Changes in the Doppler waveform of the ovine femoral artery following infusion of vasoactive agents: a preliminary study.

Abstract The aim of this study was to investigate whether femoral artery pulsatility index ( pi ) can be used as an indicator of vasomotor tone in the digit of an ungulate species by measuring the change in pi induced by infusion of vasoactive agents in halothane-anaesthetised sheep. Intra-arterial infusion of the vasoconstrictor phenylephrine (9  μg min −1 ) tended to increase waveform pi (3.89–6.24, n =4, P =0.100). Infusion of a low dose (3  μg min −1 ) of the vasodilator sodium nitroprusside did not alter femoral artery pi , however infusion of a higher dose (30  μg min −1 ) tended to increase pi (5.39–6.70, n =5, P =0.059). During these studies heart rate, mean abp and p a CO 2 did not change significantly. The tendency for pi to increase in response to vasodilation was unexpected and the mechanism involved is unclear. It appears that femoral artery pi cannot be used to predict vasomotor tone in the digit of the anaesthetised sheep.