Perioperative supplemental oxygen in colorectal patients: a meta-analysis

Effects of high versus low inspiratory oxygen fraction on postoperative clinical outcomes in patients undergoing surgery under general anesthesia: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVES

To determine whether high perioperative inspired oxygen fraction (FiO₂) compared with low FiO₂ has more deleterious postoperative clinical outcomes in patients undergoing non-thoracic surgery under general anesthesia.

DESIGN

Meta-analysis of randomized controlled trials.

SETTING

Operating room, postoperative recovery room and surgical ward.

PATIENTS

Surgical patients under general anesthesia.

INTERVENTION

High perioperative FiO₂ (≥0.8) vs. low FiO₂ (≤0.5).

MEASUREMENTS

The primary outcome was mortality within 30 days. Secondary outcomes were pulmonary outcomes (atelectasis, pneumonia, respiratory failure, postoperative pulmonary complications [PPCs], and postoperative oxygen parameters), intensive care unit (ICU) admissions, and length of hospital stay. A subgroup analysis was performed to explore the treatment effect by body mass index (BMI).

MAIN RESULTS

Twenty-six trials with a total 4991 patients were studied. The mortality in the high FiO₂ group did not differ from that in the low FiO₂ group (risk ratio [RR] 0.91, 95% confidence interval [CI] 0.42-1.97, P = 0.810). Nor were there any significant differences between the groups in such outcomes as pneumonia (RR 1.19, 95% CI 0.74-1.92, P = 0.470), respiratory failure (RR 1.29, 95% CI 0.82-2.04, P = 0.270), PPCs (RR 1.05, 95% CI 0.69-1.59, P = 0.830), ICU admission (RR 0.94, 95% CI 0.55-1.60, P = 0.810), and length of hospital stay (mean difference [MD] 0.27 d, 95% CI -0.28-0.81, P = 0.340). The high FiO₂ was associated with postoperative atelectasis more often (risk ratio 1.27, 95% CI 1.00-1.62, P = 0.050), and lower postoperative arterial partial oxygen pressure (MD -5.03 mmHg, 95% CI -7.90- -2.16, P < 0.001)_. In subgroup analysis of BMI >30 kg/m², these parameters were similarly affected between the groups.

CONCLUSIONS

The use of high FiO₂ compared to low FiO₂ did not affect the short-term mortality, although it may increase the incidence of atelectasis in adult, non-thoracic patients undergoing surgical procedures. Nor were there any significant differences in other secondary outcomes.

Effect of Perioperative High Oxygen Concentration on Postoperative SSI in Elective Colorectal Surgery-A Randomized Controlled Trial

BACKGROUND

This study was carried out to investigate the effect of perioperative high oxygen concentration on surgical site infection (SSI) in patients undergoing elective colorectal surgery.

METHODS

This was a single-center, prospective, parallel arm, double-blind, superiority randomized controlled trial. All patients more than 18 years of age undergoing elective colorectal surgery were included as per the inclusion criteria. Patients were randomized at the time of induction of anesthesia into high concentration and standard concentration oxygen group based on the concentration of oxygen. Incidence of SSI, day of the detection of SSI, grade of SSI, incidence of anastomotic leak, postoperative day of return of bowel functions, day of starting oral feeds, day of ambulation, and length of hospitalization were studied in both the groups.

RESULTS

A total of 94 patients were included in the study, 47 patients each in high concentration oxygen group and standard concentration oxygen group respectively. The SSI rates were comparable between the two groups [55.3% (95% CI-4.012-69.83) vs. 40.4% (95% CI-26.37-55.73); p = 0.215]. There was no significant difference found with respect to mean day of detection of SSI [4.5(IQR-3.0-7.5) vs. 6.0 (IQR-3.0-9.0; p = 0.602], postoperative day of return of bowel functions (2.20 ± 0.542 vs. 2.13 ± 0.582; p = 0.540), oral feeds (3.62 ± 0.945 vs. 3.46 ± 1.048; p = 0.544), ambulation (4.17 ± 0.868 vs. 4.17 ± 1.270; p = 0.987), and the length of hospitalization [15(IQR-10-19) vs. 15(IQR-10.75-18.25); p = 0.862] between the two groups.

CONCLUSION

There was no significant difference in the rate of SSI with the use of perioperative high oxygen concentration in patients undergoing elective colorectal 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.

Perioperative high inspired oxygen fraction therapy reduces surgical site infection with Pseudomonas aeruginosa in rats

Surgical site infection (SSI) remains one of the most important causes of healthcare-associated infections, accounting for ~17 % of all hospital-acquired infections. Although short-term perioperative treatment with high fraction of inspired oxygen (FiO2) has shown clinical benefits in reducing SSI in colorectal resection surgeries, the true clinical benefits of FiO2 therapy in reducing SSI remain unclear because randomized controlled trials on this topic have yielded disparate results and inconsistent conclusions. To date, no animal study has been conducted to determine the efficacy of short-term perioperative treatments with high (FiO2>60 %) versus low (FiO2<40 %) oxygen in reducing SSI. In this report, we designed a rat model for muscle surgery to compare the effectiveness of short-term perioperative treatments with high (FiO2=80 %) versus a standard low (FiO2=30 %) oxygen in reducing SSI with Pseudomonas aeruginosa - one of the most prevalent Gram-negative pathogens, responsible for nosocomial SSIs. Our data demonstrate that 5 h perioperative treatment with 80 % FiO2 is significantly more effective in reducing SSI with P. aeruginosa compared to 30 % FiO2 treatment. We further show that whilst 80 % FiO2 treatment does not affect neutrophil infiltration into P. aeruginosa-infected muscles, neutrophils in the 80 % FiO2-treated and infected animal group are significantly more activated than neutrophils in the 30 % FiO2-treated and infected animal group, suggesting that high oxygen perioperative treatment reduces SSI with P. aeruginosa by enhancing neutrophil activation in infected wounds.

