The syndrome of inappropriate antidiuresis: pathophysiology, clinical management and new therapeutic options

Pain related syndrome of inappropriate antidiuretic hormone secretion in a kitten

A 2-month-old domestic shorthair kitten was presented for evaluation of weakness, gait abnormalities, and signs of pain after trauma. On admission, the patient was found laterally recumbent with obvious gait abnormalities: difficulty rising from sitting and marked unilateral left hind limb lameness. On orthopedic examination, severe pain, crepitations, and swelling of the left hind limb were detected. Results of the first diagnostic work-up were all consistent with hyponatremia, hypochloremia and a Salter-Harris type I fracture. The kitten initially received isotonic fluids, analgesia, and antiemetic treatment. Twelve hours after admission, the analgesic plan was considered insufficient, and the general patient's condition worsened, showing severe mental depression. Blood and urine samples were collected for a more in-depth diagnostic evaluation; the patient showed worsening hyponatremia (113 mmol/L; [RR: 146,2-156,2]), severe plasma hypoosmolality (218.2 mOsm/kg; [RR: 287-307 mOsm/kg]), high natriuresis (Na: 74.9 mmol/L; [RR: <40 mmol/L]), and urinary hyperosmolality (630 mOsm/kg; [RR: <150 mOsm/kg]). Based on these new clinical findings syndrome of inappropriate antidiuretic hormone (SIADH) secretion was diagnosed. Emergency treatment with hypertonic saline was then instituted, a constant rate infusion of 3% hypertonic saline infusion to increase plasma sodium was initiated and a loop diuretic, furosemide (1 mg/kg/IV), was administered at 12-hour intervals to induce diuresis. Discharge occurred 4 days after admission as the patient was clinically stable and the hyponatremia progressively resolved. To the author's knowledge this is the first report of a kitten developing pain related SIADH associated to orthopedic trauma.

Apelin and Copeptin Levels in Patients With Chronic SIAD Treated With Empagliflozin

Background

Empagliflozin increases sodium levels in patients with a chronic syndrome of inappropriate antidiuresis (SIAD), and dapagliflozin increases apelin levels in patients with diabetes mellitus. Exogenous apelin increases sodium levels in rats with SIAD. We aimed to investigate whether an increase in plasma apelin concentration may contribute to the efficacy of empagliflozin in SIAD.

Methods

Post hoc secondary analysis of a double-blind, crossover, placebo-controlled trial performed from December 2017 to August 2021 at the University Hospital Basel, Switzerland, investigating the effect of 4-week treatment with empagliflozin 25 mg/day as compared to placebo in 14 outpatients with chronic SIAD (NCT03202667). The objective was to investigate the effect of empagliflozin on plasma apelin and copeptin concentrations and their ratio.

Results

Fourteen patients, 50% female, with a median [interquartile range] age of 72 years [65-77] were analyzed. Median apelin concentration was 956 pmol/L [853, 1038] at baseline. Median [interquartile range] apelin relative changes were +11% [0.7, 21] and +8% [-5, 25] (P = .672) at the end of the placebo and empagliflozin phases, respectively. Median copeptin concentration was 2.6 [2.2, 4.5] pmol/L at baseline and had a relative change of +5 [-2. 11]% and +25% [10, 28] (P = .047) over the placebo and empagliflozin phases, respectively.

Conclusion

Empagliflozin did not lead to significant changes in apelin or the apelin/copeptin ratio in patients with chronic SIAD but led to an increase in copeptin. This suggests that the efficacy of empagliflozin in SIAD is independent of apelin and is not blunted by the adaptative increase in copeptin.

Case report: Twice-daily tolvaptan dosing regimen in a challenging case of hyponatremia due to SIAD

Background

Syndrome of inappropriate antidiuresis (SIAD) is one of the most frequent causes of euvolemic hyponatremia (serum sodium levels < 135 mEq/L) and it represents more than 35% of hyponatremia cases in hospitalized patients. It is characterized by an inappropriate vasopressin (AVP)/antidiuretic hormone (ADH) secretion, which occurs independently from effective serum osmolality or circulating volume, leading to water retention via its action on type 2 vasopressin receptor in the distal renal tubules. Corpus callosum agenesis (CCA) is one of the most common congenital brain defects, which can be associated to alterations in serum sodium levels. This report presents a rare case of chronic hyponatremia associated with SIAD in a woman with CCA, whose correction of serum sodium levels only occurred following twice-daily tolvaptan administration.

Case presentation

A 30-year-old female was admitted to our hospital for non-acute hyponatremia with dizziness, headache, distal tremors, and concentration deficits. She had profound hyponatremia (Na 121 mmol/L) with measured plasma hypo-osmolality (259 mOsm/Kg) and urinary osmolality greater than 100 mOsm/Kg (517 mOsm/Kg). She presented clinically as normovolemic. After the exclusion of other causes of normovolemic hyponatremia, such as hypothyroidism and adrenal insufficiency, a diagnosis of SIAD was established. We have ruled out paraneoplastic, inflammatory, and infectious causes, as well as ischemic events. Her medical history showed a CCA and frontal teratoma. We administered tolvaptan initially at a low dosage (15 mg once a day) with persistence of hyponatremia. Therefore, the dosage was first doubled (30 mg once a day) and then increased to 45 mg once a day with an initial improvement in serum sodium levels, although not long-lasting. We therefore tried dividing the 45 mg tolvaptan administration into two doses of 30 mg and 15 mg respectively, using an off-label treatment schedule, thus achieving long-lasting serum sodium levels in the low-normal range associated with a general clinical improvement.

Conclusions

This report underlines the importance of the correct diagnosis, management and treatment of SIAD, as well as the need for further studies about the pharmacokinetics and pharmacodynamics of vasopressin receptor antagonists.

Syndrome of Inappropriate Antidiuresis: From Pathophysiology to Management

Hyponatremia is the most common electrolyte disorder, affecting more than 15% of patients in the hospital. Syndrome of inappropriate antidiuresis (SIAD) is the most frequent cause of hypotonic hyponatremia, mediated by nonosmotic release of arginine vasopressin (AVP, previously known as antidiuretic hormone), which acts on the renal V2 receptors to promote water retention. There are a variety of underlying causes of SIAD, including malignancy, pulmonary pathology, and central nervous system pathology. In clinical practice, the etiology of hyponatremia is frequently multifactorial and the management approach may need to evolve during treatment of a single episode. It is therefore important to regularly reassess clinical status and biochemistry, while remaining alert to potential underlying etiological factors that may become more apparent during the course of treatment. In the absence of severe symptoms requiring urgent intervention, fluid restriction (FR) is widely endorsed as the first-line treatment for SIAD in current guidelines, but there is considerable controversy regarding second-line therapy in instances where FR is unsuccessful, which occurs in around half of cases. We review the epidemiology, pathophysiology, and differential diagnosis of SIAD, and summarize recent evidence for therapeutic options beyond FR, with a focus on tolvaptan, urea, and sodium-glucose cotransporter 2 inhibitors.

