Slow continuous hemodialysis--new therapy for acute renal failure in critically ill patients--Part 2. Animal experiments and clinical implication.

Five acutely uremic dogs were treated for 9 hours by means of slow continuous hemodialysis using our newly developed machine. The blood concentrations of urea nitrogen (BUN) and creatinine were determined every hour and were compared to those calculated from a mathematical pool model. In order to assess the accuracy of volume control, the body weight of dogs was monitored continuously by scale bed, under simultaneous 200 ml/hour infusion and ultrafiltration. Arterial and swan-ganz catheter were inserted to measure hemodynamic changes during hemodialysis. The efficacy of solute elimination was coincidental with the predicted value. The error of volume control was within +/- 5% of set rate. Hemodynamic parameters were not significantly influenced in spite of a large amount of volume exchange. In conclusion, it was demonstrated that slow continuous hemodialysis could be a better alternative to peritoneal dialysis, continuous hemofiltration or conventional hemodialysis in order to treat acute renal failure in critically ill patients, in terms of solute removal, volume control and the effects on hemodynamics.

The dual effects of hemodialysis on cardiac function assessed by pulsed Doppler echocardiography.

To assess the effect of hemodialysis on cardiac function, a change of preload due to water removal was considered. In order to keep the preload constant during hemodialysis, extracorporeal ultrafiltration was induced before hemodialysis (step 1), and then hemodialysis without water removal was achieved (step 2). Cardiac performance in 8 patients was evaluated before and at the end of each step using pulsed doppler echocardiography. Step 1: Ultrafiltration was 1350 +/- 410 ml and hematocrit increased significantly. Left ventricular end-diastolic dimension (LVDd) decreased from 40.3 +/- 4.2 (mean +/- standard deviation) mm to 36.1 +/- 4.6 mm (p less than 0.005) and aortic peak flow velocity (PFV) also decreased from 59.9 +/- 16.0 cm/s to 49.0 +/- 11.0 cm/s (p less than 0.005). Step 2: In contrast, after hemodialysis without water removal, the mean velocity of circumferential fiber shortening (mVcf) increased from 1.36 +/- 0.26 circ/s to 1.86 +/- 0.36 circ/s (p less than 0.005). PFV and average acceleration (Aa) increased from 49.0 +/- 11.0 cm/s to 63.8 +/- 11.4 cm/s (p +/- 0.001) and from 750 +/- 220 cm/s/s to 1270 +/- 280 cm/s/s (p less than 0.001), respectively. During this step, serum potassium and osmolality decreased significantly. In conclusion, hemodialysis improves cardiac function under constant preload condition and this is due to the direct effects of hemodialysis by the correction of electrolytes and osmolar components such as uremic toxin.