A quantitative computed tomography assessment of brain weight, volume, and specific gravity in severe head trauma

Role of substance P in cerebral edema and association with an estimated specific gravity of the brain and an outcome prediction in post-traumatic cerebral edema

Purpose

The study aims to evaluate the role of substance P in cerebral edema and outcomes associated with acute TBI.

Method

Patients with acute TBI who presented within 6 h and a CT scan showed predominantly cerebral edema were included in the study. Substance P level was assessed from a serum sample collected within 6 h of trauma. We also evaluated the brain-specific gravity using the Brain View software.

Result

A total of 160 (128 male) patients were recruited. The median serum substance P concentration was 167.89 (IQR: 101.09-238.2). Substance P concentration was high in the early hours after trauma (p = 0.001). The median specific gravity of the entire brain was 1.04. Patients with a low Glasgow coma scale (GCS) at admission had a high concentration of the substance P. In the univariate analysis, low GCS, elevated serum concentrations of substance P level, high Rotterdam grade, high cerebral edema grade, a high international normalized ratio value, and high blood sugar levels were associated with poor outcomes at six months. In logistic regression analysis, low GCS at admission, high cerebral edema grade, and elevated blood sugar level were strongly associated with poor outcomes at six months. The area under the receiver operating characteristic curve was 0.884 (0.826-0.941).

Conclusion

Serum substance P is strongly associated with the severity of cerebral edema after TBI. However, brain-specific gravity does not directly correlate with posttraumatic cerebral edema severity. Serum substance P does not influence the clinical outcome of traumatic brain injury.

Importance of CSF-based Aβ clearance with age in humans increases with declining efficacy of blood-brain barrier/proteolytic pathways

The kinetics of amyloid beta turnover within human brain is still poorly understood. We previously found a dramatic decline in the turnover of Aβ peptides in normal aging. It was not known if brain interstitial fluid/cerebrospinal fluid (ISF/CSF) fluid exchange, CSF turnover, blood-brain barrier function or proteolysis were affected by aging or the presence of β amyloid plaques. Here, we describe a non-steady state physiological model developed to decouple CSF fluid transport from other processes. Kinetic parameters were estimated using: (1) MRI-derived brain volumes, (2) stable isotope labeling kinetics (SILK) of amyloid-β peptide (Aβ), and (3) lumbar CSF Aβ concentration during SILK. Here we show that changes in blood-brain barrier transport and/or proteolysis were largely responsible for the age-related decline in Aβ turnover rates. CSF-based clearance declined modestly in normal aging but became increasingly important due to the slowing of other processes. The magnitude of CSF-based clearance was also lower than that due to blood-brain barrier function plus proteolysis. These results suggest important roles for blood-brain barrier transport and proteolytic degradation of Aβ in the development Alzheimer’s Disease in humans.

To understand if brain interstitial fluid/cerebrospinal fluid (ISF/CSF) exchange, CSF turnover, blood-brain barrier function or proteolysis were affected by aging or the presence of β amyloid plaques, Elbert et al. develop a non-steady state physiological model using MRI-derived brain volumes, stable isotope labeling kinetics of Aβ, and lumbar CSF Aβ concentration. Their model suggests an important role for blood-brain barrier transport and proteolytic degradation of Aβ in the development Alzheimer’s Disease in humans.

Escalate and De-Escalate Therapies for Intracranial Pressure Control in Traumatic Brain Injury

Severe traumatic brain injury (TBI) is frequently associated with an elevation of intracranial pressure (ICP), followed by cerebral perfusion pressure (CPP) reduction. Invasive monitoring of ICP is recommended to guide a step-by-step “staircase approach” which aims to normalize ICP values and reduce the risks of secondary damage. However, if such monitoring is not available clinical examination and radiological criteria should be used. A major concern is how to taper the therapies employed for ICP control. The aim of this manuscript is to review the criteria for escalating and withdrawing therapies in TBI patients. Each step of the staircase approach carries a risk of adverse effects related to the duration of treatment. Tapering of barbiturates should start once ICP control has been achieved for at least 24 h, although a period of 2–12 days is often required. Administration of hyperosmolar fluids should be avoided if ICP is normal. Sedation should be reduced after at least 24 h of controlled ICP to allow neurological examination. Removal of invasive ICP monitoring is suggested after 72 h of normal ICP. For patients who have undergone surgical decompression, cranioplasty represents the final step, and an earlier cranioplasty (15–90 days after decompression) seems to reduce the rate of infection, seizures, and hydrocephalus.

