The effect of nonionic radiographic contrast medium on serum electrolytes and proteins during intravenous urography

A prospective study was done on 20 adult patients to determine changes in the serum electrolytes and proteins produced by bolus administration of 100 ml of the nonionic contrast medium iohexol (Omnipaque 300) for intravenous urography. Blood samples were taken for analysis before injection and at five and 30 minutes after. Statistically significant decreases in serum sodium, potassium, total protein, albumin, calcium, and phosphate were noted at five minutes post-injection (p less than 0.001). The mean percentage decreases were sodium 2.4%, potassium 5.1%, total protein 13.7%, albumin 14.2%, calcium 8.6%, and phosphate 5.3%. These values were significantly decreased after 30 minutes (p less than 0.001) except for the serum potassium concentration which had almost returned to baseline level. The changes in sodium, potassium, and phosphate are small and thought to be secondary to hemodilution due to the osmolality of the contrast. The changes in total protein, albumin, and calcium were much greater and difficult to explain. Although we found significant changes in serum biochemistry and proteins, these did not appear to cause clinical abnormalities in this group of patients.