Abstract 889: Cardiac Output Measurements Acquired During Rapid Steady-State Infusions Are Accurate in a Flow Chamber Model, Except at the Start of Infusion
Introduction: Thermodilution cardiac output measurement (TD COM) using a pulmonary artery (PA) catheter is routine practice. There are reports that rapid simultaneous fluid infusion through the venous infusion port of the PA catheter limits the accuracy of TD COM, and in many centers, such infusions are stopped prior to TD COM. Here, we hypothesized that steady-state simultaneous fluid infusion, regardless of rate, has negligible effect on TD COM, while altering the rate of that infusion may indeed affect the TDCOM.
Method: A specialized flow chamber was constructed to model TD COM in the PA. Fluid was passed through a 1.5″ diameter tube at a constant flow and temperature (37.0°C). Into this tube, a PA catheter was inserted. Room temp fluid (10mL) was injected and the flow calculated with a GE Solar 8000M patient monitor (widely used for TD COM in the ICU). Fluid was infused into the venous infusion port of the PA catheter with an Alaris IVAC infusion pump. Flow was measured at infusion rates from 0 –999ml/hr with four measurements at each rate. Next, flow was measured at 1, 10 and 60 sec after changing the infusion rate to 999ml/hr from 0ml/hr.
Results: TD COM were unaffected by steady infusion rates (Panel A: Correlation coefficient r2=0.068). However, flow measured 1 sec after the start of rapid infusion (999ml/hr) was 0.3 L/min less than flow measured after 60 sec (Panel B. n=10, p=0.027). All data mean +/− standard error.
Conclusions: Simultaneous fluid infusions through the venous port of a PA catheter do not affect TD flow measurements unless a rapid infusion has been started within 1 min. The common clinical practice of halting infusions prior to TD COM may be unnecessary in most cases.