Cardiac surgery is a complex and invasive procedure that leads to critical postoperative conditions. This type of procedure is employed to treat cardiovascular diseases.¹ As it is considered a major procedure, it requires extensive assistance and care. That is why patients who undergo this type of surgery are sent to the intensive care unit (ICU) and kept there under intensive care until their hemodynamics, level of consciousness, and respiratory and cardiovascular functions are restored in the first few hours after surgery. However, some patients remain longer on mechanical ventilation (MV) and this may be associated with mortality.²

Some complications can prolong the time a patient spends on MV. Pulmonary complications are very common in the post-surgical period and are associated with factors such as age, male gender, previous illnesses — systemic arterial hypertension, diabetes mellitus, chronic obstructive pulmonary disease, chronic renal insufficiency, and length of time the patient is on cardiopulmonary bypass (CPB).³ As a result, the prolonged MV stay can increase mortality risk.⁴

It is pertinent to consider the risk aspects before admitting a patient, as care during support is also a reflection of the time spent in hospital. In addition, it is important to know the previous reasons why MV may be prolonged after surgery. Patients who remain on MV for a long time suffer physical deconditioning due to sedation, which causes muscle weakness in the diaphragm, thus increasing mortality. Another factor contributing to the high mortality rate is that these patients are more susceptible to ventilator-induced lung damage. Failure to wean is also a factor that contributes to the same outcome.⁵

The length of MV in patients undergoing cardiac surgery can increase the severity of the case and even lead to mortality since many of these patients have complications that are already postoperative. In those patients who stay longer, mortality is the result of cardiogenic shock, cardiac arrest, renal failure, multiple organ failure, and sepsis.⁶

It is known that a large number of patients are hospitalized due to cardiovascular diseases and that in many cases the intervention needs to be surgical. There are still few studies that make this type of correlation, so the present work can provide relevant data for the creation of protocols within hospitals. Therefore, the aim of this study is to correlate MV time with mortality in patients who have undergone cardiac surgery.

A total of 110 patients were assessed in this study. The sample was gathered for convenience and divided into two groups: those who remained on MV for less than eight hours and another with those who stayed on MV for more than eight hours.

Table 1 shows that the majority of patients were male, with 66 people (60%), the average age was 57 standard deviation (±) 8 years and the main comorbidity was a sedentary lifestyle, which was found in 79 people (72%). The other data were not significant between the groups, except for CPB time, which was higher in the group that stayed for more than eight hours (p = 0.03).

Table 2 shows some of the variables that were analyzed: MV, age, male gender, BMI, and CPB time. However, among these variables, MV time was associated with increased mortality (Central Illustration).

The study sought to investigate the relationship between MV time and mortality in patients who had undergone cardiac surgery. The results showed that the main variables related to mortality were male gender, MV, age, BMI, and CPB time.

Fernandez-Zamora et al.⁶ observed in their study that the mortality rate was higher in patients who remained on MV for a longer time. This finding is explained by the fact that these patients are more susceptible to sepsis and multiple organ failure. Suarez's study also reinforces this finding.⁷

A study of individuals who had undergone cardiac surgery showed that CPB time is a predictor of prolonged MV. Once it is associated with physiological changes, CPB can generate a systematic inflammatory response and increased capillary permeability, which can lead to pulmonary edema, contributing to prolonged MV.⁸

In our study, prolonged MV of more than eight hours was associated with CPB time. Unlike our investigation and the aforementioned ones, Parmana et al.⁹ assessed the duration of MV in patients who underwent off-pump myocardial revascularization. These authors observed that patients also remained on MV for prolonged periods of time. Despite not having CPB, which is a resource responsible for promoting an inflammatory response, other factors were evaluated and found to be predictors of prolonged ventilation. Some of them were high tidal volume, use of inotropic agents, and lungs inflammation.

García-Delgado et al.¹⁰ also concluded that high tidal volume is associated with prolonged ventilation since the volume is capable of generating inflammatory mediators, which in turn, promote biotrauma. The authors also considered that age and female gender were predictors of prolonged ventilation. With regard to gender, their study is in controversy with ours, where males were considered to be predictors of prolonged MV.

Bartz et al.¹¹ also stated in their study of patients who underwent myocardial revascularization that MV was associated with mortality. He pointed to CPB and age as triggering factors.

In terms of age, the present study showed a significant association between this factor and prolonged MV. Sankar et al.⁸ showed in their work that there was longer ventilation in the participants who were in the highest age group. This result is similar to that found by Rahimi et al.,¹² who explained that the ageing process brings structural and functional changes. This is because one of the risk factors for cardiovascular disease is advancing age, which makes this public vulnerable to the onset of hypertension, obesity, dyslipidemia, and other diseases that can increase this risk. In addition, lifestyle habits such as sedentary lifestyles, smoking, and alcohol consumption contribute to the morbidity and mortality of these elderly people.

In the study by Gumus et al.,¹³ there was no correlation between age and gender and prolonged MV, and the authors themselves stated that this result was due to the small number of participants compared to other studies. In contrast, the work by Aksoy et al.¹⁴ emphasized that female gender was a predictor of prolonged MV.

Although Sankar et al.⁸ presented significant results regarding the main causes of mortality after cardiac surgery related to CPB increasing the time on MV, due to inflammatory responses, Bignami et al.¹⁵ emphasized how pulmonary lesions were recurrent in the postoperative period consequently making them susceptible to mortality.

Ball et al.¹⁶ discussed pulmonary complications. Although there is still no definition of these consequences in the postoperative period, they may be associated with the duration and type of surgery, also taking into account the patient's existing predispositions.

The findings of the present research will justify its clinical and scientific relevance. They will also serve as a basis for other works and contribute as a source of information for other students and others interested in the hospital area.

The limitations of this study involve factors that were not assessed, such as high tidal volume, the use of inotropes, and pulmonary inflammation, which could have influenced the results. Furthermore, the absence of an evaluation of pre-existing frailty status is a significant limitation, as frailty is a well-established prognostic factor, particularly concerning mortality and functional recovery in critically ill patients. A more comprehensive discussion of the clinical implications could be improved by considering these factors, as well as incorporating strategies such as early mobilization, sedation protocols, and adjunctive therapies, including anti-inflammatory drugs. These elements might not only affect extubation success but also influence post-ICU recovery and long-term quality of life. A deeper analysis of these variables would provide a more nuanced understanding of critical care management and enhance therapeutic strategies. The small number of patients is another limitation of the study.

An innovative approach to analyzing the relationship between MV time and mortality after coronary artery bypass grafting could involve combining predictive modeling, risk stratification, and conducting multicenter cohort studies. By developing advanced statistical models, such as machine learning, it is possible to identify predictive factors that influence both prolonged ventilation and mortality outcomes, allowing for personalized postoperative care. At the same time, stratifying patients based on demographic characteristics and comorbidities would help identify at-risk subgroups, guiding more targeted interventions. Finally, conducting a multicenter study would broaden the diversity of the collected data, enabling comparisons between different clinical practices and their respective associations with MV outcomes and mortality, providing a more comprehensive view of the issue.

Based on what was found in the studies analyzed, MV time of more than eight hours is a predictor of mortality after heart surgery given that some risk factors contribute to patients remaining on MV for longer.