What are the best indications for using intravenous (IV) saline versus lactated Ringer's in Emergency Medical Services (EMS)?

Indications for IV Saline vs Lactated Ringer's in EMS

In EMS settings, balanced crystalloids like Lactated Ringer's should generally be used as first-line fluid therapy for most patients, while 0.9% saline should be reserved for specific indications such as traumatic brain injury, severe hyponatremia, or metabolic alkalosis. 1

General Fluid Selection Principles

• Balanced crystalloids (like Lactated Ringer's) are preferred for most resuscitation scenarios due to lower risk of hyperchloremic acidosis compared to normal saline 1
• Normal saline (0.9% NaCl) should be limited to a maximum of 1-1.5L when used, due to risk of hyperchloremic acidosis 1
• Fluid choice should be guided by the patient's underlying condition, with special considerations for specific clinical scenarios 1

Specific Indications for Normal Saline (0.9% NaCl)

• Traumatic Brain Injury (TBI): Normal saline is strongly recommended as first-line fluid therapy in TBI patients 1, 2
• Severe Hyponatremia: Normal saline helps correct sodium deficits without diluting serum sodium further 1
• Metabolic Alkalosis: The relative acidifying effect of normal saline can help correct alkalosis 3
• Diabetic Ketoacidosis (DKA): Traditionally used, though recent evidence suggests balanced solutions may be beneficial 4

Specific Indications for Lactated Ringer's

• Hemorrhagic Shock (without TBI): Balanced solutions like LR are preferred for resuscitation in trauma with significant blood loss 1, 5
• Sepsis: Balanced crystalloids are preferred to reduce risk of kidney injury and hyperchloremic acidosis 3
• Lactic Acidosis: Contrary to common misconception, LR does not significantly worsen lactic acidosis despite containing lactate 3, 6
• Burns: LR is traditionally preferred for initial fluid resuscitation in burn patients 1

Contraindications and Cautions

• Avoid Lactated Ringer's in:

  • Traumatic brain injury patients (use normal saline instead) 1, 2
  • Severe liver dysfunction (impaired lactate metabolism) 3
  • Severe hyperkalemia (LR contains potassium) 1

• Avoid Normal Saline in:

  • Severe acidosis, especially with hyperchloremia 1, 3
  • Patients requiring large volume resuscitation (>1.5L) due to risk of hyperchloremic acidosis 1, 5

Volume Considerations

• Both fluids should be administered according to the patient's clinical condition and hemodynamic response 1
• In hemorrhagic shock, a strategy of restricted volume replacement is recommended until bleeding is controlled 1
• Target systolic blood pressure of 80-90 mmHg in hemorrhagic shock without TBI 1

Common Pitfalls to Avoid

• Myth: LR significantly raises serum lactate levels - Research shows minimal clinically significant effect on lactate levels even with large volumes 6
• Myth: Normal saline is always safer - In large volumes, NS can cause hyperchloremic acidosis and potentially worsen outcomes 5
• Myth: Fluid type doesn't matter - Evidence shows different outcomes based on fluid choice in specific clinical scenarios 5, 2, 4

Remember that while these guidelines provide direction, the clinical context and patient-specific factors remain important considerations in fluid selection for EMS scenarios 1.