The bronchial vasodilatory response to ionic and non-ionic contrast
media.
Baile, Elisabeth M, Lu Wang, Lorraine Verburgt, and Peter D.
Par[acute]e.
UBC Pulmonary Research Laboratory, St Paul's Hospital, Vancouver,
Canada, V6Z 1Y6
APStracts 3:0524A, 1996.
Although we have recently shown that bronchial arterial injection of
conventional contrast medium causes a significant increase in
bronchial blood flow (QBr) and that this response is partially
attenuated after infusion of N-omega-nitro-L-arginine (LNA), we were
not able to determine the precise mechanism for this increase in QBr.
In this study we examined the effect of bronchial arterial (ba)
injection of conventional ionic as well as non-ionic contrast media.
We measured QBr in 9 anesthetized ventilated, open-chested sheep. QBr
was recorded before (baseline) and at the peak response to injection
of 0.5 ml of either 0.9% saline (control, isosmolar with plasma),
Omnipaque (iohexol: non-ionic), Conray 66 (sodium iothalamate: ionic)
or 50% Dextrose (viscous control). Measurements were made during a
control period; after infusion of the alpha-agonist phenylephrine (5
x 10-6 to 5 x 10-7 M), and after bronchial arterial infusion of LNA,
10 -2 M. Results: Ba injection of Saline, Omnipaque, Conray and
Dextrose caused an increase in QBr (P<0.05). During the
control period increases in peak QBr on injection of Saline,
Omnipaque, Conray and Dextrose were 55+/-29%, 112+/-62%, 280+/-99%
and 388+/-125% of baseline, respectively. Ba-infusion of LNA lowered
baseline QBr and partially attenuated the response to injection of
Saline, Omnipaque and Conray (P<0.05). Phenylephrine, in doses
which decreased baseline QBr to the same extent as LNA, did not
attenuate the bronchial vasodilation. There was a linear relationship
between osmolality and the percentage increase in bronchial blood
flow. We conclude that an osmolar stress is the trigger for the
contrast-induced bronchial vasodilation and that the response is
partially mediated by endothelial release of NO.
Received 13 August 1996; accepted in final form 5 November 1996.
APS Manuscript Number A775-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996