title: Quantification of recirculation by thermodilution during venovenous extracorporeal membrane oxygenation.
abstract: 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.
authors.affiliation: Department of Pediatrics, University of Alberta, Edmonton, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Sreenan
authors.forename: H
authors.initials: H
authors.lastname: Osiovich
authors.forename: P Y
authors.initials: PY
authors.lastname: Cheung
authors.forename: R P
authors.initials: RP
authors.lastname: Lemke
mesh_terms: 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