Correlation of serum brain natriuretic peptide with hyponatremia and delayed ischemic neurological deficits after subarachnoid hemorrhage

Cardiovascular manifestations of neurologic disease

Cardiac manifestations of neurologic diseases are common in clinical practice. There are numerous anatomic and pathophysiologic links between the normal and abnormal function of both systems. There are a number of brain-heart interactions which affect the care of patients as well as help guide therapeutic development. This is exemplified in the area of vascular neurology where knowledge of the brain-heart connection is essential not only for bedside management but where collaborative efforts between neurology and cardiology are key in developing new strategies for ischemic stroke prevention and treatment, atrial fibrillation, and interventional techniques. This chapter will focus on cardiac manifestations of neurologic disease, with special emphasis on vascular and intensive care neurology, epilepsy, and neurodegenerative and peripheral nervous system diseases.

Hormonal dysfunction in neurocritical patients

PURPOSE OF REVIEW

Acute brain injury results in widespread systemic endocrine dysfunction and affects how we care for patients. We review the existing literature on incidence, type and duration of endocrine dysfunction with special focus on the pituitary dependent function.

RECENT FINDINGS

Acute studies document widespread alterations of the hypothalamic-pituitary-adrenal axis, disruption of the anterior hypothalamus related hormones, and alteration of regulation of sodium and fluid balance. Diagnostic testing and therapeutic intervention are outlined in this review. Relative adrenal insufficiency and cerebral salt wasting are the two main forms of endocrine dysfunction in neurocritical care patients.

SUMMARY

Surveillance for endocrine dysfunction and early treatment with hormonal replacement may be life-saving in neurologic critically ill patients.

Pituitary dysfunction after aneurysmal subarachnoid hemorrhage

Patients recovering from aneurysmal SAH often complain about weakness, fatigue and impaired cognitive skills. Pituitary dysfunction might be one possible reason for these complaints, as in patients with traumatic brain injury, hypopituitarism is known to be a common complication. There are only a few studies dealing with this problem in SAH patients, but these studies suggest that pituitary disturbances are very frequent after aneurysmal SAH. But anterior pituitary lobe disturbances might not be the only one responsible for some complaints or complications in patients suffering from aneurysmal SAH. Hyponatremia in the early state after SAH could be a hint for posterior pituitary lobe dysfunction.

Angiographically documented cerebral vasospasm following transsphenoidal surgery for pituitary tumors

Symptomatic cerebral vasospasm (CVS) after transsphenoidal surgery (TSS) is very rare compared with vasospasm resulting from aneurysmal subarachnoid hemorrhage (SAH). Fewer than six cases documented by cerebral angiography have been reported. We evaluated the records of 15 patients in whom SAH developed after TSS. Their clinical symptoms, radiological and laboratory findings were analyzed. Among 15 patients with postoperative SAH, 11 did not show CVS during their postoperative course. However, four patients presented with various clinical symptoms suggestive of CVS on postoperative days 7-9. They showed an abrupt drop of serum sodium level 1 or 2 days before the onset of CVS symptoms. Patients with TSS-related SAH should be managed with proactive and aggressive treatment. Hyponatremia, which usually occurs around the first week after TSS, should not be ignored as a matter of metabolic or hormonal disequilibrium commonly encountered after pituitary surgery.

Cardiovascular predictors of long-term outcomes after non-traumatic subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Cardiac injury is common after subarachnoid hemorrhage (SAH) and is associated with adverse early outcomes, but long-term effects are unknown. The first aim of this study was to compare the long-term rates of death, stroke, and cardiac events in SAH survivors versus a matched population without SAH. The second aim was to quantify the effects of cardiac injury on the outcome rates.

METHODS

This was a retrospective cohort study of patients with and without non-traumatic SAH. For aim #1, the predictor variable was SAH and the outcome variables were all-cause and cerebrovascular mortality, stroke, cardiac mortality, acute coronary syndrome (ACS), and heart failure (HF) admission. A multivariable Cox proportional hazards analysis was performed. For aim #2, the predictor variables were cardiac injury (elevated serum cardiac enzymes or a diagnosis code for ACS) and dysfunction (pulmonary edema on X-Ray or a diagnosis code for HF).

RESULTS

Compared with 4,695 members without SAH, the 910 SAH patients had higher rates of all-cause mortality (hazard ratio [HR 2.6], 95% confidence intervals [CI] 2.0-3.4), cerebrovascular mortality (HR 30.6, CI 13.5-69.4), and stroke (HR 10.2, CI 7.5-13.8). Compared with the non-SAH group, the SAH patients with cardiac injury had increased rates of all-cause mortality (HR 5.3, CI 3.0-9.3), cardiac mortality (HR 7.3, CI 1.7-31.6), and heart failure (HR 4.3, CI 1.53-11.88).

CONCLUSIONS

SAH survivors have increased long-term mortality and stroke rates compared with a matched non-SAH population. SAH-induced cardiac injury is associated with an increased risk of death and heart failure hospitalization.

Occurrence of vasospasm and infarction in relation to a focal monitoring sensor in patients after SAH: placing a bet when placing a probe?

INTRODUCTION

Vasospastic brain infarction is a devastating complication of aneurysmal subarachnoid hemorrhage (SAH). Using a probe for invasive monitoring of brain tissue oxygenation or blood flow is highly focal and may miss the site of cerebral vasospasm (CVS). Probe placement is based on the assumption that the spasm will occur either at the dependent vessel territory of the parent artery of the ruptured aneurysm or at the artery exposed to the focal thick blood clot. We investigated the likelihood of a focal monitoring sensor being placed in vasospasm or infarction territory on a hypothetical basis.

METHODS

From our database we retrospectively selected consecutive SAH patients with angiographically proven (day 7-14) severe CVS (narrowing of vessel lumen >50%). Depending on the aneurysm location we applied a standard protocol of probe placement to detect the most probable site of severe CVS or infarction. We analyzed whether the placement was congruent with existing CVS/infarction.

RESULTS

We analyzed 100 patients after SAH caused by aneurysms located in the following locations: MCA (n = 14), ICA (n = 30), A1CA (n = 4), AcoA or A2CA (n = 33), and VBA (n = 19). Sensor location corresponded with CVS territory in 93% of MCA, 87% of ICA, 76% of AcoA or A2CA, but only 50% of A1CA and 42% of VBA aneurysms. The focal probe was located inside the infarction territory in 95% of ICA, 89% of MCA, 78% of ACoA or A2CA, 50% of A1CA and 23% of VBA aneurysms.

