CONSTIPATION IN ICU 

1.  DEFINITION (No universal consensus)

Most ICU studies define constipation as:

• No bowel movement for ≥3 days
• OR need for rescue laxatives/enema
• OR hard stools / difficult evacuation

2.  EPIDEMIOLOGY

• Incidence: 15–83% (very common in ICU)
• Higher in:
• Mechanically ventilated patients
• Sedated/paralyzed patients
• Opioid use
• Enteral feeding patients

3.  WHY IT MATTERS

Constipation leads to:

A. Gastrointestinal effects

• Ileus
• Abdominal distension
• Increased intra-abdominal pressure (IAP)
• Feeding intolerance → ↑ aspiration risk

B. Respiratory effects

• Diaphragmatic splinting → difficult weaning
• ↑ ventilator days

C. Systemic effects

• Bacterial translocation → sepsis risk (theoretical)
• Delirium (gut-brain axis)

4.  PATHOPHYSIOLOGY (MULTIFACTORIAL)

A. Reduced gut motility

• Critical illness → autonomic dysfunction
• ↓ parasympathetic tone

B. Medications (most important cause)

• Opioids → μ-receptor mediated ↓ peristalsis
• Sedatives (propofol, benzodiazepines)
• Anticholinergics
• Vasopressors → ↓ splanchnic perfusion

C. Electrolyte imbalance

• Hypokalemia → ↓ smooth muscle contractility
• Hypercalcemia → constipation

D. Immobility

• Bed rest → ↓ colonic motility

E. Enteral feeding issues

• Low fiber feeds
• Inadequate hydration

5.  RISK FACTORS 

6.  DIAGNOSIS

A. History

• Last bowel movement
• Stool consistency
• Laxative use

B. Examination

• Abdominal distension
• Bowel sounds
• Rectal exam → fecal impaction

C. Monitoring tools

• Daily bowel chart (essential in ICU)

D. Investigations (if needed)

• X-ray abdomen → fecal loading / ileus
• CT abdomen → obstruction (if suspected)

7. DIFFERENTIAL DIAGNOSIS 

8.  MANAGEMENT 

FIRST RULE: RULE OUT SURGICAL CAUSES

Before treating “constipation,” exclude:

• Mechanical bowel obstruction
• Paralytic ileus
• Acute colonic pseudo-obstruction (Ogilvie)

 Clues:

• Severe distension
• Vomiting
• Absent bowel sounds
• Cecum >10–12 cm (X-ray)

 STEPWISE ICU MANAGEMENT ALGORITHM

 STEP 1: CORRECT REVERSIBLE CAUSES (MANDATORY)

A. Drug review (MOST IMPORTANT)

• Reduce/stop:
• Opioids (if possible)
• Anticholinergics
• Sedatives

 If opioids required → plan early PAMORA

B. Correct metabolic abnormalities

• Hypokalemia → target K⁺ >4 mEq/L
• Hypercalcemia → treat cause
• Hypomagnesemia

C. Optimize perfusion

• Avoid excessive vasopressors
• Ensure adequate splanchnic perfusion

D. Hydration

• Maintain euvolemia
• Avoid dehydration (especially in enteral feeds)

 STEP 2: NON-PHARMACOLOGICAL MANAGEMENT

A. Early enteral nutrition (VERY IMPORTANT)

• Stimulates gut motility via:
• Gastrocolic reflex
• Preferred over parenteral nutrition

B. Fiber

• Use only if no ileus
• Avoid in:
• Severe sepsis
• Gut hypoperfusion

C. Mobilization

• Even passive limb movement helps

D. Bowel charting

• Daily documentation:
• Stool frequency
• Consistency

4.  PHARMACOLOGICAL MANAGEMENT 

 A. OSMOTIC LAXATIVES (FIRST-LINE)

1. Polyethylene Glycol (PEG) 

• Dose:17–34 g/day via NG/PO
• Mechanism:Non-absorbable osmotic agent → ↑ water in stool

 Advantages:

• Predictable effect
• Less gas than lactulose
• Better tolerated in ICU

2. Lactulose

• Dose:15–30 mL PO/NG BD–TDS
• Mechanism:Fermented → osmotic effect + acidifies colon

 Disadvantages:

• Bloating
• Gas
• Electrolyte imbalance

 B. STIMULANT LAXATIVES (ADD-ON)

Used if osmotic laxatives inadequate

1. Bisacodyl

• Dose:5–10 mg PO
• 10 mg suppository
• Mechanism:Direct colonic stimulation

2. Senna-Dose:8.6–17.2 mg PO

 Combine with osmotic agents for synergy

 C. STOOL SOFTENERS

• Docusate sodium

 Limited ICU evidence → not preferred alone

 D. RECTAL THERAPY (ESCALATION)

Indications:

• No response to oral therapy
• Suspected distal stool retention

Options:

1. Glycerin suppository
2. Bisacodyl suppository
3. Phosphate enema
4. Tap water enema

Manual disimpaction

• For fecal impaction
• Requires lubrication + analgesia

 E. PROKINETIC AGENTS (IF ILEUS COMPONENT)

1. Metoclopramide

• Dose:10 mg IV TDS
• Action:Dopamine antagonist → ↑ gastric emptying

2. Erythromycin

• Dose:200 mg IV BD
• Mechanism:Motilin receptor agonist

 Useful in:

• Feed intolerance
• Gastroparesis

 F. OPIOID-INDUCED CONSTIPATION 

Pathophysiology:

• μ-receptor activation → ↓ peristalsis + ↑ absorption

Treatment: PAMORAs (Peripheral μ-opioid receptor antagonists)

1. Methylnaltrexone

• Dose:0.15 mg/kg SC (alternate days)
• Rapid onset (within hours)

2. Naloxegol-Oral option

3. Alvimopan-Mainly post-op ileus

• Do NOT reverse analgesia
• Use when laxative-refractory opioid constipation

REFERENCES

1. Irwin and Rippe’s Intensive Care Medicine