Addition of Local Anesthetics to Contrast Media

Abstract

Effects of equiosmolar solutions (osmolality 1.35 mol/kg) of the ratio 1.5 contrast medium metrizoate (250 mg I/ml) containing either the local anesthetic mepivacaine or saline were evaluated on subjective discomfort, aortic blood pressure and heart rate in 17 patients referred for aortofemoral angiography due to intermittent claudication. Each patient was injected with 30 ml (15 ml/s) of each solution in random double-blind order. Each patient was then injected with 45 ml (12 ml/s) of the ratio 3 medium ioxaglate (320 mg I/ml, osmolality 0.58 ml/kg). Ioxaglate caused significantly less total discomfort, pain, heat, vocal reactions, involuntary movements and hemodynamic effects than metrizoate-mepiva-caine and metrizoate-saline. The effects of the two metrizoate solutions did not differ significantly. Previous contradictory reports on the effects of anesthetics in contrast media were reviewed with regard to experimental design, different osmolality of the test and control solutions, premedication, and pH dependence of local anesthetics. Ratio 3 media are recommended because they produce a more reliable relief of patient discomfort and fewer hemodynamic changes than the addition of local anesthetics to ratio 1.5 media.