How should constipation be managed in a critically ill patient in the Intensive Care Unit (ICU)?

Management of Constipation in Critically Ill ICU Patients

Constipation in critically ill ICU patients should be managed with a stepwise protocol beginning with early enteral nutrition when feasible, followed by stimulant laxatives (senna or bisacodyl) as first-line pharmacologic therapy, with escalation to osmotic agents and suppositories for refractory cases, while ruling out mechanical obstruction and fecal impaction before treatment initiation. 1, 2

Initial Assessment and Risk Factor Identification

Before initiating treatment, perform a focused evaluation to identify reversible causes and contraindications:

• Rule out fecal impaction first, especially if overflow diarrhea is present, as this represents a medical emergency requiring manual disimpaction rather than laxatives 1, 2
• Exclude mechanical bowel obstruction through physical examination and abdominal imaging if clinically indicated 1, 2
• Evaluate for metabolic causes including hypercalcemia, hypokalemia, hypothyroidism, and diabetes mellitus 1, 2
• Review and discontinue non-essential constipating medications when possible 1, 2
• Recognize that constipation occurs in approximately 70% of critically ill patients, making it nearly universal in this population 3

Prevention Through Early Enteral Nutrition

Early enteral nutrition (within 24-48 hours of ICU admission) is the single most important preventive measure for constipation in critically ill patients and should be initiated whenever the gastrointestinal tract is functional. 1, 3

• Early EN reduces infectious complications compared to parenteral nutrition (RR 0.50,95% CI 0.37-0.67) and is associated with significantly less constipation 1, 3
• EN should be started at low rates and progressively increased within 48 hours to avoid overfeeding complications 1
• Contraindications to EN include uncontrolled shock, uncontrolled hypoxemia and acidosis, uncontrolled upper GI bleeding, gastric aspirate >500 mL/6 hours, bowel ischemia, bowel obstruction, and abdominal compartment syndrome 1
• Target 20-25 kcal/kg/day during the acute phase, increasing to 25-30 kcal/kg/day during recovery 1

Pharmacologic Management Algorithm

First-Line: Stimulant Laxatives

Initiate bisacodyl 10-15 mg orally once to three times daily OR senna 2-3 tablets twice to three times daily with a goal of one non-forced bowel movement every 1-2 days. 1, 4

• Bisacodyl and senna are the most commonly used agents in ICU bowel protocols (75.6% and 81.0% of protocols respectively) 4
• These stimulant laxatives increase bowel motility and are well-tolerated in critically ill patients 1

Second-Line: Add Stool Softeners and Osmotic Agents

If constipation persists after 24-48 hours of stimulant laxatives:

• Add docusate sodium as a stool softener in combination with stimulant laxatives 1, 4
• Consider osmotic laxatives: polyethylene glycol (1 capful in 8 oz water twice daily), lactulose 30-60 mL 2-4 times daily, or magnesium hydroxide 30-60 mL once to twice daily 1
• Polyethylene glycol is used in 37.8% of ICU bowel protocols and is generally well-tolerated 4

Third-Line: Rectal Interventions

For persistent constipation despite oral laxatives:

• Glycerin suppository (one rectally daily to twice daily) as initial rectal intervention 1, 2
• Bisacodyl suppository (10 mg rectally once to twice daily) if glycerin suppository ineffective 1
• Mineral oil retention enema may be combined with suppositories for more complete resolution 1, 2
• Manual disimpaction should be performed following premedication with analgesics ± anxiolytics if impaction is confirmed 1

Fourth-Line: Prokinetic Agents

Consider metoclopramide 10-20 mg orally four times daily if gastroparesis or upper GI dysmotility is suspected. 1

• Prokinetic agents address upper digestive tract dysmotility that may contribute to overall gastrointestinal dysfunction 5

Specialized Agents for Opioid-Induced Constipation

For patients on high-dose opioids with refractory constipation, consider methylnaltrexone 0.15 mg/kg subcutaneously every other day (maximum once daily). 1

• Methylnaltrexone is a peripherally-acting opioid antagonist that relieves opioid-induced constipation while maintaining analgesia 1
• Contraindicated in mechanical bowel obstruction and post-operative ileus 1
• This represents a promising strategy for patients requiring ongoing opioid therapy 5

Protocol Activation and Monitoring

Bowel protocols should be nurse-activated based on predefined criteria, with the most common being absence of bowel movement for 24-96 hours. 4

• 79.5% of ICUs utilize formal bowel protocols, with nurses activating them in 62.8% of cases 4
• Other activation criteria include opioid use (18.9%), ICU admission (8.1%), and feeding initiation (10.8%) 4
• The most clinically relevant definition of constipation in ICU is absence of stool for the first 6 days after admission 5

Escalation Criteria

Escalate therapy based on:

• Time from last bowel movement (most common criterion, used in 59.4% of protocols) 4
• Ongoing opioid use (18.9% of protocols) 4
• Absence of stool on digital rectal examination (10.8% of protocols) 4

Discontinuation Criteria

Discontinue laxative therapy when diarrhea develops, as this is included as a discontinuation criterion in 40.5% of ICU bowel protocols 4

Important Caveats and Contraindications

• Avoid enemas in patients with neutropenia, thrombocytopenia, recent colorectal surgery, anal trauma, or severe colitis 2
• Systematic gastric residual volume monitoring should be avoided as it does not reliably predict lower GI dysfunction 5
• Despite widespread use, bowel protocols have not been definitively shown to reduce ICU length of stay, mechanical ventilation duration, or mortality (low-quality evidence) 6
• However, protocols show a trend toward reducing constipation (RR 0.50,95% CI 0.25-1.01, p=0.05) 6

Stress Ulcer Prophylaxis Considerations

All critically ill patients with risk factors for stress-related upper GI bleeding should receive either proton pump inhibitors or H2 receptor antagonists at low-dose regimens. 1

• Risk factors include coagulopathy, shock, and chronic liver disease 1
• Prophylaxis should be discontinued when critical illness resolves or risk factors are no longer present 1
• This is relevant as stress ulcer prophylaxis is routine in ICU but should not be confused with constipation management 1