Lessons to be learned: a case study approach - Diuretic therapy and a laxative causing electrolyte and water imbalance, loss of attention, a fall andsubsequent fractures of the tibia and fibula in an elderly lady

The case is described of a hitherto well, alert and intelligent lady of 85 years of age, who commenced medication with diuretics - prescribed for mild congestive cardiac failure; she developed constipation consequent upon the diuresis and dehydration thereby provoked. As a result she began to take, unknown to her general practitioner, regular and increasing amounts of laxa tives. At about this time she was noted by her son to become "rapidly senil e" - with the result that she fell on account of losing her normally good c oncentration and attention; she sustained fractures of the right tibia and fibula. Shortly after admission to hospital she was premedicated, anaesthet ised and operated upon, following which there was a postoperative regimen c omprising several litres of low sodium isotonic infusions, all given intrav enously. She was found at this point to be severely hyponatraemic with a lo w serum osmolality, but following the institution of water restriction rapi dly improved as her serum sodium rose again; there was an accompanying mass ive diuresis as the previously retained water was voided. Concomitant with the serum sodium rise her mental concentration and attention regained their former levels. The biochemical and cellular mechanisms underlying this pat ient's symptoms are discussed.