What is the recommended fluid resuscitation strategy in critical care?

Fluid Resuscitation Strategies in Critical Care

Primary Recommendation

Crystalloids are the first-line fluid for resuscitation in critically ill patients, with balanced crystalloids (such as Ringer's lactate or Plasmalyte) preferred over 0.9% normal saline to reduce adverse renal events and mortality. 1

Type of Fluid: Crystalloids vs Colloids

Crystalloids as First-Line Therapy

• Crystalloids should be used as the initial resuscitation fluid in all critically ill patients including those with sepsis, septic shock, and hemorrhagic shock 1
• Current evidence demonstrates no mortality benefit with colloids compared to crystalloids at 28 days, making routine colloid use unjustified given their significantly higher cost (albumin costs approximately 140 Euro/L, hydroxyethyl starch 25 Euro/L, versus isotonic saline 1.5 Euro/L) 1, 2, 3
• Colloids require less volume for equivalent intravascular expansion (ratio of approximately 1.5:1), but this does not translate to improved clinical outcomes 1

When to Consider Colloids

• Albumin may be considered as second-line therapy only in patients with refractory septic shock requiring large volumes of crystalloids or those not responding adequately to crystalloid resuscitation 1, 2
• In hemorrhagic shock specifically, albumin has not demonstrated benefit and is not recommended as routine therapy 1
• Hydroxyethyl starches should be avoided entirely due to increased risk of acute kidney injury (RR 1.30), need for renal replacement therapy, coagulopathy, and increased transfusion requirements 1, 4, 3

Choice of Crystalloid: Balanced vs Normal Saline

Balanced Crystalloids Preferred

• Balanced crystalloids (Ringer's lactate or Plasmalyte) should be used preferentially over 0.9% normal saline to reduce the composite outcome of death, acute kidney injury, or need for renal replacement therapy 1, 2
• The SMART study (15,802 ICU patients) demonstrated reduced major adverse kidney events (MAKE-30) with balanced crystalloids versus normal saline 1
• This benefit is particularly important when large volumes are administered (>5000 mL), as occurs in hemorrhagic shock and severe sepsis, where hyperchloremic metabolic acidosis from normal saline increases mortality 1

Exception for Initial Isotonic Saline

• Despite the preference for balanced crystalloids, isotonic saline (0.9% NaCl) remains acceptable as the initial fluid of choice for immediate resuscitation in hypovolemia, with transition to balanced crystalloids for ongoing resuscitation 5, 2

Volume and Rate of Administration

Sepsis and Septic Shock

• Administer at least 30 mL/kg of crystalloid within the first 3 hours for patients with sepsis or septic shock 5, 2
• Initial fluid boluses should be 250-1000 mL administered rapidly, with reassessment after each bolus 1, 2
• Typical 24-hour requirements may reach 4-10 liters in severe cases 1

Hemorrhagic Shock

• Use 20 mL/kg boluses administered over 5-10 minutes, with reassessment for improved perfusion or signs of fluid overload after each bolus 1
• Large volumes are often required (regularly exceeding 5000-10,000 mL in the first 24 hours for trauma) 1

Pediatric Populations

• Initial fluid volume of 10-20 mL/kg of isotonic saline with repeated doses based on clinical response 5
• Pediatric advanced life support guidelines support up to 60 mL/kg for hypovolemic and septic shock 5
• Rapid fluid resuscitation exceeding 40 mL/kg in the first hour has been associated with improved survival in pediatric septic shock 5

Assessment of Response and Resuscitation Targets

Clinical Endpoints

• Reassess hemodynamic status after each fluid bolus using the following parameters 1, 5, 2:
  • Heart rate and blood pressure normalization
  • Improved capillary refill time (target <3 seconds)
  • Skin temperature improvement and decreased mottling
  • Improved mental status
  • Urine output >0.5 mL/kg/hr
  • Serum lactate reduction (aim for 20% decrease if elevated)

Dynamic vs Static Measures

• Use dynamic measures of fluid responsiveness rather than static measures like central venous pressure (CVP) alone, which are unreliable for guiding fluid resuscitation 5, 2
• Dynamic measures include passive leg raise testing and cardiac ultrasound assessment in ventilated patients 1
• CVP monitoring should not be used as the sole guide for fluid administration 1, 5

Critical Pitfalls and Caveats

Avoid Fluid Overload

• Discontinue aggressive fluid resuscitation when signs of fluid overload develop: new onset rales, increased work of breathing, hypoxemia from pulmonary edema, or hepatomegaly 1
• Patients with multiple organ failure who are >10% fluid overloaded have worse outcomes than those <10% overloaded 1
• Consider early initiation of continuous renal replacement therapy (CRRT) to prevent fluid overload while allowing continued plasma infusion for coagulopathy correction 1

Special Populations

• In pregnant patients, use a more restrictive initial approach (1-2 L bolus initially) due to lower colloid oncotic pressure and higher risk of pulmonary edema, increasing to 30 mL/kg only for septic shock or inadequate response 5
• In acute brain injury, avoid hypotonic solutions and maintain adequate cerebral perfusion pressure 1

Restrictive vs Aggressive Strategies

• While aggressive early fluid resuscitation improves outcomes in septic shock, avoid excessive fluid administration in uncontrolled hemorrhage, as it may increase bleeding by elevating blood pressure, dislodging clots, and diluting coagulation factors 1, 6
• In hemorrhagic shock, hypotensive resuscitation strategies (permissive hypotension) may be appropriate until surgical control of bleeding is achieved 1, 6

Monitoring and Adjustment

• After initial resuscitation, implement fluid removal strategies (diuretics or dialysis) if oliguria develops despite adequate resuscitation, as this approach has been associated with improved outcomes 1
• Continue fluid administration only as long as hemodynamic improvement is demonstrated with each bolus 5, 2