Identifying factors associated with prolonged mechanical ventilation following isolated coronary artery bypass grafting: a retrospective observational study

Background

The Society of Thoracic Surgeons has advocated for enhanced recovery after cardiac surgery and recommends extubation of patients within 6 h following routine coronary artery bypass grafting (CABG). Early extubation has been shown to decrease mortality and postoperative complications. The primary objective of this study was to create a preliminary prediction model that would identify modifiable factors associated with prolonged postoperative mechanical ventilation following isolated CABG at our institution.

Methods

This was a single-center retrospective observational records review study. Case records for 85 patients who had undergone an isolated, elective CABG between January 2021 and December 2022 were evaluated. A multivariable logistic regression model with backwards selection was used to estimate probability of prolonged postoperative mechanical ventilation (>6 h). Predictor variables were based on readily available clinical information on patient demographics, comorbidities, and factors related to operative management (time on bypass, opioid use, patient acid-base status, core temperature). Models were internally validated by bootstrapping, and model performance was evaluated by optimism-corrected c-statistics.

Results

Twenty-six of 85 patients (31 %) were intubated for >6 h. Base deficit, age, core temperature, and history of chronic obstructive pulmonary disease (COPD) were the strongest and most consistent predictors of prolonged intubation. Model discrimination and calibration were satisfactory (c-statistics > 0.75). A simple probability chart was constructed from the final model to estimate patient risk of prolonged intubation.

Conclusions

Older (>75 years), increased base deficit (base deficit ≤ -6 mmol/L), and hypothermic (<36 °C) patients with history of COPD had the highest estimated probability of prolonged intubation (>90 %) following isolated CABG. Future validation studies will require a larger cohort. Nevertheless, findings from this study have led to proactive changes in patient management at our institution to identify high-risk patients and prevent or partially reverse base deficit and hypothermia before patient arrival to the intensive care unit.