Edited by: Cameron Bass, Duke University, United States
Reviewed by: Ralph George Depalma, United States Department of Veterans Affairs, United States; Lucia A. Rivera Lara, Johns Hopkins University, United States
Specialty section: This article was submitted to Neurotrauma, a section of the journal Frontiers in Neurology
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Despite seemingly functional coagulation, hemorrhagic lesion progression is a common and devastating condition following traumatic brain injury (TBI), stressing the need for new diagnostic techniques. Multiple electrode aggregometry (MEA) measures platelet function and could aid in coagulopathy assessment following TBI. The aims of this study were to evaluate MEA temporal dynamics, influence of concomitant therapy, and its capabilities to predict lesion progression and clinical outcome in a TBI cohort.
Adult TBI patients in a neurointensive care unit that underwent MEA sampling were retrospectively included. MEA was sampled if the patient was treated with antiplatelet therapy, bled heavily during surgery, or had abnormal baseline coagulation values. We assessed platelet activation pathways involving the arachidonic acid receptor (ASPI), P2Y12 receptor, and thrombin receptor (TRAP). ASPI was the primary focus of analysis. If several samples were obtained, they were included. Retrospective data were extracted from hospital charts. Outcome variables were radiologic hemorrhagic progression and Glasgow Outcome Scale assessed prospectively at 12 months posttrauma. MEA levels were compared between patients on antiplatelet therapy. Linear mixed effect models and uni-/multivariable regression models were used to study longitudinal dynamics, hemorrhagic progression and outcome, respectively.
In total, 178 patients were included (48% unfavorable outcome). ASPI levels increased from initially low values in a time-dependent fashion (
A general longitudinal trend of MEA is identified in this TBI cohort, even in patients without known antiplatelet therapies. Values appear also affected by platelet inhibitory treatment and by platelet transfusions. While significant in univariate models to predict outcome, MEA values did not independently correlate to outcome or lesion progression in multivariable analyses. Further prospective studies to monitor coagulation in TBI patients are warranted, in particular the interpretation of pathological MEA values in patients without antiplatelet therapies.
Traumatic brain injury (TBI) is a worldwide leading cause of mortality and disability (
Diagnosis of coagulopathy is complex (
While these techniques are primarily used to assess platelet function in cardiology patients, Multiplate®, based on multiple electrode aggregometry (MEA), use was shown to improve outcome prediction in a general trauma population (
In our department, a majority of patients with TBI in need of neurointensive care unit (NICU) care is assessed using MEA. This presents a unique opportunity to evaluate its utility within the clinical setting. With this in mind, we sought to characterize MEA alterations following TBI, analyze how MEA levels are altered in drug induced coagulopathy, examine how MEA levels are associated with bleeding progression in patients with severe TBI, and how it subsequentially affects outcome.
This was a retrospective observational study undertaken at the NICU at Karolinska University Hospital (Stockholm, Sweden) including patients treated between February 2010 (clinical introduction of MEA) and May 2014. The work was approved by the local ethics committee in Stockholm County, the Central Ethical Review Board (diary numbers 2014/1488-31/5 and 2015/1675-31/1).
Patients were included if they had suffered a traumatic intracranial lesion, were of ≥15 years of age, and had been admitted to the NICU during the years 2010–2014. All patients included were at all times treated according to local routine at the NICU, as earlier described in Ref. (
Trauma severity was assessed using the definitions of the Advanced Trauma and Life Support system (
Glasgow Outcome Scale (GOS) (
The Multiplate® (Roche Diagnostics, Basel, Switzerland) unit was used to assess MEA values. This is an impedance aggregometry method (
Using MEA, we evaluated three different platelet activation pathways: the arachidonic acid receptor (ASPI), P2Y12 receptor (ADP), and thrombin receptor (TRAP). These receptors are specifically inhibited by the pharmacological compounds: cyclooxygenase (COX) inhibitors (ASPI), P2Y12 inhibitors (ADP), and glycoprotein IIb/IIIa antagonists (TRAP) (
The full statistical protocol is described in the Supplementary Materials and Methods in the Supplementary Material. Demographic data were presented as mean ± SD, median (interquartile range), or count (%). Spearman correlation (rho, ρ) was used to assess correlation between different platelet receptor values, in addition to visual scatterplots. The distribution of MEA was examined using the Shapiro–Wilk test, and inferential analysis was conducted using the Mann–Whitney
Missing values relevant for outcome analysis were plotted (Figure S1 in Supplementary Material) using the R package neato (
Between 2010 and 2014, 387 TBI patients were admitted to the NICU at the Karolinska University Hospital. Of these, 178 underwent MEA analysis and were included. Patient demographics are presented in Tables
Patient demographics.
