CONSULT ROUNDS

A great case of hyponatremia that is in a patient with CNS disease and leading to a Cerebral Salt Wasting vs SIADH picture. Hard to differentiate both when the patient is already on 3% saline. Usually the volume status can give the clue if seen initially before the treatment is started.

Main topic of discussion was an approach to deal with this via a tonicity balance method.
A nice paper by Dr. Mitch Halperin et al in Intensive Care Medicine in 2001 reviewed this topic with a nice example.
When we treat someone with natremias, we account for mostly either free water excess or free water loss and adjust our rate of fluid choices accordingly. A different approach is of using the simple WHAT IS GOING IN ( salt and water) and WHAT IS COMING OUT( salt and water) and calculate the total net NA excess or loss and free water excess and loss and adjust based on that.
Take a look at that paper: Its titled Tonicity Balance and not electrolyte free water calculations guides therapy for acute changes in natremias. A must read!