Equations

Anthropometrics

Body mass index

BMI = Wt(kg) / Ht (m)2

Body surface area

Adults (age > 11 years)

BSA = 0.007184 x  (Ht(cm) ^ 0.725)  x  (Wt(kg) ^ 0.425)

Peds

BSA = 0.024265 x  (Ht(cm) ^ 0.3964)  x  (Wt(kg) ^ 0.5378)

Ideal body weight

Adults (age > 11 years)

IBW = 45.5 + (2.3 x  (Ht(in) - 60))

If male then add 4.5 to above

Peds

IBW = (Ht(cm)2  x  1.76) / 1000

Modified body weight

If Actual weight is greater than 125% of IBW then

MBW = IBW + 0.2 x (ABW - IBW)

If Actual weight is less than 80% of IBW then

MBW = IBW + 0.2 x (IBW - ABW)

Otherwise MBW = ABW

Mid arm muscle circumference

MAMC = MAC -  (0.314 x  TSF)

Monitoring parameters

Nitrogen balance

N Bal = N in - N out

where

N in = Protein intake (g/d) / 6.25

N out = UUN + 4

Creatinine clearance

Adults (age > 11 years)

CrCl = (140 - Age) x Wt(kg) / (Cr * 72)

If Female multiply above by 0.85

Peds    

CrCl = (Ht * 0.55) / Cr

Corrected calcium

Corrected Ca = Ca + (0.8  x   (4 - Albumin)

Plasma osmolality

Plasma osmol = (2  x  Na) + (Glucose / 18) + (BUN / 2.8)

Bicarbonate deficit

Bicarb def  = (24 - Bicarb) x  Wt(kg) x   0.5

Fluid deficit

Fluid deficit = (1 - (140 / Na)) x  Wt(kg)  x  0.6

Sodium deficit

Sodium deficit  = (140 - Na)  x  Wt(kg)  x   0.6

Nutritional needs assessment

Basal energy expenditure

Adults (age > 11 years)

Male

BEE = 66 + (13.7 x  Weight) + (5 x  Height) - (6.8  x   Age)

Female

BEE = 665 + (9.6  x  Weight) + (1.7  x  Height) - (4.7  x   Age)

Age 3 to 11 years  

Male

BEE = (22.7 x  Weight) + 495

Female

BEE = (22.5  x  Weight) + 499

Age 1 to 2

Male

BEE = (60.9  x  Weight) - 54

Female

BEE = (61  x   Weight) - 51

Estimated energy expenditure

EEE = BEE x Stress/activity factor

Fluid requirements

Fluid req = 1 to 1.5ml per Kcal

Protein requirements

Adults (age  > 11 years)

Protein req = Weight  x  (1.2 + (Activity  x   0.2))

Age 7 to 11 years

Protein req = Weight  x   (1 + (Activity  x   0.2))

Age 4 to  6 years

Protein req = Weight  x   (1.1 + (Activity  x   0.2))

Age 1 to 3 years

Protein req = Weight  x   (1.2 + (Activity  x   0.2))

TPN evaluation parameters

Calcium:Phosphate solubility product

Ca:PO4 product = Ca(meq)  x  PO4(meq)

Osmolarity per liter

1.  Amino acid contribution

AA mOsmol = 100 mOsmol/final %

2.  Dextrose contribution

Dextrose mOsmol = 50 mOsmol/final %

3.  Lipid contribution

Lipid mOsmol = 1.7 mOsmol/g

4.  Electrolyte contribution

Total mEq of each constituent cation and anion

1 mOsmol = 1 mEq

5.  Add all contributions and divide by volume/1000

Osmolarity per liter = (AA mOsmol + Dext mOsmol + Lipid mOsmol + Lyte mOsmol)  /  (Total volume / 1000)

Nitrogen:Calorie ratio

N:C ratio = Kcal/day / (Protein(g/day)  /  6.25)