The ear oximeter as a circulatory monitor

In a previous report we demonstrated that, by making a simple modification in the method of recording the ear oximeter, one is able to obtain, in addition, a record of blood flow in the ear which is closely related to cardiac output. In this paper, we report our observations on the relationship between this measure of cardiac output and the actions of vasoconstrictor drugs during cardiac surgery. In some instances, we have seen a rise in cardiac output with a rise in blood pressure; while in others, there has been an accompanying fall in cardiac output. The method offers itself as a very convenient way of assessing the actions of the various vasopressor drugs on cardiac output. In instances where a rise in blood pressure produced by the vasopressor is not accompanied by an increase in cardiac output, all vasopressor therapy is abandoned or a change is made to a more suitable drug.