paralytic ileus

Pharmacologic Management of Post op paralytic ileus (P01):

• Minimizing the sympathetic inhibition of gastrointestinal motility, decreasing inflammation and stimulation of gastrointestinal 11-opioid receptors are the ultimate goals of pharmacologic management.

A) Minimizing sympathetic inhibition

• Both propranolol, a nonspecific 13-receptor antagonist, and dihydroergotamine, an a-receptor antagonist, have been investigated for treatment of POI.
• Neostigmine is an acetylcholinsterase inhibitor that causes an increase in cholinergic (parasympathetic) activity in the gut wall, which is believed to thereby stimulate colonic motility.
• Use of edrophonium chloride and bethanechol chloride, which competitively inhibit acetylcholine on the binding site of acetylcholinesterase, has been reported to show improvement of POI.
• Cisapride is a serotonin (5-HT)4 receptor antagonist that promotes acetylcholine release from postganglionic nerve endings in the myenteric plexus and is thought to indirectly improve gastrointestinal motility.
• Metocloprimide is suspected to enhance gastrointestinal motility without stimulating gastric secretion, but its use has not been substantiated for POI.

B) Decreasing inflammation

• Decreasing inflammation may be indicated in patients who are about to undergo major intestinal surgery, as this is thought to be an important contributing factor to POI.
• Nonsteroidal anti-inflammatory (NSAIDs) agents can be used in conjunction with opioid analgesics for their dual effects on pain control and inflammatory inhibition.

C) Stimulation of gastrointestinal iii-opioid receptors

• Stimulation of gastrointestinal .1-opioid receptors can theoretically influence gastrointestinal motility directly; therefore, blocking the peripheral gastrointestinal effects of centrally acting opioids used for analgesia may help prevent POI.
• Two novel drugs are being investigated for this reason: alvimopan and methylnaltrexone.
• Both drugs are If-opioid receptor antagonists, and both appear to offer promising results for preventing prolonged POI.
• Opioid therapy for postoperative or chronic pain is frequently associated with adverse effects, the most common being dose-limiting and debilitating bowel dysfunction, so alvimopan and methylnaltrexone may also be useful in the treatment of chronic opioid bowel dysfunction.
• The currently available opioid antagonists such as naloxone are of limited use because they also act at central opioid receptors to reverse analgesia and elicit opioid withdrawal.
• Alvimopan and methylnaltrexone are peripherally acting if-opioid receptor antagonists that have been studied in patients undergoing abdominal and pelvic surgery and have been shown in several studies to significantly accelerate gastrointestinal recovery. Alvimopan received FDA approval for the treatment of POI on May 20, 2008.

D) Alternative medications

• Bisacodyl administration versus placebo twice daily starting on postoperative day 1, patients who received bisacodyl had significantly earlier bowel movements than those who received placebo (25 h v. 56 h), but further studies are needed to assess the effect of laxatives on POI.

• Chemical, electrolyte, or mineral disturbances (such as decreased potassium levels)
• Complications of intra-abdominal surgery
• Decreased blood supply to the abdominal area (mesenteric artery ischemia)
• Injury to the abdominal blood supply
• Intra-abdominal infection
• Kidney or lung disease
• Use of certain medications, especially narcotics

Management:

Nil per os (NPO or “Nothing by Mouth”) is mandatory in all cases.

• Nasogastric suction and parenteral feeds may be required until passage is restored.
• There is no place for the routine use of peristaltic stimulants. Bowel movements may be stimulated by prescribing lactulose, erythromycin or, in severe cases (Ogilvie’s syndrome), neostigmine.
• If possible the underlying cause is corrected (e.g. replace electrolytes).
• In older children, paralytic ileus may be due to bacterial, viral, or food poisoning (gastroenteritis), which is sometimes associated with secondary peritonitis and appendicitis.

Causes of Paralytic ileus

• Postoperative – a degree of ileus usually occurs after any abdominal procedure and is self-limiting, with a variable duration of 24-72 hrs. Post op ileus may be prolonged in the presence of hypoproteinemia or metabolic abnromality.
• Paralytic ileus is a state in which there is failure of transmission of peristaltic waves secondary to neuromuscular failure.
• The resultant stasis leads to accumulation of fluid and gas within the bowel with associated distention, vomiting, absent or diminished bowel sounds and absolute constipation.
• Radiological picture shows dilated gas filled bowel loops with multiple air-fluid level.
• The picture is similar to mechanical small bowel obstruction; the only differentiating point is presence of gas in colon and rectum in paralytic ileus.
• Other clinical differentiating features of paralytic ileus from mechanical small bowel obstruction are.

1. Pain – Pain is colicky in mechanical obstruction. Pain is not a feature of paralytic ileus and if present is a steady, diffuse pain.
2. Bowel sounds – Bowel sounds are hypoactive or absent in paralytic ileus in contrast to hyperactive bowel sounds in mechanical obstruction.