Calculated Serum Osmolality May be a Valuable Addition to Extubation Assessment

Clinicians typically focus on respiratory mechanics and spontaneous breathing trial performance to determine whether a patient is ready to be extubated. Could the addition of pre-extubation calculated hyperosmolarity improve extubation assessment?

Chinese researchers explored that idea in a study that compared outcomes among patients in two large databases — the MIMIC-IV, which contains de-identified records from Beth Israel Deaconess Medical Center that were collected between 2008 and 2022, and the eICU-CRD, which contains ICU data from multiple U.S. hospitals collected in 2014 and 2015.

Overall, 2,638 eligible extubations in the MIMIC-IV resulting in 317 reintubations, and 1,390 in the eICU-CRD resulting in 93 reintubations were included in the trial. Calculated serum osmolality (cOSM), which was derived from sodium, glucose, and blood urea nitrogen, was measured within the 24-hour period prior to extubation. 

Results showed:

• 48-hour reintubation occurred in 13.6% of index extubations in the MIMIC-IV with calculated serum osmolality >300 mOsm/kg and 10.8% with values ≤300 mOsm/kg.
• The association was replicated in eICU-CRD, where the corresponding risks were 10.5% and 4.6%.
• The corresponding adjusted 72-hour risk ratios were 1.25 and 1.53.
• Additional adjustment for respiratory severity produced little change within the corresponding measured subsets, whereas the continuous association was weaker in MIMIC-IV.

The authors believe their study adds a metabolic perspective on the patient’s physiologic state immediately before extubation that may be useful when making decisions surrounding extubation.

“Because cOsm can be derived from routinely available laboratory data, it merits prospective evaluation as a complementary marker within extubation assessment,” they wrote.

The study was published by Frontiers in Medicine.

Highlighted in RC Buzz, November 9, 2026