Quantification of recirculation by thermodilution during venovenous extracorporeal membrane oxygenation.
OBJECTIVE
The aim of this study was to determine whether recirculation could be quantified by a thermodilution technique during venovenous (VV) extracorporeal membrane oxygenation (ECMO) in a rabbit model.


METHODS
Five New Zealand white rabbits, mean weight, 4.5 (range, 3.7 to 5.7) kg, were anesthetized, instrumented, cannulated with a double-lumen catheter, and placed on VV ECMO. Serial injections of ice-cold saline were performed at the arterial arm of the circuit, and the resultant temperature change at various pump flows was measured at the venous arm of the circuit using a thermistor-tipped catheter and a cardiac output computer. Results were compared with the respective 100% recirculation measured with all the circuit flow passing through the bridge.


RESULTS
Using linear regression, recirculation percentage could be calculated as: 19 + 0.1 x pump flow (R2 = 0.81, P < .005). Recirculation correlated positively with pump flow. Variability between results at each flow was less than 10%.


CONCLUSIONS
Recirculation can be quantified during VV ECMO by measuring the change in temperature in the venous arm using a cardiac output computer after injection of a known quantity of ice-cold saline in the arterial side of the circuit. The effect of interventions to reduce recirculation can be assessed conveniently and reliably.
Sreenan
C
C
Department of Pediatrics, University of Alberta, Edmonton, Canada.
Osiovich
H
H
Cheung
P Y
PY
Lemke
R P
RP
D000818:Animals; D001831:Body Temperature; D002408:Catheters, Indwelling; D015199:Extracorporeal Membrane Oxygenation / Q000379:methods*; D005260:Female; D011652:Pulmonary Circulation / Q000502:physiology*; D011817:Rabbits; D013815:Thermodilution / Q000379:methods