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

Effectiveness of supplemental oxygenation to prevent surgical site infections: A systematic review with meta-analysis

OBJECTIVE

to assess the effectiveness of supplemental oxygenation with high FiO2 when compared to conventional FiO2 in the prevention of surgical site infection.

METHOD

an effectiveness systematic review with meta-analysis conducted in five international databases and portals. The research was guided by the following question: Which is the effectiveness of supplemental oxygenation with high FiO2 (greater than 80%) when compared to conventional FiO2 (from 30% to 35%) in the prevention of surgical site infections in adults?

RESULTS

fifteen randomized clinical trials were included. Although all the subgroups presented a general effect in favor of the intervention, colorectal surgeries had this relationship evidenced with statistical significance (I2=10%;X2=4.42; p=0.352).

CONCLUSION

inspired oxygen fractions greater than 80% during the perioperative period in colorectal surgeries have proved to be effective to prevent surgical site infections, reducing their incidence by up to 27% (p=0.006). It is suggested to conduct new studies in groups of patients subjected to surgeries from other specialties, such as cardiac and vascular. PROSPERO registration No.: 178,453.

Optimal anesthetic conduct regarding immediate and short-term outcomes after liver transplantation - Systematic review of the literature and expert panel recommendations

BACKGROUND

In the era of enhanced recovery after surgery, there is significant discussion regarding the impact of intraoperative anesthetic management on short-term outcomes following liver transplantation (LT), with no clear consensus in the literature.

OBJECTIVES

To identify whether or not intraoperative anesthetic management affects short-term outcomes after liver transplantation.

DATA SOURCES

Ovid MEDLINE, Embase, Scopus, Google Scholar, and Cochrane Central.

METHODS

A systematic review following PRISMA guidelines was undertaken. The systematic review was registered on PROSPERO (CRD42021239758). An international expert panel made recommendations for clinical practice using the GRADE approach.

RESULTS

After screening, 14 studies were eligible for inclusion in this systematic review. Six were prospective randomized clinical trials, three were prospective nonrandomized clinical trials, and five were retrospective studies. These manuscripts were reviewed to look at five questions regarding anesthetic care and its impact on short term outcomes following liver transplant. After review of the literature, the quality of evidence according to the following outcomes was as follows: intraoperative and postoperative morbidity and mortality (low), early allograft dysfunction (low), and hospital and ICU length of stay (moderate).

CONCLUSIONS

For optimal short term outcomes after liver transplantation, the panel recommends the use of volatile anesthetics in preference to total intravenous anesthesia (TIVA) (Level of Evidence: Very low; Strength of Recommendation: Weak) and minimum alveolar concentration (MAC) versus bispectral index (BIS) for depth of anesthesia monitoring (Level of Evidence: Very low; Strength of Recommendation: Weak). Regarding ventilation and oxygenation, the panel recommends a restrictive oxygenation strategy targeting a PaO₂ of 70-120 mmHg (10-14 kPa), a tidal volume of 6-8 ml/kg ideal body weight (IBW), administration of positive end expiratory pressure (PEEP) tailored to patient intraoperative physiology, and recruitment maneuvers. (Level of evidence: Very low; Strength of Recommendation: Strong). Finally, the panel recommends the routine use of antiemetic prophylaxis. (Level of evidence: low; Strength of Recommendation: Strong).

