COMPARISON OF TRANSTRACHEAL AND EXTRAVASCULAR DOPPLER DETERMINATIONS OF STROKE VOLUME AND CARDIAC-OUTPUT AT VARIOUS STATES OF VOLUME LOADING IN PIGLETS

Objective: To assess the applicability of a new technology in neonates . Transtracheal Doppler and extravascular Doppler determinations of st roke volume and cardiac output were compared with thermodilution measu rements at various states of volume loading in an animal model. Design : Prospective, descriptive study. Setting: Animal research laboratory at; a university medical center. Subjects: Fourteen newly weaned pigle ts, weighing 2.8 to 6.5 kg. Interventions: Doppler probes were placed on the endotracheal tube tip (transtracheal Doppler) and directly on t he aortic adventitia (extravascular Doppler). A 4-Fr thermodilution ca theter was inserted in the pulmonary artery, Stroke volume and cardiac output determinations were recorded at baseline, after a 15-mL/kg vol ume load and after successive 15-mL/kg blood withdrawals to exsanguina tion or a systolic blood pressure of <20 mm Hg. Measurements and Main Results: Transtracheal and extravascular Doppler measurements of cardi ac output were not significantly different from thermodilution at any physiologic state. These techniques were able to measure stroke volume s and cardiac outputs at the low levels seen in severe hemorrhagic sho ck. Conclusions: Transtracheal Doppler and extravascular Doppler measu rements of cardiac output compare favorably with thermodilution. These methods effectively followed trends from alterations in intravascular volume, even at very high heart rates and small stroke volumes. Trans tracheal Doppler and extravascular Doppler should yield useful informa tion in critically ill neonatal patients, where data regarding stroke volume and cardiac output may be useful in clinical management.