Determination of cardiac output at the ascending aorta with an extravascular Doppler ultrasound probe in comparison with aortic thermodilution

Currently, no reliable minimally invasive method of measuring cardiac outpu t continuously in neonates and children undergoing cardiac surgery is avail able. An extravascular Doppler probe was used to measure cardiac output in 15 New Zealand White rabbits (average weight 3.5 kg, range 2.5-4.5 kg). The results obtained were compared with cardiac outputs determined using the a ortic thermodilution principle. The mean cardiac outputs measured with the extravascular Doppler probe was 0.37 +/- 0.01 l/min as compared with 0.39 /- 0.01 l/min with aortic thermodilution. Regression analysis revealed a cl ose correlation (r = 0.973) between the two techniques. The extravascular D oppler techniques is an option for continuous and reliable cardiac output m easurement in small animals used in surgical experiments (open chest models ) and in neonates or children during surgical repair of complicated congeni tal heart conditions.