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220 PART 2: General Management of the Patient

window of time to evaluate for bleeding. A positive CTA study will show distal esophagus, cardia, or stomach fundus. The GDA is embolized for
hyperdense contrast material within the bowel lumen on the arterial bleeding originating from the remainder of the stomach and duodenum.
phase that increases on the delayed phase. Oral contrast should not be There is no statistical difference in outcomes between patients treated with
given because it will obscure contrast extravasation into the bowel lumen. empiric embolization versus embolization after angiographically demon-
CTA, by virtue of the cross-sectional imaging it provides, can also detect strated contrast extravasation. Empiric embolization should be avoided
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lesions that are not bleeding at the time of the study. CTA is emerging as in patients with prior radiation therapy or bowel surgery (eg, Whipple
the preferred first step in evaluation of patients with hemodynamically procedure) due to altered vascular anatomy and diminished or absent
significant acute lower GIB. The primary drawback of CTA is the neces- collateral circulation heightening risk of bowel ischemia. Compared with
sity of intravenous iodinated contrast, which may elicit a hypersensitivity the upper GI tract, the lower GI tract is theorized to be at increased risk
reaction or cause renal injury. This can be particularly concerning when of ischemia due to the absence of significant collateral pathways. While
considering the additional contrast required in a subsequent endovascular there is believed to be a rich intramural vascular network that offers
procedure (although typically, a positive CTA will guide subsequent ther- some protection against bowel ischemia, it is insufficient to allow for
apy and minimize the amount of contrast needed during angiography and routine empiric embolization. Thus, with regard to lower GIB, only active
embolization). CTA has a sensitivity of 90.9%, a specificity of 99%, and an bleeding that is visible on angiography is treated.
accuracy of 97.6% in localizing GI bleeding. In an animal model, CTA The overall technical and clinical success of embolization in upper
31
has been shown to detect bleeding rates as low as 0.3 mL/min—better than GIB is 93% and 67%, respectively. Technical success rates of lower GIB
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conventional angiography, but poorer than nuclear medicine studies. 32 embolization now approach 100% and 90%, respectively. The rate of
If the source of bleeding cannot be identified, angiography is typically recurrent hemorrhage after embolization has been reported between 0%
deferred. However, in cases of hemodynamic instability, preprocedural and 40%. 37,38 The higher rate of rebleeding in the upper GI tract com-
diagnostic imaging may be obviated in favor of direct angiographic pared with the lower GI tract may be attributed to refilling of injured
evaluation. In these circumstances, angiography is the most pragmatic vessels through the robust collateral circulation. Other factors associ-
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option because it allows for concomitant diagnosis and therapy in ated with clinical failure of arterial embolization include the use of anti-
patients who are critically ill. Angiography is even favored over surgery— coagulants, underlying coagulopathy, longer time interval between onset
particularly in high-risk surgical patients. It is minimally invasive and of bleed and embolization, increased number of RBC transfusions, hypo-
is associated with lower mortality. Additionally, outcomes between volemic shock and/or vasopressor use, and corticosteroids. 34,36,39,40 It is
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patients managed with arterial embolization and surgery are similar. 33,34 important to remember that embolization does not treat the underlying
Prior to angiography, the patient’s renal and coagulation status should pathology such as with peptic ulcer disease. In these patients, gastric acid
be assessed. Elevated PTT and PT/INR, as well as thrombocytopenia, suppression and treatment of helicobacter pylori are important adjuncts
should be corrected. In many patients, correcting an underlying coagu- to prevent recurrence of bleeding. Fortunately, even if bleeding recurs
lopathy may arrest bleeding. Embolization is unlikely to succeed in the after embolization, it is usually much less severe and the patient is less
setting of coagulopathy. Embolic agents cause vessel obstruction by pro- critical, thus allowing for surgical or endoscopic therapy. The incidence
viding a scaffold for thrombus formation rather than by pure mechanical of surgical intervention for patients with clinically unsuccessful arterial
occlusion. If necessary, blood products may be given intraprocedurally. embolization is 15% to 20%. In some instances, repeat embolization
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Target INR is <1.5 and target platelet count is >50,000/μL. can be performed in cases of recurrence. Although reembolization for
Once active hemorrhage is documented and localized with a diag- recurrent bleeding poses a theoretical increased risk of ischemic compli-
nostic radiology study, and the preprocedural labs have been optimized, cations, it does not appear to have a negative effect on clinical outcome.
the patient should be transferred immediately to the angiography suite. The overall postembolization complication rate is 6% to 9%.
