title: Cardiac output can be measured with the transpulmonary thermodilution method in a paediatric animal model with a left-to-right shunt.
abstract: BACKGROUND
  The transpulmonary thermodilution (TPTD) technique for measuring cardiac output (CO) has never been validated in the presence of a left-to-right shunt.
  
  
  METHODS
  In this experimental, paediatric animal model, nine lambs with a surgically constructed aorta-pulmonary left-to-right shunt were studied under various haemodynamic conditions. CO was measured with closed and open shunt using the TPTD technique (CO(TPTD)) with central venous injections of ice-cold saline. An ultrasound transit time perivascular flow probe around the main pulmonary artery served as the standard reference measurement (CO(MPA)).
  
  
  RESULTS
  Seven lambs were eligible for further analysis. Mean (sd) weight was 6.6 (1.6) kg. The mean CO(MPA) was 1.21 litre min(-1) (range 0.61-2.06 l min(-1)) with closed shunt and 0.93 litre min(-1) (range 0.48-1.45 litre min(-1)) with open shunt. The open shunt resulted in a mean Q(p)/Q(s) ratio of 1.8 (range 1.6-2.4). The bias between the two CO methods was 0.17 litre min(-1) [limits of agreement (LOA) of 0.27 litre min(-1)] with closed shunt and 0.14 litre min(-1) (LOA of 0.32 litre min(-1)) with open shunt. The percentage errors were 22% with closed shunt and 34% with open shunt. The correlation (r) between the two methods was 0.93 (P<0.001) with closed shunt and 0.86 (P<0.001) with open shunt. The correlation (r) between the two methods in tracking changes in CO (ΔCO) during the whole experiment was 0.94 (P<0.0001).
  
  
  CONCLUSIONS
  The TPTD technique is a feasible method of measuring CO in paediatric animals with a left-to-right shunt.
authors.affiliation: The Department of Intensive Care Medicine, Radboud University Nijmegen Medical Centre, Nijmegen,The Netherlands. a.nusmeier@ic.umcn.nl
authors.forename: A
authors.initials: A
authors.lastname: Nusmeier
authors.forename: W P
authors.initials: WP
authors.lastname: de Boode
authors.forename: J C W
authors.initials: JC
authors.lastname: Hopman
authors.forename: P H
authors.initials: PH
authors.lastname: Schoof
authors.forename: J G
authors.initials: JG
authors.lastname: van der Hoeven
authors.forename: J
authors.initials: J
authors.lastname: Lemson
mesh_terms: D000818:Animals; D001011:Aorta / Q000502:physiology; D002302:Cardiac Output; D004195:Disease Models, Animal; D006330:Heart Defects, Congenital / Q000503:physiopathology*; D011652:Pulmonary Circulation; D012756:Sheep; D012771:Shock, Hemorrhagic / Q000503:physiopathology; D013815:Thermodilution / Q000379:methods*