Intraoperative ventilation strategies significantly impact patient outcomes, with a recent meta-analysis indicating that low tidal volume (LV) ventilation and driving pressure-guided positive end-expiratory pressure (PEEP) reduce postoperative pulmonary complications (PPCs). The study, encompassing 16 randomized controlled trials (RCTs) and 4993 patients, highlights the importance of tailored ventilation strategies during general anesthesia.
The meta-analysis, published in the British Journal of Anaesthesia, compared various ventilation strategies, including low tidal volume (6–8 ml/kg) with PEEP ≥5 cm H2O versus high tidal volume (>8 ml/kg) with zero PEEP, higher PEEP (≥6 cm H2O) versus lower PEEP (<6 cm H2O), and driving pressure-guided PEEP versus fixed PEEP. The primary outcome was the incidence of PPCs, with secondary outcomes including intraoperative cardiovascular complications and 30-day mortality.
Key Findings
The results indicated a significant reduction in PPCs with LV compared to high tidal volume (OR=0.402, CI 0.280–0.577, P<0.001) and with driving pressure-guided PEEP compared to fixed PEEP (OR=0.358, CI 0.187–0.684, P=0.002). However, higher PEEP was associated with a higher incidence of intraoperative cardiovascular complications (OR=1.385, CI 1.027–1.867, P=0.002). There was no significant difference in 30-day mortality across the different ventilation strategies.
Implications for Clinical Practice
The findings suggest that employing LV ventilation strategies, particularly when combined with driving pressure-guided PEEP, can mitigate the risk of PPCs. According to the study, "Optimal intraoperative mechanical ventilation is unclear; however, our meta-analysis showed that low tidal volume and driving pressure-guided PEEP strategies were associated with a reduction in postoperative pulmonary complications."
Understanding the Mechanisms
The reduction in PPCs with LV ventilation is attributed to the prevention of alveolar overdistension and ventilator-induced lung injury. High tidal volumes and pressures can cause alveolar and endothelial dysfunction, leading to vessel leakage and inflammation. LV ventilation, on the other hand, promotes a more homogenous distribution of tidal volume within the lungs.
Caveats and Considerations
The authors acknowledge several limitations, including the inclusion of only English-language articles and heterogeneity in the enrolled studies' inclusion and exclusion criteria. The definition and timeframe for PPCs also varied across studies. Additionally, the meta-analysis excluded patients with severe pulmonary and cardiac disease, limiting the generalizability of the findings to this population.
Future Directions
Despite these limitations, the meta-analysis provides valuable insights into optimizing intraoperative ventilation strategies. Further research is needed to investigate the influence of different ventilation strategies on postoperative outcomes, particularly in specific patient populations and with a focus on long-term quality of life.
