Body Water Deficit
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Sodium (mmol/L)
Weight
unit kg lb
R e s u l t s
Body Water Deficit in L
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Body Water Deficit

Water deficit (with or without Na+ loss) and Na+ gain is the most common cause of hypernatremia

Water deficit should be corrected over a period of 48-72 hrs with the aim to bring sodium to 145 mEq/L

Formula:

Body Water Deficit (in liters)= 0.6 * Wt * [(Na/140) - 1]

Where,

  • Wt=current weight in kg
  • Na=measured serum Na in mEq/L

Assumes Total Body Water is 60% of current body weight; may be less in female or cachectic patients

Expanded formula: Deficit= Desired TBW - Current TBW=

[(Na*0.6*Wt)/Normal serum Na] - (0.6*Wt)

Reference:

  1. Adrogué HJ, Madias NE. Hypernatremia. N Engl J Med. 2000;342(20):1493-9.
  2. Agrawal V, Agarwal M, Joshi SR, et al. Hyponatremia and hypernatremia: disorders of water balance. J Assoc Physicians India. 2008;56:956-64.