Investigations

• urea, electrolytes, and creatinine ^a  

Why?

A low serum sodium increases the risk of dying

Patient	Prognostic Factor	Outcome	CER	RR (95% CI)	NNF+ (95% CI)
severe heart failure b	fall in serum sodium (by 3 mmol/l) independent	death at 15 months	12%	1.42 (1.08 to 1.87)	19 (9 to 100)