Mildly Reduced Brain Swelling and Improved Neurological Outcome in Aquaporin-4 Knockout Mice following Controlled Cortical Impact Brain Injury

Brain edema following traumatic brain injury (TBI) is associated with considerable morbidity and mortality. Prior indirect evidence has suggested the involvement of astrocyte water channel aquaporin-4 (AQP4) in the pathogenesis of TBI. Here, focal TBI was produced in wild type (AQP4(+/+)) and knockout (AQP4(-/-)) mice by controlled cortical impact injury (CCI) following craniotomy with dura intact (parameters: velocity 4.5 m/sec, depth 1.7 mm, dwell time 150 msec). AQP4-deficient mice showed a small but significant reduction in injury volume in the first week after CCI, with a small improvement in neurological outcome. Mechanistic studies showed reduced intracranial pressure at 6 h after CCI in AQP4(-/-) mice, compared with AQP4(+/+) control mice (11 vs. 19 mm Hg), with reduced local brain water accumulation as assessed gravimetrically. Transmission electron microscopy showed reduced astrocyte foot-process area in AQP4(-/-) mice at 24 h after CCI, with greater capillary lumen area. Blood-brain barrier disruption assessed by Evans blue dye extravasation was similar in AQP4(+/+) and AQP4(-/-) mice. We conclude that the mildly improved outcome in AQP4(-/-) mice following CCI results from reduced cytotoxic brain water accumulation, though concurrent cytotoxic and vasogenic mechanisms in TBI make the differences small compared to those seen in disorders where cytotoxic edema predominates.

Association of a common genetic variant within ANKK1 with six-month cognitive performance after traumatic brain injury

Genetic association analyses suggest that certain common single nucleotide polymorphisms (SNPs) may adversely impact recovery from traumatic brain injury (TBI). Delineating their causal relationship may aid in development of novel interventions and in identifying patients likely to respond to targeted therapies. We examined the influence of the (C/T) SNP rs1800497 of ANKK1 on post-TBI outcome using data from two prospective multicenter studies: the Citicoline Brain Injury Treatment (COBRIT) trial and Transforming Research and Clinical Knowledge in Traumatic Brain Injury Pilot (TRACK-TBI Pilot). We included patients with ANKK1 genotyping results and cognitive outcomes at six months post-TBI (n = 492: COBRIT n = 272, TRACK-TBI Pilot n = 220). Using the California Verbal Learning Test Second Edition (CVLT-II) Trial 1-5 Standard Score, we found a dose-dependent effect for the T allele, with T/T homozygotes scoring lowest on the CVLT-II Trial 1-5 Standard Score (T/T 45.1, C/T 51.1, C/C 52.1, ANOVA, p = 0.008). Post hoc testing with multiple comparison-correction indicated that T/T patients performed significantly worse than C/T and C/C patients. Similar effects were observed in a test of non-verbal processing (Wechsler Adult Intelligence Scale, Processing Speed Index). Our findings extend those of previous studies reporting a negative relationship of the ANKK1 T allele with cognitive performance after TBI. In this study, we demonstrate the value of pooling shared clinical, biomarker, and outcome variables from two large datasets applying the NIH TBI Common Data Elements. The results have implications for future multicenter investigations to further elucidate the role of ANKK1 in post-TBI outcome.

Measurement of the glial fibrillary acidic protein and its breakdown products GFAP-BDP biomarker for the detection of traumatic brain injury compared to computed tomography and magnetic resonance imaging

Glial fibrillary acidic protein and its breakdown products (GFAP-BDP) are brain-specific proteins released into serum as part of the pathophysiological response after traumatic brain injury (TBI). We performed a multi-center trial to validate and characterize the use of GFAP-BDP levels in the diagnosis of intracranial injury in a broad population of patients with a positive clinical screen for head injury. This multi-center, prospective, cohort study included patients 16-93 years of age presenting to three level 1 trauma centers with suspected TBI (loss of consciousness, post-trauma amnesia, and so on). Serum GFAP-BDP levels were drawn within 24 h and analyzed, in a blinded fashion, using sandwich enzyme-linked immunosorbent assay. The ability of GFAP-BDP to predict intracranial injury on admission computed tomography (CT) as well as delayed magnetic resonance imaging was analyzed by multiple regression and assessed by the area under the receiver operating characteristic curve (AUC). Utility of GFAP-BDP to predict injury and reduce unnecessary CT scans was assessed utilizing decision curve analysis. A total of 215 patients were included, of which 83% suffered mild TBI, 4% moderate, and 12% severe; mean age was 42.1±18 years. Evidence of intracranial injury was present in 51% of the sample (median Rotterdam Score, 2; interquartile range, 2). GFAP-BDP demonstrated very good predictive ability (AUC=0.87) and demonstrated significant discrimination of injury severity (odds ratio, 1.45; 95% confidence interval, 1.29-1.64). Use of GFAP-BDP yielded a net benefit above clinical screening alone and a net reduction in unnecessary scans by 12-30%. Used in conjunction with other clinical information, rapid measurement of GFAP-BDP is useful in establishing or excluding the diagnosis of radiographically apparent intracranial injury throughout the spectrum of TBI. As an adjunct to current screening practices, GFAP-BDP may help avoid unnecessary CT scans without sacrificing sensitivity (Registry: ClinicalTrials.gov Identifier: NCT01565551).

Classification of traumatic brain injury: past, present, and future

Disease classification is central to the practice of medicine; it systematizes clinical knowledge and experience. Classification is essential for diagnosis and effective treatment of human disease. Progress in classifying traumatic brain injury (TBI) for targeted treatment has lagged behind other diseases such as cancer, and has contributed to a lack of progress in the field. Today TBI is most frequently classified as mild, moderate, or severe using the Glasgow Coma Scale (GCS). However, the GCS is symptoms-based and does not allow for targeting of specific pathology. Here we review general schemas for disease classification and how they have evolved over time. We discuss the characteristics of an ideal classification system and the unique challenges inherent to achieving such a system for TBI. Current means of classifying TBI are reviewed, as are the strengths and limitations of these approaches. Generating the data required to modernize TBI classification and to perhaps facilitate a targeted, precision medicine approach to its management will require a highly collaborative international effort. Fortunately these efforts are underway and will benefit from the lessons and tools that have come from other areas of medicine that have already found success with this approach.

Very early administration of progesterone for acute traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. Progesterone has been shown to improve neurologic outcome in multiple experimental models and two early-phase trials involving patients with TBI.

METHODS

We conducted a double-blind, multicenter clinical trial in which patients with severe, moderate-to-severe, or moderate acute TBI (Glasgow Coma Scale score of 4 to 12, on a scale from 3 to 15, with lower scores indicating a lower level of consciousness) were randomly assigned to intravenous progesterone or placebo, with the study treatment initiated within 4 hours after injury and administered for a total of 96 hours. Efficacy was defined as an increase of 10 percentage points in the proportion of patients with a favorable outcome, as determined with the use of the stratified dichotomy of the Extended Glasgow Outcome Scale score at 6 months after injury. Secondary outcomes included mortality and the Disability Rating Scale score.

