Balanced Crystalloids for Fluid Resuscitation
Use lactated Ringer's solution or Plasma-Lyte as the balanced crystalloid of choice for fluid resuscitation in most clinical scenarios, including obese patients with rhabdomyolysis, with the critical exception that normal saline (0.9% NaCl) should be used instead of lactated Ringer's in rhabdomyolysis due to the potassium content risk. 1, 2, 3
Examples of Balanced Crystalloids
The primary balanced crystalloid solutions available are:
- Lactated Ringer's solution (Ringer's Lactate) - contains sodium 130 mmol/L, potassium 4 mmol/L, chloride 109 mmol/L, lactate 28 mmol/L 1, 2
- Plasma-Lyte (Plasmalyte A) - contains physiologic electrolyte concentrations with sodium 140 mmol/L, potassium 5 mmol/L, chloride 98 mmol/L 4, 5
- Isofundine - contains sodium 145 mmol/L, potassium 4 mmol/L, chloride 127 mmol/L 4
Why Balanced Crystalloids Are Preferred
Balanced crystalloids reduce 30-day mortality (OR 0.84,95% CI 0.74-0.95) and major adverse kidney events compared to normal saline in critically ill patients. 2, 4 The SMART trial of 15,802 ICU patients demonstrated that balanced crystalloids significantly decreased the composite outcome of death, renal replacement therapy, or persistent renal dysfunction within 30 days (14.3% vs 15.4%). 6, 2
The mechanism of benefit relates to electrolyte composition closer to plasma, which prevents hyperchloremic metabolic acidosis that causes renal vasoconstriction and acute kidney injury. 1, 2 Normal saline contains supraphysiologic chloride concentration (154 mmol/L) that worsens acidosis and increases mortality when hyperchloremia develops. 1, 2
Critical Exception: Rhabdomyolysis
In rhabdomyolysis, use normal saline (0.9% NaCl) rather than balanced crystalloids due to the potassium content in balanced solutions. 1 Rhabdomyolysis causes massive release of intracellular potassium into circulation, creating life-threatening hyperkalemia risk. 3, 7 The 4-5 mmol/L potassium in lactated Ringer's or Plasma-Lyte, while physiologic in other contexts, becomes dangerous when added to already elevated serum potassium from muscle breakdown. 1
Management of rhabdomyolysis requires:
- Aggressive intravenous normal saline resuscitation to maintain urine output ≥300 mL/hour 3
- Immediate serum potassium measurement and electrocardiogram to identify hyperkalemia complications 3, 7
- Continue fluids until creatine kinase levels fall below 1,000 U/L 3
- Consider sodium bicarbonate for acidotic patients and mannitol if urine output goals not met 3, 7
Additional Contraindications to Balanced Crystalloids
Avoid lactated Ringer's in severe traumatic brain injury or head trauma due to its slightly hypotonic nature (osmolarity 273 mOsm/L), which can worsen cerebral edema. 6, 1, 4 One study showed increased mortality with pre-hospital lactated Ringer's versus normal saline in TBI patients (HR 1.78,95% CI 1.04-3.04). 8
Guideline Recommendations Across Clinical Scenarios
For sepsis and septic shock: The Surviving Sepsis Campaign recommends crystalloids as first-line fluid with either balanced crystalloids or saline acceptable, though balanced crystalloids show mortality benefit particularly when initiated in the emergency department. 6, 5 The effect was greater when fluid choice was controlled starting in the ED (OR 0.68,95% CI 0.52-0.89) versus ICU only (OR 1.14,95% CI 0.70-1.88). 5
For hemorrhagic shock and trauma: European guidelines recommend crystalloids as initial fluid choice over colloids, with balanced solutions preferred to avoid hyperchloremic acidosis from large volume resuscitation. 6 Trauma patients commonly require >5,000-10,000 mL in first 24 hours, making fluid composition critically important. 6
For emergency laparotomy: The ERAS Society strongly recommends balanced crystalloids over normal saline, especially in high-risk patients with existing acidosis or hyperchloremia who require significant fluid volumes. 6
For renal patients: KDIGO guidelines recommend isotonic crystalloids over colloids, with balanced crystalloids specifically reducing acute kidney injury risk. 1, 4 The potassium content should not be considered a contraindication even in renal dysfunction, as renal transplant recipients receiving normal saline actually developed higher potassium levels than those receiving lactated Ringer's. 1
What to Avoid
Never use hydroxyethyl starch solutions - they increase renal failure risk (RR 1.34,95% CI 1.0-1.8) and mortality without demonstrating benefit. 6 The Surviving Sepsis Campaign provides a strong recommendation against HES with high-quality evidence. 6
Limit normal saline use to specific indications (rhabdomyolysis, severe TBI) and avoid large volumes (>1-1.5 L) in other scenarios due to association with hyperchloremic acidosis, increased vasopressor requirements, and major adverse kidney events. 6, 1, 2
Albumin is not recommended for routine fluid resuscitation as it shows no mortality benefit and costs significantly more than crystalloids. 6 Consider only when patients require substantial crystalloid amounts in sepsis. 6
Common Pitfalls
Do not assume potassium in balanced crystalloids is dangerous for all patients - it is physiologically impossible to create hyperkalemia using fluid with potassium concentration equal to or lower than plasma except in rhabdomyolysis/crush syndrome. 1 Do not continue outdated protocols using large volume normal saline based on pre-2018 practice patterns. 2 Do not delay balanced crystalloid initiation in sepsis until ICU admission, as early ED use provides greater mortality benefit. 5