Question 17

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

Discussion

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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