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

Sodium and Its Impact on Outcome After Aneurysmal Subarachnoid Hemorrhage in Patients With and Without Delayed Cerebral Ischemia

OBJECTIVES

To perform a detailed examination of sodium levels, hyponatremia and sodium fluctuations, and their association with delayed cerebral ischemia (DCI) and poor outcome after aneurysmal subarachnoid hemorrhage (aSAH).

DESIGN

An observational cohort study from a prospective SAH Registry.

SETTING

Tertiary referral center focused on SAH treatment in the Amsterdam metropolitan area.

PATIENTS

A total of 964 adult patients with confirmed aSAH were included between 2011 and 2021.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 277 (29%) developed DCI. Hyponatremia occurred significantly more often in DCI patients compared with no-DCI patients (77% vs. 48%). Sodium levels, hyponatremia, hypernatremia, and sodium fluctuations did not predict DCI. However, higher sodium levels were significantly associated with poor outcome in DCI patients (DCI onset -7, DCI +0, +1, +2, +4, +5, +8, +9 d), and in no-DCI patients (postbleed day 6-10 and 12-14). Also, hypernatremia and greater sodium fluctuations were significantly associated with poor outcome in both DCI and no-DCI patients.

CONCLUSIONS

Sodium levels, hyponatremia, and sodium fluctuations were not associated with the occurrence of DCI. However, higher sodium levels, hypernatremia, and greater sodium fluctuations were associated with poor outcome after aSAH irrespective of the presence of DCI. Therefore, sodium levels, even with mild changes in levels, warrant close attention.

Prevention and Correction of Dysnatremia After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Dysnatremia occurs commonly in patients with aneurysmal subarachnoid hemorrhage (aSAH). The mechanisms for development of sodium dyshomeostasis are complex, including the cerebral salt-wasting syndrome, the syndrome of inappropriate secretion of antidiuretic hormone, diabetes insipidus. Iatrogenic occurrence of altered sodium levels plays a role, as sodium homeostasis is tightly linked to fluid and volume management.

METHODS

Narrative review of the literature.

RESULTS

Many studies have aimed to identify factors predictive of the development of dysnatremia, but data on associations between dysnatremia and demographic and clinical variables are variable. Furthermore, although a clear relationship between serum sodium serum concentrations and outcomes has not been established-poor outcomes have been associated with both hyponatremia and hypernatremia in the immediate period following aSAH and set the basis for seeking interventions to correct dysnatremia. While sodium supplementation and mineralocorticoids are frequently administered to prevent or counter natriuresis and hyponatremia, evidence to date is insufficient to gauge the effect of such treatment on outcomes.

CONCLUSIONS

In this article, we reviewed available data and provide a practical interpretation of these data as a complement to the newly issued guidelines for management of aSAH. Gaps in knowledge and future directions are discussed.

Endocrine dysregulation in aneurysmal subarachnoid haemorrhage

INTRODUCTION

Aneurysmal Subarachnoid haemorrhage (aSAH) is one of the most common causes of neurocritical care admission. Consistent evidence has been suggestive of endocrine dysregulation in aSAH. This review aims to provide an up-to-date presentation of the available evidence regarding endocrine dysregulation in aneurysmal subarachnoid haemorrhage.

METHODS

A comprehensive literature search was performed using PubMed database. All available evidence related to endocrine dysregulation in hypothalamic-pituitary hormones, adrenal hormones and natriuretic peptides after aSAH, published since 2010, were reviewed.

RESULTS

There have been reports of varying prevalence of dysregulation in hypothalamic-pituitary and adrenal hormones in aSAH. The cause of this dysregulation and its pattern remain unclear. Hypothalamic-pituitary and adrenal dysregulation have been associated with higher incidence of poor neurological outcome and increased mortality. Whilst there is evidence that long-term dysregulation of these axes may also develop, it appears to be less frequent than the acute-phase dysregulation and transient in pattern. Increased levels of catecholamines have been reported in the hyper-acute phase of aSAH with reported inconsistent correlation with the outcomes and the complications of the disease. There is growing evidence that of a causal link between the endocrine dysregulation and the development of hyponatraemia and delayed cerebral ischaemia, in the acute phase of aSAH. However, the pathophysiological mechanism and pattern of endocrine dysregulation which could be causally associated with these complications still remain debatable.