RESULTS

A total of 882 of the planned sample of 1140 patients underwent randomization before the trial was stopped for futility with respect to the primary outcome. The study groups were similar with regard to baseline characteristics; the median age of the patients was 35 years, 73.7% were men, 15.2% were black, and the mean Injury Severity Score was 24.4 (on a scale from 0 to 75, with higher scores indicating greater severity). The most frequent mechanism of injury was a motor vehicle accident. There was no significant difference between the progesterone group and the placebo group in the proportion of patients with a favorable outcome (relative benefit of progesterone, 0.95; 95% confidence interval [CI], 0.85 to 1.06; P=0.35). Phlebitis or thrombophlebitis was more frequent in the progesterone group than in the placebo group (relative risk, 3.03; CI, 1.96 to 4.66). There were no significant differences in the other prespecified safety outcomes.

CONCLUSIONS

This clinical trial did not show a benefit of progesterone over placebo in the improvement of outcomes in patients with acute TBI. (Funded by the National Institute of Neurological Disorders and Stroke and others; PROTECT III ClinicalTrials.gov number, NCT00822900.).

Outcome prediction after mild and complicated mild traumatic brain injury: external validation of existing models and identification of new predictors using the TRACK-TBI pilot study

Although the majority of patients with mild traumatic brain injury (mTBI) recover completely, some still suffer from disabling ailments at 3 or 6 months. We validated existing prognostic models for mTBI and explored predictors of poor outcome after mTBI. We selected patients with mTBI from TRACK-TBI Pilot, an unselected observational cohort of TBI patients from three centers in the United States. We validated two prognostic models for the Glasgow Outcome Scale Extended (GOS-E) at 6 months after injury. One model was based on the CRASH study data and another from Nijmegen, The Netherlands. Possible predictors of 3- and 6-month GOS-E were analyzed with univariate and multi-variable proportional odds regression models. Of the 386 of 485 patients included in the study (median age, 44 years; interquartile range, 27-58), 75% (n=290) presented with a Glasgow Coma Score (GCS) of 15. In this mTBI population, both previously developed models had a poor performance (area under the receiver operating characteristic curve, 0.49-0.56). In multivariable analyses, the strongest predictors of lower 3- and 6-month GOS-E were older age, pre-existing psychiatric conditions, and lower education. Injury caused by assault, extracranial injuries, and lower GCS were also predictive of lower GOS-E. Existing models for mTBI performed unsatisfactorily. Our study shows that, for mTBI, different predictors are relevant as for moderate and severe TBI. These include age, pre-existing psychiatric conditions, and lower education. Development of a valid prediction model for mTBI patients requires further research efforts.

Reduced brain edema and infarct volume in aquaporin-4 deficient mice after transient focal cerebral ischemia

Aquaporin-4 (AQP4) is a water channel expressed in astrocyte end-feet lining the blood-brain barrier. AQP4 deletion in mice is associated with improved outcomes in global cerebral ischemia produced by transient carotid artery occlusion, and focal cerebral ischemia produced by permanent middle cerebral artery occlusion (MCAO). Here, we investigated the consequences of 1-h transient MCAO produced by intraluminal suture blockade followed by 23 h of reperfusion. In nine AQP4(+/+) and nine AQP4(-/-) mice, infarct volume was significantly reduced by an average of 39 ± 4% at 24h in AQP4(-/-) mice, cerebral hemispheric edema was reduced by 23 ± 3%, and Evans Blue extravasation was reduced by 31 ± 2% (mean ± SEM). Diffusion-weighted magnetic resonance imaging showed greatest reduction in apparent diffusion coefficient around the occlusion site after reperfusion, with remarkably lesser reduction in AQP4(-/-) mice. The reduced infarct volume in AQP4(-/-) mice following transient MCAO supports the potential utility of therapeutic AQP4 inhibition in stroke.

Diffusion tensor imaging for outcome prediction in mild traumatic brain injury: a TRACK-TBI study

We evaluated 3T diffusion tensor imaging (DTI) for white matter injury in 76 adult mild traumatic brain injury (mTBI) patients at the semiacute stage (11.2±3.3 days), employing both whole-brain voxel-wise and region-of-interest (ROI) approaches. The subgroup of 32 patients with any traumatic intracranial lesion on either day-of-injury computed tomography (CT) or semiacute magnetic resonance imaging (MRI) demonstrated reduced fractional anisotropy (FA) in numerous white matter tracts, compared to 50 control subjects. In contrast, 44 CT/MRI-negative mTBI patients demonstrated no significant difference in any DTI parameter, compared to controls. To determine the clinical relevance of DTI, we evaluated correlations between 3- and 6-month outcome and imaging, demographic/socioeconomic, and clinical predictors. Statistically significant univariable predictors of 3-month Glasgow Outcome Scale-Extended (GOS-E) included MRI evidence for contusion (odds ratio [OR] 4.9 per unit decrease in GOS-E; p=0.01), ≥1 ROI with severely reduced FA (OR, 3.9; p=0.005), neuropsychiatric history (OR, 3.3; p=0.02), age (OR, 1.07/year; p=0.002), and years of education (OR, 0.79/year; p=0.01). Significant predictors of 6-month GOS-E included ≥1 ROI with severely reduced FA (OR, 2.7; p=0.048), neuropsychiatric history (OR, 3.7; p=0.01), and years of education (OR, 0.82/year; p=0.03). For the subset of 37 patients lacking neuropsychiatric and substance abuse history, MRI surpassed all other predictors for both 3- and 6-month outcome prediction. This is the first study to compare DTI in individual mTBI patients to conventional imaging, clinical, and demographic/socioeconomic characteristics for outcome prediction. DTI demonstrated utility in an inclusive group of patients with heterogeneous backgrounds, as well as in a subset of patients without neuropsychiatric or substance abuse history.

ED disposition of the Glasgow Coma Scale 13 to 15 traumatic brain injury patient: analysis of the Transforming Research and Clinical Knowledge in TBI study

OBJECTIVE

Mild traumatic brain injury (mTBI) patients are frequently admitted to high levels of care despite limited evidence suggesting benefit. Such decisions may contribute to the significant cost of caring for mTBI patients. Understanding the factors that drive disposition decision making and how disposition is associated with outcomes is necessary for developing an evidence-base supporting disposition decisions. We evaluated factors associated with emergency department triage of mTBI patients to 1 of 3 levels of care: home, inpatient floor, or intensive care unit (ICU).

METHODS

This multicenter, prospective, cohort study included patients with isolated head trauma, a cranial computed tomography as part of routine care, and a Glasgow Coma Scale (GCS) score of 13 to 15. Data analysis was performed using multinomial logistic regression.

RESULTS

Of the 304 patients included, 167 (55%) were discharged home, 76 (25%) were admitted to the inpatient floor, and 61 (20%) were admitted to the ICU. In the multivariable model, admission to the ICU, compared with floor admission, varied by study site, odds ratio (OR) 0.18 (95% confidence interval [CI], 0.06-0.57); antiplatelet/anticoagulation therapy, OR 7.46 (95% CI, 1.79-31.13); skull fracture, OR 7.60 (95% CI, 2.44-23.73); and lower GCS, OR 2.36 (95% CI, 1.05-5.30). No difference in outcome was observed between the 3 levels of care.

