What are the important medical history considerations in syndrome of inappropriate antidiuretic hormone secretion (SIADH)?

Updated: Aug 16, 2019
  • Author: Christie P Thomas, MBBS, FRCP, FASN, FAHA; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Signs and symptoms of acute hyponatremia do not precisely correlate with the severity or the acuity of the hyponatremia. Some patients with profound hyponatremia may be relatively asymptomatic. Anorexia, nausea, and malaise are early symptoms and may be seen when the serum Na+ level is less than 125 mEq/L. A further decrease in the serum Na+ level can lead to headache, muscle cramps, irritability, drowsiness, confusion, weakness, seizures, and coma. These occur as osmotic fluid shifts result in cerebral edema and increased intracranial pressure.

Important considerations related to the history are symptoms that reflect the cause of SIADH. Patients may have symptoms that suggest increased secretion of ADH, such as chronic pain, symptoms from CNS or pulmonary tumors (eg, hemoptysis, chronic headaches), or head injury, and drug use. It is important to determine if the patient has had excessive fluid intake because of inappropriate thirst or psychogenic polydipsia or because hypotonic fluids were administered in a healthcare setting. The history may also give important information about the chronicity of the condition, which may, in turn, influence the rate of correction of hyponatremia.

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