Some Important Values-Ideal Body Values

Some Important Values-

Ideal Body Weight, Body Surface Area, Alveolar-Arterial Gradient, Creatinine Clearance

Ideal Body Weight

  • Most healthy infants and children grow in a predictable fashion, following a typical pattern of progression in weight, length, and head circumference.
  • Growth velocity, the change in growth over time, is a more sensitive index of growth than is a single measurement.
  • Term neonates may lose up to 10 percent of their birth weight in the first few days of life and typically regain their birth weight by 10 to 14 days
  • Newborns gain approximately 30 g/day (1 oz/day) until 3 months of age
  • Infants gain approximately 20 g/day (0.67 oz/day) between three and six months of age and approximately 10 g/day between 6 and 12 months
  • Infants double their birth weight by 4 months of age and triple their birth weight by 1 year
  • Children gain 2 kg/year (4.4 lbs/year) between 2 years and puberty
  • (any may be used):
  • 1.men: 50kg + 2.3kg/each inch over 5ft; women: 45.5kg + 2.3kg/each inch over 5ft
  • 2.men: 52kg + 1.9kg/each inch over 5ft; women: 49kg + 1.7/each inch over 5ft
  • 3.men: 56.2kg + 1.41kg/each inch over 5ft; women: 53.1kg + 1.36kg/each inch over 5ft

Height velocity —

  • A period of at least six months is necessary for reliable calculation of height velocity in children older than two years.
  • Average normal length or height velocities are as follows
    • 0 to 6 months — One inch (2.5 cm) per month
    • 7 to 12 months — One-half inch (1.25 cm) per month
    • 12 to 24 months — Usually >4 inches (10 cm) per year
    • 24 to 36 months — 3 inches (8 cm) per year
    • 36 to 48 months — 2.75 inches (7 cm) per year
    • 4 to 10 years — 2 to 2.4 inches (5 to 6 cm) per year

Creatinine Clearance

  • men: CrCl = (140-age) IBW/serum Cr × 72
  • women: CrCl = CrCl (male) × 0.85

Alveolar-Arterial Gradient

  • P (A-a)O2 = (PB-PH2O) FIO2 – (Pa CO2 × 1.2) – PaO2
  • P (A-a)O2 = (760-47) FIO2 – (PaCO2 × 1.2) – Pa O2 (sea level)
  • For room air at sea level: P (A-a)O2 = 150-[PO2 + (PO2 + PCO2/0.8)]
  • Normal A-a gradient < (age/4) + 4

Body Surface Area

  • BSA (m2) = square root of [ht (in) × wt (lb)/3131]
  • osmolarity (calculated) = 2 (Na) + glucose/18 + BUN/2.8 [osmolar gap = <10mOsm/kg]
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