CONCLUSION

Clinical characteristics and local practice patterns contribute to mTBI disposition decisions. Level of care was not associated with outcomes. Intracranial hemorrhage, GCS 13 to 14, skull fracture, and current antiplatelet/anticoagulant therapy influenced disposition decisions.

Symptomatology and functional outcome in mild traumatic brain injury: results from the prospective TRACK-TBI study

Mild Traumatic Brain Injury (mTBI), or concussion, is a major public health concern. There is controversy in the literature regarding the true incidence of postconcussion syndrome (PCS), with the constellation of physical, cognitive, emotional, and sleep symptoms after mTBI. In the current study, we report on the incidence and evolution of PCS symptoms and patient outcomes after mTBI at 3, 6, and 12 months in a large, prospective cohort of mTBI patients. Participants were identified as part of the prospective, multi-center Transforming Research and Clinical Knowledge in Traumatic Brain Injury Study. The study population was mTBI patients (Glasgow Coma Scale score of 13-15) presenting to the emergency department, including patients with a negative head computed tomography discharged to home without admission to hospital; 375 mTBI subjects were included in the analysis. At both 6 and 12 months after mTBI, 82% (n=250 of 305 and n=163 of 199, respectively) of patients reported at least one PCS symptom. Further, 44.5 and 40.3% of patients had significantly reduced Satisfaction With Life scores at 6 and 12 months, respectively. At 3 months after injury, 33% of the mTBI subjects were functionally impaired (Glasgow Outcome Scale-Extended score ≤6); 22.4% of the mTBI subjects available for follow-up were still below full functional status at 1 year after injury. The term "mild" continues to be a misnomer for this patient population and underscores the critical need for evolving classification strategies for TBI for targeted therapy.

The impact of previous traumatic brain injury on health and functioning: a TRACK-TBI study

The idea that multiple traumatic brain injury (TBI) can have a cumulative detrimental effect on functioning is widely accepted. Most research supporting this idea comes from athlete samples, and it is not known whether remote history of previous TBI affects functioning after subsequent TBI in community-based samples. This study investigates whether a previous history of TBI with loss of consciousness (LOC) is associated with worse health and functioning in a sample of individuals who require emergency department care for current TBI. Twenty-three percent of the 586 individuals with current TBI in the Transforming Research and Clinical Knowledge in Traumatic Brain Injury study reported having sustained a previous TBI with LOC. Individuals with previous TBI were more likely to be unemployed (χ(2)=17.86; p=0.000), report a variety of chronic medical and psychiatric conditions (4.75≤χ(2)≥24.16; p<0.05), and report substance use (16.35≤χ(2)≥27.57; p<0.01) before the acute injury, compared to those with no previous TBI history. Those with a previous TBI had less-severe acute injuries, but experienced worse outcomes at 6-month follow-up. Results of a series of regression analyses controlling for demographics and acute injury severity indicated that individuals with previous TBI reported more mood symptoms, more postconcussive symptoms, lower life satisfaction, and had slower processing speed and poorer verbal learning, compared to those with no previous TBI history. These findings suggest that history of TBI with LOC may have important implications for health and psychological functioning after TBI in community-based samples.

Acute biomarkers of traumatic brain injury: relationship between plasma levels of ubiquitin C-terminal hydrolase-L1 and glial fibrillary acidic protein

Biomarkers are important for accurate diagnosis of complex disorders such as traumatic brain injury (TBI). For a complex and multifaceted condition such as TBI, it is likely that a single biomarker will not reflect the full spectrum of the response of brain tissue to injury. Ubiquitin C-terminal hydrolase L1 (UCH-L1) and glial fibrillary acidic protein (GFAP) are among of the most widely studied biomarkers for TBI. Because UCH-L1 and GFAP measure distinct molecular events, we hypothesized that analysis of both biomarkers would be superior to analysis of each alone for the diagnosis and prognosis of TBI. Serum levels of UCH-L1 and GFAP were measured in a cohort of 206 patients with TBI enrolled in a multicenter observational study (Transforming Research and Clinical Knowledge in Traumatic Brain Injury [TRACK-TBI]). Levels of the two biomarkers were weakly correlated to each other (r=0.364). Each biomarker in isolation had good sensitivity and sensitivity for discriminating between TBI patients and healthy controls (area under the curve [AUC] 0.87 and 0.91 for UCH-L1 and GFAP, respectively). When biomarkers were combined, superior sensitivity and specificity for diagnosing TBI was obtained (AUC 0.94). Both biomarkers discriminated between TBI patients with intracranial lesions on CT scan and those without such lesions, but GFAP measures were significantly more sensitive and specific (AUC 0.88 vs. 0.71 for UCH-L1). For association with outcome 3 months after injury, neither biomarker had adequate sensitivity and specificity (AUC 0.65-0.74, for GFAP, and 0.59-0.80 for UCH-L1, depending upon Glasgow Outcome Scale Extended [GOS-E] threshold used). Our results support a role for multiple biomarker measurements in TBI research. ( ClinicalTrials.gov Identifier NCT01565551).

Transforming research and clinical knowledge in traumatic brain injury pilot: multicenter implementation of the common data elements for traumatic brain injury

Traumatic brain injury (TBI) is among the leading causes of death and disability worldwide, with enormous negative social and economic impacts. The heterogeneity of TBI combined with the lack of precise outcome measures have been central to the discouraging results from clinical trials. Current approaches to the characterization of disease severity and outcome have not changed in more than three decades. This prospective multicenter observational pilot study aimed to validate the feasibility of implementing the TBI Common Data Elements (TBI-CDEs). A total of 650 subjects who underwent computed tomography (CT) scans in the emergency department within 24 h of injury were enrolled at three level I trauma centers and one rehabilitation center. The TBI-CDE components collected included: 1) demographic, social and clinical data; 2) biospecimens from blood drawn for genetic and proteomic biomarker analyses; 3) neuroimaging studies at 2 weeks using 3T magnetic resonance imaging (MRI); and 4) outcome assessments at 3 and 6 months. We describe how the infrastructure was established for building data repositories for clinical data, plasma biomarkers, genetics, neuroimaging, and multidimensional outcome measures to create a high quality and accessible information commons for TBI research. Risk factors for poor follow-up, TBI-CDE limitations, and implementation strategies are described. Having demonstrated the feasibility of implementing the TBI-CDEs through successful recruitment and multidimensional data collection, we aim to expand to additional study sites. Furthermore, interested researchers will be provided early access to the Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) data set for collaborative opportunities to more precisely characterize TBI and improve the design of future clinical treatment trials. (ClinicalTrials.gov Identifier NCT01565551.).