CONCLUSION

The probability that a single focal probe will be situated in the territory of severe CVS and infarction varies. It seems to be reasonably accurate for MCA and ICA aneurysms, but not for ACA or VBA aneurysms.

Update on the management of subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating cerebrovascular disease. Outcome after SAH is mainly determined by the initial severity of the hemorrhage. Neuroimaging, in particular computed tomography, and aneurysm repair techniques, such as coiling and clipping, as well as neurocritical care management, have improved during the last few years. The management of a patient with SAH should have an interdisciplinary approach with case discussions between the neurointensivist, interventionalist and the neurosurgeon. The patient should be treated in a specialized neurointensive care unit of a center with sufficient SAH case volume. Poor-grade patients can be observed for complications and delayed cerebral ischemia through continuous monitoring techniques in addition to transcranial Doppler ultrasonography such as continuous electroencephalography, brain tissue oxygenation, cerebral metabolism, cerebral blood flow and serial vascular imaging. Neurocritical care should focus on neuromonitoring for delayed cerebral ischemia, management of hydrocephalus, seizures and intracranial hypertension, as well as of medical complications such as hyperglycemia, fever and anemia.

Evolving role of biomarkers in acute cerebrovascular disease

The development of a clinically validated biomarker of acute cerebral ischemia would have the potential to facilitate the use of time-sensitive reperfusion strategies, allow for individualization of patient care by predicting relative risk of hemorrhage and volume of penumbral tissue, and add valuable prognostic information for patients presenting with acute stroke. Additionally, a stroke biomarker might benefit early stage clinical research by serving as a surrogate measure of ischemic injury. Although at present there are no clinically validated biomarkers of acute stroke, previous studies have focused on markers associated with different components of the ischemic cascade, including microglial activation, inflammation, oxidative stress, neuronal injury, hemostasis, and endothelial dysfunction. Evolving technologies have provided high throughput approaches to investigate potential gene and protein signatures, and methods to measure newly discovered markers of cell death and immune responses. Prior to defining the clinical utility of stroke biomarkers, it is critical to understand the inherent limitations of a biomarker-based approach and define its potential value for providing adjunctive diagnostic and prognostic information. The identification and validation of a clinically relevant biomarker, or panel of markers, of stroke will ultimately require incorporation of both stringent research design and assessment in the clinical context in which the marker will be used.

Elevated BNP is associated with vasospasm-independent cerebral infarction following aneurysmal subarachnoid hemorrhage

BACKGROUND

Elevated levels of B-type natriuretic peptide (BNP) have been associated with cardiac dysfunction and adverse neurological outcomes after subarachnoid hemorrhage (SAH). We sought to determine whether elevated levels of BNP are independently associated with radiographic cerebral infarction after SAH.

METHODS

Plasma BNP levels were measured after admission, a mean of 5.5 ± 3.0 days after SAH onset. Cerebral infarction was determined by retrospective review of computerized tomography (CT) scans. Cerebral vasospasm was confirmed by the presence of vascular narrowing on cerebral angiogram. The association between BNP and cerebral infarction was quantified using multivariable logistic regression and reverse stepwise elimination of clinical covariates. A stratified analysis was performed to quantify the association between BNP levels and infarction in patients with and without angiographic vasospasm.

RESULTS

BNP levels were measured from 119 subjects. The median BNP level was 105 pg/ml (interquartile range 37-275 pg/ml). In our multivariable model, the top quartile of BNP levels (≥ 276 pg/ml) were associated with an increased odds of cerebral infarction (OR 4.2, P = 0.009). The stratified analysis showed that the association between BNP and infarction was strongest in patients without angiographic vasospasm (OR 7.8, P = 0.006).

CONCLUSIONS

Elevated levels of BNP are strongly and independently associated with cerebral infarction, and the association is most pronounced in patients without angiographic vasospasm. These results provide further evidence that other mechanisms can contribute to infarction, and BNP may be a useful biomarker in detecting patients at risk for adverse outcomes without large vessel vasospasm.

Transcranial Doppler ultrasonography for diagnosis of cerebral vasospasm after aneurysmal subarachnoid hemorrhage: mean blood flow velocity ratio of the ipsilateral and contralateral middle cerebral arteries

BACKGROUND

Transcranial Doppler (TCD) is widely accepted to monitor cerebral vasospasm after subarachnoid hemorrhage (SAH); however, its predictive value remains controversial.

OBJECTIVE

To investigate the predictive reliability of an increase in the mean blood flow velocity (mBFV) ratio of the ipsilateral to contralateral middle cerebral arteries (I/C mBFV) compared with the conventional absolute flow velocity.

METHODS

We retrospectively investigated the clinical and radiologic data of consecutive patients with SAH admitted from July 2003 to August 2009 who underwent TCD ultrasonography. The highest mBFV value in bilateral middle cerebral arteries was recorded, while delayed cerebral ischemia (DCI) was defined as neurological deficits or computed tomographic evidence of cerebral infarction caused by vasospasm. The ipsilateral side was defined as the side with higher mBFV value when evaluating the I/C mBFV. We thus elucidated the reliability of this rate in comparison with the conventional method for predicting DCI with receiver operating characteristic (ROC) analysis.

RESULTS

One hundred and forty-two patients were retrospectively analyzed with specific data from 1262 TCD studies. The ROC curve showed that the overall predictive value for DCI had an area under the curve of 0.86 (95% confidence interval: 0.76-0.96) when the I/C mBFV was used vs 0.80 (0.71-0.88) when the absolute flow velocity was used. The threshold value that best discriminated between patients with and without DCI was I/C mBFV of 1.5.

CONCLUSION

In patients with SAH, the I/C mBFV demonstrated a more significant correlation to vasospasm than the absolute mean flow velocity.

Hyponatremia is predictable in patients with aneurysmal subarachnoid hemorrhage--clinical significance of serum atrial natriuretic peptide

PURPOSE

Serum atrial natriuretic peptide (ANP) that is elevated after aneurysmal subarachnoid hemorrhage (SAH) causes diuresis and natriuresis (cerebral salt wasting) and might exacerbate delayed ischemic neurological deficit (DIND). We investigated relationships among hyponatremia, serum ANP elevation, and the onset of DIND after SAH.

MATERIALS AND METHODS

Thirty-nine consecutive patients (15 women and 24 men) with SAH were assigned to a normonatremia group or a group that developed hyponatremia after SAH. Serum ANP and brain natriuretic peptide were assessed after SAH. All patients remained normovolemic and normotensive. We attributed DIND to vasospasm only in the absence of other causes and when supported by cerebral angiography.