Serum osmolality, cerebrospinal fluid specific gravity and overt hepatic encephalopathy severity in patients with liver failure

BACKGROUND AND AIMS

Hepatic encephalopathy (HE) is a leading contributor to morbidity in liver disease. While hyperammonaemia plays a key role, the mechanisms of cerebral toxicity are unclear. We hypothesized that serum hyperosmolality contributes to HE during acute (ALF) and acute-on-chronic liver failure (ACLF) through mechanisms that affect the water and solute composition of the cerebral environment.

METHODS

We performed a retrospective analysis of serum osmolality, cerebral spinal fluid (CSF) solute density (specific gravity, determined from computed tomography attenuation) and clinical HE severity (Glasgow Coma Score [GCS]) at the time of intensive care admission in a prospectively identified cohort of liver failure patients with overt HE.

RESULTS

Seventy-three patients (39 ALF and 34 ACLF) were included, of whom 28 (38%) were comatose. Serum osmolality (303.9 ± 15.4 mOsm/kg) was elevated despite normal serum sodium (136.6 ± 6.3 mEq/L). Increased osmolality was independently associated with more severe encephalopathy (ordinal adjusted OR 0.26 [95% CI 0.22, 0.31] for higher GCS per standard deviation increase in osmolality) and lower CSF-specific gravity (linear adjusted β = -0.039 [95% CI -0.069, -0.009] Hounsfield unit per 1 mOsm/kg).

CONCLUSIONS

In the context of related research, these data suggest that hyperosmolality increases brain exposure to metabolic toxins by blood-brain barrier alteration and may be a unique therapeutic target.

Modification in CSF specific gravity in acutely decompensated cirrhosis and acute on chronic liver failure independent of encephalopathy, evidences for an early blood-CSF barrier dysfunction in cirrhosis

Although hepatic encephalopathy (HE) on the background of acute on chronic liver failure (ACLF) is associated with high mortality rates, it is unknown whether this is due to increased blood-brain barrier permeability. Specific gravity of cerebrospinal fluid measured by CT is able to estimate blood-cerebrospinal fluid-barrier permeability. This study aimed to assess cerebrospinal fluid specific gravity in acutely decompensated cirrhosis and to compare it in patients with or without ACLF and with or without hepatic encephalopathy. We identified all the patients admitted for acute decompensation of cirrhosis who underwent a brain CT-scan. Those patients could present acute decompensation with or without ACLF. The presence of hepatic encephalopathy was noted. They were compared to a group of stable cirrhotic patients and healthy controls. Quantitative brain CT analysis used the Brainview software that gives the weight, the volume and the specific gravity of each determined brain regions. Results are given as median and interquartile ranges and as relative variation compared to the control/baseline group. 36 patients presented an acute decompensation of cirrhosis. Among them, 25 presented with ACLF and 11 without ACLF; 20 presented with hepatic encephalopathy grade ≥ 2. They were compared to 31 stable cirrhosis patients and 61 healthy controls. Cirrhotic patients had increased cerebrospinal fluid specific gravity (CSF-SG) compared to healthy controls (+0.4 %, p < 0.0001). Cirrhotic patients with ACLF have decreased CSF-SG as compared to cirrhotic patients without ACLF (-0.2 %, p = 0.0030) that remained higher than in healthy controls. The presence of hepatic encephalopathy did not modify CSF-SG (-0.09 %, p = 0.1757). Specific gravity did not differ between different brain regions according to the presence or absence of either ACLF or HE. In patients with acute decompensation of cirrhosis, and those with ACLF, CSF specific gravity is modified compared to both stable cirrhotic patients and healthy controls. This pattern is observed even in the absence of hepatic encephalopathy suggesting that blood-CSF barrier impairment is manifest even in absence of overt hepatic encephalopathy.

