Renal, Urology and Electrolytesmiddle twist
A 68-year-old woman with recently diagnosed small cell lung cancer is brought in after a generalised tonic-clonic seizure at home. Over three days she has become progressively confused and nauseated. She is not on chemotherapy yet and takes no regular medications. Her blood pressure is 128/76 mmHg with no postural drop, mucous membranes are moist, jugular venous pressure is normal and there is no oedema. Serum sodium is 114 mmol/L (135–145), potassium 4.0 mmol/L, urea 3.1 mmol/L, creatinine 62 µmol/L, glucose 5.2 mmol/L, serum osmolality 238 mOsm/kg, urine osmolality 540 mOsm/kg and urine sodium 68 mmol/L. Thyroid function and morning cortisol are normal.
Which one of the following is the most appropriate immediate management?