A Conspectus of Euvolemic Hyponatremia, Its Various Etiologies, and Treatment Modalities: A Comprehensive Review of the Literature

Hyponatremia is the most prevalent electrolyte imbalance encountered among hospitalized patients, athletes, the elderly, patients with chronic ailments, postoperative patients, and a few asymptomatic individuals. Clinical manifestations of hyponatremia can be diverse, with characteristic neurological symptoms. Depending on in-depth medical history, physical examination (including volume status assessment), laboratory investigation, and drug history, patients can be classified broadly as undergoing hypervolemic, euvolemic, or hypovolemic hyponatremia. However, patients with hypervolemic hyponatremia often present with distinctive signs such as edema or ascites, and the clinical presentation of hypovolemic and euvolemic hyponatremia poses significant challenges for clinicians. The convolution in clinical manifestations of patients is due to the varied etiologies of euvolemic hyponatremia, such as syndrome of inappropriate antidiuretic hormone secretion (SIADH), adrenocortical insufficiency, hypothyroidism, psychogenic polydipsia, different classes of drugs (chemotherapeutics, antipsychotics, antidepressants), endurance exercise events, and reset osmostat syndrome (ROS). The management of hyponatremia depends on the rate of hyponatremia onset, duration, severity of symptoms, levels of serum sodium, and underlying comorbidities. Over the last decade, the clinical understanding of hyponatremia has been scattered due to the introduction of innovative laboratory markers and new drugs. This article will be a conspectus of all the recent advancements in the field of diagnosis, investigations, management, and associations of hyponatremia, along with traditional clinical practices. Subsequently, a holistic overview has been laid out for the clinicians to better understand and identify knowledge deficiencies on this topic.

Use of the osmolal gap in diagnosing mixed physiology hyponatremia in a child with B-cell acute lymphoblastic leukemia

Hyponatremia is common among children undergoing treatment for hematologic malignancies and may be attributed to multiple underlying causes. In cases of hyponatremia due to mixed physiology, the osmolal gap, can identify pseudohyponatremia that may be masked by other causes.

Differential diagnosis between syndrome of inappropriate antidiuretic hormone secretion and cerebral/renal salt wasting syndrome in children over 1 year: proposal for a simple algorithm

Hyponatremia, especially if acute and severe, can be a life-threatening condition. Several conditions can trigger hyponatremia. In this review, we will discuss two conditions that can determine euvolemic hyponatremia: the cerebral/renal salt wasting (CRSW) syndrome and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), including the two subtypes: reset osmostat (RO) and nephrogenic syndrome of inappropriate antidiuresis (NSIAD) and their differential diagnoses. Despite the passage of over 70 years since its first description, to date, the true etiopathogenesis of CRSW syndrome, a rare cause of hypovolemic/euvolemic hyponatremia, is almost unknown. SIADH, including RO and NSIAD, is sometimes difficult to differentiate from CRSW syndrome; in its differential diagnosis, the clinical approach based on the evaluation of the extracellular volume (ECV) was proven insufficient. We therefore suggest a simple diagnostic algorithm based on the assessment of the degree of hyponatremia, urinary osmolality, and the assessment of the fraction of urate excretion (FEUa) in conditions of hyponatremia and after serum sodium correction, to be applied in children over 1 year of life.

Hyponatraemia and the syndrome of inappropriate antidiuresis (SIAD) in cancer

Hyponatraemia is a common electrolyte abnormality seen in a wide range of oncological and haematological malignancies and confers poor performance status, prolonged hospital admission and reduced overall survival, in patients with cancer. Syndrome of inappropriate antidiuresis (SIAD) is the commonest cause of hyponatraemia in malignancy and is characterised by clinical euvolaemia, low plasma osmolality and concentrated urine, with normal renal, adrenal and thyroid function. Causes of SIAD include ectopic production of vasopressin (AVP) from an underlying tumour, cancer treatments, nausea and pain. Cortisol deficiency is an important differential in the assessment of hyponatraemia, as it has an identical biochemical pattern to SIAD and is easily treatable. This is particularly relevant with the increasing use of immune checkpoint inhibitors, which can cause hypophysitis and adrenalitis, leading to cortisol deficiency. Guidelines on the management of acute, symptomatic hyponatraemia recommend 100 mL bolus of 3% saline with careful monitoring of the serum sodium to prevent overcorrection. In cases of chronic hyponatraemia, fluid restriction is recommended as first-line treatment; however, this is frequently not feasible in patients with cancer and has been shown to have limited efficacy. Vasopressin-2 receptor antagonists (vaptans) may be preferable, as they effectively increase sodium levels in SIAD and do not require fluid restriction. Active management of hyponatraemia is increasingly recognised as an important component of oncological management; correction of hyponatraemia is associated with shorter hospital stay and prolonged survival. The awareness of the impact of hyponatraemia and the positive benefits of active restoration of normonatraemia remain challenging in oncology.

Management of SIADH-related hyponatremia due to psychotropic medications - An expert consensus from the Association of Medicine and Psychiatry

OBJECTIVE

Hyponatremia is the most common electrolyte imbalance encountered in clinical practice and is associated with negative healthcare outcomes and cost. SIADH is thought to account for one third of all hyponatremia cases and is typically an insidious process. Psychotropic medications are commonly implicated in the etiology of drug induced SIADH. There is limited guidance for clinicians on management of psychotropic-induced SIADH.

METHODS

After an extensive review of the existing literature, clinical-educators from the Association of Medicine and Psychiatry developed expert consensus recommendations for management of psychotropic-induced SIADH. A risk score was proposed based on risk factors for SIADH to guide clinical decision-making.

RESULTS

SSRIs, SNRIs, antipsychotics, carbamazepine, and oxcarbazepine have moderate to high level of evidence demonstrating their association with SIADH. Evaluation for an avoidance of medications that cause hyponatremia is particularly important. Substitution with medication that is less likely to cause SIADH should be considered when appropriate. We propose an algorithmic approach to monitoring hyponatremia with SIADH and corresponding treatment depending on symptom severity.

CONCLUSIONS

The proposed algorithm can help clinicians in determining whether psychotropic medication should be stopped, reduced or substituted where SIADH is suspected with recommendations for sodium (Na+) monitoring. These recommendations preserve a role for clinical judgment in the management of hyponatremia with consideration of the risks and benefits, which may be particularly relevant for complex patients that present with medical and psychiatric comorbidities. Further studies are needed to determine whether baseline and serial Na+ monitoring reduces morbidity and mortality.

COVID-19 and dysnatremia: A comparison between COVID-19 and non-COVID-19 respiratory illness

Objective:

To investigate the occurrence of disorders of water and sodium balance in COVID-19 in our clinic.

Methods:

In this retrospective chart review, patients were included if a polymerase chain test result for SARS-CoV-2 was obtained and if at least one plasma sodium concentration measurement was obtained during the period from March to June 2020. The occurrences of hyponatremia and hypernatremia were compared between 193 SARS-CoV-2-positive and 138 SARS-CoV-2-negative patients. A χ² test was used to determine statistical significance, and the corresponding p-values were calculated.

