscopy, and phase contrast angiography at <72 hours, 14 days, and 30 days or greater after concussion. A similar number of age- and gender-matched controls were evaluated at a single time point.

RESULTS

ImPACT results confirmed statistically significant differences in initial total symptom score and reaction time between the SRC and control groups, resolving by 14 days for total symptom score and 30 days for reaction time. No evidence of structural injury was found on qualitative review of MRI. No decreases in neuronal metabolite N-acetyl aspartate or elevation of lactic acid were detected by proton magnetic resonance spectroscopy. Statistically significant alterations in CBF were documented in the SRC group, with reduction in CBF predominating (38 vs 48 mL/100 g per minute; P = .027). Improvement toward control values occurred in only 27% of the participants at 14 days and 64% at >30 days after SRC.

CONCLUSIONS

Pediatric SRC is primarily a physiologic injury, affecting CBF significantly without evidence of measurable structural, metabolic neuronal or axonal injury. Further study of CBF mechanisms is needed to explain patterns of recovery.

Pediatric neurocritical care

Pediatric neurocritical care is an emerging multidisciplinary field of medicine and a new frontier in pediatric critical care and pediatric neurology. Central to pediatric neurocritical care is the goal of improving outcomes in critically ill pediatric patients with neurological illness or injury and limiting secondary brain injury through optimal critical care delivery and the support of brain function. There is a pressing need for evidence based guidelines in pediatric neurocritical care, notably in pediatric traumatic brain injury and pediatric stroke. These diseases have distinct clinical and pathophysiological features that distinguish them from their adult counterparts and prevent the direct translation of the adult experience to pediatric patients. Increased attention is also being paid to the broader application of neuromonitoring and neuroprotective strategies in the pediatric intensive care unit, in both primary neurological and primary non-neurological disease states. Although much can be learned from the adult experience, there are important differences in the critically ill pediatric population and in the circumstances that surround the emergence of neurocritical care in pediatrics.

Cerebrovascular response in children following severe traumatic brain injury

OBJECTIVE

To describe the pathophysiologic response in cerebral blood flow (CBF) and autoregulation after severe traumatic brain injury (TBI), Glasgow Coma Score (GCS) ≤8 on admission, in children, defining a baseline for future studies.

METHODS

Retrospective chart review of 95 patients following TBI, ages 0.1-18.4 years (<5 years (n = 44), <2 years (n = 17)) for CBF using Xenon Computerized Tomography (XeCT) over a 10-year period and 6-month Glasgow Outcome Scores (GOS). A total of 140 CBF studies were performed variably from admission up to post injury day (PID) 9; 27 patients underwent repeat CBF study after PaCO(2) was manipulated to determine CO(2) vasoreactivity (CO(2)VR).

RESULTS

Mean CBF on admission (PID 0, n = 26) was 32.05 ± 21.45 ml/100 g/min (mean ± SEM) and was ≤20 ml/100 g/min in eight patients. At PID 1-2, mean CBF increased to 55.36 ± 23.11 ml/100 g/min. There was significant differences in mean CBF of "favorable" outcomes (GOS ≥ 4) versus "unfavorable" outcome (GOS ≤ 3) (61.74 ± 18.27 vs. 46.54 ± 26.26, respectively (P = 0.01)). "Unfavorable" outcomes were seen in all patients with CBF ≤20 ml/100 mg/min during PID 0-2 and in 76.5% of children <2 years. CO(2)VR <2%/Torr PaCO(2) within PID 0-2 was significantly associated with "unfavorable" outcome (P = 0.029).

CONCLUSION

Younger age, early or later low CBF, and CO(2)VR <2%/Torr PaCO(2) were correlated with poorer outcomes in children. This represents the largest experience with XeCT CBF in children and confirms our preliminary report of low early CBF after TBI in children, disturbed CO(2)VR, and relationship of low CBF and unfavorable outcome.

