eMedicine Specialties > Emergency Medicine > Endocrine & Metabolic

Syndrome of Inappropriate Antidiuretic Hormone Secretion: Follow-up

Author: Keenan Bora, MD, Fellow, Medical Toxicology, Detroit Medical Center; Attending Physician, Medical Center Emergency Services, Detroit
Coauthor(s): Meher Chaudhry, MD, Chief Resident, Department of Emergency Medicine, Detroit Receiving Hospital, University Health Center
Contributor Information and Disclosures

Updated: Oct 20, 2009

Follow-up

Further Inpatient Care

  • Inpatient care is indicated for severe symptomatic hyponatremia or for treatment of the underlying disease.

Further Outpatient Care

  • Water restriction is the mainstay of treatment. Patients with sodium levels of more than 125 mEq/L can be managed with water restriction of 500 mL per day and close follow-up.
  • For refractory cases of SIADH, consider pharmacologic therapy.

Inpatient & Outpatient Medications

Complications

  • Central pontine myelinolysis (CPM) is the most feared complication of excessive, overly rapid correction of hyponatremia. Typical features are disorders of upper motor neurons including spastic quadriparesis and pseudobulbar palsy, and mental disorders ranging from confusion to coma.20 The risk is increased in persons with hepatic failure, potassium depletion, large burns, and malnutrition.13 Once central pontine myelinolysis occurs as a complication, there is no proven treatment.
    • Patients with cerebral disease or underlying metabolic disorders (eg, alcoholism, liver disease, malnutrition, hypokalemia, large burns) are at increased risk for CPM. Premenopausal patients undergoing surgery, especially gynecologic or related procedures, may also have an increased risk.
    • CPM is more likely in patients with long-standing, severe hyponatremia that is corrected too rapidly.
    • Risk is minimal if hyponatremia develops over less than 48 hours, even with rapid correction.
    • Onset of CPM may be delayed, manifesting days after correction, despite initial clinical improvement.

Prognosis

  • The prognosis of SIADH best correlates to the underlying cause.
  • Rapid and complete recovery tends to be the rule for recovery from drug-induced SIADH when the offending agent is withdrawn.
  • Successful treatment of pulmonary or CNS infection can lead to correction of SIADH. 
  • Patients who present with neurologic symptoms, cerebral edema, or severe hyponatremia may develop permanent neurologic impairment.

Patient Education

  • Emphasize the importance of compliance with fluid restriction.

    • Patients must understand that a typical diet may contain 750-1000 mL of water before accounting for free water intake.
    • Voluntary fluid intake may have to be limited to 250-500 mL (ie, 1-2 glasses) per day.

Miscellaneous

Medicolegal Pitfalls

  • Correcting hyponatremia too rapidly may result in CPM with permanent neurologic deficits.
  • Given the strong association with small cell carcinoma of the lung, aggressive workup for occult small cell carcinoma in patients without an alternative explanation for their SIADH may be warranted.
  • Attributing low sodium to laboratory error is a pitfall.
 
Acknowledgments

The authors and editors of eMedicine gratefully acknowledge the contributions of previous authors, Alexandr Rafailov, MD, Richard H Sinert, DO, and James Foster, MD, to the development and writing of this article.



More on Syndrome of Inappropriate Antidiuretic Hormone Secretion

Overview: Syndrome of Inappropriate Antidiuretic Hormone Secretion
Differential Diagnoses & Workup: Syndrome of Inappropriate Antidiuretic Hormone Secretion
Treatment & Medication: Syndrome of Inappropriate Antidiuretic Hormone Secretion
Follow-up: Syndrome of Inappropriate Antidiuretic Hormone Secretion
References
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References

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Further Reading

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Keywords

SIADH, antidiuretic hormone, ADH, vasopressin, syndrome of inappropriate antidiuretic hormone secretion, hyponatremia, elevated urine osmolality, excessive sodium excretion, renal excretion of water, concentrated urine, ADH dysregulation, exercise-induced hyponatremia, osmolarity, cerebral salt wasting, reset osmostat

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Contributor Information and Disclosures

Author

Keenan Bora, MD, Fellow, Medical Toxicology, Detroit Medical Center; Attending Physician, Medical Center Emergency Services, Detroit
Keenan Bora, MD is a member of the following medical societies: American Academy of Clinical Toxicology, American Academy of Emergency Medicine, American College of Emergency Physicians, American College of Medical Toxicology, and American Medical Association
Disclosure: Nothing to disclose.

Coauthor(s)

Meher Chaudhry, MD, Chief Resident, Department of Emergency Medicine, Detroit Receiving Hospital, University Health Center
Disclosure: Nothing to disclose.

Medical Editor

Erik D Schraga, MD, Consulting Staff, Department of Emergency Medicine, Mills-Peninsula Emergency Medical Associates; Consulting Staff, Permanente Medical Group, Kaiser Permanente, Santa Clara Medical Center
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Howard A Bessen, MD, Professor of Medicine, Department of Emergency Medicine, UCLA School of Medicine; Program Director, Harbor-UCLA Medical Center
Howard A Bessen, MD is a member of the following medical societies: American College of Emergency Physicians
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Erik D Schraga, MD, Consulting Staff, Department of Emergency Medicine, Mills-Peninsula Emergency Medical Associates; Consulting Staff, Permanente Medical Group, Kaiser Permanente, Santa Clara Medical Center
Disclosure: Nothing to disclose.

 
 
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