N-Terminal Pro-B-Type Natriuretic Peptide in Patients With Isolated Traumatic Brain Injury: A Prospective Cohort Study

Role of Brain Natriuretic Peptide in the Prediction of Early Postoperative Seizures Following Surgery for Traumatic Acute Subdural Hematoma: A Prospective Study

INTRODUCTION

Brain natriuretic peptide (BNP) is a reliable biomarker in the acute phase of traumatic brain injury. However, the relationship between BNP and traumatic acute subdural hematoma (aSDH) has not yet been addressed. This study aimed to analyze BNP levels on admission in surgically treated patients and assess their relationship with early postoperative seizures (EPS) and functional outcomes.

METHODS

Patients with unilateral traumatic aSDH who were surgically treated in our department between July 2017 and May 2020 were included in the study. BNP was preoperatively measured. Patients' neurologic condition, radiographic variables on initial cranial computed tomography, sodium serum levels on admission, and occurrence of EPS were prospectively assessed. Functional outcome was assessed using the modified Rankin Scale (mRS) at discharge and follow-up (at 2-3 months). A poor outcome was defined by a mRS score > 3.

RESULTS

EPS occurred in 20 (19.6%) of 102 surgically treated patients in the final cohort on the median day 3. A significant association between EPS and a poor Glasgow Coma Scale score at the 7th postoperative day was found, which in turn independently predicted a poor functional outcome at discharge and follow-up. Nonetheless, EPS were not associated with poor functional outcomes. The multivariate analysis revealed BNP > 95.4 pg/ml (aOR = 5.7, p = 0.003), sodium < 137.5 mmol/l (aOR = 4.6, p = 0.009), and left-sided aSDH (aOR = 4.4, p = 0.020) as independent predictors of EPS.

CONCLUSION

In the early postoperative phase of traumatic aSDH, EPS were associated with worse neurologic conditions, which in turn independently predicted poor outcomes at discharge and follow-up. Although several EPS risk factors have already been elucidated, this study presents BNP as a novel reliable predictor of EPS. Further larger studies are needed to determine whether a more precise estimate of EPS risk using BNP levels can be reached.

Analysis of Brain Natriuretic Peptide Levels after Traumatic Acute Subdural Hematoma and the Risk of Post-Operative Cerebral Infarction

Traumatic acute subdural hematoma (aSDH) is associated with a high mortality rate caused by post-operative cerebral infarction. Recently, brain natriuretic peptide (BNP) was considered a reliable biomarker in the acute phase of traumatic brain injuries. We therefore aimed in this study to analyze BNP levels on admission, identify the predictors of their elevation, and assess the relationship between BNP and the risk of post-operative cerebral infarction. Patients with isolated, unilateral, traumatic aSDH who were admitted to our department between July 2017 and May 2020 were enrolled in this study. On admission, cranial computer tomography (CCT) and BNP sampling were simultaneously performed. Additionally, the time between head trauma and BNP sampling (TTS) was assessed. Admission radiographic variables included hematoma volumes, midline shift, and degree of brain edema. Cerebral infarction was detected on postoperative CCT. In total, 130 patients were included in this study. Surgical treatment was performed in 82.3% (n = 107) of cases. The multiple regression analysis showed that larger hematoma volumes (p = 0.032) and advanced age (p = 0.005) were independent predictors of elevated BNP when TTS <24 h. The binomial logistical regression analysis identified BNP with a cutoff value of <29.4 pg/mL (TTS = 3-12 h, adjusted odds ratio [aOR] = 16.5, p = 0.023) as an independent predictor of post-operative cerebral infarction. Elevated BNP levels in the first 24 h post-trauma were related to larger hematoma volumes and advanced age. Further, an increased risk of post-operative cerebral infarction was identified in patients with lower BNP levels in the post-traumatic period 3-12 h.