Results:

Hypernatremia was significantly more frequently observed in COVID-19 patients, in 38% (74 of 193), versus only 8% in SARS-CoV-2-negative patients (11 of 138) (p < 0.01). Hyponatremia was observed in 34% of the included COVID-19 patients (65 of 193) versus 24% of SARS-CoV-2-negative patients (33 of 138). In 12% of all COVID-19 patients (23 of 193), both hyponatremia and hypernatremia were observed at some point during their admission. Among the non-COVID-19 patients, only 4% showed these plasma sodium concentration fluctuations (5 of 138). The mortality rate among the hospitalized COVID-19 patients was 23% (45 of 193). Correcting for double-counting, more than 71% (32 of 45) of the deceased COVID-19 patients developed dysnatremia (hyponatremia, hypernatremia or both) versus 57% (84 out of 148) of the surviving COVID-19 patients.

Conclusion:

Disorders of water and sodium balance—and especially hypernatremia—seem to be a common occurrence in COVID-19 patients. This has important implications for the treatment of COVID-19 patients.

The Role of Consecutive Plasma Copeptin Levels in the Screening of Delayed Cerebral Ischemia in Poor-Grade Subarachnoid Hemorrhage

The prognostic value of copeptin in subarachnoid hemorrhage (SAH) has been reported, but the prognosis was largely affected by the initial clinical severity. Thus, the previous studies are not very useful in predicting delayed cerebral ischemia (DCI) in poor-grade SAH patients. Here, we first investigated the feasibility of predicting DCI in poor-grade SAH based on consecutive measurements of plasma copeptin. We measured copeptin levels of 86 patients on days 1, 3, 5, 7, 9, 11, and 13 using ELISA. The primary outcome was the association between consecutive copeptin levels and DCI development. The secondary outcomes were comparison of copeptin with C-reactive protein (CRP) in predicting DCI. Additionally, we compared the prognostic value of transcranial Doppler ultrasonography (TCD) with copeptin using TCD alone to predict DCI. Increased copeptin (OR = 1.022, 95% CI: 1.008–1.037) and modified Fisher scale IV (OR = 2.841; 95% CI: 0.998–8.084) were closely related to DCI. Consecutive plasma copeptin measurements showed significant differences between DCI and non-DCI groups (p < 0.001). Higher CRP and DCI appeared to show a correlation, but it was not statistically significant. Analysis of copeptin changes with TCD appeared to predict DCI better than TCD alone with AUCROC differences of 0.072. Consecutive measurements of plasma copeptin levels facilitate the screening of DCI in poor-grade SAH patients.

Small cell carcinoma of the cervix complicated by syndrome of inappropriate antidiuretic hormone secretion: a case report

Small cell carcinoma of the cervix is a rare malignant tumor in the clinical setting. Clinical manifestations of this tumor are mostly similar to those of normal types of cervical cancer. Small cell carcinoma of the cervix only shows symptoms of neuroendocrine tumors, such as syndrome of inappropriate antidiuretic hormone secretion (SIADH). Most of the hyponatremia caused by SIADH can be managed after removal of the cause. Hyponatremia is a predictor of poor prognosis and can be used as an indicator of partial recurrence. We report a case of small cell carcinoma of the cervix complicated by SIADH. Our patient presented with irregular vaginal bleeding after menopause. After one cycle of chemotherapy, there was trembling of the limbs, and a laboratory examination showed low Na⁺ and low Cl⁻ levels. After limited water intake, intravenous hypertonic saline, and intermittent diuretic treatment, the patient’s blood Na⁺ levels returned to normal. After a radical operation, the above-mentioned symptoms disappeared.

Syndrome of Inappropriate Antidiuretic Hormone in Esophageal Cancer Patient

Syndrome of inappropriate antidiuretic hormone (SIADH) is a disorder of fluid and sodium balance characterized by hypotonic hyponatremia, low plasma osmolality, and increased urine osmolality caused by excessive release of antidiuretic hormone (ADH). Malignancy is one of the most common causes of SIADH, but SIADH in esophageal carcinoma is very rarely reported. In this case report, a 74-year-old male patient of moderate differentiation of squamous cell esophageal carcinoma had a recurrent electrolyte balance disorder despite repeated corrections. The patient experienced improvement after fluid restriction and drug administration.

Comparing the Voets equation and the Adrogue-Madias equation for predicting the plasma sodium response to intravenous fluid therapy in SIADH patients

Background

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is one of the most common causes of hypotonic hyponatremia. In our previous work, we have derived a novel model (Voets equation) that can be used by clinicians to predict the effect of crystalloid intravenous fluid therapy on the plasma sodium concentration in SIADH.

Methods

In this retrospective chart review, the predictive accuracy of the Voets equation and the Adrogue-Madias equation for the plasma sodium response to crystalloid infusate was compared for fifteen plasma sodium response measurements (n = 15) in twelve SIADH patients. The medical records of these patients were accessed anonymously and none of the authors were their treating physicians. The Pearson correlation coefficient r and corresponding p-value were calculated for the predictions by the Voets model compared to the measured plasma sodium response and for the predictions by the Adrogue-Madias model compared to the measured plasma sodium response.

Results and conclusion

The presented results show that the Voets model (r = 0.94, p < 0.001) predicted the aforementioned plasma sodium response significantly more accurately than the Adrogue-Madias model (r = 0.49, p = 0.07) in SIADH patients and could therefore be a clinically useful addition to the existing prediction models.

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH): Optimal Management

Hyponatremia, defined as serum sodium concentration <135 mEq/l, is the most common electrolyte balance disorder in clinical practice. Many causes are listed, but syndrome of inappropriate antidiuretic hormone secretion (SIADH) is certainly the most relevant, mainly in oncological and hospitalized patients. In this review, the pathophysiological and clinical aspects are described in detail. Patients’ extensive medical history and structured physical and biochemical tests are considered the milestones marking the way of the SIADH management as to provide early detection and proper correction. We focused our attention on the poor prognostic role and negative effect on patient’s quality of life of SIADH-induced hyponatremia in both malignant and non-malignant settings, stressing how optimal management of this electrolyte imbalance can result in improved outcomes and lower health costs.

COVID-19 Pneumonia: An Emerging Cause of Syndrome of Inappropriate Antidiuretic Hormone

Syndrome of inappropriate antidiuretic hormone (SIADH) is the leading cause of hyponatremia. We, herein, report a case of a patient with coronavirus disease-2019 (COVID-19) who developed sudden exertional dyspnea and hypoxia and was found to be hyponatremic. A diagnosis of SIADH was made due to COVID-19 pneumonia. The patient was managed conservatively with a significant improvement during the course of hospitalization and on follow-up.

Trihexyphenidyl induced malignant hyperthermia in a patient with Parkinson's disease complicated with pneumonia: A case report

INTRODUCTION

Drug-induced fever is easy to overlook in respiratory departments. High fever is a rare side effect of trihexyphenidyl, which can be used clinically to treat Parkinson's disease. Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a group of clinical syndromes caused by various diseases, resulting in water retention and refractory hyponatremia. However, pneumonia combined with malignant hyperthermia and SIADH has rarely been reported. We describe an unusual case of malignant hyperthermia and refractory hyponatremia due to trihexyphenidyl adverse reaction.

