Supplemental postoperative oxygen and tissue oxygen tension in morbidly obese patients

High inspired oxygen versus low inspired oxygen for reducing surgical site infection: a meta-analysis

To perform a meta-analysis of published literature to assess the role of high-concentration inspired oxygen in reducing the incidence of surgical site infections (SSIs) following all types of surgery, a comprehensive search for published randomized controlled trials (RCTs) comparing high- with low-concentration inspired oxygen for SSIs was performed. The related data were extracted by two independent authors. The fixed and random effects methods were used to combine data. Twelve RCTs involving 6750 patients were included. Our pooled result found that no significant difference in the incidence of SSIs was observed between the two groups, but there was high statistic heterogeneity across the studies [risk ratio (RR): 0·91; 95% confidence interval (CI): 0·72-1·14; P = 0·40; I² = 54%]. The sensitivity analysis revealed the superiority of high-concentration oxygen in decreasing the SSI rate (RR: 0·86; 95% CI: 0·75-0·98; P = 0·02). Moreover, a subgroup analysis of studies with intestinal tract surgery showed that patients experienced less SSI when high-concentration inspired oxygen was administrated (RR: 0·53; 95% CI: 0·37-0·74; P = 0·0003). Our study provided no direct support for high-concentration inspired oxygen in reducing the incidence of SSIs in patients undergoing all types of surgery.

The Effects of Local Warming on Surgical Site Infection

BACKGROUND

Surgical site infections (SSI) account for a major proportion of hospital-acquired infections. They are associated with longer hospital stay, readmissions, increased costs, mortality, and morbidity. Reducing SSI is a goal of the Surgical Care Improvement Project and identifying interventions that reduce SSI effectively is of interest. In a single-blinded randomized controlled trial (RCT) we evaluated the effect of localized warming applied to surgical incisions on SSI development and selected cellular (immune, endothelial) and tissue responses (oxygenation, collagen).

METHODS

After Institutional Review Board approval and consent, patients having open bariatric, colon, or gynecologic-oncologic related operations were enrolled and randomly assigned to local incision warming (6 post-operative treatments) or non-warming. A prototype surgical bandage was used for all patients. The study protocol included intra-operative warming to maintain core temperature ≥36°C and administration of 0.80 FIO2. Patients were followed for 6 wks for the primary outcome of SSI determined by U.S. Centers for Disease Control (CDC) criteria and ASEPSIS scores (additional treatment; presence of serous discharge, erythema, purulent exudate, and separation of the deep tissues; isolation of bacteria; and duration of inpatient stay). Tissue oxygen (PscO2) and samples for cellular analyses were obtained using subcutaneous polytetrafluoroethylene (ePTFE) tubes and oxygen micro-electrodes implanted adjacent to the incision. Cellular and tissue ePTFE samples were evaluated using flow cytometry, immunohistochemistry, and Sircol™ collagen assay (Biocolor Ltd., Carrickfergus, United Kingdom).

RESULTS

One hundred forty-six patients participated (n=73 per group). Study groups were similar on demographic parameters and for intra-operative management factors. The CDC defined rate of SSI was 18%; occurrence of SSI between groups did not differ (p=0.27). At 2 wks, warmed patients had better ASEPSIS scores (p=0.04) but this difference was not observed at 6 wks. There were no significant differences in immune, endothelial cell, or collagen responses between groups. On post-operative days one to two, warmed patients had greater PscO2 change scores with an average PscO2 increase of 9-10 mm Hg above baseline (p<0.04).

CONCLUSIONS

Post-operative local warming compared with non-warming followed in this study, which included intra-operative warming to maintain normothermia and FIO2 level of 0.80, did not reduce SSI and had no effect on immune, endothelial cell presence, or collagen synthesis. PscO2 increased significantly with warming, however, the increase was modest and less than expected or what has been observed in studies testing other interventions.

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

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.