Homogeneous immunosubtraction integrated with sample preparation enabled by a microfluidic format

Immunosubtraction is a powerful and resource-intensive laboratory medicine assay that reports both protein mobility and binding specificity. To expedite and automate this electrophoretic assay, we report on advances to the electrophoretic immunosubtraction assay by introducing a homogeneous, not heterogeneous, format with integrated sample preparation. To accomplish homogeneous immunosubtraction, a step-decrease in separation matrix pore-size at the head of a polyacrylamide gel electrophoresis (PAGE) separation channel enables "subtraction" of target analyte when capture antibody is present (as the large immune-complex is excluded from PAGE), but no subtraction when capture antibody is absent. Inclusion of sample preparation functionality via small pore size polyacrylamide membranes is also key to automated operation (i.e., sample enrichment, fluorescence sample labeling, and mixing of sample with free capture antibody). Homogeneous sample preparation and assay operation allows on-the-fly, integrated subtraction of one to multiple protein targets and reuse of each device. Optimization of the assay is detailed which allowed for ~95% subtraction of target with 20% non-specific extraction of large species at the optimal antibody-antigen ratio, providing conditions needed for selective target identification. We demonstrate the assay on putative markers of injury and inflammation in cerebrospinal fluid (CSF), an emerging area of diagnostics research, by rapidly reporting protein mobility and binding specificity within the sample matrix. We simultaneously detect S100B and C-reactive protein, suspected biomarkers for traumatic brain injury (TBI), in ~2 min. Lastly, we demonstrate S100B detection (65 nM) in raw human CSF with an estimated lower limit of detection of 3.25 nM, within the clinically relevant concentration range for detecting TBI in CSF. Beyond the novel CSF assay introduced here, a fully automated immunosubtraction assay would impact a spectrum of routine but labor and time-intensive laboratory medicine assays.

Physiological and histopathological responses following closed rotational head injury depend on direction of head motion

Rotational inertial forces are thought to be the underlying mechanism for most severe brain injuries. However, little is known about the effect of head rotation direction on injury outcomes, particularly in the pediatric population. Neonatal piglets were subjected to a single non-impact head rotation in the horizontal, coronal, or sagittal direction, and physiological and histopathological responses were observed. Sagittal rotation produced the longest duration of unconsciousness, highest incidence of apnea, and largest intracranial pressure increase, while coronal rotation produced little change, and horizontal rotation produced intermediate and variable derangements. Significant cerebral blood flow reductions were observed following sagittal but not coronal or horizontal injury compared to sham. Subarachnoid hemorrhage, ischemia, and brainstem pathology were observed in the sagittal and horizontal groups but not in a single coronal animal. Significant axonal injury occurred following both horizontal and sagittal rotations. For both groups, the distribution of injury was greater in the frontal and parietotemporal lobes than in the occipital lobes, frequently occurred in the absence of ischemia, and did not correlate with regional cerebral blood flow reductions. We postulate that these direction-dependent differences in injury outcomes are due to differences in tissue mechanical loading produced during head rotation.

Practical aspects of bedside cerebral hemodynamics monitoring in pediatric TBI

INTRODUCTION

Disturbances in cerebral hemodynamics may have a profound influence on secondary injury after traumatic brain injury (TBI), and many therapies in the neurocritical care unit may adversely affect cerebral blood flow. However, the clinician is often unaware of this when it occurs because practical methods for monitoring cerebral hemodynamics by the bedside have been lacking. Current imaging studies only provide a snapshot of the brain at one point in time, giving limited information about a dynamic condition.

DISCUSSION

This review will focus on key pathophysiological concepts required to understand changes in cerebral hemodynamics after TBI and the principles, potential benefits, and limitations of currently available bedside monitoring techniques, including transcranial Doppler, autoregulation, and local/regional cerebral blood flow.

Intracranial pressure monitoring for traumatic brain injury in the modern era

INTRODUCTION

Intracranial pressure (ICP) has become a cornerstone of care in adult and pediatric patients with traumatic brain injury (TBI).

DISCUSSION

Despite the fact that continuous monitoring of ICP in TBI was described almost 60 years ago, there are no randomized trials confirming the benefit of ICP monitoring and treatment in TBI. There is, however, a large body of clinical evidence showing that ICP monitoring influences treatment and leads to better outcomes if part of protocol-driven therapy. However, treatment of ICP has adverse effects, and there are several questions about ICP management that have yet to be definitively answered, particularly in pediatric TBI. This review examines the history and evolution of ICP monitoring, pathophysiological concepts that influence ICP interpretation, ongoing controversies, and the place of ICP monitoring in modern neurocritical care.

