cardiac surgery, marked by mechanical ventilation lasting 24 hours or more. This comprehensive systematic review and meta-analysis explores the incidence, associated risk factors, and in-hospital mortality linked to PMV among cardiac surgery patients, with data drawn from 32 studies encompassing 68,766 patients.
Incidence of PMV
The incidence of PMV was found to be 20%, but this varied significantly depending on the type of surgery and how PMV was defined. For example, patients undergoing complex aortic surgeries demonstrated the highest incidence (39.4%), while those receiving combined coronary artery bypass grafting (CABG) and valve surgery had the lowest (5.6%). When PMV was defined as lasting ≥72 hours, the incidence increased to 27.3%, compared to 16.1% for definitions of ≥24 hours. These findings emphasize that defining PMV consistently is crucial for reliable data interpretation and management planning.
Risk Factors for PMV
Fifteen significant risk factors for PMV were identified, falling into demographic, preoperative, and intraoperative categories:
- Demographic Risk Factors: Advanced age and female sex were strongly associated with PMV. Older patients are more prone to PMV due to reduced physiological reserves and increased comorbidities. Female patients showed increased susceptibility, potentially linked to hormonal differences and ICU-acquired muscle weakness.
- Preoperative Risk Factors: Conditions like ejection fraction (EF) <50%, body mass index (BMI) >28 kg/m², chronic obstructive pulmonary disease (COPD), and chronic renal failure were linked to increased PMV risk. A low EF and higher BMI signify compromised cardiovascular function and increased metabolic strain, respectively. Chronic renal failure exacerbates this by limiting physiological reserves.
- Intraoperative Risk Factors: Prolonged cardiopulmonary bypass (CPB) time, particularly exceeding 120 minutes, was a key factor. Longer CPB times increase the risk of systemic inflammation and ischemia-reperfusion injury, leading to respiratory complications that necessitate extended mechanical ventilation.
Impact on Mortality
The analysis revealed that PMV significantly elevates in-hospital mortality, with affected patients exhibiting a 14-fold increased risk compared to those without PMV. The highest mortality rates were observed in the PMV ≥72-hour group, particularly among patients undergoing CABG with valve surgery. The heightened mortality is linked to PMV-related complications like diaphragmatic dysfunction, muscle wasting, and prolonged ICU stays.
Clinical Implications
These findings underscore the importance of identifying at-risk patients to prevent PMV effectively. Implementing early extubation protocols and optimizing preoperative and intraoperative care are critical strategies. Addressing modifiable risk factors, such as controlling BMI and improving cardiac function preoperatively, can reduce PMV incidence. Furthermore, enhanced intraoperative management, including minimizing CPB time, may help mitigate risks.
Limitations
While this review provides valuable insights, it is constrained by the variability in PMV definitions across studies and limited non-English data inclusion. Additionally, some potential risk factors, like smoking history, were not comprehensively analyzed due to insufficient data.
Conclusions
The study highlights that PMV affects one in five cardiac surgery patients and significantly raises in-hospital mortality risks. Identifying and managing risk factors like advanced age, BMI, and prolonged CPB time is crucial for improving outcomes. Future research should refine PMV definitions, explore long-term impacts, and evaluate the role of less-studied factors to enhance prevention and management strategies.