For most patients undergoing coronary artery bypass grafting (CABG), removing the breathing tube and transitioning away from mechanical ventilation are important early milestones in recovery. However, a significant subset of cardiac surgery patients requires respiratory support much longer than expected. Prolonged mechanical ventilation (PMV) is associated with greater morbidity, mortality, intensive care utilization, hospital costs, and long-term functional impairment.
A 2026 study published in the Journal of Clinical Medicine investigated whether clinicians could identify patients at increased risk for prolonged ventilation using information available before CABG surgery. The researchers also examined how events occurring during and immediately after surgery could further refine that prediction.
The investigators retrospectively analyzed adult patients undergoing CABG at Hospital General Universitario Gregorio Marañón between January 2011 and December 2024. After exclusions, 2,083 patients formed the final study population. PMV was defined as invasive mechanical ventilation lasting more than 48 hours after surgery, including accumulated ventilation time in patients requiring reintubation.
About One in Nine Patients Experienced Prolonged Ventilation
Among the 2,083 patients, 241 developed PMV, an incidence of 11.6%. In other words, approximately one in nine patients remained mechanically ventilated for more than 48 hours.
Patients who developed PMV tended to have a more challenging preoperative clinical profile. They were older and more frequently had anemia, impaired kidney function, reduced left ventricular function, severe pulmonary hypertension, urgent surgery, previous cardiac surgery, and preoperative intra-aortic balloon pump support.
One particularly interesting finding involved preoperative anemia. Average hemoglobin was 12.6 g/dL among patients who developed PMV compared with 13.4 g/dL among those who did not. After adjustment, hemoglobin below 11 g/dL remained independently associated with PMV, with an odds ratio of 1.82.
This finding is important because anemia differs from many other risk factors: it may potentially be modifiable before surgery. The authors appropriately caution that their observational study cannot establish that correcting anemia will prevent prolonged ventilation. Nevertheless, the results support careful assessment of anemia and contemporary patient blood management before cardiac surgery.
A Practical Preoperative Risk Score
The researchers initially created a multivariable preoperative model that demonstrated good discrimination, with an apparent AUROC of 0.789 and an optimism-corrected AUROC of 0.774 following bootstrap internal validation.
They then converted the model into a simpler point-based score designed for bedside use.
The score incorporates age, hemoglobin below 11 g/dL, severe renal dysfunction, ventricular dysfunction, combined CABG and valve surgery, previous cardiac surgery, COPD, urgent surgery, and preoperative intra-aortic balloon pump use.
The resulting risk gradient was striking.
Patients scoring 0–2 points had only a 2.9% observed risk of prolonged ventilation. Risk increased to 10.6% with 3–5 points, 26.6% with 6–8 points, and 44.3% with 9 or more points.
Thus, the highest-risk patients experienced PMV at more than 15 times the observed rate of the lowest-risk category.
The simplified score retained much of the predictive performance of the more complex statistical model, achieving an AUROC of 0.780. Interestingly, this was similar to EuroSCORE II’s AUROC of 0.771 in this cohort, although the difference was not statistically significant. Unlike EuroSCORE II, however, the new score was specifically designed to predict prolonged ventilation rather than operative mortality.
Risk Changes During the Operation
One of the study’s strengths is that the investigators did not treat perioperative risk as static.
Adding intraoperative information improved model discrimination from an AUROC of 0.789 to 0.832. Cardiopulmonary bypass (CPB) duration and the intraoperative use of dobutamine and adrenaline were independently associated with PMV.
The relationship between bypass duration and respiratory risk was especially noteworthy. As illustrated by the restricted cubic spline on page 7, PMV risk was relatively stable at shorter bypass durations but began increasing progressively after approximately 120 minutes of CPB exposure.
The authors do not establish 120 minutes as a definitive causal threshold. Still, the pattern raises an important clinical consideration: prolonged exposure to cardiopulmonary bypass may contribute to pulmonary dysfunction through inflammatory activation, endothelial injury, capillary leak, and impaired postoperative gas exchange.
Why This Study Matters
Perhaps the most useful message from this research is that prolonged ventilation after CABG may be viewed as more than an isolated pulmonary complication. Instead, it can represent the cumulative effect of preoperative vulnerability, cardiac function, renal function, anemia, surgical complexity, cardiopulmonary bypass exposure, bleeding, transfusion, and hemodynamic stress.
Identifying high-risk patients before surgery could help clinicians plan ICU resources, counsel patients and families, optimize potentially modifiable factors, and apply targeted perioperative strategies.
The study also highlights preoperative anemia as a particularly interesting target. Optimizing anemia and reducing unnecessary transfusion are already important components of contemporary patient blood management, although prospective research is required to determine whether anemia correction itself reduces prolonged ventilation.
The new scoring system is promising, but it is not yet ready to be considered a universally validated risk calculator. The research comes from a single institution, is retrospective, and spans more than a decade during which perioperative practices evolved. External validation in independent patient populations will therefore be essential.
Still, the findings provide a clinically intuitive framework: some of the information needed to identify patients at risk for prolonged mechanical ventilation is available before surgery even begins. As additional information emerges during bypass and the early postoperative period, clinicians may be able to refine that prediction further and individualize care.
