What is the appropriate initial fluid resuscitation for a patient with hypovolemic shock?

Initial Fluid Resuscitation for Hypovolemic Shock

Begin immediate resuscitation with isotonic crystalloid (0.9% normal saline or lactated Ringer's solution) administered as rapid boluses: 20 mL/kg over 5-10 minutes in children or 500-1000 mL over 15-30 minutes in adults, repeating up to 60 mL/kg in the first hour for children or 30 mL/kg within 3 hours for adults. 1, 2

Fluid Choice and Initial Bolus Strategy

• Isotonic crystalloids are the first-line resuscitation fluid for hypovolemic shock, with normal saline (0.9% NaCl) and lactated Ringer's solution both acceptable choices 1, 3, 2, 4
• The American Academy of Pediatrics and Dutch Pediatric Society recommend isotonic saline as first choice based on evidence showing no mortality benefit of colloids over crystalloids, while colloids carry additional risks of infection, anaphylaxis, and substantially higher costs 1, 3
• Administer 10-20 mL/kg boluses in neonates and children, or 20 mL/kg boluses in pediatric patients, given rapidly over 5-10 minutes 1, 3, 2
• Administer 500-1000 mL boluses in adults over 15-30 minutes 2
• Reassess immediately after each bolus before administering additional fluid 1, 2

Volume Limits and Escalation

• Children may receive up to 60 mL/kg total in the first hour if perfusion does not normalize and no signs of fluid overload develop 1, 2
• Adults should receive up to 30 mL/kg within the first 3 hours 2
• A maximum total volume of up to 200 mL/kg may be given in children if signs of fluid overload remain absent 2
• When large fluid volumes are required (e.g., severe sepsis), synthetic colloids may be considered after initial crystalloid resuscitation due to longer intravascular duration, though this is a weaker Grade C recommendation 1, 3

Critical Stopping Points: Signs of Fluid Overload

Stop or slow fluid administration immediately if any of the following develop: 1, 2

• Hepatomegaly (enlarged liver on palpation)
• Pulmonary rales or crackles on auscultation
• Gallop rhythm on cardiac auscultation
• Increased work of breathing or respiratory distress
• Decreased oxygen saturation
• Increased jugular venous pressure (in adults)

If hepatomegaly or rales develop, switch to inotropic support rather than continuing fluid resuscitation. 1

Resuscitation Endpoints: When to Stop

Target the following clinical parameters to determine adequate resuscitation: 1, 2

• Capillary refill ≤2 seconds
• Normal heart rate for age
• Warm extremities with strong peripheral pulses equal to central pulses
• Normal mental status or level of consciousness
• Urine output >1 mL/kg/hour in children or >0.5 mL/kg/hour in adults
• Normal blood pressure for age or MAP ≥65 mmHg in adults

Vasopressor Initiation

• Initiate norepinephrine if shock persists after 40-60 mL/kg in children or 30 mL/kg in adults, targeting MAP of 65 mmHg 2
• Norepinephrine is the first-line vasopressor, with epinephrine as an alternative 2
• Begin peripheral inotropic support until central venous access can be obtained in children who are not responsive to fluid resuscitation, as delay in inotrope use is associated with major increases in mortality risk 1

Special Populations and Considerations

Neonates

• Use 10-20 mL/kg boluses of isotonic saline (without dextrose for resuscitation), reassessing after each bolus 3, 2
• Dextrose-containing solutions must not be used for rapid resuscitation boluses 3
• In neonates with severe hemolytic anemia (severe malaria or sickle cell crises) who are not hypotensive, blood transfusion is superior to crystalloid or albumin bolusing 1

Traumatic Brain Injury

• Use isotonic saline exclusively, avoiding hypotonic solutions 2
• Maintain adequate systolic blood pressure for age 2

Burns

• Give 20 mL/kg within the first hour for adults with ≥15% TBSA or children with ≥10% TBSA burns 2
• Use balanced crystalloids such as Ringer's Lactate as first-line treatment 2

Balanced vs. Unbalanced Crystalloids

• Balanced solutions (lactated Ringer's, Plasma-Lyte) offer advantages over normal saline by preventing hyperchloremic metabolic acidosis and may reduce acute kidney injury 3, 4
• Normal saline contains supraphysiologic chloride concentration (154 mmol/L vs. plasma ~100 mmol/L), which can cause hyperchloremic metabolic acidosis with prolonged administration 3
• Evidence for benefits of balanced solutions in patient morbidity and mortality is increasing 4

Critical Pitfalls to Avoid

• Do not use hypotonic fluids (0.45% saline, 0.18% saline, D5W) for shock resuscitation in any age group 3, 2
• Do not rely solely on blood pressure to guide therapy; blood pressure alone is not a reliable endpoint, especially in children who can maintain blood pressure through vasoconstriction until cardiovascular collapse is imminent 1, 2
• Do not continue aggressive fluid without reassessment for overload after each bolus 2
• Do not delay fluid resuscitation waiting for central venous access; use peripheral or intraosseous access and begin therapy immediately 3, 2
• Do not delay vasopressor initiation in fluid-refractory shock beyond 40-60 mL/kg in children or 30 mL/kg in adults 2
• Do not use etomidate for intubation in pediatric patients with septic shock due to associated higher mortality 2

Monitoring During Resuscitation

• Reassess clinical status immediately after each bolus before administering additional fluid 1, 2
• Monitor heart rate, blood pressure, capillary refill time, skin temperature, mental status, and urine output continuously 3, 2
• Use dynamic measures of fluid responsiveness (pulse pressure variation, stroke volume variation) rather than static measures like CVP alone when available 2
• Monitor plasma electrolytes regularly, particularly sodium levels 3
• Urine output <1 mL/kg/hour (without urinary retention or established renal failure) indicates impaired renal perfusion and may guide need for additional resuscitation 3