Plasma biogenic amines in head injury

In adult patients with severe traumatic brain injury, does the use of norepinephrine for augmenting cerebral perfusion pressure improve neurological outcome? A systematic review

BACKGROUND AND OBJECTIVE

Despite multiple interventions, mortality due to severe traumatic brain injury (sTBI) within mature Trauma Systems has remained unchanged over the last decade. During this time, the use of vasoactive infusions (commonly norepinephrine) to achieve a target blood pressure and cerebral perfusion pressure (CPP) has been a mainstay of sTBI management. However, evidence suggests that norepinephrine, whilst raising blood pressure, may reduce cerebral oxygenation. This study aimed to review the available evidence that links norepinephrine augmented CPP to clinical outcomes for these patients.

METHODS

A systematic review examining the evidence for norepinephrine augmented CPP in TBI patients was undertaken. Strict inclusion and exclusion criteria were developed for a dedicated literature search of multiple scientific databases. Two dedicated reviewers screened articles, whilst a third dedicated reviewer resolved conflicts.

RESULTS

The systematic review yielded 4,809 articles, of which 1,197 duplicate articles were removed. After abstract/title screening, 45 articles underwent full text review, resulting in the identification of two articles that investigated the effect of norepinephrine administration on clinical outcomes in patients following TBI when compared to other vasopressors. Neither study found a difference in neurological outcome between the vasopressor groups. No articles measured the effect of norepinephrine compared to no vasopressor use on the clinical outcome of patients with sTBI.

CONCLUSIONS

Despite being a mainstay of pharmacological management for hypotension in patients following sTBI, there is minimal clinical evidence supporting the use of norepinephrine in targeting a CPP for either improving neurological outcomes or reducing mortality. Outcomes-based clinical trials exploring the role of brain tissue perfusion and oxygenation monitoring are required to validate any benefit.

COMT Val158Met and cognitive and functional outcomes after traumatic brain injury

There is significant variability in long-term outcomes after traumatic brain injury (TBI), making accurate prognosis difficult. In seeking to enhance understanding of outcomes, this study aimed to investigate whether COMT Val(158)Met allele status was associated with performance on neuropsychological measures of attention and working memory, executive functioning, learning and memory, and speed of information processing in the early rehabilitation phase. The study also aimed to examine whether the COMT polymorphism was associated with longer-term functional outcomes. A total of 223 participants (71.3% male) with moderate-to-severe TBI were recruited as rehabilitation inpatients to participate in a prospective, longitudinal head injury outcome study. The three COMT genotype groups (Val/Val, Val/Met, and Met/Met) were well matched for estimated full-scale IQ, years of education, age at injury, and injury severity. Results showed no significant difference between genotypes on neuropsychological measures (all p>0.05) or functional outcome, as measured by the Glasgow Outcome Scale-Extended (GOS-E), after controlling for age, education, and severity of injury. The presence of frontal lobe pathology was also not associated with cognitive performance. Those with greater injury severity (i.e., longer duration of post-traumatic amnesia) performed more poorly on measures of processing speed and verbal new learning and recall. It was concluded that there was little support for the influence of COMT Val(158)Met on cognitive function, or functional outcome measures, in the acute rehabilitation phase after TBI.

Genetic predictors of response to treatment with citalopram in depression secondary to traumatic brain injury

OBJECTIVES

To determine which serotonergic system-related single nucleotide polymorphisms (SNPs) predicted variation in treatment response to citalopram in depression following a traumatic brain injury (TBI).

METHODS

Ninety (50 M/40 F, aged 39.9, SD = 18.0 years) post-TBI patients with a major depressive episode (MDE) were recruited into a 6-week open-label study of citalopram (20 mg/day). Six functional SNPs in genes related to the serotonergic system were examined: serotonin transporter (5HTTLPR including rs25531), 5HT1A C-(1019)G and 5HT2A T-(102)C, methylene tetrahydrofolate reductase (MTHFR) C-(677)T, brain-derived neurotrophic factor (BDNF) val66met and tryptophan hydroxylase-2 (TPH2) G-(703)T. Regression analyses were performed using the six SNPs as independent variables: Model 1 with response (percentage Hamilton Depression (HAMD) change from baseline to endpoint) as the dependent variable and Model 2 with adverse event index as the dependent variable (Bonferroni corrected p-value < 0.025).

