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Meta-Analysis
. 2015 Jun 25;2015(6):CD008884.
doi: 10.1002/14651858.CD008884.pub2.

The effects of high perioperative inspiratory oxygen fraction for adult surgical patients

Jørn Wetterslev  1 , Christian S Meyhoff, Lars N Jørgensen, Christian Gluud, Jane Lindschou, Lars S Rasmussen
Affiliations
Meta-Analysis

The effects of high perioperative inspiratory oxygen fraction for adult surgical patients

Jørn Wetterslev et al. Cochrane Database Syst Rev. .

Abstract

Background: Available evidence on the effects of a high fraction of inspired oxygen (FIO2) of 60% to 90% compared with a routine fraction of inspired oxygen of 30% to 40%, during anaesthesia and surgery, on mortality and surgical site infection has been inconclusive. Previous trials and meta-analyses have led to different conclusions on whether a high fraction of supplemental inspired oxygen during anaesthesia may decrease or increase mortality and surgical site infections in surgical patients.

Objectives: To assess the benefits and harms of an FIO2 equal to or greater than 60% compared with a control FIO2 at or below 40% in the perioperative setting in terms of mortality, surgical site infection, respiratory insufficiency, serious adverse events and length of stay during the index admission for adult surgical patients.We looked at various outcomes, conducted subgroup and sensitivity analyses, examined the role of bias and applied trial sequential analysis (TSA) to examine the level of evidence supporting or refuting a high FIO2 during surgery, anaesthesia and recovery.

Search methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, BIOSIS, International Web of Science, the Latin American and Caribbean Health Science Information Database (LILACS), advanced Google and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) up to February 2014. We checked the references of included trials and reviews for unidentified relevant trials and reran the searches in March 2015. We will consider two studies of interest when we update the review.

Selection criteria: We included randomized clinical trials that compared a high fraction of inspired oxygen with a routine fraction of inspired oxygen during anaesthesia, surgery and recovery in individuals 18 years of age or older.

Data collection and analysis: Two review authors extracted data independently. We conducted random-effects and fixed-effect meta-analyses, and for dichotomous outcomes, we calculated risk ratios (RRs). We used published data and data obtained by contacting trial authors.To minimize the risk of systematic error, we assessed the risk of bias of the included trials. To reduce the risk of random errors caused by sparse data and repetitive updating of cumulative meta-analyses, we applied trial sequential analyses. We used Grades of Recommendation, Assessment, Development and Evaluation (GRADE) to assess the quality of the evidence.

Main results: We included 28 randomized clinical trials (9330 participants); in the 21 trials reporting relevant outcomes for this review, 7597 participants were randomly assigned to a high fraction of inspired oxygen versus a routine fraction of inspired oxygen.In trials with an overall low risk of bias, a high fraction of inspired oxygen compared with a routine fraction of inspired oxygen was not associated with all-cause mortality (random-effects model: RR 1.12, 95% confidence interval (CI) 0.93 to 1.36; GRADE: low quality) within the longest follow-up and within 30 days of follow-up (Peto odds ratio (OR) 0.99, 95% CI 0.61 to 1.60; GRADE: low quality). In a trial sequential analysis, the required information size was not reached and the analysis could not refute a 20% increase in mortality. Similarly, when all trials were included, a high fraction of inspired oxygen was not associated with all-cause mortality to the longest follow-up (RR 1.07, 95% CI 0.87 to 1.33) or within 30 days of follow-up (Peto OR 0.83, 95% CI 0.54 to 1.29), both of very low quality according to GRADE. Neither was a high fraction of inspired oxygen associated with the risk of surgical site infection in trials with low risk of bias (RR 0.86, 95% CI 0.63 to 1.17; GRADE: low quality) or in all trials (RR 0.87, 95% CI 0.71 to 1.07; GRADE: low quality). A high fraction of inspired oxygen was not associated with respiratory insufficiency (RR 1.25, 95% CI 0.79 to 1.99), serious adverse events (RR 0.96, 95% CI 0.65 to 1.43) or length of stay (mean difference -0.06 days, 95% CI -0.44 to 0.32 days).In subgroup analyses of nine trials using preoperative antibiotics, a high fraction of inspired oxygen was associated with a decrease in surgical site infections (RR 0.76, 95% CI 0.60 to 0.97; GRADE: very low quality); a similar effect was noted in the five trials adequately blinded for the outcome assessment (RR 0.79, 95% CI 0.66 to 0.96; GRADE: very low quality). We did not observe an effect of a high fraction of inspired oxygen on surgical site infections in any other subgroup analyses.

Authors' conclusions: As the risk of adverse events, including mortality, may be increased by a fraction of inspired oxygen of 60% or higher, and as robust evidence is lacking for a beneficial effect of a fraction of inspired oxygen of 60% or higher on surgical site infection, our overall results suggest that evidence is insufficient to support the routine use of a high fraction of inspired oxygen during anaesthesia and surgery. Given the risk of attrition and outcome reporting bias, as well as other weaknesses in the available evidence, further randomized clinical trials with low risk of bias in all bias domains, including a large sample size and long-term follow-up, are warranted.

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Conflict of interest statement

Jørn Wetterslev (JW), Christian S Meyhoff (CSM), Lars N Jørgensen (LNJ), Christian Gluud (CG), Jane Lindschou (JL), Lars S Rasmussen (LSR).

JW, CSM, LNJ and LSR were all members of the Steering Committee for the Meyhoff 2009 trial.

CSM was the principal investigator of the Meyhoff 2009 trial. (JL and CG extracted data and evaluated bias for the Meyhoff 2009 trial. Neither was involved in planning, conduct or analysis of the Meyhoff 2009 trial.)