Measurement of brain perfusion in newborns: pulsed arterial spin labeling (PASL) versus pseudo-continuous arterial spin labeling (pCASL)

BACKGROUND

Arterial spin labeling (ASL) perfusion-weighted imaging (PWI) by magnetic resonance imaging (MRI) has been shown to be useful for identifying asphyxiated newborns at risk of developing brain injury, whether or not therapeutic hypothermia was administered. However, this technique has been only rarely used in newborns until now, because of the challenges to obtain sufficient signal-to-noise ratio (SNR) and spatial resolution in newborns.

OBJECTIVE

To compare two methods of ASL-PWI (i.e., single inversion-time pulsed arterial spin labeling [single TI PASL], and pseudo-continuous arterial spin labeling [pCASL]) to assess brain perfusion in asphyxiated newborns treated with therapeutic hypothermia and in healthy newborns.

DESIGN/METHODS

We conducted a prospective cohort study of term asphyxiated newborns meeting the criteria for therapeutic hypothermia; four additional healthy term newborns were also included as controls. Each of the enrolled newborns was scanned at least once during the first month of life. Each MRI scan included conventional anatomical imaging, as well as PASL and pCASL PWI-MRI. Control and labeled images were registered separately to reduce the effect of motion artifacts. For each scan, the axial slice at the level of the basal ganglia was used for comparisons. Each scan was scored for its image quality. Quantification of whole-slice cerebral blood flow (CBF) was done afterwards using previously described formulas.

RESULTS

A total number of 61 concomitant PASL and pCASL scans were obtained in nineteen asphyxiated newborns treated with therapeutic hypothermia and four healthy newborns. After discarding the scans with very poor image quality, 75% (46/61) remained for comparison between the two ASL methods. pCASL images presented a significantly superior image quality score compared to PASL images (p < 0.0001). Strong correlation was found between the CBF measured by PASL and pCASL (r = 0.61, p < 0.0001).

CONCLUSION

This study demonstrates that both ASL methods are feasible to assess brain perfusion in healthy and sick newborns. However, pCASL might be a better choice over PASL in newborns, as pCASL perfusion maps had a superior image quality that allowed a more detailed identification of the different brain structures.

New and old tools for abdominal imaging in critically ill patients

Diagnostic imaging technology has advanced considerably during the past two decades. Different imaging techniques have been proposed for abdominal imaging in critically ill patients like plain radiography, sonography, computed tomography (CT), magnetic resonance and positron emission tomography. Sonography has been proven to be effective to detect free intra-peritoneal fluid and it is considered one of the primary diagnostic modalities for abdominal evaluation for trauma assessment. In our opinion sonography should replace other invasive techniques to rapidly triage blunt trauma patients with unstable vital signs and examine the peritoneal cavity as a site of major haemorrhage to expedite exploratory laparotomy. On the other hand, CT has become the imaging modality of choice in hemodynamically stable patients with multisystem blunt and penetrating trauma. New developments in the quantitative analysis of the CT images will improve our knowledge of pathophysiology, diagnostic and therapeutic management of abdominal pathologies in critically ill patients.

Mean cerebral blood flow measurements using phase contrast MRI in the first year of life

Alterations in cerebral blood flow (CBF) are believed to be linked to many of the neurological pathologies that affect neonates and small infants. CBF measurements are nonetheless often difficult to perform in this population, as many techniques rely on radioactive tracers or other invasive methods. In this study, mean global CBF was measured in 21 infants under the age of one, using non-invasive MRI techniques adapted to the neonatal population. Mean CBF was computed as the ratio of blood flow delivered to the brain (measured using phase contrast MRI) and brain volume (computed by segmenting anatomical MR images). Tests in adult volunteers and repeated measurements showed the flow measurements using the proposed method to be both accurate and reproducible. It was also found that cardiac gating need not be employed in infants with no known cardiac pathology. The developed technique can easily be appended to a neonatal MRI examination to provide rapid, robust, and non-invasive estimates of mean CBF, thus providing a means to monitor developmental or pathology-related alterations in cerebral perfusion and the impact of different treatment courses. In the imaged cohort, mean CBF and flow to the brain were found to rapidly increase during the first year of life (from approx. 25 to 60 ml blood/100 ml tissue/min), in good agreement with literature from other modalities where available. Mean CBF also showed a significant correlation with arterial oxygen saturation level and heart rate, but no significant correlation was found between CBF and the hematocrit or body temperature.