Predictors of Brain Natriuretic Peptide Serum Level Elevation in Patients with Symptomatic Chronic Subdural Hematoma: A Prospective Study

Background: Brain natriuretic peptide serum levels (BNP) on admission are frequently elevated in patients with symptomatic chronic subdural hematoma (cSDH) and predict unfavorable long-term functional outcomes. However, the reasons for these elevated levels remain unclear. Therefore, we aimed to identify the predictors of BNP elevation. Methods: Patients with unilateral symptomatic cSDH who were surgically treated in our department between November 2016 and May 2020 were enrolled. Patients’ symptoms and neurological deficits were prospectively assessed using a study questionnaire. On initial computer tomography, hematoma volumes and midline shift (MLS) values were measured to analyze the degree of brain compression. Results: In total, 100 patients were analyzed. Linear regression analysis showed that higher BNP levels were significantly associated with smaller hematoma volumes (p = 0.003) and littler MLS values (p = 0.022). Multivariate analysis revealed that presence of a neurological deficit (p = 0.041), a hematoma volume < 140 mL (p = 0.047), advanced age (p = 0.023), and head trauma within 24 h of admission (p = 0.001) were independent predictors of BNP elevation. Conclusion: In symptomatic cSDH, BNP elevation is related, among others, to the presence of neurological deficits and smaller hematoma volumes. Whether BNP elevation may coincide with the early stage of hematoma growth, i.e., immaturity of cSDH neomembrane, requires further investigations.

Changes in Subendocardial Viability Ratio in Traumatic Brain Injury Patients

Background: Traumatic brain injury (TBI) is often associated with cardiac dysfunction, which is a consequence of the brain-heart cross talk. The subendocardial viability ratio (SEVR) is an estimate of myocardial perfusion. The aim of this study was to analyze changes in the SEVR in patients with severe TBI without previous cardiac diseases. Methods: Adult patients treated for severe TBI with a Glasgow coma score <8 were studied. Pressure waveforms were obtained by a high-fidelity tonometer in the radial artery for SEVR calculation at five time points: immediately after admission to the intensive care unit and 24, 48, 72, and 96 h after admission. SEVRs and other clinically important parameters were analyzed in patients who survived and did not survive after 28 days of treatment, as well as in patients who underwent decompressive craniectomy (DC). Results: A total of 64 patients (16 females and 48 males) aged 18-64 years were included. Fifty patients survived and 14 died. DC was performed in 23 patients. SEVRs decreased 24 h after admission in nonsurvivors (p < 0.05) and after 48 h in survivors (p < 0.01) and its values were significantly lower in nonsurvivors than in survivors at 24, 72, and 96 h from admission (p < 0.05). The SEVR increased following DC (p < 0.05). Conclusions: A decreased SEVR is observed in TBI patients. Surgical decompression increases the SEVR, indicating improvement in coronary microvascular perfusion. The results of our study seem to confirm that brain injury affects myocardium function.

Higher plasma NT-proBNP levels correlate with syndrome of inappropriate antidiuretic hormone and poor prognosis in neurological patients

Background

Hyponatremia induced by syndrome of inappropriate antidiuretic hormone secretion (SIADH) was common electrolyte disturbance encountered in critically ill neurological diseases, which has normal or increased fluid volume. Brain natriuretic peptide (BNP), which is released in equal proportion to N-terminal pro-brain natriuretic peptide (NT-proBNP), plays vital roles in regulation of volume status. The relationship between SIADH and NT-proBNP levels in neurological diseases has rarely been reported.

Methods

A retrospective cross-sectional study was conducted to analyze plasma NT-proBNP levels in 33 patients with SIADH and 23 controlled eunatremic patients with neurological diseases.

Results

Baseline NT-proBNP levels were compared between two groups [SIADH group: median 311 pg/mL, interquartile range (IQR) 110–768 pg/mL] vs. eunatremic group: median 46 pg/mL, IQR, 12–96 pg/mL) (P<0.05). Plasma NT-proBNP levels were markedly increased in hyponatremic patients who had two or more complications than those who had less complication (P<0.05). In SIADH patients, NT-proBNP levels in remission phase were lower to levels at baseline. Furthermore, no death was seen in eunatremic patients, while five SIADH patients died from complications.

Conclusions

SIADH had higher plasma NT-proBNP levels and poorer prognosis compared to eunatremic neurological patients. NT-proBNP serves as a biomarker of disease severity while not extracellular volume (ECV) status in critically ill neurological patients.

Role of brain natriuretic peptide in the prediction of long-term surgical outcome of chronic subdural hematoma

OBJECTIVE

To investigate the role of brain natriuretic peptide (BNP) in predicting long-term functional outcome and develop a new predictive score of poor functional outcome after surgery for chronic subdural hematoma (cSDH).

