Dye-dilution cardiac output without blood withdrawal in the conscious rabbit

Cardiac output can be measured in the conscious rabbit without blood withdrawal by use of a modified dye-dilution method. Blood flows continuously from the central ear artery through a Silastic catheter that passes through a modified cuvette lumen and back into an ear vein. Blood flow through this shunt was 1.5 ml/min. This modified technique was evaluated by comparison with a simultaneously performed cardiac output measurement using radioactive microspheres and by making consecutive dye-dilution measurements at short time intervals. A correlation coefficient of 0.96 was obtained when comparing dye-dilution and microsphere cardiac outputs. The difference between 11 paired measurements was 7.09 +/- 5.24% (mean +/- SD). Consecutive outputs measured within 3 min of each other by the flow-through technique had a correlation coefficient of 0.99 and a difference between the first and second determinations of 3.52 +/- 2.38%. The method permits dye-dilution cardiac output measurement in the conscious rabbit while avoiding the potential error caused by blood withdrawal from small animals.