Fluid Management for Diarrhea
Primary Recommendation
For mild to moderate dehydration, use reduced osmolarity oral rehydration solution (ORS) as first-line therapy; escalate to intravenous isotonic fluids (lactated Ringer's or normal saline) only for severe dehydration, shock, altered mental status, or failure of oral therapy. 1
Oral Rehydration Strategy
Mild to Moderate Dehydration
Administer reduced osmolarity ORS (osmolarity <250 mmol/L) containing 65-70 mEq/L sodium and 75-90 mmol/L glucose for all ages and causes of diarrhea 1
Dosing for mild dehydration (3-5% fluid deficit): Give 50 mL/kg over 2-4 hours 2
Dosing for moderate dehydration (6-9% fluid deficit): Give 100 mL/kg over 2-4 hours 2
Commercial ORS products include Pedialyte, CeraLyte, and Enfalac Lytren 1
Avoid inappropriate fluids: Do not use apple juice, Gatorade, sports drinks, or commercial soft drinks for rehydration 1
Administration Technique for Vomiting Patients
Give small, frequent volumes (5-10 mL every 1-2 minutes via spoon or syringe) rather than allowing ad libitum drinking, which worsens vomiting 1
Consider nasogastric ORS administration for patients who cannot tolerate oral intake but have normal mental status 1
Continuous slow nasogastric infusion can be helpful for persistent vomiting 1
Intravenous Rehydration
Indications for IV Fluids
Switch to IV therapy when: 1
- Severe dehydration (≥10% fluid deficit) is present
- Signs of shock or hemodynamic instability exist
- Altered mental status develops
- ORS therapy fails
- Intestinal ileus is present
- Ketonemia prevents oral tolerance
IV Fluid Protocol
Initial resuscitation: Give 20 mL/kg boluses of lactated Ringer's solution or normal saline for shock or severe dehydration 1
Continue IV fluids until pulse, perfusion, and mental status normalize, then transition to ORS for remaining deficit 1
Fluid rate must exceed ongoing losses: Calculate as urine output + insensible losses (30-50 mL/h) + gastrointestinal losses 1
Target urine output: Maintain >0.5 mL/kg/h 1
Avoid rapid fluid resuscitation in mild to moderate hypovolemia 1
Maintenance and Ongoing Losses
After rehydration is complete: Replace ongoing stool losses with ORS until diarrhea resolves 1
Total daily fluid requirements: Prescribe 2200-4000 mL/day depending on ongoing losses 1
Continue breastfeeding throughout the illness without interruption 1
Resume age-appropriate diet immediately after rehydration is complete 1
Special Populations and Cautions
Elderly Patients
ORS is indicated for all elderly patients with grade 2 or higher diarrhea, as they have the highest risk of complications 1
Monitor for overhydration in patients with chronic heart or kidney failure 1
Cancer Patients
Grade 3-4 diarrhea requires IV fluids regardless of dehydration severity 1
Consider central venous pressure monitoring for severe cases, balanced against infection/bleeding risks 1
Pediatric Considerations
ORS success rate exceeds 96% in children when properly administered 1
For children 2-5 years (≤20 kg): Use liquid formulation (1 mg/5 mL) rather than capsules 3
Critical Pitfalls to Avoid
Do not allow thirsty patients to drink large volumes rapidly from a cup or bottle—this worsens vomiting and leads to ORS failure 1
Do not use antimotility agents (loperamide) in children <18 years or in any patient with fever, bloody/mucous stools, or suspected inflammatory diarrhea 1, 2
Do not withhold ORS simply because of high stool output (>10 mL/kg/hour)—most patients still respond with adequate replacement 1
Reassess frequently during fluid administration to ensure dehydration is not worsening 1