What is the best course of action for a 9-month-old infant experiencing vomiting and diarrhea for 24 hours?

Management of 9-Month-Old Infant with Vomiting and Diarrhea

Begin oral rehydration therapy immediately with ORS (oral rehydration solution) at 100 mL/kg over 2-4 hours if the infant shows signs of moderate dehydration (6-9% fluid deficit), which is likely given the 24-hour duration of symptoms with vomiting and diarrhea. 1, 2

Initial Assessment of Dehydration Severity

First, determine the degree of dehydration by examining specific clinical signs:

• Look for prolonged capillary refill time, abnormal skin turgor (prolonged skinfold retraction), sunken eyes, and dry mucous membranes - these are the most reliable indicators of moderate dehydration in infants 2, 3, 4
• Assess for altered neurologic status, decreased urine output, and rapid, deep breathing 2, 4
• Mild dehydration (3-5% deficit) presents with minimal clinical signs, moderate dehydration (6-9% deficit) shows the above signs clearly, and severe dehydration (≥10% deficit) presents with shock, altered mental status, or poor perfusion 1, 2

Rehydration Protocol

For Mild to Moderate Dehydration (Most Likely Scenario)

• Administer ORS containing 50-90 mEq/L of sodium at 100 mL/kg over 2-4 hours 1, 2
• Start with small volumes using a teaspoon, syringe, or medicine dropper (approximately one teaspoon at a time), then gradually increase as tolerated 1, 2
• Commercial formulations include Pedialyte, CeraLyte, or Enfalac Lytren 2, 5
• Reassess hydration status after 2-4 hours; if still dehydrated, reestimate the fluid deficit and restart rehydration therapy 1, 2

Replacing Ongoing Losses

• Give 10 mL/kg of ORS for each watery or loose stool 1, 2
• Give 2 mL/kg of ORS for each episode of vomiting 1, 2
• For infants <10 kg (which includes this 9-month-old), provide 60-120 mL ORS for each diarrheal stool or vomiting episode, up to approximately 500 mL/day 2

Feeding During Illness

• If breastfed, continue nursing on demand throughout the entire illness without interruption 1, 2
• If formula-fed, resume full-strength, lactose-free or lactose-reduced formula immediately upon rehydration 1, 2
• If lactose-free formula is unavailable, full-strength lactose-containing formula can be used under supervision, watching for worsening diarrhea that would indicate lactose intolerance 1
• At 9 months of age, offer age-appropriate solid foods every 3-4 hours as tolerated, including starches, cereals, fruits, and vegetables 1, 2
• Avoid foods high in simple sugars and fats 1

When to Escalate to IV Therapy

Switch to intravenous rehydration if:

• The infant progresses to severe dehydration with shock (≥10% fluid deficit), altered mental status, or poor perfusion 1, 2
• ORS therapy fails after appropriate trial 2
• The infant cannot tolerate oral intake due to persistent vomiting 1
• If IV therapy is needed, administer 20 mL/kg boluses of Ringer's lactate or normal saline until pulse, perfusion, and mental status normalize 1

Monitoring Response

• Reassess clinical signs every 2-4 hours, including skin turgor, mucous membrane moisture, mental status, and perfusion 2, 6
• Monitor stool frequency and consistency 2
• Track weight changes throughout therapy 2

Medications to Avoid

• Do not use antibiotics unless dysentery (bloody diarrhea) is present, high fever persists, or watery diarrhea lasts more than 5 days 1
• Avoid nonspecific antidiarrheal agents in this age group 1

Common Pitfalls

• Do not withhold feeding during rehydration - early refeeding within 24 hours improves outcomes 1, 7
• Do not use hypotonic fluids for parenteral rehydration if IV therapy becomes necessary 8
• The presence of reducing substances in stool without clinical worsening does not indicate lactose intolerance - only worsening diarrhea upon lactose introduction is diagnostic 1