Originally published by 2 Minute Medicine^® (view original article). Reused on AccessMedicine with permission.

1. Supraphysiological oxygen administration during surgery is associated with higher incidence of kidney, myocardial and lung injury

Evidence Rating Level: 2 (Good)

Greater than 80% of patients undergoing general anesthesia are exposed to oxygen administration higher than that required to maintain normal blood oxygen levels. There are potentially harmful effects of supplemental oxygen administration, however, due to the consequences of hypoxemia, supplemental oxygen is a common component of anesthesia. This retrospective cohort study included 350, 657 patients who underwent surgical procedures longer than 120 minutes under general anesthesia and measured clinical outcomes based on level of oxygen exposure including acute kidney injury (measured using the Kidney Disease Improving Global Outcomes) myocardial injury (defined as a troponin >0.04 ng/mL within 72 hours of operation) and lung injury (defined using the international classification of diseases hospital discharge diagnosis codes). For each patient, minute to minute FiO2 and SpO2 data were obtained, and the amount of oxygen that was in excess was determined. The incidence of acute kidney injury, myocardial infarction and lung injury were higher in those who received oxygen levels at supraphysiological levels; for example, those at the 75th percentile of oxygen levels had a 26% greater odds of acute kidney injury, 12% greater odds of myocardial injury, and 14% greater odds of lung injury compared to those at the 25^th percentile. The observational nature of this study and discrepancies on general diagnosis of these injuries (for example the use of diagnosis codes to identify lung injury) are a few limitations to this study. Future studies are needed to identify the best intraoperative oxygen administration guidelines, knowing that both hypoxemia and supraphysiological oxygen may be associated with adverse events.

Click to read the study in BMJ

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