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

Recovery from SIADH-associated osteoporosis: a case report

INTRODUCTION

Recent studies show an association between hyponatremia and osteoporosis. We have previously reported a case of severe male osteoporosis due to chronic syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Here, we provide a follow-up on this case after cure of the condition that further supports the causal relationship.

THE CASE

A 38-year-old man had been diagnosed with severe osteoporosis most likely due to chronic SIADH. The SIADH was believed to be idiopathic. A magnetic resonance imaging scan, however, revealed a tumor in the sinus, and biopsies showed an esthesioneuroblastoma, immunohistochemically positive for antidiuretic hormone (ADH). After the tumor was removed, ADH and sodium levels normalized. A dual-energy x-ray absorptiometry scan performed 7 months after the patient's last surgery showed a significant spontaneous improvement in bone mineral density in the lumbar vertebrae.

CONCLUSION

This case provides evidence for a causal relationship between SIADH and chronic hyponatremia and impaired bone metabolism that can lead to severe secondary osteoporosis. The effect on bone metabolism is at least partially reversible.

The Syndrome of Inappropriate Secretion of AntiDiuretic Hormone in Patients With Brucellosis

OBJECTIVE

Various studies have shown that a number of infectious disease causes syndrome of inappropriate antidiuretic hormone (SIADH). However, the relationship between infectious disease and SIADH is not yet fully known. In this prospective study, we aimed to assess the presence of SIADH in patients with brucellosis.

PATIENTS AND METHODS

Thirty-five patients with acute brucellosis were retrospectively reviewed. The diagnosis of brucellosis was performed using the Wright test in connection with blood culture. SIADH was defined by euvolemic hyponatremia (serum sodium level lower than 135 mEq/l) with increased urinary sodium excretion (urinary sodium higher than 40 mmol/l).

RESULTS

Of the 35 patients, 19 (54%) had SIADH; 20 (57%) also had hypouricemia (uric acid level lower than 4 mg/dl). Additionally, all of the studied patients had a high mean urinary sodium excretion rate (mean 132 mmol/l; range 40-224). Most importantly, the hyponatremic patients were more likely to have a lower albumin level (P < 0.01).

CONCLUSIONS

SIADH is a major complication of brucellosis. The presence of SIADH could be a diagnostic tool for diagnosing brucellosis. Further larger randomized studies may confirm these findings.

Desmopression is an effective adjunct treatment for reversing excessive hyponatremia overcorrection

We report a case of a 50-year-old malnourished African American male with hiccups, nausea and vomiting who was brought to the Emergency Department after repeated seizures at home. Laboratory evaluations revealed sodium (Na⁺) 107 mmol/L, unmeasurably low potassium, chloride < 60 mmol/L, bicarbonate of 38 mmol/L and serum osmolality 217 mOsm/kg. Seizures were controlled with 3% saline IV. Once nausea was controlled with iv antiemetics, he developed large volume free water diuresis with 6 L of dilute urine in 8 h (urine osmolality 40-60 mOsm/kg) and serum sodium rapidly rose to 126 mmol/L in 12 h. Both intravenous desmopressin and 5% dextrose in water was given to achieve a concentrated urine and to temporarily reverse the acute rise of sodium, respectively. Serum Na⁺ was gradually re-corrected in 2-3 mmol/L daily increments from 118 mmol/L until 130 mmol/L. Hypokalemia was slowly corrected with resultant auto-correction of metabolic alkalosis. The patient discharged home with no neurologic sequaele on the 11^th hospital day. In euvolemic hyponatremic patients, controlling nausea may contribute to unpredictable free water diuresis. The addition of an antidiuretic hormone analog, such as desmopressin can limit urine output and prevent an unpredictable rise of the serum sodium.

Multiple electrolyte disorders in a neurosurgical patient: solving the rebus

BACKGROUND

It is important to ensure an adequate sodium and volume balance in neurosurgical patients in order to avoid the worsening of brain injury.Indeed, hyponatremia and polyuria, that are frequent in this patient population, are potentially harmful, especially if not promptly recognized.Differential diagnosis is often challenging, including disorders, which, in view of similar clinical pictures, present very different pathophysiological bases, such as syndrome of inappropriate antidiuresis, cerebral/renal salt wasting syndrome and diabetes insipidus.

