Severe pediatric traumatic brain injury (TBI) is associated with unfavorable outcomes secondary to injury from activation of the inflammatory cascade, the release of excitotoxic neurotransmitters, and changes in the reactivity of cerebral vessels, causing ischemia. Hypoperfusion of injured brain tissues after TBI is also associated with unfavorable outcomes. Therapeutic hypothermia is an investigational treatment strategy for use in patients with severe TBI that has shown differential effects on various cerebrospinal fluid (CSF) mediators in pediatric patients. Endothelin-1 (ET-1) is a powerful vasoconstrictor that exerts its effects on the cerebrovascular endothelium for sustained periods after TBI. The purpose of this study was to determine if CSF concentrations of ET-1 are increased after severe TBI in children, and if they are associated with demographics and outcomes that are affected by therapeutic hypothermia. This was an ancillary study to a prospective, randomized-controlled trial of early hypothermia in a tertiary care pediatric intensive care unit. Children (n = 34, age 3 months-15 years) suffering from severe TBI were randomized to hypothermia (n = 19) and normothermia (n = 15) as part of the efficacy study. Children undergoing diagnostic lumbar puncture (n = 11) to rule out infection were used as controls. Patients received either mild to moderate hypothermia (32-33°C) or normothermia as part of their treatment protocol. CSF was serially collected during the first 5 days after TBI. ET-1 concentrations were quantitated in patient and control CSF samples by a validated ELISA in duplicate with a limit of quantification of 0.195 pg/mL. CSF ET-1 concentrations were increased by two- to threefold in children after TBI compared to controls, and the increase was sustained for up to 5 days post-TBI. This relationship was not affected by hypothermia, and there were no differences in ET-1 response between children with inflicted and accidental TBI. Group-based trajectory analysis revealed two distinct groups with similar ET-1 levels over time. Univariate analysis showed a significant association between ET-1 levels and Glasgow Outcome Scale (GOS) scores, for which higher ET-1 levels over time were associated with unfavorable outcomes. ET-1 is increased in children with severe TBI and is associated with unfavorable outcomes. This increase in ET-1 may mediate the hypoperfusion or cerebrovascular dysfunction accompanying severe TBI in children. Importantly, hypothermia does not affect the brain's ET-1 response as measured in the CSF.

Background Endothelin-1 (ET-1) is a potent vasoconstrictor implicated in the pathogenesis of vasospasm and delayed cerebral ischemia (DCI) in aneurysmal subarachnoid hemorrhage (aSAH) patients. The aim of this study was to investigate the relationship between cerebrospinal fluid (CSF) ET-1 levels and angiographic vasospasm and DCI. Methods Patients with aSAH were consented (n = 106). Cerebral vasospasm was determined by angiography. DCI was determined by transcranial Doppler (TCD) results and/or angiogram results with corresponding clinical deterioration. CSF ET-1 levels over 14 days after the initial insult was quantified by ELISA. ET-1 analysis included a group-based trajectory analysis and ET-1 exposure rate during 24, 48, and 72 h prior to, as well as 72 h post angiography, or clinical deterioration. Results Trajectory analysis revealed two distinct groups of subjects with 56% of patients in the low ET-1 trajectory group (mean at day 1 = 0.31 pg/ml; SE = 0.04; mean at day 14 = 0.41 pg/ml; SE = 0.15) and 44% of patients in the high ET-1 trajectory group (mean at day 1 = 0.65 pg/ml; SE = 0.08; mean at day 14 = 0.61 pg/ml; SE = 0.06). Furthermore, we observed that ET-1 exposure rate 72 h before angiography and clinical spasm was a significant predictor of both angiographic vasospasm and DCI, whereas, ET-1 exposure after angiography and clinical spasm was not associated with either angiographic vasospasm or DCI. Conclusion Based on these results we conclude that ET-1 concentrations are elevated in a sub-group of patients and that the acute (72 h prior to angiography and clinical neurological deterioration), but not chronic, elevations in CSF ET-1 concentrations are indicative of the pathogenic alterations of vasospasm and DCI in aSAH patients.

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Aneurysmal subarachnoid hemorrhage is a type of stroke with high morbidity and mortality. Increased endothelin-1 (ET-1) levels have been associated with increased risk of cerebral vasospasm, which is associated with increased morbidity. The purpose of this study was to investigate the relationships between ET-1 genotypes and ET-1 protein levels in cerebrospinal fluid (CSF) measured 72 hr before angiographic vasospasm measurement in subjects at high risk of cerebral vasospasm. Specifically, this study evaluated the differences between variant positive and variant negative groups of nine different ET-1 single-nucleotide polymorphisms (SNPs) in relationship with the ET-1 protein exposure rate. The CSF ET-1 protein levels were quantified using enzyme-linked immunosorbent assay. One functional SNP and eight ET-1 tagging SNPs were selected because they represent genetic variability in the entire ET-1 gene. The variant negative group of SNP rs2070699 was associated with a significantly higher ET-1 exposure rate than the variant positive group ( p = 0.004), while the variant positive group of the rs5370 group showed a trend toward association with a higher ET-1 exposure rate ( p = 0.051). Other SNPs were not informative. This is the first study to show differences in ET-1 exposure rate 72 hr before angiography in relation to ET-1 genotypes. These exploratory findings need to be replicated in a larger study; if replicated, these differences in genotypes may be a way to inform clinicians of those patients at a higher risk of increased ET-1 protein levels, which may lead to a higher risk of angiographic vasospasm.

Objectives Pathological increases in asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase (NOS) inhibitor, have been implicated in endothelial dysfunction and vascular diseases. Reduced NO early after traumatic brain injury (TBI) may contribute to hypoperfusion. Currently, methods to quantify ADMA in the cerebrospinal fluid (CSF) have not been fully explored. We aimed to develop and validate a method to determine ADMA in the CSF of a pediatric TBI population and to use this method to assess the effects of (i) TBI and (ii) therapeutic hypothermia (TH) on this mediator. Design, Setting, Patients An ancillary study to a prospective, phase II randomized clinical trial (RCT) of early hypothermia in a tertiary care pediatric intensive care unit for children with TBI admitted to Children's Hospital of Pittsburgh. Interventions None Measurements and Main Results A UPLC-MS/MS method was developed and validated to quantitate ADMA. A total of 56 samples collected over 3 days starting with injury onset were analyzed from the CSF of consented therapeutic hypothermia (n=9) and normothermia (n=10) children. Children undergoing diagnostic lumbar puncture (n=5) were controls. ADMA was present at a quantifiable level in all samples. Mean ADMA levels were significantly increased in normothermic TBI children compared to control (0.19± 0.08 μmol/L and 0.11± 0.02μmol/L respectively, p=0.01), and hypothermic children had significantly reduced mean ADMA levels (0.11 ± 0.05 μmol/L) vs. normothermic (p=0.03) measured on day 3. Patient demographics including age, gender, and NO levels (measured as nitrite and nitrate using liquid chromatography coupled with Griess reaction) did not significantly differ between normothermia and hypothermia groups. Also, NO levels did not correlate with ADMA concentrations. Conclusions ADMA levels were significantly increased in the CSF of TBI children. Early hypothermia attenuated this increase. The implications of attenuated ADMA on NOS activity and regional cerebral blood flow after TBI by TH deserve future attention.