Max correction 10mEq/L in first 24hr (8 mmol/l during every 24 h thereafter), until a serum sodium concentration of 130 mmol/l is reached (lowers risk of osmotic demyelination syndrome) 
Calculate total body water
TBW(kg) = Wt(kg) x 0.6 = [Wt(lb) x 0.45] x 0.6 = Wt(lb) x 0.27
Calculate mEq deficit
(Desired Na - Measured Na) ~ must be ≤ 10
Calculate NS rate to be given over 24hr
NS rate (cc/hr) = TBW x mEq deficit x 0.27
If using 3% sodium chloride (to avoid volume overload) divide above rate by 3.33
Hyponatremia
Thiazide diuretic use
Hypernatremia
Na-wasting nephropathy 
Hypercapnia
Osmotic diuresis 
Hypermagnesemia
Aldosterone deficiency