CONCLUSION

The evidence, mainly from small observational and heterogeneous in methodology studies, is suggestive of adverse effects of the endocrine dysregulation on the outcome and the incidence of complications of the disease. However, the cause of this dysregulation and a pathophysiological mechanism that could link its presence with the development of acute complications and the outcome of the aSAH remain unclear. Further research is warranted to elucidate the clinical significance of endocrine dysregulation in subarachnoid haemorrhage.

Temporal Relationship between Hyponatremia and Development of Cerebral Vasospasm in Aneurysmal Subarachnoid Hemorrhage Patients: A Retrospective Observational Study

BACKGROUND

Hyponatremia is a common complication after aneurysmal subarachnoid hemorrhage (aSAH). Previous studies have reported an association between hyponatremia and vasospasm, however whether hyponatremia directly contributes to the pathogenesis of cerebral vasospasm (CVS), or is a by-product is still unclear. The aim of this study was to explore an association between hyponatremia and CVS after aSAH, and evaluating the temporality of these 2 events.

METHODS

A retrospective study of consecutive patients with aSAH admitted to the Baylor St. Luke's Medical center between January 2008 and December 2012 was conducted. Demographics, baseline characteristics, serum sodium levels, and evidence of vasospasm detected by transcranial Doppler, CT Angiogram, MR angiogram, and digital subtracted angiography were collected. Patients were dichotomized into a hyponatremic and a normonatremic group. CVS incidence and clinical outcome was compared between groups. Timing of CVS after initial hyponatremia episodes was recorded Results: One hundred and sixty 4 patients with aSAH were included. Hyponatremia was identified in 66 patients (40.2%) and CVS occurred in 71 subjects (43.2%). The incidence of CVS was higher in the hyponatremic group compared to the normonatremic group, 65.1 % versus 28.5%, respectively (P < .001). Hyponatremia preceded CVS by median 1.5 days suggesting a temporal trend.

CONCLUSIONS

Our study shows a significant association between hyponatremia and CVS, with hyponatremia preceding CVS events. This retrospective finding denotes the need for larger prospective studies, aiming to clarify the temporal relationship of serum sodium levels and CVS.

Significance of fluctuations in serum sodium levels following aneurysmal subarachnoid hemorrhage: an exploratory analysis

OBJECTIVE

Fluctuations in patient serum sodium levels are common after aneurysmal subarachnoid hemorrhage (aSAH), but their effect on patient outcome is not well described in the literature. The goal of this work was to better characterize the relationship between fluctuations in serum sodium levels, outcome, and the development of delayed cerebral ischemia (DCI) after aSAH.

METHODS

The authors performed a post hoc analysis of data from the Clazosentan to Overcome Neurological Ischemia and Infarction Occurring After Subarachnoid Hemorrhage (CONSCIOUS-1) trial. Patients had their serum sodium values recorded daily for 14 days post-aSAH. Average and average absolute daily differences in sodium levels were calculated for each patient based on 3 reference points: admission sodium levels, a normal sodium level (defined as 140 mmol/L), and the previous day's sodium level. These variables were also calculated for the classic "vasospasm window" (days 3-12) post-aSAH. A stepwise logistic regression model, locally weighted scatterplot smoothing curves, and receiver operator characteristic curve analysis were used to evaluate the relationship between alterations in serum sodium levels and clinical outcome or the development of DCI after aSAH. Poor outcome was defined as a modified Rankin Scale (mRS) score of > 2 at 3 months.

RESULTS

The average daily difference in sodium values from baseline (p < 0.001), average daily difference from a normal sodium level (p < 0.001), average absolute daily difference from a normal sodium level (p = 0.015), and average absolute daily difference from the previous day's sodium level (p = 0.017) were significant predictors of poor outcome in a stepwise multivariate regression model. There was a trend toward significance for average absolute daily difference from admission sodium levels during the vasospasm window as an independent predictor of DCI (p = 0.052). There was no difference in the predictive capacity for DCI when sodium fluctuations from post-aSAH days 1-14 were compared with those from the classic vasospasm window (days 3-12).

CONCLUSIONS

Fluctuations in serum sodium levels may play a role in clinical outcome and the development of DCI after aSAH. The timing of these fluctuations appears to have no significant effect on the development of DCI.

