Formulas

Question 1

Total body water

Answer 1

TBW = wt x 0.5 (Female) or 0.6 (Male)

Question 2

Free water deficit

Answer 2

[(Na+ -140)/140] x TBW

Question 3

Na+ deficit

Answer 3

Na+ deficit = 0.6 x BW (target plasma Na+ conc - starting plasma Na+ conc)

Question 4

Corrected Ca

Answer 4

Corrected Ca = (0.8 * (Normal Albumin - Pt’s Albumin) + S. Ca

unit g/dL

Question 5

Corrected Na for hyperglycemia

Answer 5

Corrected Na = Measured Na+ + [0.024 * (Measured glucose in mg/dL -100)}