Hyperoxemia During Cardiac Surgery Is Associated With Postoperative Pulmonary Complications

Abstract

The use of hyperoxemia during cardiac surgery remains controversial. We hypothesized that intraoperative hyperoxemia during cardiac surgery is associated with an increased risk of postoperative pulmonary complications.

Design: Retrospective cohort study.

Setting: We analyzed intraoperative data from five hospitals within the Multicenter Perioperative Outcomes Group between January 1, 2014, and December 31, 2019. We assessed intraoperative oxygenation of adult patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Hyperoxemia pre and post CPB was quantified as the area under the curve (AUC) of Fio₂ above 0.21 in minutes when the corresponding peripheral oxygen saturation was greater than 92% measured by pulse oximetry. We quantified hyperoxemia during CPB as the AUC of Pao₂ greater than 200 mm Hg measured by arterial blood gas. We analyzed the association of hyperoxemia during all phases of cardiac surgery with the frequency of postoperative pulmonary complications within 30 days, including acute respiratory insufficiency or failure, acute respiratory distress syndrome, need for reintubation, and pneumonia.

Patients: Twenty-one thousand six hundred thirty-two cardiac surgical patients.

Interventions: None.

Measurements and main results: During 21,632 distinct cardiac surgery cases, 96.4% of patients spent at least 1 minute in hyperoxemia (99.1% pre-CPB, 98.5% intra-CPB, and 96.4% post-CPB). Increasing exposure to hyperoxemia was associated with an increased risk of postoperative pulmonary complications throughout three distinct surgical periods. During CPB, increasing exposure to hyperoxemia was associated with an increased odds of developing postoperative pulmonary complications (p < 0.001) in a linear manner. Hyperoxemia before CPB (p < 0.001) and after CPB (p = 0.02) were associated with increased odds of developing postoperative pulmonary complications in a U-shaped relationship.

Conclusions: Hyperoxemia occurs almost universally during cardiac surgery. Exposure to hyperoxemia assessed continuously as an AUC during the intraoperative period, but particularly during CPB, was associated with an increased incidence of postoperative pulmonary complications.

Keywords: cardiac surgery; hyperoxemia; postoperative pulmonary complications; supplemental oxygen.

Figure 1.

Consolidated Standards of Reporting Trials flow (CONSORT) diagram of exclusion criteria applied to the patient cohort. CPB = cardiopulmonary bypass.

Figure 2.

Distribution of hyperoxemia, stratified by postoperative pulmonary complications status displayed via overlaid histograms. A, Pre-cardiopulmonary bypass (CPB), B, intra-CBP, and C, post-CPB. For the pre- and post-CPB periods, median Fio₂ values are presented. For the intra-CPB period, median Pao₂ values are presented. PPC = postoperative pulmonary complication.

Figure 3.

Association between hyperoxemia exposure and the adjusted log odds ratio of postoperative pulmonary complications at three time points as estimated via multiple logistic regression. The x-axes denote the mean Fio₂ for 2A/2C and the mean Pao₂ for 2B. Tick marks along the x-axes delineate the 10 deciles of distribution for hyperoxemia exposure, measured by area under the curve. Shaded regions represent the 95% bootstrap CI for the predicted log odds of postoperative pulmonary complications. A, Pre-cardiopulmonary bypass (CPB), B, intra-CPB, and C, post-CPB. PPC = postoperative pulmonary complication.

Figure 4.

Association between pairwise combinations of hyperoxemia exposures and log odds ratio of postoperative pulmonary complications. Pairwise relationships between the hyperoxemia exposures and the adjusted log odds ratios of postoperative pulmonary complications (PPCs) were estimated via multiple logistic regression. The size of each bubble corresponds to the number of subjects who received each combination of hyperoxemia. Bubble color represents the log odds of postoperative pulmonary complications. The color scale is explained by the legend on the right of the plot. For pre- and post-cardiopulmonary bypass (CPB), axes tick marks indicate the median Fio₂ during the respective time period. For intra-CPB, axes tick marks indicate the median Pao₂ during the respective time period.