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Intraoperative fluid dosing in adult patients
Maintenance rate, NPO deficit and third-space replacement for intraoperative fluids.
Intraoperative fluid dosing in adult patients
Weight
Hours NPO before surgery
hours
Case duration
hours
Surgical trauma (third-space loss)
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When to use
- Estimating an intraoperative crystalloid infusion plan combining maintenance needs, preoperative fasting deficit, and ongoing surgical (third-space) losses.
Formula
Maintenance (Holliday-Segar, 4-2-1 rule): 4 mL/kg/hr for first 10 kg + 2 mL/kg/hr for next 10 kg + 1 mL/kg/hr thereafter. NPO deficit = maintenance rate x hours NPO, replaced 50% in hour 1 and 25% in each of the next 2 hours. Third-space loss added per hour by surgical trauma category.
Pearls and pitfalls
- The classic third-space/fixed-deficit model is a teaching simplification; many modern goal-directed protocols use more restrictive, individualised replacement.
- Reassess against urine output, haemodynamics and blood loss rather than the formula alone.