Using an algorithm to derive a mean systemic filling pressure analogue, cardiac power and dynamic measures of the venous return pressure gradient relative to the mean systemic filling pressure provided an assessment of the efficiency of volume expansion in post-surgical cardiac patients.

No abstract

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.

Critically ill patients with acute renal failure are traditionally treated with low-protein diets to help control uremia. This dietary approach may be deleterious to the patient's nutritional status and unnecessary, especially if continuous renal placement therapies (CRRT) are used. However, the optimal amount of protein supplementation during CRRT is unknown. In patients receiving CRRT, a high protein intake may result in a positive nitrogen balance in the absence of uncontrolled uremia. Accordingly, we studied nitrogen metabolism in two consecutive cohorts of acute renal failure patients receiving equal amounts of calories but variable amounts of nitrogen. One group received protein according to the preferences of the attending clinician, the other a high and fixed amount of protein (2.5 g/kg/day). Patients treated according to attending clinician preferences received significantly less dietary protein (1.2 g/kg/day vs. 2.5 g/kg/day; p < 0.0001) and had a negative mean nitrogen balance of -5.5 g/day. Patients receiving a high and fixed amount of protein had a less negative mean nitrogen balance (-1.92 g/day). Such patients were more likely to experience a positive nitrogen balance during any 24-h period (53.6% vs. 36.7%; p < 0.05). They also required more aggressive hemofiltration to maintain control of uremia (mean ultradiafiltrate volume: 2145 mL/h vs. 1658 mL/h; p < 0.0001) and had a significantly higher but still acceptable mean plasma urea level (26.6 mmol/L vs. 18 mmol/L; p < 0.0001). Survival was not significantly different in the two groups (37.5% vs. 31.3%). We conclude that a high-protein diet can be safely administered to critically ill patients with acute renal failure receiving continuous renal replacement therapy. Such a high protein intake improves nitrogen balance when compared to moderate protein intake. A low protein intake is unnecessary in patients treated with CRRT.

No abstract

It is unknown whether continuous renal replacement techniques result in diminished morbidity and mortality when compared to conventional dialytic techniques. To investigate this issue a previously described, retrospectively studied group of critically ill patients with severe acute renal failure treated by conventional dialysis (CD) was compared to a prospectively studied group of similar patients treated by acute continuous hemodiafiltration (ACHD). A combined retrospective and prospective clinical and laboratory investigation was carried out for 234 consecutive critically ill patients with severe acute renal failure in the intensive care unit of a tertiary institution. Biochemical, clinical and outcome data in all patients treated by conventional dialytic techniques (intermittent hemodialysis and/or peritoneal dialysis) during a 5-year period were retrospectively analyzed, and a prospective analysis of the same biochemical, clinical and outcome data in all patients treated by acute continous hemodiafiltration was done over a similar time span, with statistical comparison of findings. One hundred and fifty patients were treated by ACHD and 84 by CD. ACHD patients were more severely ill (mean APACHE II score: 28.2 vs. 25.8; p < 0.01) and older (mean age: 59.9 vs. 55.5 years; p < 0.01). There were no significant differences in the incidence of sepsis, bacteremia and need for mechanical ventilation. ACHD resulted in better control of uremia (mean steady-state plasma urea level: 20.1 vs. 31.7 mmol/l; p < 0.001) and hyperphosphatemia (mean serum phosphate: 1.26 vs. 1.95 mmol/l) after 24 h of initiation of therapy. It also allowed the administration of full nutritional support in a significantly greater percentage of patients (91.3 vs. 64.8%; p < 0.001). Survival to ICU discharge was significantly greater in ACHD patients (43.3 vs. 29.8%; p < 0.05), but survival to hospital discharge was not statistically different (ACHD: 38.6% vs. CD: 29.8%; n.s.). When survival to hospital discharge was corrected for illness severity, patients with an intermediate degree of illness severity (APACHE score between 19 and 29) were more likely to survive if treated with ACHD rather than CD (50.6 vs. 30%; p < 0.025). ACHD survivors had a shorter mean ICU stay (11.8 vs. 16.9 days; p < 0.05) and a shorter mean duration of hospital stay (33.9 vs. 58.4 days; p < 0.001). The findings of this study suggest that, in critically ill patients, ACHD may provide better control of uremia and a greater ability to administer full nutritional support than CD. They also suggest that the use of ACHD is associated with a shorter duration of ICU and hospital stay and may even provide a survival advantage. The current study invites further investigation of the use of continuous hemofiltration techniques in the critically ill.

The correct measurement of CVP is pivotal to its proper clinical application. This relates to defining the pressure gradient for venous return and heart efficiency. The clinical appreciation of CVP should be restored by educational efforts of its physiological context.

We have prospectivly investigated the effect of a flexible approach to the management of acute renal failure in critically ill patients based on continuous haemodiafiltration (CHD). Fifty critically ill patients (mean APACHE II score 28.1, range 18-37), with a mean age of 59.5 years, were treated with continuous arteriovenous haemodiafiltration (CAVHD) and/or continuous venovenous haemodiafiltration (CWHD). CHD achieved excellent haemodynamic stability and control of azotaemia in all patients and permitted aggressive parenteral nutrition. The mean blood urea concentration fell from 33.9 mmol/l (95% confidence interval, CI, 29.1-38.7) to a plateau of 17 mmol/l (95% CI 14.3-19.7) after 72 h of therapy despite persistent anuria and the parenteral administration of 0.3g/kday of protein nitrogen (mean urea clearance: 24.2ml/min; 95% CI 22.9-25.5). No supplemental dialytic therapy was required during the 9,485 h of treatment. All clinically significant complications related to vascular access (14%). Twenty-two patients (44%) survived to be discharged from the ICU. CHD is relatively safe and effective in the management of acute renal failure in the critically ill.