GFAP-BDP as an acute diagnostic marker in traumatic brain injury: results from the prospective transforming research and clinical knowledge in traumatic brain injury study

Reliable diagnosis of traumatic brain injury (TBI) is a major public health need. Glial fibrillary acidic protein (GFAP) is expressed in the central nervous system, and breakdown products (GFAP-BDP) are released following parenchymal brain injury. Here, we evaluate the diagnostic accuracy of elevated levels of plasma GFAP-BDP in TBI. Participants were identified as part of the prospective Transforming Research And Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) Study. Acute plasma samples (<24 h post-injury) were collected from patients presenting with brain injury who had CT imaging. The ability of GFAP-BDP level to discriminate patients with demonstrable traumatic lesions on CT, and with failure to return to pre-injury baseline at 6 months, was evaluated by the area under the receiver operating characteristic curve (AUC). Of the 215 patients included for analysis, 83% had mild, 4% had moderate, and 13% had severe TBI; 54% had acute traumatic lesions on CT. The ability of GFAP-BDP level to discriminate patients with traumatic lesions on CT as evaluated by AUC was 0.88 (95% confidence interval [CI], 0.84-0.93). The optimal cutoff of 0.68 ng/mL for plasma GFAP-BDP level was associated with a 21.61 odds ratio for traumatic findings on head CT. Discriminatory ability of unfavorable 6 month outcome was lower, AUC 0.65 (95% CI, 0.55-0.74), with a 2.07 odds ratio. GFAP-BDP levels reliably distinguish the presence and severity of CT scan findings in TBI patients. Although these findings confirm and extend prior studies, a larger prospective trial is still needed to validate the use of GFAP-BDP as a routine diagnostic biomarker for patient care and clinical research. The term "mild" continues to be a misnomer for this patient population, and underscores the need for evolving classification strategies for TBI targeted therapy. (ClinicalTrials.gov number NCT01565551; NIH Grant 1RC2 NS069409).

Combined SCI and TBI: recovery of forelimb function after unilateral cervical spinal cord injury (SCI) is retarded by contralateral traumatic brain injury (TBI), and ipsilateral TBI balances the effects of SCI on paw placement

A significant proportion (estimates range from 16 to 74%) of patients with spinal cord injury (SCI) have concomitant traumatic brain injury (TBI), and the combination often produces difficulties in planning and implementing rehabilitation strategies and drug therapies. For example, many of the drugs used to treat SCI may interfere with cognitive rehabilitation, and conversely drugs that are used to control seizures in TBI patients may undermine locomotor recovery after SCI. The current paper presents an experimental animal model for combined SCI and TBI to help drive mechanistic studies of dual diagnosis. Rats received a unilateral SCI (75 kdyn) at C5 vertebral level, a unilateral TBI (2.0 mm depth, 4.0 m/s velocity impact on the forelimb sensori-motor cortex), or both SCI+TBI. TBI was placed either contralateral or ipsilateral to the SCI. Behavioral recovery was examined using paw placement in a cylinder, grooming, open field locomotion, and the IBB cereal eating test. Over 6weeks, in the paw placement test, SCI+contralateral TBI produced a profound deficit that failed to recover, but SCI+ipsilateral TBI increased the relative use of the paw on the SCI side. In the grooming test, SCI+contralateral TBI produced worse recovery than either lesion alone even though contralateral TBI alone produced no observable deficit. In the IBB forelimb test, SCI+contralateral TBI revealed a severe deficit that recovered in 3 weeks. For open field locomotion, SCI alone or in combination with TBI resulted in an initial deficit that recovered in 2 weeks. Thus, TBI and SCI affected forelimb function differently depending upon the test, reflecting different neural substrates underlying, for example, exploratory paw placement and stereotyped grooming. Concurrent SCI and TBI had significantly different effects on outcomes and recovery, depending upon laterality of the two lesions. Recovery of function after cervical SCI was retarded by the addition of a moderate TBI in the contralateral hemisphere in all tests, but forepaw placements were relatively increased by an ipsilateral TBI relative to SCI alone, perhaps due to the dual competing injuries influencing the use of both forelimbs. These findings emphasize the complexity of recovery from combined CNS injuries, and the possible role of plasticity and laterality in rehabilitation, and provide a start towards a useful preclinical model for evaluating effective therapies for combine SCI and TBI.

Altering physiological networks using drugs: steps towards personalized physiology

Background

The rise of personalized medicine has reminded us that each patient must be treated as an individual. One factor in making treatment decisions is the physiological state of each patient, but definitions of relevant states and methods to visualize state-related physiologic changes are scarce. We constructed correlation networks from physiologic data to demonstrate changes associated with pressor use in the intensive care unit.

Methods

We collected 29 physiological variables at one-minute intervals from nineteen trauma patients in the intensive care unit of an academic hospital and grouped each minute of data as receiving or not receiving pressors. For each group we constructed Spearman correlation networks of pairs of physiologic variables. To visualize drug-associated changes we split the networks into three components: an unchanging network, a network of connections with changing correlation sign, and a network of connections only present in one group.

Results

Out of a possible 406 connections between the 29 physiological measures, 64, 39, and 48 were present in each of the three component networks. The static network confirms expected physiological relationships while the network of associations with changed correlation sign suggests putative changes due to the drugs. The network of associations present only with pressors suggests new relationships that could be worthy of study.

Conclusions

We demonstrated that visualizing physiological relationships using correlation networks provides insight into underlying physiologic states while also showing that many of these relationships change when the state is defined by the presence of drugs. This method applied to targeted experiments could change the way critical care patients are monitored and treated.

Resting state magnetoencephalography functional connectivity in traumatic brain injury

OBJECT

Traumatic brain injury (TBI) is one of the leading causes of morbidity worldwide. One mechanism by which blunt head trauma may disrupt normal cognition and behavior is through alteration of functional connectivity between brain regions. In this pilot study, the authors applied a rapid automated resting state magnetoencephalography (MEG) imaging technique suitable for routine clinical use to test the hypothesis that there is decreased functional connectivity in patients with TBI compared with matched controls, even in cases of mild TBI. Furthermore, they posit that these abnormal reductions in MEG functional connectivity can be detected even in TBI patients without specific evidence of traumatic lesions on 3-T MR images. Finally, they hypothesize that the reductions of functional connectivity can improve over time across serial MEG scans during recovery from TBI.

METHODS

Magnetoencephalography maps of functional connectivity in the alpha (8- to 12-Hz) band from 21 patients who sustained a TBI were compared with those from 18 age- and sex-matched controls. Regions of altered functional connectivity in each patient were detected in automated fashion through atlas-based registration to the control database. The extent of reduced functional connectivity in the patient group was tested for correlations with clinical characteristics of the injury as well as with findings on 3-T MRI. Finally, the authors compared initial connectivity maps with 2-year follow-up functional connectivity in a subgroup of 5 patients with TBI.

RESULTS

Fourteen male and 7 female patients (17-53 years old, median 29 years) were enrolled. By Glasgow Coma Scale (GCS) criteria, 11 patients had mild, 1 had moderate, and 3 had severe TBI, and 6 had no GCS score recorded. On 3-T MRI, 16 patients had abnormal findings attributable to the trauma and 5 had findings in the normal range. As a group, the patients with TBI had significantly lower functional connectivity than controls (p < 0.01). Three of the 5 patients with normal findings on 3-T MRI showed regions of abnormally reduced MEG functional connectivity. No significant correlations were seen between extent of functional disconnection and injury severity or posttraumatic symptoms (p > 0.05). In the subgroup undergoing 2-year follow-up, the second MEG scan demonstrated a significantly lower percentage of voxels with decreased connectivity (p < 0.05) than the initial MEG scan.