RESULTS

MTHFR and BDNF SNPs predicted greater treatment response (R(2)= 0.098, F = 4.65, p = 0.013). The 5HTTLPR predicted greater occurrence of adverse events (R(2)= 0.069, F = 5.72, p = 0.020).

CONCLUSION

Results suggest that polymorphisms in genes related to the serotonergic system may help predict short-term response to citalopram and tolerability to the medication in patients with MDE following a TBI.

Impact of early administration of sertraline on depressive symptoms in the first year after traumatic brain injury

The potential for sertraline administered in the first 3 months after moderate to severe traumatic brain injury (TBI) to decrease the incidence of depression in the first year after injury was assessed in a double-blinded randomized control trial. Subjects were enrolled an average of 21 days after injury (none >8 weeks) followed by oral administration of placebo (50 subjects) or sertraline 50 mg (49 subjects) for 3 months. Subjects were not depressed at the time of study initiation. Outcome was assessed using the Hamilton Depression Rating Scale (HDRS) and the Depression Scale of the Neurobehavioral Functioning Inventory (NFI). Based on intent-to-treat and efficacy subset analyses, those receiving placebo exhibited significantly greater depressive symptoms than those receiving sertraline during the first 3 months after injury while receiving placebo/drug (10% of placebo group achieving a score of 6 or greater on the HDRS, 0% of the sertraline group; p < 0.023.). There was no significant difference in depressive symptoms during the remainder of the year between the two groups. Sertraline is effective in diminishing depressive symptoms even among those not clinically depressed while the medication is being taken. However, the results do not support the idea that administration early in recovery diminishes the expression of depressive symptoms after the drug is stopped. There is no basis from this study to assume that sertraline administered early in recovery after TBI, when neurotransmitter functioning is often altered, has ongoing effects on the serotonin system after sertraline is discontinued.

Outcome after traumatic brain injury sustained in older adulthood: a one-year longitudinal study

OBJECTIVE

The objective of this study was to explore the effects of traumatic brain injury (TBI) on cognition and functioning in older adults in a one-year longitudinal study.

METHODS

Participants with mild-to-moderate TBI were compared with an age-, gender-, and education-matched healthy comparison group on aspects of cognition. Neuropsychologic tests were administered at one year. Self-reported measures of functioning were completed at baseline, six months, and one year. Informants rated instrumental functioning at one year.

RESULTS

Sixty-nine subjects aged 50 years and over (mean: 67 years; standard deviation: 7.9) and a comparison group of 79 participants were assessed. Patients with TBI had poorer processing speed, verbal memory, language, and executive function; they self-reported more psychologic distress, psychosocial dysfunction, and postconcussive symptoms; and they were rated as more impaired in functioning than the comparison group. TBI of moderate severity accounted for most of the between-group differences.

CONCLUSION

TBI, particularly of moderate severity, led to poorer cognitive and psychosocial functioning one year postinjury among older adults. The clinical significance of this may become more evident with time in this vulnerable population.

Interleukin-16 expression in the peripheral blood and CD8 T lymphocytes after traumatic injury

BACKGROUND

Expressed in several pathologic conditions, interleukin (IL-16) can induce chemotaxis and regulate the activation of CD4-positive leukocytes. This study investigated the expression of IL-16 in trauma patient plasma and peripheral blood leukocytes to determine its involvement in the physiologic response to injury.

METHODS

In this study, 25 consecutive patients requiring trauma team activation and 15 noninjured subjects were evaluated for plasma IL-16 by enzyme-linked immunosorbent assay and peripheral blood leukocyte expression of intracellular cytokine by flow cytometry.

RESULTS

Trauma patient plasma IL-16 was transiently increased after injury in comparison with levels in noninjured control subjects. In patients with worse outcome, both peripheral blood T lymphocyte intracellular IL-16 levels and CD4/CD8 lymphocyte ratios were lower than those for less severely injured patients and control subjects.

