9. Postoperative Ileus

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9. Postoperative Ileus

  1. 1. Postoperative Ileus
  2. 2. Pathophysiology NEUROGENIC PHARMACOLOGIC HORMONAL INFLAMMATORY ILEUS
  3. 3. Pathophysiology: neurogenic + hormonal • Catecholamines: – Raised in postoperative period – Alpha + beta blockers in animals improved GI motility, not in humans – Rats with no adrenal medulla had no shorter postoperative ileus
  4. 4. Pathophysiology: neurogenic + hormonal • Sympathetic overactivity: – Afferent inhibitory neural reflexes: skin + intestine incisions – Efferent inhibitory neural reflexes: inhibits release of ACh by ENS – Animal studies: blocking sympathetic reflexes leads to shorter ileus
  5. 5. Pathophysiology: neurogenic + hormonal • Corticotropin-releasing factor: – Released in response to stress – Mice with no CRF receptors do not develop gastric ileus • Nitric oxide: – Main inhibitory neurotransmitter in ENS – Role in ileus in animal studies, unknown role in humans
  6. 6. Pathophysiology: Inflammatory • Macrophages: – Dominant leucocyte in muscular layers – Activated by manipulation of intestines, release proinflammatory cytokines (including NO) – Prostaglandins directly inhibit intestinal smooth muscle contraction; blocking COX-2 increases muscular contractility – Selective manipulation of jejunum in rats leads to pan-intestinal hypomotility, ? upregulation of inflammatory cascade throughout GIT • Mast cells: – mast cell stabilisers limit inflammation
  7. 7. Pathophysiology: Pharmacologic • Opioids – Inhibitory effect: presynaptic blockage of excitatory neurones innervating intestinal smooth muscle ∀ µ, δ, κ (predominately µ2 causing bowel dysfunction) – Naloxone (non-selective µ blocker) improves motility – ? Future selective µ2 blocker
  8. 8. Pathophysiology: Pharmacologic • Anaesthesia – Short half-life – No evidence of prolonged bowel dysfunction • Fluids + electrolytes – Conflicting results
  9. 9. Prevention • Laparoscopic surgery: – Reduces length of postoperative ileus – ? Mechanism: • Reduced inflammatory response • Less pain, less analgesia • Less aggressive use of NGTs • Alvimopan: peripheral µ blocker – Administered before opioids – Dose dependent
  10. 10. Treatment • Nasogastric decompression – Routine use unnecessary – Slower return of normal bowel function • Early ambulation – No benefit to bowel function – Encouraged to prevent other complications
  11. 11. Treatment • Early enteral feeding – Malnutrition has detrimental effects on healing – Enteral nutrition has far fewer complications than TPN: • Mucosal atrophy • Increased permeability • Increased septic complications – Benefit to ileus: uncertain – Encouraged to enhance wound + anastomotic healing
  12. 12. Treatment: Pharmacological • NSAIDs: – Pain relief + anti-inflammatory – Risk of surgical site + GI bleeding • Avoidance of opioids • Epidural analgesia: – Clear benefit – Inhibits reflex arcs • Stimulant laxatives may help • Neostigmine: adverse effects limit use
  13. 13. • Multiple causes • Multiple prevention strategies and treatments available, no single treatment completely effective

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