Efectividad de la oxigenación suplementaria para prevenir la infección del sitio quirúrgico: revisión sistemática con metaanálisis

Resumen Objetivo: evaluar la efectividad de la oxigenación suplementaria con FiO2 elevada en comparación con la FiO2 convencional para prevenir la infección del sitio quirúrgico. Método: revisión sistemática de eficacia con metaanálisis en cinco bases de datos y portales internacionales. La investigación se guio por la pregunta: ¿Qué tan eficaz es la oxigenación suplementaria con FiO2 alta (más del 80%) en comparación con la FiO2 convencional (del 30 al 35%) para prevenir la infección del sitio quirúrgico en adultos? Resultados: se incluyeron quince ensayos clínicos aleatorizados. Aunque todos los subgrupos mostraron un efecto general a favor de la intervención, en las cirugías colorrectales esa relación tenía significancia estadística (I2=10%; X²=4,42; p=0,352). Conclusión: una fracción inspirada de oxígeno superior al 80% durante el perioperatorio en cirugías colorrectales ha demostrado ser eficaz en la prevención de la infección del sitio quirúrgico, reduciendo su incidencia hasta en un 27% (p=0,006). Se sugiere realizar más estudios en grupos de pacientes sometidos a cirugías en otras especialidades, como cardiaca y vascular. Registro PROSPERO: 178453.

Comparison of Intra-operative Pressure-Controlled Ventilation and Volume-Controlled Ventilation in Bariatric Surgery: A Prospective Randomized Study

Background: Mechanical ventilation may be particularly challenging in obese patients undergoing laparoscopic bariatric surgery. The present study aimed to compare the effects of pressure-controlled ventilation (PCV) with those of volume-controlled ventilation (VCV) on peripheral tissue oxygenation (PTO), respiratory function, hemodynamic status, and ventilation-related complications in patients undergoing laparoscopic bariatric surgery.

Methods: A total of 100 patients with obesity who underwent gastric plication or sleeve gastrectomy were recruited for the study, and 60 patients (n=32, in group PCV; n=28, in group VCV) were ultimately enrolled. Data on peri-operative PTO (arterial blood gas [ABG] analysis and tissue oxygen saturation [StO₂]) and respiratory functions were recorded for each patient, along with post-operative hemodynamic status, fluid intake, urinary output, Numeric Pain Rating Scale (NPRS) score , and complications.

Results: The two groups were similar in pH, partial pressure of oxygen, partial pressure of carbon dioxide, oxygen saturation, and lactate values at baseline, intra-operative and post-operative periods. The peri-operative StO₂ values were also similar between the two groups at all times. The two groups were identical in terms of preoperative values for respiratory function tests and post-operative hemodynamic status, fluid intake, urinary output, pain scores, and complication rates.

Conclusions: In conclusion, the choice of the mechanical ventilation mode did not appear to influence oxygen delivery, respiratory function, hemodynamic status, post-operative pain, or ventilation-related complications in obese patients undergoing laparoscopic bariatric surgery.

Intra-Operative Inspired Fraction of Oxygen and the Risk of Surgical Site Infections in Patients with Type 1 Surgical Incisions

BACKGROUND

Whether the fraction of inspired oxygen (F_IO₂) influences the risk of surgical site infection (SSI) is controversial. The World Health Organization and the World Federation of Societies of Anesthesiologists offer conflicting recommendations. In this study, we evaluate simultaneously three different definitions of F_IO₂ exposure and the risk of SSI in a large surgical population.

PATIENTS AND METHODS

Patients with clean (type 1) surgical incisions who developed superficial and deep organ/space SSI within 30 days after surgery from January 2003 through December 2012 in five surgical specialties were matched to specialty-specific controls. Fraction of inspired oxygen exposure was defined as (1) nadir F_IO₂, (2) percentage of operative time with F_IO₂ greater than 50%, and (3) cumulative hyperoxia exposure, calculated as the area under the curve (AUC) of F_IO₂ by time for the duration in which F_IO₂ greater than 50%. Stratified univariable and multivariable logistic regression models tested associations between F_IO₂ and SSI.

