Effects of intraoperative high versus low inspiratory oxygen fraction (FiO2) on patient's outcome: A systematic review of evidence from the last 20 years

Where the Postanesthesia Care Unit and Intensive Care Unit Meet

The intensive care unit (ICU) was born from the postanesthesia care unit (PACU). In today's hospital systems, there remains a lot of overlap in the care missions of each location. The patient populations share many similarities and many of the same care, technology, and care protocols apply to patients in both units. As shown by the COVID-19 pandemic, there is immense value in maintaining protocols, processes, and staffing models for the safe care of ICU patients in the PACU when ICU demands exceed capacity.

Postoperative pulmonary complications with high versus standard FiO2 in adult patients undergoing major abdominal surgery: A noninferiority trial

BACKGROUND

Despite the possible clinical benefit of high intraoperative oxygen therapy on surgical site infection, the effect on postoperative respiratory function is debatable. However, it remains yet to be elucidated whether hyperoxia due to a high fraction of inspired oxygen used in conjunction with lung protective ventilation can lead to increased incidence of postoperative pulmonary complications.

METHODS

In this noninferiority randomized trial, an intraoperative high fraction of inspired oxygen of 0.8 (group H) was compared to a standard fraction of inspired oxygen of 0.3 to 0.4 (group S) in adult patients undergoing major elective or emergency surgery. A lung protective ventilation strategy was employed in all patients, including volume control ventilation with a tidal volume of 6 to 8 mL/kg of predicted body weight, respiratory rate of 12 beats per minute, and positive end-expiratory pressure of 5 to 8 cm H2O. Postoperative pulmonary complications were assessed on postoperative days 3 and 5 by the Melbourne group scale.

RESULTS

In this trial, n = 226 patients were randomized; among them, 130 patients underwent routine surgery, and 96 patients underwent emergency surgery. The median (interquartile range) of the patients was 48 (35-58) years, and 47.3% were female. Melbourne group scale scores at postoperative day 3 (median [interquartile range] 2 [1-4] in group S vs 2 [1-3] in group H; the difference in median [95% confidence interval] 0 [0, -1]; P = .13) and day 5 (median [interquartile range] 1 (0-3) in group S vs 1 [0-3] in group H; the difference in median [95% confidence interval] 0 [0, 0.5]; P = .34) were statistically similar in both the groups and the upper margin was within the predefined margin of 1. Incidence of surgical site infection (P = .46), postoperative hospital stay (P = .29), and days alive without antibiotic therapy at postoperative day 28 (P = .95) were similar in both groups.

CONCLUSION

High intraoperative fiO2 was noninferior to standard fiO2 in postoperative pulmonary complications in adult patients undergoing major surgery.

Effects of low versus high inspired oxygen fraction on myocardial injury after transcatheter aortic valve implantation: A randomized clinical trial

BACKGROUND

Oxygen therapy is used in various clinical situation, but its clinical outcomes are inconsistent. The relationship between the fraction of inspired oxygen (FIO2) during transcatheter aortic valve implantation (TAVI) and clinical outcomes has not been well studied. We investigated the association of FIO2 (low vs. high) and myocardial injury in patients undergoing TAVI.

METHODS

Adults undergoing transfemoral TAVI under general anesthesia were randomly assigned to receive FIO2 0.3 or 0.8 during procedure. The primary outcome was the area under the curve (AUC) for high-sensitivity cardiac troponin I (hs-cTnI) during the first 72 h following TAVI. Secondary outcomes included the AUC for postprocedural creatine kinase-myocardial band (CK-MB), acute kidney injury and recovery, conduction abnormalities, pacemaker implantation, stroke, myocardial infarction, and in-hospital mortality.

RESULTS

Between October 2017 and April 2022, 72 patients were randomized and 62 were included in the final analysis (n = 31 per group). The median (IQR) AUC for hs-cTnI in the first 72 h was 42.66 (24.82-65.44) and 71.96 (35.38-116.34) h·ng/mL in the FIO2 0.3 and 0.8 groups, respectively (p = 0.066). The AUC for CK-MB in the first 72 h was 257.6 (155.6-322.0) and 342.2 (195.4-485.2) h·ng/mL in the FIO2 0.3 and 0.8 groups, respectively (p = 0.132). Acute kidney recovery, defined as an increase in the estimated glomerular filtration rate ≥ 25% of baseline in 48 h, was more common in the FIO2 0.3 group (65% vs. 39%, p = 0.042). Other clinical outcomes were comparable between the groups.