CONCLUSIONS

A rapid automated resting-state MEG imaging technique demonstrates abnormally decreased functional connectivity that may persist for years after TBI, including cases classified as "mild" by GCS criteria. Disrupted MEG connectivity can be detected even in some patients with normal findings on 3-T MRI. Analysis of follow-up MEG scans in a subgroup of patients shows that, over time, the abnormally reduced connectivity can improve, suggesting neuroplasticity during the recovery from TBI. Resting state MEG deserves further investigation as a prognostic and predictive biomarker for TBI.

Magnetic resonance imaging improves 3-month outcome prediction in mild traumatic brain injury

OBJECTIVE

To determine the clinical relevance, if any, of traumatic intracranial findings on early head computed tomography (CT) and brain magnetic resonance imaging (MRI) to 3-month outcome in mild traumatic brain injury (MTBI).

METHODS

One hundred thirty-five MTBI patients evaluated for acute head injury in emergency departments of 3 LEVEL I trauma centers were enrolled prospectively. In addition to admission head CT, early brain MRI was performed 12 ± 3.9 days after injury. Univariate and multivariate logistic regression were used to assess for demographic, clinical, socioeconomic, CT, and MRI features that were predictive of Extended Glasgow Outcome Scale (GOS-E) at 3 months postinjury.

RESULTS

Twenty-seven percent of MTBI patients with normal admission head CT had abnormal early brain MRI. CT evidence of subarachnoid hemorrhage was associated with a multivariate odds ratio of 3.5 (p = 0.01) for poorer 3-month outcome, after adjusting for demographic, clinical, and socioeconomic factors. One or more brain contusions on MRI, and ≥4 foci of hemorrhagic axonal injury on MRI, were each independently associated with poorer 3-month outcome, with multivariate odds ratios of 4.5 (p = 0.01) and 3.2 (p = 0.03), respectively, after adjusting for head CT findings and demographic, clinical, and socioeconomic factors.

INTERPRETATION

In this prospective multicenter observational study, the clinical relevance of abnormal findings on early brain imaging after MTBI is demonstrated. The addition of early CT and MRI markers to a prognostic model based on previously known demographic, clinical, and socioeconomic predictors resulted in a >2-fold increase in the explained variance in 3-month GOS-E.

A longitudinal MRI study of traumatic axonal injury in patients with moderate and severe traumatic brain injury

OBJECTIVE

To study the evolution of traumatic axonal injury (TAI) detected by structural MRI in patients with moderate and severe traumatic brain injury (TBI) during the first year and relate findings to outcome.

METHODS

58 patients with TBI (Glasgow Coma Scale score 3-13) were examined with MRI at a median of 7 days, 3 months and 12 months post injury. TAI lesions were evaluated blinded and categorised into three stages based on location: hemispheres, corpus callosum and brainstem. Lesions in T2* weighted gradient echo (GRE), fluid attenuated inversion recovery (FLAIR) and diffusion weighted imaging (DWI) were counted and FLAIR lesion volumes were estimated. Inter-rater reliability score was calculated. Outcome was assessed 12 months post injury using the Glasgow Outcome Scale Extended.

RESULTS

In the initial MRI, 31% had brainstem lesions compared with 17% at 3 months (p=0.008). In the FLAIR sequences, number and volumes of lesions were reduced from early to 3 months (p<0.001). In T2*GRE sequences, the number of lesions persisted at 3 months but was reduced at 12 months (p=0.007). The number of lesions in DWI and volume of FLAIR lesions on early MRI predicted worse clinical outcome in adjusted analyses (p<0.05).

CONCLUSION

This is the first study to demonstrate and quantify attenuation of non-haemorrhagic TAI lesions on structural MRI during the first 3 months after TBI; most importantly, the disappearance of brainstem lesions. Haemorrhagic TAI lesions attenuate first after 3 months. Only early MRI findings predicted clinical outcome after adjustment for other prognostic factors. Hence valuable clinical information may be missed if MRI is performed too late after TBI.

Early management of severe traumatic brain injury

Severe traumatic brain injury remains a major health-care problem worldwide. Although major progress has been made in understanding of the pathophysiology of this injury, this has not yet led to substantial improvements in outcome. In this report, we address present knowledge and its limitations, research innovations, and clinical implications. Improved outcomes for patients with severe traumatic brain injury could result from progress in pharmacological and other treatments, neural repair and regeneration, optimisation of surgical indications and techniques, and combination and individually targeted treatments. Expanded classification of traumatic brain injury and innovations in research design will underpin these advances. We are optimistic that further gains in outcome for patients with severe traumatic brain injury will be achieved in the next decade.

Coagulopathy after traumatic brain injury

Traumatic brain injury has long been associated with abnormal coagulation parameters, but the exact mechanisms underlying this phenomenon are poorly understood. Coagulopathy after traumatic brain injury includes hypercoagulable and hypocoagulable states that can lead to secondary injury by either the induction of microthrombosis or the progression of hemorrhagic brain lesions. Multiple hypotheses have been proposed to explain this phenomenon, including the release of tissue factor, disseminated intravascular coagulation, hyperfibrinolysis, hypoperfusion with protein C activation, and platelet dysfunction. The diagnosis and management of these complex patients are difficult given the lack of understanding of the underlying mechanisms. The goal of this review is to summarize the current knowledge regarding the mechanisms of coagulopathy after blunt traumatic brain injury. The current and emerging diagnostic tools, radiological findings, treatment options, and prognosis are discussed.

The effect of decompressive hemicraniectomy on brain temperature after severe brain injury

BACKGROUND

Animal studies have shown that even a small temperature elevation of 1°C can cause detrimental effects after brain injury. Since the skull acts as a potential thermal insulator, we hypothesized that decompressive hemicraniectomy facilitates surface cooling and lowers brain temperature.

METHODS

Forty-eight patients with severe brain injury (TBI = 38, ICH = 10) with continuous brain temperature monitoring were retrospectively studied and grouped into "hemicraniectomy" (n = 20) or "no hemicraniectomy" (n = 28) group. The paired measurements of core body (T Core) and brain (T Br) temperature were recorded at 1-min intervals over 12 ± 7 days. As a surrogate measure for the extent of surface heat loss from the brain, ∆T Core-Br was calculated as the difference between T Core and T Br with each recording. In order to accommodate within-patient temperature correlations, mixed-model regression was used to assess the differences in ∆T Core-Br between those with and without hemicraniectomy, adjusted for core body temperature and diagnosis.

RESULTS

A total of 295,883 temperature data pairs were collected (median [IQR] per patient: 5047 [3125-8457]). Baseline characteristics were similar for age, sex, diagnosis, incidence of sepsis, Glasgow Coma Scale score, ICU mortality, and ICU length of stay between the two groups. The mean difference in ∆T Core-Br was 1.29 ± 0.87°C for patients with and 0.80 ± 0.86°C for patients without hemicraniectomy (P < 0.0001). In mixed-model regression, accounting for temperature correlations within patients, hemicraniectomy and higher T Core were associated with greater ∆T Core-Br (hemicraniectomy: estimated effect = 0.60, P = 0.003; T Core: estimated effect = 0.21, P < 0.0001).

CONCLUSIONS

Hemicraniectomy is associated with modestly but significantly lower brain temperature relative to core body temperature.