SNP improves cerebral hemodynamics during normotension but fails to prevent sex dependent impaired cerebral autoregulation during hypotension after brain injury

Traumatic brain injury (TBI) is a leading cause of morbidity in children and boys are disproportionately represented. Hypotension is common and worsens outcome after TBI. Previous studies show that adrenomedullin, a cerebrovasodilator, prevented sex dependent impairment of autoregulation during hypotension after piglet fluid percussion brain injury (FPI). We hypothesized that this concept was generalizable and that administration of another vasodilator, sodium nitroprusside (SNP), may equally improve CBF and cerebral autoregulation in a sex dependent manner after FPI. SNP produced equivalent percent cerebrovasodilation in male and female piglets. Reductions in pial artery diameter, cortical CBF, and cerebral perfusion pressure (CPP) concomitant with elevated intracranial pressure (ICP) after FPI were greater in male compared to female piglets during normotension which was blunted by SNP. During hypotension, pial artery dilation (PAD) was impaired more in the male than the female after FPI. However, SNP did not improve hypotensive PAD after FPI in females and paradoxically caused vasoconstriction in males. SNP did not prevent reductions in CBF, CPP or autoregulatory index during combined hypotension and FPI in either sex. SNP aggravated ERK MAPK upregulation after FPI. These data indicate that despite prevention of reductions in CBF after FPI, SNP does not prevent impairment of autoregulation during hypotension after FPI. These data suggest that therapies directed at a purely hemodynamic increase in CPP will fail to improve outcome during combined TBI and hypotension.

Continuous monitoring of cerebrovascular pressure reactivity after traumatic brain injury in children

OBJECTIVE

We hypothesized that pressure reactivity index (PRx) values indicating preserved cerebrovascular pressure autoregulation would be associated with survival in children with traumatic brain injury (TBI). This hypothesis was tested in a prospective, blinded, observational, pilot study.

METHODS

Twenty-one children admitted between May 2006 and September 2008 with severe TBI necessitating invasive intracranial pressure monitoring were enrolled in this study. The PRx was continuously monitored as a moving, linear correlation coefficient between low-frequency waves of intracranial and arterial blood pressures. Positive values of PRx approaching 1 indicate impaired cerebrovascular pressure reactivity, whereas negative PRx values or values close to 0 indicate preserved cerebrovascular pressure reactivity. Survival was the primary outcome and was compared with the average PRx value obtained during the intracranial pressure-monitoring period.

RESULTS

PRx was associated with survival in this cohort; survivors (N = 15) had a mean PRx +/- SD of 0.08 +/- 0.19, and nonsurvivors (N = 6) had a mean PRx of 0.69 +/- 0.21 (P = .0009). In this sample, continuous PRx monitoring suggested impaired cerebrovascular pressure reactivity at low levels of cerebral perfusion pressure (CPP) and intact cerebrovascular pressure reactivity at higher levels of CPP.

CONCLUSIONS

Intact cerebrovascular pressure reactivity quantified with the PRx is associated with survival after severe head trauma in children. The PRx is CPP dependent in children. The PRx may be useful for defining age-specific and possibly patient-specific optimal targets for CPP after TBI.

Cerebrovascular pathophysiology in pediatric traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is the leading cause of traumatic morbidity and mortality in children. Although there is increasing information concerning TBI in adults and experimental animal models, relatively little is known regarding cerebrovascular pathophysiology specific to children.

MATERIALS

A review of the pertinent medical literature.

RESULTS

Systemic and cerebral hemodynamic factors such as hypotension, hypoxia, hyperglycemia, and fever are associated with poor outcome in pediatric TBI. Similarly, cerebral autoregulation is often impaired after TBI and may adversely affect outcome, especially if systemic hemodynamics are altered. Furthermore, CO2 vasoreactivity may be altered after pediatric TBI and lead to either cerebral ischemia or hyperemia.

CONCLUSIONS

Understanding the effect of pediatric TBI on the cerebral circulation is needed to potentially develop protocols to improve outcome in this vulnerable population. Specifically, changes in pediatric cerebrovascular physiology and pathophysiology, including CO2 vasoreactivity and pressure autoregulation, must be understood and their mechanism elucidated.

Transcranial Doppler pulsatility index is not a reliable indicator of intracranial pressure in children with severe traumatic brain injury

BACKGROUND

The TCD-derived PI has been associated with ICP in adult studies but has not been well investigated in children. We examined the relationship between PI and ICP and CPP in children with severe TBI.

METHODS

Data were prospectively collected from consecutive TCD studies in children with severe TBI undergoing ICP monitoring. Ipsilateral ICP and CPP values were examined with Spearman correlation coefficient (mean values and raw observations), with a GEE, and as binary values (1 and 20 mm Hg, respectively).