CONCLUSIONS

The FIO2 level did not have a significant effect on periprocedural myocardial injury following TAVI. However, considering the marginal results, a benefit of low FIO2 during TAVI could not be ruled out.

Fraction of Inspired Oxygen During General Anesthesia for Non-Cardiac Surgery: Systematic Review and Meta-Analysis

Background

Controversy exists regarding the effects of a high versus a low intraoperative fraction of inspired oxygen (FiO₂) in adults undergoing general anesthesia. This systematic review and meta‐analysis investigated the effect of a high versus a low FiO₂ on postoperative outcomes.

Methods

PubMed and Embase were searched on March 22, 2022 for randomized clinical trials investigating the effect of different FiO₂ levels in adults undergoing general anesthesia for non‐cardiac surgery. Two investigators independently reviewed studies for relevance, extracted data, and assessed risk of bias. Meta‐analyses were performed for relevant outcomes, and potential effect measure modification was assessed in subgroup analyses and meta‐regression. The evidence certainty was evaluated using GRADE.

Results

This review included 25 original trials investigating the effect of a high (mostly 80%) versus a low (mostly 30%) FiO₂. Risk of bias was intermediate for all trials. A high FiO₂ did not result in a significant reduction in surgical site infections (OR: 0.91, 95% CI 0.81–1.02 [p = .10]). No effect was found for all other included outcomes, including mortality (OR = 1.27, 95% CI: 0.90–1.79 [p = .18]) and hospital length of stay (mean difference = 0.03 days, 95% CI −0.25 to 0.30 [p = .84). Results from subgroup analyses and meta‐regression did not identify any clear effect modifiers across outcomes. The certainty of evidence (GRADE) was rated as low for most outcomes.

Conclusions

In adults undergoing general anesthesia for non‐cardiac surgery, a high FiO₂ did not improve outcomes including surgical site infections, length of stay, or mortality. However, the certainty of the evidence was assessed as low.

Does Higher Intraoperative Fraction of Inspired Oxygen Improve Complication Rates Following Implant-Based Breast Reconstruction?

Background

The surgical literature debates about whether an average intraoperative fractional inspired level of oxygen (FiO₂) greater than 80% confers lower postsurgical complication rates. Although some evidence demonstrates minimal or no difference in short-term mortality or surgical site infections, few studies suggest negative long-term outcomes.

Objectives

To the best of our knowledge, this is the first study examining the relationship between intraoperative FiO₂ levels and postoperative outcomes in the setting of immediate prepectoral implant-based breast reconstruction.

Methods

The authors retrospectively reviewed the complication profiles of 309 patients who underwent prepectoral 2-stage breast reconstruction following mastectomy between 2018 and 2021 at a single institution. Two cohorts were created based on whether intraoperative FiO₂ was greater than 80% or less than or equal to 80%. Complication rates between the cohorts were analyzed using Chi-squared test, Fisher's exact test, and multivariable logistic regressions. Variables examined included demographic information; smoking history; preexisting comorbidities; history of chemotherapy, radiation, or axillary lymph node dissection; and perioperative information.

Results

Chi-squared and multivariable regression analysis demonstrated no significant difference between cohorts in complication rates other than reoperation. Reoperation rates were significantly increased in the FiO₂ greater than 80% cohort (P = 0.018). Multivariable logistic regression also demonstrated that the use of acellular dermal matrix was significantly associated with increased postoperative complications (odds ratio 11.985; P = 0.034).

Conclusions

Complication rates did not statistically differ in patients with varying intraoperative FiO₂ levels outside of reoperation rates. In the setting of implant-based prepectoral breast reconstruction, hyperoxygenation likely does not lead to improved postsurgical outcomes.

Level of Evidence 3