RESULTS

Hyponatremia developed after SAH in 11 patients (28.2%), among whom serum ANP concentrations at 0 and 3 days thereafter were significantly increased. Furthermore, DIND developed in five (45.5%) and two (7.1%) hyponatremic and normonatremic patients, respectively (P < 0.05). The serum ANP levels on day 0 after SAH were higher in Hunt and Kosnik grades 3-4 than in 1-2 and in Fisher groups 3-4 than in 1-2 (P < 0.05).

CONCLUSIONS

Increasing serum ANP concentrations were independently associated with hyponatremia resulting in DIND. Early treatment of hyponatremia might prevent DIND in patients after SAH.

Management of post-subarachnoid hemorrhage vasospasm

Permanent neurologic injury and death remain common outcomes following aneurysmal subarachnoid hemorrhage. Although many sophisticated techniques are evolving for securing intracranial aneurysms to prevent rebleeding, progress is lagging in the management of posthemorrhagic complications, particularly cerebral vasospasm. Vasospasm can be defined either angiographically, by visible reduction in arterial lumen diameters, or clinically, with signs of focal or regional cerebral ischemia. The relationship between angiographic and clinical vasospasm is not straightforward. The most important known risk factors for developing posthemorrhagic vasospasm include volume and distribution of subarachnoid blood, and no preventive measures have proven effective. Established treatment strategies for vasospasm include hyperdynamic therapy, angioplasty, and selective intra-arterial injection of vasodilators. The vasodilatory approach has been called into question by recent data suggesting that reduction of arterial luminal diameters may be due largely to a proliferative arteriopathy. Novel treatment strategies have focused on protecting the cerebrum, targeting components of the inflammatory cascade, and identifying genetic factors predisposing toward vasospasm, all of which may soon yield new treatment modalities.

Cerebral salt wasting: pathophysiology, diagnosis, and treatment

Cerebral salt wasting (CSW) is a syndrome of hypovolemic hyponatremia caused by natriuresis and diuresis. The mechanisms underlying CSW have not been precisely delineated, although existing evidence strongly implicates abnormal elevations in circulating natriuretic peptides. The key in diagnosis of CSW lies in distinguishing it from the more common syndrome of inappropriate secretion of antidiuretic hormone. Volume status, but not serum and urine electrolytes and osmolality, is crucial for making this distinction. Volume and sodium repletion are the goals of treatment of patients with CSW, and this can be performed using some combination of isotonic saline, hypertonic saline, and mineralocorticoids.

Medical complications after subarachnoid hemorrhage

The prevention and management of medical complications are important for improving outcomes after subarachnoid hemorrhage (SAH). Fever, anemia requiring transfusion, hyperglycemia, hyponatremia, pneumonia, hypertension, and neurogenic cardiopulmonary dysfunction occur frequently after SAH. There is increasing evidence that acute hypoxia and extremes of blood pressure can exacerbate brain injury during the acute phase of bleeding. There are promising strategies to minimize these complications. Randomized controlled trials are needed to evaluate the risks and benefits of these and other medical management strategies after SAH.

Brain natriuretic peptide improves long-term functional recovery after acute CNS injury in mice

There is emerging evidence to suggest that brain natriuretic peptide (BNP) is elevated after acute brain injury, and that it may play an adaptive role in recovery through augmentation of cerebral blood flow (CBF). Through a series of experiments, we tested the hypothesis that the administration of BNP after different acute mechanisms of central nervous system (CNS) injury could improve functional recovery by improving CBF. C57 wild-type mice were exposed to either pneumatic-induced closed traumatic brain injury (TBI) or collagenase-induced intracerebral hemorrhage (ICH). After injury, either nesiritide (hBNP) (8 microg/kg) or normal saline were administered via tail vein injection at 30 min and 4 h. The mice then underwent functional neurological testing via rotorod latency over the following 5 days and neurocognitive testing via Morris water maze testing on days 24-28. Cerebral blood flow (CBF) was assessed by laser Doppler from 25 to 90 min after injury. After ICH, mRNA polymerase chain reaction (PCR) and histochemical staining were performed during the acute injury phase (<24 h) to determine the effects on inflammation. Following TBI and ICH, administration of hBNP was associated with improved functional performance as assessed by rotorod and Morris water maze latencies (p < 0.01). CBF was increased (p < 0.05), and inflammatory markers (TNF-alpha and IL-6; p < 0.05), activated microglial (F4/80; p < 0.05), and neuronal degeneration (Fluoro-Jade B; p < 0.05) were reduced in mice receiving hBNP. hBNP improves neurological function in murine models of TBI and ICH, and was associated with enhanced CBF and downregulation of neuroinflammatory responses. hBNP may represent a novel therapeutic strategy after acute CNS injury.

Neurologic presentations of acid-base imbalance, electrolyte abnormalities, and endocrine emergencies

Accurate identification of nervous system dysfunction is vital in the assessment of any multisystem disorder. The neurologic manifestations of acid-base disturbances, abnormal electrolyte concentrations, and acute endocrinopathies are protean and typically determined by the acuity of the underlying derangement. Detailed history and physical examination may guide appropriate laboratory testing and lead to prompt and accurate diagnosis. Neurologic manifestations of primary and secondary systemic disorders are frequently encountered in all subspecialties of medicine. This article focuses on key neurologic presentations of respiratory and metabolic acid-base derangements and potentially life-threatening endocrinopathies.

S100B and brain natriuretic peptide predict functional neurological outcome after intracerebral haemorrhage

OBJECTIVE

To determine the predictive value of S100b and brain natriuretic peptide (BNP) in order to determine accurately and quickly a discharge prognosis after primary supratentorial intracerebral haemorrhage (ICH).

METHODS

After IRB approval and informed consent, blood samples were obtained and analysed from 28 adult patients consecutively admitted to the neuroscience intensive care unit with computed tomography-proven supratentorial ICH from June 2003 and December 2004 within the first 24 h after symptom onset for S100b and BNP. Functional outcomes on discharge were dichotomized to favourable (mRS < 3) or unfavourable.

RESULTS

BNP (a neurohormone) and S100b (a marker of glial activation) were found to be independently highly predictive of functional neurological outcome at the time of discharge as measured by the modified Rankin Score (BNP: p < 0.01, r = 0.46; S100b: p < 0.01, r = 0.42) and the Barthel Index (BNP: p < 0.01, r = 0.54; s100b: p < 0.01, r = 0.50). Although inclusion of either biomarker produced additive value when included with traditional clinical prognostic variables, such as the ICH score (Barthel index: p < 0.01, r = 0.66; mRS: p < 0.01, r = 0.96), little predictive power is added with inclusion of both biomarkers in a regression model for neurological outcome.

