A woman is drowsy with a sodium of 121 mmol/L on the second day after a hysterectomy having received large volumes of 5 percent dextrose. What is the most likely mechanism?
Answer and explanation
Correct answer: D. Free water given with non-osmotic ADH release after surgery
- Step 1: Surgery causes pain, stress and nausea, which stimulate ADH release. Step 2. With ADH acting, dextrose, being metabolised to free water, dilutes plasma sodium. Isotonic fluids and sodium monitoring are safer. Answer: Free water given with non-osmotic ADH release after surgery. Why not the others: Adrenal failure is not suggested by the history. Saline would raise or maintain sodium rather than lower it. A pituitary aldosterone-secreting tumour is not relevant.
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