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CRITICAL CARE

Understanding peritonitis: Find out how to respond appropriately to this potentially fatal disorder.

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An acute or chronic disorder, peritonitis is an inflammation of the peritoneum, the serous membrane that lines the abdominal cavity and covers the visceral organs. Such inflammation may extend throughout the peritoneum or be localized as an abscess. Peritonitis commonly decreases intestinal motility and causes intestinal distension with gas. Without treatment, it can lead to fatal bowel obstruction, sepsis, or multiple organ dysfunction syndrome. Here's what you need to know to assess patients for peritonitis and intervene appropriately.

How peritonitis develops

The gastrointestinal (GI) tract normally contains bacteria, but the peritoneum is sterile. Inflammation and perforation of the GI tract from appendicitis, diverticulitis, or a peptic ulcer lets bacteria invade the peritoneum, causing peritonitis. Chemical inflammation also can cause peritonitis. Possible causes include perforation of a gastric ulcer with gastric acid release or bile release from a perforated gallbladder.

Whether the inflammation is bacterial or chemical, fluid containing protein and electrolytes accumulates in the peritoneal cavity and makes the usually transparent peritoneum opaque, red, inflamed, and edematous. Usually, the infection is localized as an abscess because the peritoneal cavity is so resistant to contamination. However, if the peritoneum is weakened or injured, inflammation and infection can spread through the peritoneal cavity. Peristaltic action decreases, leading to bowel obstruction. Large amounts of fluid from the intravascular space move into the peritoneal cavity, causing hypovolemia and hemoconcentration. The patient can develop shock, oliguria, and renal failure.

Recognizing trouble

In the early stage of peritonitis, the patient may feel vague, generalized abdominal pain. (If the infection is localized, he may describe pain over a specific area.) As peritonitis progresses, the patient's abdominal pain becomes increasingly severe and unremitting and usually increases with movement and respirations. Occasionally, pain may be referred to the shoulder or thoracic area. Other signs and symptoms include abdominal distension, anorexia, nausea, vomiting, and an inability to pass feces and flatus.

When you take the patient's vital signs, you may find fever, tachycardia, and hypotension. The patient will be acutely distressed and may lie still in bed with his knees flexed, breathing shallowly and moving as little as possible as he tries to relieve abdominal pain. If he's lost excessive fluid, electrolytes, and proteins into the abdominal cavity, you may note excessive sweating; cool, clammy skin; pallor; abdominal distension, and signs of dehydration (such as dry mucous membranes).

Early in peritonitis, you'll hear bowel sounds on auscultation, but these sounds tend to disappear as the inflammation progresses. You'll note abdominal rigidity on palpation and general tenderness (or local tenderness if the inflammation stays in a specific area). The patient also may have rebound tenderness.

Diagnostic testing includes a urinalysis, complete blood cell count, blood chemistry, abdominal and chest X-rays, abdominal and pelvic computed tomography (CT) scans, and paracentesis to obtain a peritoneal fluid sample for lab testing. If the patient has peritonitis, his white blood cell count is likely to reveal leukocytosis (more than 11,000/mm3), and his serum electrolyte levels may be abnormal, reflecting dehydration. Abdominal X-rays may show edematous and gaseous distension of the small and large bowel. Air will be visible in the abdominal cavity if an air-containing visceral organ such as the stomach has been perforated. The chest X-ray may show diaphragmatic elevation, and abdominal CT scan may reveal small fluid collections in areas of inflammation.

Peritoneal fluid analysis can help the health care provider identify peritoneal infection and pancreatic, biliary, or urinary leak.

How to intervene

Maintaining your patient's hemodynamic stability is key. Treatment also is aimed at combating infection, restoring intestinal motility, and replacing fluids and electrolytes.

In bacterial peritonitis, the type of antibiotic therapy administered depends on the infecting organism. Keep the patient N.P.O., administer supplemental parenteral fluids and electrolytes as prescribed, and administer medication to manage pain as ordered. Insert a nasogastric (NG) tube to decompress the bowel.

Surgery is an important intervention for all cases of peritoneal infection. The type of surgery depends on the cause of peritonitis; for example, an appendectomy may be performed if the peritonitis was caused by a ruptured appendix. Irrigation of the abdominal cavity with antibiotic solutions may be performed during surgery, although this practice is controversial.

Nursing considerations

Ensure that your patient has a patent airway and assess his respiratory status at least hourly, or more frequently if his condition warrants it (for example, if he has respiratory compromise due to shock). Note respiratory rate, rhythm, and depth and report dyspnea and accessory muscle use.

Auscultate the lungs bilaterally for adventitious or diminished breath sounds. Assess the patient's oxygen saturation continuously via pulse oximetry and monitor and report abnormalities in arterial blood gas analysis results.

Place the patient in a comfortable position that maximizes air exchange, such as semi-Fowler's to high Fowler's position. If his respiratory status deteriorates, assist with endotracheal intubation and mechanical ventilation.

Assess the patient's hemodynamic status, including blood pressure and heart rate, at least hourly, or more frequently if indicated. If he has a pulmonary artery catheter, monitor central venous pressure, pulmonary artery wedge pressure, cardiac output, and cardiac index.

Institute continuous cardiac monitoring and watch for arrhythmias caused by fluid volume deficits, hypoxemia, acid-base disturbances, or electrolyte imbalance. Be prepared to treat arrhythmias according to advanced cardiac life support guidelines.

Monitor the patient's temperature every 1 to 2 hours and administer antipyretics as ordered. Auscultate his abdomen for bowel sounds and assess for abdominal distension. If distension occurs, measure his abdominal girth daily to monitor changes. Keep him N.P.O. until his bowel function returns. Administer histamine2-receptor antagonists as ordered to reduce the risk of peptic ulcer formation.

As ordered, administer intravenous (I.V.) fluid and electrolyte replacement. If the patient exhibits signs and symptoms of hemorrhage, prepare to administer blood products such as packed red blood cells.

Give I.V. antibiotics as ordered and assess for ototoxicity and nephrotoxicity.

Closely monitor the patient's fluid intake and output, assessing urine output hourly. Notify the health care provider if urine output is less than 0.5 ml/kg/hour. Remember to include drainage from all sources in output calculations. Weigh the patient daily. If he has an NG tube, monitor tube drainage every 1 to 2 hours for color, amount, and other characteristics. Notify the health care provider if the drainage is bright red or looks like coffee grounds.

Monitor the patient's level of consciousness, noting such changes as increasing confusion, lethargy, or mental sluggishness, which may suggest hypoxemia.

Regularly assess his pain level, using a pain-intensity rating scale, and manage pain appropriately. Be alert for a sudden increase in pain severity (or a sudden decrease in severe pain), which may indicate perforation.

Provide emotional support to the patient and his family and teach them which signs and symptoms to report immediately, such as changes in pain characteristics, difficulty breathing, nausea or vomiting, or light-headedness. By understanding peritonitis and how to manage it, you can help your patient on the road to recovery.

Adapted and updated from Critical Care Challenges, Lippincott Williams & Wilkins, 2003.

© 2006 Lippincott Williams & Wilkins, Inc.