Why are clinical trials in pediatric head injury so difficult?

Acute minocycline administration reduces brain injury and improves long-term functional outcomes after delayed hypoxemia following traumatic brain injury

Clinical trials of therapeutics for traumatic brain injury (TBI) demonstrating preclinical efficacy for TBI have failed to replicate these results in humans, in part due to the absence of clinically feasible therapeutic windows for administration. Minocycline, an inhibitor of microglial activation, has been shown to be neuroprotective when administered early after experimental TBI but detrimental when administered chronically to human TBI survivors. Rather than focusing on the rescue of primary injury with early administration of therapeutics which may not be clinically feasible, we hypothesized that minocycline administered at a clinically feasible time point (24 h after injury) would be neuroprotective in a model of TBI plus delayed hypoxemia. We first explored several different regimens of minocycline dosing with the initial dose 24 h after injury and 2 h prior to hypoxemia, utilizing short-term neuropathology to select the most promising candidate. We found that a short course of minocycline reduced acute microglial activation, monocyte infiltration and hippocampal neuronal loss at 1 week post injury. We then conducted a preclinical trial to assess the long-term efficacy of a short course of minocycline finding reductions in hippocampal neurodegeneration and synapse loss, preservation of white matter myelination, and improvements in fear memory performance at 6 months after injury. Timing in relation to injury and duration of minocycline treatment and its impact on neuroinflammatory response may be responsible for extensive neuroprotection observed in our studies.

N-acetylcysteine reduces brain injury after delayed hypoxemia following traumatic brain injury

Preclinical investigations into neuroprotective agents for traumatic brain injury (TBI) have shown promise when administered before or very early after experimental TBI. However clinical trials of therapeutics demonstrating preclinical efficacy for TBI have failed to replicate these results in humans, a lost in translation phenomenon. N-acetylcysteine (NAC) is a potent anti-oxidant with demonstrated efficacy in pre-clinical TBI when administered early after primary injury. Utilizing our clinically relevant mouse model, we hypothesized that NAC administration in a clinically relevant timeframe could improve the brain's resilience to the secondary insult of hypoxemia. NAC or vehicle administered daily starting 2 h prior to hypoxemia (24 h after controlled cortical impact) for 3 doses in male mice reduced short-term axonal injury and hippocampal neuronal loss. Six month behavioral assessments including novel object recognition, socialization, Barnes maze, and fear conditioning did not reveal performance differences between sham controls and injured mice receiving NAC or saline vehicle. At 7 months after injury, NAC administered mice had reduced hippocampal neuronal loss but no reduction in lesion volume. In summary, our preclinical trial to test the neuroprotective efficacy of NAC against a secondary hypoxic insult after TBI demonstrated short and long-term neuropathological evidence of neuroprotection but a lack of detectable differences in long-term behavioral assessments between sham controls and injured mice limits conclusions on its impact on long-term neurobehavioral outcomes.

The Base Deficit, International Normalized Ratio, and Glasgow Coma Scale (BIG) Score, and Functional Outcome at Hospital Discharge in Children With Traumatic Brain Injury

OBJECTIVES

To examine the association of the base deficit, international normalized ratio, and Glasgow Coma Scale (BIG) score on emergency department arrival with functional dependence at hospital discharge (Pediatric Cerebral Performance Category ≥ 4) in pediatric multiple trauma patients with traumatic brain injury.

DESIGN

A retrospective cohort study of a pediatric trauma database from 2001 to 2018.

SETTING

Level 1 trauma program at a university-affiliated pediatric institution.

