Hyponatremia.

Abstract

Physicians may face difficulties treating patients who have hyponatremia.The risks of rapid correction, such as pontine myelinosis, are well known.Also, many and sometimes complex factors influence the serum sodiumconcentration. A 72-year-old woman from a nursing home presents to the emergencydepartment with a change in her mental state over the past few hours. She hasa medical history of coronary artery disease and hypertension. Her medicationsinclude hydrochlorothiazide. 25 mg a day, and aspirin, 81 mg a day. Onphysical examination, she has decreased skin turgor, orthostatic hypotension,and disorientation to time, place, and person without focal neurologicdeficits. Initial laboratory tests show a serum sodium level of 110 mmol/L;blood urea nitrogen, 23.2 mmol/L (65 mg/dL); creatinine, 318 μmol/L (3.6mg/dL); triglycerides, 2.75 mmol/L (244 mg/dl); and plasma osmolality, 278mmol/kg of water (278 mOsm/kg of water). Other laboratory findings are abicarbonate value of 29 mmol/L; hematocrit, 0.35 (35%); potassium, 4.0 mmol/L;uric acid, 0.42 mmol/L (7.0 mg/dL); urine osmolality, 450 mmol/kg of water;and urine specific gravity, 1.019. Her serum sodium level 2 months beforeadmission was 135 mmol/L, and her urine output was 400 mL a day. She isadmitted to the hospital, and a regimen of intravenous isotonic sodiumchloride solution is started at a rate of 84 mL per hour in the first 24hours.