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  • Title: Pulmonary vascular impedance vs. resistance in hypoxic and hyperoxic dogs: effects of propofol and isoflurane.
    Author: Ewalenko P, Stefanidis C, Holoye A, Brimioulle S, Naeije R.
    Journal: J Appl Physiol (1985); 1993 May; 74(5):2188-93. PubMed ID: 8335547.
    Abstract:
    The pulmonary vascular effects of inhaled anesthetics have been reported variably. We compared the effects of intravenous anesthesia (propofol) and inhalational anesthesia (isoflurane) on multipoint mean [pulmonary arterial pressure (Ppa)-pulmonary arterial occluded pressure (PpaO)]/cardiac output (Q) plots and on pulmonary vascular impedance (PVZ) spectra in eight dogs alternatively ventilated in hyperoxia [inspired O2 fraction (FIO2) 0.4] and in hypoxia (FIO2 0.1). Q was altered by a manipulation of venous return. During propofol, hypoxia increased (Ppa-PpaO) by an average of 2-3 mmHg over the entire range of Q studied, from 1 to 2.5 l.min-1 x m-2. This hypoxic pulmonary vasoconstriction (HPV) was associated with insignificant changes in PVZ. Decreasing Q in hypoxia and hyperoxia did not affect PVZ. Compared with propofol, isoflurane decreased (Ppa-PpaO) by an average of 2-5 mmHg at all levels of Q studied in both hypoxia and hyperoxia but did not affect HPV. During isoflurane anesthesia, 0 Hz PVZ was lower (P < 0.01) in hypoxia, but otherwise the PVZ spectrum was not different from that recorded during propofol anesthesia. We conclude that, in dogs, 1 degree general anesthesia with isoflurane alone decreases pulmonary vascular tone without inhibition of HPV and that 2 degrees pressure/Q plots in the time domain are more sensitive than those in the frequency domain to subtle hemodynamic changes induced by hypoxia or isoflurane at the periphery of the pulmonary vasculature.
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