Effects of injection site and flow rate on the distribution of injected solutions in an extracorporeal membrane oxygenation circuit
Hoie, E.B.; Hall, M.C.; Schaaf, L.J.
American Journal of Hospital Pharmacy 50(9): 1902-1906
1993
ISSN/ISBN: 0002-9289 PMID: 8135237 Document Number: 421330
The effects of injection site and flow rates on drug distribution within an extracorporeal membrane oxygenation (ECMO) circuit were studied. Two commercially available reservoirs (30 mL and 50 mL) were connected to a closed ECMO circuit that did not include the membrane oxygenator and heater. The circuit was filled with 150-170 mL of a 9.5% dextran solution in deionized, distilled water with a viscosity approximating that of blood. Flow rates of the circulating solution were set at 75 mL/min and 375 mL/min. Bordeaux red dye was injected into an ECMO circuit at prereservoir, postreservoir, and intrareservoir sites, and samples were obtained from these sites for analysis. Gentamicin was also injected at the prereservoir site, with samples obtained from the reservoir, reservoir tubing, and the prereservoir and postreservoir sites. Postreservoir dye injections resulted in complete mixing at any flow rate. Prereservoir injections at flow rates less than 250 mL/min resulted in incomplete mixing of dye, whereas intrareservoir injections resulted in incomplete mixing at any flow rate. Gentamicin injection was also affected by flow rate, resulting in higher concentrations within the reservoir and reservoir tubing. In patients on ECMO, drug distribution may be substantially altered if drugs are given as a bolus at prereservoir or intrareservoir sites. Efforts should be made to select injection sites that will provide safe and therapeutic drug delivery while minimizing the effects of the ECMO circuit on drug distribution.