Syndrome of Inappropriate Anti-Diuretic Hormone (SIADH); Risks and Dangers of a Misnomer
CCCF ePoster library. Shafiee M. 11/02/16; 151003; 121
Dr. Mohammad Ali Shafiee
Dr. Mohammad Ali Shafiee
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Topic: Basic or Translational Science

Syndrome of Inappropriate Anti-Diuretic Hormone (SIADH); Risks and Dangers of a Misnomer

Shafiee, Mohammad Ali1; TabaTaba-Vakili, Sahar2; Parastandechehr, Gilda2; Hakimfaal, Shirin2; Sharif, Umar2; Nazarian, Amir; Dastgheib, Mohammad2; Ghaffarian, Hanieh2;

1Division of General Internal Medicine
 Assistant Professor, Department of Medicine, University of Toronto
 Royal College Mentor, Department of Medicine, University of Toronto
 Toronto General Hospital, 200 Elizabeth Street, 14 EN-208
 Toronto, ON, M5G 2C4 | Tel: 416-340-4800 ex 6244 | Fax: 416-595-5826

2Division of General Internal Medicine Toronto General Hospital
 University Health Network
 Toronto General Hospital, 200 Elizabeth Street, 14 EN-209A
 Toronto, ON, M5G 2C4 | Tel: 416-340-4800 ex 2182 | Fax: 416-595-5826


The first clinical case of a patient with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) was presented by Schwartz et al. in 1957. Since then, up to 30% of critically ill patients are diagnosed with this syndrome. Although patients diagnosed with SIADH are assumed to have inappropriate secretion of ADH, only 30% of these patients are found to have increased serum ADH levels. This indicates a significant knowledge gap as patients diagnosed with SIADH are often not approached physiologically and are therefore vulnerable to complications of inappropriately rapid correction of serum sodium. A physiologic approach to patients with hyponatremia in the inpatient setting is warranted as hyponatremia is an independent prognostic factor in outcome and can affect the length of hospital stay.
Herein, we aim to conduct a physiologic appraisal of patients with hyponatremia who were diagnosed with SIADH in the inpatient setting of the general internal medicine (GIM) ward of Toronto General Hospital (TGH).  Additionally we aim to propose a simplified physiologic approach to patients in the inpatient setting with hyponatremia which could potentially lead to a more individualized therapeutic approach.

We retrospectively analyzed 340 patients with hyponatremia who were admitted to TGH between 2012 and 2016 and stratified them into 6 categories based on information obtained from history of present illness, past medical history, patterns of change in plasma and urine osmolality as wells as urinalysis and urine electrolytes.

Out of the 340 patients, 221 (65%) were diagnosed with SIADH (54% male, average patient age was 67 years). Hyponatremia was found to be caused by low osmole intake (34%), enhanced ADH action due to non-osmotic stimuli (22%), increased ADH secretion (9%), reset osmostat (5%) and offending medications through various mechanisms (9%). The severity of hyponatremia was not related to the physiologic categories. The treatment approaches were predominantly fluid restriction (53%) and salt tablets (18%), followed by oxocubes (15%), IV saline infusion (10%), discontinuation of the offending medication (7%), and use of vaptans (6%).

Conclusion: Individualized management of hyponatremia in patients in the inpatient setting can be achieved by therapy geared towards the underlying physiologic process. Encouraging patients to increase osmole intake and salt tablets in conjunction with free water intake may prevent hyponatremia and improve outcomes by reducing the risk of complications from inappropriately rapid correction of serum sodium.
*This abstract is based on preliminary results.

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