High-concentration oxygen and surgical site infections in abdominal surgery: a meta-analysis

BACKGROUND

There has been recent interest in using high-concentration oxygen to prevent surgical site infections (SSIs). Previous meta-analyses in this area have produced conflicting results. With the publication of 2 new randomized controlled trials (RCTs) that were not included in previous meta-analyses, an updated review is warranted. Our objective was to perform a meta-analysis on RCTs comparing high- and low- concentration oxygen in adults undergoing open abdominal surgery.

METHODS

We completed independent literature reviews using electronic databases, bibliographies and other sources of grey literature to identify relevant studies. We assessed the overall quality of evidence using grade guidelines. Statistical analysis was performed on pooled data from included studies. A priori subgroup analyses were planned to explain statistical and clinical heterogeneity.

RESULTS

Overall, 6 studies involving a total of 2585 patients met the inclusion criteria. There was no evidence of a reduction in SSIs with high-concentration oxygen (risk ratio 0.77, 95% confidence interval 0.50-1.19, p = 0.24). We observed substantial heterogeneity among studies.

CONCLUSION

There is moderate evidence that high-concentration oxygen does not reduce SSIs in adults undergoing open abdominal surgery.

Rational use of oxygen in medical disease and anesthesia

PURPOSE OF REVIEW

Supplemental oxygen is often administered during anesthesia and in critical illness to treat hypoxia, but high oxygen concentrations are also given for a number of other reasons such as prevention of surgical site infection (SSI). The decision to use supplemental oxygen is, however, controversial, because of large heterogeneity in the reported results and emerging reports of side-effects. The aim of this article is to review the recent findings regarding benefits and harms of oxygen therapy in anesthesia and acute medical conditions.

RECENT FINDINGS

Large randomized trials have not found significant reductions in SSI with 80% oxygen during and after abdominal surgery and cesarean section. There is no documented benefit of hyperbaric oxygen treatment for acute ischemic stroke, and there is emerging data to suggest increased mortality with normobaric supplemental oxygen for myocardial infarction without heart failure. Survival and neurologic outcome seem to be adversely affected by hyperoxia in patients with return of spontaneous circulation after cardiac arrest.

SUMMARY

The benefits of supplemental oxygen are not yet confirmed, and new findings suggest that potential side-effects should be considered if the inspired oxygen concentration is increased above what is needed to maintain normal arterial oxygen saturation.

Optimizing perioperative care in bariatric surgery patients

Enhanced recovery after surgery (ERAS) programs have been shown to minimise morbidity in other types of surgery, but comparatively less data exist investigating ERAS in bariatric surgery. This article reviews the existing literature to identify interventions which may be included in an ERAS program for bariatric surgery. A narrative literature review was conducted. Search terms included 'bariatric surgery', 'weight loss surgery', 'gastric bypass', 'ERAS', 'enhanced recovery', 'enhanced recovery after surgery', 'fast-track surgery', 'perioperative care', 'postoperative care', 'intraoperative care' and 'preoperative care'. Interventions recovered by the database search, as well as interventions garnered from clinical experience in ERAS, were used as individual search terms. A large volume of evidence exists detailing the role of multiple interventions in perioperative care. However, efficacy and safety for a proportion of these interventions for ERAS in bariatric surgery remain unclear. This review concludes that there is potential to implement ERAS programs in bariatric surgery.

Can anaesthetic technique effect postoperative outcome?

PURPOSE OF REVIEW

Conventional wisdom maintains that multiple aspects of surgical technique and management may affect postoperative outcome, while anaesthetic technique has little long-term effect on patient outcomes. There is accumulating evidence that, on the contrary, anaesthetic management may in fact exert a number of longer-term effects in postoperative outcome. Here, we review the most topical aspects of anaesthetic management which may potentially influence later postoperative outcomes.

