Peds Dosing & Airway

CRNA Study Suite · Weight-based doses, ETT/LMA sizing, fluids, blood
All Calculators Pediatric Quick-Reference Peds Dosing
Patient
Optional Extras
Quick Values
Weight
--
kg
ETT Size
--
mm ID
ETT Depth at Lip
--
cm
LMA Size
--
by weight
Blade
--
laryngoscope
Maintenance
--
mL/hr (4:2:1)
Airway
1. Endotracheal Tube
Size = (16 + age) / 4 = ID. Subtract 0.5 for a cuffed tube. Check for leak at 20 cm H2O.
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AgeInternal Diameter (mm)
Premie2.0 - 3.0 uncuffed
Infant (<1 yr)3.0 - 3.5 cuffed
1 - 2 yr3.5 - 4.0
3 - 4 yr4.5
5 - 8 yr5.0
9 - 11 yr5.5
≥12 yr6.0 and above
2. Insertion Depth
12 + (age / 2) = cm at the lip. Small babies by weight: kg + 6 (1 kg = 7 cm, 2 kg = 8 cm, 3 kg = 9 cm, 4 kg = 10 cm). Newborn to 6 mo = 11 cm, 1 - 2 yr = 12 cm.
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Depth = -- cm at the lip
3. LMA Size (by weight)
WeightLMA Size
<5 kg1
5 - 10 kg1.5
10 - 20 kg2
20 - 30 kg2.5
30 - 50 kg3
50 - 70 kg4
>70 kg5
4. Blade, Cuff, Bag
AgeBlade
PremieMiller 00 - 0
NewbornMiller 0
1 - 12 moMiller 1 / Wis 1
1 - 3 yrWis 1.5
>4 yrMiller 2
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5. Thyromental Distance
Straight-line distance from the prominence of the thyroid cartilage to the bony point of the lower mandibular border, measured with the neck fully extended and the mouth closed. It estimates the mandibular space available to displace the tongue during laryngoscopy.
Normal (adult): at least 6 - 7 cm, about three adult fingerbreadths.
Less than 6 - 7 cm predicts difficult laryngoscopy; Chestnut uses <6 cm as the cutoff for increased airway risk.
No validated pediatric cutoff exists. In infants and small children, assess the submental/mandibular space qualitatively: it is small, the larynx sits anterior, and gentle hand position during mask ventilation matters because pressure on the submental space easily obstructs the airway.
(Sheets, 2023, p. 344; Reale, 2026, p. 687; Miller & Elisha, 2023, p. 1212)
Drug Doses
Fluids & Blood
Maintenance Fluid (4:2:1 Rule)
First 10 kg = 4 mL/kg/hr, second 10 kg = 2 mL/kg/hr, then 1 mL/kg/hr >20 kg. Fluid deficit = NPO hours x maintenance. All patients <2 yr get a buretrol on the IV.
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Estimated Blood Volume & Allowable Blood Loss
ABL = EBV x (initial Hct - lowest acceptable Hct) / initial Hct
AgeEBV
Preterm95 cc/kg
Newborn85 cc/kg
1 - 3 yr80 cc/kg
3 - 6 yr75 cc/kg
>6 yr70 cc/kg
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Blood Products
--
Sponges soaked: 4x4 holds ~10 mL, ray-tech ~10 - 20 mL, lap sponge ~100 mL of blood.
Reference Tables
Normal Vital Signs
AgeHRSBPDBP
Preterm120 - 18045 - 6030
Term100 - 18055 - 7040
1 yr100 - 14070 - 10060
3 yr85 - 11575 - 11070
5 yr80 - 10080 - 12070
NPO Guidelines (all ages)
IntakeHours
Clear liquids2
Breast milk4
Infant formula / non-human milk / light meal6
Solids, fried or fatty foods8
Clear liquids: water, pulp-free juice, carbonated drinks, clear tea, black coffee. Light meal: dry toast and a clear liquid.
Syringe Dilutions (10 mL)
Epinephrine 10 mcg/mL
Target: 100 mcg in a 10 mL syringe = 10 mcg/mL, so 1 mcg per 0.1 mL.
From a 1 mg/mL (1:1,000) ampule, two steps:
1. Draw 1 mL (1 mg) + 9 mL NS in a 10 mL syringe = 100 mcg/mL (1:10,000).
2. Waste 9 mL, keep 1 mL (100 mcg), then draw 9 mL NS = 10 mcg/mL.

From a 1:10,000 code syringe (100 mcg/mL), one step: draw 1 mL (100 mcg) + 9 mL NS = 10 mcg/mL.
Calculate a patient above to see the dose in mL of this mix.
Fentanyl 10 mcg/mL
Target: 100 mcg in a 10 mL syringe = 10 mcg/mL, so 1 mcg per 0.1 mL.
From a 100 mcg vial (2 mL at 50 mcg/mL): draw the whole vial (2 mL) + 8 mL NS = 100 mcg in 10 mL = 10 mcg/mL.
Calculate a patient above to see the dose in mL of this mix.
Source

Doses and sizing transcribed from a pediatric anesthesia reference card (Akron Children's Hospital, compiled by J. Beris, CRNA, 2014). Thyromental distance values from Sheets, S. A. (2023), in Nurse anesthesia (7th ed., p. 344); Reale, S. C. (2026), in Chestnut's obstetric anesthesia (p. 687); and Miller, A., & Elisha, S. (2023), in Nurse anesthesia (7th ed., p. 1212). For education only. Verify every dose against current guidelines and your institution's protocols before clinical use.

How this works

Weight-based dosing

Every dose on this page is a per-kilogram range multiplied by the patient's weight, with hard caps where they exist (ondansetron 4 mg, ketorolac 15 mg, magnesium 2 g, furosemide 20 mg, and adult doses for antibiotics). If weight is left blank it is estimated as (age x 2) + 9 kg for children 1 year and older.

Airway sizing

ETT internal diameter uses (16 + age) / 4, minus 0.5 mm for a cuffed tube, cross-checked against an age band table. Insertion depth at the lip is 12 + (age / 2) cm, or weight + 6 cm in small babies (1 kg = 7 cm through 4 kg = 10 cm). LMA size is picked from the standard weight bands.