RESULTS

One thousand two hundred fifty cases of SSI were matched to 3,248 controls. Increased oxygen exposure, by any of the three measures, was not associated with the outcome of any SSI in a multivariable logistic regression model. Elevated body mass index (BMI; 35+ vs. <25, odds ratio [OR] 1.78, 95% confidence interval [CI] 1.43-2.24), surgical duration (250+ min vs. <100 min, OR 1.93, 95% CI 1.48-2.52), diabetes mellitus (OR 1.37, 95% CI 1.13-1.65), peripheral vascular disease (OR 1.52, 95% CI 1.10-2.10), and liver cirrhosis (OR 2.48, 95% CI 1.53-4.02) were statistically significantly associated with greater odds of any SSI. Surgical sub-group analyses found higher intra-operative oxygen exposure was associated with higher odds of SSI in the neurosurgical and spine populations.

CONCLUSION

Increased intra-operative inspired fraction of oxygen was not associated with a reduction in SSI. These findings do not support the practice of increasing F_IO₂ for the purpose of SSI reduction in patients with clean surgical incisions.

Oxygen therapies and their effects on wound healing

Oxygen is an important factor for wound healing. Although several different therapies investigated the use of oxygen to aid wound healing, the results of these studies are not unequivocal. This systematic review summarizes the clinical and experimental studies regarding different oxygen therapies for promoting wound healing, and evaluates the outcomes according the methodological details. A systematic literature search was conducted using Embase, Medline, Web of Science, Cochrane, PubMed publisher, and Google Scholar libraries. Clinical and experimental studies investigating oxygen for wound healing were selected. Included articles were categorized according to the kind of therapy, study design, and wound type. The methodological details were extracted and analyzed. Sixty-five articles were identified and divided in three different oxygen therapies: Local oxygen therapy, hyperbaric oxygen therapy, and supplemental inspired oxygen therapy. More than half of the included local oxygen and hyperbaric oxygen studies had one or more significant positive outcomes, 77 and 63%, respectively. Supplemental inspired oxygen therapy during gastrointestinal and vascular surgery was more likely to have a positive result than during other surgical interventions reducing surgical site infections. These many positive outcomes promote the use of oxygen treatment in the stimulation of wound healing. However, the lack of clinical studies and vast methodological diversity made it impossible to perform a proper comparison within and between the different therapies. Further randomized clinical studies are warranted to examine the value of these therapies, especially studies that investigate the more patient-friendly oxygen dressings and topical wound oxygen therapies. Also, to achieve more solid and consistent data, studies should use more standardized methods and subjects.

A Critical Analysis of Perioperative Outcomes in Morbidly Obese Patients Following Renal Mass Surgery

OBJECTIVE

To evaluate if body mass index (BMI) ≥ 40 is associated with risk of postoperative complications, receipt of perioperative blood transfusion (PBT), length of hospital stay (LOS), perioperative death, or hospital readmission rate following renal mass surgery.

MATERIALS AND METHODS

After Institutional Review Board approval, comprehensive information was collected for patients treated with surgery for renal mass from 2000 to 2015 at one institution. Univariable and multivariable analyses were used to evaluate the association of BMI ≥ 40 among other putative risk factors for perioperative outcomes.

RESULTS

A total of 1048 patients were treated surgically, including 115 (11%) with BMI > 40. Minimally invasive and open surgical approaches were used for 480 (45.8%) and 568 (54.2%) patients, respectively. Morbid obesity was not associated with risk of major complications, overall complications, receipt of PBT, LOS, hospital readmission rate, or perioperative death. Charlson comorbidity index was the only independent predictor of major complications following renal mass surgery, P = .0006, per point odds ratio 1.2 (95%C.I. 1.08-1.32). Surgical site infections (SSIs) were more common in patients with BMI ≥ 40 vs BMI < 40 (10.5% vs 4.8%, P = .01). Following multivariable analysis, BMI ≥ 40 was the only independent predictor of SSIs, odds ratio 2.6, 95% confidence interval 1.32-5.13; P = .006.

CONCLUSION

Morbid obesity (BMI ≥ 40) is an independent predictor of developing SSIs following renal mass surgery. Morbid obesity is not predictive of risk for major complications, receipt of PBT, hospital readmission, perioperative death, or LOS.

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.