Correlation of serum osmolality in medical encephalopathy

Abstract

Background: Hypoosmolality and hyperosmolality, which are relatively common clinical problems, are associated with pathological changes in brain volume: brain edema during hypoosmolar states and brain dehydration during hyperosmolar states.

Objectives: To calculate and measure serum osmolality in encephalopathy patients admitted to SKIMS medical emergency service and to correlate serum osmolality with the level of consciousness in these patients with follow up (outcome) at 6 months and 1 year.

Participants: Non-traumatic encephalopathy patients aged over 18 years.

Study design: The study was conducted prospectively over a period of 18 months.

Methods: Direct measurement of serum osmolality was done. ABG & KFT was done on admission and ABG repeated at 24 hours and after 24 hours for the calculation of serum osmolality. All the patients were followed up at 6 months and 1 year telephonically.

Results: Out of total 165 subjects, 99 (60%) were males and 66 (40%) females. No difference in outcome with relation to gender, age or number of comorbidities was found. Hyperosmolality was associated with worse GCS. Measured osmolality had a significant correlation with the orientation status of the study population while as calculated osmolality didn’t. The lower the GCS, the worse was the outcome. The measured osmolality was found to have a significant impact on the outcome of these patients, with hyperosmolality associated with worse outcome. The calculated osmolality at admission was not found to have any significant association with the outcome. Only 22.1% patients were alive at 1 year, these patients were of younger age groups, predominant etiology was drug toxicity, neurological infections, epilepsy or dyselectrolytemia, had a higher GCS on admission, lesser degree of disorientation and a lower mean osmolality.

Conclusions: Measured osmolality is more accurate for prognostication as well as in determining the grade of encephalopathy in comparison to calculated osmolality. Hyperosmolality is associated with worse outcome as well as the grade of encephalopathy. The outcome of these patients is independent of the age, gender and the number of underlying comorbidities while as GCS on admission, grade of encephalopathy and the measured osmolality have a significant impact on the outcome. These encephalopathy patients have a very high mortality rate.