Computed tomography-estimated specific gravity at hospital admission predicts 6-month outcome in mild-to-moderate traumatic brain injury patients admitted to the intensive care unit

BACKGROUND

It is clear that patients with a severe traumatic brain injury (TBI) develop secondary, potentially lethal neurological deterioration. However, it is difficult to predict which patients with mild-to-moderate TBI (MM-TBI), even after intensive care unit (ICU) admission, will experience poor outcome at 6 months. Standard computed tomography (CT) imaging scans provide information that can be used to estimate specific gravity (eSG). We have previously demonstrated that higher eSG measurements in the standard CT reading were associated with poor outcomes after severe TBI. The aim of this study was to determine whether eSG of the intracranial content predicts 6-month outcome in MM-TBI.

METHODS

We analyzed admission clinical and CT scan data (including eSG) of 66 patients with MM-TBI subsequently admitted to our neurosurgical ICU. Primary outcome was defined as a Glasgow Outcome Scale score of 1 to 3 after 6 months. Discriminating power (area under the receiver operating characteristic curve [ROC-AUC], 95% confidence interval) of eSG to predict 6-month poor outcome was calculated. The correlation of eSG with the main ICU characteristics was then compared.

RESULTS

Univariate and stepwise multivariate analyses showed an independent association between eSG and 6-month poor outcome (P = 0.001). ROC-AUC of eSG for the prediction of 6-month outcomes was 0.87 (confidence interval: 0.77-0.96). Admission eSG values were correlated with the main ICU characteristics, specifically 14-day mortality (P = 0.004), length of mechanical ventilation (P = 0.01), length of ICU stay (P = 0.045), and ICU procedures such as intracranial pressure monitoring (P < 0.001).

CONCLUSIONS

In this MM-TBI cohort admitted to the ICU, eSG of routine CT scans was correlated with mortality, ICU severity, and predicted 6-month poor outcome. An external validation with studies that include the spectrum of TBI severities is warranted to confirm our results.

In vivo accuracy of two intraparenchymal intracranial pressure monitors

PURPOSE

To evaluate the in vivo accuracy of the new Pressio(®) device for intraparenchymal monitoring of intracranial pressure (ICP) versus the Codman(®) device and intraventricular measurement external ventricular drainage (EVD).

METHODS

Data were collected retrospectively for 30 consecutive patients admitted into a 25-bed neurosurgical intensive care unit of a university hospital between January and December 2009. Patients received both intraventricular and intraparenchymal ICP monitoring with Pressio(®) (n = 15) or Codman(®) (n = 15).

RESULTS

We obtained 3,089 data points from the 30 patients. Mean difference between intraparenchymal and EVD pressure (bias) was -0.6 mmHg, and limits of agreement (1.96 SD of the bias) were -8.1 to 6.9 mmHg with Pressio(®) and 0.3 mmHg with limits of agreement of -6.7 to 7.1 mmHg with Codman(®) (NS). The temporal difference was -0.7 ± 1.6 mmHg/100 h of monitoring with Pressio(®) and 0.1 ± 1.6 mmHg/100 h of monitoring with Codman(®) over the study period (NS).

CONCLUSIONS

Intraparenchymal pressure measured with both transducers approximates intraventricular cerebrospinal fluid pressure with an accuracy of ±7 mmHg.

Does brain swelling increase estimated specific gravity?

OBJECTIVE

At the acute phase of traumatic brain injury (TBI), brain swelling contributes substantially to the development of secondary neurological lesions. Elucidating the pathophysiology of brain swelling is crucial to improve TBI management. In a previous study, specific gravity (SG) of the noncontused hemisphere, as estimated by computed tomography (CT), was higher in patients with high Marshall CT scores and severe brain swelling. The aim of this study was to investigate the relationship between estimated specific gravity (eSG) and clinical variable suggestive of brain swelling.

