Pediatric fluids, blood and allowable loss
Stem
A 2-year-old girl, 12 kg, is having an open reduction of a dislocated hip with a pelvic osteotomy. She is healthy, her last solid meal was 8 hours ago and her last clear fluid 2 hours ago. Her hematocrit is 36%. The surgeon expects meaningful blood loss. A peripheral IV is in after an inhalational induction.
Question
What are her maintenance fluid rate, blood volume and allowable blood loss, and how will you manage her fluids and blood?
Ideal answer
HeadlineMaintenance 44 mL/h, blood volume about 900 mL, allowable loss about 375 mL; isotonic fluid, then red cells.
- Maintenance by 4-2-1: 44 mL/h. 40 mL/h for the first 10 kg plus 2 mL/kg/h for the next 2 kg;1 a drink 2 hours ago leaves a small deficit.
- Blood volume 75 mL/kg, roughly 900 mL. 70 to 80 mL/kg at this age.2
- Allowable loss: 900 times 15 over 36. Blood volume times the hematocrit fall over the starting hematocrit; 21%, close to the hemoglobin of 7 a stable child over 4 months tolerates.3,2
- Balanced isotonic crystalloid like lactated Ringer's, glucose checked. Never a hypotonic fluid as a bolus.1
- Red cells 10 to 15 mL/kg near the limit. About 120 to 180 mL, after crystalloid or albumin;3 hemoglobin and gas as loss approaches 375 mL.
Breaking down the answer
- Do the arithmetic aloud — examiners want the numbers in seconds and the reasoning behind them; organization and presentation are graded.
- Small child, small margin — 375 mL is a few soaked sponges, so I weigh sponges, measure suction and warm everything. Changes if: under 4 months, neonates, cyanotic heart disease or high oxygen needs, which raise the trigger above a hemoglobin near 7.3
- Why isotonic and balanced — saline brings hyperchloremic acidosis; hypotonic fluid brings hyponatremia when surgery and pain raise ADH; a burette or syringe pump prevents an accidental liter.1
- Glucose by indication — dextrose is routine under a year and with long fasts or risk factors; for a normoglycemic toddler after a short fast, I measure rather than reflexively add it.1
- Postoperative isotonic maintenance — with potassium and dextrose, to avoid hospital-acquired hyponatremia; the AAP gives a strong, grade A recommendation from 28 days to 18 years.4 Changes if: neurosurgical, cardiac, renal or hepatic disease, which the guideline excludes.
Follow-up question
An hour later estimated loss is 420 mL. Heart rate is 165, blood pressure 68/34, and the hematocrit is 20%. The surgeon says another 200 mL is likely. What now?
Follow-up answer
HeadlineHemorrhagic hypovolemia past her allowable loss; I tell the surgeon and ask for pressure on the field while I catch up.
Warmed red cells, 15 mL/kg or about 180 mL, through a warmer by syringe, and an isotonic bolus of 10 to 20 mL/kg if she stays hypotensive while blood arrives.3,1 Blood slowly enough to avoid a potassium load, and calcium for citrate-induced hypocalcemia. A second unit, plus gas, potassium, ionized calcium and coagulation studies. Approaching one blood volume: plasma at 10 to 15 mL/kg and platelets, kept above 50,000 in active bleeding.3 Then heart rate, pressure, gases and the field again.
Pitfalls that cost points
- Forgetting to divide by the starting hematocrit in the allowable-loss formula.
- Using an adult blood volume of 65–70 mL/kg for a neonate.
- Waiting for hypotension, a late sign in children, before transfusing.
Rapid-fire
Q: Blood volume of a preterm neonate? A: About 90 to 100 mL/kg; a term neonate about 80 to 90.2
Q: Platelet threshold? A: Below 50,000 with active bleeding or an invasive procedure, below 100,000 for CNS surgery.3
Q: Maximum maintenance rate in most children? A: About 100 mL/h, the adult cap.1
Q: Bolus for hypovolemia? A: 10 to 20 mL/kg of isotonic crystalloid, then reassess.1
Q: Plasma dose? A: 10 to 15 mL/kg.3
Numbers to know
| Item | Value |
|---|---|
| Maintenance (4-2-1) | 4 mL/kg/h first 10 kg, 2 next 10, 1 after1 |
| Blood volume | Preterm 90–100, term 80–90, infant 70–80, child 70–75 mL/kg2 |
| Allowable loss | EBV × (Hct start − Hct min) ÷ Hct start2 |
| Hemoglobin trigger (>4 months, stable) | ~7 g/dL3 |
| Red cells, plasma, platelets | 10–15 mL/kg each3 |
| Isotonic maintenance | 28 days to 18 years, grade A4 |
Links
- Fluid management: crystalloid, colloid, goal-directed, Massive hemorrhage and transfusion, Hyponatremia and TURP syndrome, Transfusion reactions, TRALI and TACO
- AAP Clinical Practice Guideline: Maintenance Intravenous Fluids in Children (2018)
Sources
- 1.IV Fluid Therapy Clinical Pathway · Nationwide Children's Hospital · nationwidechildrens.org4-2-1 rate, fluid choice, dextrose indications, bolus volumes.
- 2.Maximum Allowable Blood Loss (Iowa Anesthesia Protocols) · University of Iowa · iowaprotocols.medicine.uiowa.eduTable of estimated blood volume by age from several references.
- 3.Management of perioperative bleeding in children (Colombian Journal of Anesthesiology) · Revista Colombiana de Anestesiología · elsevier.esNon-systematic review; transfusion thresholds and component doses.
- 4.Clinical Practice Guideline: Maintenance Intravenous Fluids in Children (Feld et al., Pediatrics 2018;142:e20183083) · AAP, 2018 · umassmed.eduFull-text copy hosted by UMass Chan pediatrics; applies to ages 28 days to 18 years, with listed exclusions.
Facts on this page were checked against these sources on Oct 15, 2026. Guidelines change; confirm doses against current institutional protocols.