[Acute renal failure in the aged]

Changes due to ageing appear increasingly during the last third of the lifespan, and the overall performance capability of the organism gradually declines. Loss of function of the kidney, a vital organ, in the form of acute renal failure represents a special hazard to older patients despite modern therapies including the use of the various forms of artificial kidney. In diagnosis, care must be taken to differentiate between functional renal insufficiency and genuine acute renal failure. To prevent the complications arising through acute renal failure, the water, electrolyte and acid/base balances must be extremely carefully monitored and promptly corrected where necessary. The elderly patient with acute renal failure must receive a high calorie intake (approx. 3000 kcal/24h) and must be continuously supplied with adequate quantities of amino acids (at least 1.2--1.5 g/kg-body weight/24h). During treatment should be adjusted to the endogenous creatinine clearance which, in older patients, is often very much lowered at normal serum creatinine. With drugs whose therapeutic range is very narrow, blood-level determinations are needed. To avoid uraemic complications as far as possible, it is advisable to apply, prophylactically, either conventional haemofiltration or continuous arterio-venous haemofiltration at a serum creatinine between 3 and 4 mg/dl and serum urea between 140 and 160 mg/dl. It is of decisive importance that malfunction of other vital functions is prevented, since the mortality for older patients (over 55 years of age) with acute renal failure and no other vital-function disturbance is around 30% but this figure rises to around 75% where acute renal failure and other vital-function disturbances are present.