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

Background

Surgical site infection is one of the most common adverse outcomes of surgery and is considered largely preventable (Stall et al 2013, Wetterslev et al 2015, Allegranzi et al 2016). Surgical site infections place a considerable burden on health care, both to the patient in terms of morbidity and mortality and organizationally with prolonged stays in hospitals and increased costs (Stall et al 2013, Allegranzi et al 2016).

Over the years research has examined whether the administration of inspired oxygen during surgery, and within the first postoperative hours, affects the frequency of wound infections. Findings from the studies have varied showing both a reduction in the frequency of surgical wound infections with high inspiratory oxygenation while also reporting wound infections to nearly double (Pryor et al 2004, Belda et al 2005, Wetterslev et al 2015). The administration of high fraction of inspired oxygen (FiO₂) equal to or above 60% is thought to improve the body’s ability to defend against bacteria and aid in tissue healing.

Objective/s

The objective of the review was to examine the available research evidence related 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.

Intervention/methods

The methods utilized in this review were consistent with the methods outlined in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). A comprehensive search was conducted in multiple databases up to March 2015. The review included randomized clinical trials (RCTs) only (excluding quasi-randomized and observational studies) and adult patients (18 years and older) who underwent elective or emergency surgery. Interventions included studies which compared a high FiO₂ of 60% or above with a control FiO₂ of 40% or below during surgery or both during surgery and during time spent in the postanaesthetic care unit. Primary outcomes of interest included all-cause mortality (assessed according to the longest follow-up period for each trial and surgical site infection within 30 days of follow-up after surgery).

Results

A total of 28 RCTs (9330 participants) were included in the review. The majority of studies were conducted in high-income countries (n = 26) and conducted in Europe (n = 7) or North America (n = 7). A total of 7537 participants provided data to the outcomes of interest for this review. The number of participants varied between each study from 38-2012 participants, with one study including a small proportion of participants aged 15-17 years. The surgical intervention varied across studies from colorectal and abdominal surgery, appendectomy, caesarean section, breast surgery, and orthopaedic surgery along with a variety of other surgeries. The majority of studies examined an FiO₂ of 80% oxygen or greater delivered via non-rebreathing or tightly sealed masks with high flow.

A total of eight studies, 4918 participants, provided data on mortality. When examining the longest follow up period for each study, the overall findings demonstrated that a high FiO₂ of 60% to 90% compared with 30% to 40% oxygen used during the perioperative period was not associated with all-cause mortality (RR 1.07, 95% CI 0.87 to 1.33). In a subgroup analysis of studies with overall low risk of bias (n = 4 studies), the results remained consistent; a high FiO₂ was not associated with all-cause mortality (RR 1.12, 95% CI 0.93 to 1.36).

A total of 15 studies, 7219 participants, provided data on surgical site infection. When examining surgical site infection within 14 to 30 days of follow-up after surgery, the overall findings demonstrated participants were 13% less likely to develop a surgical site infection when receiving high FiO₂, however these results were not significant (RR 0.87, 95% CI 0.71 to 1.07; P value = 0.18). In sub group analysis of studies with overall low risk of bias (n = 5 studies) the findings were consistent (RR 0.86, 95% CI 0.63 to 1.17; participants = 4201).

Conclusions

The evidence remains inclusive as to whether a high FiO₂ reduces all-cause mortality and surgical site infection rates. The results indicated a higher risk of mortality in the interventions group however the findings were not statistically significant. In relation to surgical site infection, the findings demonstrated a decrease risk in the intervention group; however these findings were not statistically significant. Due to weakness in the available evidence such as the risk of attrition and outcome reporting bias, 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. The authors’ concluded there was insufficient evidence to support the routine use of FiO₂ and recommended that further research be conducted to derive definitive conclusions.

Implications for practice

The findings from this review remain inconclusive as to whether high fraction inspired oxygen should be delivered perioperatively. These findings are in contrast to the recommendations from the World Health Organization which states that “adult patients undergoing general anaesthesia with endotracheal intubation for surgical procedures should receive an 80% FiO₂ intraoperatively and, if feasible, in the immediate postoperative period for 2–6 h, to reduce the risk of SSI” (Allegranzi et al 2016, p.e288).

While the evidence remains inconclusive as to whether high fraction inspired oxygen delivered perioperatively is beneficial or harmful to patients in relation to mortality and surgical site infection, nurses continue to play a major role in both administering and monitoring the patient on oxygen therapy. The use of oxygen therapy to main adequate levels of arterial oxygen should be upheld.

No competing interests declared