Height
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Height and weight formula in pedia
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I have enough context from the textbooks and my clinical knowledge. Let me now provide a comprehensive answer.
Pediatric Height & Weight Estimation Formulas
These are the standard formulas used in clinical practice for estimating weight and height in children when direct measurement is unavailable (especially during emergencies).
Weight Estimation Formulas
1. APLS (Advanced Pediatric Life Support) Formula — most widely used
| Age | Formula |
|---|---|
| 0–12 months | Weight (kg) = (age in months + 9) ÷ 2 |
| 1–5 years | Weight (kg) = (age in years × 2) + 8 |
| 6–12 years | Weight (kg) = (age in years × 3) + 7 |
2. Nelson's Formula (simplified)
| Age | Formula |
|---|---|
| 3–12 months | Weight (kg) = age (months) + 9 / 2 |
| 1–6 years | Weight (kg) = age (years) × 2 + 8 |
| 7–12 years | Weight (kg) = age (years) × 7 − 5 / 2 |
3. PALS / Basic Formula
- 1–10 years: Weight (kg) = age (years) × 2 + 10 (used in many PALS algorithms)
4. Mid-Arm Circumference Formula (school-age children)
Weight (kg) = (mid-arm circumference [cm] − 10) × 3
- Validated as reliable for school-age children; an alternative to the Broselow tape
- — Tintinalli's Emergency Medicine, p. 2036
5. Broselow Tape (Length-Based System)
- Uses the child's measured length to estimate weight and guide drug dosing/equipment selection
- Color-coded; incorporated in AHA PALS
- Note: Inaccurate in ~1/3 of children (may over- or underestimate); less reliable in obese or underweight populations
- — Tintinalli's Emergency Medicine, p. 725
Height (Length) Estimation Formulas
| Age | Formula |
|---|---|
| Birth | ~50 cm |
| 1 year | ~75 cm |
| 2–12 years | Height (cm) = age (years) × 6 + 77 |
| Alternate (2+ years) | Height (cm) = age (years) × 5 + 80 |
Mid-parental height (genetic potential):
- Boys: (Father's height + Mother's height + 13) ÷ 2
- Girls: (Father's height + Mother's height − 13) ÷ 2 (values in cm; use +5 and −5 for inches)
Quick Reference Summary
| Parameter | Formula |
|---|---|
| Weight 1–5 y | Age × 2 + 8 kg |
| Weight 6–12 y | Age × 3 + 7 kg |
| Height 2–12 y | Age × 6 + 77 cm |
| ETT size (uncuffed) | Age/4 + 4 |
| ETT size (cuffed) | Age/4 + 3.5 |
Clinical note: These are estimates only. Whenever possible, use an actual scale. The Broselow tape remains the standard length-based tool in pediatric resuscitation settings despite its limitations in overweight or underweight populations. Parental estimation of weight has also been shown to be more accurate than formula-based methods in some studies (Tintinalli's Emergency Medicine).
Height and weight formulas in pedia acc to age
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Here is a complete breakdown of pediatric height and weight estimation formulas organized by age, sourced directly from Tintinalli's Emergency Medicine.
Pediatric Weight Estimation Formulas by Age
Named Formulas (Table 109-4)
| Formula Name | Age Group | Formula |
|---|---|---|
| APLS | Infants | (age in months × 0.5) + 4 |
| 1–5 years | (age in years × 2) + 8 | |
| 6–12 years | (age in years × 3) + 7 | |
| Nelson | < 12 months | (months + 9) ÷ 2 |
| 1–6 years | (years × 2) + 8 | |
| 7–12 years | (years × 7) − 5 | |
| Best Guess | < 12 months | (months + 9) ÷ 2 |
| 1–4 years | (years + 5) × 2 | |
| 5–14 years | years × 4 | |
| Luscombe | All children | (years × 3) + 7 |
| Argall | All children | (years + 2) × 3 |
Reference Weights by Age (Table 109-5)
| Age | Weight (kg) | Landmark |
|---|---|---|
| Term newborn | 3.5 | Birth weight |
| 6 months | 7 | 2× birth weight |
| 1 year | 10 | 3× birth weight |
| 4 years | 16 | ¼ of adult weight (70 kg) |
| 10 years | 35 | ½ of adult weight |
Mid-Arm Circumference Formula (school-age)
Weight (kg) = (mid-arm circumference [cm] − 10) × 3
Useful when length measurement is difficult; reliable for school-age children.
Pediatric Height (Length) Estimation by Age
| Age | Expected Height |
|---|---|
| Birth | ~50 cm |
| 1 year | ~75 cm (gains ~25 cm in 1st year) |
| 2 years | ~85–87 cm |
| 2–12 years | Height (cm) = (age in years × 6) + 77 |
| Alternate | Height (cm) = (age in years × 5) + 80 |
Doubling rule:
- Height at 2 years ≈ 50% of adult height
Quick Summary by Age Group
| Age Group | Weight Formula | Expected Height |
|---|---|---|
| 0–12 months | (months + 9) ÷ 2 | 50 cm → 75 cm |
| 1–5 years | (years × 2) + 8 | Age × 6 + 77 cm |
| 6–12 years | (years × 3) + 7 | Age × 6 + 77 cm |
Clinical note: These are estimates only and may be less accurate in obese or underweight children. The Broselow tape (length-based) remains the preferred tool for weight estimation during pediatric resuscitation. Parental report of weight is often equally reliable or better than formula-based estimates.