CONCLUSION

Posttraumatic changes in IL-16 expression were found to be associated with worse patient outcome, suggesting an innate immune mechanism with a role in regulation of the T lymphocyte response to injury.

The consequences of traumatic brain injury on cerebral blood flow and autoregulation: a review

In this decade, the brain argueably stands as one of the most exciting and challenging organs to study. Exciting in as far as that it remains an area of research vastly unknown and challenging due to the very nature of its anatomical design: the skull provides a formidable barrier and direct observations of intraparenchymal function in vivo are impractical. Moreover, traumatic brain injury (TBI) brings with it added complexities and nuances. The development of irreversible damage following TBI involves a plethora of biochemical events, including impairment of the cerebral vasculature, which render the brain at risk to secondary insults such as ischemia and intracranial hypertension. The present review will focus on alterations in the cerebrovasculature following TBI, and more specifically on changes in cerebral blood flow (CBF), mediators of CBF including local chemical mediators such as K+, pH and adenosine, endothelial mediators such as nitric oxide and neurogenic mediators such as catecholamines, as well as pressure autoregulation. It is emphasized that further research into these mechanisms may help attenuate the prevalence of secondary insults and therefore improve outcome following TBI.

Extracellular release of serotonin following fluid-percussion brain injury in rats

Serotonin has been implicated in the pathobiology of central nervous system trauma. Using microdialysis techniques, we performed measurements of extracellular serotonin release within the traumatized cerebral cortex of rats subjected to moderate fluid-percussion (F-P) brain injury. Twenty-four hours prior to TBI, a F-P interface was positioned parasagitally over the right cerebral cortex. On the second day, fasted rats were anesthetized with 70% nitrous oxide, 1% halothane and 30% oxygen. Under controlled physiological conditions and normothermic brain temperature (37-37.5 degrees C), rats were injured (n = 6) with a F-P pulse ranging from 1.8 to 2.0 atm. Following trauma, brain temperature was maintained for 4 h at 37 degrees C. Sham trauma animals (n = 7) were treated in an identical manner. Brain trauma induced acute elevations in the extracellular levels of serotonin (p < 0.01, ANOVA) compared to sham-operated controls. For example, serotonin levels increased from 18.85 +/- 7.12 pm/mL (mean +/- SD) in baseline samples to 65.78 +/- 11.36 in the first 10 min after trauma. The levels of serotonin remained significantly higher than control for the first 90-min sampling period. In parallel to the increase in serotonin levels after TBI, a significant 71.1% decrease (i.e., 182.29 +/- 30.08 vs 52.75 +/- 16.92) in extracellular 5-hydroxyindoleacetic acid (5-HIAA) levels was observed during the first 10 min after TBI. These data indicate that TBI is followed by a prompt increase in the extracellular levels of serotonin in cortical regions adjacent to the impact site. These neurochemical findings indicate that serotonin may play a significant role in the pathophysiology of TBI.

Creatine kinase isoenzymes in acute brain injury

Brain-type creatine kinase (CK) isoenzyme (CK-BB) was detected in the serum in 13 out of 26 patients with acute brain injury (50%). The peak of CK-BB activity ranged from 5 to 188 U/liter, constituting, on average, 10.5% of the total CK activity. The highest activities were seen in patients with gunshot wounds. High CK-BB activity was associated with poor prognosis, but minimal CK-BB elevations did not have prognostic significance. Heart-type creatine kinase isoenzyme (CK-MB) was detected in the serum in 17 out of 26 patients (65%). The peak activity ranged from 5 to 115 U/liter, constituting, on average, 6.6% of total CK activity. Electrocardiogram taken from 20 patients revealed transient T-wave inversions in the precordial leads in four patients; three of them also showed serum CK-MB activity. Subendocardial hemorrhage was detected at autopsy in three of the five CK-MB-positive patients, but in none of the four CK-MB-negative cases. Present findings suggest that acute brain injury may be secondarily cause myocardial damage.