METHODS

Patients with cSDH that were surgically treated in our department between November 2016 and December 2019 were included in the study. Pre- and postoperative plasma BNP and clinical condition were prospectively recorded. At follow-up (5-6 months), a simplified modified Rankin Scale (mRS) questionnaire was conducted through a standardized telephone interview. A poor outcome was defined by a mRS > 3. Based on predictors of the long-term functional outcome, a score was calculated. Its accuracy was tested using the area under the curve (AUC) of the receiver operating characteristic analysis.

RESULTS

In total, 119 patients were analyzed (median age: 76 years, range: 44-94 years). Preoperative plasma BNP (BNP-1) was elevated in 77 patients (64.7%). For the follow-up phone interview, 101 patients (84.8%) were available. In the multivariate analysis, poor outcome at follow-up could be predicted using BNP-1 (p = 0.034), age (p = 0.036), motor deficit (p = 0.013) and Glasgow coma scale score on admission (p = 0.008). The "Functional Long-term Outcome Predictive score" (FLOP-score) was therefore computed, and revealed an excellent discriminative capacity compared to other scores, with an AUC of 0.86 (0.77-0.95).

CONCLUSIONS

Preoperative plasma BNP is an independent predictor of functional outcome at follow-up. Using the FLOP-score, the risk of experiencing a poor outcome could accurately be predicted.

Biomarkers for traumatic brain injury: a short review

Cellular response to TBI is a mixture of excitotoxicity, neuroinflammation, and cell death. Biomarkers that can track these lesions and inflammatory processes are being explored for their potential to provide objective measures in the evaluation of TBI, from prehospital care to rehabilitation. By understanding the pathways involved, we could be able to improve diagnostic accuracy, guide management, and prevent long-term disability. We listed some of the recent advances in this translational, intriguing, fast-growing field. Although the knowledge gaps are still significant, some markers are showing promising results and could be helping patients in the near future.

Analysis of Brain Natriuretic Peptide Serum Levels in Patients with Symptomatic Chronic Subdural Hematoma: A Potential Reliable Biomarker

The purpose of this study was to analyze brain natriuretic peptide (BNP) serum levels of patients with chronic subdural hematoma (cSDH) and their clinical implication. Patients with cSDH who underwent surgery in our department between November 2016 and October 2019 were eligible for enrollment in the study. Patients with recurrent bleedings, traumatic brain injury, cSDH associated with other intracranial pathologies, and those with a history of congestive heart failure, renal or endocrine disease were excluded. We measured BNP serum levels pre- and post-operatively and at discharge. The BNP values were analyzed with respect to patient medical history and neurological condition. The Glasgow Coma Scale score and the modified Rankin Scale score classified the clinical and neurological condition at the time of admission and discharge, respectively. The data of 100 surgically treated patients with cSDH (mean age 73.2, range 42 − 94 years, male/female 3.5:1) were analyzed. Pre-operative BNP serum levels (BNP-1) were elevated in 67% of the patients (n = 67; median = 101.6 pg/mL; p < 0.001). These serum levels increased after surgery (p < 0.001) and decreased thereafter (p < 0.001), reaching a level at discharge (day 7) that was not statistically different from BNP-1 (p > 0.05). In addition, elevated BNP-1 showed a significant statistical association with the presence of atrial fibrillation (p < 0.01) and antiplatelet and/or anticoagulant therapy (p < 0.01). This study provides new evidence regarding BNP serum levels and their secretion pattern in patients with cSDH. Whether BNP-1 can predict the long-term functional outcome of patients with cSDH is being investigated in this ongoing prospective study.

Brain-Heart Interactions in Traumatic Brain Injury

The cardiovascular manifestations associated with nontraumatic head disorders are commonly known. Similar manifestations have been reported in patients with traumatic brain injury (TBI); however, the underlying mechanisms and impact on the patient's clinical outcomes are not well explored. The neurocardiac axis theory and neurogenic stunned myocardium phenomenon could partly explain the brain-heart link and interactions and can thus pave the way to a better understanding and management of TBI. Several observational retrospective studies have shown a promising role for beta-adrenergic blockers in patients with TBI in reducing the overall TBI-related mortality. However, several questions remain to be answered in clinical randomized-controlled trials, including population selection, beta blocker type, dosage, timing, and duration of therapy, while maintaining the optimal mean arterial pressure and cerebral perfusion pressure in patients with TBI.