PATIENTS

Two to 17 years old children sustaining major blunt trauma including a traumatic brain injury and meeting trauma team activation criteria.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Two investigators, blinded to the BIG score, determined discharge Pediatric Cerebral Performance Category scores. The BIG score was measured on emergency department arrival. The 609 study patients were 9.7 ± 4.4 years old with a median Injury Severity Score 22 (interquartile range, 12). One-hundred seventy-one of 609 (28%) had Pediatric Cerebral Performance Category greater than or equal to 4 (primary outcome). The BIG constituted a multivariable predictor of Pediatric Cerebral Performance Category greater than or equal to 4 (odds ratio, 2.39; 95% CI, 1.81-3.15) after adjustment for neurosurgery requirement (odds ratio, 2.83; 95% CI, 1.69-4.74), pupils fixed and dilated (odds ratio, 3.1; 95% CI, 1.49-6.38), and intubation at the scene or referral hospital (odds ratio, 2.82; 95% CI, 1.35-5.87) and other postulated predictors of poor outcome. The area under the BIG receiver operating characteristic curve was 0.87 (0.84-0.90). Using an optimal BIG cutoff less than or equal to 8, sensitivity and negative predictive value for functional dependence at discharge were 93% and 96%, respectively, compared with a sensitivity of 79% and negative predictive value of 91% with Glasgow Coma Scale less than or equal to 8. In children with Glasgow Coma Scale 3, the BIG score was associated with brain death (odds ratio, 2.13; 95% CI, 1.58-2.36). The BIG also predicted disposition to inpatient rehabilitation (odds ratio, 2.26; 95% CI, 2.17-2.35).

CONCLUSIONS

The BIG score is a simple, rapidly obtainable severity of illness score that constitutes an independent predictor of functional dependence at hospital discharge in pediatric trauma patients with traumatic brain injury. The BIG score may benefit Trauma and Neurocritical care programs in identifying ideal candidates for traumatic brain injury trials within the therapeutic window of treatment.

Pediatric Donation After Circulatory Determination of Death: A Scoping Review

OBJECTIVE

Although pediatric donation after circulatory determination of death is increasing in frequency, there are no national or international donation after circulatory determination of death guidelines specific to pediatrics. This scoping review was performed to map the pediatric donation after circulatory determination of death literature, identify pediatric donation after circulatory determination of death knowledge gaps, and inform the development of national or regional pediatric donation after circulatory determination of death guidelines.

DATA SOURCES

Terms related to pediatric donation after circulatory determination of death were searched in Embase and MEDLINE, as well as the non-MEDLINE sources in PubMed from 1980 to May 2014.

STUDY SELECTION

Seven thousand five hundred ninety-seven references were discovered and 85 retained for analysis. All references addressing pediatric donation after circulatory determination of death were considered. Exclusion criteria were articles that did not address pediatric patients, animal or laboratory studies, surgical techniques, and local pediatric donation after circulatory determination of death protocols. Narrative reviews and opinion articles were the most frequently discovered reference (25/85) and the few discovered studies were observational or qualitative and almost exclusively retrospective.

DATA EXTRACTION

Retained references were divided into themes and analyzed using qualitative methodology.

DATA SYNTHESIS

The main discovered themes were 1) studies estimating the number of potential pediatric donation after circulatory determination of death donors and their impact on donation; 2) ethical issues in pediatric donation after circulatory determination of death; 3) physiology of the dying process after withdrawal of life-sustaining therapy; 4) cardiac pediatric donation after circulatory determination of death; and 5) neonatal pediatric donation after circulatory determination of death. Donor estimates suggest that pediatric donation after circulatory determination of death will remain an event less common than brain death, albeit with the potential to substantially expand the existing organ donation pool. Limited data suggest outcomes comparable with organs donated after neurologic determination of death. Although there is continued debate around ethical aspects of pediatric donation after circulatory determination of death, all pediatric donation after circulatory determination of death publications from professional societies contend that pediatric donation after circulatory determination of death can be practiced ethically.

CONCLUSIONS

This review provides a comprehensive overview of the published literature related to pediatric donation after circulatory determination of death. In addition to informing the development of pediatric-specific guidelines, this review serves to highlight several important knowledge gaps in this topic.

Neuroglobin upregulation offers neuroprotection in traumatic brain injury

OBJECTIVES

The aim of this study was to investigate rat neuroglobin (rNGB) expression level after traumatic brain injury (TBI) and further study its neuroprotective effects in TBI when it was overexpressed in adenoviral vector.