RESULTS

Thirty-four children underwent 275 TCD studies. There was a weak relationship between mean values of ICP and PI (P = .04, r = 0.36), but not when raw observations (P = .54) or GEE (P = .23) were used. Pulsatility index was 0.76 when ICP was lower than 20 mm Hg and 0.86 when ICP was 20 mm Hg or higher. When PI was 1 or higher, ICP was lower than 20 mm Hg in 62.5% (25 of 40 studies), and when ICP was 20 mm Hg or higher, PI was lower than 1 in 75% (46 of 61 studies). The sensitivity and specificity of a PI threshold of 1 for examining the ICP threshold of 20 mm Hg were 25% and 88%, respectively. The relationship between CPP and PI was stronger (P = .001, r = -0.41), but there were too few observations below 50 mm Hg to examine PI at this threshold.

CONCLUSION

The absolute value of the PI is not a reliable noninvasive indicator of ICP in children with severe TBI. Further study is required to examine the relationship between PI and a CPP threshold of 50 mm Hg.

New concepts in treatment of pediatric traumatic brain injury

Emerging evidence suggests unique age-dependent responses following pediatric traumatic brain injury. The anesthesiologist plays a pivotal role in the acute treatment of the head-injured pediatric patient. This review provides important updates on the pathophysiology, diagnosis, and age-appropriate acute management of infants and children with severe traumatic brain injury. Areas of important clinical and basic science investigations germane to the anesthesiologist, such as the role of anesthetics and apoptosis in the developing brain, are discussed.

uPA modulates the age-dependent effect of brain injury on cerebral hemodynamics through LRP and ERK MAPK

We hypothesized that urokinase plasminogen activator (uPA) contributes to age-dependent early hyperemia after fluid percussion brain injury (FPI) by activating extracellular signal-related kinase (ERK) mitogen-activated protein kinase (MAPK), leading to histopathologic changes in the underlying cortex. Both cerebrospinal fluid (CSF) uPA and phosphorylation of CSF ERK MAPK was increased at 1 min after FPI in newborn pigs, but was unchanged in juvenile pigs. uPA and phosphorylated ERK MAPK, detectable in sham piglet brain by immunohistochemistry, was markedly elevated and associated with histopathology 4 h after FPI in the newborn but there was minimal staining and histopathology in the juvenile. EEIIMD, a peptide derived from PA inhibitor-1 that does not affect proteolysis, blunted FPI-induced phosphorylation of ERK MAPK. FPI produced pial artery dilation and increased cerebral blood flow at 1 min after insult in the newborn, but not in the juvenile. Antilipoprotein-related protein (LRP) antibody, EEIIMD, a soluble uPA antagonist, and the ERK MAPK antagonist U 0126 inhibited FPI-associated hyperemia. These data indicate that uPA is upregulated after FPI and produces an age-dependent early hyperemia followed by histopathology through an LRP- and ERK MAPK-dependent pathway.

Hypothermia following pediatric traumatic brain injury

Preclinical as well as clinical studies in traumatic brain injury (TBI) have established the likely association of secondary injury and outcome in adults in children following severe injury. Similarly, there is growing evidence in experimental laboratory studies that moderate hypothermia has a beneficial effect on outcome, though the exact mechanisms remain to be absolutely defined. The Pediatric TBI Guidelines provided the knowledge and background for standard management of children following severe TBI and highlighted that there are very few clinical studies to date. In particular with respect to temperature regulation and the use of hypothermia, initial findings of case series of small numbers were promising. Further preliminary randomized clinical trials, both single institution and multicenter, have provided the initial data on safety and efficacy, though larger, Phase III studies are necessary to ensure both the safety and efficacy of hypothermia in pediatric TBI prior to implementation as part of the standard of care. It is expected that hypothermia initiated early after severe TBI will have a protective effect on the pediatric brain and can be done safely, but this still remains to be definitively tested.

Modulating effect of apolipoprotein E polymorphisms on secondary brain insult and outcome after childhood brain trauma

OBJECTIVE

The aim of this study was to determine the relationship between apolipoprotein E (APO E) alleles, the amount of cerebral perfusion pressure (CPP) insult and outcome in children after brain trauma.

MATERIALS AND METHODS

In a prospective two-centre case-control study, the APO E genotypes of 65 critically ill children admitted after brain trauma were correlated with age-related CPP insult quantification, conscious state at the time of discharge from intensive care and global outcome at 6 months post-injury. One hundred sixty healthy age- and sex-matched children were genotyped as controls.

RESULTS

The CPP insult level among the e4 carriers with poor outcome was significantly less than the non-e4 carriers (p=0.03). Homozygotic e3 patients with good recovery did so despite having suffered nearly 26 times more CPP insult than those who were not e3 homzygous (p=0.02).

CONCLUSION

Different APO E alleles may potentially affect cerebral ischaemic tolerance differently in children after brain trauma.

