A 43-year-old woman comes to the emergency department due to nausea, dizziness, and headache for a day. Her menses began 2 days ago. She has occasionally had fatigue and dizziness during her menstrual periods, but today's symptoms feel different. The patient has a history of von Willebrand disease, causing recurrent, heavy menstrual blood loss, and is scheduled for an endometrial ablation procedure. Her only medication is intranasal desmopressin taken on the first 3 days of her menstrual period. Temperature is 36.9 C (98.4 F), blood pressure is 120/80 mm Hg, pulse is 92/min and regular, and respirations are 18/min. The patient appears restless. Mucous membranes are moist. Deep tendon reflexes are 2+ throughout and Babinski sign is absent. Sensory examination shows no focal deficits. The chest is clear to auscultation. The abdomen is soft and nontender. There is no peripheral edema. The remainder of the examination is unremarkable. Which of the following is the most appropriate next step in management?

Question

A 43-year-old woman comes to the emergency department due to nausea, dizziness, and headache for a day.  Her menses began 2 days ago.  She has occasionally had fatigue and dizziness during her menstrual periods, but today's symptoms feel different.  The patient has a history of von Willebrand disease, causing recurrent, heavy menstrual blood loss, and is scheduled for an endometrial ablation procedure.  Her only medication is intranasal desmopressin taken on the first 3 days of her menstrual period.  Temperature is 36.9 C (98.4 F), blood pressure is 120/80 mm Hg, pulse is 92/min and regular, and respirations are 18/min.  The patient appears restless.  Mucous membranes are moist.  Deep tendon reflexes are 2+ throughout and Babinski sign is absent.  Sensory examination shows no focal deficits.  The chest is clear to auscultation.  The abdomen is soft and nontender.  There is no peripheral edema.  The remainder of the examination is unremarkable.  Which of the following is the most appropriate next step in management?

Quizplus · Accepted Answer

11ec25c8_d836_80af_bc81_39b00cbcf130_MD0003_00 This patient's acute nausea is likely due to hyponatremia induced by recent use of intranasal desmopressin. Desmopressin is an analogue of antidiuretic hormone (ADH) commonly used to treat central diabetes insipidus; it also promotes the release of von Willebrand factor, and can treat mild to moderately heavy menstrual bleeding associated with von Willebrand disease. However, since desmopressin induces physiologic effects of ADH (eg, renal water reabsorption, concentration of urine), it can cause hyponatremia and excess ADH stimulation, manifesting as syndrome of inappropriate ADH secretion (SIADH). Therefore, serum electrolytes should be obtained first in this patient to check for hyponatremia and rule in the diagnosis of SIADH. Expected laboratory findings in patients with SIADH include hypotonic hyponatremia (due to ADH-mediated water retention and reabsorption), high urine osmolality (ie, concentrated urine), and high urine sodium (due to increased secretion of natriuretic peptides). As seen in this patient, SIADH is also associated with euvolemia (eg, absence of edema or jugular venous distension) on physical examination. At first, ADH-mediated water reabsorption slightly increases extracellular volume; however, increased natriuretic peptide secretion leads to sodium and water excretion, ultimately normalizing extracellular volume. (Choice A) Although hypoxemia (eg, from pulmonary embolism) may manifest with nausea, elevated heart rate, and dizziness, this patient has no risk factors for pulmonary disease or symptoms of respiratory distress (eg, shortness of breath, chest pain). Therefore, serum electrolytes are a better initial test. (Choice B) Although acute liver failure may cause excessive bleeding and present with nausea and dizziness, this patient lacks associated findings of jaundice and abdominal pain and has no risk factors (eg, infection, excess alcohol intake). (Choice C) MRI of the brain can be used to assess for CNS pathology (eg, bleeding, acute stroke) that could manifest with headache or dizziness. However, this patient lacks focal neurologic signs; therefore, a metabolic workup with serum electrolytes is a more appropriate initial test. (Choice D) Plasma desmopressin is not routinely measured. It may be high in this patient, given her recent medication use with the onset of menses, but serum electrolytes are a more rapid initial step for confirming hyponatremia and SIADH. Educational objective: The administration of desmopressin, an analogue of antidiuretic hormone (ADH), can induce the syndrome of inappropriate ADH secretion. Urinary water excretion is impaired, leading to hypotonic hyponatremia. Laboratory studies, including serum electrolytes, urine osmolality, and urine sodium, are the first step in establishing the diagnosis. References: Desmopressin and the risk of hyponatremia: a population-based cohort study. (http://www.ncbi.nlm.nih.gov/pubmed/31634354) Intranasal desmopressin-induced hyponatremia. (http://www.ncbi.nlm.nih.gov/pubmed/8700794)

A 43-Year-Old Woman Comes to the Emergency Department Due to Nausea