Cardiac output measurement in ventilated lambs with a significant left-to-right shunt using the modified carbon dioxide fick method.
BACKGROUND
It remains a great challenge to measure systemic blood flow in critically ill newborns. In a former study we validated the modified carbon dioxide Fick (mCO(2)F) method for measurement of cardiac output in a newborn lamb model. In this new study we studied the influence of a left-to-right shunt on the accuracy of the mCO(2)F method.


OBJECTIVE
To analyze the influence of a left-to-right shunt on the agreement between cardiac output measurement with the mCO(2)F method and ultrasonic transit time pulmonary blood flow in a lamb model.


METHODS
The study was approved by the Ethical Committee on Animal Research of the Radboud University Nijmegen and performed in 8 random-bred lambs. A Gore-Tex shunt was placed between the left pulmonary artery and the descending aorta. This aortopulmonary shunt was intermittently opened and closed, while cardiac output was manipulated by creating hemorrhagic hypotension. Cardiac output measurement with the mCO(2)F method (Q(mCO2F)) was compared with pulmonary blood flow obtained by a transit time ultrasonic flow probe positioned around the common pulmonary artery (Q(APC)).


RESULTS
Bias, defined as Q(mCO2F) - Q(APC), was calculated for each measurement. With an open shunt there was a significant left-to-right shunt (mean Qp/Qs ratio 2.26; range 1.56-3.69). Mean bias (SD) was -12.3 (50.4) ml x kg(-1) x min(-1) and -12.3 (42.7) ml x kg(-1) x min(-1) for measurements with a closed and open shunt, respectively (no statistical significant difference).


CONCLUSIONS
Cardiac output measurement with the mCO(2)F method is reliable and easily applicable in ventilated newborn lambs, also in the presence of a significant left-to-right shunt.
de Boode
Willem P
WP
Department of Neonatology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. W.deBoode@cukz.umcn.nl
Hopman
Jeroen C W
JC
Wijnen
Marc H W A
MH
Tanke
Ronald B
RB
van der Hoeven
Hans G
HG
Liem
K Djien
KD
D000818:Animals; D000831:Animals, Newborn; D001011:Aorta / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood*; D002302:Cardiac Output / Q000502:physiology*; D023421:Models, Animal; D008955:Models, Cardiovascular; D008991:Monitoring, Physiologic / Q000379:methods* / Q000592:standards; D011652:Pulmonary Circulation / Q000502:physiology; D015203:Reproducibility of Results; D012121:Respiration, Artificial; D012756:Sheep
D002245:Carbon Dioxide