CONCLUSIONS

Serum S100b and BNP levels in the first 24 h after injury accurately predict neurological function at discharge after supratentorial ICH.

Neurogenic stunned myocardium

Neurogenic stunned myocardium may be defined as myocardial injury and dysfunction occurring after diverse types of acute brain injury as a result of imbalance of the autonomic nervous system. The spectrum of observed cardiac abnormalities includes electrocardiographic changes, arrhythmia, myocardial necrosis, release of B-type natriuretic peptide, and both systolic and diastolic dysfunction of the left ventricle. These are reversible abnormalities, and although management should include careful cardiac monitoring, treatments should generally focus on the underlying neurologic process to maximize neurologic recovery.

Transcranial Doppler for predicting delayed cerebral ischemia after subarachnoid hemorrhage

OBJECTIVE

Transcranial Doppler (TCD) is widely used to monitor the temporal course of vasospasm after subarachnoid hemorrhage (SAH), but its ability to predict clinical deterioration or infarction from delayed cerebral ischemia (DCI) remains controversial. We sought to determine the prognostic utility of serial TCD examination after SAH.

METHODS

We analyzed 1877 TCD examinations in 441 aneurysmal SAH patients within 14 days of onset. The highest mean blood flow velocity (mBFV) value in any vessel before DCI onset was recorded. DCI was defined as clinical deterioration or computed tomographic evidence of infarction caused by vasospasm, with adjudication by consensus of the study team. Logistic regression was used to calculate adjusted odds ratios for DCI risk after controlling for other risk factors.

RESULTS

DCI occurred in 21% of patients (n = 92). Multivariate predictors of DCI included modified Fisher computed tomographic score (P = 0.001), poor clinical grade (P = 0.04), and female sex (P = 0.008). After controlling for these variables, all TCD mBFV thresholds between 120 and 180 cm/s added a modest degree of incremental predictive value for DCI at nearly all time points, with maximal sensitivity by SAH day 8. However, the sensitivity of any mBFV more than 120 cm/s for subsequent DCI was only 63%, with a positive predictive value of 22% among patients with Hunt and Hess grades I to III and 36% in patients with Hunt and Hess grades IV and V. Positive predictive value was only slightly higher if mBFV exceeded 180 cm/s.

CONCLUSION

Increased TCD flow velocities imply only a mild incremental risk of DCI after SAH, with maximal sensitivity by day 8. Nearly 40% of patients with DCI never attained an mBFV more than 120 cm/s during the course of monitoring. Given the poor overall sensitivity of TCD, improved methods for identifying patients at high risk for DCI after SAH are needed.

Clinical significance of elevated natriuretic peptide levels and cardiopulmonary parameters after subarachnoid hemorrhage

Daily changes in serum concentrations of natriuretic peptides and various cardiopulmonary parameters were measured after the onset of subarachnoid hemorrhage (SAH) to investigate the pathogenesis of the cardiac and pulmonary consequences in 15 patients with acute phase SAH, divided into the control group (n = 5) with consciousness continuously preserved from SAH onset to admission, and the consciousness disturbance group (n = 10). Daily changes in serum A-type and B-type natriuretic peptides (ANP and BNP, respectively) were measured for 10 days, and intrathoracic blood volume index and extravascular lung water index (EVLWI) were measured for 5 days by the single transpulmonary thermodilution method. Natriuretic peptides in the consciousness disturbance group showed significantly higher values during the 10-day period, with ANP 119.2 +/- 12.4 pg/ml (mean +/- standard error of the mean, p = 0.005) on day 2 and BNP 354.1 +/- 80.3 pg/ml (p = 0.009) on day 1. EVLWI showed higher values in the consciousness disturbance group compared to the control group throughout the 5-day period. The increases in natriuretic peptide levels and increase in pulmonary extravascular water content found in SAH patients with consciousness disturbance show that load on the left ventricle or atrium as well as pulmonary capillary pressure are increased immediately after onset, supporting the contention that excessive release of catecholamines occurs at this time.

Prevalence and clinical demographics of cerebral salt wasting in patients with aneurysmal subarachnoid hemorrhage

Hyponatremia is a frequent complication following subarachnoid hemorrhage (SAH), and is commonly attributed either to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) or cerebral salt wasting syndrome (CSW). The object of this study is to elucidate the clinical demographics and sequelae of hyponatremia due to CSW in subjects with aneurysmal SAH. Retrospective chart review of patients >18 years with aneurysmal SAH admitted between January 2004 and July 2007 was performed. Subjects with moderate to severe hyponatremia (serum sodium <130 mmol l(-1)) were divided into groups consistent with CSW and SIADH based on urine output, fluid balance, natriuresis, and response to saline infusion. Clinical demographics were compared. Of 316 subjects identified, hyponatremia (serum sodium <135 mmol l(-1)) was detected in 187 (59.2%) subjects and moderate to severe hyponatremia in 48 (15.2%). Of the latter group, 35.4% were categorized with SIADH and 22.9% with CSW. Compared to eunatremic subjects, hyponatremia was associated with significantly longer hospital stay (15.7 +/- 1.9 vs. 9.6 +/- 1.1 days, p < 0.001). Subjects with CSW had similar mortality and duration of hospital stay vs. those with SIADH. Though less common than SIADH, CSW was detected in approximately 23% of patients with history of aneurysmal SAH and was not clearly associated with enhanced morbidity and mortality compared to subjects with SIADH. Further studies regarding the pathogenesis and management, along with the medical consequences, of CSW are important.