Hyponatremia After Spontaneous Aneurysmal Subarachnoid Hemorrhage-A Prospective Observational Study

OBJECTIVE

Hyponatremia has been frequently observed after aneurysmal subarachnoid hemorrhage (SAH), and some data have suggested a correlation with symptomatic cerebral vasospasm and poor outcomes. The present prospective study investigated sodium and water disturbances after aneurysmal SAH with regard to symptomatic vasospasm and patient outcomes.

METHODS

Data from all patients with aneurysmal SAH treated in our department during a 2-year period were collected. Daily natriuresis, sodium levels, water balance, and serum and urine osmolality were measured at 4 different points: day 1 of admission or bleeding, day 3, day 7, and day 14-21 or discharge. The clinical parameters (i.e., Hunt and Hess grade, aneurysm location and treatment, onset of vasospasm) were reviewed. The patients' outcome was assessed using the Glasgow outcome score and modified Rankin scale.

RESULTS

A total of 101 patients (70 women; median age, 52 years) were enrolled in the present study. Of these 101 patients, 59.4% had a good grade SAH (Hunt and Hess grade 1-3). The most common aneurysm location was the anterior communicating artery (37%). The results from an electrolyte analysis were available for ≤91 patients at days 1 and 78 at discharge. In 33 patients (32.7%), hyponatremia had been diagnosed at any time point. Hyponatremia was most frequently observed at day 1 and later at days 7-10. A location in the anterior communicating artery resulted in hyponatremia more frequently only at day 1 (P = 0.007). The main causes of hyponatremia were cerebral salt-wasting syndrome (early onset) and syndrome of inappropriate antidiuretic hormone secretion (early and late onset).

CONCLUSION

Distinguishing early- and late-onset hyponatremia is of major relevance, because different therapeutic approaches are required. Only hyponatremia at discharge resulted in less favorable outcomes.

Target Serum Sodium Levels During Intensive Care Unit Management of Aneurysmal Subarachnoid Hemorrhage

INTRODUCTION

Dysnatremia commonly occur in the intensive care unit (ICU) management of patients with aneurysmal subarachnoid hemorrhage (SAH). However, detailed management strategies have not been provided even by current guidelines. The purposes of this study were to examine the association of abnormal serum sodium levels with unfavorable neurologic outcomes and to identify the target range of serum sodium in patients with SAH.

METHODS

We retrospectively reviewed all patients who were consecutively hospitalized with a confirmed diagnosis of SAH between January 2009 and December 2015. Univariate/multivariate analyses were performed to identify the independent predictors of an unfavorable neurologic outcome (modified Rankin scale of 3-6 upon hospital discharge).

RESULTS

There were 131 patients included in this study. Unfavorable neurologic outcomes occurred in 45% of patients. On multiple regression analysis, age, Hunt and Kosnik grade, and serum sodium levels in the ICU at the maximum [odds ratio (OR), 1.18; 95% CI, 1.05-1.35; P < 0.01] and minimum (OR, 0.88; 95% CI, 0.77-0.99; P = 0.048) values were significantly associated with unfavorable neurologic outcomes. The receiver operating characteristic curve analysis showed that the cut-off serum sodium levels were 145 mmol/L for maximum value and 132 mmol/L for minimum value. Patients with hyponatremia and hypernatremia during the first 2 weeks in the ICU accounted for 88.2% of patients with an unfavorable neurologic outcome; whereas, those with normal sodium levels accounted for only 15.6%.

CONCLUSIONS

In patients with SAH, both hyponatremia and hypernatremia during ICU management were significantly associated with unfavorable neurologic outcomes.

Diagnosis and Treatment of Cerebral Salt Wasting Syndrome With Cryptococcal Meningitis in HIV Patient

