Radiology, Vol 147, 677-679, Copyright © 1983 by Radiological Society of North America
Systemic hypocalcemia after clinical injections of radiographic contrast media: amelioration by omission of calcium chelating agents
LE Mallette and LS Gomez
Intravascular injection of some radiographic contrast media causes a fall
in the concentration of unbound serum calcium (Ca++) and an increase in
serum immunoreactive parathyroid hormone (iPTH). The decrease in Ca++
levels was attributed to the presence in the contrast media of calcium
chelating agents (disodium edetate and sodium citrate) and to the effects
of high ionic strength and hemodilution on calcium ion activity. In the
present study, we have tested whether omission of the calcium chelating
agents from solutions of diatrizoate will lessen the alterations in
systemic calcium metabolism. We compared Renografin- 76 (RG-76)
(diatrizoate meglumine and diatrizoate sodium), which contains disodium
edetate and sodium citrate, with Hypaque-76 (H-76) (diatrizoate meglumine,
diatrizoate sodium), which contains no calcium chelating activity. A bolus
injection of a mean dose of 62 ml of either contrast medium decreased
levels of Ca++ significantly (P less than 0.01) at five minutes. The
decrease was significantly greater (P less than 0.025) with RG-76 (0.096
+/- 0.018 mM, mean +/- SE) than it was with H-76 (0.049 +/- 0.018 mM, mean
+/- SE). The level of iPTH increased (P less than 0.01) by 68 +/- 13
nanoliter equivalents (nleq) per ml with RG-76 and by 28 +/- 8 nleq per ml
with H-76 (P less than 0.01 vs RG-76). In vitro, RG-76 decreased levels of
Ca++ in aqueous calcium solutions 3.7-fold more than did H-76, but neither
contrast medium had any direct effect on the parathyroid hormone assay
system. Omission of divalent cation chelating agents from solutions of
diatrizoate reduces their effects on systemic calcium metabolism.