[Etiology, diagnostics and therapy of hyponatremias]

Etiopathogenesis, diagnostics and therapy of hyponatremias are summarized for clinicians. Hyponatremia is the most common electrolyte abnormality. Mild to moderate hyponatremia and severe hyponatremia are found in 15-30% and 1-4% of hospitalized patients, respectively. Pathophysiologically, hyponatremias are classified into two groups: hyponatremia due to non-osmotic hypersecretion of vasopressin (hypovolemic, hypervolemic, euvolemic) and hyponatremia of non-hypervasopressinemic origin (pseudohyponatremia, water intoxication, cerebral salt wasting syndrome). Patients with mild hyponatremia are almost always asymptomatic. Severe hyponatremia is usually associated with central nervous system symptoms and can be life-threatening. Diagnostic evaluation of patients with hyponatremia is directed toward identifying the extracellular fluid volume status, the neurological symptoms and signs, the severity and duration of hyponatremia, the rate at which hyponatremia developed. The first step to determine the probable cause of hyponatremia is the differentiation of the hypervasopressinemic and non-hypervasopressinemic hyponatremias with measurement of plasma osmolality, glucose, lipids and proteins. For further differential diagnosis of hyponatremia, the determination of urine osmolality, the clinical assessment of extracellular fluid volume status and the measurement of urine sodium concentration provide important information. The most important representative of euvolemic hyponatremias is SIADH. The diagnosis of SIADH is based on the exclusion of other hyponatremic conditions; low plasma osmolality (<275 mosmol/kg) and inappropriate urine concentration (urine osmolality >100 mosmol/kg) are of pathognomic value. Acute (<48 hrs) severe hyponatremia (<120 mmol/l) necessitates emergency care with rapid restoration of normal osmotic milieu (1 mmol/l/hr increase rate of serum sodium). Patients with chronic symptomatic hyponatremia have a high risk of osmotic demyelination syndrome in brain if rapid correction of the plasma sodium occurs (maximal rate of correction of serum sodium should be 0.5 mmol/l/hr or less). The conventional treatments for chronic asymptomatic hyponatremia (except hypovolemic patients) include water restriction and/or the use of demeclocycline or lithium or furosemide and salt supplementation. Vasopressin receptor antagonists have opened a new forthcoming therapeutic era. V2 receptor antagonists, such as lixivaptan, tolvaptan, satavaptan and the V2+V1A receptor antagonist conivaptan promote the electrolyte-sparing excretion of free water and lead to increased serum sodium.

Brain natriuretic peptide correlates with the extent of atrial fibrillation-associated silent brain lesions

OBJECTIVE

Identification of plasma markers indicative for atrial fibrillation-associated silent brain lesions.

DESIGN AND METHODS

1. Comparative determination of the plasma concentrations of secretagogin, S100B, neuropeptide Y, brain fatty acid binding protein, matrix metalloprotease 9, brain natriuretic peptide, and of D-Dimer in 222 patients with atrial fibrillation and 28 controls by immunoassays. 2. Correlation of the biochemical marker plasma concentration with the extent of silent white matter brain lesions, as determined by the Fazekas score and N-acetylaspartate-spectroscopy.

RESULTS

1. Plasma concentrations of brain natriuretic peptide, of neuropeptide Y, and of matrix metalloprotease 9 were significantly higher (all with a p<0.05) in patients suffering from atrial fibrillation than in control subjects. 2. Brain natriuretic peptide correlated significantly with the Fazekas score (R=0.41; p<0.005). 3. Brain natriuretic peptide plasma concentrations were significantly higher in patients with a pathological N-acetylaspartate magnetic resonance-spectrometry (p<0.05).

CONCLUSION

Brain natriuretic peptide plasma concentrations correlate with the extent of atrial fibrillation-associated silent brain lesions.

Diagnostic and prognostic impact of brain natriuretic peptide in cardiac and noncardiac diseases

OBJECTIVE

Cardiac secretion of brain natriuretic peptide (BNP) increases with the progression of congestive heart failure (CHF). The plasma measurement of BNP emerged recently as a useful, cost-effective biomarker for the diagnosis and prognosis of CHF.

METHODS

BNP assay is useful for evaluating patients with acute dyspnea, because a low level can help rule out CHF in primary care settings and reduce the demand for echocardiography. Equally, BNP level can be particularly useful in recognizing heart failure in a patient with acute dyspnea and a history of chronic obstructive pulmonary disease.

RESULTS

However, although the clinical use of BNP as a biomarker in CHF is increasing, the specificity of BNP in CHF is not strong, suggesting that other mechanisms beyond simple ventricular stretch stimulate BNP release. Multiple disorders in the intensive care unit, apart from CHF, cause elevated BNP levels, including cardiovascular disease states such as ischemia, arrhythmias, cardiac hypertrophy, and coronary endothelial dysfunction, as well as disorders of no cardiac origin, such as sepsis, septic shock, and acute respiratory distress syndrome. Moreover, the impact of increased BNP in patients with sepsis is not clear. The relationship between BNP and both left ventricular ejection fraction and left-sided filling pressures is weak, and data on the prognostic impact of high BNP levels in patients with sepsis are conflicting.

CONCLUSION

Nevertheless, this review highlights the potential benefits of BNP in the recognition and management of heart failure, and defines the gray zones of BNP levels; it also identifies conditions influencing BNP levels in relation to a certain heart failure and describes conditions of no cardiac origin with increased BNP.

Cerebral salt wasting syndrome: review

Hyponatremia is the most frequent electrolyte disorder in critically neurological patients. Cerebral salt wasting syndrome (CSW) is defined as a renal loss of sodium during intracranial disease leading to hyponatremia and a decrease in extracellular fluid volume. The pathogenesis of this disorder is still not completely understood. Sympathetic responses as well as some natriuretic factors play a role in this syndrome. Distinction between SIADH and CSW might be difficult. The essential point is the volemic state. It is necessary to rule out other intermediate causes. Treatment requires volume replacement and maintenance of a positive salt balance. Mineral corticoids may be useful in complicated cases.

Cerebral salt wasting and elevated brain natriuretic peptide levels after traumatic brain injury: 2 case reports

BACKGROUND

Historically, hyponatremia in patients with varying brain diseases was termed cerebral salt wasting. Hyponatremia secondary to CSW was reported to be a distinct entity from SIADH, with the distinguishing feature of decreased extracellular fluid volume. Brain natriuretic peptide, a peptide with natriuretic, vasorelaxant, and aldosterone-inhibiting properties, was recently implicated in aneurysmal SAH patients with CSW. Here, we describe 2 cases of CSW in TBI patients with elevated BNP levels. This phenomenon has not been previously described.

CASE DESCRIPTION

Two patients with TBI and hyponatremia were subject to analysis. Central lines were placed to assess volume status. Levels of BNP were measured at the onset of hypertonic saline infusion. Electrocardiogram and cardiac enzyme studies were performed to assess cardiac function. Serial imaging was performed to assess the extent of brain injury.

CONCLUSIONS

These patients with TBI had findings consistent with CSW with elevated BNP levels in the setting of normal cardiac function. In both cases, a high BNP level was observed after declining plasma Na levels despite aggressive hypertonic saline infusion. High BNP levels may be associated with CSW. Further studies are necessary to establish a causative role for BNP in TBI-induced CSW.

