Pediatric CRRT: Ultrafiltration Control

1. Pediatric CRRT:Ultrafiltration Control William E. Smoyer, M.D. Pediatric Nephrology University of Michigan

2. Introduction • Ultrafiltration control not a widely accepted concern for CRRT • Often not regulated in adult ICUs • No reports of significant volume imbalances • Industry standards for pump error - 5-10% • Few reports on CRRT pump accuracy (in vitro) 1,2 • Anecdotal reports of severe unanticipated volume depletion in several small children on CRRT 1 Jenkins R et al. ASAIO J. 38:808, 1992 2 Roberts M et al. Int J Artif Organs. 15:99, 1992

3. CRRT Pump Accuracy Study • Hypothesis: Unanticipated fluid losses with CVVHD are clinically significant and result from variable pressure loads on the pumps • Study Design: • 1) To prospectively analyze the accuracy of available IV pumps during CRRT in vivo • 2) To prospectively analyze the effects of blood flow, total dialysate (D) + ultrafiltrate (UF) flow, and net UF flow rates on pump pressures in vitro

4. Methods • Patients • 4 infants and children requiring CRRT (CVVHD) • CRRT Circuit • Hemofilters: • Renal Systems; Renaflo II HF 400 (SA 0.30 m2) • Hospal; Multiflow - 60 (SA 0.60 m2) • Minntech; Minifilter Plus (SA 0.07 m2) • Blood Flow: 4 cc/kg/min (Gambro AK 10) • IV Pumps: • Medex Trilogy / Alaris Gemini / Baxter Colleague 3

5. Methods • In Vivo Data Collection • Bags weighed on infant scale accurate to +0.5 ml (g) • Sequential 1 hour measurements of: • “Set” vs. “Measured” dialysate inflow • “Set” vs. “Measured” ultrafiltrate outflow • In Vivo Data Analysis (1049 total pump-hours) • Analysis of absolute hourly error for each pump • Analysis of mean % error for each pump • Comparison of each pump’s mean % error: • At variable pump flow rates • During use for dialysate (inflow) vs. ultrafiltrate (outflow)

6. CRRT Pump Accuracy-Trilogy

7. CRRT Pump Accuracy-Gemini

8. CRRT Pump Accuracy-Colleague 3

9. CRRT Pump Accuracy-Combined

10. Results of In Vivo Studies • Dialysate Pump Error (all pumps): • Range: -6.8  +0.5% (-34.3  +4.7 ml/hr) • Mean: -4.0% • Ultrafiltrate Pump Error (all pumps): • Range: -1.5  +7.4% (-13.7  +16.2 ml/hr) • Mean: +0.9% • Cumulative Pump Error (all pumps): • Range: -7.9  +0.9% (-48.5  +9 ml/hr) • Mean: -5.2%

11. Effect of Blood Flow on CRRT Pump Pressures-Trilogy

12. Effect of Blood Flow on CRRT Pump Pressures-Colleague 3

13. Effect of Total Flow on CRRT Pump Pressures-Trilogy

14. Effect of Total Flow on CRRT Pump Pressures-Colleague 3

15. Effect of Net UF Flow on CRRT Pump Pressures-Trilogy

16. Effect of Net UF Flow on CRRT Pump Pressures-Colleague 3

17. Results of In Vitro Studies • Direct correlation between blood flow rate and: • D Post-Pump Pressures (80% increase) • UF Pre-Pump Pressures (52% increase) • Correlations with total D + UF flow rate: • Direct - UF Post-Pump Pressures (0-15 mm Hg) • Inverse - D Pre-Pump Pressures (75-69 mm Hg) • Correlations with net UF flow rate: • Direct - UF Post-Pump Pressures (14-21 mm Hg) • Inverse - D Post-Pump Pressures (68-45 mm Hg) • Inverse - UF Pre-Pump Pressures (93-71 mm Hg)

18. Summary • Pump accuracy variable among available IV pumps for CRRT • All still within industry standards at all flow rates • All 3 pumps consistently resulted in underinfusion of fluid when used for dialysate (inflow) • 2 of 3 pumps consistently resulted in excess fluid removal when used for ultrafiltrate (outflow) • Pump errors are generally additive and result in unanticipated fluid losses (x = -5.2%)

19. Summary • Unanticipated fluid losses during CRRT with available IV pumps are clinically significant (>1000 ml/24 hr) • Clinically relevant changes in blood flow, total dialysate + ultrafiltrate, and net ultrafiltrate flow rates do result in significant alterations in IV pump pressure loads • Impact of IV pump pressure load changes on pump performance currently being analyzed