Hyponatremia is one of the most common electrolyte imbalances in HIV patients. The differential diagnosis may include hypovolemic hyponatremia, syndrome of inappropriate antidiuretic hormone secretion (SIADH), and adrenal insufficiency. Here, we describe a case of hyponatremia secondary to cerebral salt wasting syndrome (CSWS) in an HIV patient with cryptococcal meningitis. A 52-year-old man with a history of diabetes and HIV was admitted for headache and found to have cryptococcal meningitis. He was also found to have asymptomatic hyponatremia. He had signs of hypovolemia, such as orthostatic hypotension, dry mucosa, decreased skin turgor, hemoconcentration, contraction alkalosis, and high BUN/Cr ratio. The laboratory findings revealed sodium of 125 mmol/L, potassium of 5.5 mmol/L, urine osmolality of 522 mOsm/kg, urine sodium of 162 mmol/L, and urine chloride of 162 mmol/L. We started normal saline for hypovolemia, each 1 L prior and after amphotericin therapy. However, hypovolemia did not improve significantly despite IV fluid. Cosyntropin stimulation test was negative, and renin level was 0.25 ng·mL·h, with the aldosterone level of <1 ng/dL, the serum brain natriuretic peptide of 15 pg/mL, and serum uric acid of 2.8 mg/dL. The diagnosis of CSWS was suspected, fludrocortisone was tried, and hypovolemia and hyponatremia improved. Cryptococcal meningitis in HIV patients can present with CSWS, and the distinction between CSWS and SIADH is important because the treatment for CSWS is different than that of SIADH. Both share a similar clinical picture except that CSWS presents with constant hypovolemia despite volume replacement. Salt tablets, normal saline, or fludrocortisone can be used for treatment.

Polyuria and cerebral vasospasm after aneurysmal subarachnoid hemorrhage

Background

Natriuresis with polyuria is common after aneurysmal subarachnoid hemorrhage (aSAH). Previous studies have shown an increased risk of symptomatic cerebral vasospasm or delayed cerebral ischemia (DCI) in patients with hyponatremia and/or the cerebral salt wasting syndrome (CSW). However, natriuresis may occur in the absence of hyponatremia or hypovolemia and it is not known whether the increase in DCI in patients with CSW is secondary to a concomitant hypovolemia or because the physiology that predisposes to natriuretic peptide release also predisposes to cerebral vasospasm. Therefore, we investigated whether polyuria per se was associated with vasospasm and whether a temporal relationship existed.

Methods

A retrospective review of patients with aSAH was performed. Exclusion criteria were admission more than 48 h after aneurysmal rupture, death within 5 days, and the development of diabetes insipidus or acute renal failure. Polyuria was defined as >6 liters of urine in a 24 h period. Vasospasm was defined as a mean velocity > 120 m/s on Transcranial Doppler Ultrasonography (TCDs) or by evidence of vasospasm on computerized tomography (CT) or catheter angiography. Multivariable logistic regression was performed to assess the relationship between polyuria and vasospasm.

Results

95 patients were included in the study. 51 had cerebral vasospasm and 63 met the definition of polyuria. Patients with polyuria were significantly more likely to have vasospasm (OR 4.301, 95 % CI 1.378–13.419) in multivariate analysis. Polyuria was more common in younger patients (52 vs 68, p <.001) but did not impact mortality after controlling for age and disease severity. The timing of the development of polyuria was clustered around the diagnosis of vasospasm and patients with polyuria developed vasospasm faster than those without polyuria.

Conclusions

Polyuria is common after aSAH and is significantly associated with cerebral vasospasm. The development of polyuria may be temporally related to the development of vasospasm. An increase in urine volume may be a useful clinical predictor of patients at risk for vasospasm.

Impact of Hyponatremia on Morbidity, Mortality, and Complications After Aneurysmal Subarachnoid Hemorrhage: A Systematic Review

BACKGROUND

Hyponatremia is a common metabolic disturbance after aneurysmal subarachnoid hemorrhage (SAH), and it may worsen outcomes. This review aims to characterize the effect of hyponatremia on morbidity and mortality after SAH.

OBJECTIVES

We sought to determine the prevalence of hyponatremia after SAH, including in subgroups, as well as its effect on mortality and certain outcome measures, including degree of disability and duration of hospitalization.

METHODS

A search of terms "hyponatremia" and "subarachnoid hemorrhage" was performed on PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and EMBASE. Studies were included if they reported prevalence of hyponatremia and if they discussed outcomes such as mortality, duration of stay, functional outcomes (e.g., Glasgow Outcomes Scale), or incidence of complications in patients with aneurysmal SAH. Two independent researchers assessed the titles and abstracts and reviewed articles for inclusion.