DESIGN

Retrospective study of data from a prospectively established database.

SETTING

Neurology ICU in a teaching hospital in Paris, France.

PARTICIPANTS

We studied 20 patients with severe traumatic brain injury (TBI), 20 patients with high-grade subarachnoid hemorrhage (SAH) presenting similar brain-swelling criteria, 20 patients with low-grade SAH, and 20 healthy controls.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Estimated brain specific gravity was acquired from CT images obtained at ICU admission. eSG was estimated in the overall intracerebral content and in a region-of-interest composed of white matter and the diencephalon. eSG in the region of interest was significantly higher in the TBI patients than in the high-grade SAH patients (1.0350 +/- 0.0041 vs. 1.0310 +/- 0.0019 g/ml, P < 0.05). eSG was similar in the high-grade SAH, low-grade SAH, and control groups.

CONCLUSIONS

Our findings do not support a causal link between brain swelling and eSG elevation. The eSG increase in severe TBI patients is not due to brain swelling.

Does the brain become heavier or lighter after trauma?

An uncontrolled rise in intracranial pressure is probably the most common cause of death in traumatic brain-injured patients. The intracranial pressure rise is often due to cerebral oedema. Diffusion-weighted imaging has been extensively used to study cerebral oedema formation after trauma in experimental studies. Nevertheless, this technology is difficult to perform at the acute phase, especially in unstable head trauma patients. For these reasons, a safe examination allowing us to better understand the pathophysiology of cerebral oedema formation in such patients would be of great interest. Radiological attenuation is linearly correlated with estimated specific gravity in human tissue. This property gives the opportunity to measure in vivo the volume, weight and specific gravity of any tissue by computed tomography. We recently developed a software package (BrainView) for Windows workstations, providing semi-automatic tools for brain analysis from DICOM images obtained from cerebral computed tomography. In this review, we will discuss the results of the in vivo analysis of brain weight, volume and specific gravity and consider the use of this software as a new technology to improve our knowledge of cerebral oedema formation after trauma and to evaluate the severity of traumatic brain-injured patients.

Hypertonic saline solutions for treatment of intracranial hypertension

PURPOSE OF REVIEW

This review aims to provide an update on recent knowledge gained on hypertonic saline solutions for the treatment of intracranial hypertension. Explanatory approaches to the mechanisms underlying the edema-reducing effects of the solutions are outlined, practical aspects of use are presented, and trials that assessed their clinical utility are highlighted.

RECENT FINDINGS

With an established trauma system, hypertonic saline added to conventional fluid resuscitation did not improve long-term outcome in multiple injury with hypotension and brain trauma. In intensive care, hypertonic saline reduced intracranial hypertension after subarachnoid haemorrhage, brain trauma, and a variety of other brain diseases, including cerebral edema in acute liver failure.

SUMMARY

Hypertonic saline solutions have evolved as an alternative to mannitol or may be used in otherwise refractory intracranial hypertension to treat raised intracranial pressure. With high osmolar loads, the efficacy of the solution is enhanced, but no simple relationship between the saline concentration and the clinical effects of a solution is established. Caution is advised with high osmolar loads because they carry increased risks for potentially deleterious consequences of hypernatremia or may induce osmotic blood-brain barrier opening with possibly harmful extravasation of the hypertonic solution into the brain tissue.

A combined clinical and MRI approach for outcome assessment of traumatic head injured comatose patients

Traumatic brain injury (TBI) is associated with substantial consumption of health care resources. No clinical or paraclinical examination can reliably predict neurological evolution. In this study, we evaluated the ability of a combined clinical and MRI approach to predict outcome.

METHODS

This prospective study took place between June 2001 and March 2005 in a Neurosurgical Intensive Care Unit in Paris, France. Inclusion criteria were TBI patients still mechanically ventilated and without clinical signs of awareness after 2 weeks. Four clinical signs were assessed after cessation of sedation: grasping, yawning, chewing and paroxysmal sympathetic storm. FLAIR and T2* acquisitions on MRI were used in order to localize brain lesions. Statistically linked regions (clusters) were defined. Outcome was assessed at one year by Glasgow Outcome Scale (GOS).

