The effect of antihistamine, endothelin antagonist and corticosteroid prophylaxis on contrast media induced bronchospasm

Bronchospasm is a well recognized adverse reaction to radiographic contrast media (RCM) and may occur more frequently in asthmatics and atopics. This study was designed to identify RCM which are most likely to cause bronchosp asm and to investigate underlying mechanisms mediating this response. Guine a pigs (mean body weight 550 g, n=46) were anaesthetized with Hypnorm (5 mi kg(-1)) and Hypnovel (2 mi kg(-1)) and tracheal, jugular and pleural cannu lae introduced. Total airways resistance (Raw) was calculated from the slop e of the pressure/flow relationship. The effects of RCM (diatrizoate 370 mg I ml(-1), ioxaglate 320 mgI ml(-1), iotrolan 300 mgI ml(-1) and iopromide 3 00 mgI ml(-1)) at a dose of 4 mi kg(-1) body weight or control solutions ma tched for volume, pH and osmolarity administered via the jugular vein on Ra w were studied. The effects of pre-treatment (30 min before the administrat ion of RCM) with antihistamine (Mepyramine (30 mg kg(-1)ip)) or non-selecti ve endothelin receptor antagonist (SB209670 (1 mg kg(-1)iv)) were investiga ted. The effectiveness of corticosteroids prophylaxis (prednisolone (20 mg kg(-1)ip)) administered 18-24 h and 1 h pre-RCM was also assessed. Control animals received normal saline pre-treatment before RCM administration. Lun gs were taken for histological examination 30-40 min post-administration of RCM. Only ioxaglate caused a significant (p<0.05) increase in Raw (5.19+/- 0.58 to 13.95+/-3.53 mmHg ml(-1) min(-1)). Neither mannitol nor saline cont rol solutions had any effect on Raw. Pre-treatment with Mepyramine, SB20967 0 or prednisolone caused no significant change in the ioxaglate induced inc rease in Raw. Histological examination of lung tissue from ioxaglate treate d animals showed no important abnormalities. In summary, only the ionic dim er ioxaglate caused an increase in Raw. This effect was independent of osmo larity and could be the result of the chemical composition of the contrast agent. It was not an inflammatory response and could not be prevented by pr ophylactic treatment with antihistamine, endothelin antagonist or corticost eroids. The mechanisms responsible for the increase in Raw remain uncertain .