Variable | Type (unit) | Total number of patients: 178 |
---|---|---|
Gender | Male/female | 133/45 (75/25) |
Age | (years) | 54 (37–65) |
Oxygen saturation SoA | (%) | 96 (93–98) |
Missing | 68 (38) | |
Blood pressure SoA | Systolic (mmHg) | 130 (120–150) |
Missing | 69 (39) | |
Admission GCS | GCS 3 | 53 (30) |
GCS 4–5 | 15 (8) | |
GCS 6–8 | 31 (17) | |
GCS 9–13 | 47 (26) | |
GCS 14–15 | 32 (18) | |
Median | 7 | |
Pupil responsiveness admission | Normal | 138 (78) |
Unilateral unresponsive | 18 (10) | |
Bilateral unresponsive | 19 (11) | |
Missing | 3 (1.7) | |
Extracranial injury (multitrauma) | Present | 46 (26) |
Radiological findings | Midline shift (mm) | 3 (0–9) |
Progression hematoma | 60 (34) | |
Epidural hematoma | 20 (11) | |
Dual subdural hematoma | 11 (6) | |
Intraventricular bleeding | 28 (16) | |
Subarachnoid hemorrhage basal cisterns | 42 (24) | |
Subarachnoid hemorrhage convexity | 121 (68) | |
Stockholm CT score | Total score | 22 ± 9.6 |
Final GOS | GOS 1 (dead) | 22 (12) |
GOS 2 (vegetative) | 2 (1) | |
GOS 3 (severe, dependent) | 61 (34) | |
GOS 4 (moderate, independent) | 56 (31) | |
GOS 5 (recovered) | 37 (21) | |
GOS 1–3 (unfavorable) | 85 (48) | |
GOS 4–5 (favorable) | 93 (52) |
Coagulation status.
Variable | Patient values | Reference interval (unit) | |
---|---|---|---|
Platelet count admission | 212 (175–248) | 145–348 (109/l) | |
APTT admission | 31 (29–36) | 28–40 (s) | |
Missing | 9 (5) | ||
INR admission | 1.1 (1–1.2) | <1.2 (INR) | |
Missing | 6 (3) | ||
ASPI, first value | 51 (23.5–79) | 71–115; 65–119 (AU) | |
ADP, first value | 51 (31–69) | 57–113; 57–113 (AU) | |
TRAP, first value | 95 ± 35.6 | 84–128; 84–128 (AU) | |
Missing | 1 (0.56) | ||
Platelet transfusion | Transfused | 112 (63) | |
Missing | 4 (2) | ||
Platelet transfusion dose | Volume | 600 (0–1,142) | (ml) |
Missing | 10 (5.6) | ||
Erythrocyte transfusion | Transfused | 102 (57) | |
Fresh frozen plasma transfusion | Transfused | 80 (45) | |
COX inhibitor treatment | Treatment before admission | 42 (24) | |
ADP inhibitor treatment | Treatment before admission | 5 (2.8) |
There was a significant positive correlation between all three platelet receptors’ first MEA values (Figures S2A1–C1 in Supplementary Material). For the ASPI versus TRAP receptor, ρ = 0.59 (
The first MEA values were examined on 127 patients of which 30 had received COX inhibitor treatment. We excluded all patients who had received a platelet transfusion before MEA values were obtained. MEA values were lower for patients treated with COX inhibitors compared with those who were not (Figure
Pharmacologic modulation of multiple electrode aggregometry (MEA) values. The first arachidonic acid receptor (ASPI) values (indicated as individual data points and as summarizing boxplots) for a subset of patients with and without cyclooxygenase (COX) inhibitor treatment (and without preceding platelet transfusions) are depicted
Immediately following TBI, platelet function (ASPI) was low and thereafter increased over time (Figure
Platelet function alterations over time following TBI, dependent on prehospital cyclooxygenase (COX) inhibitor treatment. Patients with COX inhibitor treatment before hospital admission demonstrated a consistently lower arachidonic acid receptor (ASPI) value compared with those without COX inhibitor treatment
Linear mixed effect model for ASPI values among TBI patients.