PATIENT CONCERNS

Fifty-five-year-old male with pneumonia presented with malignant hyperthermia and refractory hyponatremia has a history of Parkinson's disease.

DIAGNOSIS

Early considerations related the described hyperthermia findings to the manifestations of pneumonia. However, the last findings were due to trihexyphenidyl adverse reaction.

INTERVENTIONS

Broad-spectrum antibiotics, oral and intravenous supplement of concentrated sodium chloride, drug, and physical cooling.

OUTCOMES

The patient survived. During the 3-month follow up, the patient was no recurrence of fever or hyponatremia.

CONCLUSION

High fever and SIADH can be a rare adverse reaction to trihexyphenidyl. Therefore, possible drug factors should be considered in the case. Consideration of other possible causes can improve early diagnosis and treatment of patients with fever of unknown origins.

Hyponatraemia and Syndrome of Inappropriate Antidiuretic Hormone Secretion in Non-azotaemic Dogs with Babesiosis Associated with Decreased Arterial Blood Pressure

Introduction

A previous study on canine babesiosis showed low serum tonicity in affected dogs, which may result from syndrome of inappropriate antidiuretic hormone secretion (SIADH). This endocrine disorder was recognised in human malaria which is considered a disease with similar pathogenesis to canine babesiosis. The aim of this study was to investigate the occurrence of SIADH in babesiosis-afflicted dogs.

Material and Methods

Serum and urinary sodium and urine specific gravity (USG) were determined in dogs with babesiosis. Mean arterial pressure (MAP) was measured at the beginning of the clinical examination. Serum tonicity and osmolality were calculated. Correlations were calculated between MAP and serum and urinary sodium concentrations, USG, serum tonicity, and calculated serum osmolality.

Results

Statistically significant correlations were observed between MAP and tonicity, calculated osmolality, USG, and serum and urinary sodium concentrations in non-azotaemic dogs. In three non-azotaemic dogs SIADH was recognised.

Conclusion

SIADH develops in non-azotaemic dogs with babesiosis. It is probably associated with decreased blood pressure in infected dogs. Thus, it seems that in fact it may be appropriate vasopressin secretion in canine babesiosis as a protective mechanism in hypotension which leads to hypoxia and renal failure in affected dogs.

Duloxetine and Angiotensin II Receptor Blocker Combination Potentially Induce Severe Hyponatremia in an Elderly Woman

We encountered a case of syndrome of inappropriate antidiuretic hormone secretion (SIADH) caused by duloxetine, serotonin and norepinephrine reuptake inhibitor (SNRI). A 74-year-old woman complaining of severe lethargy was transferred to our emergency department. Her serum sodium level was 109 mEq/L. Plasma hypo-osmolality with urine normo-osmolality was observed, indicating SIADH. Her essential hypertension had long been treated with telmisartan, and she had just started duloxetine 20 mg/day for chronic musculoskeletal pain 4 days prior to admission. On prescribing duloxetine in the primary care setting, clinicians should be aware of the possibility of duloxetine-induced hyponatremia, particularly in combination with telmisartan.

First experience with Tolvaptan for the treatment of neonates and infants with capillary leak syndrome after cardiac surgery

Background

Postoperative fluid management in critically ill neonates and infants with capillary leak syndrome (CLS) and extensive volume overload after cardiac surgery on cardiopulmonary bypass is challenging. CLS is often resistant to conventional diuretic therapy, aggravating the course of weaning from invasive ventilation, increasing length of stay on ICU and morbidity and mortality.

Methods

Tolvaptan (TLV, vasopressin type 2 receptor antagonist) was used as an additive diuretic in neonates and infants with CLS after cardiac surgery. Retrospective analysis of 25 patients with CLS including preoperative and postoperative parameters was performed. Multivariate regression analysis was performed to identify predictors for TLV response.

Results

Multivariate analysis identified urinary output during 24 h after TLV administration and mean blood pressure (BP) on day 2 of TLV treatment as predictors for TLV response (AUC = 0.956). Responder showed greater weight reduction (p < 0.0001), earlier weaning from ventilator during TLV (p = 0.0421) and shorter time in the ICU after TLV treatment (p = 0.0155). Serum sodium and serum osmolality increased significantly over time in all patients treated with TLV.

Conclusion

In neonates and infants with diuretic-refractory CLS after cardiac surgery, additional aquaretic therapy with TLV showed an increase in urinary output and reduction in bodyweight in patients classified as TLV responder. Increase in urinary output and mean BP on day 2 of treatment were strong predictors for TLV response.

Electronic supplementary material

The online version of this article (10.1186/s12887-019-1418-6) contains supplementary material, which is available to authorized users.

Chronic Hyponatremia Due to the Syndrome of Inappropriate Antidiuresis (SIAD) in an Adult Woman with Corpus Callosum Agenesis (CCA)

BACKGROUND Corpus callosum agenesis (CCA) is one of the most common congenital brain abnormalities, and is associated with neurodevelopmental and neuropsychiatric disorders. In CCA, defects in osmoregulation have been reported. This report presents a rare case of chronic hyponatremia associated with the syndrome of inappropriate antidiuresis (SIAD) in a woman with CCA. CASE REPORT A 41-year-old woman presented to the renal unit with symptomatic hyponatremia. In her past medical history, she had a four-year history of systemic arterial hypertension and Sjögren's syndrome, and a three-year history of systemic lupus erythematosus (SLE), which was treated with cyclophosphamide. She had CCA but with irregular neurological follow-up. During the previous eight years, her plasma sodium levels ranged from between 118-134 mEq/L. On this hospital admission, she had plasma hypo-osmolality, measured in milli-osmoles per kilogram of H2O (mOsm/kg H2O), of 251 mOsm/Kg H2O, and a urinary hyper-osmolality of 545 mOsm/Kg H2O, and increased level of plasma antidiuretic hormone (ADH) (1.8 pg/ml). Bone densitometry was consistent with osteoporosis. The patient remained asymptomatic during her hospital stay. Chronic hyponatremia associated with the SIAD was diagnosed. Water restriction and increased protein intake resulted in a partial improvement in the serum sodium level (128-134 mEq/L). The patient was discharged from the hospital with outpatient follow-up. CONCLUSIONS A rare case of chronic hyponatremia due to the SIAD associated with CCA is reported that demonstrates the importance of correct diagnosis, management, and clinical follow-up of the SIAD, including bone densitometry.

Influenza A: another cause of SIADH?

The syndrome of inappropriate antidiuretic hormone (SIADH) secretion is a frequent cause of hyponatraemia. It is a dilutional hyponatraemia secondary to impaired urinary dilution in the absence of renal disease or any identifiable non-osmotic stimulus known to induce antidiuretic hormone secretion. SIADH can arise secondary to various respiratory tract infections; however, the association between SIADH and influenza A infection is described in only a few cases in the literature. The authors present a case report of influenza A that may have caused a profound SIADH-related hyponatraemia.

