Authors: Müller-Wirtz LM et al.
Journal: Anesthesiology, Accepted December 18, 2025. DOI: 10.1097/ALN.0000000000005906
Summary
This post hoc analysis of a large cluster factorial randomized trial evaluated whether intraoperative mechanical power—normalized to predicted body weight—is associated with postoperative oxygenation impairment and pulmonary complications in orthopedic surgical patients. Mechanical power integrates multiple ventilatory variables into a single measure of energy delivered to the respiratory system and has been proposed as a global marker of ventilator-related lung injury.
The investigators analyzed 2,860 orthopedic surgeries performed in 2,582 patients exposed to a wide range of ventilatory strategies through randomized combinations of tidal volume (6 vs 10 ml/kg PBW) and PEEP (5 vs 8 cmH₂O). Time-weighted mechanical power per predicted body weight (MP-PBW) was calculated and linked to postoperative oxygenation measured by the SpO₂/FiO₂ ratio in the PACU and on the ward, postoperative pulmonary complications (PPC), and hospital length of stay.
Higher intraoperative MP-PBW was independently associated with worse postoperative oxygenation in both the PACU and inpatient wards. Each 0.1 J/min/kgPBW increase in MP-PBW resulted in clinically meaningful reductions in oxygenation and was associated with a 55% increase in the odds of PPC. Importantly, higher mechanical power did not translate into longer hospital length of stay.
When compared with traditional ventilatory variables, mechanical power did not outperform driving pressure or peak pressure in explaining postoperative oxygenation impairment. Models incorporating driving pressure explained nearly the same degree of variance as those using MP-PBW, suggesting that simpler metrics may offer similar clinical insight.
Overall, the findings reinforce the importance of minimizing ventilatory energy delivery during surgery and support driving pressure as a practical intraoperative target comparable to mechanical power.
Key Points
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Higher intraoperative mechanical power is associated with worse postoperative oxygenation.
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Increased mechanical power is linked to a significantly higher risk of postoperative pulmonary complications.
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Mechanical power was not associated with longer hospital length of stay.
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Driving pressure showed a comparable association with postoperative oxygenation as mechanical power.
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Findings support lung-protective ventilation strategies even in non-thoracic orthopedic surgery.
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Simpler metrics such as driving pressure may be as clinically informative as mechanical power.
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