Fixed effect variable | Estimate | SE | |
---|---|---|---|
Time from trauma | 0.10627 | 0.02 | <0.001 |
Platelet count | 0.09221 | 0.01381 | <0.001 |
COX inhibitor | −9.47869 | 4.23748 | 0.02583 |
The decision tree gives a graphic representation of information content that could aid rule based interpretation of the data. Decision trees from all seven imputations were compared visually and showed congruency overall (data not shown), of which one representative is shown (Figure
A decision tree for determining the importance of ASPI. A representative imputation of one of the decision trees is depicted. Each node in the tree denotes the predicted GOS value (indexed by color and GOS category number), followed by the percentage of patients belonging in each node. While moving downwards in the tree, GOS changes depending on the independent variables and the percentages of patients who pertain to the stipulated criteria decrease accordingly. Consistent across all imputations, ASPI values in the range of 32–68 affected the determination of Glasgow Outcome Scale (GOS) 4–5 among younger patients with higher GCS (only one imputation shown). Radiologic score was defined as the Stockholm CT score (
Relations of MEA values toward GOS levels were visualized with conditional density plots (CD plots, Figures
Depiction of univariate analysis of selected variables hypothesized to influence Glasgow Outcome Scale (GOS) or hemorrhagic progression. In panels
Univariate analysis of variables and correlations to final GOS.
Independent variable | Pseudo- |
|
---|---|---|
Age | 0.0008 | 0.067 |
GCS at admission | <0.0001 | 0.167 |
Pupil responsiveness | 0.0070, <0.0001 | 0.130 |
Stockholm CT score | <0.0001 | 0.208 |
Oxygen saturation at SoA | 0.0282 | 0.044 |
Blood pressure at SoA | 0.1401 | NS |
Injury Severity Score | 0.4317 | NS |
ASPI, 1st value | 0.0389 | 0.026 |
ADP, 1st value | 0.2874 | NS |
TRAP, 1st value | 0.0086 | 0.042 |
TPK at admission | 0.3616 | NS |
INR at admission | 0.4198 | NS |
APTT at admission | 0.0020 | 0.060 |
Platelet transfusion | 0.0030 | 0.054 |
COX inhibitor treatment | 0.0176 | 0.034 |
Radiologic intracranial hemorrhagic progression | 0.0001 | 0.104 |
Multivariable proportional odds analysis of variables affecting final GOS.
Independent variable | OR | CI | |
---|---|---|---|
Age | 0.966 | 0.948–0.984 | 0.000117 |
GCS admission | 1.130 | 1.05–1.21 | 0.001612 |
Pupil responsiveness | 0.596 | 0.355–1.00 | 0.0707 |
Stockholm CT score | 0.945 | 0.914–0.977 | 0.00176 |
Oxygen saturation SoA | 1.06 | 1.00–1.11 | 0.0685 |
Blood pressure SoA | 1.00 | 0.992–1.01 | 0.409 |
Radiological intracranial hemorrhagic progression | 0.363 | 0.196–0.671 | 0.00479 |
Relations of MEA as predictors toward hemorrhagic progression were visualized with CD plots (Figures
To the best of our knowledge, this is the first study to investigate the clinical utility of a platelet function method in a clinical TBI setting. We found that
Platelet function, as indicated by MEA, exhibits a temporal profile even in the absence of platelet inhibitors where MEA values are generally low initially, and subsequently increase over the days following TBI. If this also reflects a clinically significant coagulopathy is yet unknown. The first ASPI and TRAP values were associated with long-term outcome in univariable analyses, albeit they did not contribute with any independent information when adjusting with known outcome predictors. Radiologic intracranial hemorrhagic progression, an important predictor of long-term outcome, could not be predicted using MEA values. MEA may in part be able to identify patients who arrive with TBI using COX inhibitors from a general coagulopathy.
Trauma-induced coagulopathy, one of the secondary injuries following TBI, is a poorly defined condition incorporating a hypo- and a hypercoagulable state (
Platelet receptor values have but rarely (
In outcome analysis, CD plots of GOS and intracranial hemorrhagic progression exhibited a similar u-shaped relation between ASPI/GOS and ASPI/intracranial hemorrhagic progression, with both high and low levels suggesting worse outcomes. This implies that there might be ASPI values that are optimal to evade hemorrhagic progression and accordingly, affect GOS. However, these data should be interpreted cautiously, as the CD plots contained few observations at very low and high levels of ASPI. In univariate analysis (dependent variable GOS), both the first ASPI and TRAP values were significant. In multivariable analysis, this effect was no longer seen, meaning that ASPI and TRAP are meaningful for outcome prediction
Radiologic intracranial hemorrhagic progression was a strong predictor of GOS. However, in univariate analysis of predictors for radiologic hemorrhagic progression, APTT at admission was the only significant variable. GCS and Stockholm CT score at admission were borderline significant, implying that a worse initial clinical status was associated with future progression and deterioration. The finding of APTT is interesting, but not the focus of this study.
