What is the best normal saline (sodium chloride solution) to administer to a teenager?

Normal Saline Administration in Teenagers

For teenagers requiring intravenous fluid resuscitation, isotonic 0.9% normal saline is the recommended first-line crystalloid, administered at 20 mL/kg boluses for severe dehydration or shock, with careful monitoring of clinical response. 1

Clinical Context and Indications

The choice of normal saline depends entirely on the clinical scenario:

Severe Dehydration or Shock

• Administer intravenous isotonic crystalloid (0.9% normal saline or lactated Ringer's) as 20 mL/kg boluses until pulse, perfusion, and mental status normalize 1
• For adolescents weighing ≥30 kg with severe dehydration, this translates to rapid boluses repeated as needed based on clinical response 1
• The American Academy of Allergy, Asthma, and Immunology recommends 0.9% normal saline as the preferred crystalloid for emergency fluid replacement in shock states due to its immediate volume expansion capability 2

Mild to Moderate Dehydration

• Oral rehydration solution (ORS) is first-line therapy, not intravenous saline 1
• Adolescents should receive 2-4 L of ORS over 3-4 hours for rehydration 1
• Only transition to IV fluids if ORS fails, there is altered mental status, or ileus is present 1

Maintenance Fluid Therapy

• If unable to take oral fluids, administer 5% dextrose in 0.25% normal saline with 20 mEq/L potassium chloride intravenously 1
• This hypotonic solution is appropriate for maintenance, not resuscitation 1
• For standard maintenance in isonatremic states, 5% dextrose in 0.45% saline with 20 mEq/L KCl over 24 hours is recommended 3

Important Caveats and Pitfalls

Avoid Common Errors

• Do not use 0.9% normal saline for routine maintenance therapy - it provides excessive sodium and chloride that can lead to hyperchloremic metabolic acidosis 4, 5
• Recent evidence demonstrates that normal saline causes more metabolic acidosis, acute kidney injury, and potential mortality compared to balanced crystalloids like lactated Ringer's or Plasma-Lyte 4, 5
• The excess chloride concentration (154 mEq/L vs. 100 mEq/L in plasma) is the primary culprit for these adverse effects 4

Special Populations Requiring Monitoring

• Patients with congestive heart failure or chronic renal disease need close monitoring to prevent volume overload 2
• Establish continuous vital sign monitoring during rapid fluid administration 2
• In conditions with increased vascular permeability (like anaphylaxis), up to 50% of intravascular fluid may shift to extravascular space within 10 minutes, requiring larger volumes 2

Type of Dehydration Matters

• Hypernatremic dehydration requires slower correction with more hypotonic solutions (5% dextrose in 0.2% saline with 20 mEq/L KCl over 2-3 days) to avoid cerebral edema 3
• Hyponatremic dehydration is best treated with alternating 0.9% and 0.45% saline in 5% dextrose with 20 mEq/L KCl 3
• Isonatremic dehydration responds well to 5% dextrose in 0.45% saline with 20 mEq/L KCl 3

Practical Algorithm

1. Assess severity of dehydration and hemodynamic status

   • Severe dehydration/shock → 0.9% normal saline 20 mL/kg boluses 1
   • Mild-moderate dehydration → ORS first-line 1

2. Once circulation restored, transition to appropriate maintenance

   • If tolerating oral intake → continue ORS 1
   • If NPO required → 5% dextrose in 0.25-0.45% saline with KCl 1, 3

3. Monitor for complications

   • Check electrolytes, especially sodium 3
   • Assess urinary output and clinical response 1
   • Watch for signs of volume overload in at-risk patients 2