Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3860_Библиотеки_им_академика_М_И_Перельмана

Often patients experience increased pain during the lysis, which may be due to lysis and embolization of small clots. With continued infusion, these episodes are usually

This chapter outlines general principles of embolic and chemoembolic therapy, with particular attention to the techniques used and to which clinical entities may benefit from such catheter directed therapy.

which do not appreciably risk occluding the catheter. By using a coaxial system, the operator may catheterize the vessel of choice virtually without regard to vessel size, thus significantly decreasing the risk of both nontarget emboli­zation and damage to the underlying vessel.

When large particles such as Gelfoam pledgets are used for embolization, care must be taken to use a selec­tive catheter or coaxial system with an inner diameter and taper large enough to prevent occlusion of the catheter by the embolic material. A catheter with an end-hle only also should be used to prevent inadvertent nontarget embolization through a catheter side hole. In addition, if an adhesive material such as cyanoacrylate is used, the glue must be mixed with tantalum powder for radiopacity and the deliver y catheter must be flushed with dextrose solution, because exposure of the glue to ionic com­pounds causes instant polymerization and catheter occlu­sion.

bined approach using multiple agents is often most use­ful.

To choose the embolic agent needed, the anticipated end result of the embolization procedure must be under­stood. For instance, embolization for bleeding from a posttraumatic pseudoaneurysm has a different goal from embolization/ablation of a renal tumor preoperatively. Similarly, embolization for bleeding from a renal tumor has a purpose different from that of preoperative emboli­zation of the same pathology. Large embolic agents such as coils and Gelfoam pledgets may be used for emboliza­tion of large vessels in organs with abundant collateral supply, such as the stomach or liver, in which proximal vessels can be occluded safely without risk of tissue in­farction due to the extenssive collateral network. Large agents may be also used in tissues with an end-organ vascular supply in which the entire blood supply to the area of interest is to be occluded; however, large agents should not be used in vessels in which future emboliza­tion or transcatheter therapy is anticipated. By occlusion of the only vascular supply to a region, future selective catherization will be precluded by occluding the sole vascular access to the pathology. In contrast to large agents, liquid agents such as alcohol or glue will embolize to the most distal vascular supply and cause infarction by occluding the smallest arterioles supplying a lesion. Be­cause collateral supply occurs at a site proximal to the embolization, liquid embolization is effective in destroy­ing tissue even when there is significant parasitization or collaterization of blood supply from an adjacent source; however, it should not be used unless cell death and necrosis are the desired end results.

Embolization with particulateagents isconsidered com­plete when slowing of flow, not complete statis, is visual­ized. Because all arteries will tend to “back thrombose” to the previous bifurcation point when a distal occlusion is encountered, excessive embolization will decrease out­flow enough that the entire feeding artery may throm­bose. Fluoroscopically noted reflux is another indicator that the embolization procedure should be stopped.

Hemorrhage is a clinical setting in which transcatheter embolotherapy may prove useful. Embolization of active bleeding almost always provides a less invasive form of patient management than surgical alternatives, and in certain clinical settings, such as postradiation or postsur­gical fields, it may prove to be the only viable alternative because of the difficulty of surgery in such an operative field. Active bleeding may be caused by a number of etiologies, including inflammation, neoplasm, trauma, and congenital or developmental abnormalities. Once again, the desired end result of the embolization and the degree of permanence required are essential factors in determining the embolic agent of choice.

may benefit from emergent embolotherapy preceding, or in lieu of, surgical therapies.

Similar suc­cess rates have been noted in other studies for pathology as varied as jejunal ulcers, pseudoaneurysms, and Meckel’s diverticulum.

tysis.

In addition to inflammatory causes of bleeding, emboliza­tion may be used in patients presenting with hemorrhage following trauma; However, in the setting of trauma the underlying nature of the vessels as well as the desired endpoint differ greatly from those seen in the setting of chronic inflammatory disease. In mostinstances, posttrau­matic bleeding involves previously healthy vessels that un­dergo acute changes such as transection or pseudoaneu­rysm formation; temporizing measures are frequently all that are required to allow the vessel to undergo the heal­ing process or to stabilize the patient preoperatively. Be­cause of these differences, the embolic agents differ from those seen with hemorrhage from chronic inflammatory diseases.

The most common sources of arterial hemorrhage fol­lowing pelvic trauma are branches of the internal iliac arteries (Fig. 8-1). Cut-film angiography is the preferred method for initial diagnostic angiography done because of the presence of bowel motion artifact in the pelvis during digital subtraction angiography (DSA), although DSA may be sufficient in patients who are hemodynami­cally unstable and in whom time is crucial. It is recom­mended that distal aortogram be done before selective catheterization of the internal iliac arterie is performed because of the possibility of concomitant arterial damage