MRCP2-1214

MRCP2-1214

A 72-year-old woman presents to the emergency clinic after her GP noticed low sodium levels in a routine blood test. Her electrolyte levels are as follows:

Na+ 120 mmol/L (135 – 145)
K+ 4.2 mmol/L (3.5 – 5.0)
Urea 5.6 mmol/L (2.0 – 7.0)
Creatinine 65 µmol/L (55 – 120)

A previous electrolyte check 2 years ago was unremarkable. However, she is currently asymptomatic and shows no signs of peripheral edema. On examination, her jugular venous pulse is visible but not raised, and her mucous membranes are moist. Heart sounds are normal, and her chest is clear on auscultation. Her heart rate is 68 beats per minute, and her blood pressure is 115/75 mmHg.

Further tests reveal a serum osmolality of 275 mOsm/kg (280-285), urine sodium of 42 mEq/L (<20), and urine osmolality of 175 mOsm/kg (50-1200). What is the most appropriate initial management step to increase her sodium levels?