Accuracy of CVVH on ECMO : A comparison of IV pump versus Braun Diapact driven systems Matthew L. Paden, MD Division of Pediatric Critical Care Emory University Children’s Healthcare of Atlanta at Egleston

The Clinical Problem Multiple ECMO/CVVH patients who are 10+ liters positive on paper, yet are clinically dehydrated Hypothesis : Both IV pump and Braun Diapact driven CVVH systems when used with ECMO have error rates greater than 5% / hour.

Methods for CRRT on ECMO Commercially available CRRT machines B Braun Diapact Edwards Aquarius Fresenius Gambro Prisma/Prismaflex Advantage – Standardized equipment, “built for the purpose”

Methods for CRRT on ECMO IV Pump Driven Described by Weber, et al 1998 IV pumps used to create ultrafiltrate and deliver replacement fluid Ultrafiltrate is measured using a urometer Advantage – low cost, no additional training for ECMO specialists, less extracorporeal blood volume

The Problem Inaccuracy has been described in CRRT in patients not on ECMO The pumps are the problem PCRRT 2000 – 7% extra ultrafiltrate removed 2% less replacement fluid delivered ASAIO 1992 – Up to 12.5% error rate Error correlates with pressure drop across membrane and pump type

Alaris Pump Accuracy Sucosky et al. Awaiting publication. 2008

Methods Two identical saline primed ECMO circuits Stockert S3, ½ inch drain, 3/8 inch return 4.5 m2 Medtronic oxygenator PAN 6 hemofilter CVVH prescribed : IV pump vs. Diapact Net even fluid balance Varying ultrafiltration rates (0.5 – 2 L / hour) Hourly weights of UF/Replacement bags, circuit pressures

Results 48 hourly measurements 26 hours Alaris 22 hours Diapact No correlation between error rate and Prescribed ultrafiltration rate ECMO flow rate CVVH blood flow rate

Results - Alaris Created a median 0.8% less ultrafiltrate per hour than prescribed (+7% to -12%) Delivered a median of 4.3% less replacement fluid per hour than prescribed (+3% to -25%) NET 3.5% of prescribed UF per hour dehydration to patient

Examples with Alaris 4 kg neonate on ECMO with 100 ml/hour prescribed UF rate and even fluid balance 84 ml (21 ml/kg) fluid negative per day 10 kg child on ECMO with 300 ml/hour prescribed UF rate and even fluid balance 252 ml (25 ml/kg) fluid negative per day 45 kg child on ECMO with 2000 ml/hour prescribed UF rate and even fluid balance 1.68 L (37 ml/kg) fluid negative per day

Results - Diapact Created a median 1% more ultrafiltrate per hour than prescribed (+6% to -8%) Delivered a median of 1% more replacement fluid per hour than prescribed (+10% to -7%)

Examples Braun Accurate when looking at medians over time Hourly variation could be important in a hemodynamically unstable patient Hourly Fluid Balance -5 35 10 -40 -10 -30

Conclusions In this in vitro CVVH/ECMO model Both the Alaris and Diapact methods had error rates that could be clinically significant Careful physical assessment of the patient’s volume status is necessary Further work is needed to develop more a accurate fluid management system for CRRT on ECMO