This document outlines the steps to calculate sodium correction for hypo- and hypernatremia. For hyponatremia, it describes how to determine: 1) the change in serum sodium per liter of infusate, 2) the volume required, 3) the time required for correction, and 4) the infusion rate. For hypernatremia, the same steps are followed to calculate water deficit and rate of correction using free water. An example for each is provided to demonstrate the full calculation.

1. SODIUM CORRECTION FORMULA
DR. RAVIKIRAN H M
HYPONATREMIA
STEPS:
1. Change in S. Na+
with 1lt infusate (Adrogus-Madias equation) in meq/lit
=
𝐼𝑛𝑓𝑢𝑠𝑎𝑡𝑒 𝑁𝑎 − 𝑆𝑒𝑟𝑢𝑚 𝑁𝑎
𝑇𝐵𝑊 + 1
2. Volume required in lit
=
𝐷𝑒𝑠𝑖𝑟𝑒𝑑 𝑆𝑒𝑟𝑢𝑚 𝑁𝑎 − 𝑠𝑒𝑟𝑢𝑚 𝑁𝑎
𝐶𝑕𝑎𝑛𝑔𝑒 𝑖𝑛 𝑠𝑒𝑟𝑢𝑚 𝑛𝑎 𝑤𝑖𝑡𝑕 1𝑙𝑖𝑡 𝑖𝑛𝑓𝑢𝑠𝑎𝑡𝑒
=
140 − 𝑠𝑒𝑟𝑢𝑚 𝑁𝑎
𝐶𝑕𝑎𝑛𝑔𝑒 𝑖𝑛 𝑠𝑒𝑟𝑢𝑚 𝑛𝑎 𝑤𝑖𝑡𝑕 1𝑙𝑖𝑡 𝑖𝑛𝑓𝑢𝑠𝑎𝑡𝑒
3. Time required in hrs
=
𝐷𝑒𝑠𝑖𝑟𝑒𝑑 𝑆𝑒𝑟𝑢𝑚 𝑁𝑎 − 𝑠𝑒𝑟𝑢𝑚 𝑁𝑎
𝑟𝑎𝑡𝑒 𝑜𝑓 𝑐𝑜𝑟𝑟𝑒𝑐𝑡𝑖𝑜𝑛
=
140 − 𝑠𝑒𝑟𝑢𝑚 𝑁𝑎
𝑟𝑎𝑡𝑒 𝑜𝑓 𝑐𝑜𝑟𝑟𝑒𝑐𝑡𝑖𝑜𝑛
4. Run rate in ml/hr
=
𝑣𝑜𝑙𝑢𝑚𝑒 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑
𝑡𝑖𝑚𝑒 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑
Note:
FLUID Na+
in meq/lit
3% NS 513
0.9% NS 154
RL 130
0.45% NS 77
5D 0
Total body water (TBW) =0.6xBW in men

2. =0.5xBW in women
Na+
deficit=0.6xBWx[140-Na+
]
H2O deficit=0.6xBWx[
𝑁𝑎−140
140
]
Example:
70kg Male, Serum Na+
110, rate of correction 1meq/hr, using 3% NS
1. Change in S Na
=
513 − 110
0.6𝑥70 + 1
=
403
43
= 9.37𝑚𝑒𝑞/𝑙𝑖𝑡
2. Volume
=
140 − 110
9.37
=
30
9.37
= 3.2𝑙𝑖𝑡
3. Time
=
140 − 110
1
= 30𝑕𝑟
4. Run rate
=
3200
30
= 106𝑚𝑙/𝑕𝑟
Thus correction is: 3%NS at 106ml/hr for 30hrs.

3. HYPERNATREMIA
Example:
70kg male, serum Na 160, rate of correction 0.5meq/hr, using 5D
First method:
Change in Serum Na
=
0 − 160
0.6𝑥70 + 1
=
−160
43
= −3.72𝑚𝑒𝑞/𝑙𝑖𝑡
Volume required
=
140 − 160
−3.72
=
−20
−3.72
= 5.37𝑙𝑖𝑡
Time required
=
140 − 160
0.5
=
20
0.5
= 40𝑕𝑟𝑠
Run rate
Two methods
same steps as hyponatremia H2O deficit formula

4. =
5370
40
= 134𝑚𝑙/𝑕𝑟
Thus rate of correction is 5D at 134ml/hr for 40hrs.
H2O deficit method
= 0.6 × 70(
160 − 140
140
) = 6𝑙𝑖𝑡
So 6lit over 48hrs
=
6000
48
= 125𝑚𝑙/𝑕𝑟