## Pediatric Calculators

Clinical calculators for pediatric medicine

### Blood Pressure Percentile

AAP 2017 Clinical Practice Guideline

Based on normative tables for normal-weight children ages 1-17. Flynn et al., Pediatrics 2017;140(3):e20171904.

Age (years)
Sex
Height (cm)
Systolic BP (mmHg)
Diastolic BP (mmHg)
Definitions: Hypertension & Hypotension (AAP 2017 / Nelson)

Hypertension Classification (AAP 2017)

Category | Ages 1 to <13 years | Ages ≥13 years
--- | --- | ---
Normal | <90th percentile | <120/<80 mmHg
Elevated BP | ≥90th to <95th percentile OR 120/80 mmHg to <95th (whichever lower) | 120-129/<80 mmHg
Stage 1 HTN | ≥95th percentile to <95th + 12 mmHg OR 130/80-139/89 mmHg (whichever lower) | 130/80 to 139/89 mmHg
Stage 2 HTN | ≥95th + 12 mmHg OR ≥140/90 mmHg (whichever lower) | ≥140/90 mmHg

Hypertensive Urgency vs Emergency (Nelson)

- Hypertensive urgency: Severe BP elevation (>95th + 30 mmHg or >180/120) WITHOUT end-organ damage. Requires reduction over 24-48 hours.
- Hypertensive emergency: Severe BP elevation WITH end-organ damage (encephalopathy, heart failure, retinopathy, renal injury). Requires immediate IV therapy with goal reduction of 25% in first 8 hours.

Hypotension (AAP/PALS)

- Definition: Systolic BP below the 5th percentile for age, sex, and height.
- Quick estimate (1-10 years): Hypotension = SBP < 70 + (2 × age in years) mmHg
- Neonates: SBP < gestational age in weeks (term: <60 mmHg)
- Clinical significance: Hypotension in children is a late sign of shock. Tachycardia, poor perfusion, and altered mental status typically precede hypotension.

Sources: Flynn JT et al., Pediatrics 2017;140(3). Nelson Textbook of Pediatrics, 21st ed. PALS Provider Manual.

### BMI Percentile

CDC Growth Charts, ages 2-20

Based on CDC 2000 growth reference data. For children ages 2-20 years.

Age (years)
Sex
Weight (kg)
Height (cm)

### Body Surface Area

Mosteller formula

Mosteller formula: BSA (m2) = sqrt(height(cm) x weight(kg) / 3600)

Weight (kg)
Height (cm)

### Weight-Based Dosing

Calculate dose based on weight. Always verify against formulary and institutional guidelines.

Patient Weight (kg)
Dose (mg/kg)
Frequency
Max single dose (mg, optional)
Concentration (mg/mL, optional)

### Growth Percentiles

WHO growth standards (0-2y) / CDC 2000 (2-20y).

Sex
Age
Gestational Age (weeks)
Weight (kg)
Length/Height (cm)
Head Circumference (cm)
Mid-Parental Height (optional)
Mother's Height (cm)
Father's Height (cm)

### Neonatal Bilirubin

AAP 2022 Clinical Practice Guideline. Determines phototherapy threshold based on gestational age and risk factors.

Neurotoxicity Risk Factors for Phototherapy Threshold (AAP 2022)

Higher Risk (use lower threshold):

- Gestational age 35-37 weeks (with other risk factors)
- Albumin < 3.0 g/dL
- Isoimmune hemolytic disease (ABO, Rh incompatibility)
- G6PD deficiency
- Asphyxia / significant lethargy
- Sepsis
- Acidosis (pH < 7.15)
- Temperature instability / hypothermia

Lower Risk (use higher threshold):

- Gestational age ≥ 38 weeks
- No hemolysis
- Well-appearing infant
- No risk factors above

Source: AAP 2022 Clinical Practice Guideline

Risk Factors for Severe Neonatal Hyperbilirubinemia (Nelson Table 137.1)

