What are the commonly used physiological electrolyte solutions?

Commonly Used Physiological Electrolyte Solutions

Balanced crystalloid solutions should be used in preference to 0.9% normal saline for fluid resuscitation and maintenance of intravascular volume due to their more physiological composition and reduced risk of hyperchloremic metabolic acidosis. 1

Types of Physiological Electrolyte Solutions

Crystalloid Solutions

• Balanced Crystalloid Solutions:

  • Examples include Ringer's lactate, Plasma-Lyte, and other solutions with electrolyte compositions closer to plasma 1
  • Contain physiological or near-physiological concentrations of chloride 1
  • Associated with lower rates of hyperchloremic metabolic acidosis compared to normal saline 2
  • Recommended as first-line fluid therapy in hypotensive bleeding trauma patients 1

• 0.9% Sodium Chloride (Normal Saline):

  • Contains equal concentrations of sodium and chloride (154 mmol/L each) 1, 3
  • Non-physiological due to supraphysiological chloride content (plasma chloride is normally 40 mmol/L lower than sodium) 3, 4
  • If used, should be limited to a maximum of 1-1.5 L to avoid hyperchloremic acidosis 1
  • Should be avoided in patients with severe acidosis, especially when associated with hyperchloremia 1

• Hypotonic Solutions:

  • Examples include some formulations of Ringer's lactate 1
  • Should be avoided in patients with severe head trauma to minimize fluid shift into damaged cerebral tissue 1

Colloid Solutions

• Use is restricted due to adverse effects on hemostasis 1
• Examples include:
  • Hydroxyethyl starch (HES) solutions (not recommended due to increased risk of kidney failure) 1
  • Gelatins and albumin 1
• May result in lower fluid requirements than crystalloids (ratio of 1.5:1) 1

Clinical Considerations for Solution Selection

Benefits of Balanced Solutions

• Lower incidence of hyperchloremic metabolic acidosis 1, 2
• Reduced risk of kidney injury and renal dysfunction 1
• Lower 30-day mortality in critically ill patients 1
• Slight reduction in hospital length of stay 5
• Better acid-base balance with higher blood pH and bicarbonate levels 5
• Reduced risk of hypokalaemia after intravenous correction 5

Risks of 0.9% Saline

• Hyperchloremic metabolic acidosis in a dose-dependent manner 2, 3
• Decreased kidney perfusion and urine output 1
• Increased extravascular fluid accumulation 1
• Increased vasopressor requirements 1
• Higher risk of acute kidney injury 1, 2
• Electrolyte derangements 1
• Dilutional coagulopathy 1
• Higher overall volume requirements for adequate resuscitation 1

Special Populations

Trauma Patients

• Balanced electrolyte solutions are favored as the initial crystalloid solution 1
• If 0.9% saline is used, it should be limited to 1-1.5 L maximum 1
• Avoid hypotonic solutions in patients with traumatic brain injury 1

Pediatric Patients

• For children with severe dehydration due to diarrhea, balanced solutions likely result in a slight reduction of hospital stay compared to 0.9% saline 5
• For parenteral nutrition in neonates and children, balanced solutions with appropriate sodium, potassium, and chloride content are recommended based on age and weight 1
• For oral rehydration in children with diarrhea, glucose-containing reduced osmolarity WHO oral rehydration solution is preferred 1, 6

Common Pitfalls and Caveats

• Overuse of 0.9% saline: Despite being called "normal" saline, 0.9% NaCl has no scientific or historical basis for this name and is not physiologically normal 7
• Ignoring existing electrolyte abnormalities: Patients with pre-existing acidosis or hyperchloremia should avoid 0.9% saline 1
• Fluid overload: Excessive administration of any crystalloid can lead to edema that impairs pulmonary gas exchange and tissue oxygenation 2
• Using sports drinks or juice for rehydration: These are not recommended for treating dehydration due to illness as they have inappropriate electrolyte compositions 6

Monitoring Recommendations

• Monitor serum electrolyte concentrations, especially in critically ill patients 1
• Assess acid-base status in patients receiving large volumes of fluids 1, 2
• Monitor for signs of hyperchloremic acidosis when using 0.9% saline 2
• Evaluate renal function in patients receiving large volumes of fluids 1

In conclusion, while both 0.9% saline and balanced crystalloid solutions are commonly used physiological electrolyte solutions, current evidence favors balanced crystalloids for most clinical scenarios due to their more physiological composition and reduced risk of adverse effects.