What is the preferred choice between colloids and crystalloids for fluid resuscitation in adult patients?

Crystalloids Over Colloids for Fluid Resuscitation

Crystalloids should be used as the first-line fluid for resuscitation in critically ill adults, with balanced isotonic crystalloids (such as Ringer's Lactate) preferred over normal saline. 1, 2

Initial Fluid Choice

• Balanced isotonic crystalloids are the clear first-line choice for initial fluid resuscitation in hypovolemic patients, recommended by the American College of Critical Care Medicine, European Society of Anaesthesiology, and European Society of Intensive Care Medicine 1, 2

• Crystalloids provide similar clinical outcomes to colloids but at significantly lower cost (isotonic saline costs approximately 1.5 Euro/liter versus 25 Euro/liter for hydroxyethyl starch or 140 Euro/liter for albumin) 1

• Crystalloids have a lower risk of adverse effects, including renal failure and coagulopathy, compared to colloids 1

Initial Administration Protocol

• Start with 10-20 ml/kg bolus of balanced crystalloid as the initial fluid challenge 1

• For sepsis specifically, administer a minimum of 30 ml/kg of crystalloids during initial resuscitation 2

• Reassess hemodynamic response using dynamic variables (pulse pressure variation, stroke volume variation) and clinical signs of tissue perfusion (capillary refill, skin temperature, mental status, urine output >0.5 ml/kg/hour) 1, 2

Why Crystalloids Are Superior

The evidence strongly favors crystalloids over colloids:

• Mortality outcomes show no benefit with colloids: Multiple high-quality guidelines and the 2018 Cochrane review (69 studies, 30,020 participants) demonstrate probably little or no difference in mortality between crystalloids and any type of colloid (starches, dextrans, gelatins, or albumin) 3

• Synthetic colloids cause harm: Hydroxyethyl starches (HES) are explicitly contraindicated in sepsis and septic shock due to increased mortality (51% vs 43%, p=0.03) and acute renal failure demonstrated in the VISEP and 6S trials 2

• Starches increase need for renal replacement therapy (RR 1.30,95% CI 1.14 to 1.48) and blood transfusions (RR 1.19,95% CI 1.02 to 1.39) 3

When to Consider Colloids (Second-Line Only)

Colloids may be considered only in specific rescue situations:

• Albumin as second-line therapy when patients require substantial amounts of crystalloids and demonstrate refractory shock despite adequate crystalloid resuscitation 1, 2

• The volume ratio needed is approximately 1.5:1 crystalloid to colloid to achieve similar hemodynamic endpoints 1

• Never use synthetic colloids (HES or gelatins) in septic patients due to increased mortality and renal complications 2

Specific Fluid Type Recommendations

• Balanced/buffered crystalloids are preferred over normal saline to reduce the risk of hyperchloremic metabolic acidosis and adverse renal events 4, 1

• The Surviving Sepsis Campaign (2020) recommends using buffered/balanced crystalloids over unbalanced crystalloids for acute resuscitation in shock 4

• Normal saline should be avoided as it increases risk of renal dysfunction compared to balanced solutions 1

Common Pitfalls to Avoid

• Do not rely on traditional teaching favoring colloids without considering current evidence showing no mortality benefit and increased harm 1

• Avoid using HES solutions entirely - they are contraindicated by the European Medicines Agency for volume resuscitation, particularly in sepsis 2

• Do not use albumin as first-line therapy - it is probably not recommended for initial sepsis resuscitation (GRADE 2-) and provides no mortality benefit over crystalloids 2

• Monitor for fluid overload - excessive crystalloid administration can lead to volume overload, respiratory failure, and complications; stop fluid administration when perfusion normalizes or signs of overload develop 1, 2

Clinical Algorithm

1. Initial resuscitation: Administer 10-30 ml/kg of balanced isotonic crystalloid (Ringer's Lactate or Ringer's Acetate) 1, 2

2. Reassess hemodynamics: Monitor capillary refill, skin perfusion, mental status, blood pressure, and urine output 1, 2

3. If shock persists after adequate crystalloid: Consider albumin only as rescue therapy when crystalloid requirements become excessive 1, 2

4. Never use: HES solutions, gelatins, or dextrans in critically ill or septic patients 4, 2

5. If requiring vasopressors: Add norepinephrine targeting MAP ≥60-65 mmHg rather than administering more fluid 4

The evidence is clear and consistent across multiple high-quality guidelines: crystalloids are safer, equally effective for mortality outcomes, and significantly less expensive than colloids for initial fluid resuscitation in critically ill adults.