Hyper flow and intracranial hypertension in diffuse axonal injury: an update to gennarelli doctrine

Twelve consecutive paediatric (six) and adult (six) patients harbouring a neuroradiological pattern consistent with diffuse axonal injury (DAI) along with slit ventricles underwent haemodynamic study in the Intensive Care Unit of our University. All the patients had GCS scores less than 8 after a severe brain injury. serial head computed tomography (CT) and magnetic resonance (MR) scans demonstrated a radiological pattern of DAI. Transcranial Doppler Sonography (TCD) of the middle cerebral arteries was performed through the temporal bone window in all the patients. All patients but one underwent a continuous monitoring of intracranial pressure (ICP) and cerebral extraction of 02 (CEO2). Therapy with barbiturates and hyperventilation was necessary in all the cases. In two patients (one adult and one paediatric) a bilateral decompressive craniectomy was performed in order to decrease a severe intracranial hypertension. Hyperflow along with intracranial hypertension, variably responsive to barbiturate therapy, was observed in all the patients by means of TCD and CEO2. In our patients intracranial hypertension along with hyperflow syndrome were found associated with DAI. Medical as well as surgical treatments were tailored according to the haemodynamic study.

Cerebral blood flow and autoregulation after pediatric traumatic brain injury

Traumatic brain injury is a global health concern and is the leading cause of traumatic morbidity and mortality in children. Despite a lower overall mortality than in adult traumatic brain injury, the cost to society from the sequelae of pediatric traumatic brain injury is very high. Predictors of poor outcome after traumatic brain injury include altered systemic and cerebral physiology, including altered cerebral hemodynamics. Cerebral autoregulation is often impaired after traumatic brain injury and may adversely impact the outcome. Although altered cerebrovascular hemodynamics early after traumatic brain injury may contribute to disability in children, there is little information regarding changes in cerebral blood flow and cerebral autoregulation after pediatric traumatic brain injury. This review addresses normal pediatric cerebral physiology and cerebrovascular pathophysiology after pediatric traumatic brain injury.

Incidence of hypo- and hypercarbia in severe traumatic brain injury before and after 2003 pediatric guidelines

OBJECTIVE

To examine the incidence of severe hypocarbia (PaCO2 <30 mm Hg) in patients with severe pediatric traumatic brain injury before and after publication of the 2003 pediatric guidelines (PG).

DESIGN

Retrospective cohort analysis.

SETTING

Harborview Medical Center, Seattle, Washington (January 1, 1995, to December 31, 2005).

PATIENTS

Children <15 yrs of age with severe pediatric traumatic brain injury.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The pre-PG group (before August 1, 2003) included 375 patients and the post-PG group included 89 patients. Post PG guidelines, there was a trend toward earlier (45 vs. 32 mins; p = .05) and more frequent (7.1 vs. 8.4 samples; p = .06) PaCO2 sampling within 48 hrs of admission. Children 0-2 yrs had a longer time (75.0 mins) between admission and first PaCO2 sample than older children (44.3 mins; p < .01). The youngest children also had the highest incidence of severe hypocarbia on the first PaCO2 sample (31% vs. 19%; p = .02). Incidence of severe hypocarbia was high and did not decline (60% vs. 52%; p = .2) after the PG guidelines. However, over the 11 yrs, the odds of severe hypocarbia decreased (adjusted odds ratio 0.9; 95% confidence interval 0.84-0.96). During both periods, the incidence of severe hypocarbia was highest during the first 2 hrs after hospital admission. Intracranial pressure monitors were used more frequently post-PG. In 62 of 82 (77%) patients with severe hypocarbia in whom an intracranial pressure monitor was in place, the preceding intracranial pressure was <20 mm Hg. Severe hypocarbia independently predicted inpatient mortality (adjusted odds ratio 2.8; 95% confidence interval 1.3-5.9).

CONCLUSIONS

Although PaCO2 sampling was more frequent during the post-PG period and severe hypocarbia decreased during successive study years, the incidence of severe hypocarbia remained high during the first 48 hrs after hospital admission during the post-PG period. Time to PaCO2 sampling was longer in young children and associated with more severe hypocarbia. The presence of severe hypocarbia predicted mortality.

Pediatric traumatic brain injury: not just little adults

PURPOSE OF REVIEW

This review will update the reader on the most significant recent findings with regards to both the clinical research and basic science of pediatric traumatic brain injury.