Hyponatremia in patients with esophageal cancer treated with chemotherapy including cisplatin

BACKGROUND

Little is known about hyponatremia in patients with esophageal cancer treated with cisplatin-based chemotherapy. The aim of this study was to analyze the risk factors for hyponatremia and its effect on outcomes in patients with esophageal cancer treated with chemotherapy including cisplatin.

METHODS

We retrospectively analyzed the records of 137 patients with esophageal cancer who received chemotherapy including cisplatin for the first time between January 2011 and December 2014.

RESULTS

Hyponatremia (Na < 135 mEq/L) was seen in 77 patients (59%), of whom 29 had Grade 3 (120 ≤ Na < 130 mEq/L) or Grade 4 (Na < 120 mEq/L) hyponatremia. We divided patients into the hyponatremia group (patients with Na < 130 mEq/L) and the control group (patients with Na ≥ 130 mEq/L), and compared the results between the two groups. Three patients (2%) were diagnosed with the syndrome of inappropriate secretion of antidiuretic hormone. The serum sodium level before starting chemotherapy was significantly lower and white blood cell count was significantly higher in the hyponatremia group. Appetite loss was seen significantly more often in the hyponatremia group as the chemotherapy-related adverse effect. There was no significant difference in overall survival between the two groups.

CONCLUSIONS

Hyponatremia is a common adverse effect induced by cisplatin. Caution should be exercised with patients with a low sodium level before starting chemotherapy. Hyponatremia can be associated with other chemotherapy-related adverse effects, and it should therefore be treated correctly.

Association of copeptin, a surrogate marker of arginine vasopressin, with cerebral vasospasm and delayed ischemic neurologic deficit after aneurysmal subarachnoid hemorrhage

OBJECTIVE

Delayed ischemic neurological deficit (DIND) is a leading cause of mortality and morbidity after aneurysmal subarachnoid hemorrhage (aSAH). Arginine vasopressin (AVP) is a hormone released by the posterior pituitary. It is known to cause cerebral vasoconstriction and has been implicated in hyponatremia secondary to the syndrome of inappropriate antidiuretic hormone secretion. Direct measurement of AVP is limited by its short half-life. Copeptin, a cleavage product of the AVP precursor protein, was therefore used as a surrogate marker for AVP. This study aimed to investigate the temporal relationship between changes in copeptin concentrations and episodes of DIND and hyponatremia.

METHODS

Copeptin concentrations in cerebrospinal fluid were quantified using enzyme-linked immunosorbent assay in 19 patients: 10 patients with DIND, 6 patients without DIND (no-DIND), and 3 controls.

RESULTS

Copeptin concentrations were higher in DIND and no-DIND patients than in controls. In hyponatremic DIND patients, copeptin concentrations were higher compared with hyponatremic no-DIND patients. DIND was associated with a combination of decreasing sodium levels and increasing copeptin concentrations.

CONCLUSIONS

Increased AVP may be the unifying factor explaining the co-occurrence of hyponatremia and DIND. Future studies are indicated to investigate this relationship and the therapeutic utility of AVP antagonists in the clinical setting.

Amiodarone-Induced Hyponatremia Masked by Tolvaptan in a Patient with an Implantable Left Ventricular Assist Device

A 43-year-old man was referred to our hospital in June 2014 because of severe heart failure. He was diagnosed with familial dilated cardiomyopathy and was administered oral tolvaptan and amiodarone for atrial and ventricular tachycardia. Since up-titration of carvedilol had failed and he was dependent on dobutamine, a left ventricular assist device (LVAD) was implanted. Tolvaptan and furosemide were both discontinued after LVAD implantation and he was discharged from the hospital. Thirteen months later, he was hospitalized for lethargy and hyponatremia of 108 mEq/L, with an antidiuretic hormone level of 2.5 pg/mL, which suggested syndrome of inappropriate antidiuretic hormone secretion (SIADH). We discontinued amiodarone and administered fludrocortisones. However, hyponatremia persisted for a few more days, eventually resulting in delirium and damage to the LVAD driveline. He received an urgent pump exchange and hyponatremia was gradually improved. We considered the possibility that amiodarone-induced SIADH was masked by tolvaptan therapy before LVAD implantation.

Syndrome of Inappropriate Antidiuretic Hormone Secretion in a Patient with Mucosa-associated Lymphoid Tissue Lymphoma

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) may develop in association with several malignancies. However, as an immunohistochemical analysis is not performed in the majority cases, its true cause is often uncertain. We herein report a case of SIADH following chemotherapy due to tumor-derived ADH production in a patient with mucosa-associated lymphoid tissue (MALT) lymphoma. A retrospective immunohistochemical analysis demonstrated ADH expression by lymphoma cells. These findings highlight the importance of using an immunohistochemical analysis to determine ADH production by tumor cells in patients with SIADH. Such analyses play an important role in elucidating the pathogenesis of SIADH and determining the most appropriate treatment.

Syndrome of Inappropriate Antidiuretic Hormone Secretion in a Mini-Breed Puppy Associated With Aspiration Pneumonia

A 3-month-old intact male Prague ratter was presented to the emergency service for evaluation of progressive lethargy, weakness, coughing and labour breathing after an episode of resistance to oral deworming. The patient exhibited depression, increased respiratory effort and cyanosis at initial presentation. Results of first diagnostic work-up (complete blood cell count, biochemistry panel and thoracic x-rays) were all consistent with aspiration pneumonia. The puppy was initially treated with balanced isotonic crystalloids, broad spectrum antibiotics, nebulization with thoracic coupage and was transferred to an infant incubator with a sustained FiO2 of 40-50%. Twenty-four hours after ICU admission the patient's condition suffered a worsening and the dog was orthopneic, severely depressed with episodes of intermittent dysphoria and seizuring. New thoracic radiographs and several samples of blood and urine were collected to go further in the diagnostic workup revealing severe hyponatremia, severe plasma hypotonicity, high natriuresis and metabolic acidosis with a worsening of the radiological pulmonary pattern. Based on these new clinical findings a diagnosis of SIADH was established. Emergency treatment with hypertonic 3% saline solution and loop diuretics was started like a sodium supplement and to inhibit water resorption in renal tubules, thus reducing the volume overload. The goal of this treatment was to achieve a progressive and controlled increase of plasma sodium concentration and promoting the excretion of positive body water imbalance. The patient's condition improved clinically over the following days, treatment was progressively discontinued and the dog was discharged 7 days after admission. To the author's knowledge this is the first report of a puppy younger than 12 weeks with respiratory distress developing SIADH associated to aspiration pneumonia.