FINDINGS

73 patients were included: 41 had poor outcome (GOS 1-3) and 32 had good outcome (GOS 4-5). Lesions in the clusters "right upper pons and right lower midbrain"," hypothalamus and basal forebrain","left parietal, left temporal, left occipital lobes and left insula" and the presence of grasping or chewing were associated with poor outcome in multivariate analysis. This combined clinical and MRI approach gives a much better prediction than MRI approach only (P < 0.009), with an area under the ROC curve of 0.94 (95 % CI, 0.89-1.00).

INTERPRETATION

These data suggest that MRI associated with clinical assessment improves outcome prediction in severe TBI patients.

Total cerebral blood flow and total brain perfusion in the general population: the Rotterdam Scan Study

Reduced cerebral perfusion may contribute to the development of cerebrovascular and neurodegenerative diseases. Little is known on cerebral perfusion in the general population, as most measurement techniques are too invasive for application in large groups of healthy individuals. Total cerebral blood flow (tCBF) can be noninvasively measured by magnetic resonance imaging (MRI) but is highly correlated with brain volume. We calculated total brain perfusion by dividing tCBF by brain volume, and we investigated determinants of total brain perfusion in comparison with tCBF. Secondly, we studied whether persons with a low tCBF or low total brain perfusion have a larger volume of white matter lesions (WML). This study is based on 892 persons aged 60 to 91 years from the Rotterdam Study, a population-based cohort study. We performed two-dimensional (2D) phase-contrast MRI for tCBF measurement. Brain volume and WML volume were quantitatively assessed. Cardiovascular determinants were assessed by interview and physical examination. We assessed associations between cardiovascular determinants and flow measures with linear regression models, adjusted for age and sex. Associations between tCBF or total brain perfusion and WML volume were assessed using general linear models. We found that determinants of tCBF and total brain perfusion differed largely due to the large influence of brain volume on tCBF values. Persons with low total brain perfusion had a significantly larger WML volume compared with those with high total brain perfusion. Prospective studies are required to unravel whether hypoperfusion contributes to WML formation or that tissue damage, manifested by WML, leads to brain hypoperfusion.

Effect of loxapine on electrical brain activity, intracranial pressure, and middle cerebral artery flow velocity in traumatic brain-injured patients

INTRODUCTION

Delirium is a frequent complication of traumatic brain injury, especially during the weaning period. Antipsychotic drugs are often used in this case. Loxapine is a tricyclic antipsychotic drug with sedating properties. The effects of intravenous loxapine on EEG as well as on systemic and cerebral hemodynamics after traumatic brain injury are unknown.

METHODS

Seven sedated and mechanically ventilated traumatic brain injured patients were studied 11 +/- 5 days after trauma. They were on continuous perfusion of sufentanil and midazolam. Left and right spectral edge frequency (SEFl, SEFr) of continuous EEG recording, intracranial pressure (ICP), mean flow velocity of the middle cerebral artery (MFV(MCA)) and mean arterial pressure (MAP) were simultaneously recorded and digitalized before and after loxapine infusion (10 mg in 10 min of continuous infusion).

RESULTS

Loxapine induced no significant change on MAP, MFV. On the contrary, it decreased ICP and both SEFl, SEFr. ETCO(2 )and the dose of vasopressors were not altered during the study period.

CONCLUSION

10 mg of loxapine administered intravenously over 10 min decreased brain electrical activity. There is a concomitant reduction in ICP without any significant change in cerebral blood flow velocity. The use of intravenous loxapine to control agitation is not accompanied by deleterious hemodynamic or systemic effects in ICU's traumatic brain injured patients.

