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After completing this case study, the reader should be able to:

  • Identify the etiologies of hyponatremia and specifically the syndrome of inappropriate antidiuretic hormone (SIADH) release.

  • Assess risk factors for developing hyponatremia and SIADH.

  • Evaluate osmotic and fluid status in patients with hyponatremia.

  • Recommend and monitor appropriate therapy and alternative treatments for SIADH.

  • Discuss treatment options for SIADH, proper administration of selected treatments, and potential side effects.


Chief Complaint

“There’s nothing wrong with me, I don’t know why she made me come here!”


Patrick O’Flannery is a 73-year-old man who presents to the ED after several episodes of “weird” behavior, according to his family and friends. He is accompanied by his wife who stated that Patrick had been the unrestrained driver in a car accident 3 days earlier. Patrick was driving himself home from the Caribou Lodge when he swerved off the road and hit a tree. His wife indicates that he hit his head on the steering wheel and lost consciousness for approximately 2 minutes but appeared otherwise unharmed except for a cut on his forehead. The paramedics cleaned and bandaged the patient’s lesion and noted that he was combative and disoriented but refused to go to the hospital. The wife states that Patrick has not been “acting like himself” since the accident and she had observed him displaying worsening confused and disoriented behavior in the past 24 hours.


Exercise-induced asthma since childhood

Depression for 7 years


Lives at home with wife; has two children, both living out of state. Employed part time as a cab driver. Social alcohol use. Denies smoking and use of illicit substances.


Albuterol inhaler 2 puffs by mouth Q 6 H PRN exercise; last used 1 week ago

Fluoxetine 20 mg by mouth daily for 6 years


Penicillin (reaction unknown)


Difficult to obtain because of decreased mental status. Wife states that he has no medical problems except asthma and depression.

Physical Examination


A&O × 3 but disoriented about recent events. Patient is agitated and confused.


BP 130/84 mm Hg, P 88 bpm, RR 21, T 37°C; Wt 209 lb (95 kg), Ht 5′9″ (175 cm)


Diaphoretic centrally and very warm; small lesion ...

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