Effects of angiographic contrast media on colloid oncotic pressure

Angiographic contrast media are known to induce alterations in cardiovascular dynamics which may result in acute pulmonary edema. The risk of pulmonary edema was previously shown to be negatively correlated to the level of colloid oncotic pressure (COP). It was also shown that the gradient between COP and left ventricular end-diastolic pressure (LVEDP) represents a better predictor of pulmonary edema than does LVEDP alone. The present report evaluates the effects of a bolus injection of contrast media on those pressures, as predisposing factors for pulmonary edema. Our data are based on 15 unselected patients admitted for coronary angiography. The plasma volume increased by 16.5% (2,903 to 3,384 ml.) at two minutes after injection of a 50 c.c. bolus of meglumine diatrizoate (Renographin 76%) and had returned towards normal at 30 minutes. In parallel the COP decreased from 23.4 +/- 2.4 to 19.6 +/- 2.3 mm. Hg (p < 0.001) to return the 22.7 +/- 2.6. The COP-LVEDP gradient decreased by 8.7 mm. Hg (8.4 to -0.3, P < 0.001). Such a gradient was well within the danger zone of pulmonary edema. These findings further clarify the mechanisms of pulmonary edema induced by contrast media.