Severe cyclophosphamide-related hyponatremia in a patient with acute glomerulonephritis

Cyclophosphamide is frequently used to treat cancer, autoimmune and renal diseases, such as rapidly progressive glomerulonephritis. Its side effects are well-known, including bone marrow depression, infections, alopecia, sterility, bladder malignancy and hemorrhagic cystitis. Moreover, in some cases cyclophosphamide use has been related to the onset of hyponatremia, by development of a syndrome of inappropriate antidiuresis. Indeed, severe hyponatremia has been previously reported in patients treated with high-dose or moderate-dose of intravenous cyclophosphamide, while only few cases have been reported in patients treated with low dose. Here, we discuss a case of a syndrome of inappropriate antidiuresis followed to a single low-dose of intravenous cyclophosphamide in a patient with a histological diagnosis of acute glomerulonephritis, presenting as acute kidney injury. After cyclophosphamide administration (500 mg IV), while renal function gradually improved, the patient developed confusion and headache. Laboratory examinations showed serum sodium concentration dropped to 122 mmol per liter associated with an elevated urinary osmolality of 199 mOsm/kg, while common causes of acute hyponatremia were excluded. He was successfully treated with water restriction and hypertonic saline solution infusion with the resolution of the electrolyte disorder. This case, together with the previous ones already reported, highlights that electrolyte profile should be strictly monitored in patients undergoing cyclophosphamide therapy in order to early recognize the potentially life-threatening complications of acute water retention.

Successful Radiotherapy for Advanced Small Cell Carcinoma of the Prostate with Syndrome of Inappropriate Secretion of Antidiuretic Hormone

Small cell carcinoma of the prostate (SCCP) is rare in clinical practice. It is often accompanied with the syndrome of inappropriate antidiuretic hormone secretion (SIADH). We present a case of SCCP with SIADH that was successfully treated with radiotherapy in the metastatic lymphnodes and prostate. The patient was an 81-year-old male with a castrate-resistant prostate cancer (CRPC) with invaded rectum and multiple metastases of pelvic lymphnodes. Hyponatremia was present. After radiotherapy, serum sodium increased and neuron-specific enolase (NSE) decreased. To our knowledge, this is the first case of SCCP with SIADH treated with radiotherapy to improve hyponatremia.

Mild Lung Tuberculosis in a Patient Suffering from Status Epilepticus Caused by the Syndrome of Inappropriate Secretion of Antidiuretic Hormone (SIADH)

A 76-year-old woman was diagnosed with lung tuberculosis. On the second day of anti-tuberculosis treatment, she became unconscious and developed status epilepticus accompanied by hyponatremia. The hyponatremia was caused by the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Detailed examinations revealed that the patient's status epilepticus had occurred due to hyponatremia, which was caused by lung tuberculosis-associated SIADH. Previous case reports noted that patients with tuberculosis-associated SIADH showed mild clinical manifestations. They also reported that extensive lung involvement was associated with SIADH development. We herein report a rare case of SIADH complicated with status epilepticus that was caused by tuberculosis with mild lung involvement.

Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) associated with lateral medullary syndrome: case report and literature review

Background

Only one case of syndrome of inappropriate secretion of antidiuretic hormone with lateral medullary syndrome has been reported so far. We report a case of lateral medullary syndrome showing syndrome of inappropriate secretion of antidiuretic hormone and analyze the pathomechanism underlying its clinical features.

Case presentation

A 67-year-old man was admitted to our hospital for dizziness, dysarthria, and dysphagia. He was diagnosed with lateral medullary syndrome based on the neurological examination and brain magnetic resonance imaging. Horner syndrome was absent. Asymptomatic hyponatremia appeared 9 days after admission and the patient was diagnosed with syndrome of inappropriate secretion of antidiuretic hormone. Fluid restriction and intravenous furosemide injection improved the hyponatremia.

Conclusion

Lateral medullary syndrome could be associated with syndrome of inappropriate secretion of antidiuretic hormone.

Congenital hyperinsulinism in Chinese patients: 5-yr treatment outcome of 95 clinical cases with genetic analysis of 55 cases

AIM

The aim of this study is to investigate the clinical features, therapeutic outcomes, and genetic mutations of congenital hyperinsulinism (CHI) in Chinese patients.

METHODS

The clinical features and therapeutic outcomes of 95 CHI cases were recorded, and genetic analyses were conducted to identify mutations in ABCC8 and KCNJ11 in 55 cases. Direct sequencing was carried out in 25 of the cases with ABCC8 and KCNJ11 mutations. Additionally, 16 samples with no mutations and the remaining 30 samples were sequenced using Ion Torrent platform.

RESULTS

Clinical misdiagnosis occurred in 36/95 (38%) of the cases. Most (82/95; 84%) of the patients were given diazoxide therapy combined with age-dependent frequent feeding, which was effective in 54/95 (66%) cases. The side effects of diazoxide included sodium and water retention, gastrointestinal reactions, polytrichia, and thrombocytopenia. Five patients were treated with octreotide for 1-4 months, of which 80% (4/5) showed a positive response. Non-surgical therapy was effective in 71/95 (75%) cases. Of the four children who received subtotal pancreatectomy, only one had a good outcome. The remission rate of hypoglycemia was 59% for children over 2-yr-old. The CHI-related gene mutation rate was 38% for potassium channel-related genes. Early onset of CHI and a lower diazoxide response rate were associated with potassium-ATP channel gene mutations.

CONCLUSION

Age-dependent frequent feeding is an acceptable therapy for CHI. Non-surgical therapy may be highly effective, in part, due to the low rate of potassium channel gene mutations. Surgical outcomes are unreliable without 18F-fluoro-L-DOPA positron emission tomography. Therefore, we do not recommend operation without definitive identification of the pathologic type.

Efficacy and Safety of Vasopressin Receptor Antagonists for Euvolemic or Hypervolemic Hyponatremia: A Meta-Analysis

Hyponatremia, defined as a nonartifactual serum sodium level <135 mmol/L, is the most common fluid and electrolyte abnormality in clinical practice. Traditional managements (fluid restriction, hypertonic saline and loop diuretics, etc.) are difficult to maintain or ineffective. Recently, vasopressin receptor antagonists (VRAs) have shown promise for the treatment of hyponatremia. We aimed to conduct a meta-analysis to evaluate the efficacy and safety of VRAs in patients with euvolemic or hypervolemic hyponatremia. We searched Pubmed, Cochrane Library, Web of Science and Springer, etc. (latest search on June 4, 2015) for English publications with randomized controlled trials. Two authors independently screened the citations and extracted data. We calculated pooled relative risk (RR), risk difference (RD), weighted mean difference (WMD) or standard mean difference (SMD), and 95% confidence intervals (CIs) by using random and fixed effect models. We collected data from 18 trials involving 1806 patients. Both random and fixed effect meta-analyses showed that VRAs significantly increased the net change of serum sodium concentration (WMD(random) = 4.89 mEq/L, 95%CIs = 4.35-5.43 and WMD(fixed) = 4.70 mEq/L, 95%CIs = 4.45-4.95), response rate (RR(random )= 2.77, 95%CIs = 2.29-3.36 and RR(fixed) = 2.95, 95%CIs = 2.56-3.41), and 24-hour urine output (SMD(random) = 0.82, 95%CIs = 0.65-1.00 and SMD(fixed) = 0.79, 95%CIs = 0.66-0.93) compared to placebo. Furthermore, VRAs significantly decreased body weight (WMD(random) = -0.87 kg, 95%CIs = -1.24 to -0.49 and WMD(fixed) = -0.91 kg, 95%CIs = -1.22 to -0.59). In terms of safety, rates of drug-related adverse events (AEs), rapid sodium level correction, constipation, dry mouth, thirst, and phlebitis in the VRA-treated group were greater than those in control group. However, there was no difference in the total number of AEs, discontinuations due to AEs, serious AEs, death, headache, hypotension, nausea, anemia, hypernatremia, urinary tract infection, renal failure, pyrexia, upper gastrointestinal bleeding, diarrhea, vomiting, peripheral edema, and dizziness between the 2 groups. Random effect meta-analyses showed that post treatment urine osmolality, supine systolic blood pressure, and diastolic blood pressure were lowered (WMD(random) = -233.07 mOsmol/kg, 95%CIs = -298.20-147.94; WMD(random) = -6.11 mmHg, 95%CIs = -9.810 to -2.41; WMD(random )= -2.59 mmHg, 95%CIs = -4.06 to -1.11, respectively), but serum osmolality was increased (WMD(random) = 9.29 mOsmol/kg, 95%CIs = 5.56-13.03). There was no significant change from baseline in serum potassium concentration between the 2 groups (WMD(fixed) = 0.00 mmHg, 95%CIs = -0.07-0.06). VRAs are relatively effective and safe for the treatment of hypervolemic and euvolemic hyponatremia.