RECENT FINDINGS

The developing brain is not simply a smaller version of the mature brain. Studies have uncovered important distinctions of the younger brain after traumatic brain injury, including an increased propensity for apoptosis, age-dependent parameters for cerebral blood flow and metabolism, development-specific biomarkers, increased likelihood of early posttraumatic seizures, differential sensitivity to commonly used neuroactive medications and altered neuroplasticity during recovery from injury. Specifically, there is strong preclinical evidence for increased neuronal apoptosis in the developing brain being triggered by anesthetics and anticonvulsants, making it paramount that future studies more clearly delineate preferred agents and specific indications for use, incorporating long-term functional outcomes as well as short-term benefits. In addition, the young brain may actually benefit from therapeutic interventions that have been less effective following adult traumatic brain injury, such as decompressive craniectomy and hypothermia.

SUMMARY

An increasing body of evidence demonstrates the importance of establishing age-dependent guidelines for physiological monitoring, pharmacological intervention, management of intracranial pressure and facilitating recovery of function.

[Decompressive craniectomy in children and adolescents with head injury: analysis of seven cases]

INTRODUCTION

Decompressive craniectomy (DC) is a surgical technique used to treat patients with elevated intracranial pressure often found in head injury. Its indication remains a controversial issue in the pediatric population.

OBJECTIVE

To report seven cases managed with this technique.

METHOD

Retrospective study of seven patients, aged from 2 to 17 years, treated with unilateral DC due to increased intracranial pressure (ICP) as a consequence of head injury. All patients had ICP monitored post operatively and the DC classified as ultra-early (<6h), early (6-12h) or late (>24h) according to the time of its application. The minimum follow-up was six months.

RESULTS

Patients were evaluated with CT scans and clinical exams, and graded according the Glasgow Outcome Scale (GOS). Three patients deceased (GOS1), one was in vegetative state (GOS2), two recovered but still requiring nursing care (GOS3 and 4), and one had a full recovery (GOS5) at hospital discharge. After six months the GOS2 and a GOS3 patients achieved full recovery (GOS5). Subdural collection (2), hydrocephalus (1) and superficial infection (1) occurred as complication. Two patients had autologous cranioplasty and the other two heterologous cranioplasty.

CONCLUSION

Decompressive craniectomy remains a feasible treatment method to lower the ICP, but is not safe from complications. A multicentric study should be done for appropriate protocol treatment of pediatric patients.

Brain tissue oxygen monitoring in pediatric patients with severe traumatic brain injury

OBJECT

Intracranial pressure (ICP) and cerebral perfusion pressure (CPP) monitoring are fundamental to the management of severe traumatic brain injury (TBI). In adults, brain tissue oxygen monitoring (specifically PO2) and treatment have been shown to be safe additions to conventional neurocritical care and are associated with improved outcome. Brain tissue oxygen monitoring, however, has not been described in pediatric patients with TBI. In this report, the authors present preliminary experience with the use of ICP and PO2 monitoring in this population.

METHODS

Pediatric patients (age <18 years) with severe TBI (Glasgow Coma Scale score <8) admitted to a Level 1 trauma center who underwent ICP and PO2 monitoring were evaluated. Therapy was directed at maintaining ICP below 20 mm Hg and age-appropriate CPP (> or =40 mm Hg). Data obtained in six patients (two girls and four boys ranging in age from 6-16 years) were analyzed. Brain tissue oxygen levels were significantly higher (p < 0.01) at an ICP of less than 20 mm Hg (PO2 29.29 +/- 7.17 mm Hg) than at an ICP of greater than or equal to 20 mm Hg (PO2 22.83 +/- 13.85 mm Hg). Significant differences (p < 0.01) were also measured when CPP was less than 40 mm Hg (PO2 2.53 +/- 7.98 mm Hg) and greater than or equal to 40 mm Hg (PO2 28.97 +/- 7.85 mm Hg).

CONCLUSIONS

Brain tissue oxygen monitoring may be a safe and useful addition to ICP monitoring in the treatment of pediatric patients with severe TBI.

Haemodynamic patterns in children with posttraumatic diffuse brain swelling. A preliminary study in 6 cases with neuroradiological features consistent with diffuse axonal injury

BACKGROUND

In the present report we describe the cerebral haemodynamics and the neuroradiological findings observed in six consecutive children, three males and three females aged 4-15.6 yrs (mean age 8.95) displaying a neuroradiological pattern consistent with diffuse axonal injury (DAI) along with slit ventricles.

