Constipation in critically ill adults

Table 1 Key definitions of constipation reported in the intensive care unit

Ref.	Definition of constipation used in the study	Setting	Remarks
Drossman et al[10], 2016	≥ 2 of 6 symptoms for ≥ 3 months, symptom onset ≥ 6 months prior (Rome IV criteria)	General population	Not validated in ICU patients; relies on patient self-report and chronic symptom history, which limits applicability in critical illness
Gacouin et al[11], 2010	Absence of bowel movement for ≥ 6 days after ICU admission	Medical ICU	Utilizes a longer bowel movement interval threshold compared to most ICU studies
Guardiola et al[12], 2016	Paralysis of the lower gastrointestinal tract	ICU	Proposes an alternative term to constipation in an ICU setting
Lewis and Heaton[13], 1997	Types 1-2 (hard, lumpy) suggest constipation (Bristol Stool Form Scale)	General population	Widely used to assess stool consistency; may serve as a complementary tool for assessing constipation in ICU patients
Mostafa et al[14], 2003	Failure for the bowel to open for 3 consecutive days	Surgical/medical ICU	Definition applied within a broader investigation of gastrointestinal dysfunction in ICU patients
Nassar et al[15], 2009	Need for treatment with laxatives or enemas	ICU	Defined by the need for pharmacological intervention
Patanwala et al[16], 2006	Absence of bowel movement within the first 4 days of ICU admission	Medical ICU	Adopts a 96-hour interval instead of the 72-hour period typical for ambulatory patients, accounting for the first 24 hours dedicated to patient stabilization, which can delay initiation of enteral nutrition or bowel regimen
van der Spoel et al[17], 2006	First defecation occurring after 6 days	Mixed ICU	One of the earliest studies proposing an ICU-specific operational definition of constipation

ICU: Intensive care unit.

Table 2 Contributing factors to constipation in critically ill adults

Category	Contributing factors
Patient-related factors	Advanced age, prior abdominal surgery, immobility
Disease-related factors	Systemic	Acute kidney injury, sepsis, shock
	Metabolic	Diabetes mellitus, hyper/hypothyroidism, electrolyte imbalances
	Neurological	Spinal cord injury, stroke, Parkinson’s disease, multiple sclerosis, autonomic neuropathy
	Myopathies	Amyloidosis, scleroderma
	Psychological	Depression, anxiety, eating disorders
	Mechanical	Colorectal cancer, strictures, rectocele
Medication-related factors	Polypharmacy
	Opioids
	Sedatives
	Anticholinergics, including antidepressants and antipsychotics
	Antihypertensives, including calcium-channel blockers
	Diuretics
Nutrition-related factors	NPO status, delayed enteral feeding, inadequate fiber intake, dehydration

NPO: Nothing by mouth.

Table 3 Possible complications associated with constipation in the intensive care unit

Category	Possible complications
Respiratory	Reduced lung compliance
	Prolonged mechanical ventilation and ICU length of stay
	Risk of VAP
	Pulmonary aspiration
Infectious	Bacterial overgrowth and translocation
	Intestinal microbiota disruption (dysbiosis)
	Systemic inflammation triggered by endotoxins and bacterial translocation
	Nosocomial infection and sepsis
Gastrointestinal	Abdominal distension and discomfort
	Elevated intra-abdominal pressure
	Vomiting
	Delayed gastric emptying
	Poor tolerance of enteral nutrition
	Risk of intestinal pseudo-obstruction or perforation
Neurocognitive and psychological	Risk of delirium
	Psychological distress due to constipation-related pain or discomfort
	Reduced patient comfort and well-being

ICU: Intensive care unit; VAP: Ventilator-associated pneumonia.

Table 4 Enterally-administered laxatives used in management of constipation in the intensive care unit

Parameter	Osmotic laxatives		Stimulant laxatives	Stool softeners	Bulk-forming laxatives
	Saline	Non-saline
Examples	Milk of magnesia; magnesium citrate; sodium phosphate	Lactulose; macrogol/PEG	Senna; bisacodyl	Docusate	Psyllium; methylcellulose; polycarbophil
Mecha-nism of action	Increase intestinal osmotic pressure and water retention; promotes intestinal motility by stimulating cholecysto-kinin secretion	Poorly absorbed by the gut and act as hyperosmolar agents	Increase intestinal motility, water and electrolyte secretions; stimulates peristalsis	Act as a surfactant which emulsifies stool with fat and water	Increase stool bulk and frequency
Onset	0.5-6 hours (rapid)	Lactulose: 24-72 hours; PEG: 24-96 hours	6-12 hours	24-72 hours (slow)	12-72 hours (slow)
Clinical use	Rescue treatment for acute constipation. May cause electrolyte disturbances; caution in renal or cardiac dysfunction	Common use in ICU. Lactulose may result in shorter ICU length of stay; PEG may be more effective in opioid-induced constipation and has lower risk of acute intestinal pseudo-obstruction	Common use in ICU. Often combined with osmotic laxatives	Prophylactic use only. Often adjunctive, limited efficacy when used alone	Rarely used in ICU. Requires adequate hydration. Contraindicated in presence of bowel obstruction, ileus or megacolon

PEG: Poly-ethylene glycol; ICU: Intensive care unit.

Table 5 Suggested approach to management of constipation in the intensive care unit

Phase/criteria	Management
On admission (< 24 hours)	Patient history: Frequency of bowel movements, stool consistency, timing of last stool, baseline laxative use, history of bowel disorders
	Identify risk factors: Opiate use, immobility, neurological impairment, surgery, etc. Minimize risk factors where possible
	Preventive strategies	Correct fluid and electrolyte imbalances (potassium, calcium, magnesium)
		Ensure adequate hydration
		Initiate early enteral nutrition
	Consider initiating daily prophylactic laxatives in high-risk patients
> 24 hours since last defecation	Review and minimize constipating agents (e.g. opioids, anticholinergics)
	Perform abdominal and rectal examination
	Start first-line laxative therapy (e.g. lactulose, PEG, senna, bisacodyl); increase dose if already on therapy
	Reassess and adjust therapy daily
> 48 hours since last defecation (escalation phase)	Repeat rectal exam to assess impaction
	Consider	Abdominal X-ray to evaluate for ileus or obstruction
		Combination/adjunctive therapy
		Rectal interventions (e.g. enemas)
Refractory constipation	Consider advanced investigations and interventions	Abdominal CT to rule out mechanical obstruction
		Neostigmine (especially in suspected acute colonic pseudo-obstruction)
		Manual rectal dis-impaction if indicated
		Surgical decompression as last resort
Discontinuation criteria	Presence of diarrhea or resolution of symptoms
Contraindications to bowel management protocol	Renal disease
	Major abdominal surgery/bowel obstruction
	Neutropenia (or bone marrow transplant)
	Nausea and vomiting, undiagnosed abdominal pain
	Thrombocytopenia

CT: Computed tomography; PEG: Poly-ethylene glycol; ICU: Intensive care unit.