RESULTS

Thirteen studies met inclusion criteria. The prevalence of at least mild hyponatremia was 859 of 2387 (36%) of patients. Hyponatremia was associated with vasospasm and duration of hospitalization, but it did not influence mortality.

CONCLUSION

Hyponatremia is common after SAH, and there is evidence that it is associated with certain poorer outcomes. Larger, prospective studies are needed to assess these findings and provide further evidence.

Mid-regional pro-atrial natriuretic peptide and the assessment of volaemic status and differential diagnosis of profound hyponatraemia

BACKGROUND

Hyponatraemia is common and its differential diagnosis and consequent therapy management is challenging. The differential diagnosis is mainly based on the routine clinical assessment of volume status, which is often misleading. Mid-regional pro-atrial natriuretic peptide (MR-proANP) is associated with extracellular and cardiac fluid volume.

METHODS

A total of 227 consecutive patients admitted to the emergency department with profound hypo-osmolar hyponatraemia (Na < 125 mmol L(-1) ) were included in this prospective multicentre observational study conducted in two tertiary centres in Switzerland. A standardized diagnostic evaluation of the underlying cause of hyponatraemia was performed, and an expert panel carefully evaluated volaemic status using clinical criteria. MR-proANP levels were compared between patients with hyponatraemia of different aetiologies and for assessment of volume status.

RESULTS

MR-proANP levels were higher in patients with hypervolaemic hyponatraemia compared to patients with hypovolaemic or euvolaemic hyponatraemia (P = 0.0002). The area under the curve (AUC) to predict an excess of extracellular fluid volume, compared to euvolaemia, was 0.73 [95% confidence interval (CI) 0.62-0.84]. Additionally, in multivariate analysis, MR-proANP remained an independent predictor of excess extracellular fluid volume after adjustment for congestive heart failure (P = 0.012). MR-proANP predicted the syndrome of inappropriate antidiuresis (SIAD) versus hypovolaemic and hypervolaemic hyponatraemia with an AUC of 0.77 (95% CI 0.69-0.84).

CONCLUSION

MR-proANP is associated with extracellular fluid volume in patients with hyponatraemia and remains an independent predictor of hypervolaemia after adjustment for congestive heart failure. MR-proANP may be a marker for discrimination between the SIAD and hypovolaemic or hypervolaemic hyponatraemia.

Hyponatremia in the neurocritical care patient: An approach based on current evidence

In the neurocritical care setting, hyponatremia is the commonest electrolyte disorder, which is associated with significant morbimortality. Cerebral salt wasting and syndrome of inappropriate antidiuretic hormone have been classically described as the 2 most frequent entities responsible of hyponatremia in neurocritical care patients. Nevertheless, to distinguish between both syndromes is usually difficult and useless as volume status is difficult to be determined, underlying pathophysiological mechanisms are still not fully understood, fluid restriction is usually contraindicated in these patients, and the first option in the therapeutic strategy is always the same: 3% hypertonic saline solution. Therefore, we definitively agree with the current concept of "cerebral salt wasting", which means that whatever is the etiology of hyponatremia, initially in neurocritical care patients the treatment will be the same: hypertonic saline solution.

Biomarkers and acute brain injuries: interest and limits

For patients presenting with acute brain injury (such as traumatic brain injury, subarachnoid haemorrhage and stroke), the diagnosis and identification of intracerebral lesions and evaluation of the severity, prognosis and treatment efficacy can be challenging. The complexity and heterogeneity of lesions after brain injury are most probably responsible for this difficulty. Patients with apparently comparable brain lesions on imaging may have different neurological outcomes or responses to therapy. In recent years, plasmatic and cerebrospinal fluid biomarkers have emerged as possible tools to distinguish between the different pathophysiological processes. This review aims to summarise the plasmatic and cerebrospinal fluid biomarkers evaluated in subarachnoid haemorrhage, traumatic brain injury and stroke, and to clarify their related interests and limits for diagnosis and prognosis. For subarachnoid haemorrhage, particular interest has been focused on the biomarkers used to predict vasospasm and cerebral ischaemia. The efficacy of biomarkers in predicting the severity and outcome of traumatic brain injury has been stressed. The very early diagnostic performance of biomarkers and their ability to discriminate ischaemic from haemorrhagic stroke were studied.

