What is the preferred fluid for resuscitation, Lactated Ringer's (LR) solution or Normal Saline (NS), in pregnant and postpartum women?

Lactated Ringer's Solution Over Normal Saline for Pregnant and Postpartum Women

Lactated Ringer's solution (LR) should be used instead of normal saline (NS) for fluid resuscitation in pregnant and postpartum women, as recommended by the Surviving Sepsis Campaign guidelines which specifically advise balanced crystalloids over normal saline in sepsis and septic shock. 1

Guideline-Based Recommendations

Primary Recommendation for Obstetric Patients

• The Surviving Sepsis Campaign (SSC) guidelines explicitly recommend balanced crystalloid solutions (such as lactated Ringer's solution or Plasma-Lyte) instead of normal saline for resuscitation in patients with sepsis or septic shock. 1

• This recommendation applies directly to pregnant and postpartum women with sepsis, who face unique physiological challenges including lower colloid oncotic pressure and higher risk of pulmonary edema during pregnancy. 1

Rationale for Balanced Crystalloids in Pregnancy

• Normal saline causes hyperchloremic metabolic acidosis, renal vasoconstriction, increased cytokine secretion, and increased risk of acute kidney injury - all particularly concerning in the pregnant population already at risk for complications. 1

• Balanced crystalloid solutions like LR have near-physiological electrolyte concentrations and lower chloride content, reducing the risk of these adverse effects. 2, 3

• Large randomized controlled trials (SMART trial with 15,802 critically ill patients) demonstrated that balanced crystalloids resulted in lower rates of major adverse kidney events compared to normal saline. 2, 3

Clinical Application Algorithm

For Septic Pregnant/Postpartum Patients

• Initial fluid bolus: Start with 1-2 L of lactated Ringer's solution, with consideration to escalate to 30 mL/kg within the first 3 hours for patients in septic shock or those with inadequate response to initial bolus. 1

• Target mean arterial pressure (MAP): Aim for 65 mm Hg, though this threshold has not been specifically validated in pregnant patients. 1

• Volume status monitoring: Perform assessment within 6 hours if hypotension persists after fluid administration or if initial lactate level is ≥4 mmol/L. 1

For General Resuscitation Needs

• First-line choice: Lactated Ringer's solution for most patients requiring fluid resuscitation. 2

• If normal saline must be used: Limit to maximum 1-1.5 L to minimize hyperchloremic effects. 2, 3

Important Caveats and Contraindications

When to Avoid Lactated Ringer's

• Traumatic brain injury: Use normal saline rather than LR in patients with TBI, as LR was associated with increased mortality in this specific population (hazard ratio 1.78). 2, 4

• This is critical because hypotonic solutions like Ringer's lactate can cause fluid shifts into damaged cerebral tissue. 3

Special Pregnancy Considerations

• Pregnant women have lower colloid oncotic pressure and higher risk of pulmonary edema, making careful fluid management essential even when using the preferred balanced crystalloid. 1

• The Society for Maternal-Fetal Medicine (SMFM) recommends tailoring fluid volume to the patient's condition rather than automatically administering the full 30 mL/kg, particularly given these physiological changes. 1

• If initial fluid bolus of less than 30 mL/kg is given, CMS requires documentation of clinical reason and specific amount ordered. 1

Supporting Evidence Beyond Sepsis

• In massive hemorrhage models, LR required significantly less volume (125.7 mL/kg vs 256.3 mL/kg) and resulted in less acidosis and better coagulation profiles compared to NS. 5, 6

• LR resuscitation in acute pancreatitis was associated with lower 1-year mortality (adjusted OR 0.61) compared to NS. 7

• However, a recent large hospital-wide crossover trial showed no significant difference in death or readmission at 90 days between LR and NS in general hospitalized patients, though this was not specific to pregnant populations or sepsis. 8

Monitoring Parameters

• Regular assessment of acid-base status through arterial or venous blood gases. 3

• Monitoring of serum electrolytes, particularly chloride levels. 3

• Assessment of renal function and urine output. 3

• Fluid balance monitoring to avoid volume overload, especially critical given pregnancy-related increased risk of pulmonary edema. 1, 3