6. Giving Isotonic Fluids to Someone Who Has Fixed Water Retention or Hypertonic Urine Can Worsen the Problem
This can stem from an incomplete or incorrect evaluation of hyponatremia, which is a common problem in hospitalized patients. When hyponatremia is present, the first order of business should be to exclude pseudohyponatremia and confirm that it's hypotonic hyponatremia.
After confirmation, the volume status should be assessed. One useful way to do this is to measure urine creatinine, urine sodium, and urine osmolality (osm), Dr. Florez says. If a patient has water retention or hypertonic urine from syndrome of inappropriate diuretic hormone secretion (SIADH), hypothyroidism, or glucocorticoid deficiency, the hospitalist needs to act accordingly.
"If the urine osm is high, higher than the serum osm, and is fixed at that level for some reason…giving that person isotonic fluids will lead to additional water retention and make the situation worse," he says. "It's very important to assess the volume status and establish the cause. And then, if you're going to give fluids, be mindful of what the urine might look like. Do not give fluids that are hypotonic with respect to what the urine is making, unless you are completely convinced that the person is dry and therefore needs volume."