Outline the risk factors and your management strategies for constipation in the critically ill.
- 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
- 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).
- 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
- Bulk forming laxatives
- Osmotic laxatives
- Contact laxatives
- 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:
- Soluble fibre
Tier two therapies and investigations: Assuming bowel obstruction and megacolon are ruled out
- Osmotic laxatives:
- Polyethylene glycol
- PR examination: this may have a therapeutic effect
- 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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