Acute Abdominal Disease with Intestinal Obstruction

Pathophysiology of Acute Abdominal Disease with Intestinal Obstruction

• Acute abdominal disease with intestinal obstruction can occur in various portions of the bowel and has multiple causes, including adhesions, strictures, or tumors.
• Intestinal obstruction can be classified into three types: intraluminal (e.g., due to tumor, sequestration within a hernia, stricture), extraluminal (e.g., cholelithiasis, foreign body), or as part of a process directly involving the bowel tissue (e.g., ulcerative colitis, Crohn disease, ischemic pathology).
• Pain is the most common initial symptom associated with abdominal disease and is typically present in acute obstructive disease.
• Abdominal distention may progress dramatically, which strongly suggests the presence of a perforated intraabdominal viscus—a sign that is verified by radiographic findings showing evidence of free air within the abdominal cavity.

Causes of Acute Bowel Obstruction

• Adhesions that occur due to previous abdominal surgery
• Incarcerated or strangulated loops of the bowel that become trapped within hernias in the abdominal wall
• A prior history of abdominal surgery, particularly in the pelvic region, associated with a greater risk of developing intraabdominal adhesions
• Patients who are sedentary, debilitated, and taking chronic medications (e.g., phenothiazines) are at increased risk of developing hypotonic bowel

Physiological Consequences of Bowel Obstruction, Strangulation, and Perforation

• Hypovolemia from causes that include vomiting, diarrhea, extravascular fluid losses, and gastric suctioning
• Peritonitis and sepsis, which occur from the bacteria and enterotoxins that are released from the perforated bowel, further magnify fluid loss
• These processes can dramatically affect intravascular volume, electrolyte balance, and acid-base balance and result in sepsis
• Multisystem organ dysfunction syndrome is associated with increased mortality, which is initiated via the inflammatory response and may result in acute respiratory distress syndrome

Surgical Management

• Surgical resection of a diseased portion of the intestine is accomplished by creating a midline abdominal incision
• The fascia and the muscle layers are excised, and retractors are placed within the abdomen to improve visualization
• The peritoneal cavity is inspected
• After the diseased portion of the bowel is identified and resected, the distal and proximal ends of the bowel are excised
• An anastomosis is created by inserting a stapling device through a purse-string suture that is made at the distal portion

Anesthetic Management and Considerations

• Preoperative Period: Compare and contrast the clinical considerations associated with a large bowel and small bowel obstruction
• Large bowel obstruction typically has a longer prodromal period before acute signs and symptoms occur
• It may be associated with fewer acute metabolic derangements because its primary function is storage rather than secretion and absorption
• The large bowel is less likely to strangulate than the small bowel, but it can become markedly distended under certain conditions, such as toxic megacolon, which may lead to rupture

Physiologic Concerns Associated with Toxic Megacolon

• Occurs more frequently in patients who have ulcerative colitis
• This condition can occur in critically ill patients undergoing aggressive antibiotic therapy
• In this disease process, acute stasis of the large colon permits bacterial overgrowth, promoting a dramatic increase in intraluminal pressure
• The result is mucosal inflammation with loss of bowel wall integrity, which facilitates systemic absorption of bacterial endotoxins
• Clinical signs include abdominal distention, fever, tachycardia, pain, and the absence of bowel sounds
• Anemia, leukocytosis, hypokalemia, and hypoalbuminemia are typically present

Physiologic Manifestations Associated with Bowel Perforation

• Decreased blood flow, which causes tissue ischemia and a breakdown of the bowel wall resulting from increased intraluminal pressure
• Obstruction to blood flow along with impairment in bowel motility leads to sequestration and accumulation of fluid and gas proximal to the level of obstruction
• Absorption of intraluminal Fluid is impaired because of increased intraluminal pressure
• Release of bacteria, endotoxins, and intraluminal contaminants from within the bowel lumen into the peritoneum and into the systemic circulation results in sepsis

Signs and Symptoms Associated With Bowel Obstruction and Perforation

• Pain
• Abdominal distention
• Bloating
• Constipation
• Nausea and vomiting
• Fever
• Leukocytosis
• Hemodynamic variability
• Intraluminal gas and fluid within the lumen of segments proximal to the obstruction
• Free air present within the peritoneum (suggestive of bowel perforation)

Cardiovascular Abnormalities Associated with Bowel Obstruction

• Profound alterations in cardiovascular functioning and metabolic homeostasis are possible because of disruption in the integrity of the gastrointestinal tract
• The hemodynamic function is particularly susceptible to alterations in fluid, electrolyte, and acid-base balance that occur
• Cardiovascular function is affected by decreased preload resulting from an intravascular fluid volume deficit
• Compensatory sympathetic responses (tachycardia and vasoconstriction) attempt to restore adequate perfusion to tissues; however, there is a point where the compensatory mechanism will no longer support an adequate cardiovascular response and hypotension will occur

Abdominal Compartment Syndrome (ACS)

• Associated with increased intraabdominal pressure (IAP), which can cause end-organ dysfunction
• Increased IAP decreases cardiac output, glomerular filtration, and mesenteric and hepatic perfusion
• Decreased respiratory excursion and functional residual capacity can lead to increased peak airway pressures and hypoxia
• Because of pressure on the venous and arterial vasculature within the abdominal cavity, increases in intracranial pressure occur

Explore the various causes of acute abdominal disease with intestinal obstruction, including obstructions in different parts of the bowel caused by adhesions, strictures, or tumors. Learn about intraluminal, extraluminal, and tissue-related causes of intestinal obstruction.