Platelet inhibitors are common among TBI patients due to demographic alterations (
A theoretical treatment for platelet dysfunction is platelet transfusion. Based on ASPI levels, we distinguished an increased platelet function following transfusion, as expected (
This study should be pursued by a blinded randomized prospective multicenter study on isolated (non-multitrauma) TBI patients using GOS and lesion progression as outcome variables. MEA measurements should be taken at fixed, consecutive time points. Using these data, it would be possible to establish eligible reference intervals at different time points and conduct outcome analysis.
This study holds all the limitations of a retrospective study. Residual confounding, confounding by indication, and treatment bias must be assumed to exist in our data. These highlight problems with retrospective observational analyses and emphasize the need for blinded prospective trials. However, in lack of such MEA is often performed as a screening to identify if unconscious TBI patients are on platelet inhibitors. This will present the physician with a multitude of pathological MEA values in patients without platelet inhibitors, and without a metric for interpretation. This highly motivates an observational study such as this, despite its retrospective nature. Moreover, despite caveats, this is one of the first and larger studies to analyze a large cohort of mild-to-severe TBI patients and as we have had access to large amounts of prospectively collected data, we believe our data set is clinically valid for an NICU TBI population. Further, we have access to some unique variables like the trauma time, successfully registered in all prehospital records. Importantly, we have used this for a reliable characterization of platelet function longitudinally, which can rarely be done in equally large materials elsewhere. Still, MEA samples were to a large extent obtained at different time points, and treatments given at others. Moreover, our assessment of intracranial hemorrhage progression could be a bit sensitive as any lesion present was taken into account. Previous studies have defined set threshold, such as a minimal blood volume of 2 ml on the first CT scan (
We present the first larger investigation of the clinical utility of platelet function measurements using MEA in NICU treated TBI patients. Following TBI, a general longitudinal trend, with initially low MEA values and a subsequent increase over days is seen, indicating a pathophysiological link. MEA levels were affected by both COX inhibitor treatment and platelet transfusion. Progression of intracranial hemorrhage is an important predictor of poor TBI prognosis but MEA values could not significantly predict this condition. Both ASPI and TRAP values were associated with outcome, but did not add any independent information in presence of other outcome predictors. In summary, these findings warrant further prospective, blinded trials to full understand the utility of MEA in TBI patients.
The study was carried out in accordance with Swedish legislation, the Declaration of Helsinki, and the specific recommendations stipulated by the local ethics committee in Stockholm County, Centrala Etikprövningsnämnden (the Central Ethical Review Board). The study was exempt from written informed consent, as it was carried out retrospectively on data base material, was purely observational, and did not inflict on patient treatment. The local ethics committee (the Central Ethical Review Board) approved the protocol of this study (diary numbers 2014/1488-31/5 and 2015/1675-31/1).
CL, ET, AF, MN, DN, B-MB, and MS designed and planned the study. CL, ET, and MN acquisitioned the data. CL, ET, AF, and DN analyzed and interpreted the data. CL drafted the manuscript. CL, ET, MN, AF, DN, MS, and B-MB revised the manuscript critically. All the authors read and approved the final manuscript and agreed to be accountable for all aspects of the work.
None of the coauthors have received any payment from a third party for any aspect of the submitted work. The authors have no financial relationships to disclose. B-MB has participated and lectured during Roche “user meetings,” which is an annual gathering of researchers and clinicians to share experiences and research results following usage of Multiplate®. CL has participated in one of those meetings. During the meeting, which each time extended for 1 day, food and beverages were provided free of charge. None of the other coauthors have any conflicts of interest to declare.
The authors gratefully acknowledge the support from Gunilla Malmborg Bornhall (Neurointensive Care Unit, Karolinska University Hospital, Stockholm, Sweden) for her valuable trauma database registration. They also thank Nils-Johan Lindborg (Neurointensive Care Unit, Karolinska University Hospital, Stockholm, Sweden) for valuable instructions on the handling of the Multiplate®. They also thank Björn Zylberszac (Critical Care Clinisoft, Karolinska University Hospital, Stockholm, Sweden) for his help with compilation of intensive care unit data.
The Supplementary Material for this article can be found online at