Respiratory care

PURPOSE OF THE REVIEW

Neurosurgical patients frequently develop respiratory complications, adversely affecting neurologic outcome and survival. The review summarizes current literature and management of respiratory complications associated with brain injury.

MAJOR FINDINGS

Respiratory complications are commonly associated with traumatic brain injury and subarachnoid haemorrhage. Lung-protective ventilation with reduced tidal volumes improves outcome in acute lung injury, and should be applied to neurosurgical patients in the absence of increased intracranial pressure. Weaning from the mechanical ventilation should be initiated as soon as possible, although the role of neurological status in the weaning process is not clear. Prevention of pneumonia and aspiration improves survival. In patients with difficult weaning, early bedside percutaneous tracheostomy should be considered.

FURTHER INVESTIGATIONS

Further studies are warranted to elucidate an optimal oxygenation and ventilation in brain-injured patients, weaning strategies, predictors of the failed weaning and extubation, respiratory support in patients with difficulties to wean, and early tracheostomy.

Prediction of symptomatic cerebral vasospasm in patients with aneurysmal subarachnoid hemorrhage: relationship to cerebral salt wasting syndrome

OBJECTIVES

Symptomatic cerebral vasospasm is a major complication in patients with subarachnoid hemorrhage (SAH). Symptomatic cerebral vasospasm has been reported to be related to the patient's blood volume which is influenced by cerebral salt wasting syndrome (CSWS). We undertook a prospective study to assess whether the onset of symptomatic cerebral vasospasm was predictable or not, by observing the phenomena of CSWS (natriuresis and osmotic diuresis).

METHODS

Sixty-seven consecutive aneurysmal SAH patients were analysed. After surgery, all patients underwent hypervolemic therapy in order to keep central venous pressure (CVP) within 8-12 cmH(2)O, serum sodium level above 140 mEq/l and a positive water balance. Patients were classified into two groups: those without symptomatic cerebral vasospasm (n=55) and those with symptomatic cerebral vasospasm (n=12). To estimate natriuresis and osmotic diuresis, sodium in/out, water in/out, CVP and other parameters were measured and compared between the two groups.

RESULTS

One day before symptomatic cerebral vasospasm, three factors reached statistical difference in the group that experienced symptomatic cerebral vasospasm: sodium balance, urine volume and water balance. On the day of symptomatic cerebral vasospasm, two factors reached statistical difference: sodium excretion and urine volume. No factor was significantly different 2 days before symptomatic cerebral vasospasm.

DISCUSSION

Symptomatic cerebral vasospasm has a strong relationship with CSWS. Negative sodium and water balance and increased urine volume indicate a predictor of symptomatic cerebral vasospasm. To predict symptomatic cerebral vasospasm, strict observations are required, because CSWS and symptomatic cerebral vasospasm which follows, develop rapidly.

Plasmatic B-type natriuretic peptide and C-reactive protein in hyperacute stroke as markers of CT-evidence of brain edema

OBJECTIVE

Plasmatic B-type-natriuretic peptide (NT-PBNP) and C-reactive protein (CRP) have been reportedly elevated in stroke patients; however their clinical significance remains uncertain. The purpose of this work is to investigate whether elevation of these proteins at baseline predicts CT-evidence of brain edema.

METHODS

We recruited 41 consecutive patients with stroke and determined NT-PBNP and CRP at baseline (within 5 hours after onset), after 48-72 hours, and at discharge. Stroke severity was measured by means of the NIHS scale at baseline and at discharge. We also carried out brain CT at admittance and after 48 hours.

RESULTS

There were 29 ischemic strokes and 12 hemorrhagic strokes. Evidence of brain edema on delayed scan was seen in 14 patients. Baseline levels of NT-PBNP did not predict CT-evidence of edema but CRP levels did so significantly (0.7 mg/dl in patients without edema versus 4.7 mg in patients with edema; p=0.001). Both NT-PBNP and PC levels correlated poorly to NIHSS score and increased markedly from baseline to the second determination in patients with edema. For these patients the NT-PBNP increase was 133.6 pmol/l in comparison to 1.58 pmol/l in patients without edema (p=0.002). Neither CRP nor NT-PBNP baseline levels were predictive of dependency or death.

CONCLUSIONS

We conclude that CRP at baseline but not NT-PBNP predicts CT evidence of brain edema in stroke patients. We hypothesize that NT-PBNP levels elevated in response to edema after 48 hours of admission.

[Aneurysmal subarachnoid hemorrhage. Significance and complications]

Despite substantial improvement in the management of patients with aneurysmal subarachnoid hemorrhage (SAH), including early aneurysm occlusion by endovascular techniques and surgical procedures, a significant percentage of patients with SAH still experience serious sequelae of neurological or cognitive deficits as a result of primary hemorrhage and/or secondary brain damage. Available neuromonitoring methods for early recognition of ischemia include, among others, measurement of brain tissue O(2) partial pressure, brain metabolism with microdialysis and monitoring of regional blood flow. The triple-H therapy (arterial hypertension, hypervolemia and hemodilution) is the treatment of choice of a symptomatic vasospasm and leads to an enduring recession of ischemic symptoms, if initiated early after the onset of a vasospasm-linked ischemic neurological deficit. Further promising therapy approaches are the administration of highly selective ET(A) receptor antagonists and intracisternal administration of vasodilators in depot form. This review summarizes the major neurological and non-neurological complications following aneurysm occlusion. Possible neuromonitoring techniques to improve diagnosis and therapy for treatment of symptomatic vasospasm as well as extracranial complications are discussed.

Relationship between serum sodium level and brain ventricle size after aneurysmal subarachnoid hemorrhage

OBJECTIVE

To study the relationship of serum sodium levels and brain ventricle size after aneurysmal subarachnoid hemorrhage (SAH).

METHODS

Serum sodium levels and brain computed tomography (CT) scans were obtained simultaneously and within 21 days from onset of SAH in 69 patients. Serum sodium levels were compared with brain ventricle size on CT. The index of third ventricle was calculated from brain CT, and we studied its relationship to GOS (Glasgow Outcome Scale) scores.

RESULTS

There was obvious correlation between serum sodium levels and index of third ventricle (r = -0.753). GOS scores correlated with serum sodium levels in patients with hypernatremia.

CONCLUSION

There was a negative correlation between serum sodium levels and cerebral ventricle size in SAH patients. Hypernatremia is one factor leading an unfavorable prognosis in SAH patients.