Correlations of ANP genetic polymorphisms and serum levels with ischemic stroke risk: a meta-analysis

AIMS

This meta-analysis was performed to evaluate the correlations between atrial natriuretic peptide (ANP) genetic polymorphism and its serum ANP levels with the risk of ischemic stroke.

METHODS

The PubMed, CISCOM, CINAHL, Web of Science, Google Scholar, EBSCO, Cochrane Library, and CBM databases were searched for relevant articles published before October 1st, 2013 without language restrictions. Meta-analysis was conducted using the STATA 12.0 software. Crude odds ratios (ORs) or standardized mean difference (SMD) with their 95% confidence interval (95% CI) were calculated. Twelve case-control studies that met all inclusion criteria were included in this meta-analysis. A total of 1285 patients with ischemic stroke and 1088 healthy control subjects were involved in this meta-analysis. Three common single-nucleotide polymorphisms (1837 G/A, 2238 T/C, and 664 G/A) in the ANP gene were assessed.

RESULTS

Our meta-analysis results revealed that ANP 2238 T/C polymorphism might increase the risk of ischemic stroke (C allele vs. T allele: OR=2.26, 95% CI: 1.59-3.23, p<0.001; TC+CC vs. TT: OR=2.26, 95% CI: 1.34-3.81, p=0.002; respectively). However, we found no correlations of ANP 1837 G/A and 664 G/A polymorphisms with ischemic stroke risk (all p>0.05). Furthermore, ischemic stroke patients had higher levels of serum ANP than those of healthy control subjects (SMD=3.12, 95% CI: 1.16-5.07, p=0.002). Our study revealed no publication bias in this meta-analysis (all p>0.05).

CONCLUSION

Our findings indicate that ANP genetic polymorphism and serum ANP levels may contribute to the development of ischemic stroke. Thus, the ANP genetic polymorphism and serum ANP levels could be potential biomarkers for early detection of ischemic stroke.

Risk Factors, Incidence, and Effect of Cardiac Failure and Myocardial Infarction in Aneurysmal Subarachnoid Hemorrhage Patients

BACKGROUND:

Cardiac dysfunction is a well-known complication of aneurysmal subarachnoid hemorrhage (aSAH). However, the clinical significance of cardiac complications is largely unknown.

OBJECTIVE:

To determine whether cardiac complications are independently related to outcomes and to identify potential predictors associated with these complications.

METHODS:

We extracted all hospitalizations for aSAH from the National Inpatient Sample database for years 2002 to 2009. We used generalized estimating equations to determine whether cardiac complications were associated with the patient outcomes and to evaluate potential predictors of cardiac complications.

RESULTS:

Among 53 713 cases of aSAH, there were 3609 (6.72%) and 151 (0.28%) incidences of cardiac failure (CF) and myocardial infarction (MI), respectively. The overall in-hospital mortality rate was 24.8%, whereas the mortality rate for patients with CF was 34.4% and the mortality rate for patients with MI was 29.8%. Patients who experienced CF were significantly more likely than other patients to die in the hospital (odds ratio: 1.6, 95% confidence interval: 1.47-1.68; P &lt; .001). The difference in mortality rates between MI patients and other patients, however, was not statistically significant. The generalized estimating equation model identified 7 factors that were predictive of CF: age, sex, race, primary payer, diabetes, smoker, and cardiac disease. For MI, the model identified age, race, and primary payer as significant predictors of MI.

CONCLUSION:

Our results suggest that an important association exists between cardiac complications and mortality/morbidity in aSAH patients. aSAH patients with CF appear to have a higher mortality rate, longer hospital length of stay, and higher hospitalization costs compared with those without CF.

Hyponatremia may reflect severe inflammation in children with febrile urinary tract infection

BACKGROUND

Hyponatremia is the most common electrolyte abnormality in clinical practice, but little is known about the association between febrile urinary tract infection (UTI) and hyponatremia or its significance to clinical outcomes.

METHODS

Data from 140 children with febrile UTI between 2000 and 2010 were retrospectively analyzed. Laboratory examinations [white blood cell (WBC) count, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and serum sodium concentration], renal ultrasonography, (99m)Technetium-dimercaptosuccinic acid (DMSA) scintigraphy, and voiding cystourethrogram were performed. Culture growing >50,000 colonies of one single bacterial species on a urine sample obtained by catheter or >100,000 colonies on two clean-catch samples was required to establish diagnosis of UTI.

