Effect of pH, buffer and osmolality of different contrast media on aortic blood pressure in the rabbit

Intra-aortic injections in rabbits of contrast media with a lower osmolality (metrizamide, C29 and ioxaglate) caused significantly less decrease in aortic blood pressure than injections of contrast media with a higher osmolality (diatrizoate, metrizoate and iothalamate) at iodine equivalent concentrations. Increasing the acidity of metrizamide and C29 form pH 7.4 to 5.0 increased the blood pressure fall. Variation of the buffer (phosphate, TRIS and bicarbonate) in metrizamide and C29 solutions at physiologic pH did not cause any difference in response.