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Basics ⬇

Outline

BASICS

Definition!!navigator!!

Ileus is defined as intestinal obstruction that impairs aboral transit of ingesta, and includes both physical and mechanical obstructions. However, in the equine, it mostly refers to the functional inhibition of propulsive intestine activity, irrespective of its pathophysiology.

Pathophysiology!!navigator!!

  • Regulation of motility occurs as a complex interaction of central innervation, autonomic innervation, and the enteric nervous system. The enteric nervous system acts on the GI tract either directly through neurotransmitters or indirectly through intermediate cells, such as the interstitial cells of Cajal, cells of the immune system, or endocrine cells
  • Acetylcholine is the main excitatory neurotransmitter in the gut. Sympathetic stimulation (norepinephrine) inhibits acetylcholine release from the cholinergic fibers, resulting in inhibition of motility. Nonadrenergic–noncholinergic neurotransmitters like adenosine triphosphate, vasoactive intestinal peptide, substance P, nitric oxide, and others also play a role in regulating GI activity
  • Many reflexes are present that are essential to the proper functioning of intestinal motility, some of which occur locally within the enteric nervous system and are responsible for peristalsis and mixing contractions. Other reflexes travel to sympathetic ganglia, the spinal cord, or the brainstem to coordinate more complex activities, such as the gastrocolic reflex
  • Pain can cause a systemic release of norepinephrine, inhibiting acetylcholine release and decreasing intestinal motility. Ileus can develop from diseases directly involving the digestive system. Shock, electrolyte imbalances, hypoalbuminemia, peritonitis, endotoxemia, and distention, ischemia, or inflammation of the intestinal tract have all been implicated as contributing to the pathophysiology of ileus in the horse
  • POI occurs in around 20–25% of horses after laparotomy, affects small intestine most commonly, and is more frequent after small intestinal resection and anastomosis (42% of horses)

Systems Affected!!navigator!!

  • GI
  • Cardiovascular—hypovolemia and endotoxemia can result in depressed cardiovascular function

Signalment!!navigator!!

More common in Arabians and horses >10 years of age.

Signs!!navigator!!

Historical Findings

Depression, mild to moderate signs of colic, anorexia, and constipation. Ileus can occur secondary to many diseases (see Causes) that can be associated with specific historical findings.

Physical Examination Findings

  • Heart rate and respiratory rate are often elevated and mild to severe signs of colic are common. Clinical signs associated with dehydration are often present due to intestinal sequestration of fluids
  • Abdominal auscultation reveals an absence or reduction of borborygmi
  • On rectal palpation, distention of either the small or large intestine may be present
  • Build-up of fluid in the stomach occurs because of a lack of progressive motility. Decompression with a nasogastric tube not only prevents gastric rupture and provides pain relief, but it also allows for the volume of fluid to be quantified for IV replacement fluid therapy

Causes!!navigator!!

Ileus can be induced by virtually any intestinal insult, including intestinal distention or impaction, enteritis/colitis, abdominal surgery or peritonitis, vascular or obstructive intestinal injuries, endotoxemia, pain, shock, hypoproteinemia, or electrolyte imbalances.

Risk Factors!!navigator!!

Any factors predisposing the development of a previously mentioned cause of ileus. Colic cases with PCV >45%; elevated serum protein, albumin or glucose; electrolyte imbalances (hypokalemia or hypocalcemia); >8 L reflux at admission; prolonged anesthesia; prolonged surgery; high pulse rate; strangulating or ischemic lesion; resection and anastomosis. Certain drugs (α2-agonists or opioid analgesics) also inhibit intestinal motility.

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Functional ileus should be differentiated from obstructive diseases that require immediate surgical intervention. Persistent discomfort despite gastric decompression should alert for serious tissue injury or obstructive conditions.

CBC/Biochemistry/Urinalysis!!navigator!!

  • Increased PCV due to dehydration and/or splenic contraction. Azotemia may also be present
  • Hypoproteinemia in cases of colitis or enteritis. Hyperproteinemia if an inflammatory response is present
  • Leukopenia if associated with an acute inflammatory response. A longstanding inflammatory response can cause leukocytosis
  • Hypokalemia, hypocalcemia, hypomagnesemia, hypochloremia, and hyponatremia may be present due to sequestration of fluid in the intestines

Other Laboratory Tests!!navigator!!

Abdominocentesis

No detectable abnormalities except in cases of duodenitis/proximal jejunitis, peritonitis, or obstructive ileus, where the peritoneal fluid can be serosanguineous due to intestinal compromise and the cellular and protein levels are often high.

Imaging!!navigator!!

Ultrasonography

The intestine can be assessed for presence of movement, mural thickness, and dilation.

Treatment ⬆ ⬇

Outline

TREATMENT

Aims!!navigator!!

To decompress the GI tract, reduce inflammation and pain, stimulate motility, maintain hydration, and keep electrolytes balanced to both promote motility and maintain the GI barrier, as well as to prevent cardiovascular impairment.

Appropriate Health Care!!navigator!!

Inpatient intensive care management with 24 h monitoring.

Nursing Care!!navigator!!

