Prevention and dispersion of contrast media induced red cell aggregates. An in vitro study.

Red cell aggregation was observed microscopically when human blood and contrast media were mixed on glass slides. Aggregation was more frequent in low-osmolal media: mainly rouleaux were formed in ioxaglate but irregular aggregates in non-ionic media. Aggregation was similar at concentrations of 150 and 300 mg I/ml. Pre-treatment of glass slides with heparinized saline reduced red cell aggregation but saline alone was almost as effective. Most of the irregular aggregates dispersed when saline or heparinized saline was applied to them. Saline and heparinized saline had an identical dispersing effect. After incubation of the aggregates in iopamidol in plastic tubes for one or five minutes, saline was injected into the tubes, and after mixing the solution was poured onto glass slides and examined under the microscope. Only a few small irregular aggregates were detected in 6/60 specimens. It is concluded that ionicity of a flushing medium and shear of the injection are able to disperse red cell aggregates during angiography.