Fluid Administration in Adults and Pediatric Patients
Adults
For adults with mild to moderate dehydration, reduced osmolarity oral rehydration solution (ORS) is the first-line therapy, while isotonic intravenous fluids (lactated Ringer's or normal saline) should be administered for severe dehydration, shock, or altered mental status. 1
Initial Assessment and Fluid Choice
- Begin with isotonic saline (0.9% NaCl) at 15-20 mL/kg/hour (approximately 1-1.5 liters) during the first hour for volume expansion 1, 2
- After initial resuscitation, fluid choice depends on corrected serum sodium: 1, 2
Oral Rehydration Protocol
- For mild-moderate dehydration without shock, give ORS at volumes based on ongoing losses: 1
- Continue ORS until clinical dehydration is corrected 1
Electrolyte Replacement
- Once urine output is confirmed, add 20-30 mEq/L potassium (2/3 KCl and 1/3 KPO4) to IV fluids 1
- Never add potassium before confirming adequate renal function 2, 3
Critical Monitoring Parameters
- Monitor blood pressure, pulse, perfusion, mental status, and urine output 1, 2
- The change in serum osmolality must not exceed 3 mOsm/kg/hour to prevent central pontine myelinolysis 1, 2
- Correct estimated fluid deficits within 24 hours 1, 2
Transition to Maintenance
- Once rehydrated, switch to maintenance fluids and replace ongoing stool losses with ORS 1
- Resume age-appropriate diet immediately after rehydration 1
Pediatric Patients
For children with mild to moderate dehydration, oral rehydration solution is first-line therapy at 50-100 mL after each stool for children under 2 years and 100-200 mL for older children, while intravenous isotonic saline at 10-20 mL/kg/hour is indicated for severe dehydration with a critical safety limit of 50 mL/kg over the first 4 hours. 1, 2
Initial Fluid Resuscitation
- Start with isotonic saline (0.9% NaCl) at 10-20 mL/kg/hour for the first hour 1, 2
- In severely dehydrated patients, this may be repeated but total reexpansion must not exceed 50 mL/kg over the first 4 hours to prevent cerebral edema 1, 2
- Calculate remaining fluid replacement over 48 hours, not 24 hours as in adults 2
Oral Rehydration Protocol
- Children <2 years: 50-100 mL of ORS after each stool 1
- Children >2 years: 100-200 mL of ORS after each stool 1
- Nasogastric ORS administration may be used in children with moderate dehydration who cannot tolerate oral intake 1
Subsequent IV Fluid Management
- Once renal function is assured, add 20-40 mEq/L potassium (2/3 KCl or potassium-acetate and 1/3 KPO4) 1
- When serum glucose reaches 250 mg/dL (in diabetic ketoacidosis), change to 5% dextrose with 0.45-0.75% NaCl 1
- For general dehydration, a regimen of 0.9% saline + 2.5% dextrose at 20 mL/kg/hour for 2 hours has proven safe and effective 4
Critical Safety Considerations
- Monitor mental status continuously to rapidly identify cerebral edema 1, 2
- Never exceed 3 mOsm/kg/hour change in osmolality 1, 2
- Frequent assessment of cardiac, renal, and mental status is mandatory during fluid resuscitation 1, 2
Feeding During Illness
- Continue breastfeeding throughout the diarrheal episode 1
- For infants on formula, dilute with equal volume of clean water until diarrhea stops 1
- For children >4-6 months, offer freshly prepared foods (cereal-bean or cereal-meat mixes with vegetable oil) every 3-4 hours 1
- Resume normal age-appropriate diet immediately after rehydration is complete 1
Common Pitfalls to Avoid
- Never use salt-containing solutions (0.9% NaCl) in nephrogenic diabetes insipidus as their tonicity (
300 mOsm/kg) exceeds typical urine osmolality (100 mOsm/kg), requiring 3 liters of urine to excrete 1 liter of isotonic fluid 1 - Never administer excessive fluids in patients with cardiac or renal compromise as this precipitates pulmonary edema 2, 3
- Never use rapid adult protocols in children without modification as cerebral edema risk is substantially higher 1, 2
- Avoid antimotility drugs (loperamide) in all children <18 years with acute diarrhea 1