Measurement of cardiac output by the thermodilution method during left thoracotomy in the lateral position in the dog

The validity of cardiac output measurement by thermodilution in the lateral position during thoracotomy was assessed. Three balloon thermodilution Swan-Ganz catheters were placed in the pulmonary artery trunk and the right and left pulmonary arteries in 12 mongrel dogs, after left thoracotomy had been performed. Cardiac output was measured simultaneously from two of the three sites. The cardiac output measurements show no significant difference related to the location of the catheter extremities: the mean cardiac index was found to be 2.164 +/- 0.448 l/min/m2 from the pulmonary artery trunk, 2.127 +/- 0.404 l/min/m2 from the left branch and 2.116 +/- 0.421 l/min/m2 from the right branch. It is concluded that the measurement of cardiac output during left thoracotomy is valid, whether the thermistor is situated in the pulmonary artery trunk or in a main branch to either the dependent or non-dependent lung.