The role of N-terminal pro-brain natriuretic peptide in evaluating the prognosis of patients with intracerebral hemorrhage

A prognostic biomarker that can provide a good prediction of prognosis in patients with intracerebral hemorrhage (ICH) would be beneficial in guiding the initial management decisions in the setting of ICH. N-terminal pro-brain natriuretic peptide (NT-proBNP) is a biomarker of prognosis in patients with cardiovascular disease and ischemic stroke. However, the prognostic role of NT-proBNP in patients with spontaneous ICH is still a controversial issue. This study aimed to determine the prognostic value of NT-proBNP in patients with spontaneous ICH. A total of 132 patients from 571 ICH cases in inpatient settings were enrolled in this study. Blood samples from each subject were obtained and analyzed for NT-proBNP on admission and on days 4 and 7. The first end point was functional outcome at discharge, which was dichotomized into favorable or unfavorable; the secondary end point was mortality within 6 months after ICH. Compared with the baseline levels on admission after ICH, the NT-proBNP levels increased markedly on day 4 (P < 0.05). Multivariate logistic regression analysis indicated that the NT-proBNP level on day 4, the ICH score, and the APACHE II score were independent prognostic factors of functional outcome and 6-month mortality in ICH patients. A cutoff NT-proBNP level of 999.85 pg/ml predicted an unfavorable functional outcome (with 66.1% sensitivity and 98.7% specificity) and 6-month mortality (with 93.8% sensitivity and 92.0% specificity) in ICH patients. Thus, the NT-proBNP level on day 4 was found to be a powerful prognostic predictor of functional outcome and 6-month mortality in ICH patients, which would be beneficial to guiding the initial management decisions in the setting of ICH.

Investigation of changes in brain natriuretic peptide serum levels and its diagnostic value in patients with mild and moderate head trauma, in patients referred to emergency department of Alzahra Hospital, Isfahan, 2013-2014

Background:

Head trauma is one of the most common reasons for emergency department (ED) care. Over the past decade, initial management strategies in mild and moderate head trauma have become focused on selective computed tomography (CT) use based upon presence or absence of specific aspects of patient history and/or clinical examination which has received more attention following reports of increased cancer risk from CT scans. Recently changes in serum brain natriuretic peptide (BNP) levels following head trauma have been studied. We investigated the changes in serum levels of BNP in patients with mild and moderate head trauma, in whom the first brain CT scanning was normal.

Materials and Methods:

This study is a cross-sectional, descriptive research. It was performed in patients with mild and moderate head trauma. Forty-one patients with isolated mild and moderate traumatic brain injury (Glasgow Coma Scale = 9–15) were included. First brain CT scans were obtained during 2 h after ED arrival and the second one after 24 h. Plasma BNP levels were determined using a specific immunoassay system.

Results:

Twenty-three patients were in Group A (with normal first and second brain CT) and 18 patients in Group B (with normal first and abnormal second brain CT). With P = 0.001, serum BNP level = 9.04 was determined for differentiating two groups.

Conclusion:

We concluded that serum BNP level is higher in patients with mild and moderate head trauma with delayed pathologic changes in second brain CT relative to patients with mild and moderate head trauma and with normal delayed brain CT.

Cerebral Salt-Wasting Syndrome Caused by Minor Head Injury

A 34-year-old woman was admitted to hospital after sustaining a head injury in a motor vehicle accident (day 1). No signs of neurological deficit, skull fracture, brain contusion, or intracranial bleeding were evident. She was discharged without symptoms on day 4. However, headache and nausea worsened on day 8, at which time serum sodium level was noted to be 121 mEq/L. Treatment with sodium chloride was initiated, but serum sodium decreased to 116 mEq/L on day 9. Body weight decreased in proportion to the decrease in serum sodium. Cerebral salt-wasting syndrome was diagnosed. This case represents the first illustration of severe hyponatremia related to cerebral salt-wasting syndrome caused by a minor head injury.

N-Terminal Pro-Brain Natriuretic Peptide Concentrations After Hypertensive Intracerebral Hemorrhage: Relationship With Hematoma Size, Hyponatremia, and Intracranial Pressure

Introduction:

The role of N-terminal pro-brain natriuretic peptide (NT-proBNP) in patients with hypertensive intracerebral hemorrhage (HICH) is poorly understood. This study aimed to investigate the secretion pattern of NT-proBNP in patients with HICH and to assess its relationship with hematoma size, hyponatremia, and intracranial pressure (ICP).