Syndrome of Inappropriate Antidiuretic Hormone Secretion: A Poor Prognosis in Small-cell Lung Cancer

BACKGROUND AND AIMS

Small cell lung cancer (SCLC) is frequently associated with syndrome of inappropriate antidiuretic hormone (SIADH) secretion. In this study we investigated the prognostic value of SIADH in Chinese patients with SCLC.

METHODS

We prospectively studied a total of 385 patients with SCLC diagnosed in our institution. The relationship between the SIADH and treatment outcomes including progression-free survival (PFS) and overall survival (OS) were analyzed. Univariate analysis and Cox multivariate analyses were used for statistical analyses. PFS and OS curves were drawn using Kaplan-Meier method.

RESULTS

The median PFS and OS in patients with SIADH was 6.7 months (95% confidence interval [CI]: 4.3-9.1) and 11.6 months (95% CI: 7.4-15.7), respectively. The corresponding PFS and OS in SCLC without SIADH was 9.2 months (95% CI: 8.6-9.8) and 19.2 months (95% CI: 16.5-21.9), respectively; the difference between groups was statistically significant (p = 0.007 and p = 0.000, respectively). The association of SIADH with poor PFS (p = 0.000) and OS (p = 0.002) retained its statistical significance after adjusting for potential confounding variables. In addition, PFS (p = 0.000) and OS (p = 0.000) of SIAHD patients with plasma sodium <125 mmol/L or without plasma sodium recovery to normal level are both shorter than in patients without SIADH. OS in SIAHD patients with plasma sodium recovery time to normal level is also shorter than patients without SIADH (p = 0.03).

CONCLUSIONS

SIADH is a common occurrence in patients with SCLC and is associated with poor prognosis for SCLC in Chinese patients.

Randomized, double blinded, placebo-controlled trial to evaluate the efficacy and safety of tolvaptan in Chinese patients with hyponatremia caused by SIADH

To study the effect of tolvaptan on non-acute, non-hypovolemic hyponatremia in inappropriate secretion of antidiuretic hormone (SIADH) syndrome in Chinese patients. Hyponatremic SIADH patients received placebo (N = 18) or tolvaptan (N = 19) at an initial dose of 15 mg/day with further titration to 30 mg/day and 60 mg/day based on serum sodium concentrations. Randomized, double-blind, placebo-controlled trial. Primary endpoint was the change of the serum sodium from baseline to days 4 and 7. Analysis of covariance (ANCOVA) was used for statistical analysis. At day 4, average daily changes in serum sodium levels from baseline was 1.9 ± 2.9 mmol/L (1.9 ± 2.9 mEq/L) in the placebo group and 8.1 ± 3.6 mmol/L (8.1 ± 3.6 mEq/L) in the tolvaptan group; at day 7, the values were 2.5 ± 3.9 mmol/L (2.5 ± 3.9 mEq/L) and 8.6 ± 3.9 mmol/L (8.6 ± 3.9 mmEq/L) for the placebo and tolvaptan groups (ANCOVA, P < 0.001). At days 4 and 7, daily urine output and proportions of patients with normalized serum sodium were significantly superior in the tolvaptan group. The most common adverse events occurring in the tolvaptan group were dry mouth and thirst. Tolvaptan demonstrated superiority to placebo in the treatment of Chinese SIADH patients with hyponatremia by elevating serum sodium concentration with acceptable safety profile.

Down with the Flu: Hyponatremia in a patient with influenza

Context:

Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a common cause of hyponatremia. Although it has been associated with different pulmonary infections, there have been only few case reports describing the association of SIADH with influenza.

Case Report:

We report a case of SIADH in a patient with influenza who was successfully treated with fluid restriction.

Conclusion:

It is essential for clinicians to be aware of the association between influenza and SIADH.

[Hyponatremias: From pathophysiology to treatments. Review for clinicians]

Hyponatremia could be defined as a public health topic: too many patients are concerned in both hospitalized and general populations; hyponatremia induces lots of clinical outcomes and a great economic burden. Its pathophysiology involves thirst regulation (hypotonic water intakes) and losses regulation (through the kidney under vasopressin control). Diagnostic approach should insure that hyponatremia reflects hypo-osmolality and hypotonicity: first, a false hyponatremia should be ruled out, then a non-hypotonic one. Next step is clinic: extracellular status should be evaluated. When increased, any edematous status should be evoked: heart failure, liver cirrhosis or nephrotic syndrome. When decreased, any cause of extracellular dehydration should be evoked: natriuresis could help distinguishing between renal (adrenal insufficiency, diuretics use or salt-losing nephropathy) or extrarenal (digestive mostly) etiologies. When clinically normal, a secretion of inappropriate antidiuretic hormone (SIADH) should be evoked, once hypothyroidism or hypoadrenocorticism have been ruled out. Therapy depends on the severity of the clinical impact. From extracellular rehydration, through fluid restriction, the paraneoplastic and heart failure-induced SIADH benefit from a new class of drug, available among the therapeutic strategies: aquaretics act through antidiuretic hormone receptor antagonism (vaptans). Their long-term benefits still have to be proven but it is a significant step forward in the treatment of hyponatremias.

Risk factors, complication and measures to prevent or reverse catastrophic sodium overcorrection in chronic hyponatremia

Hyponatremia is the most common electrolyte disorder encountered in clinical practice. Patients who develop this condition for more than 48 hours are at risk for severe neurological sequelae if correction of the serum sodium occurs too rapidly. Certain medical disorders are known to place patients at an increased risk for rapid correction of serum sodium concentration. Large-volume polyuria in this setting is an ominous sign. For these patients, early identification of risk factors, close monitoring of serum sodium correction and the use of 5% dextrose with or without desmopressin to prevent or reverse overcorrection are important components of treatment.

