Answer: Measurement of CO by lithium dilution is based on the same principles as the thermodilution techniques. Isotonic lithium chloride is injected as a bolus. It mixes with the venous blood as it travels through the right heart, pulmonary circulation, left heart, and the aorta. The concentration-time curve of the indicator is, in contrast to the thermodilution methods, routinely generated in a peripheral artery (A-line) by the use of an ion-selective electrode.
It is contra-indicated in
- patients receiving lithium therapy
- patients who are less than 40 kg in weight and
- patients in the first trimester of pregnancy