JW and CG are members of the task force on trial sequential analysis (TSA) at the Copenhagen Trial Unit developing and programming TSA (www.ctu.dk/tsa).

LSR is Editor‐in‐Chief of Acta Anaesthesiologica Scandinavica; he has received funding from the Tryg Foundation, a philanthropic foundation that supports research and has financed a professorship in emergency medicine.

JL have reported no conflicts of interest.

Figures

1
1
Funnel plot of comparison: 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, outcome: 1.5 Surgical site infection stratified according to overall risk of bias in a random‐effects model.
2
2
Trial sequential analysis of the effect on mortality within the longest follow‐up in trials with overall low risk of bias. With an anticipated relative risk increase (RRI) of 20%, mortality in the control group of 15.7% with a type 1 error of 5% and a type 2 error of 20%, and diversity (D2) of 57%, the required information size is 10,736 participants. The cumulative Z‐curve does not cross the conventional boundary nor the trial sequential monitoring boundary for harm. The cumulative Z‐curve does not reach the futility area. Therefore evidence of an effect on all‐cause mortality based on trials with low risk of bias is lacking, and we cannot exclude a 20% RRI due to lack of data.
3
3
Trial sequential analysis of all trials reporting all‐cause mortality. With an anticipated relative risk increase (RRI) of 20%, mortality in the control group of 15.7% with a type 1 error of 5% and a type 2 error of 20% and diversity (D2) of 65%, the required information size is 13,264 participants. The cumulative Z‐curve does not cross the conventional boundaries nor the boundaries for benefit or harm. The cumulative Z‐curve does not reach the futility area. Therefore evidence of both beneficial and harmful effects on all‐cause mortality is lacking for all trials regardless of risk of bias and with varying time to follow‐up. We cannot exclude a 20% RRI or RRR due to lack of data.
4
4
Trial flow diagram. We reran the search in March 2015. We found two studies of interest, which we will consider when we update the review.
5
5
Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.
6
6
Trial sequential analysis (TSA) of high inspiratory supplemental oxygen fraction 60% to 90% vs 30% to 40% in surgical site infection for all trials of surgical participants within 14 to 30 days of follow‐up. The required information size to detect or reject a 20% relative risk reduction in a random‐effects model was estimated at 13,189 participants, using a control event proportion of 12.9% and diversity of 63% among included trials (I2 = 48%; 95% CI 30% to 62%; P value = 0.02). Fifteen trials with 7219 participants provided data on surgical site infection. The conventional boundary for statistical significance was not crossed (P value = 0.18) and the trial sequential monitoring boundary for benefit was not crossed, as the TSA adjusted CI for the risk ratio was as follows: RR 0.87, 95% CI 0.65 to 1.17).
1.1
1.1. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 1 Mortality within longest follow‐up stratified according to overall risk of bias.
1.2
1.2. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 2 Mortality within longest follow‐up best/worst case scenario of participants lost to follow‐up.
1.3
1.3. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 3 Mortality within longest follow‐up worst/best case scenario of participants lost to follow‐up.
1.4
1.4. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 4 Mortality within 30 days of follow‐up stratified according to overall risk of bias.
1.5
1.5. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 5 Surgical site infection stratified according to overall risk of bias in a random‐effects model.
1.6
1.6. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 6 Surgical site infection stratified according to overall risk of bias in a fixed‐effect model.
1.7
1.7. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 7 Surgical site infection stratified according to use of nitrous oxide.
1.8
1.8. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 8 Surgical site infection stratified according to FIO2 in the intervention group higher or lower than 80%.
1.9
1.9. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 9 Surgical site infection stratified according to use of high FIO2 during operation and the postoperative period.
1.10
1.10. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 10 Surgical site infection stratified according to type of surgery.
1.11
1.11. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 11 Surgical site infection according to follow‐up longer or shorter than 14 days.
1.12
1.12. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 12 Surgical site infection stratified according to use of preoperative antibiotics.
1.13
1.13. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 13 Surgical site infection stratified according to sequence generation.
1.14
1.14. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 14 Surgical site infection stratified according to allocation concealment.
1.15
1.15. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 15 Surgical site infection according to blinding of participants and personnel.
1.16
1.16. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 16 Surgical site infection stratified according to outcome assessment.
1.17
1.17. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 17 Surgical site infection stratified according to completeness of outcome data.
1.18
1.18. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 18 Surgical site infection stratified according to outcome reporting.
1.19
1.19. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 19 Surgical site infection stratified according to presence of other bias.
1.20
1.20. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 20 Surgical site infection best/worst case scenario of participants lost to follow‐up.
1.21
1.21. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 21 Surgical site infection worst/best case scenario of participants lost to follow‐up.
1.22
1.22. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 22 Respiratory insufficiency stratified according to overall risk of bias.
1.23
1.23. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 23 Serious adverse events.
1.24
1.24. Analysis
Comparison 1 60% to 90% oxygen vs 30% to 40% oxygen perioperatively, Outcome 24 Length of stay after surgery.
See this image and copyright information in PMC

Update of

  • doi: 10.1002/14651858.CD008884

References

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References to studies excluded from this review

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References to studies awaiting assessment

Gin 2013 {unpublished data only}
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Schietroma 2014 {published data only}
    1. Schietroma M, Cecilia EM, Sista F, Carlei F, Pessia B, Amicucci G. High‐concentration supplemental perioperative oxygen and surgical site infection following elective colorectal surgery for rectal cancer: a prospective, randomized, double‐blind, controlled, single‐site trial. The Amercian Journal of Surgery 2014;208(5):719‐26. [DOI: 10.1016/j.amjsurg.2014.04.002.] - DOI - PubMed

References to ongoing studies

Osvaldo 2011 {published data only}
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