Optic Nerve Sheath Diameter Guided Detection of Sepsis-Associated Encephalopathy
Source: Critical Care (2020) 24:520
This letter was written in response to the research letter discussing the measurement of ultrasonography guided optic nerve sheath diameter (ONSD) in sepsis associated encephalopathy (SAE) and its correlation with outcome.
The author pointed out a few serious limitations of that study, some of which include:
- The difference in ONSD across the three population groups compared in the study is sub-millimetric.
- An unblinded investigator patient clinical condition can be biased to overestimate ONSD in SAE cases.
- The inclusion of elderly patients, many of which have septated or trabeculated ONS, which may have affected the measurement of the optic nerve diameter.
- The presence of the “blooming effect” from positive pressure ventilation and changes in end-tidal carbon dioxide, which can affect ONSD
The author challenge the ONSD threshold of ≥ 5.5 mm for detection of SAE due to these and other limitations.