Renal replacement in critically ill patients: the age factor

The aim of this study was to assess the efficacy of the renal replacement therapy adopted in our ICU for patients who were affected by acute renal failure after their admission to the ICU, and to evaluate the role of age in relation to renal function and surviving probability.

During a period of 18 months (February 2002–July 2003), we treated 22 patients with acute renal failure by means of continuous renal replacement therapy. The patients, 17 males and 13 females were divided into two groups: one group of patients (group A) younger than 65 years; a second group (group B) older than 65 years. Group A was made up of 14 patients, 10 suffering from polytrauma and four from acute pancreatitis, and a mean age of42 ± 9 years. The second group was made up of 16 patients, who underwent major surgical interventions, four after open heart surgery, four after gynaecological surgery and eight after abdominal surgery with a mean age of 76 ± 11 years. All the patients got into our ICU for acute respiratory failure and needed mechanical ventilation. Oliguria has been diagnosed when the urine output was less than 400 ml/day. The acute renal failure was due to hypotension and sepsis; the renal replacement therapy was started when an oliguria and/or a volemic overload were observed. All patients were treated with a slow low-efficient daily dialysis (SLEDD) single pass adapted to each patient with a low flow therapy for 10–12 hours in order to obtain a good haemodynamic stability and ensure an urea clearance of 45–60 l/day and Kt/V weekly > 6. Statistical analysis was made with ANOVA and logistic regression.

The patients' ICU length of stay was 16.3 ± 5.9 days for group A and 24.4 ± 10.8 for group B. The SLEDD therapy lasted 10.3 ± 3.9 days for group A and 19.7 ± 7.1 days for group B. The Qb was 150–200 ml/min, the Qd 60–100 ml/min and the mean ultrafiltration 150 ml/hour. The caloric intake was 32.7 ± 7 kcal/kg/day with a proteic intake of 1.9 ± 0.5 g/kg/day. Six patients of group A (42.8%) and 11 patients of group B (68.7%) died. All the survivors recovered renal function.

Sepsis is the most relevant reason for acute renal insufficiency and mortality in critically ill patients. According to our experience SLEDD can be considered a safe and efficacious treatment for these patients: it allows an aggressive volemic removal and an adequate nutritional support coupled with haemodynamic stability and uremic control. The logistic regression shows that age, severity of illness and amount of organs affected were independent risk factors for poor outcome.