Question 17

Outline the risk factors and your management strategies for constipation in the critically ill.

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College Answer

Risk factors

  • Constipation usually results from multiple interacting causative factors:
  • Decreased gastrointestinal motility secondary to:  sepsis, 
  • electrolyte abnormalities  drugs e.g. opiates
  • spinal injury
  • neuromuscular conditions such as Parkinsons long-term laxative abuse
  • Immobility due to illness, injury or sedation. Bed rest or a period of immobility is thought to result in a weakening of the abdominal wall muscles leading to difficulty in raising the intraabdominal pressure sufficiently for defecation to occur.
  • Stool quality, which may be affected by lack of fluid and fibre
  • Lack of access to appropriate toilet facilities and lack of privacy
  • Unconscious patients may not feel the need to defecate and cannot express this need
  • Using a bedpan increases the likelihood of constipation. Intra-abdominal pressure needs to be raised for successful defecation and this is impaired while lying on a bedpan. 
  • Increased incidence in the elderly and nursing home residents

Management Strategies

  • May benefit from routine Bowel Management Protocol. 
  • Routine laxatives for all, upgraded to stronger agents/enemas if no bowel action after 2 days.
  • AXR if no successful bowel movements after 3-4 days.
  • Consider surgical/mechanical cause for constipation and rule out with surgical review / AXR / CT.
  • Consideration of neostigmine infusion if pseudo obstruction (rule out mechanical obstruction first – CT abdomen transition point).

Non-pharmacological Interventions:

  • Sedation breaks to allow assessment of need
  • Stop medications that cause constipation
  • Normal enteral diet (high fibre feed)
  • Availability of commodes/toilets near to patient area for ambulant patients
  • Minimisation of opiate analgesia as able (consideration of Targin)
  • Mobilisation / free patient from unnecessary lines/tubes etc.
  • Adequate oral hydration
  • Normalise electrolytes

Pharmacological Interventions:

  • Bulk forming laxatives
  • Osmotic laxatives
  • Enemas
  • Contact laxatives
  • Prokinetics
  • Neostigmine for pseudo-obstruction


Risk factors for constipation in the critically ill:

Modifiable ICU-related risk factors

  • Delayed enteral nutrition (delayed for longer than 24 hrs) - although early enteral nutrition has also been blamed, and in fact in ICU patients nasogastric nutritional formula is at least as likely to cause constipation as diarrhoea ( Montejo et al, 1999).
  • Reduced mobility
  • Deep sedation
  • Heavy opiate use
  • Anticholinergic drug side effects
  • Calcium channel blockers
  • The use of paralysing infusions
  • Electrolyte disturbance, eg.hypokalemia hypercalcemia and hypomagnesemia
  • Dehydration, inadequate fluid resuscitation (or excess diuresis)
  • Hypotension (SBP under 90mmHg - Gacouin et al, 2010)
  • Hypoxia (P/F ratio under 150 - also Gacouin et al)

Non-modifiable disease risk factors

  • Abdominal surgery
  • Severe illness
  • Paralysis (eg. spinal cord injury) 
  • Prior alcohol or cannabis use

Management strategies for constipation in the critically ill

Tier one therapies and investigations:

  • Abdominal X-ray to exclude "true" bowel obstruction"
  • Electrolytes and biochemistry to rule out and correct any electrolyte disturbance
  • Fluid management review to ensure euvolaemia and adequate hydration
  • Attention to primary pathology (eg. shock, hypoxic respiratory failure) - if this is being treated well and is getting better, patience may be all that is required.
  • Drug chart audit to ensure exposure to opiates, anticholinergics and calcium channel blockers is minimised
  • Mobility: physiotherapy for limbs, sit out of bed in a chair, etc
  • Stool softeners, stimulants and bulk-forming laxatives:
    • Docusate
    • Sennocot
    • Soluble fibre

Tier two therapies and investigations: Assuming bowel obstruction and megacolon are ruled out

  • Osmotic laxatives:
    • Lactulose
    • Polyethylene glycol
  • PR examination:  this may have a therapeutic effect
  • Enema
  • Prokinetics, eg. erythromycin
  • Opiate antagonists, eg. methylnaltrexone

Tier three therapies and investigations: assuming all of the above are ineffective, or mpossible to implement

  • Abdominal CT  to investigate for possible abdominal pathology unseen on AXR
  • Neostigmine infusion
  • Manual disimpaction
  • Surgical decompression


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