Page 1481 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

1020 PART 9: Gastrointestinal Disorders

similar to esophageal variceal band ligation can be used to treat bleeding crucial to avoid extensive surgical resection and to ensure that the bleed-
internal hemorrhoids. 101 ing is truly arising from the LGI tract.
■ RADIONUCLIDE STUDIES Preoperative Localization: The role of angiography and colonoscopy in
identifying the bleeding site was outlined previously. In addition to angi-
In the event of a negative colonoscopy, a radionuclide scan using ography and colonoscopy, exploratory laparotomy with intraoperative
99m Tc-pertechnetate-labeled red blood cells is used frequently to local- endoscopy can be used to localize the bleeding source, especially in the
ize the LGI bleeding site prior to subsequent angiographic evaluation. small intestine. Intraoperative endoscopy can be performed with oral,
The nuclear scan offers the ability to detect rates of bleeding as low as rectal, or enterotomy introduction of the endoscope. Following incision
0.1 mL/min, and the 48-hour stability of the tagged red blood cells of the abdominal wall and exposure of small bowel, the endoscope can
allows repeated imaging during this time period. However, the high sen- be introduced orally. The endoscope, generally a pediatric colonoscope,
sitivity of radionuclide imaging is offset by its low specificity compared can be advanced easily to the ligament of Treitz. Subsequently, the
with a positive endoscopic or angiographic examination. A positive entire small bowel is examined by pleating the small bowel over the
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radionuclide study localizes the bleeding only to an area of the abdomen colonoscope. The endoscopist must limit the amount of air insufflation
and cannot define precisely the mucosal location of the bleeding site. because excessive distention of the bowel will result in prolonged post-
Therefore, a positive scan should be used to direct attention to specific operative ileus. Following inspection of the small bowel to the ileocecal
sites of the GI tract that can be examined subsequently by angiography valve, a second inspection is performed as the colonoscope is withdrawn
or a repeat endoscopy. Furthermore, surgical intervention should not be slowly. The surgeon assists the examination by carefully inspecting the
based on the results of a radionuclide scan alone but should be guided serosal side of the bowel for abnormalities, such as a transilluminated
by accurate angiographic or endoscopic evaluation. angiodysplastic lesion. Alternatively, a sterilized colonoscope may be
■ ANGIOGRAPHIC THERAPY placed through an enterotomy site in the small bowel and then can be
passed proximally and distally into the small bowel to facilitate exami-
Angiography with therapeutic intent is the appropriate treatment nation. This approach carries a risk of contamination of the exposed
modality in the setting of massive bleeding that precludes colonoscopy peritoneum. A collaborative effort between the endoscopist and the
or after a nondiagnostic colonoscopy. The overall diagnostic yield of surgeon is essential for the efficient and safe performance of intraopera-
angiography ranges from 40% to 78%, with diverticular disease and tive endoscopy.
angiodysplasia being the most common findings. In a stable patient, Once the source of bleeding is localized, a segmental colectomy
a radionuclide scan is performed often for initial localization prior to involving the bleeding lesion can be performed. In a patient with
angiographic evaluation because the nuclear scan is a more sensitive extensive diverticular disease and a localized diverticular bleeding site,
examination and detects slower rates of bleeding. Patients who develop a segmental resection eradicating the bleeding site is adequate with-
106
an immediate blush on 99mTc-labeled red blood cell scintigraphy are out the need to resect segments involving nonbleeding diverticula.
likely to have a positive angiography. In the absence of localization via With respect to angiodysplasia, the presence of cecal angiodysplasia
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nuclear imaging, the superior mesenteric artery (SMA) is examined first should alert the surgeon to the possibility of angiodysplasia in the distal
because most diverticular and angiodysplastic bleeds occur in bowel terminal ileum. It should be noted that angiography that demonstrates
supplied by this artery. If the evaluation of the SMA is negative, the cecal angiodysplasia may fail to identify a similar small bowel lesion,
104
inferior mesenteric and celiac vessels are studied. and therefore, intraoperative small bowel endoscopy should be used.
The intermittent nature of LGI bleeding in many cases presents a In addition, when a right hemicolectomy for suspected angiodysplasia
problem for angiographic evaluation and treatment because active is undertaken, resection of the distal 30 to 60 cm of the terminal ileum
bleeding at the time of dye injection is required for a positive examina- should be considered.
tion. Transfusion requirements of >5 units of packed red cells within a A subtotal colectomy is indicated for exsanguinating hemorrhage
24-hour period have been shown to predict a positive angiography. or persistent hemorrhage without an identifiable site of bleeding, and
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Initial angiographic hemostasis using intra-arterial vasopressin or involves colonic resection from the cecum to proximal rectum with an
embolization ranges from 60% to 100%, although recurrent bleeding ileoproctostomy. This procedure is associated with a high morbidity
108
may be as high as 50%, especially following vasopressin therapy. and mortality, but rebleeding rates are extremely low. Blind segmental
106
Intraarterial vasoconstrictive therapy with vasopressin is used predomi- resection is contraindicated because this procedure is associated with
108
nantly in diverticular bleeding and angiodysplasia and is associated with excessive rates of rebleeding, morbidity, and mortality.
a major complication rate of 10% to 20%, including arrhythmias, isch-
emia, and pulmonary edema. Transcatheter embolization therapy with OBSCURE BLEEDING AND SMALL BOWEL EVALUATION
various agents, including gelatin sponge and microcoils, may be a more Occasionally, a patient presenting with acute gastrointestinal bleeding
definitive means of controlling hemorrhage but is associated with a risk undergoes a nondiagnostic evaluation with endoscopy, radionuclide
of intestinal infarction as high as 20%. Attempts to reduce this risk have imaging, and angiography but clinically stabilizes owing to intermittent
included the application of a highly selective catheterization technique or permanent cessation of bleeding. In such a situation, emergent surgical
and the use of a relatively distal site for embolization with temporary exploration and intraoperative endoscopy may not be indicated. Instead,
occluding agents. 107 further diagnostic evaluation should be directed specifically at the small
In the event that therapeutic angiography does not achieve permanent bowel, which is the likely source of obscure bleeding in many cases, with
hemostasis, emergent surgical therapy is indicated. However, initial angi- angiodysplasia being the most common lesion. Advances in endoscopic
ographic therapy in the actively bleeding patient may achieve temporary technology have enabled the gastroenterologist to visualize more distal
hemostasis and hemodynamic stability and thereby allow surgical inter- portions of the small bowel compared with traditional upper endoscopy.
vention in a controlled setting with an improved operative mortality. 106 These novel endoscopic modalities will be reviewed and will be followed
■
by a discussion of specific lesions associated with obscure bleeding.
■
In the patient presenting with exsanguinating LGI hemorrhage, colo- NOVEL ENDOSCOPIC MODALITIES
SURGICAL THERAPY
noscopy and angiography should be deferred, and an emergent subtotal Push Enteroscopy (PE): An orally inserted adult/pediatric colonoscope
colectomy should be performed. In all other cases, surgical therapy or special enteroscope is passed with or without an overtube as far as
should be reserved for hemorrhage that is refractory to nonsurgical possible beyond the ligament of Treitz and allows visualization of the
interventions. Furthermore, preoperative localization of bleeding is proximal 60 cm of jejunum. The diagnostic yield of this procedure is as

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