What are examples of crystalloids?

Examples of Crystalloids for Intravenous Fluid Therapy

Crystalloids are intravenous fluids containing water and electrolytes that can freely cross semipermeable membranes and are commonly used for vascular filling in critically ill patients. 1

Types of Crystalloids

Isotonic Crystalloids (280-310 mOsm/L)

• 0.9% Sodium Chloride (Normal Saline)

  • Contains 154 mmol/L of sodium and 154 mmol/L of chloride 1
  • Osmolarity of 308 mOsm/L 1
  • Most widely used crystalloid historically, especially in North America 2

• Balanced Crystalloids

  • Plasma-Lyte

    • Contains sodium (140 mmol/L), potassium (5 mmol/L), chloride (98 mmol/L), magnesium (3 mmol/L) 3
    • Contains acetate (27 mmol/L) as a buffer 3
    • Osmolarity of 295 mOsm/L 1

  • Isofundine

    • Contains sodium (145 mmol/L), potassium (4 mmol/L), chloride (127 mmol/L), calcium (2.5 mmol/L) 1
    • Contains acetate (27 mmol/L), gluconate (23 mmol/L), and malate (5 mmol/L) 1
    • Osmolarity of 309 mOsm/L 1

Hypotonic Crystalloids (<280 mOsm/L)

• Ringer's Lactate
  • Contains sodium (130 mmol/L), potassium (4 mmol/L), chloride (108 mmol/L), calcium (0.9 mmol/L) 1
  • Contains lactate (27.6 mmol/L) as a buffer 1
  • Osmolarity of 277 mOsm/L 1
  • Should be avoided in patients with severe head trauma due to risk of cerebral edema 1

Hypertonic Crystalloids (>310 mOsm/L)

• 3% Sodium Chloride 1
• 7.5% Sodium Chloride 1

Clinical Considerations When Choosing Crystalloids

Balanced vs. Non-Balanced Crystalloids

• Balanced crystalloids have an electrolyte composition closer to plasma and may reduce the risk of hyperchloremic metabolic acidosis compared to 0.9% saline 4, 2
• The SMART trial demonstrated that balanced crystalloids resulted in lower rates of major adverse kidney events compared to saline in critically ill patients 5
• Balanced crystalloids are recommended as first-line fluid therapy in patients with hemorrhagic shock to reduce mortality and adverse renal events 1

Special Clinical Situations

• Acute Brain Injury: Isotonic crystalloids are recommended as first-line fluid therapy to reduce mortality and improve neurological prognosis 1
• ESRD Patients: Balanced crystalloids like Plasma-Lyte are preferred over 0.9% saline for intraoperative fluid management 4
• Trauma Patients: The European guideline on management of major bleeding recommends 0.9% sodium chloride or balanced crystalloid solution for initial fluid therapy 1

Potential Adverse Effects

• High volumes of 0.9% saline can lead to hyperchloremic metabolic acidosis 2, 4
• Hypotonic solutions can worsen cerebral edema in patients with traumatic brain injury 1
• The potassium content in balanced solutions (4-5 mmol/L) is generally not a concern even in patients prone to hyperkalemia 4

Crystalloids vs. Colloids

• Crystalloids are recommended over colloids for initial fluid resuscitation 1
• Colloids (such as hydroxyethyl starch, dextrans, gelatins, and albumin) should be restricted due to adverse effects on hemostasis 1
• A meta-analysis found no difference in mortality between critically ill patients receiving crystalloids versus colloids 6

Crystalloids remain the cornerstone of fluid therapy in critically ill patients, with balanced solutions increasingly preferred over 0.9% saline due to their more physiologic composition and potentially improved clinical outcomes 2, 5.