The obese patient
Definitions
- Overweight = BMI 25-29
- Obesity = BMI 30-39
- Morbid obesity = BMI 40-49
- Super obesity = BMI >50
- Total body weight (TBW)= Actual weight
- Ideal body weight (IBW)= Calc. based on height & weight
- Lean body mass (LBM)= Calc. based on subtracting body fat from TBW
Estimating Patient Weight
Multiple formulas to estimate weight, below are most common:
- Estimated male TBW = 93.2 + 3.29[arm circumference (cm)] + 0.43[height (cm)]
- Estimated female TBW = 64.6 + 2.15[arm circumference (cm)] + 0.54[height (cm)]
- Estimated male IBW in kg = height in cm - 100
- More accurate IBW estimate:
- IBW (male) in kg = 50kg + 2.3kg for each in. over 5ft
- More accurate IBW estimate:
- Estimated female IBW in kg = height in cm - 105
- More accurate IBW estimate:
- IBW (female) in kg = 45kg + 2.3kg for each in. over 5ft
- More accurate IBW estimate:
- Estimated LBM = 1.3 x IBW
- Others:
- Epocrates has IBW calculator
- Http://www.medcalc.com/body.html
Medication Adjustments in Obesity
Obesity alters hepatic/renal clearance and volume of distribution (Vd) of many drugs