Associations of End-Tidal Carbon Dioxide Concentrations with Postoperative Outcomes: is Mechanical Power Next?
British Journal of Anaesthesia 135, 1591-1594
doi: 10.1016/j.bja.2025.09.005
What's the question?
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Is the end-tidal carbon dioxide (ETCO2) level during surgery associated with complications, specifically postoperative pulmonary complications (PPCs)?
Background Information
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Nasa et al. (doi 10.1016/j.bja.2025.07.076) assessed data from two large trials (PROVILHO and PROBESE) to assess the relationship between intraoperative ETCO2 and postoperative outcome.
The study
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Patients with a low ETCO2 were more likely to be older, taller, and non-obese, with higher lung compliance than those without hypocapnia
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Patients with a low ETCO2 were ventilated with a higher tidal volume and a higher minute volume than those without hypocapnia
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Why might anaesthetists hyperventilate patients?
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compensation for insufflated carbon dioxide eg during laparoscopy​​
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some studies (weak) show hyperventilation can lead to less shoulder pain​
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Strengths and Weaknesses
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Lower ETCO2 may be a reflection of a high PaCO2-ETCO2 gradient, which may reflect poor cardiovascular function
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No arterial blood gases were available in the referenced study, so no data on the true gradient is available
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Higher tidal volumes can decrease venous return, decreasing cardiac output and therefore reducing ETCO2​
PHRACC's Conclusions
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There appears to be an independent relationship between low intraoperative ETCO2 and and the occurrence of postoperative pulmonary complications
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This relationship holds whether patients have a BMI <30 or a BMI >30