METHODS

The Wistar rats (280-320 g) were divided into control, 12 and 36 hours after TBI groups (n = 3) and their TBI model was established. Subsequently, NGB expression level was examined by Western blot and immunohistochemical. Beyond that, adenoviral vectors pAdEasy-rNGB-GFP and pAdEasy-GFP were constructed and transfected into the rat brain respectively (pAdEasy-GFP was control), and the neuroprotective effects were examined by immunohistochemical.

RESULTS

Immunohistochemical and Western blot results demonstrated that NGB expression level was increased at 12 and 36 hours after TBI injury compare with control. Meanwhile, the pAdEasy-rNGB-GFP transfected rats suffered less necrosis and apoptosis compare to control.

CONCLUSIONS

NGB was upregulated in TBI and overexpressed rNGB had a significant neuroprotection in TBI. However, the mechanism remained unknown. This study suggested that rNGB overexpression may be a new strategy for treating of TBI.

The role of prothrombotic factors in the ocular manifestations of abusive and non-abusive head trauma: a feasibility study

OBJECTIVES

Retinal hemorrhage is a cardinal manifestation of abusive head injury. Thrombophilia is relatively common in the general population and in adults can be associated with retinal hemorrhage. The specificity of retinal hemorrhage for abusive head trauma in the presence of prothrombotic factors, in particular following non-abusive head trauma, has not been investigated. Our objective was to determine whether the hypothesis that prothrombotic factors affect specificity of retinal hemorrhage to AHT can be tested. This may have important ramifications both for diagnosis and expert witness testimony.

METHODS

To investigate the feasibility of studying this issue, we conducted a prospective cohort study of children with abusive and non-abusive head trauma. Thrombophilia screening and ophthalmic examinations were performed.

RESULTS

Six of 30 admitted children were fully enrolled. Enrollment obstacles included caregiver stress, animosity towards allegations of abuse, child protection services involvement, and research phlebotomy coordination. Prevalence of thrombophilia was high in children with retinal hemorrhage and in 1 case the question of hemorrhage adjudicated as abuse was considered in light of a history of a fall.

CONCLUSION

We estimate that to answer the critical question of retinal hemorrhage specificity for abuse in the presence of thrombophilia will require 53 centers for a 1 year study or 18 centers for a 3-year study. We identify potential obstacles and interventions.

Neurocritical care monitoring correlates with neuropathology in a swine model of pediatric traumatic brain injury

BACKGROUND

Small-animal models have been used in traumatic brain injury (TBI) research to investigate the basic mechanisms and pathology of TBI. Unfortunately, successful TBI investigations in small-animal models have not resulted in marked improvements in clinical outcomes of TBI patients.

OBJECTIVE

To develop a clinically relevant immature large-animal model of pediatric neurocritical care following TBI.

METHODS

Eleven 4-week-old piglets were randomly assigned to either rapid axial head rotation without impact (n = 6) or instrumented sham (n = 5). All animals had an intracranial pressure monitor, brain tissue oxygen tension (Pbto(2)) probe, and cerebral microdialysis probe placed in the frontal lobe and data collected for 6 hours following injury.

RESULTS

Injured animals had sustained elevations in intracranial pressure and lactate-pyruvate ratio (LPR), and decreased Pbto(2) compared with sham. Pbto(2) and LPR from separate frontal lobes had strong linear correlation in both sham and injured animals. Neuropathologic examination demonstrated significant axonal injury and infarct volumes in injured animals compared with sham at 6 hours postinjury. Averaged over time, Pbto(2) in both injured and sham animals had a strong inverse correlation with total injury volume. Average LPR had a strong correlation with total injury volume.

CONCLUSION

LPR and Pbto(2) can be utilized as serial nonterminal secondary markers in our injury model for neuropathology, and as evaluation metrics for novel interventions and therapeutics in the acute postinjury period. This translational model bridges a vital gap in knowledge between TBI studies in small-animal models and clinical trials in the pediatric TBI population.