Methods:

This prospective study enrolled 147 isolated patients with HICH. Blood samples were obtained from each patient, and values of serum NT-proBNP, hematoma size, blood sodium, and ICP were collected for each patient.

Results:

The peak-to-mean concentration of NT-proBNP was 666.8 ± 355.1 pg/mL observed on day 4. The NT-proBNP levels in patients with hematoma volume >30 mL were significantly higher than those in patients with hematoma volume <30 mL ( P < .05). In patients with severe HICH, the mean concentration of NT-proBNP was statistically higher than that in patients with mild–moderate HICH ( P < .05), and the mean level of NT-proBNP in hyponatremia group was significantly higher than that in normonatremic group ( P < .05). In addition, the linear regression analysis indicated that serum NT-proBNP concentrations were positively correlated with ICP ( r = .703, P < .05) but negatively with blood sodium levels only in patients with severe HICH ( r = −.704, P < .05). The serum NT-proBNP levels on day 4 after admission were positively correlated with hematoma size ( r = .702, P < .05).

Conclusion:

The NT-proBNP concentrations were elevated progressively and markedly at least in the first 4 days after HICH and reached a peak level on the fourth day. The NT-proBNP levels on day 4 were positively correlated with hematoma size. There was a notable positive correlation between plasma NT-proBNP levels and ICP in patients with severe HICH. Furthermore, only in patients with severe HICH, the plasma NT-proBNP levels presented a significant correlation with hyponatremia, which did not occur in patients with mild–moderate HICH.

Systemic complications of traumatic brain injury

PURPOSE OF REVIEW

Increased understanding of the pathophysiology in traumatic brain injury (TBI) has resulted in the development of core physiological targets and therapies to preserve cerebral oxygenation, and in doing so prevent secondary insult. This review addresses the many systemic complications of TBI that make achieving these targets challenging and can influence outcome.

RECENT FINDINGS

There are a wide range of systemic complications following TBI. Complications involve the cardiovascular, respiratory, immunological, haematological and endocrinological systems amongst others, and can influence early management and long-term outcomes.

SUMMARY

Effective management of TBI should go beyond formulaic-based pursuit of physiological targets and requires a detailed understanding of the multisystem response of the body.

Systemic manifestations of traumatic brain injury

Traumatic brain injury (TBI) affects functioning of various organ systems in the absence of concomitant non-neurologic organ injury or systemic infection. The systemic manifestations of TBI can be mild or severe and can present in the acute phase or during the recovery phase. Non-neurologic organ dysfunction can manifest following mild TBI or severe TBI. The pathophysiology of systemic manifestations following TBI is multifactorial and involves an effect on the autonomic nervous system, involvement of the hypothalamic-pituitary axis, release of inflammatory mediators, and treatment modalities used for TBI. Endocrine dysfunction, electrolyte imbalance, and respiratory manifestations are common following TBI. The influence of TBI on systemic immune response, coagulation cascade, cardiovascular system, gastrointestinal system, and other systems is becoming more evident through animal studies and clinical trials. Systemic manifestations can independently act as risk factors for mortality and morbidity following TBI. Some conditions like neurogenic pulmonary edema and disseminated intravascular coagulation can adversely affect the outcome. Early recognition and treatment of systemic manifestations may improve the clinical outcome following TBI. Further studies are required especially in the field of neuroimmunology to establish the role of various biochemical cascades, not only in the pathophysiology of TBI but also in its systemic manifestations and outcome.

Plasma brain-type natriuretic Peptide level following seizure and syncope: pilot study

Background and Purpose:

To explore the clinical feasibility of plasma brain-type natriuretic peptide (proBNP) level to differentiate the two major causes of transient unconsciousness, seizure and vasovagal syncope (VVS) in adult patients.

Methods:

ProBNP levels were evaluated within 24 hours following attack in patients who had experienced a transient episode of unconsciousness. For confirmatory diagnosis, clinical history was reviewed thoroughly and several work-ups including electroencephalography and cerebral imaging and tilt-table test, were performed in cases of putative VVS, as a part of routine clinical approaches.