METHODS

All the patients were admitted to the Paediatric Intensive Care Unit with GCS scores less than 8 after a severe brain injury. Serial head computed to mography (CT) and magnetic resonance (MR) scans demonstrated a radiological pattern of DAI. Transcranial Doppler Sonography (TCD) of the middle cerebral arteries was performed through the temporal bone window in all the patients. All patients but one underwent a continuous monitoring of intracranial pressure (ICP) and cerebral extraction of O(2) (CEO(2)). Treatment with barbiturates and hyperventilation was necessary in all the cases. In one patient, a bilateral decompressive cran iectomy was performed in order to decrease severe in tracranial hypertension.

RESULTS

Hyperflow along with intracranial hyper tension, variably responsive to barbiturate medication, was observed in all the patients by means of TCD and CEO(2).

CONCLUSIONS

Intracranial hypertension can be elevated in pediatric posttraumatic hyperflow syndromes associated with DAI. The observation of the time course of the parameters studied allowed us to modify the pharmacological treatment and/or perform surgical decompression (external cerebrospinal fluid (CSF) drainage in five cases; decompressive craniectomy in one case). Compartmental hyperflow TCD pattern was evident in only one patient. Although the limited number of pa tients in our series does not allow definite conclusions, we strongly believe that TCD, with ICP and CEO(2) monitoring, are useful tools in planning surgical strategy in children with neuroradiological signs of DAI.

Pediatric traumatic brain injury: quo vadis?

In this review, five questions serve as the framework to discuss the importance of age-related differences in the pathophysiology and therapy of traumatic brain injury (TBI). The following questions are included: (1) Is diffuse cerebral swelling an important feature of pediatric TBI and what is its etiology? (2) Is the developing brain more vulnerable than the adult brain to apoptotic neuronal death after TBI and, if so, what are the clinical implications? (3) If the developing brain has enhanced plasticity versus the adult brain, why are outcomes so poor in infants and young children with severe TBI? (4) What contributes to the poor outcomes in the special case of inflicted childhood neurotrauma and how do we limit it? (5) Should both therapeutic targets and treatments of pediatric TBI be unique? Strong support is presented for the existence of unique biochemical, molecular, cellular and physiological facets of TBI in infants and children versus adults. Unique therapeutic targets and enhanced therapeutic opportunities, both in the acute phase after injury and in rehabilitation and regeneration, are suggested.

Lack of effects of 1439 MHz electromagnetic near field exposure on the blood-brain barrier in immature and young rats

Possible effects of 1439 MHz electromagnetic near field (EMF) exposure on the blood-brain barrier (BBB) were investigated using immature (4 weeks old) and young (10 weeks old) rats, equivalent in age to the time when the BBB development is completed and the young adult, respectively. Alteration of BBB related genes, such as those encoding p-glycoprotein, aquaporin-4, and claudin-5, was assessed at the protein and mRNA levels in the brain after local exposure of the head to EMF at 0, 2, and 6 W/kg specific energy absorption rates (SARs) for 90 min/day for 1 or 2 weeks. Although expression of the 3 genes was clearly decreased after administration of 1,3-dinitrobenzene (DNB) as a positive control, when compared with the control values, there were no pathologically relevant differences with the EMF at any exposure levels at either age. Vascular permeability, monitored with reference to transfer of FITC-dextran, FD20, was not affected by EMF exposure. Thus, these findings suggest that local exposure of the head to 1439 MHz EMF exerts no adverse effects on the BBB in immature and young rats.

Decompressive craniectomy in pediatric patients with traumatic brain injury with intractable elevated intracranial pressure

BACKGROUND

Care of pediatric traumatic brain injury (TBI) has placed emphasis on maximizing cerebral perfusion to prevent ischemia and reperfusion injury. A subset of patients with TBI will continue to have refractory intracranial pressure (ICP) elevation despite aggressive therapy including ventriculostomy, pentobarbital coma, hypertonic saline, and diuretics. Decompressive craniectomy (DC) is a controversial treatment of severe TBI. It is our hypothesis that DC can enhance survival and minimize secondary brain injury in this patient subset.

METHODS

Patients younger than 20 years treated at a level I regional trauma center between November 2001 and November 2004, who met inclusion criteria for the Brain Trauma Foundation TBI-trac clinical database were included. All patients with a mechanism of injury consistent with TBI and Glasgow Coma Scale score of less than 9 for at least 6 hours after resuscitation and who did not die in the emergency department are entered into a clinical database. Patients who arrived at the study hospital more than 24 hours after injury are excluded.

RESULTS

There were 30 patients with TBI identified. The mean Glasgow Coma Scale score at presentation was 8 with a range of 3 to 13. Six patients underwent DC for intractable elevated ICP. Of 6 patient's postoperative ICP, 5 were less than 20 mm Hg. One patient required a return to the operating room where further débridement of brain was performed. All patients who received a DC survived and were discharged to a TBI rehabilitation facility.

