Tendency to acidosis following the injection of radio-opaque contrast material

Abstract

Fifty patients were investigated during routine carotid angiography under general anaesthesia. The procedure tended to produce a metabolic acidosis, the mean change in base for the group being -2.3 mEq/liter. Those patients starting with a base excess showed the greatest change (-3.2 mEq/1.) and those starting with a base deficit the least (-1.7 mEq/1.). The change is attributed to the injection of the contrast material meglumine iothalo-mate ("Conray 280"). In vitro experiments showed a comparable change in base when blood and contrast were mixed in proportions similar to those obtaining clinically. CO2 retention enhanced the tendency to acidosis. No satisfactory explanation could be found for the wide variation in the response of different individuals. The degree of change was not correlated with age, sex, weight or physical state of the patients, nor with duration or type of anaesthesia. This tendency to acidosis may in part be responsible for the occasional untoward reaction to the injection of contrast.