Syndrome of inappropriate antidiuretic hormone secretion and cerebral/renal salt wasting syndrome: similarities and differences

Hyponatremia (sodium levels of <135 mEq/L) is one of the most common electrolyte imbalances in clinical practice, especially in patients with neurologic diseases. Hyponatremia can cause cerebral edema and brain herniation; therefore, prompt diagnosis and proper treatment is important in preventing morbidity and mortality. Among various causes of hyponatremia, diagnosing syndrome of inappropriate antidiuretic hormone secretion (SIADH) and cerebral/renal salt wasting syndrome (C/RSW) is difficult due to many similarities. SIADH is caused by excess of renal water reabsorption through inappropriate antidiuretic hormone secretion, and fluid restriction is the treatment of choice. On the other hand, C/RSW is caused by natriuresis, which is followed by volume depletion and negative sodium balance and replacement of water and sodium is the mainstay of treatment. Determinating volume status in hyponatremic patients is the key point in differential between SIADH and C/RSW. However, in most situations, differential diagnosis of these two diseases is difficult because they overlap in many clinical and laboratory aspects, especially to assess differences in volume status of these patients. Although distinction between the SIADH and C/RSW is difficult, improvement of hypouricemia and an increased fractional excretion of uric acid after the correction of hyponatremia in SIADH, not in C/RSW, may be one of the helpful points in discriminating the two diseases. In this review, we compare these two diseases regarding the pathophysiologic mechanisms, diagnosis, and therapeutic point of view.

Kidney-Organ Interaction

The practice of critical care nephrology demands an intimate understanding of the interactions and “crosstalk” that occurs between the kidney and multiple organ systems, in particular the heart, lung, gut, and brain. Accumulating evidence suggests that acute injury and dysfunction to the kidney can incite and propagate cardiac, pulmonary, gastrointestinal, and neurologic injury and dysfunction through a host of mechanisms.

Syndrome of inappropriate antidiuretic hormone secretion in a cat with a putative Rathke's cleft cyst

An 11-year-old spayed female domestic shorthair cat was evaluated for anorexia, lethargy and weight loss of 6 days' duration. Bilateral mydriasis, absent menace response, slow-to-absent pupillary light reflexes, bilateral retinal detachment, intermittent horizontal nystagmus, intermittent ventral strabismus and systemic hypertension were present. Biochemical analysis revealed severe hyponatremia, severe hypochloremia and mild hypokalemia. Multifocal central nervous system disease was suspected based on optic, trigeminal sensory (ophthalmic branch), vestibulocochlear and possible oculomotor nerve dysfunction. Thoracic radiographs showed mild cardiomegaly without evidence of congestive heart failure. Ultrasound revealed mild pleural and peritoneal effusion. A cause of the severe hyponatremia was not identified, and it persisted despite fluid therapy. Syndrome of inappropriate antidiuretic hormone secretion (SIADH) was suspected as the cause of hyponatremia. Humane euthanasia was elected owing to continued clinical decline. Serum hyposmolality, urine hyperosmolality, natriuresis and lack of confirmed renal, thyroid and pulmonary disease aided in the presumed diagnosis of SIADH. Post-mortem histopathology of the brain revealed degeneration of the hypothalamus and optic tracts, along with a prominent fluid-filled craniopharyngeal duct (putative Rathke's cleft cyst) separating the pars distalis and the pars intermedius. The hypothalamic degeneration, possibly secondary to a Rathke's cleft cyst, was hypothesized to be the cause of presumptive SIADH in the patient. Although rare in occurrence, Rathke's cleft cyst should be included as a differential diagnosis in dogs and cats with signs of pituitary dysfunction.

Association between bipolar episodes and fluid and electrolyte homeostasis: a retrospective longitudinal study

OBJECTIVES

Imbalance of fluid and electrolyte homeostasis has been suggested to be associated with the neuropathological processes underlying bipolar disorder. However, longitudinal data regarding the association of bipolar episodes with fluid balance are still lacking. We hypothesized that mania may be associated with a relative fluid retention and hemodilution, and depression with a relative hemoconcentration.

METHODS

Patients with bipolar disorder (n = 43) admitted to a mental health center, both with depressive and manic episodes, were retrospectively followed between 2005 and 2013. Fluid balance and electrolyte serum indices were compared between their manic and depressive episodes. We adjusted for physical and psychiatric comorbidities and for psychotropic treatment, using two-way analysis of variance with repeated measures.

RESULTS

There was a significant reduction in serum fluid balance indices during mania compared to depression: mean hemoglobin concentration 13.9 ± 1.4 g/dL versus 14.5 ± 1.4 g/dL, paired t = -4.2, p < 0.0005; mean hematocrit 41.1 ± 4.1% versus 42.3 ± 3.7%, paired t = -3.0, p < 0.005; mean albumin concentration 4.2 ± 0.3 g/dL versus 4.5 ± 0.3 g/dL, paired t = -4.5, p < 0.0001; and mean sodium concentration 140.3 ± 2.0 mEq/L versus 141.0 ± 2.0 mEq/L, paired t = -2.1, p = 0.04, respectively. Controlling for physical and psychiatric comorbidities and psychotropic treatment did not alter these associations.

CONCLUSIONS

Our results support the notion of an imbalance of fluid and electrolyte homeostasis among bipolar episodes, which is suggestive for relative hemoconcentration during depressive episodes and relative hemodilution during manic episodes. These findings may eventually lead to novel therapeutic targets.

Masking of syndrome of inappropriate antidiuretic hormone secretion: the isonatremic syndrome

OBJECTIVE

To determine whether the administration of isotonic saline in patients undergoing spinal fusion surgery prevents the development of hyponatremia, thus masking the detection of syndrome of inappropriate antidiuretic hormone secretion (SIADH).

STUDY DESIGN

Prospective observational cohort study conducted in pediatric patients undergoing spinal fusion surgery. Using established criteria for diagnosing SIADH with the exception of serum sodium as a criterion, we separated patients into those with and without masked SIADH. Random cortisol levels were measured in the perioperative period to test for adrenal insufficiency to exclude it as a cause for natriuresis and hyponatremia.

RESULTS

Of the 40 patients included in the study, 13 (32%; 95% CI, 19%-49%) met study criteria for masked SIADH. The serum sodium levels between the 2 groups were not different throughout the postoperative period. The antidiuretic hormone levels were increased at 24-48 hours after surgery (20.4 pg/mL in masked SIADH group vs 6.6 pg/mL in no masked SIADH group, P = .04). Subjects with masked SIADH demonstrated a tendency for weight gain (3.9 kg vs 2.5 kg, P = .058), which was maximal on postoperative day 2. Cortisol levels were similar between the groups.

CONCLUSION

Masked SIADH (SIADH-like state without hyponatremia) commonly occurs in the postoperative period in children and young adults undergoing spinal fusion surgery. Early postoperative evaluation and recognition may result in appropriate management of patient's fluid balance.

Evaluation and management of hyponatraemia in children

AIM

Paediatric hyponatraemia is usually caused by an excess of antidiuretic hormone and may lead to serious neurological complications. It is challenging for clinicians to differentiate between conditions causing excess water and salt loss. This review analyses individual causes of hyponatraemia and focuses on optimal diagnostic algorithms and treatment strategies.

CONCLUSION

Correct evaluation of hyponatraemia requires proper understanding of the aetiology and appropriate management calls for a detailed history, physical examination and specific laboratory investigations.