Lithium dilution cardiac output measurement - a brief review

We have previously described a new indicator dilution method of measuring c ardiac output which is minimally invasive, requiring only central venous an d arterial catheters. These would probably already have been inserted in pa tients whose management would be helped by cardiac output measurement. The indicator is isotonic (150 mM) lithium chloride (LiCl) which is injected as a bolus via a central venous catheter. Arterial blood is sampled at 4 ml/m in through a disposable lithium sensor, which consists of a lithium-selecti ve electrode in a flow-through cell. The voltage across the lithium-selecti ve membrane is measured using an isolated amplifier and from this the lithi um dilution curve is calculated and cardiac output derived. Studies in huma ns and animals over a large range of cardiac output values have shown it to be safe, accurate and simple to use.