Associations of intraoperative end–tidal CO2 levels with postoperative outcome–secondary analysis of a worldwide observational study
Prashant Nasa, David M. P. van Meenen, Frederique Paulus, Marcelo Gama de Abreu, Sebastiaan M. Bossers, Patrick Schober, Marcus J. Schultz, Ary Serpa Neto, Sabrine N.T. Hemmes, Wolfgang Kroell, Helfried Metzler, Gerd Struber, Thomas Wegscheider, Hans Gombotz, Michael Hiesmayr, Werner Schmid, Bernhard Urbanek, David Kahn, Mona Momeni, Audrey Pospiech, Fernande Lois, Patrice Forget, Irina Grosu, Jan Poelaert, Veerle van Mossevelde, Marie-Claire van Malderen, Dimitri Dylst, Jeroen van Melkebeek, Maud Beran, Stefan de Hert, Luc De Baerdemaeker, Bjorn Heyse, Jurgen Van Limmen, Piet Wyffels, Tom Jacobs, Nathalie Roels, Ann De Bruyne, Stijn van de Velde, Brigitte Leva, Sandrine Damster, Benoit Plichon, Marina JurosZovko, Dejana Djonovic-Omanoviċ, Selma Pernar, Josip Zunic, Petar Miskovic, Antonio Zilic, Slavica Kvolik, Dubravka Ivic, Darija Azenic-Venzera, Sonja Skiljic, Hrvoje Vinkovic, Ivana Oputric, Kazimir Juricic, Vedran Frkovic, Jasminka Kopic, Ivan Mirkovic, Nenad Karanovic, Mladen Carev, Natasa Dropulic, Jadranka Pavicic Saric, Gorjana Erceg, Matea Bogdanovic Dvorscak, Branka Mazul-Sunko, Anna Marija Pavicic, Tanja Goranovic, Branka Maldini, Tomislav Radocaj, Zeljka Gavranovic, Inga Mladic-Batinica, Mirna Sehovic, Petr Stourac, Hana Harazim, Olga Smekalova, Martina Kosinova, Tomas Kolacek, Kamil Hudacek, Michal Drab, Jan Brujevic, Katerina Vitkova, Katerina Jirmanova, Ivana Volfova, Paula Dzurnakova, Katarina Liskova, Radovan Dudas, Radek Filipsky, Samir El Kafrawy, Hisham Hosny Abdelwahab, Tarek Metwally, Ahmed Abdel-Razek, Ahmed Mostafa El-Shaarawy, Wael Fathy Hasan, Ahmed Gouda Ahmed, Hany Yassin, Mohamed Magdy, Mahdy Abdelhady, Mohamed Mahran, Eiko Herodes, Peeter Kivik, Juri Oganjan
Abstract
Patients receiving intraoperative ventilation during general anesthesia often have low end–tidal CO 2 (etCO 2 ). We examined the association of intraoperative etCO 2 levels with the occurrence of postoperative pulmonary complications (PPCs) in a conveniently–sized international, prospective study named ‘Local ASsessment of Ventilatory management during General Anesthesia for Surgery’ (LAS VEGAS). Patients at high risk of PPCs were categorized as ‘low etCO 2 ’ or ‘normal to high etCO 2 ’ patients, using a cut–off of 35 mmHg. The primary endpoint was a composite of previously defined PPCs; the individual PPCs served as secondary endpoints. The need for unplanned oxygen was defined as mild PPCs and severe PPCs included pneumonia, respiratory failure, acute respiratory distress syndrome, barotrauma, and new invasive ventilation. We performed propensity score matching and LOESS regression to evaluate the relationship between the lowest etCO 2 and PPCs. The analysis included 1843 (74 %) ‘low etCO 2 ’ patients and 648 (26 %) ‘normal to high etCO 2 ’ patients. There was no difference in the occurrence of PPCs between ‘low etCO 2 ’ and ‘normal to high etCO 2 ’ patients (20 % vs. 19 %; RR 1.00 [95 %–confidence interval 0.94 to 1.06]; P = 0.84). The proportion of severe PPCs among total occurring PPCs, were higher in ‘low etCO 2 ’ patients compared to ‘normal to high etCO 2 ’ patients (35 % vs. 18 %; RR 1.16 [1.08 to 1.25]; P < 0.001). Propensity score matching did not change these findings. LOESS plot showed an inverse relationship of intraoperative etCO 2 levels with the occurrence of PPCs. In this cohort of patients at high risk of PPCs, the overall occurrence of PPCs was not different between ‘low etCO 2 ’ patients and ‘normal to high etCO 2 ’ patients, but severe PPCs occurred more often in ‘low etCO 2 ’, with an inverse dose–dependent relationship between intraoperative etCO 2 levels and PPCs. This analysis was performed without additional funding. LAS VEGAS was partially funded and endorsed by the European Society of Anesthesiology and Intensive Care (ESAIC) and the Amsterdam University Medical Centers, location ‘AMC’. LAS VEGAS was registered at Clinicaltrials.gov ( NCT01601223 ), first posted on May 17, 2012. • This secondary analysis of the LAS VEGAS study, aimed to examine the association between etCO₂ levels and the occurrence of PPCs. • No significant difference was found in overall PPCs between ‘low etCO₂ (below 35 mmHg)’ and ‘normal to high etCO₂ (≥ 35 mmHg)’ patients (20 % vs. 19 %). • Severe PPCs were more common in the ‘low etCO₂’ group (35 % vs. 18 %). Propensity score matching did not alter the results, showing a robust association. • Potential mechanisms include hyperventilation causing ventilator-induced lung injury, ventilation-perfusion mismatching, or an underlying pulmonary pathology. • Future prospective studies should explore the causality between low etCO₂ and severe PPCs.