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At our institution, we strive to perform angiography within 1 hour of Complications of embolotherapy include access site hematoma, nontar-
radiologic diagnosis of gastrointestinal bleeding. get embolization resulting in bowel necrosis, ischemic stricture, arterial
■ TECHNIQUE dissection, and contrast-induced renal failure. Even in technically suc-
cessful superselective embolization, there is a small risk of ischemia.
There are two basic endovascular treatment options: embolization and Findings of ischemia may include self-limited abdominal pain, elevated
vasopressor infusion. Both aim to decrease perfusion to the site of serum lactate, or asymptomatic discoloration or ulceration on endos-
vascular injury and thereby allow for clot formation and subsequent copy. Incidence of bowel infarction with current endovascular emboliza-
endogenous repair of the injured vessel. Embolization is the preferred tion techniques is reported to be 0% to 20%. 41
endovascular therapy for acute GIB.
Vasopressin: Once the treatment of choice for lower GI bleeding, vasopres-
Embolization: The right common femoral artery is accessed with a sin infusion is now only rarely used as a second-line therapy. Vasopressin
5-French vascular sheath. Then, using an angiographic catheter the mes- causes vasoconstriction of the smooth muscle of the splanchnic blood ves-
enteric vasculature in question is selected and angiography is performed. sels and the bowel wall. In this manner, it decreases perfusion to the site of
Celiac artery and SMA angiograms are performed for upper GI bleed- vascular injury to allow for clot formation. So, just as with embolotherapy,
ing; superior mesenteric artery (SMA), inferior mesenteric artery (IMA) procedural success is dependent on a normal coagulation cascade.
and internal iliac angiograms are performed for lower GI bleeding. The In terms of angiographic technique, vasopressin infusion is much less
primary angiographic findings of bleeding are visualization of active challenging than embolotherapy. After the right common femoral artery
contrast extravasation in the arterial phase and contrast pooling in the is accessed with a 5-French vascular sheath, the SMA or IMA is selected
venous phase. Once the site of bleeding is identified, the targeted vessel with an angiographic catheter. With the catheter tip seated just beyond the
is subselected, often with the use of a smaller microcatheter. The vessel ostium of the target vessel, vasopressin is infused at a rate of 0.2 U/min
is then embolized using any number of embolic agents. Coils are most for 20 minutes. Angiography is repeated to assess for persistent con-
commonly used. Modern endovascular coils are MRI compatible and do trast extravasation. If this rate is inadequate to stop bleeding, infusion is
not preclude subsequent MRI examinations. The fibers of the coil elicit increased to 0.3 or 0.4 U/min and another trial infusion is performed. Once
thrombosis while the coil itself functions as a scaffold for thrombus. an efficacious rate is found, it is continued for 12 hours. Subsequently, the
Many cases of gastrointestinal bleeding are intermittent in nature rate is reduced by half every 12 hours and concluded with a 12-hour saline
and thus produce negative angiography. As noted above, empiric or blind infusion. If clinical signs of active hemorrhage persist, follow-up angiogra-
embolization of the vessels supplying the area of concern can be performed phy may be performed. Otherwise, the catheter may be removed.
if no arterial abnormality is seen in upper GI bleeding. This technique is The waning use of vasopressin is attributable to improved microcath-
feasible in the upper GI tract due to its rich collateral circulation. The left eter technology and the preference for immediate angiographic result,
gastric artery is embolized if the site of bleeding has been localized to the both of which favor embolization. Nevertheless, this technique may

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