The systemic implications of aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is analogous to a pathophysiological watershed, disrupting brain integrity and function and precipitating an array of systemic derangements including cardiovascular, respiratory, endocrine, hematological, and immune dysfunction. Extracerebral organ dysfunction is closely linked to the magnitude of the primary neurological insult, suggesting neurogenic, neuroendocrine and neuroimmunomodulatory mechanisms. Systemic organ involvement is associated with increased mortality and neurological impairment, even after adjustment for other outcome predictors such as the severity of the initial neurological injury. This may be a reflection of secondary brain injury precipitated by hypoxemia, circulatory failure, fever, or hyperglycemia, all of which have been linked to adverse clinical outcomes. Interventions to avert or reverse these and other perturbations need to be tested in clinical trials as they represent opportunities to improve survival and neurological recovery in patients with SAH.

[Cerebral salt wasting syndrome: experimental study in rats]

INTRODUCTION

The cerebral salt wasting syndrome (CSWS) is characterized by hyponatraemia secondary to excessive natriuesis with osmotic duiresis. This syndrome, frequently, occurs after subarachnoid haemorrhage (SAH), but may occur after any acute cerebral aggression.

OBJECTIVES

The aim of the study was to assess the frequency of the CSWS in animal models with, SAH, cerebral ischemia (CI), and cranial trauma (CT), and its correlation with the secretion of brain natriuretic peptide (BNP).

METHOD

Four groups of rats were selected: group SAH (n=7) consisted of SAH induced by perforation of the carotid artery in its intracerebral part; group CI (n=7) consisted of CI induced by ligature of the carotid artery; group CT (n=7) consisted of induced CT; and a control group Sham (n=7). Weight, serum sodium, BNP, and urinary sodium, were measured at baseline and 24 hours after.

RESULTS

Rats with SAH had significant natriuresis and diuresis with negative sodium balance (-95.9+/-447.4 mumol) with a significant difference (P<0.05) compared to the rats of the CI and the Sham groups. There was no difference in the 24 hours level of BNP between the four different groups.

CONCLUSION

We conclude that SAH, in animal models, induced high diuresis with negative sodium balance in the first 24 hours. These findings were absents in the others groups. This was independent of the BNP secretion and may correspond to the early occurrence of a CSWS.

Hyponatremia and Comparison of NT-pro-BNP Concentrations in Blood Samples from Jugular Bulb and Arterial Sites after Traumatic Brain Injury in Adults: A Pilot Study

BACKGROUND

Hyponatremia after traumatic brain injury (TBI) may influence neurological function and treatment. A causal relationship between elevated serum concentrations of Type B natriuretic peptide (BNP) and hyponatremia has been implied after subarachnoid hemorrhage and other neurosurgical disorders, although the source of BNP has not been identified. We evaluated if hyponatremia and increased BNP occur after TBI and if BNP is produced/released by the brain within 24 h after injury.

RESULTS

NT-proBNP was measured in concomitant jugular venous and arterial blood samples within 24 h after TBI. NT-proBNP was elevated in both samples in six patients (24%). One patient (4%) showed an increased jugular NT-proBNP concentration above a normal arterial concentration, suggesting a brain source. In the other 24 patients the difference between jugular and arterial NT-proBNP was not statistically significant. Hyponatremia (< or =136 mEq/l) also occurred in six patients (24%), but only two (8%) had both increased arterial NT-proBNP and hyponatremia. In both the urine sodium was slightly elevated above normal, but not statistically different from other patients. The difference in serum sodium between hypo- and normo-natremic groups was significant, but mean NT-proBNP and jugular:arterial NT-proBNP differences were not.

CONCLUSIONS

In this pilot study BNP is elevated within 24 h after TBI in some patients. However, it does not originate from the brain and increased NT-proBNP concentrations are not consistently associated with hyponatremia or increased urinary sodium loss.

Hyponatremia: clinical diagnosis and management

Hyponatremia is a common clinical problem in hospitalized patients and nursing home residents. It also may occur in healthy athletes after endurance exercise. The majority of patients with hyponatremia are asymptomatic and do not require immediate correction of hyponatremia. Symptomatic hyponatremia is a medical emergency requiring rapid correction to prevent the worsening of brain edema. How fast we should increase the serum sodium levels depends on the onset of hyponatremia and still remains controversial. If the serum sodium levels are corrected too rapidly, patients may develop central pontine myelinolysis, but if they are corrected too slowly, patients may die of brain herniation. We review the epidemiology and mechanisms of hyponatremia, the sensitivity of women to hyponatremic injury, the adaptation and maladaptation of brain cells to hyponatremia and its correction, and the practical ways of managing hyponatremia. Because the majority of hyponatremia is caused by the non-osmotic release of vasopressin, the recent approval of the vasopressin receptor antagonist conivaptan for euvolemic hyponatremia may simplify hyponatremia management. However, physicians should be aware of the risk of rapid correction of hyponatremia, hypotension, and excessive fluid intake.

Cardiovascular predictors of in-patient mortality after subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Whether cardiac dysfunction contributes to morbidity and mortality after subarachnoid hemorrhage (SAH) remains controversial. The objective of this study was to test the hypothesis that cardiovascular abnormalities are independently related to in-patient mortality after SAH.

METHODS

This was a prospective cohort study of patients with aneurysmal SAH. Heart rate and blood pressure were measured, a blood sample was obtained, and echocardiography was performed on three study days, starting as soon after admission as possible. The cardiovascular predictor variables were heart rate, systolic blood pressure (SBP), cardiac troponin I (cTi) level, B-type natriuretic peptide (BNP) level, and left ventricular ejection fraction. The primary outcome measure was in-patient mortality. The association between each predictor variable and mortality was quantified by multivariate logistic regression, including relevant covariates and reporting odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

The study included 300 patients. An initial BNP level greater than 600 pg/mL was markedly associated with death (OR 37.7, p < 0.001). On the third study day (9.1 +/- 4.1 days after SAH symptom onset), a cTi level greater than 0.3 mg/L (OR 7.6, p = 0.002), a heart rate of 100 bpm or greater (OR 4.9, p = 0.009), and a SBP less than 130 mmHg (OR 6.7, p = 0.007) were significantly associated with death.

CONCLUSIONS

Cardiovascular abnormalities are independent predictors of in-patient mortality after SAH. Though these effects may be explained by a reduction in cerebral perfusion pressure or other mechanisms, further research is required to determine whether or not they are causal in nature.

