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

Quantification of ventricular stress in univentricular hearts during early childhood using age-independent zlog-NT-proBNP

BACKGROUND

Children with univentricular hearts (UVH) undergo up to three palliative surgical procedures to achieve complete circulatory separation (Fontan circulation). As a marker of cardiac wall stress, NT-proBNP is a promising tool to assess systemic ventricular load in these patients. However, different reference intervals (RI) apply to each stage, as NT-proBNP is highly age-dependent.

METHODS

Children undergoing systemic-to-pulmonary (SP) shunt placement (stage 1), bidirectional cavopulmonary shunt (BCPS, stage 2) or total cavopulmonary connection (TCPC, stage 3) between 2011 and 2021 with NT-proBNP measurement within 7 days before surgery were included. Furthermore, outpatients after TCPC with NT-proBNP measurement were enrolled. Biomarker levels were evaluated using its age-adjusted z-score ("zlog-NT-proBNP"; age-independent RI, -1.96 to +1.96), allowing comparison between different stages and revealing changes in systemic ventricular load independent of the marked physiological decline in RI with age.

RESULTS

Overall, 289 children (227 before, 62 after TCPC) met the eligibility criteria. Median time between blood sampling and surgery (SP shunt/BCPS/TCPC) was 2 [1-3] days and 3.2 [2.0-4.5] years after TCPC. Age-adjusted zlog-NT-proBNP levels were 3.47 [2.79-3.93] in children with native UVH (before SP shunt), 3.10 [1.89-3.58] at stage 1 (before BCPS), 1.08 [0.51-1.88] at stage 2 (before TCPC), and 1.09 [0.72-1.75] at stage 3 (after TCPC/Fontan completion). Consequently, BCPS revealed the strongest decrease (median - 2.02 logarithmized standard deviations, p < 0.001).

CONCLUSIONS

In children with UVH undergoing staged Fontan palliation, zlog-NT-proBNP is a highly promising tool for course assessment of systemic ventricular load, independent of the age-related decline in physiological NT-proBNP concentration.

BNP and NT-proBNP Concentrations in Paired cerebrospinal Fluid and Plasma Samples of Patients with Traumatic Brain Injury

BACKGROUND

The aim of this study was to investigate the secretion patterns of brain natriuretic peptide (BNP) and N-terminal-proBNP (NT-proBNP) after traumatic brain injury (TBI) and to analyze the source of them in cerebrospinal fluid (CSF).

MATERIALS AND METHODS

We synchronously measured BNP and NT-proBNP concentrations in paired CSF and plasma samples from 22 moderate to severe TBI patients and 40 healthy control patients. The CSF and/or plasma ratio of albumin (Q_Albumin) was calculated daily. The BNP and NT-proBNP levels of CSF and plasma were compared between TBI patients and control patients.

RESULTS

CSF BNP and NT-proBNP levels peaked on day 3 after injury, as did the plasma BNP and NT-proBNP levels. The CSF BNP and NT-proBNP levels in TBI patients were elevated from day 1, which was significantly higher than control group (P < 0.05 and P < 0.01, respectively). However, in plasma, only NT-proBNP levels were significantly higher than in the control group from day 2 (P < 0.05). In addition, Q_BNP, defined as CSF BNP concentration and/or plasma BNP concentration, was significantly higher in TBI patients than in the control group (P < 0.01). However, Q_Albumin remained within ranges of a mild to moderate dysfunction of blood-brain-barrier in TBI patients.

CONCLUSIONS

CSF BNP concentrations are elevated and peak on day 3 after moderate to severe TBI. CSF BNP may originate from the brain and may be a potential biomarker of TBI.

Defining New Research Questions and Protocols in the Field of Traumatic Brain Injury through Public Engagement: Preliminary Results and Review of the Literature

Traumatic brain injury (TBI) is the most common cause of death and disability in the age group below 40 years. The financial cost of loss of earnings and medical care presents a massive burden to family, society, social care, and healthcare, the cost of which is estimated at £1 billion per annum (about brain injury (online)). At present, we still lack a full understanding on the pathophysiology of TBI, and biomarkers represent the next frontier of breakthrough discoveries. Unfortunately, many tenets limit their widespread adoption. Brain tissue sampling is the mainstay of diagnosis in neuro-oncology; following on this path, we hypothesise that information gleaned from neural tissue samples obtained in TBI patients upon hospital admission may correlate with outcome data in TBI patients, enabling an early, accurate, and more comprehensive pathological classification, with the intent of guiding treatment and future research. We proposed various methods of tissue sampling at opportunistic times: two methods rely on a dedicated sample being taken; the remainder relies on tissue that would otherwise be discarded. To gauge acceptance of this, and as per the guidelines set out by the National Research Ethics Service, we conducted a survey of TBI and non-TBI patients admitted to our Trauma ward and their families. 100 responses were collected between December 2017 and July 2018, incorporating two redesigns in response to patient feedback. 75.0% of respondents said that they would consent to a brain biopsy performed at the time of insertion of an intracranial pressure (ICP) bolt. 7.0% replied negatively and 18.0% did not know. 70.0% would consent to insertion of a jugular bulb catheter to obtain paired intracranial venous samples and peripheral samples for analysis of biomarkers. Over 94.0% would consent to neural tissue from ICP probes, external ventricular drains (EVD), and lumbar drains (LD) to be salvaged, and 95.0% would consent to intraoperative samples for further analysis.

