Use of conjunctival oxygen index for evaluation of cardiac output in dogs.

The relationship between the palpebral conjunctival oxygen (PcjO2) index, mixed venous oxygen tension (PvO2), and cardiac index were compared, using a canine hemorrhagic shock model. The cardiac output was reduced by reducing the blood volume in 5% increments until the initial cardiac output was reduced by one half. In each of 7 dogs, the PcjO2 index and PvO2 were found to have good correlation with cardiac index; however, the correlation coefficients were markedly reduced when the data from all of the dogs were combined. It was concluded that PcjO2 index provides an excellent means of assessing changes in cardiac index over time in the same dog; however, it cannot be used to estimate cardiac index in an individual dog with a degree of accuracy that would be clinically significant.