Neurocardiogenic injury in neurovascular disorders

cardiac injury occurs frequently after stroke; and the most widely investigated form of neurocardiogenic injury is aneurysmal subarachnoid hemorrhage. Echocardiography and screening for elevated troponin and B-type natriuretic peptide levels may help prognosticate and guide treatment of stroke. Cardiac catheterization is not routinely recommended in subarachnoid hemorrhage patients with left ventricular dysfunction and elevated troponin. The priority should be treatment of the underlying neurologic condition, even in patients with left ventricular dysfunction. Cardiac injury that occurs after subarachnoid hemorrhage appears to be reversible. In contrast to subarachnoid hemorrhage patients, patients with ischemic stroke are more likely to have concomitant significant heart disease. For patients who develop brain death, cardiac evaluation under optimal conditions may help increase the organ donor pool.

Vasospasm in aneurysmal subarachnoid hemorrhage: diagnosis, prevention, and management

Cerebral vasospasm is a major cause of morbidity and mortality associated with subarachnoid hemorrhage (SAH). Advances in neuroimaging and development of newer intraparenchymal monitoring devices have improved the prediction and diagnosis of cerebral vasospasm significantly. Recent experimental and clinical trials have increased the armamentarium of preventive and treatment strategies for cerebral vasospasm. Vasospasm refractory to medical therapy usually is treated endovascularly with percutaneous transluminal balloon angioplasty (PTA) for proximal vessel vasospasm and vasodilator infusion for distal vessel vasospasm. Although vasospasm usually does not recur after PTA, recurrence is frequent after vasodilator infusion. The development of newer microballoon catheters has led to improvements in treatment of not only proximal but also distal vessel vasospasm with balloon angioplasty. This article reports on current knowledge in the diagnosis, prediction, prevention, and management of cerebral vasospasm.

Fludrocortisone therapy in cerebral salt wasting

Cerebral salt wasting is an increasingly recognized condition in pediatrics and is characterized by inappropriate natriuresis and volume contraction in the presence of cerebral pathology. Diagnosis can be difficult and therapy challenging. A few single case reports of the successful use of fludrocortisone exist. We report 4 patients with cerebral salt wasting, all of whom presented with hyponatremia in the presence of known intracerebral pathology. All had clinically significant hyponatremia, and 3 had hyponatremic seizures. Two of the patients also satisfied clinical criteria for diabetes insipidus. They all were treated with regimens using increased sodium and fluid administration but experienced ongoing salt wasting. Fludrocortisone was instituted in all 4 patients and in 3 resulted in rapid improvement in net sodium balance, enabling the weaning of hypertonic fluids and stabilization of serum electrolytes. In 3 patients, fludrocortisone treatment was complicated by hypokalemia, and in 1 patient by hypertension, which necessitated a dose reduction or brief cessation of therapy. Duration of therapy was 4 to 125 days. Cerebral salt wasting presents considerable management challenges; however, fludrocortisone therapy can be an effective adjunct to treatment.

Medical complications after subarachnoid hemorrhage: new strategies for prevention and management

PURPOSE OF REVIEW

To summarize new concepts regarding the occurrence, prevention, and management of medical complications following subarachnoid hemorrhage.

RECENT FINDINGS

Data regarding the impact of common medical complications after subarachnoid hemorrhage on delayed cerebral ischemia and neurological outcome after subarachnoid hemorrhage are available from recent outcomes studies. Fever, anemia requiring transfusion, hyperglycemia, electrolyte abnormalities, pneumonia, hypertension, and neurogenic stunned myocardium and pulmonary edema occur frequently after subarachnoid hemorrhage. Fever, anemia, hyperglycemia, and acute hypoxia and hypotension related to neurogenic stunned myocardium have the greatest impact on mortality and functional outcome after subarachnoid hemorrhage. Potential treatment interventions for these complications include the development of acute resuscitation strategies to optimize cerebral perfusion in poor-grade patients, maintaining normothermia with systemic cooling devices, administration of erythropoietin to prevent severe anemia, preserving normoglycemia with continuous insulin infusions, and goal-directed hemodynamic support guided by brain tissue oxygenation.

SUMMARY

Clinical trials to investigate interventions targeted at preventing or treating common medical complications after subarachnoid hemorrhage are needed.

Hyponatremia in the neurosurgical patient: epidemiology, pathophysiology, diagnosis, and management

OBJECTIVE

Hyponatremia is an important and common electrolyte disorder in critically ill neurosurgical patients that has been reported in association with a number of different primary diagnoses. The correct diagnosis of the pathophysiological cause is vital because it dramatically alters the treatment approach.

METHODS

We review the epidemiology and presentation of patients with hyponatremia, the pathophysiology of the disorder with respect to sodium and fluid balance, and the diagnostic procedures for determining the correct cause.

RESULTS

We then present the various treatment options, including discussion of one of the newest groups of agents, the arginine vasopressin receptor antagonists, currently under study for the treatment of hyponatremia in neurosurgical patients.

CONCLUSION

Hyponatremia is a serious comorbidity in neurosurgical patients that requires particular attention as its treatment varies by cause and its consequences can affect neurological outcome.

Alteration in brain natriuretic peptide (BNP) plasma concentration following severe traumatic brain injury

BACKGROUND

Brain natriuretic peptide (BNP) is a potent natriuretic and vasodilator factor which, by its systemic effects, can decrease cerebral blood flow (CBF). In aneurysmal subarchnoid hemorrhage (aSAH), BNP plasma concentrations were found to be associated with hyponatremia and were progressively elevated in patients who eventually developed delayed ischemic deficit secondary to vasospasm. The purpose of the present study was to evaluate trends in BNP plasma concentrations during the acute phase following severe (traumatic brain injury) TBI.

METHODS

BNP plasma concentration was evaluated in 30 patients with severe isolated head injury (GCS<8 on admission) in four time periods after the injury (period 1: days 1-2; period 2: days 4-5; period 3: days 7-8; period 4: days 10-11). All patients were monitored for ICP during the first week after the injury.

FINDINGS

The initial BNP plasma concentrations (42+/-36.9 pg/ml) were 7.3 fold (p<0.01) higher in TBI patients as compared to the control group (5.78+/-1.90 pg/ml). BNP plasma concentrations were progressively elevated through days 7-8 after the injury in patients with diffused SAH as compared to patients with mild or no SAH (p<0.001) and in patients with elevated ICP as compared to patients without elevated ICP (p<0.001). Furthermore, trends in BNP plasma concentrations were significantly and positively associated with poor outcome.

INTERPRETATION

BNP plasma concentrations are elevated shortly after head injury and are continuously elevated during the acute phase in patients with more extensive SAH and in those with elevated ICP, and correlate with poor outcomes. Further studies should be undertaken to evaluate the role of BNP in TBI pathophysiology.