Continuous arteriovenous haemodiafiltration in the critically ill: influence on major nutrient balances

The impact of continuous arteriovenous haemodiafiltration (CAVHD) on nitrogen, lipid and carbohydrate balance was studied in 9 parenterally fed critically ill patients with acute renal failure. The effects on carbohydrate delivery of varying dialysate glucose concentrations or flow rates were also investigated. The total daily nitrogen loss was a mean of 24.1 g (95% CI 20.9-27.3 g/24 h) with non-urea nitrogen losses of 7.6 g (95% CI 5.6-9.6 g/24 h). Glucose delivery was a mean 5.8 g/h with a dialysate glucose concentration of 1.5% and a flow rate of 1 l/h (95% CI 4.5-7.0 g/h). Carbohydrate delivery increased with increased dialysate glucose concentration (mean 11.4 g/h with 2.5% glucose: 95% CI 9.6-13.1 g/h; mean 14.9 g/h with a 4.25% concentration: 95% CI 10.9-19; and with increased dialysate flow rates (mean 9.6 g/h, 95% CI 6.8-12.4 g/h, using 2 l/h of 1.5% glucose). Only trace amounts of cholesterol and/or triglycerides were detected in occasional ultradiafiltrate samples. CAVHD has an important impact on nitrogen and carbohydrate balance, but not on lipid status. Knowledge of these interactions is crucial for the rational planning of nutritional strategies in the critically ill.