— Tintinalli's Emergency Medicine, Tables 109-4 and 109-5
Holiday cigar formula
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You're asking about the Holliday-Segar formula (commonly mispronounced/misspelled as "Holiday CIGAR") — the standard method for calculating pediatric maintenance IV fluid requirements. Here it is in full:
Holliday-Segar Formula
(Maintenance IV Fluid Requirements)
The Rule: 4-2-1
| Body Weight | Rate (mL/kg/hr) | Volume (mL/kg/day) |
|---|---|---|
| First 10 kg | 4 mL/kg/hr | 100 mL/kg/day |
| Second 10 kg | 2 mL/kg/hr | 50 mL/kg/day |
| Each kg above 20 kg | 1 mL/kg/hr | 20 mL/kg/day |
How to Calculate (Worked Example)
25 kg child (8-year-old):
| Segment | Hourly | Daily |
|---|---|---|
| First 10 kg: 4 × 10 | 40 mL/hr | 1000 mL/day |
| Second 10 kg: 2 × 10 | 20 mL/hr | 500 mL/day |
| Remaining 5 kg: 1 × 5 | 5 mL/hr | 100 mL/day |
| Total | 65 mL/hr | 1600 mL/day |
Electrolyte Requirements (per 100 mL water metabolized)
- Sodium (Na⁺): 3 mEq per 100 mL
- Potassium (K⁺): 2 mEq per 100 mL
Current AAP guidelines recommend isotonic fluids (0.9% NaCl or Lactated Ringer's) as maintenance fluid for most hospitalized children — replacing the older practice of using hypotonic ¼ NS.
Important Limitations
- Not for neonates < 14 days old — overestimates fluid needs in newborns
- Maximum recommended rate: 120 mL/hr (in absence of cardiac, hepatic, or renal pathology)
- Adjust downward if concern for fluid overload
— The Harriet Lane Handbook, 23rd ed., Table 11.1 & Box 11.1
Types of fever
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The textbook library didn't have a dedicated "types of fever" section, but here is a comprehensive and clinically accurate breakdown based on established medical knowledge:
Types of Fever (by Pattern)
Fever patterns are described based on how temperature fluctuates over time. Classically, they help narrow the differential diagnosis.
1. Continuous (Sustained) Fever
- Temperature remains elevated throughout the day
- Variation < 1°C, never reaches normal
- Causes: Lobar pneumonia, typhoid fever (classic "step-ladder" then plateau), urinary tract infection, rickettsial infections
2. Remittent Fever
- Temperature fluctuates > 1°C daily but never returns to normal
- Most common fever pattern seen in clinical practice
- Causes: Infective endocarditis, most viral and bacterial infections, brucellosis ("undulant fever")
3. Intermittent Fever
- Temperature spikes then returns to normal in between
- Subtypes based on periodicity:
Subtype Frequency Classic Cause Quotidian Daily spikes P. knowlesi malaria Tertian Every 48 hrs P. vivax, P. ovale malaria Quartan Every 72 hrs P. malariae malaria - Also seen in: pyogenic abscesses, lymphoma
4. Hectic (Septic / Swinging) Fever
- Wide daily swings (> 2–3°C), with dramatic spikes and returns near normal
- Often accompanied by chills and drenching sweats
- Causes: Septicemia, pyogenic abscess, disseminated TB, miliary TB
- In malaria: early infection before synchronization of parasite replication causes irregular hectic fever (Sherris & Ryan's Medical Microbiology)
5. Pel-Ebstein Fever
- Alternating periods of fever (days to weeks) followed by afebrile periods of equal length
- Classic but rare
- Cause: Hodgkin's lymphoma
- "Look for the hectic Pel-Ebstein fever pattern of Hodgkin disease" — Textbook of Family Medicine
6. Relapsing Fever
- Febrile episodes separated by days of normal temperature, then recurrence
- Causes: Borrelia recurrentis (louse-borne), Borrelia hermsii (tick-borne), brucellosis
7. Inverse (Reversed) Fever
- Temperature is higher in the morning than in the evening (opposite of normal diurnal pattern)
- Causes: Miliary TB, gram-negative bacteremia, salicylate toxicity
Classification by Degree (Temperature)
| Grade | Temperature |
|---|---|
| Low-grade | 37.5–38°C (99.5–100.4°F) |
| Moderate | 38–39°C |
| High-grade | 39–40°C |
| Hyperpyrexia | > 41°C (> 105.8°F) — medical emergency |
Classification by Duration
| Type | Duration |
|---|---|
| Acute fever | < 2 weeks |
| Subacute | 2–4 weeks |
| Fever of Unknown Origin (FUO) | > 3 weeks, temp > 38.3°C, no diagnosis after initial workup |
Clinical tip: In modern practice, antibiotic and antipyretic use often obscures classic fever patterns, so they are less diagnostically reliable than historically taught — but still tested and clinically useful.
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