Genetic Factors

- Gilbert syndrome
- Crigler-Najjar syndrome
- Alagille syndrome
- β-thalassemia
- Glucose-6-phosphate dehydrogenase (G6PD) deficiency
- Bilirubin glucuronosyltransferase polymorphism
- Pyruvate kinase deficiency
- Erythrocyte structural defects (hereditary spherocytosis, elliptocytosis)
- Galactosemia

Maternal Factors

- Family history of severe jaundice, splenectomy, or cholecystectomy
- Primiparity
- Teenage pregnancy
- Diabetes
- Rhesus incompatibility
- ABO incompatibility
- Other blood group isoimmunization
- Use of drugs during labor (oxytocin, promethazine, bupivacaine)
- Exclusive breastfeeding

Perinatal Factors

- Mode of delivery (breech vs vertex, instrumentation)
- Birth trauma (cephalohematoma, substantial bruising, extravasation)
- Birth asphyxia
- Congenital infections (CMV, syphilis)
- Sepsis

Neonatal Factors

- Male sex
- Prematurity or low birthweight and small-for-gestational age
- Hypothyroidism
- Polycythemia
- Hypoglycemia
- Low intake of breast milk, dehydration, or weight loss
- Breast milk jaundice
- Jaundice in the first day of life
- Trisomy 21
- Infant of diabetic mother
- Cephalohematoma, other bruising

Other Risk Factors and Markers

- Previous sibling received phototherapy or exchange transfusion
- Predischarge TSB or TcB in the high zone
- Use of hemolytic agents (naphthalene, menthol-based products) in G6PD-deficient populations
- Folate deficiency
- Aflatoxins
- Hypothermia
- Birth outside of a healthcare facility

Modified from Olusanya BO, Kaplan M, Hansen TWR. Neonatal hyperbilirubinaemia: a global perspective. Lancet Child Adolesc Health. 2018;2:610-618. Nelson Textbook of Pediatrics, Table 137.1.

Gestational Age (weeks)
Age of Infant (hours)
Total Serum Bilirubin (mg/dL)
Risk Factors

Bhutani hour-specific bilirubin nomogram. Determines risk zone for infants >= 35 weeks GA.

Age of Infant (hours)
Total Serum Bilirubin (mg/dL)

### Normal Vital Signs by Age

Harriet Lane Handbook

Reference ranges for heart rate, respiratory rate, and blood pressure by age. Source: Harriet Lane Handbook.

Age | Heart Rate (bpm) | Respiratory Rate | Systolic BP (mmHg) | Diastolic BP (mmHg) | Weight (kg)
--- | --- | --- | --- | --- | ---
Preterm | 120-170 | 40-70 | 55-75 | 35-45 | 1-2.5
Newborn (0-1mo) | 100-160 | 30-60 | 60-80 | 35-55 | 2.5-4.5
1-6 months | 100-150 | 30-50 | 70-90 | 40-60 | 4-8
6-12 months | 90-140 | 25-40 | 75-95 | 45-65 | 8-10
1-3 years | 80-130 | 20-30 | 80-100 | 50-70 | 10-15
4-5 years | 80-120 | 20-25 | 85-105 | 50-70 | 15-20
6-8 years | 70-115 | 18-25 | 90-110 | 55-75 | 20-27
9-11 years | 70-110 | 16-22 | 95-115 | 58-78 | 27-40
12-15 years | 60-100 | 14-20 | 100-125 | 60-80 | 40-60
16-18 years | 55-95 | 12-18 | 110-130 | 65-85 | 55-75

#### Quick Reference Formulas

Estimated Weight:
1-12mo: (age in mo + 9) / 2
1-5yr: 2 x (age in yr) + 8
6-12yr: 3 x (age in yr) + 7
Min Systolic BP:
1-10yr: 70 + (2 x age in yr)
Hypotension: SBP < 5th %ile
ETT Size:
Uncuffed: (age/4) + 4
Cuffed: (age/4) + 3.5
Depth: ETT size x 3
Maintenance Fluids (4-2-1):
First 10kg: 4 mL/kg/hr
Next 10kg: +2 mL/kg/hr
Each kg above 20: +1 mL/kg/hr