Body Surface Area Calculation for a Child Weighing 18.85 kg
For a child weighing 18.85 kg, the body surface area (BSA) should be calculated using the Gehan and George equation: BSA (m²) = 0.0235 × (height [cm])^0.42246 × (weight [kg])^0.51456. 1
Recommended Formula and Calculation Method
The Gehan and George equation is the preferred method for calculating BSA in pediatric patients as it:
- Is derived from the greatest number of study subjects 2
- Is recommended by the American College of Pediatricians 1
- Provides more accurate results for pediatric patients 2
Important Considerations for Pediatric BSA Calculation
- Accurate BSA calculation is critical for pediatric patients, especially when dosing medications with narrow therapeutic indices 1
- For pediatric patients receiving peritoneal dialysis, BSA calculations are particularly important for estimating total body water (TBW) 2
- The relationship between BSA and total body water is not linear, which makes accurate calculation essential 2
Alternative Simplified Formula
If height measurements are not available, a simplified formula can be used as an approximation:
- BSA can be estimated as 1/6(WH)^0.5, where W is weight in kg and H is height in m 3
- However, this simplified approach may be less accurate for pediatric patients compared to the Gehan and George equation 1
Clinical Applications of BSA Calculation
BSA calculations are important in multiple clinical scenarios:
- Medication dosing, particularly for chemotherapeutic agents 1
- Estimating total body water in peritoneal dialysis 2
- Normalizing cardiac parameters and volumes 2
- Evaluating coronary artery dimensions in conditions like Kawasaki disease 2
Cautions and Limitations
- BSA calculations may need adjustment in special populations (e.g., amputees, malnourished patients) 2
- For amputees, specific corrections should be made using established tables for weight and BSA adjustments 2
- In malnourished patients, calculations may need to account for desired rather than actual weight 2
Importance in Pediatric Cardiology
- Z-scores based on BSA are used to standardize coronary artery dimensions in children 2
- Different Z-score systems exist, with the most rigorous being those reported for Japanese subjects by Kobayashi and for Canadian subjects by Dallaire 2
- These systems use the Haycock and Du Bois formulas for estimating BSA 2