CONCLUSION

Although this is a small sample, DC should be considered in patients with TBI with refractory elevated ICP. Long-term follow-up of this patient population should consist of neuropsychiatric evaluation in conjunction with measurement of social function.

The role of decompressive craniectomy in the management of traumatic brain injury: a critical review

Brain swelling and intracranial hypertension following severe head injury are known to contribute to secondary brain damage, and have been shown to adversely affect patient outcome. The use of unilateral craniectomy following the evacuation of a mass lesion, such as acute subdural haematoma or traumatic intracerebral haematoma, is accepted practice. The following review focuses on a bi-fronto-temporal decompressive craniectomy, used as an isolated operation for the control of intracranial hypertension, secondary to diffuse brain swelling refractory to medical management. Though the operation is being increasingly used, current opinion is still divided regarding its overall effects on outcome. This review examines the experimental and clinical evidence for and against the use of decompressive craniectomy, highlights the lack of class I evidence relevant to this topic and emphasises the necessity for well-designed prospective randomised controlled trials.

Age and cerebral circulation

Cerebral blood flow, and its control, vary as a function of age. This review focuses on the perinatal period and compares/contrasts this age period to that of the juvenile/adult. Additionally, this review describes mechanisms important in the control of the cerebral circulation as a function of age during physiologic and pathologic conditions. Two topics of pathophysiology are considered: cerebral hypoxia ischemia, often seen in perinates due to problems with delivery or respiratory management post delivery, and traumatic brain injury, described as the shaken impact syndrome, an example of child abuse. Clinically, it is important to understand the pathophysiology of the cerebral circulation in order to optimize mechanistically appropriate therapeutic modalities.

Traumatic brain injury in children--clinical implications

Traumatic brain injury (TBI) is the leading cause of death in childhood; however only very few studies focusing on the specific pathophysiology and treatment have been published to date. Head trauma is more likely in young children than in adults given the same deceleration of the body due to their large and heavy heads and weak cervical ligaments and muscles. Resulting brain injury is more severe due to their thin, pliable skulls and the yet unfused sutures. Accordingly, children below the age of 4 years have lower chances of a full recovery after severe TBI, although in general, neurologic recovery after severe brain injury in children is better than in adults. The time course of brain injury can be divided into two steps: primary and secondary injury. Primary brain injury exclusively results from the initial impact. In contrast, adverse physiologic conditions during recovery after head trauma may account for additional brain damage, which is then referred to as secondary brain injury. As primary brain injury can only be influenced by preventive measures, all therapeutic efforts during the post-injury period focus on the reduction of secondary injury to the traumatized brain. Several mechanisms have been identified to be involved in the development of post-traumatic secondary brain injury, which render the rationale for the key treatment strategies. Three evidence based measures are of critical importance to prevent or minimize secondary brain injury: (1) avoid hypoxemia, (2) avoid post-traumatic arterial hypotension, and (3) refer the traumatized child to an experienced trauma team at a center that provides the availability of special equipment, e.g. for surgical procedures and airway management, for this age group. For several other therapeutical means, e.g. hypothermia or specific surgical interventions, clinical evidence to date is insufficient to allow recommendation as rescue treatment for children at risk of severe neurological sequelae following TBI. This review discusses the clinical implication of pathophysiologic mechanisms of TBI in the developing brain according to the recent literature and current guidelines. It follows the clinical approach to a head injured child, that can be divided into three phases, i.e. initial assessment and stabilization, followed by first tier, and if necessary second tier therapeutic interventions to assure adequate oxygenation and perfusion of the brain.

Relationship between total cerebral blood flow and ICP measured noninvasively with dynamic MRI technique in healthy subjects

Cerebral blood flow and ICP are important neurophysiologic parameters known to be affected by pathology and by trauma. Limited data on the relationship between these parameters following head trauma is inconsistent with regard to whether these parameters are correlated. Data on the relationship between these parameters in the healthy state is not readily available due to a lack of noninvasive means to measure these important parameters. A recently developed noninvasive MRI-based method for simultaneous measurement of total cerebral blood flow and intracranial pressure was applied to establish the relationship between ICP and TCBF values in healthy subjects. Seventy-one simultaneous measurements of CBF and ICP were obtained from 23 healthy young adults. These results demonstrated that CBF values span over a much narrower range compared with ICP. The relationship between the inter-individual CBF and ICP measurements suggest that in the healthy state and in rest these parameters are not correlated.