Red Cell Aggregation from Concentrated Saline and Angiographic Media

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Abstract
Zahn in 1875 (1) observed aggregation of red blood cells in the mesenteric circulation of the frog following the topical application of salt crystals. A similar phenomenon was described by Read et al. (2) in various circulatory beds (mesenteric, subcutaneous, pulmonary, and pial) of dogs and cats after the intravascular administration of concentrated salt solutions including angiographic media. The purpose of the present study was to provide further information regarding this agglutinative and crenation property and, in particular, to document and extend our previous preliminary microscopic observations. Methods Adult mongrel dogs were anesthetized by the intravenous administration of pentobarbital sodium. The mesenteric circulation was microscopically examined and photographed by a technic which has been previously described (3). Observations were made before and after the intraarterial injections of 2 to 3 ml. of a solution of either 15 per cent sodium chloride or 90 per cent Hypaque. (The latter was employed because of its present popularity as a contrast agent in angiography.) Both a glass capillary system and a plastic microchamber were constructed to examine the in vitro response. The plastic mixing chamber was employed because the glass itself in the capillary system or the conditions of mixing may have had some effect upon the observed response. The glass capillary had a lumen of 50 micra, an outside diameter of 5 mm., and a length of 1 cm. To obtain good microscopic visualization, a section of the glass tube was ground and polished to within 0.3 mm. of the lumen; a plastic tray with a transparent bottom was fabricated around the tube and filled with an immersion oil which had an index of refraction similar to that of the glass. A 1-c.c. syringe was fastened in a micrometer caliper and connected to the glass tube via a polyethylene tube. A quantity of heparinized or oxalated whole blood (dog or human) or washed red cells suspended in saline was diluted with isotonic saline (control solution), 15 per cent saline, or 90 per cent Hypaque (test solutions). Sufficient amounts of the test solutions were added to give the mixtures an osmolarity of 600–800 M-osm∕L. This range was selected because in a previous study (4), it was shown to be the threshold level for a significant alteration in blood viscosity. A sample was transferred to the syringe, and flow was obtained by turning the micrometer dial to move the syringe plunger. The conditions of flow in the capillary were established microscopically and the results photographed at a shutter speed of 1∕125 to 1∕150 of a second. The plastic mixing chamber illustrated in Figure 1 had a “T” channel approximately 3 mm. wide and 50 micra deep.