RESULTS

In children with renal cortical defects diagnosed after DMSA scintigraphy (group 1), duration of fever was significantly longer (P = 0.038) and WBC (P = 0.047) and CRP (P < 0.0001) levels significantly higher than in those without renal cortical defects (group 2). However, serum sodium levels were significantly lower in group 1 than group 2 (135.9 ± 2.4 vs 137.4 ± 2.7 mEq/L, P = 0.007). Hyponatremia (serum sodium ≤ 135 mEq/L) was also more frequent in group 1 than in group 2 (74.1 % vs 45.3 %, P = 0.012). Serum sodium concentration was negatively correlated with WBC count (r = -0.156, P = 0.011) and CRP levels (r = -0.160, P= 0.028).

CONCLUSIONS

Our study indicates that hyponatremia may be a substantial inflammatory marker and is significantly and independently associated with the degree of inflammation in children with febrile UTI.

Hyponatremia and antidiuresis syndrome

Antidiuretic hormone (ADH), or arginine vasopressin (AVP), is primarily regulated through plasma osmolarity, as well as non-osmotic stimuli including blood volume and stress. Links between water-electrolyte and carbohydrate metabolism have also been recently demonstrated. AVP acts via the intermediary of three types of receptors: V1a, or V1, which exerts vasoconstrictive effects; pituitary gland V1b, or V3, which participates in the secretion of ACTH; and renal V2, which reduces the excretion of pure water by combining with water channels (aquaporin 2). Antidiuresis syndrome is a form of euvolaemic, hypoosmolar hyponatraemia, which is characterised by a negative free water clearance with inappropriate urine osmolality and intracellular hyper-hydration in the absence of renal, adrenal and thyroid insufficiency. Ninety percent of cases of antidiuresis syndrome occur in association with hypersecretion of vasopressin, while vasopressin is undetectable in 10% of cases. Thus the term "antidiuresis syndrome" is more appropriate than the classic name "syndrome of inappropriate ADH secretion" (SIADH). The clinical symptoms, morbidity and mortality of hyponatraemia are related to its severity, as well as to the rapidity of its onset and duration. Even in cases of moderate hyponatraemia that are considered asymptomatic, there is a very high risk of falls due to gait and attention disorders, as well as rhabdomyolysis, which increases the fracture risk. The aetiological diagnosis of hyponatraemia is based on the analysis of calculated or measured plasma osmolality (POsm), as well as blood volume (skin tenting of dehydration, oedema). Hyperglycaemia and hypertriglyceridaemia lead to hyper- and normoosmolar hyponatraemia, respectively. Salt loss of gastrointestinal, renal, cutaneous and sometimes cerebral origin is hypovolaemic, hypoosmolar hyponatraemia (skin tenting), whereas oedema is present with hypervolaemic, hypoosmolar hyponatraemia of heart failure, nephrotic syndrome and cirrhosis. Some endocrinopathies (glucocorticoid deficiency and hypothyroidism) are associated with euvolaemic, hypoosmolar hyponatraemia, which must be distinguished from SIADH. Independent of adrenal insufficiency, isolated hypoaldosteronism can also be accompanied by hypersecretion of vasopressin secondary to hypovolaemia, which responds to mineralocorticoid administration. The causes of SIADH are classic: neoplastic (notably small-cell lung cancer), iatrogenic (particularly psychoactive drugs, chemotherapy), lung and cerebral. Some causes have been recently described: familial hyponatraemia via X-linked recessive disease caused by an activating mutation of the vasopressin 2 receptor; and corticotropin insufficiency related to drug interference between some inhaled glucocorticoids and cytochrome p450 inhibitors, such as the antiretroviral drugs and itraconazole, etc. SIADH in marathon runners exposes them to a risk of hypotonic encephalopathy with fatal cerebral oedema. SIADH treatment is based on water restriction and demeclocycline. V2 receptor antagonists are still not marketed in France. These aquaretics seem effective clinically and biologically, without demonstrated improvement to date of mortality in eu- and hypervolaemic hyponatraemia. Obviously treatment of a corticotropic deficit, even subtle, should not be overlooked, as well as the introduction of fludrocortisone in isolated hypoaldosteronism and discontinuation of iatrogenic drugs.