RECENT FINDINGS

There is strong evidence that administration of supplemental oxygen and the avoidance of perioperative hypothermia, allogeneic blood transfusion, hyperglycaemia or large swings in blood glucose levels reduces postoperative infection rates. There is also some evidence that the use of regional anaesthesia techniques reduces chronic postsurgical pain and that avoidance of nitrous oxide reduces the long-term risk of myocardial infarction. Current evidence is equivocal regarding the effects of anaesthesia techniques and cancer recurrence. The instigation of perioperative beta-blockade in noncardiac surgery may not reduce perioperative adverse events or improve postoperative cardiovascular risk.

SUMMARY

Further prospective, large-scale human trials with long-term follow-up are required to clarify the association between anaesthesia and cancer recurrence, neurotoxicity and the developing brain and long-term postoperative cognitive dysfunction in the elderly.

[Use of fibrin based biological adhesives in the prevention of anastomotic leaks in the high risk digestive tract: preliminary results of the multicentre, prospective, randomised, controlled, and simple blind phase IV clinical trial: Protissucol001]

INTRODUCTION

A multicentre, prospective, randomised, controlled, and simple blind clinical trial was started in January 2007, with the aim of demonstrating the efficacy of fibrin-based biological adhesives in the prevention of anastomotic leaks in the high risk digestive tract.

MATERIAL AND METHODS

A study on the prevention of anastomotic healing defects by applying biological adhesives along the suture line began in January 2007, and included the hospitals, Gregorio Marañón, Universitario de San Carlos, and Hospital del Sureste, in Madrid. The enrolled patients were randomised to one of 2 groups: the study group in which the adhesive was applied to the suture line, and a control group in which it was not applied. The primary outcome of the study was the presence or absence of leaks. The trial was approved by the corresponding Clinical Research Ethics Committees and the Spanish Medicines Agency (AEMPS) and registered www.clinicaltrials.gov (NCT01306851). The authors declared not to have any conflict of interests with the company, Baxter, which markets the product in Spain.

RESULTS

A total of 104 patients were recruited between January 2007 and November 2010, of whom 52 were randomised to the study group, and 52 to the control group. A total of 22 anastomotic leaks were recorded, of which 7 (13.4%) were in the study group, and 15 (28.8%) in the control group (P=.046). The leak risk index was 0.384, which means that there was a 61% reduction in leaks in the patients who had the fibrin-based biological adhesive applied. There were 3 (5.7%) further surgeries in the study group, compared to 12 (23%) in the control group (P=.12). On analysing the mortality, it was observed that 3 patients in the study group and 4 patients in the control group died (5.7% vs. 7.7%, P=.5). No other significant differences were found as regards the type of suture, surgical time, or pre-surgical history, except that the use of drainages appeared to be a protective factor of anastomotic leak (P=.041), although the use or not of a drainage was not a controlled factor, but at the discretion of each surgeon.

CONCLUSIONS

Our study demonstrates, significantly, that in the 104 patients in the study that fibrin based biological adhesives are capable of preventing anastomotic leaks in the high risk digestive tract, reducing the risk of leaks by 61% and a further surgeries. This is the first clinical trial that shows these significant results. If our results are maintained at the end of the study, it will show that anastomotic leaks can be prevented with the application of these adhesives, thus their application may be recommended in all the anastomosis of the high risk digestive tract.

Postoperative pain management of the obese patient

In the obese patient, the goal of postoperative pain management is provision of comfort, early mobilisation and improved respiratory function without causing inadequate sedation and respiratory compromise. The pathophysiology of obesity, typical co-morbidities and the high prevalence of obstructive sleep apnoea (OSA) amongst obese patients make safe analgesic management difficult. In particular, pain control after bariatric surgery is a major challenge. Although several reviews covering anaesthesia and analgesia for obese patients are published, there is mainly expert opinion and a paucity of evidence-based recommendations. Advice on general management includes multimodal analgesic therapy, preference for regional techniques, avoidance of sedatives, non-invasive ventilation with supplemental oxygen, early mobilisation and elevation of the head of bed to 30 degrees. Finally, with regard to monitoring, sedation scoring is most relevant, but there should be a low threshold for continuous pulse oxymetry, arterial blood pressure measurement and placement in a high-dependency area for the postoperative period.