Re-orientation of clinical research in traumatic brain injury: report of an international workshop on comparative effectiveness research

During the National Neurotrauma Symposium 2010, the DG Research of the European Commission and the National Institutes of Health/National Institute of Neurological Disorders and Stroke (NIH/NINDS) organized a workshop on comparative effectiveness research (CER) in traumatic brain injury (TBI). This workshop reviewed existing approaches to improve outcomes of TBI patients. It had two main outcomes: First, it initiated a process of re-orientation of clinical research in TBI. Second, it provided ideas for a potential collaboration between the European Commission and the NIH/NINDS to stimulate research in TBI. Advances in provision of care for TBI patients have resulted from observational studies, guideline development, and meta-analyses of individual patient data. In contrast, randomized controlled trials have not led to any identifiable major advances. Rigorous protocols and tightly selected populations constrain generalizability. The workshop addressed additional research approaches, summarized the greatest unmet needs, and highlighted priorities for future research. The collection of high-quality clinical databases, associated with systems biology and CER, offers substantial opportunities. Systems biology aims to identify multiple factors contributing to a disease and addresses complex interactions. Effectiveness research aims to measure benefits and risks of systems of care and interventions in ordinary settings and broader populations. These approaches have great potential for TBI research. Although not new, they still need to be introduced to and accepted by TBI researchers as instruments for clinical research. As with therapeutic targets in individual patient management, so it is with research tools: one size does not fit all.

Quantitative CT improves outcome prediction in acute traumatic brain injury

The admission noncontrast head computed tomography (CT) scan has been demonstrated to be one of several key early clinical and imaging features in the challenging problem of prediction of long-term outcome after acute traumatic brain injury (TBI). In this study, we employ two novel approaches to the problem of imaging classification and outcome prediction in acute TBI. First, we employ the novel technique of quantitative CT (qCT) image analysis to provide more objective, reproducible measures of the abnormal features of the admission head CT in acute TBI. We show that the incorporation of quantitative, rather than qualitative, CT features results in a significant improvement in prediction of the 6-month Extended Glasgow Outcome Scale (GOS-E) score over a wide spectrum of injury severity. Second, we employ principal components analysis (PCA) to demonstrate the interdependence of certain predictive variables. Relatively few prior studies of outcome prediction in acute TBI have used a multivariate approach that explicitly takes into account the potential covariance among clinical and CT predictive variables. We demonstrate that several predictors, including midline shift, cistern effacement, subdural hematoma volume, and Glasgow Coma Scale (GCS) score are related to one another. Rather than being independent features, their importance may be related to their status as surrogate measures of a more fundamental underlying clinical feature, such as the severity of intracranial mass effect. We believe that objective computational tools and data-driven analytical methods hold great promise for neurotrauma research, and may ultimately have a role in image analysis for clinical care.

Temporizing treatment of hyperacute subdural hemorrhage by subdural evacuation port system placement

An acute subdural hematoma (SDH) requiring surgical intervention is treated with craniotomy or craniectomy, in part because it is generally accepted that coagulated blood present in the acute phase cannot be adequately evacuated by less-invasive means such as bur hole drainage. However, a hyperacute SDH in the first few hours after trauma can have mixed-density components on CT scans that are thought to represent subdural blood that is not yet fully coagulated.

The authors report a case in which a hyperacute SDH in a patient receiving antiplatelet therapy was treated with the novel technique of temporizing subdural evacuation port system (SEPS) placement. Placement of an SEPS in the intensive care unit allowed for rapid surgical treatment of the patient's elevated intracranial pressure (ICP) by drainage of 70 ml of fresh subdural blood. After initial SEPS-induced stabilization, the patient underwent operative treatment of the SDH by craniotomy. The combined approach of emergency SEPS placement followed by craniotomy resulted in a dramatic recovery, with improvement from coma and extensor posturing to a normal status on neurological evaluation 5 weeks later. In appropriately selected cases, patients with a hyperacute SDH may benefit from SEPS placement to quickly treat elevated ICP, as a bridge to definitive surgical treatment by craniotomy.

Marked reduction in wound complication rates following decompressive hemicraniectomy with an improved operative closure technique

Although decompressive hemicraniectomy with dural expansion and bone flap removal is a potentially life-saving procedure, concerns remain regarding the morbidity associated with this approach. We and others have noted the high rate of wound complications resulting from this technique, often associated with cerebrospinal fluid (CSF) absorption problems. Here, we present our experience with an improved technique for wound closure after unilateral decompressive hemicraniectomy with a wide cruciate durotomy. Data for all patients who underwent a decompressive hemicraniectomy at our institution from October 2005 to October 2009 were gathered prospectively. Starting in mid 2008, we adopted an alternate approach to operative wound closure, which involved skin closure with a running Monocryl absorbable stitch, and prolonged subgaleal drainage. We compared the rates of wound complication using this approach with those obtained with earlier conventional closure techniques. Over a 1year period, we dramatically reduced the rate of wound complications in patients undergoing hemicraniectomy at our hospital using this new (Monocryl technique, 0% (n=29) compared to other techniques, 35% (n=98), chi-squared [χ(2)] p<0.001). Patients closed using our new technique experienced markedly reduced rates of wound infection (p<0.01), and CSF leak (p<0.05), compared to other, more standard, techniques. Thus, attention to closure of hemicraniectomy wounds can markedly reduce the rate of wound complications, thus improving the risk-to-benefit ratio of this procedure.

Mechanisms of primary blast-induced traumatic brain injury: insights from shock-wave research

Traumatic brain injury caused by explosive or blast events is traditionally divided into four phases: primary, secondary, tertiary, and quaternary blast injury. These phases of blast-induced traumatic brain injury (bTBI) are biomechanically distinct and can be modeled in both in vivo and in vitro systems. The primary bTBI injury phase represents the response of brain tissue to the initial blast wave. Among the four phases of bTBI, there is a remarkable paucity of information about the cause of primary bTBI. On the other hand, 30 years of research on the medical application of shockwaves (SW) has given us insight into the mechanisms of tissue and cellular damage in bTBI, including both air-mediated and underwater SW sources. From a basic physics perspective, the typical blast wave consists of a lead SW followed by supersonic flow. The resultant tissue injury includes several features observed in bTBI, such as hemorrhage, edema, pseudoaneurysm formation, vasoconstriction, and induction of apoptosis. These are well-described pathological findings within the SW literature. Acoustic impedance mismatch, penetration of tissue by shock/bubble interaction, geometry of the skull, shear stress, tensile stress, and subsequent cavitation formation, are all important factors in determining the extent of SW-induced tissue and cellular injury. Herein we describe the requirements for the adequate experimental set-up when investigating blast-induced tissue and cellular injury; review SW physics, research, and the importance of engineering validation (visualization/pressure measurement/numerical simulation); and, based upon our findings of SW-induced injury, discuss the potential underlying mechanisms of primary bTBI.

