CLINICAL PEARLS WHEN TREATING HYPONATERMIA?1. In patients on diuretics, the fractional excretion of urea can be used to help determine if patient is hypovolemic. FeUrea= (Uurea/Purea)/(UCr/Pcr)
FeUrea <35% suggests prerenal state.
2. Before accusing someone of having SIADH, you must check TSH and adrenal function (ACTH stim).
3. Acute recognition of a chronic problem (chronic hyponatremia) does not require acute treatment.
4. To prevent overly rapid correction of hyponatremia, consider the role for DDAVP (often given as 1-2mcg SC/IV). If you do correct too quickly (want to correct 0.5 mmol/h at the absolute most) also consider giving D5W in addition to DDAVP - see the article below.
5. If volume repletion is required, give fluid that is isotonic to the patient by using a combination of NS and D5W.
6. Attach the foley catheter to the IV (figuratively) - be sure to monitor urine osm and output - and consider calculating a tonicity balance
Extras:
When seeing hyponatremia in the ER:
First rule out acute hyponatremia that needs acute correction.
Recheck the lytes as they were often done a while ago and the patient has possibly received intravenous fluids that may have significantly altered the sodium concentration - especially if the stimulus (often ECF volume depletion) for ADH secretion has been removed. Following the urine output may help to identify this (although recording can be an issue outside of the ICU) as a brisk, dilute diuresis can be bad sign.
An article on DDAVP to prevent rapid correction is posted here.
