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 = (P_B-P_H2O) FI_O2 – (Pa _CO2 × 1.2) – Pa_O2
• P (A-a)_O2 = (760-47) FI_O2 – (Pa_CO2 × 1.2) – Pa _O2 (sea level)
• For room air at sea level: P (A-a)_O2 = 150-[P_O2 + (P_O2 + P_CO2/0.8)]
• 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]