Background: We retrospectively compared the clinical outcome of post-cardiac surgery tracheal extubation between patients extubated with a lower than normal pH and patients extubated according to our routine institutional protocol. Our main goal was to clarify that strict adherence to the current criteria is dispensable.

Methods: In this retrospective cohort study, we recruited 256 patients who met our study criteria and divided them into the exposed group (n= 95) and the control group (n= 161). The inclusion criteria consisted of coronary artery bypass grafting alone and age> 18 years. The exclusion criteria comprised the use of corticosteroids in the preceding 2 weeks, Serum creatinine (SCr)> 2 mg/dL, uncontrolled diabetes, liver dysfunction, Glasgow coma scale <13, and acetazolamide and sodium bicarbonate use. The arterial blood gas (ABG) characteristics before and 6 hours after extubation, extubation failure rate, length of stay in the in ICU, length of stay in the hospital and mortality were compared between the two groups.

Results: In the control group, the males outnumbered the females and the ejection fraction was higher relative to that in the exposure group (P= 0.01 and P= 0.02, respectively). There were more patients with chronic obstructive pulmonary disease in the exposure group (P< 0.005) and also the euroSCORE was higher (P< 0.002). There were no significant differences between the groups regarding the ABG values at the time of ICU admission. Significantly higher levels of FiO₂ and PaCO₂ (P< 0.001 for both) as well as lower HCO3 and pH (P< 0.001 for both) were observed in the exposure group immediately before extubation. Following extubation, there was a significant increase in pH and a significant reduction in FiO₂ need in the exposure group (P< 0.001 for both). The extubation failure rate, length of stay in the in ICU, length of stay in the hospital, and mortality rate were not different between the 2 groups.