Results:

According to various relevant evaluations, 15 patients were diagnosed as seizure (age, 40.3±13.8 years) and 12 patients were VVS (age, 38.1±17.1 years). Plasma concentrations of pro-BNP were not different between two groups (p=0.714). Median level was 34.3 pg/mL (interquartile range: 12.9–91.1) in post-seizure group and 32.3 pg/mL (interquartile range 8.9–77.4) in post-VVS group. Additionally, it was not correlated with the sampling times within 24 hours after the episodes.

Conclusions:

The plasma level of pro-BNP has a limited clinical value in differentiating seizure and vasovagal syncope in adults. However, the more validated results with a large population should be sought in the future studies to confirm its value.

Dynamic detection of N-terminal pro-B-type natriuretic peptide helps to predict the outcome of patients with major trauma

INTRODUCTION

NT-proBNP and BNP have been demonstrated to be prognostic markers in cardiac disease and sepsis. However, the prognostic value and the dynamic changes of BNP or NT-proBNP in trauma patients remain unclear. The present study was conducted to investigate the dynamic changes of NT-proBNP in patients with major trauma (injury severity score ≥16), determine whether NT-proBNP could be used as a simple index to predict mortality in major trauma patients.

METHODS

This prospective observational study included 60 patients with major trauma. Serum NT-proBNP levels were measured on the 1st, 3rd and 7th day after injury The NT-proBNP levels in survivors were compared with those in non-survivors. The efficacy of NT-proBNP to predict survival was analyzed using receiver operating characteristic curves. An analysis of correlations between NT-proBNP and various factors, including injury severity score, Glasgow coma score, acute physiology and chronic health evaluation II, central venous pressure, creatine kinase-MB, cardiac troponin I and procalcitonin (PCT) was performed. NT-proBNP levels in patients with traumatic brain injury were compared with those in patients without traumatic brain injury. A comparison of NT-proBNP levels between patients with and without sepsis was also performed at each time point.

RESULTS

NT-proBNP levels in non-survivors were significantly higher than those in survivors at all the indicated time points. In the group of non-survivors, NT-proBNP levels on the 7th day were markedly higher than those on the 1st day. In contrast, NT-proBNP levels in survivors showed a reduction over time. The efficacy of NT-proBNP to predict survival was analyzed using ROC curves, and there was no difference in the area under the ROC between NT-proBNP and APACHE II/ISS at the three time points. A significant correlation was found between NT-proBNP and ISS on the 1st day, NT-proBNP and CK-MB, Tn-I and APACHE II on the 3rd day, NT-proBNP and PCT on the 7th day. There were no significant differences in NT-proBNP levels between patients with or without brain trauma at all the indicated time points. NT-proBNP levels in patients with sepsis were significantly higher than those in patients without sepsis at all the indicated time points.

CONCLUSION

These findings suggest that dynamic detection of serum NT-proBNP might help to predict death in patients with major trauma. A high level of NT-proBNP at admission or maintained for several days after trauma indicates poor survival.

The value of Serum BNP for diagnosis of intracranial injury in minor head trauma

OBJECTIVE

Head injury is the main cause of death among individuals younger than 45 years old. Cranial Computerized tomography (CT) is commonly used for diagnosis of head injury. Brain Natriuretic Peptide (BNP) is a peptide originally isolated from brain ventricles. The main aim of this study is to investigate BNP as an indicator of head injury among patients presenting to emergency department (ED) with minor head trauma.

METHODS

This was a prospective study conducted at the emergency department of the Numune Training and Research Hospital. A total of 162 patients who presented to the ED with minor head injury were enrolled. The patients were categorized into 2 groups as the cranial CT-negative and positive groups. The normality of the data was tested using One Sample Kolmogorov Smirnov test. Mann-Whitney U test was used to compare 2 independent groups while the Kruskal-Wallis test was utilized for comparison of more than 2 groups. A p-value of <0.05 was considered to be significant.

RESULTS

Ninety-six (59.3%) patients were male and 66 (40.7%) were female. The cranial CT-negative group had a median BNP level of 14.5 pg/ml while the cranial CT-positive group had a median BNP level of 13 pg/ml. There was no statistically significant difference between these two groups for serum BNP levels (p > 0.05).

CONCLUSION

This study suggested that serum BNP level wasn't used in defined of intracranial injury.