Magnesium Dosage for Constipation in Post-Op Flap Patient on NG Tube Feeds
For a post-operative flap patient on NG tube feeds with constipation, administer 200-400 mg of magnesium daily through the nasogastric tube. 1, 2
Dosing Recommendations
- Start with 200 mg/day of magnesium as recommended in enhanced recovery protocols for pancreatic surgery 1
- Can increase up to 400 mg/day if needed, which is the maximum recommended daily intake for magnesium supplementation 2, 3
- Administer through the NG tube once proper tube placement has been confirmed 1
- Consider dividing into 2-3 doses throughout the day to improve tolerability 2
Administration Method
- Ensure proper NG tube placement before administering any medication 1
- Dilute the magnesium in 30-50 mL of water before administration 1
- Flush the tube with 15-30 mL of water after administration to ensure complete delivery 1
- Can be administered as part of a multimodal approach to stimulate bowel movement 1
Monitoring and Precautions
- Monitor for signs of bowel movement within 24-48 hours of administration 1
- Check renal function before administration as magnesium is contraindicated in significant renal impairment 2, 3
- Monitor for signs of hypermagnesemia (hypotension, nausea, facial flushing, loss of deep tendon reflexes) 4
- Ensure adequate hydration to minimize risk of hypermagnesemia 5
Alternative and Adjunctive Approaches
- Consider adding bisacodyl (10 mg) if magnesium alone is insufficient 1
- Chewing gum has been shown to be beneficial in restoring gut activity after surgery, if the patient can tolerate oral intake 1
- Maintain near-zero fluid balance and optimize pain control to enhance return of bowel function 1
- Early mobilization, when possible, helps stimulate bowel function 1
Evidence Strength and Limitations
- Evidence for specific magnesium dosing in post-operative patients on NG feeds is limited 1
- Magnesium oxide at 800 mg daily (containing approximately 480 mg elemental magnesium) has been shown to reduce constipation in post-cardiac surgery patients 6
- Magnesium hydroxide has demonstrated superior efficacy compared to bulk laxatives in treating constipation in long-term care patients 7
- The osmotic effect of magnesium draws water into the intestinal lumen, softening stool and stimulating bowel movements 2, 5