Oxygen administration during surgery and postoperative organ injury: observational cohort study

Abstract

Objective: To examine whether supraphysiological oxygen administration during surgery is associated with lower or higher postoperative kidney, heart, and lung injury.

Design: Observational cohort study.

Setting: 42 medical centers across the United States participating in the Multicenter Perioperative Outcomes Group data registry.

Participants: Adult patients undergoing surgical procedures ≥120 minutes' duration with general anesthesia and endotracheal intubation who were admitted to hospital after surgery between January 2016 and November 2018.

Intervention: Supraphysiological oxygen administration, defined as the area under the curve of the fraction of inspired oxygen above air (21%) during minutes when the hemoglobin oxygen saturation was greater than 92%.

Main outcomes: Primary endpoints were acute kidney injury defined using Kidney Disease Improving Global Outcomes criteria, myocardial injury defined as serum troponin >0.04 ng/mL within 72 hours of surgery, and lung injury defined using international classification of diseases hospital discharge diagnosis codes.

Results: The cohort comprised 350 647 patients with median age 59 years (interquartile range 46-69 years), 180 546 women (51.5%), and median duration of surgery 205 minutes (interquartile range 158-279 minutes). Acute kidney injury was diagnosed in 19 207 of 297 554 patients (6.5%), myocardial injury in 8972 of 320 527 (2.8%), and lung injury in 13 789 of 312 161 (4.4%). The median fraction of inspired oxygen was 54.0% (interquartile range 47.5%-60.0%), and the area under the curve of supraphysiological inspired oxygen was 7951% min (5870-11 107% min), equivalent to an 80% fraction of inspired oxygen throughout a 135 minute procedure, for example. After accounting for baseline covariates and other potential confounding variables, increased oxygen exposure was associated with a higher risk of acute kidney injury, myocardial injury, and lung injury. Patients at the 75th centile for the area under the curve of the fraction of inspired oxygen had 26% greater odds of acute kidney injury (95% confidence interval 22% to 30%), 12% greater odds of myocardial injury (7% to 17%), and 14% greater odds of lung injury (12% to 16%) compared with patients at the 25th centile. Sensitivity analyses evaluating alternative definitions of the exposure, restricting the cohort, and conducting an instrumental variable analysis confirmed these observations.

Conclusions: Increased supraphysiological oxygen administration during surgery was associated with a higher incidence of kidney, myocardial, and lung injury. Residual confounding of these associations cannot be excluded.

Trial registration: Open Science Framework osf.io/cfd2m.

Fig 1

Numbers of eligible, excluded, and included patients. FIO₂=fraction of inspired oxygen; SpO₂=arterial hemoglobin oxygen saturation

Fig 2

Association between intraoperative oxygen exposure and acute kidney injury, myocardial injury, and lung injury, adjusted for factors included as covariates (age, sex, race, body mass index, American Society of Anesthesiologists status, Agency for Healthcare Research and Quality Elixhauser comorbidity index, chronic pulmonary disease, emergency surgery, preoperative serum creatinine, hemoglobin, troponin and lactate concentrations, nitrous oxide exposure, median tidal volume, median intraoperative positive end expiratory pressure, volumes of intraoperative intravenous crystalloid and packed red blood cells administrations, and intraoperative hypotension). Tick marks on x axes identify each decile of patients

Fig 3

Associations between increased intraoperative oxygen exposure and acute kidney injury, myocardial injury, and lung injury in all patients and in subgroups, adjusted for impact of factors included as covariates (age, sex, race, body mass index, American Society of Anesthesiologists status, Agency for Healthcare Research and Quality Elixhauser comorbidity index, chronic pulmonary disease, emergency surgery, preoperative serum creatinine, hemoglobin, troponin and lactate concentrations, nitrous oxide exposure, median tidal volume, median intraoperative positive end expiratory pressure, volumes of intraoperative intravenous crystalloid and packed red blood cells administrations, and intraoperative hypotension). Point estimates and bars represent odds ratios and 95% confidence intervals for organ injury associated with 75th centile compared with 25th centile of AUC_FIO2. P values represent statistical significance for each factor to modify association between oxygen exposure and organ injury, assessed with multiple degree of freedom test. AUC_FIO2=area under the curve of FIO₂ (fraction of inspired oxygen) above 21% during minutes when the corresponding oxygen saturation was >92%