Desflurane inhibits hypoxic pulmonary vasoconstriction in isolated rabbit lungs.
BACKGROUND
Inhalational anesthetics inhibit hypoxic pulmonary vasoconstriction (HPV) in vivo and in vitro with a half-maximum inhibiting effect (ED50) within concentrations applied for general anesthesia. Because it is unknown whether desflurane acts likewise, we studied its effect on HPV in isolated blood-perfused rabbit lungs and compared its ED50 with that of halothane.


METHODS
Isolated blood-perfused rabbit lungs were randomly allocated to treatment with either desflurane (n = 6) or halothane (n = 6). HPV, defined as an increase in pulmonary arterial pressure (PAP) at constant flow, was elicited by decreasing inspiratory oxygen concentration from 20% to 3% for 4 min. This effect was determined without (control HPV) and with increasing concentrations of the anesthetics (fraction of inspired carbon dioxide kept constant at 4.8 +/- 0.2%, perfusate temperature at 37 degrees C, and blood flow at 100 ml.min-1).


RESULTS
Before exposure to the anesthetics, PAP increased by 8.6 +/- 1.9 cmH2O for all lungs within 4 min of hypoxia (control PAP for all lungs 19.6 +/- 2.5 cmH2O). Desflurane decreased this effect in a concentration-dependent fashion with an ED50 of 14.5%, compared with that of halothane, with an ED50 of 1.7%.


CONCLUSIONS
Assuming that 1 minimum alveolar concentration (MAC) values of desflurane and halothane for rabbits are 8.9% and 1.39%, respectively, this study yields ED50 values for the inhibition of HPV of approximately 1.6 MAC for desflurane and 1.2 MAC for halothane (P not statistically significant).
Loer
S A
SA
Department of Anesthesiology, Heinrich-Heine-University, Düsseldorf, Germany.
Scheeren
T W
TW
Tarnow
J
J
D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D015687:Cell Hypoxia; D000077335:Desflurane; D004305:Dose-Response Relationship, Drug; D005260:Female; D066298:In Vitro Techniques; D007530:Isoflurane / Q000031:analogs & derivatives* / Q000494:pharmacology; D008168:Lung / Q000098:blood supply / Q000187:drug effects*; D008297:Male; D011817:Rabbits; D014661:Vasoconstriction / Q000187:drug effects*
D018685:Anesthetics, Inhalation; D000077335:Desflurane; D007530:Isoflurane