(Copyright of this paper remains with the British Journal of Anaesthesia. We are grateful for permission to reproduce some material from this paper.)
This was the first clinical trial and therefore many of the details of the method were slightly different from those of the present system.
Objective
Study population
Design
Evaluation
There are several potential sources of error in the LDCO method. The wrong dose of lithium chloride might be injected; this would produce a proportional error in the derived cardiac output. Lithium might have been lost between the point of injection (central vein) and the point of detection by the sensor. This could have been due to loss in the lungs, binding to protein or uptake by red cells. If such loss occurred, then the lithium dilution curves produced would have been too small and consequently cardiac output would have been overestimated. By adding aliquots of lithium chloride to whole blood in vitro we showed that there was no measurable reduction in plasma lithium concentration over a period of 30 min. In a further study in which lithium chloride was injected into the right or left atrium of patients and the curves compared, no significant loss of lithium was found. Another potential source of error is non-constancy of flow past the sensor, which might occur if the arterial catheter kinked. This would cause the recorded curve to deviate from the lognormal and this would be apparent on inspection of the curves.
Deviations from protocol
Adverse events
Comment