CASE PRESENTATION

Here we present the clinical report of a 67-year-old man with a recent episode of acute subarachnoid haemorrhage, admitted to our ward because of severe hyponatremia, hypokalemia and huge polyuria.We performed a complete workup to identify the underlying causes of these alterations and found a complex picture of salt wasting syndrome associated to primary polydipsia. The appropriate diagnosis allowed us to correct the patient hydro-electrolyte balance.

CONCLUSION

The comprehension of the pathophysiological mechanisms is essential to adequately recognize and treat hydro-electrolyte disorders, also solving the most complex clinical problems.

A case report of syndrome of inappropriate antidiuretic hormone secretion with Castleman's disease and lymphoma

BACKGROUND

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a common cause of hyponatremia in hospitalized patients and is often described in patients with small-cell carcinoma of the lung. In this report, we described both Castleman's disease and lymphoma coexisting in one patient with SIADH.

CASE PRESENTATION

A 70-year-old Chinese woman with a history of diabetes mellitus and insulin therapy had severe hyponatremia and gastrointestinal symptoms. Through a series of examinations, common causes such as pulmonary carcinoma were excluded. An abdominal mass was detected by computed tomography. Although the peripheral lymph node biopsy showed the pathological result as Castleman's disease, the pathology of the abdominal lymph node revealed diffuse large B-cell lymphoma. After chemotherapy, the hyponatremia was treated during a period of follow-up.

CONCLUSION

This patient presented with the rare clinical condition of inappropriate antidiuretic hormone secretion alongside Castleman's disease and lymphoma. Asymptomatic hyponatremia may persist for some time suggesting that clinical physicians should pay attention to the mild cases of hyponatremia. We also hypothesized that Castleman's disease is a condition of pre-lymphoma with both having the ability to cause SIADH. The possibility of lymphoma as well as Castleman's disease triggering the development of SIADH should also be taken into consideration for conducting recurrent biopsies.

[Hematologic and oncologic emergencies]

The rapid development of novel, targeted drugs in cancer medicine has led to an increase in chronically ill cancer patients and hematology patients, who are being treated aggressively despite significant comorbidities and higher age. This development will lead to an increase in the number of hematologic and oncologic emergencies, and these patients will be seen by various specialties. This review article, therefore, aims at providing clinical management algorithms for the most frequent emergencies.

Health care utilization, costs, and readmission rates associated with hyponatremia

PURPOSE

Hyponatremia is associated with higher morbidity and mortality rates among hospitalized patients. Our study evaluated health care utilization and associated costs of patients hospitalized with a primary diagnosis of hyponatremia.

METHODS

Hospitalized patients with a primary discharge diagnosis of hyponatremia (aged ≥ 18 years) were identified from the Premier Perspective™ database (January 1, 2007-March 31, 2010) and matched to non-hyponatremic (non-HN) patients using a combination of exact patient characteristic matching and propensity score matching. Univariate and multivariate statistics were used to compare hospital resource usage, costs, and 30-day readmission rates between cohorts.

RESULTS

Hospital length of stay (LOS) (± standard deviation) (3.78 ± 3.19 vs 3.54 ± 3.26 days; P < 0.001) and cost ($5396 ± $6500 vs $4979 ± $6152; P < 0.001 for the hyponatremic [HN] and non-HN patient cohorts, respectively) were greater for the HN cohort, but intensive care unit (ICU) costs ($3554 ± $6463 vs $3484 ± $8510; P = 0.828) and ICU LOS (2.37 ± 3.47 vs 2.52 ± 3.87; P = 0.345) did not differ between cohorts. The ICU admission rate (7.9% vs 4.4%; P < 0.001), as well as the 30-day readmission rate (12.1% vs 2.9%; P < 0.001) were greater for the HN cohort. After adjustment for key patient characteristics, hyponatremia was associated with a 7.6% increase in hospital LOS, an 8.9% increase in hospital costs, and a 9% increase in ICU costs. Hyponatremia was associated with an increased risk of ICU admission (odds ratio, 1.89, confidence limits, 1.72, 2.07; P < 0.001) and 30-day hospital readmission for hyponatremia (odds ratio, 4.76; confidence limits, 4.31, 5.26; P < 0.001).

CONCLUSION

Compared with non-HN patients, patients with a primary diagnosis of hyponatremia use a greater amount of hospital resources and represent a challenge to hospital profitability due to the increased likelihood of 30-day readmission.

