Anoxic protection of small intestine of dogs by intra-arterial catheterization.

Abstract

Repression of the immune response by whole-body irradiation makes possible homografting of various organs, including bone marrow. For the most part, such grafts are temporary, a primary factor in their destruction being recovery of the immune response of the host. This recovery is delayed as the amount of whole-body irradiation is increased (1). Untreated dogs receiving 1,000 to 1,100 r whole-body irradiation in one sitting usually die the intestinal type of death within three to five days. Dogs receiving a lesser though lethal dose die after five days but within thirty days. Death has been associated with bone-marrow failure. Swift and Taketa (2) shielded 6 to 8 per cent of the small intestine of rats, thereby protecting them from intestinal death. Osborne (3) removed the irradiated segment of the small intestine of rats and prevented intestinal death. From these experiments it seems likely that the immediate cause of death from the intestinal radiation syndrome may be electrolyte loss. If the animal survives beyond five days, healing of the intestinal mucosa can take place rapidly. Successful homografting of bone marrow might permit increased doses of whole-body irradiation in the treatment of leukemia and disseminated cancer. The technic might also be used in conjunction with increased amounts of chemotherapeutic agents. These last are frequently toxic to the bone marrow and small intestine. The objective of the present experiment was to determine the degree of protection against whole-body irradiation afforded by intraarterial occlusion of the superior mesenteric artery. The effect would be mediated through anoxia. Procedure Balloons, distensible to 2 c.c, were placed 2 cm. from the blind end of Ödman catheters (Fig. 2). After these were soaked in heparin, they were introduced into the femoral arteries of 4 dogs and passed into the superior mesenteric arteries under fluoroscopic guidance, using an image intensifier. The adjacent femoral vein was catheterized so that the location of the balloon could be proved by intravenous aortography. The balloon was inflated with a mixture of Hypaque and methylene blue. Hypaque permitted post-irradiation checking of the position and competence of the balloon. Appearance of the blue dye at the exterior end of the catheter during irradiation would indicate loss of distention. The balloon was distended five minutes before irradiation to allow time for the tissues to become anoxic. A plain Ödman catheter was passed into the aorta of 3 control dogs via the femoral artery. Irradiation was delivered at 250 kvp, h.v.l. of 1.75 mm. Cu, and target-skin distance of 100 cm. As can be seen in Figure 1, the animal is placed in a curved container so that one entire side is 100 cm. from the target. After 550 r in air was delivered, the dogs were turned so that the opposite side faced the target, and another 550 r was delivered. The dogs were anesthetized during irradiation with sodium pentobarbital.