What are the guidelines for IV fluid therapy bolus vs infusion in patients requiring rapid volume expansion or maintenance fluids?

IV Fluid Therapy: Bolus vs Infusion Strategy

For patients requiring rapid volume expansion (shock, sepsis, severe dehydration), administer crystalloid fluid as repeated rapid boluses of 250-1000 mL (adults) or 20 mL/kg (pediatrics) with mandatory reassessment after each bolus, rather than continuous infusion, to optimize hemodynamic response while minimizing fluid overload risk. 1

Initial Resuscitation Strategy

Adult Patients with Shock/Sepsis

Bolus administration is the preferred approach for acute resuscitation:

• Administer an initial 30 mL/kg of balanced crystalloid (Plasmalyte, Ringer's Lactate) within the first 3 hours as repeated boluses of 250-1000 mL 1, 2
• Each bolus should be given rapidly (within 5-15 minutes) followed by immediate clinical reassessment 1, 2
• Continue bolus administration as long as hemodynamic parameters improve with each dose 1
• More aggressive resuscitation may require >4L in the first 24 hours for adequate tissue perfusion 1

Physiologic rationale: Rapid crystalloid bolus achieves peak intravascular volume expansion of 630 mL immediately after infusion of 1000 mL, though this expansion is transient 3. The bolus approach allows for dynamic assessment of fluid responsiveness before committing to additional volume 1.

Pediatric Patients

Bolus strategy differs significantly by clinical context:

• In resource-rich settings with severe dehydration/shock: Administer 20 mL/kg boluses of isotonic crystalloid within 5 minutes when possible, with reassessment after each bolus 4, 1
• Maximum resuscitation volume: Up to 60 mL/kg can be administered in the first hour, divided into 20 mL/kg boluses with mandatory reassessment after each 4
• Critical warning for resource-limited settings: A large trial (N=3,141) in children with febrile illness and hypoperfusion found excess mortality with both albumin bolus (RR 1.45) and saline bolus (RR 1.44) compared to no bolus strategy 5, 1

Maintenance Fluid Administration

Continuous infusion is appropriate for maintenance therapy, not acute resuscitation:

• For pediatric patients <34 kg: Calculate maintenance using Holliday-Segar formula (100 mL/kg/day for first 10 kg + 50 mL/kg/day for next 10 kg + 25 mL/kg/day above 20 kg) and administer as continuous infusion 4
• Use isotonic solutions (0.9% NaCl or Ringer's Lactate) to prevent iatrogenic hyponatremia 4

Mandatory Reassessment Criteria

After every bolus, evaluate for positive response indicators:

• ≥10% increase in systolic or mean arterial pressure 1
• ≥10% reduction in heart rate 1
• Improved mental status and peripheral perfusion 1
• Increased urine output (target >0.5 mL/kg/h) 1, 2
• Lactate clearance 1

Stop fluid administration immediately if:

• No improvement in tissue perfusion occurs despite volume loading 1
• Pulmonary crackles develop 4, 1
• Progressive peripheral edema or respiratory distress worsens 4
• Jugular venous distension appears 4

Fluid Type Selection

Crystalloids vs Colloids

Balanced crystalloids are preferred over normal saline for initial resuscitation:

• Balanced solutions (Plasmalyte, Ringer's Lactate) reduce risk of hyperchloremic metabolic acidosis and may decrease acute kidney injury incidence 1, 2
• Normal saline (0.9% NaCl) is associated with worse acid-base balance and potentially increased mortality when used in high volumes (>5000 mL) 5

Colloids have limited role in most resuscitation scenarios:

• Albumin shows no mortality benefit over crystalloids in adult critical care 5
• Hypertonic saline (3% or 7.5%) is NOT recommended for hemorrhagic shock resuscitation (GRADE 1- recommendation) as meta-analyses show no mortality benefit 5
• Hetastarch achieves greater peak intravascular expansion (1123 mL vs 630 mL for 1000 mL infused) but lacks outcome benefits 3

Special Consideration for Hemorrhagic Shock

Balanced crystalloids are preferred pending definitive studies:

• Present data insufficient for GRADE 1 recommendation of specific crystalloid type 5
• However, potentially deleterious effects of high-volume chloride-rich solutions on renal function should orient first-line treatment toward balanced solutions 5
• Perioperative use of balanced solutions associated with lower blood transfusion requirements in some studies 5

High-Risk Populations Requiring Modified Approach

Cardiac or Renal Disease

Use smaller initial boluses with heightened vigilance:

• Start with 500 mL boluses rather than 1000 mL 1
• Consider earlier vasopressor initiation 1
• Monitor closely for pulmonary edema 1

Acute Pancreatitis

Aggressive bolus strategy may cause harm:

• Aggressive hydration (20 mL/kg bolus then 3 mL/kg/hr) vs non-aggressive (10 mL/kg bolus then 1.5 mL/kg/hr) showed increased sepsis risk (RR 1.44) 5
• In severe acute pancreatitis, aggressive hydration associated with greater APACHE II score increases (MD 3.31) 5
• Fluid-related complications more common with aggressive approach 5

Contrast-Induced Acute Kidney Injury Prevention

Modified bolus/infusion hybrid approach:

• Administer 3 mL/kg of isotonic sodium bicarbonate over 60 minutes pre-procedure, then 1 mL/kg/hr for 6 hours post-procedure 5
• Target urinary flow rate >150 mL/h for 6 hours post-procedure 5
• This represents a situation where continuous infusion rate is specified rather than bolus strategy 5

Critical Pitfalls to Avoid

Delayed resuscitation is the most critical error:

• Immediate fluid administration upon recognizing tissue hypoperfusion significantly impacts mortality 1
• Do not delay bolus administration while obtaining additional monitoring 1

Relying on static measures:

• Central venous pressure (CVP) has poor predictive ability for fluid responsiveness and should not guide therapy 1
• Use dynamic measures (stroke volume variation, pulse pressure variation) when available 2

Continuing aggressive fluids despite lack of response:

• Failure to reassess after each bolus prevents appropriate titration 1
• Persistent fluid administration without hemodynamic improvement causes pulmonary edema, tissue edema, and abdominal compartment syndrome 1

Never exceed 60 mL/kg/day of crystalloids in pediatric resuscitation:

• Higher volumes associated with worse outcomes 4