We hope you all had a great New Year.  With all this rain falling, it's hard not to think of fluid and sodium. One issue that often comes up and is a challenge to deal with is HYPONATREMIA.  Remember that the body's daily sodium requirements are 2-3 mEq/kg/dy.  For a patient to become hyponatremic, they either have taken in excess free water or have lost sodium in excess of free water.  Examples are a baby who takes in formula that has been diluted, SIADH, diuretic therapy, adrenal insufficiency, GI losses, and CF.  The first thing to do in treating the patient is to determine the sodium deficit.

Na deficit: (goal Na- actual Na) x 0.6L/kg x wt. in kg= mEq Na 

Remember also that a patient can actually have normal total body sodium, but have serum hyponatremia on labs.  This can represent PSUEDOHYPONATREMIA.  Elevated serum glucose, lipids, or protein can cause a dilutional effect of the serum sodium.  To correct:

1) Hyperglycemia: Na decreased by 1.6 mEq/L for each 100 mg/dl rise in glucose
2) Hyperlipidemia: Na decreased by 0.002 x lipid (mg/dl)
3) Hyperproteinemia: Na decreased by 0.25 x [(protein (g/dl) - 8]

Clinically, Na </= 120 mEq/L is often symptomatic (seizure, shock, lethargy).  If the change was less acute or chronic over several months, the patient may be relatively asymptomatic.

Treatment depends on etiology.

We hope this helps.  Remember to first think, "Has this patient taken in too much free water, or has this patient been losing too much sodium??"

Chief Resident Pearl, 1/2005