Two geriatric cases.

Increased production of urea and heart failure SIR,-In a recent paper Dr Julia Lowe and her colleagues (11 August, p 360) concluded that the most common adverse reaction to frusemide is a reduction of the volume of extracellular fluid "manifested clinically or as a raised blood urea concentration."This assumes that the association between frusemide and a raised urea is one of cause and effect.The most common cause of a raised plasma urea concentration in hospital patients is heart failure.'In a recent study2 we confirmed the suggestion of Domenet and Evans3 that this rise in plasma urea was often due to an increased production of urea rather than a reduction in glomerular filtration rate.We do not underestimate the potential seriousness of volume depletion.However, we suggest that increased production of urea has been largely ignored as a feature of heart failure, that it is a major factor in the rise in plasma urea in heart failure, and that it may explain the relation between plasma urea and prognosis in heart failure.