Electromagnetic flow-probe implantation for cardiac output measurements in rabbits

A technique suitable for continuous measurement of beat-to-beat cardiac output in conscious rabbits for relatively longer periods is described. The method consists, essentially, of implanting a specially constructed electromagnetic flow probe around either the pulmonary artery or the aorta during left thoracotomy (second intercostal space) in animals anesthetized with hypnorm. With care, the procedure is successful in a large proportion of the animals. Little postoperative care is required and the flow probe remains functional for several weeks up until the animals were killed to recover the probe for reimplantation. The cardiac output values (ml/min/kg) in conscious rabbits were: normal 183 +/- 9; unilateral renal hypertensive animals, 108 +/- 10 and bilateral renal hypertensive animals, 153 +/- 15. Isoprenaline increased, and propranolol decreased, the cardiac output in conscious normotensive rabbits.