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.

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.

Natriuretic hormones in brain function

Natriuretic hormones (NH) include three groups of compounds: the natriuretic peptides (ANP, BNP and CNP), the gastrointestinal peptides (guanylin and uroguanylin), and endogenous cardiac steroids. These substances induce the kidney to excrete sodium and therefore participate in the regulation of sodium and water homeostasis, blood volume, and blood pressure (BP). In addition to their peripheral functions, these hormones act as neurotransmitters or neuromodulators in the brain. In this review, the established information on the biosynthesis, release and function of NH is discussed, with particular focus on their role in brain function. The available literature on the expression patterns of each of the NH and their receptors in the brain is summarized, followed by the evidence for their roles in modulating brain function. Although numerous open questions exist regarding this issue, the available data support the notion that NH participate in the central regulation of BP, neuroprotection, satiety, and various psychiatric conditions, including anxiety, addiction, and depressive disorders. In addition, the interactions between the different NH in the periphery and the brain are discussed.

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.

Regional clearance of amino-terminal pro-brain natriuretic peptide from human plasma

AIMS

Mechanisms for clearance of circulating amino-terminal pro-brain natriuretic peptide (NT-proBNP) remain poorly understood and are relevant to the clinical utility of NT-proBNP as a diagnostic and prognostic biomarker in cardiovascular disorders. We sought to determine site(s) of production and clearance of plasma NT-proBNP in the human circulation.

METHODS AND RESULTS

In 120 subjects undergoing clinically indicated cardiac catheterization, blood samples were collected from arterial and multiple venous sites to measure transorgan gradients of plasma NT-proBNP. Clearance of plasma NT-proBNP occurred across kidney, liver, musculoskeletal, and head and neck tissues. Proportions of calculated total body NT-proBNP clearance were 55-65% across the kidney, 20-25% across the liver, 10-15% across musculoskeletal tissue, and 5-10% across the head and neck. Renal fractional extraction of NT-proBNP was unrelated to estimated glomerular filtration rate. Transorgan gradients, reflecting both renal and extra-renal NT-proBNP degradation, were correlated across multiple clearance sites within an individual.

CONCLUSION

Plasma NT-proBNP is cleared by multiple tissues in the human circulation with approximately 55-65% of total clearance occurring in renal tissue. These data provide the first evidence for extra-glomerular clearance of NT-proBNP and suggest a common multisite clearance mechanism subject to generalized regulation. Renal NT-proBNP extraction was sustained in the face of even moderate levels of kidney dysfunction.

Plasma B-type natriuretic peptide monitoring to evaluate cardiovascular function prior to organ procurement in patients with brain death

BACKGROUND

The natriuretic peptide system plays an active role in the regulation of fluid balance and systemic vascular resistance. Assays of plasma concentrations of B-type natriuretic peptide (BNP) may have a diagnostic role in evaluating myocardial function. We present our experience with BNP monitoring to assess myocardial function after the proclamation of brain death in potential organ donors.

METHODS

After the proclamation of brain death and prior to organ donation, a plasma BNP or aminoterminal pro-BNP level was obtained. Additional information from the donor included shortening fraction (SF) or ejection fraction, central venous pressure (CVP) reading, and renal function including blood urea nitrogen and creatinine. When available, data from the pulmonary artery (PA) catheter including pulmonary capillary wedge pressure (PCWP) and cardiac index were also collected.

RESULTS

The cohort for the study included eight patients (age range: 6 months to 21 years). The diagnosis of brain death by clinical or radiological examination had been completed in all patients and the patients were scheduled for organ procurement. Myocardial contractility as assessed by echocardiogram using SF was within normal limits. The CVP varied from 7 to 12 mmHg (9 +/- 2) and the PCWP was 10-11 mmHg in the two patients who had PA catheters in place. No patient was receiving inotropic medications. In five of the six patients, the BNP value was above the upper limit of normal (100 pg x ml(-1)). In two patients, an NT-pro-BNP value was obtained and found to be higher than the upper limits of normal (450 pg x ml(-1)). All eight patients were acceptable cardiac donors and the transplanted hearts functioned without difficulty in the recipients.

CONCLUSIONS

Assays of plasma BNP concentrations have been shown to be helpful in differentiating myocardial dysfunction from primary lung disease in both the adult and pediatric population. However, our data demonstrate that mechanisms other than myocardial performance may regulate BNP levels in patients with severe central nervous system injury who progress to brain death. Our preliminary data suggest that these assays appear to be of limited value in assessing myocardial performance in this population.

Cerebral salt wasting versus SIADH: what difference?

The term cerebral salt wasting (CSW) was introduced before the syndrome of inappropriate antidiuretic hormone secretion was described in 1957. Subsequently, CSW virtually vanished, only to reappear a quarter century later in the neurosurgical literature. A valid diagnosis of CSW requires evidence of inappropriate urinary salt losses and reduced "effective arterial blood volume." With no gold standard, the reported measures of volume depletion do not stand scrutiny. We cannot tell the difference between CSW and the syndrome of inappropriate antidiuretic hormone secretion. Furthermore, the distinction does not make a difference; regardless of volume status, hyponatremia complicating intracranial disease should be treated with hypertonic saline.