Dynamic, multi-level network models of clinical trials

While networks models have often been applied to complex biological systems, they are increasingly being implemented to investigate clinical questions. Clinical trials have been studied extensively by traditional statistical methods but never, to our knowledge, using networks. We obtained data for 6,847 clinical trials from five "Nervous System Diseases" (NSD) and five "Behaviors and Mental Disorders" (BMD) from the clinicaltrials.gov registry. We constructed networks of diseases and interventions for visualization and analysis using Cytoscape software. To standardize nomenclature and enable multi-level annotation, we used MeSH and UMLS terms. We then constructed separate BMD and NSD networks to study dynamics over time. To assess how topology features related to clinical significance, we constructed a sub-network of Multiple Sclerosis and Alzheimer's trials and identified which trials had been published in high-profile medical journals. We found that the BMD network has evolved into a large, decentralized topology and does not distinctly reflect the five diseases by which it was defined, while the NSD network does, though other diseases and sub-phenotypes have emerged as areas of research. We also found that high-profile trials have distinctive network characteristics. Future work is needed to address mathematical questions such as scale-dependence of network features, clinical questions such as trial design optimization, and methodological questions such as data quality improvement.

Common data elements for traumatic brain injury: recommendations from the biospecimens and biomarkers working group

Recent advances in genomics, proteomics, and biotechnology have provided unprecedented opportunities for translational research and personalized medicine. Human biospecimens and biofluids represent an important resource from which molecular data can be generated to detect and classify injury and to identify molecular mechanisms and therapeutic targets. To date, there has been considerable variability in biospecimen and biofluid collection, storage, and processing in traumatic brain injury (TBI) studies. To realize the full potential of this important resource, standardization and adoption of best practice guidelines are required to insure the quality and consistency of these specimens. The aim of the Biospecimens and Biomarkers Working Group was to provide recommendations for core data elements for TBI research and develop best practice guidelines to standardize the quality and accessibility of these specimens. Consensus recommendations were developed through interactions with focus groups and input from stakeholders participating in the interagency workshop on Standardization of Data Collection in TBI and Psychological Health held in Washington, DC, in March 2009. With the adoption of these standards and best practices, future investigators will be able to obtain data across multiple studies with reduced costs and effort and accelerate the progress of genomic, proteomic, and metabolomic research in TBI.

Hemicraniectomy: a new model for human electrophysiology with high spatio-temporal resolution

Human electrophysiological research is generally restricted to scalp EEG, magneto-encephalography, and intracranial electrophysiology. Here we examine a unique patient cohort that has undergone decompressive hemicraniectomy, a surgical procedure wherein a portion of the calvaria is removed for several months during which time the scalp overlies the brain without intervening bone. We quantify the differences in signals between electrodes over areas with no underlying skull and scalp EEG electrodes over the intact skull in the same subjects. Signals over the hemicraniectomy have enhanced amplitude and greater task-related power at higher frequencies (60-115 Hz) compared with signals over skull. We also provide evidence of a metric for trial-by-trial EMG/EEG coupling that is effective over the hemicraniectomy but not intact skull at frequencies >60 Hz. Taken together, these results provide evidence that the hemicraniectomy model provides a means for studying neural dynamics in humans with enhanced spatial and temporal resolution.

Incorporating a parenchymal thermal diffusion cerebral blood flow probe in bedside assessment of cerebral autoregulation and vasoreactivity in patients with severe traumatic brain injury

OBJECT

Cerebral autoregulation may be altered after traumatic brain injury (TBI). Recent evidence suggests that patients' autoregulatory status following severe TBI may influence cerebral perfusion pressure management. The authors evaluated the utility of incorporating a recently upgraded parenchymal thermal diffusion probe for the measurement of cerebral blood flow (CBF) in the neurointensive care unit for assessing cerebral autoregulation and vasoreactivity at bedside.

METHODS

The authors evaluated 20 patients with severe TBI admitted to San Francisco General Hospital who underwent advanced neuromonitoring. Patients had a parenchymal thermal diffusion probe placed for continuous bedside monitoring of local CBF ((loc)CBF) in addition to the standard intracranial pressure and brain tissue oxygen tension (P(bt)O(2)) monitoring. The CBF probes were placed in the white matter using a separate cranial bolt. A pressure challenge, whereby mean arterial pressure (MAP) was increased by about 10 mm Hg, was performed in all patients to assess autoregulation. Cerebral CO(2) vasoreactivity was assessed with a hyperventilation challenge. Local cerebral vascular resistance ((loc)CVR) was calculated by dividing cerebral perfusion pressure by (loc)CBF. Local cerebral vascular resistance normalized to baseline ((loc)CVR(normalized)) was also calculated for the MAP and hyperventilation challenges.

RESULTS

In all cases, bedside measurement of (loc)CBF using a cranial bolt in patients with severe TBI resulted in correct placement in the white matter with a low rate of complications. Mean (loc)CBF decreased substantially with hyperventilation challenge (-7 ± 8 ml/100 g/min, p = 0.0002) and increased slightly with MAP challenge (1 ± 7 ml/100 g/min, p = 0.17). Measurements of (loc)CBF following MAP and hyperventilation challenges can be used to calculate (loc)CVR. In 83% of cases, (loc)CVR increased during a hyperventilation challenge (mean change +3.5 ± 3.8 mm Hg/ml/100 g/min, p = 0.0002), indicating preserved cerebral CO(2) vasoreactivity. In contrast, we observed a more variable response of (loc)CVR to MAP challenge, with increased (loc)CVR in only 53% of cases during a MAP challenge (mean change -0.17 ± 3.9 mm Hg/ml/100 g/min, p = 0.64) indicating that in many cases autoregulation was impaired following severe TBI.

CONCLUSIONS

Use of the Hemedex thermal diffusion probe appears to be a safe and feasible method that enables continuous monitoring of CBF at the bedside. Cerebral autoregulation and CO(2) vasoreactivity can be assessed in patients with severe TBI using the CBF probe by calculating (loc)CVR in response to MAP and hyperventilation challenges. Determining whether CVR increases or decreases with a MAP challenge ((loc)CVR(normalized)) may be a simple provocative test to determine patients' autoregulatory status following severe TBI and helping to optimize CPP management.

Interobserver variability in the assessment of CT imaging features of traumatic brain injury

The goal of our study was to determine the interobserver variability between observers with different backgrounds and experience when interpreting computed tomography (CT) imaging features of traumatic brain injury (TBI). We retrospectively identified a consecutive series of 50 adult patients admitted at our institution with a suspicion of TBI, and displaying a Glasgow Coma Scale score < or =12. Noncontrast CT (NCT) studies were anonymized and sent to five reviewers with different backgrounds and levels of experience, who independently reviewed each NCT scan. Each reviewer assessed multiple CT imaging features of TBI and assigned every NCT scan a Marshall and a Rotterdam grading score. The interobserver agreement and coefficient of variation were calculated for individual CT imaging features of TBI as well as for the two scores. Our results indicated that the imaging review by both neuroradiologists and neurosurgeons were consistent with each other. The kappa coefficient of agreement for all CT characteristics showed no significant difference in interpretation between the neurosurgeons and neuroradiologists. The average Bland and Altman coefficients of variation for the Marshall and Rotterdam classification systems were 12.7% and 21.9%, respectively, which indicates acceptable agreement among all five reviewers. In conclusion, there is good interobserver reproducibility between neuroradiologists and neurosurgeons in the interpretation of CT imaging features of TBI and calculation of Marshall and Rotterdam scores.

