What is the difference between saline and lactated Ringer's (LR) solution for fluid resuscitation or maintenance?

Differences Between Saline and Lactated Ringer's Solution for Fluid Resuscitation or Maintenance

For most patients requiring fluid resuscitation or maintenance, balanced crystalloid solutions such as Lactated Ringer's (LR) are preferred over normal saline (0.9% sodium chloride) due to lower risk of hyperchloremic acidosis and potential reduction in adverse renal outcomes. 1

Composition Differences

• Normal saline (0.9% NaCl) contains 154 mmol/L of both sodium and chloride, making it hyperchloremic compared to plasma 1
• Lactated Ringer's is a balanced solution with near-physiological concentrations of electrolytes and contains lactate as a buffer 1
• LR has lower chloride content than normal saline, which reduces the risk of hyperchloremic metabolic acidosis 1

Clinical Considerations for Selection

Advantages of Balanced Solutions (LR)

• Reduced risk of hyperchloremic acidosis compared to normal saline 1
• Potentially lower rates of acute kidney injury and renal replacement therapy 1
• A large RCT in critically ill patients (n=15,802) showed balanced crystalloids resulted in lower rates of major adverse kidney events compared to saline 1
• May require less total volume for adequate resuscitation in hemorrhagic shock 2
• Associated with reduced 1-year mortality in acute pancreatitis patients 3
• Lower incidence of ICU admission in acute pancreatitis patients 4

Situations Where Normal Saline May Be Preferred

• Traumatic brain injury (TBI) patients - LR should be avoided in severe head trauma 1
• A secondary analysis from the PROMMTT study showed LR was associated with higher adjusted mortality compared to normal saline in TBI patients 1, 5
• Patients with severe metabolic alkalosis 1
• Patients with severe hyponatremia 1

Cautions with Normal Saline

• Can cause hyperchloremic metabolic acidosis with large volume administration 1
• Should be limited to maximum of 1-1.5 L if used 1
• Should be avoided in severe acidosis, especially when associated with hyperchloremia 1
• May require greater volumes for resuscitation in hemorrhagic shock compared to LR 2

Special Populations

Trauma Patients

• European guidelines recommend either 0.9% sodium chloride or balanced crystalloid solutions for initial fluid therapy in hypotensive bleeding trauma patients 1
• However, the authors favor balanced electrolyte solutions as the initial crystalloid solution in trauma patients 1
• Hypotonic solutions like Ringer's lactate should be avoided in patients with severe head trauma 1

Surgical Patients

• In elective orthopedic and colorectal surgery, no clinically meaningful differences in postoperative complications were found between LR and saline 6
• ERAS guidelines for emergency laparotomy suggest balanced crystalloids may result in improved patient outcomes 1

Critically Ill Patients

• The SMART trial showed lower rates of major adverse kidney events with balanced crystalloids versus saline 1
• The SALT trial demonstrated lower 30-day in-hospital mortality and lower incidence of renal replacement therapy with balanced crystalloids versus saline 1

Practical Recommendations

• For most patients requiring fluid resuscitation, balanced crystalloid solutions like LR are preferred first-line 1
• If normal saline is used, limit to 1-1.5 L maximum 1
• In patients with traumatic brain injury, use normal saline rather than LR 1, 5
• In patients with severe acidosis and hyperchloremia, avoid normal saline 1
• Both colloids and crystalloids are effective for fluid resuscitation, but crystalloids are recommended initially due to lower cost and similar outcomes 1

Common Pitfalls

• Using LR in patients with severe traumatic brain injury - this can worsen cerebral edema 1
• Excessive use of normal saline leading to hyperchloremic acidosis 1
• Not considering the patient's existing acid-base status when selecting fluids 1
• Overreliance on a single type of fluid rather than tailoring to the specific clinical situation 1