  • Parenteral fluid therapy is vital due to the inability to absorb oral fluids. Fluid rates should equal fluid deficit + maintenance + ongoing loss
  • Maintenance fluid requirements are 50–60 mL/kg/day for adult horses, and 70–80 mL/kg/day for foals. Ongoing losses can be determined by quantifying volume of gastric reflux
  • Horses suffering from hypovolemic or endotoxemic shock may benefit from hypertonic saline administration to rapidly expand the vascular fluid volume. Hypertonic saline (5–7%) can be administered at a dose of 4 mL/kg as a rapid bolus, followed by isotonic fluids because the volume expansion by hypertonic fluids is short-lived (<30 min)
  • Horses with severe hyponatremia (<120 mmol/L) should not be given hypertonic saline due to the potential for demyelination reported to occur in humans. Serum sodium replacement should be closely monitored
  • Electrolyte imbalances should be addressed due to the negative effect of hypokalemia, hypomagnesemia, and hypocalcemia on motility. KCl may be added to parenteral fluids at a maximal rate of 0.5 mEq/kg/h due to the potential for cardiac effects
  • To correct hypocalcemia, 200–500 mL of 23% calcium borogluconate can be administered slowly (diluted in LRS)
  • To correct hypomagnesemia, 150 mg/kg per day of MgSO4 (0.3 mL/kg of a 50% solution) is administered diluted in LRS
  • Horses with hypoproteinemia (<35–40 g/L) require administration of plasma or colloids to increase oncotic pressure
  • Gastric decompression via a nasogastric tube should be performed to relieve discomfort and to prevent gastric rupture

Activity!!navigator!!

Frequent hand-walking (4–6 times daily) may help stimulate the GI tract.

Diet!!navigator!!

Feed and water should be withheld.

Client Education!!navigator!!

If ileus persists or the horse deteriorates clinically, surgery is indicated owing to the potential for an obstructive/ischemic lesion.

Surgical Considerations!!navigator!!

See Client Education.

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Analgesics

  • Pain relief is important when correcting ileus. NSAIDs are a good choice as they do not inhibit motility. If additional analgesia is needed, then α2-agonists can be given alone or in conjunction with butorphanol (opioid). These drugs should be used judiciously as they can inhibit motility temporarily and mask signs of serious intestinal injury
  • NSAIDs—flunixin meglumine 0.5–1.1 mg/kg IV every 8–12 h

Prokinetic Agents

  • Bethanechol chloride—0.025 mg/kg IV or SC every 6 h. Side effects—salivation, abdominal cramps, diarrhea
  • Cisapride—recommended dose 0.1 mg/kg IM every 8 h. Side effects in people are cardiotoxicity. Related drugs like tegaserod or mosapride appear to be effective in horses as well
  • Erythromycin lactobionate—its efficacy is questionable in the presence of inflammation of the intestine. Recommended dose 0.5 mg/kg IV every 6 h. Side effect—diarrhea
  • Metoclopramide—recommended dose 0.04 mg/kg/h IV in saline as a CRI. Side effects—excitement, restlessness, sweating, abdominal cramps
  • Lidocaine—suppresses sympathetic neurotransmission, has anti-inflammatory and analgesic properties, and ameliorates the negative effects of flunixin meglumine on injured intestinal mucosa. It is widely used as a prokinetic drug although its efficacy in horses has been under question. Recommended dose 1.3 mg/kg IV as a slow bolus, followed by 0.05 mg/kg/min IV in saline or LRS as a CRI over ≥24 h. Side effects—muscle fasciculations, trembling ataxia

Contraindications!!navigator!!

Oral drug administration is contraindicated in horses with ileus of the small intestine.

Precautions!!navigator!!

N/A

Possible Interactions!!navigator!!

N/A

Alternative Drugs!!navigator!!

Acupuncture may be successful in promoting motility in horses.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

The patient should be monitored closely to ensure that IV fluid therapy is appropriate and that decompression of gastric and small intestinal distention is adequate.

Prevention/Avoidance!!navigator!!

N/A

Possible Complications!!navigator!!

  • Circulatory shock
  • GI rupture

Expected Course and Prognosis!!navigator!!

Survival of horses with POI has been reported to be around 60%.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Age-Related Factors!!navigator!!

N/A

Zoonotic Potential!!navigator!!

N/A

Abbreviations!!navigator!!

  • CRI = constant rate infusion
  • GI = gastrointestinal
  • LRS = lactated Ringer's solution
  • NSAID = nonsteroidal anti-inflammatory drug
  • PCV = packed cell volume
  • POI = postoperative ileus

Suggested Reading ⬆ ⬇

Hardy J, Rakestraw PC. Postoperative care, complications and reoperation. In: Auer JA, Stick , JA, eds. Equine Surgery, 4e. St. Louis, MO: WB Saunders, 2012:499–506.

Lefebvre D, Hudson NPH, Elce YA, et al. Clinical features and management of equine post operative ileus (POI): survey of diplomates of the American Colleges of Veterinary Internal Medicine (ACVIM), Veterinary Surgeons (ACVS) and Veterinary Emergency and Critical Care (ACVECC). Equine Vet J 2016;48:714–719.

Lefebvre D, Pirie RS, Handel IG, et al. Clinical features and management of equine post operative ileus: survey of diplomates of the European Colleges of Equine Internal Medicine (ECEIM) and Veterinary Surgeons (ECVS). Equine Vet J 2016;48:182–187.

Salem SE, Proudman CJ, Archer DC. Has intravenous lidocaine improved the outcome in horses following surgical management of small intestinal lesions in a UK hospital population? BMC Vet Res 2016;12:157.

Sanchez LC, Lester GD. Gastrointestinal ileus. In: Smith B, ed. Large Animal Internal Medicine, 5e. St. Louis, MO: Elsevier Mosby, 2015:728–731.

Author(s) ⬆

Author: Luis M. Rubio-Martinez

Consulting Editors: Henry Stämpfli and Olimpo Oliver-Espinosa