Identification of complex metabolic states in critically injured patients using bioinformatic cluster analysis

Introduction

Advances in technology have made extensive monitoring of patient physiology the standard of care in intensive care units (ICUs). While many systems exist to compile these data, there has been no systematic multivariate analysis and categorization across patient physiological data. The sheer volume and complexity of these data make pattern recognition or identification of patient state difficult. Hierarchical cluster analysis allows visualization of high dimensional data and enables pattern recognition and identification of physiologic patient states. We hypothesized that processing of multivariate data using hierarchical clustering techniques would allow identification of otherwise hidden patient physiologic patterns that would be predictive of outcome.

Methods

Multivariate physiologic and ventilator data were collected continuously using a multimodal bioinformatics system in the surgical ICU at San Francisco General Hospital. These data were incorporated with non-continuous data and stored on a server in the ICU. A hierarchical clustering algorithm grouped each minute of data into 1 of 10 clusters. Clusters were correlated with outcome measures including incidence of infection, multiple organ failure (MOF), and mortality.

Results

We identified 10 clusters, which we defined as distinct patient states. While patients transitioned between states, they spent significant amounts of time in each. Clusters were enriched for our outcome measures: 2 of the 10 states were enriched for infection, 6 of 10 were enriched for MOF, and 3 of 10 were enriched for death. Further analysis of correlations between pairs of variables within each cluster reveals significant differences in physiology between clusters.

Conclusions

Here we show for the first time the feasibility of clustering physiological measurements to identify clinically relevant patient states after trauma. These results demonstrate that hierarchical clustering techniques can be useful for visualizing complex multivariate data and may provide new insights for the care of critically injured patients.

Clinical trials in traumatic brain injury: past experience and current developments

In this article, we review past and current experience in clinical trials of traumatic brain injuries (TBIs), we discuss limitations and challenges, and we summarize current directions. The focus is on severe and moderate TBIs. A systematic literature search of the years from 1980 to 2009 revealed 27 large phase III trials in TBI; we were aware of a further 6 unpublished trials. Analysis of these 33 trials yielded interesting observations: There was a peak incidence of trial initiations that occurred in the mid-1990s with a sharp decline during the period from 2000 to 2004. Most trials that reported a significant treatment effect were studies on a therapeutic strategy (e.g., decompressive craniectomy, hypothermia), and these were single-center studies. Increasingly, studies have been shifting toward the Far East. The currently existing trial registries permit insight into ongoing or recently conducted trials. Compared with the past decade, the number of studies on neuroprotective agents taken forward into efficacy-oriented studies is low. In contrast, the number of studies on therapeutic strategies appears to be increasing again. The disappointing results in trials on neuroprotective agents in TBI have led to a critical reappraisal of clinical trial methodology. This has resulted in recommendations for preclinical workup and has triggered extensive analysis on approaches to improve the design and analysis of clinical trials in TBI. An interagency initiative toward standardization on selection and coding of data elements across the broad spectrum of TBI is ongoing, and will facilitate comparison of research findings across studies and encourage high-quality meta-analysis of individual patient data in the future.

Infection in the intensive care unit alters physiological networks

BACKGROUND

Physicians use clinical and physiological data to treat patients every day, and it is essential for treating a patient appropriately. However, medical sources of clinical physiological data are only now starting to find use in bioinformatics research.

RESULTS

We collected 29 types of physiological and clinical data on a minute-by-minute basis from trauma patients in the intensive care unit along with whether they contracted an infection during their stay. Dividing the patients into two groups based on this criterion, we determined that the correlational network amongst pairs of physiological variables changes based on whether the patient contracted an infection.

CONCLUSION

Examining the variable pairs with the largest change in correlation across groups reveals potential changes in the way our treatments affect the patient's physiology and in how our bodies react to physiological insults. These findings highlight the usefulness of physiological informatics and suggest new relationships to study while also validating previously reported relationships.

Effects of white, grey, and pia mater properties on tissue level stresses and strains in the compressed spinal cord

Recent demographics demonstrate an increase in the number of elderly spinal cord injury patients, motivating the desire for a better understanding of age effects on injury susceptibility. Knowing that age and disease affect neurological tissue, there is a need to better understand the sensitivity of spinal cord injury mechanics to variations in tissue behavior. To address this issue, a plane-strain, geometrically nonlinear, finite element model of a section of a generic human thoracic spinal cord was constructed to model the response to dorsal compression. The material models and stiffness responses for the grey and white matter and pia mater were varied across a range of reported values to observe the sensitivity of model outcomes to the assigned properties. Outcome measures were evaluated for percent change in magnitude and alterations in spatial distribution. In general, principal stresses (114-244% change) and pressure (75-119% change) were the outcomes most sensitive to material variation. Strain outcome measures were less sensitive (7-27% change) than stresses (74-244% change) to variations in material tangent modulus. The pia mater characteristics had limited (<4% change) effects on outcomes. Using linear elastic models to represent non-linear behavior had variable effects on outcome measures, and resulted in highly concentrated areas of elevated stresses and strains. Pressure measurements in both the grey and white matter were particularly sensitive to white matter properties, suggesting that degenerative changes in white matter may influence perfusion in a compressed spinal cord. Our results suggest that the mechanics of spinal cord compression are likely to be affected by changes in tissue resulting from aging and disease, indicating a need to study the biomechanical aspects of spinal cord injury in these specific populations.

Introduction: Decompressive craniectomy for trauma and cerebrovascular disease

Elevated intracranial pressure is one of the most common causes of death and disability following severe traumatic brain injury and ischemic stroke. Unfortunately, there have been no new medical treatments for cerebral edema and elevated intracranial pressure in more than 80 years. Decompressive craniectomy may be an appropriate surgical option in the face of elevated intracranial pressure that is refractory to medical treatment. When performed correctly, this procedure can reduce intracranial pressure and prevent cerebral herniation and death. The last decade has seen a renewed interest in the use of decompressive craniectomy, but many questions remain regarding patient selection, timing of surgery, surgical technique, timing of cranioplasty, and complications.

Survival with good outcome after cerebral herniation and Duret hemorrhage caused by traumatic brain injury

Brainstem hemorrhage can occur as a primary or secondary event in traumatic brain injury (TBI). Secondary brainstem hemorrhage that evolves from raised intracranial pressure and transtentorial herniation is referred to as Duret hemorrhage. Duret hemorrhage following TBI has been considered an irreversible and terminal event. The authors report on the case of a young adult patient with TBI who presented with a low Glasgow Coma Scale score and advanced signs of cerebral herniation. She underwent an urgent decompressive hemicraniectomy for evacuation of an acute epidural hematoma and developed a Duret hemorrhage postoperatively. In accordance with the family's wishes, aggressive TBI monitoring and treatment in the intensive care unit was continued even though the anticipated outcome was poor. After a lengthy hospital course, the patient improved dramatically and was discharged ambulatory, with good cognitive functioning and a Glasgow Outcome Scale score of 4. Duret hemorrhage secondary to raised intracranial pressure is not always a terminal event, and by itself should not trigger a decision to withdraw care. Aggressive intracranial monitoring and treatment of a Duret hemorrhage arising secondary to cerebral herniation may enable a good recovery in selected patients after severe TBI.