Computed Tomographic Brain Density Measurement as a Predictor of Elevated Intracranial Pressure in Blunt Head Trauma

There are no independent computed tomography (CT) findings predictive of elevated intracranial pressure (ICP). The purpose of this study was to evaluate brain density measurement on CT as a predictor of elevated ICP or decreased cerebral perfusion pressure (CPP). A prospectively collected database of patients with acute traumatic brain injury was used to identify patients who had a brain CT followed within 2 hours by ICP measurement. Blinded reviewers measured mean density in Hounsfield Units (HU) within a 100-mm2 elliptical region at four standardized positions. Brain density measurement was compared for patients with an ICP of 20 or greater versus less than 20 mm Hg and CPP of 70 or greater versus less than 70 mm Hg. During a 2-year period, 47 patients had ICP monitoring after brain CT. Average age was 40 ± 18 years old; 93.6 per cent were male; mean Injury Severity Score was 25 ± 10; and Glasgow Coma Scale was 6 ± 4. There was no difference in brain density measurement for observer 1, ICP less than 20 (26.3 HU) versus ICP 20 or greater (27.4 HU, P = 0.545) or for CPP less than 70 (27.1 HU) versus CPP 70 or greater (26.2, P = 0.624). Similarly, there was no difference for observer 2, ICP less than 20 (26.8 HU) versus ICP 20 or greater (27.4, P = 0.753) and CPP less than 70 (27.6 HU) versus CPP 70 or greater (26.2, P = 0.436). CT-measured brain density does not correlate with elevated ICP or depressed CPP and cannot predict patients with traumatic brain injury who would benefit from invasive ICP monitoring.

Opposed effects of hypertonic saline on contusions and noncontused brain tissue in patients with severe traumatic brain injury

OBJECTIVE

The aim of this study was to quantify the effect of hypertonic saline solution on contused and noncontused brain tissue in patients with traumatic brain injury. We hypothesize that hypertonic saline would increase the volume of brain contusion while decreasing the volume of noncontused hemispheric areas.

DESIGN

Prospective observational study.

SETTING

Neurosciences critical care unit of a university hospital.

PATIENTS

Fourteen traumatic brain injury patients with increased intracranial pressure.

INTERVENTIONS

A computed tomography scan was performed before and after a 20-min infusion of 40 mL of 20% saline.

MEASUREMENTS AND MAIN RESULTS

The volume, weight, and specific gravity of contused and noncontused hemispheric areas were assessed from computed tomography DICOM images by using a custom-designed software (BrainView). Physiologic variables and natremia were measured before and after infusion. Hypertonic saline significantly increased natremia from 143 +/- 5 to 146 +/- 5 mmol/L and decreased intracranial pressure from 23 +/- 3 to 17 +/- 5 mm Hg. The volume of the noncontused hemispheric areas decreased by 13 +/- 8 mL whereas the specific gravity increased by 0.029 +/- 0.027%. The volume of contused hemispheric tissue increased by 5 +/- 5 mL without any con-comitant change in density. There was a wide interindividual variability in the response of the noncontused hemispheric tissue with changes in specific gravity varying between -0.0124% and 0.0998%.

CONCLUSIONS

Three days after traumatic brain injury, the blood- brain barrier remains semipermeable in noncontused areas but not in contusions. Further studies are needed to tailor the use of hypertonic saline in patients with traumatic brain injury according to the volume of contusions assessed on computed tomography.

Computed tomography-estimated specific gravity of noncontused brain areas as a marker of severity in human traumatic brain injury

In this study, we assessed the relationship between brain estimated specific gravity (eSG) and clinical symptoms, therapeutic intensity level, and outcome in human traumatic brain injury (TBI). Brain weight, volume, and eSG of the noncontused hemispheric areas were measured from computed tomography (CT) DICOM images on the initial (5 +/- 6 h) CT of 120 patients with severe TBI. Control values were obtained from 40 healthy patients. The eSG of the noncontused hemispheric areas was significantly higher in TBI patients than in controls. eSG was higher in patients having a Marshall CT classification of 3 or 4 or a low initial Glasgow coma score. Two groups were defined according to the eSG of the noncontused hemispheric areas: less than (n = 83, 69%) or more than (n = 37, 31%) the threshold of normality (defined as 1.96 sd above normal = 1.0355 g/mL). The occurrence of mydriasis, use of osmotherapy at the scene of the accident, and therapeutic intensity level were higher in the increased eSG group. The outcome at intensive care unit discharge was worse in patients with an increased eSG although the difference was no longer significant at 1 yr. eSG determination by CT analysis might be relevant in the early management of TBI.