Prevalence of hyponatremia on geriatric wards compared to other settings over four decades: a systematic review

Aim of the study was to analyze temporal trends in prevalence of hyponatremia over four decades in different settings. A systematic review of the literature from 1966 to 2009 yielded prevalences of hyponatremia, with standard errors (SE) and pooled estimated means (PEM), calculated by year and setting (geriatric, ICU, other hospital wards, psychiatric hospitals, nursing homes, outpatients). 53 studies were included. Prevalence of hyponatremia was stable from 1976 to 2006, and higher on geriatric wards accept for ICU: e.g. PEM prevalence of mild hyponatremia (serum sodium <135 mM) was 22.2% (95%CI 20.2-24.3) on geriatric wards, 6.0% (95%CI 5.9-6.1) on other hospital wards and 17.2% (SE 7.0) in one ICU-study; for severe hyponatremia (serum sodium<125 mM) these figures were 4.5% (95%CI 3.0-6.1), 0.8% (95%CI 0.7-0.8) and 10.3% (SE 5.6). In nursing homes PEM prevalence of mild hyponatremia was 18.8% (95%CI 15.6-22.2). The higher prevalence on geriatric wards could partly be explained by age-related changes in the regulation of serum sodium. Other underlying factors can be the presence of multiple diagnoses and the use of polypharmacy.

Syndrome of inappropriate antidiuresis in doxylamine overdose

Doxylamine succinate, an H(1)-antihistamine drug, is commonly used as sleep-inducing agent as well as therapy for nausea and vomiting in pregnancy. At usual doses, it may cause impairment of cognitive and psychomotor performance, anticholinergic effects, agitation and postural hypotension. Besides, since this drug is frequently involved in either accidental or intentional overdoses, it seems relevant to bear in mind other possible toxic effects. We report a case of acute severe hyponatremia in the setting of a syndrome of inappropriate antidiuresis (SIAD), an apparent new adverse effect linked to doxylamine overdose. The Naranjo adverse drug reaction probability scale indicated a probable relationship between doxylamine intake and SIAD development. SIAD may be considered as a potential, serious adverse reaction of doxylamine overdose. Clinicians should consider this aetiological possibility when attending patients suffering from hyponatremia.

Evaluation of incremental healthcare resource burden and readmission rates associated with hospitalized hyponatremic patients in the US

BACKGROUND

Hyponatremia is a prevalent electrolyte disorder in hospitalized patients indicative of greater morbidity and mortality. A large-scale retrospective analysis was conducted to evaluate the incremental burden of hospitalized hyponatremic (HN) versus non-HN patients in terms of hospital resource utilization, costs, and hospital readmissions in the real-world setting.

METHODS

HN patients (≥18 years) were selected from the Premier Hospital Database between January 1, 2007 and March 31, 2010 and matched to a non-HN control cohort using propensity score matching. Bivariate and multivariate statistics were employed to evaluate the differences in healthcare resource utilization, costs, and hospital readmissions between patient cohorts.

RESULTS

Among the matched patient cohorts, length of stay (LOS) (8.8 ± 10.3 vs 7.7 ± 8.5 days, P < 0.001), hospital admission costs ($15,281 ± $24,054 vs $13,439 ± $22,198, P < 0.001), intensive care unit (ICU) LOS (5.5 ± 7.9 vs 4.9 ± 7.1 days, P < 0.001), and ICU costs ($8525 ± $13,342 vs $7597 ± $12,695, P < 0.001) were greater for the HN versus non-HN cohort, as were hospital readmission rates 30 days postdischarge. Multivariate regressions further demonstrated that hyponatremia was associated with an increase of 10.9% for LOS, 8.2% for total hospitalization costs, 10.2% for ICU LOS, and 8.9% for ICU costs. Additionally, after multivariate adjustment, hyponatremia was associated with a 15.0% increased chance for hospital readmission 30 days postdischarge (P < 0.0001).

CONCLUSIONS

Hyponatremia is an independent predictor of increased hospitalization LOS and cost, ICU admission and cost, and 30-day hospital readmission, and therefore represents a potential target for intervention to reduce healthcare expenditures for a large population of hospitalized hyponatremic patients.

A-kinase anchoring proteins as potential drug targets

A-kinase anchoring proteins (AKAPs) crucially contribute to the spatial and temporal control of cellular signalling. They directly interact with a variety of protein binding partners and cellular constituents, thereby directing pools of signalling components to defined locales. In particular, AKAPs mediate compartmentalization of cAMP signalling. Alterations in AKAP expression and their interactions are associated with or cause diseases including chronic heart failure, various cancers and disorders of the immune system such as HIV. A number of cellular dysfunctions result from mutations of specific AKAPs. The link between malfunctions of single AKAP complexes and a disease makes AKAPs and their interactions interesting targets for the development of novel drugs. LINKED ARTICLES This article is part of a themed section on Novel cAMP Signalling Paradigms. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.166.issue-2.

