Bowel Obstruction Supportive Care in Pediatric Oncology irantextbook.ir 93df

baseline white blood count with evidence of hemoconcentration as well as hypochloremic met- abolic alkalosis. Imaging studies begin with supine, upright and decubitus abdominal radio- graphs. Although not pathognomonic, air- fl uid levels in dilated bowel loops and pneumatosis intestinalis on KUB are strongly supportive of obstruction. Dilated and contracted bowel loops may be appreciated proximal and distal to the obstruction, respectively. Abdominal CT with oral contrast will best localize the obstruction and identify the etiology Silliman et al. 1994 ; Yip and Goddard 2010 . Patients with neutropenia or necrotic bowel are at high risk of infection and perforation of the thinned intestinal mucosa and should not undergo small bowel follow-through exam using barium. Management of obstruction includes bowel rest, decompression via nasogastric tube, and intrave- nous fl uids to resolve electrolyte derangements and treat dehydration. Additional supportive care mea- sures include antiemetics, anticholinergics and analgesics. As bowel cleansing preparations are contraindicated in gastrointestinal obstruction, ene- mas and suppositories are suggested to resolve fecal impaction and can be used with caution in immunocompromised patients Arul and Spicer 2008 ; Yip and Goddard 2010 . Indications for sur- gical intervention include: 1 persistent bleeding in the absence of neutropenia, thrombocytopenia or coagulopathy; 2 intraperitoneal perforation; 3 clinical deterioration of unknown etiology, espe- cially if requiring blood pressure support with either colloids or vasopressors; and 4 any abdom- inal process that would require surgery in an immu- nocompetent host such as a mass lesion Silliman et al. 1994 . In contrast to non-oncologic episodes of intussusception, children with intussusception caused by tumor require surgical reduction rather than air- contrast or barium enema Fisher and Rheingold 2011 .

7.6 Tumor Rupture and Organ

Perforation Tumor rupture and organ perforation are surgical emergencies. Etiologies include the malignancy itself, treatment sequelae, iatrogenic intervention and unresolved obstruction. The most common cause of GI perforation is iatrogenic intervention, specifi cally endoscopy Gagneja and Sinicrope 2002 . Tumors at risk for spontaneous rupture include Wilms tumor, hepatoblastoma, neuro- blastoma and B-cell lymphoma Arul and Spicer 2008 . Tumor rupture in patients with Burkitt lymphoma may occur at presentation, during sur- gical intervention or steroid therapy, or with tumor necrosis Fisher and Rheingold 2011 . If lymphoma erodes the intestinal wall, it can cause GI perforation at the site of transmural invasion. Tumor rupture and organ perforation are not lim- ited to solid tumors or bowel; leukemic patients with splenomegaly have a small risk for splenic rupture, either spontaneously or with trivial trauma Gagneja and Sinicrope 2002 . In addi- tion, therapy with prolonged corticosteroids, bev- acizumab or radiation disrupts the GI mucosal epithelium. As previously mentioned, bevaci- zumab potentially increases the risk of gastric perforation Demshar et al. 2011 . Sequelae like peptic ulcer disease and adhesions, acting as lead points for mesenteric twisting, represent condi- tions that further weaken the intestinal wall. Frequent endoscopic procedures, unresolved obstruction or infection, or medically refractory conditions such as gastritis and ulcers predispose to perforation Yip and Goddard 2010 ; Fisher and Rheingold 2011 . Although shock and peritoneal signs strongly suggest perforation, presentation varies consider- ably in immunocompromised pediatric oncology patients. Exam may reveal the classic acute abdo- men with the patient rigid in a fl exed position and exhibiting rebound tenderness or, in contrast, dis- play only mild evidence of discomfort, tender- ness, or distension. Intestinal distension usually results from the patient swallowing excessive amounts of air or from excessive gas production from bacterial overgrowth. Cecal diameters 13 cm dramatically increase the risk of perfora- tion. Occasionally subcutaneous emphysema may be appreciated. Bowel sounds range from absent to hyperactive. Gastric perforation com- monly presents with acute onset of severe abdom- inal pain that is often associated with nausea and vomiting, including hematemesis. Patients may complain of shoulder pain, which is referred pain from an irritated diaphragm Gagneja and Sinicrope 2002 ; Yip and Goddard 2010 . Laboratory workup may reveal relative leuko- cytosis, neutrophilia, and anemia due to peritonitis and hemorrhage as well as electrolyte imbalances that need correction prior to surgery Gagneja and Sinicrope 2002 . Initial imaging consists of an upright KUB to evaluate for air under the dia- phragm that may extend into the liver, enabling visualization of the hepatic ligament, and decubi- tus KUB to evaluate for air along the fl ank. Another clue to the presence of perforation is visualization of both sides of the bowel wall. In the setting of an indeterminate KUB, CT scan should be utilized Gagneja and Sinicrope 2002 . Surgical consultation is paramount with suspi- cion of tumor rupture or organ perforation. Pending surgical intervention, immediate man- agement includes making the patient NPO with nasogastric tube placement with suction to evac- uate the stomach and protect the airway. In addi- tion, urinary catheterization and analgesics may be necessary to monitor fl uid status and control pain, respectively. Given the risk of infection, adequate coverage for Gram- negative enteric and anaerobic organisms should be implemented similar to treatment for neutropenic enterocolitis. Laparoscopy should be utilized when possible, with surgery consisting of bowel resection of the affected area followed by reanastomosis. Patients with excessive tumor burden, such as those with disseminated Burkitt lymphoma, require reduc- tion by chemotherapy prior to surgical interven- tion Gagneja and Sinicrope 2002 ; Fisher and Rheingold 2011 .

