What is the dose of maintenance fluids for a 42.2kg female with moderate dehydration?

Maintenance Fluid Dosing for Moderate Dehydration in a 42.2kg Female

For a 42.2kg female with moderate dehydration, administer oral rehydration solution (ORS) at 120-240 mL after each diarrheal stool or vomiting episode, up to approximately 1 liter per day, until clinical dehydration is corrected. 1

Route Selection: Oral vs Intravenous

Oral rehydration solution is the first-line treatment for moderate dehydration in adults who can tolerate oral intake. 1 The Infectious Diseases Society of America provides strong evidence (strong, low quality) that adults with mild to moderate dehydration should receive ORS until clinical dehydration is corrected. 1

When to Use Intravenous Fluids Instead

Isotonic intravenous fluids (lactated Ringer's or normal saline) should only be administered if: 1

• The patient cannot tolerate oral fluids due to persistent vomiting 2
• There is altered mental status 1
• Signs of shock are present 1
• Ileus is present 1, 3
• ORS therapy has failed 1

Oral Rehydration Protocol (Preferred for Moderate Dehydration)

Rehydration Phase

• Administer 120-240 mL of ORS after each diarrheal stool or vomiting episode 1
• Maximum daily intake: approximately 1 liter (up to 2 liters if tolerated) 1
• Continue until clinical signs of dehydration resolve (normal pulse, perfusion, mental status) 1

Maintenance Phase (After Rehydration Complete)

• Resume normal age-appropriate diet every 3-4 hours 1
• Continue replacing ongoing losses with ORS until diarrhea/vomiting resolves 1
• Target daily fluid intake: 1.6 liters for women 1

Intravenous Fluid Protocol (If ORS Not Tolerated)

Initial Resuscitation

• Administer 20 mL/kg isotonic crystalloid bolus (approximately 844 mL for 42.2kg patient) over the first hour 4
• Use lactated Ringer's or normal saline 1, 4
• Reassess pulse, perfusion, mental status, and urine output after the bolus 4

Maintenance IV Fluids

• Transition to 1.5 mL/kg/hour (approximately 63 mL/hour for 42.2kg patient) once hemodynamically stable 4
• This equals approximately 100-125 mL/hour or 2.4-3.0 liters per day 4
• Use buffered crystalloid solutions (lactated Ringer's preferred over normal saline) 4
• Add 20 mEq/L potassium chloride after urine output is established 1, 2

Monitoring Parameters During IV Therapy

• Reassess vital signs every 1-2 hours during active resuscitation 4
• Target urine output: 0.5-1 mL/kg/hour (21-42 mL/hour for 42.2kg patient) 4
• Check electrolytes (sodium, potassium) every 6-12 hours 2
• Avoid positive fluid balance exceeding 1-2 liters by end of resuscitation period 4

Transition Strategy

Transition from IV to oral rehydration as soon as the patient can tolerate oral intake. 2 Begin with 120-240 mL of ORS after each loose stool while gradually decreasing the IV fluid rate. 2

Critical Pitfalls to Avoid

• Do not use hypotonic solutions (0.45% saline alone) for initial resuscitation 4
• Do not use popular beverages like apple juice, Gatorade, or soft drinks for rehydration 1
• Do not exceed 3-4 liters total IV fluids in first 24 hours unless ongoing losses are documented 4
• Do not add potassium to initial IV fluids until renal function is confirmed and patient is producing urine 4, 2
• Do not use dextrose-containing solutions during initial resuscitation unless hypoglycemia is present 4

Clinical Assessment of Adequate Rehydration

The patient is adequately rehydrated when: 1, 4

• Pulse normalizes
• Perfusion improves (capillary refill <2 seconds)
• Mental status returns to baseline
• Urine output is adequate (>0.5 mL/kg/hour)