Evaluation of costs associated with tolvaptan-mediated hospital length of stay reduction among US patients with the syndrome of inappropriate antidiuretic hormone secretion, based on SALT-1 and SALT-2 trials

BACKGROUND

Two randomized clinical trials, the Study of Ascending Levels of Tolvaptan in Hyponatremia 1 and 2 (SALT-1 and SALT-2), showed that tolvaptan was an efficacious and safe therapy for the treatment of hyponatremic patients with the syndrome of inappropriate antidiuretic hormone secretion (SIADH).

HYPOTHESIS

This study evaluated the potential cost savings associated with tolvaptan usage based on the SALT-1 and SALT-2 trials.

METHODS

Hospital length of stay (LOS) reduction associated with tolvaptan versus placebo was evaluated among hyponatremic patients with the SIADH (serum sodium < 135 mEq/L) from the combined data of the SALT-1 and SALT-2 trials. The Healthcare Cost and Utilization Project 2009 Nationwide Inpatient Sample database was used to estimate hospital cost and LOS for hospitalizations of adult (age ≥ 18 years) patients with the SIADH. A cost-offset model was constructed to evaluate the impact of tolvaptan on hospital cost and LOS, with univariate and multivariate Monte Carlo sensitivity analyses.

RESULTS

In the SALT-1 and SALT-2 trials, patients with the SIADH receiving tolvaptan had a shorter hospital LOS than patients receiving placebo (4.98 vs 6.19 days, respectively). There were 21 718 hospitalizations for the SIADH identified from the Healthcare Cost and Utilization Project Nationwide 2009 Inpatient Sample database, with a mean LOS of 5.7 days and mean total hospital costs of $8667. Using an inpatient tolvaptan treatment duration of 4 days, with a daily wholesale acquisition cost of $250, the cost-offset model estimated an LOS reduction among SIADH hospitalizations of 1.11 days. The total cost offset, including tolvaptan drug cost, was estimated to be $694 per admission. The cost-neutral break-even duration of tolvaptan therapy is 6.78 days. Univariate and multivariate sensitivity analyses demonstrated consistent cost reduction associated with tolvaptan usage. Ten thousand cycles of Monte Carlo simulation showed the 95% CI for cost offset to be $73 to $1405.

CONCLUSION

Based on the SALT-1 and SALT-2 trials, tolvaptan usage is associated with a shorter hospital LOS than placebo among patients with the SIADH. Including the drug cost for 4 days of inpatient tolvaptan therapy, tolvaptan is associated with an estimated mean hospital cost reduction of $694 per admission in the United States.

[Hypothalamic involvement in multiple sclerosis]

Hypothalamic involvement is a rare condition in patients with multiple sclerosis (MS). We report two patients with a long history of MS who presented with severe acute hypothermia with associated thrombocytopenia and elevated transaminase levels. Several cases of hypothermia or hyperthermia in patients with MS have been reported in the literature. They could be linked with hypothalamic lesions, in particular in the pre-optic area. However, other anatomical locations seem to be involved in thermoregulation and can be affected by MS. Besides, some cases of syndrome of inappropriate antidiuretic hormone secretion have been reported in patients with MS. Finally, some sleep disorders, particularly hypersomnia or narcolepsy, could be related to hypothalamic lesions, through the fall in hypocretin-1 in the cerebrospinal fluid. Hypocretin-1 is a neuropeptide that is secreted by some hypothalamic cells. It plays a role in the sleep-awake rhythm. We report one patient with narcolepsy and cataplexy before the first symptoms of MS appeared. Hypothalamic signs are rare in MS. However, several series of autopsies have shown a high frequency of demyelinating lesions in the hypothalamic area. Among these lesions, the proportion of active lesions seems elevated. Yet only few of them have a clinical or biological translation such as thermoregulation dysfunction, sleep disorders or natremia abnormalities. Thus, it seems unlikely that inflammatory hypothalamic lesions alone, even when bilateral, could be the explanation of these signs. A sufficient number of inflammatory demyelinating lesions, which we can observe in patients with a long history of MS and an already severe disability, is probably necessary to develop such a rare symptomatology. Hypothalamic signs might be a factor of poor prognosis for the disease course and progression of the disability.