7.7 Abdominal Compartment

Syndrome Although mostly seen in adult patients who have sustained trauma, abdominal compartment syndrome ACS may occur in pediatric patients, including those with large tumor masses at pre- sentation or as a postoperative complication Fisher and Rheingold 2011 ; Terpe et al. 2012 . The mechanism of ACS appears to be ischemia- reperfusion injury with associated bowel isch- emia or necrosis Beck et al. 2001 . Two large prospective studies report the incidence of ACS among children admitted to the intensive care unit to be 1 , irrespective of an oncologic diagnosis and with high risk of mortality Cheatham et al. 2007 . Increased intra- abdominal pressure IAP leads to multiorgan compromise by initially impairing respiratory mecha nics which alter cardiac output leading to organ hypoperfusion and subsequent renal and cerebral insuffi ciency De Backer 1999 . Although no defi nitive ACS diagnostic crite- ria exist for the pediatric population, children are thought to require an IAP of ≥20 mmHg with associated organ compromise Beck et al. 2001 ; Cheatham et al. 2007 ; Fisher and Rheingold 2011 . Patients with ACS will present with a tense and distended abdomen with associated hypotension, oliguria or anuria and respiratory compromise Beck et al. 2011 . The aims of ACS management are to: 1 improve abdominal wall compliance with positioning and medications; 2 decrease intraluminal content with nasogas- tric suction; 3 decrease extraluminal content with percutaneous catheter decompression of intraperitoneal air or fl uid; and 4 optimize fl uid balance to reduce end-organ hypoperfusion with- out worsening IAH. Elevating the head of the bed increases IAP and should be avoided; similarly, sedatives and analgesics will increase abdominal muscle tone and should be minimized, as possi- ble. Studies in adults with ACS are investigating neuromuscular blockade as a means to decrease IAP. Careful aggressive fl uid resuscitation with hypertonic crystalloids and colloids should be attempted although refractory IAH or end-organ damage requires immediate surgical decompres- sion Cheatham et al. 2007 .

7.8 Summary

Prompt identifi cation of abdominal emergencies in pediatric oncology patients can be a chal- lenge due to decreased signs and symptoms of infl ammation in the immunocompromised host. Successful outcomes require vigilance for atypi- cal presentations in immunocompromised chil-