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 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.

Systematic review of preoperative, intraoperative and postoperative risk factors for colorectal anastomotic leaks

BACKGROUND

Anastomotic leak (AL) represents a dreaded complication following colorectal surgery, with a prevalence of 1-19 per cent. There remains a lack of consensus regarding factors that may predispose to AL and the relative risks associated with them. The objective was to perform a systematic review of the literature, focusing on the role of preoperative, intraoperative and postoperative factors in the development of colorectal ALs.

METHODS

A systematic review was performed to identify adjustable and non-adjustable preoperative, intraoperative and postoperative factors in the pathogenesis of AL. Additionally, a severity grading system was proposed to guide treatment.

RESULTS

Of 1707 papers screened, 451 fulfilled the criteria for inclusion in the review. Significant preoperative risk factors were: male sex, American Society of Anesthesiologists fitness grade above II, renal disease, co-morbidity and history of radiotherapy. Tumour-related factors were: distal site, size larger than 3 cm, advanced stage, emergency surgery and metastatic disease. Adjustable risk factors were: smoking, obesity, poor nutrition, alcohol excess, immunosuppressants and bevacizumab. Intraoperative risk factors were: blood loss/transfusion and duration of surgery more than 4 h. Stomas lessen the consequences but not the prevalence of AL. In the postoperative period, CT is the most commonly used imaging tool, with or without rectal contrast, and a C-reactive protein level exceeding 150 mg/l on day 3-5 is the most sensitive biochemical marker. A five-level classification system for AL severity and appropriate management is presented.

CONCLUSION

Specific risk factors and their potential correction or indications for stoma were identified. An AL severity score is proposed to aid clinical decision-making.

Perioperative anemia management in colorectal cancer patients: A pragmatic approach

Anemia, usually due to iron deficiency, is highly prevalent among patients with colorectal cancer. Inflammatory cytokines lead to iron restricted erythropoiesis further decreasing iron availability and impairing iron utilization. Preoperative anemia predicts for decreased survival. Allogeneic blood transfusion is widely used to correct anemia and is associated with poorer surgical outcomes, increased post-operative nosocomial infections, longer hospital stays, increased rates of cancer recurrence and perioperative venous thromboembolism. Infections are more likely to occur in those with low preoperative serum ferritin level compared to those with normal levels. A multidisciplinary, multimodal, individualized strategy, collectively termed Patient Blood Management, minimizes or eliminates allogeneic blood transfusion. This includes restrictive transfusion policy, thromboprophylaxis and anemia management to improve outcomes. Normalization of preoperative hemoglobin levels is a World Health Organization recommendation. Iron repletion should be routinely ordered when indicated. Oral iron is poorly tolerated with low adherence based on published evidence. Intravenous iron is safe and effective but is frequently avoided due to misinformation and misinterpretation concerning the incidence and clinical nature of minor infusion reactions. Serious adverse events with intravenous iron are extremely rare. Newer formulations allow complete replacement dosing in 15-60 min markedly facilitating care. Erythropoiesis stimulating agents may improve response rates. A multidisciplinary, multimodal, individualized strategy, collectively termed Patient Blood Management used to minimize or eliminate allogeneic blood transfusion is indicated to improve outcomes.

The prevention of surgical site infection in elective colon surgery

Infections at the surgical site continue to occur in as many as 20% of elective colon resection cases. Methods to reduce these infections are inconsistently applied. Surgical site infection (SSI) is the result of multiple interactive variables including the inoculum of bacteria that contaminate the site, the virulence of the contaminating microbes, and the local environment at the surgical site. These variables that promote infection are potentially offset by the effectiveness of the host defense. Reduction in the inoculum of bacteria is achieved by appropriate surgical site preparation, systemic preventive antibiotics, and use of mechanical bowel preparation in conjunction with the oral antibiotic bowel preparation. Intraoperative reduction of hematoma, necrotic tissue, foreign bodies, and tissue dead space will reduce infections. Enhancement of the host may be achieved by perioperative supplemental oxygenation, maintenance of normothermia, and glycemic control. These methods require additional research to identify optimum application. Uniform application of currently understood methods and continued research into new methods to reduce microbial contamination and enhancement of host responsiveness can lead to better outcomes.

Effect of intraoperative high inspired oxygen fraction on surgical site infection, postoperative nausea and vomiting, and pulmonary function: systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Intraoperative high inspired oxygen fraction (FIO2) is thought to reduce the incidence of surgical site infection (SSI) and postoperative nausea and vomiting, and to promote postoperative atelectasis.

METHODS

The authors searched for randomized trials (till September 2012) comparing intraoperative high with normal FIO2 in adults undergoing surgery with general anesthesia and reporting on SSI, nausea or vomiting, or pulmonary outcomes.

RESULTS

The authors included 22 trials (7,001 patients) published in 26 reports. High FIO2 ranged from 80 to 100% (median, 80%); normal FIO2 ranged from 30 to 40% (median, 30%). In nine trials (5,103 patients, most received prophylactic antibiotics), the incidence of SSI decreased from 14.1% with normal FIO2 to 11.4% with high FIO2; risk ratio, 0.77 (95% CI, 0.59-1.00). After colorectal surgery, the incidence of SSI decreased from 19.3 to 15.2%; risk ratio, 0.78 (95% CI, 0.60-1.02). In 11 trials (2,293 patients), the incidence of nausea decreased from 24.8% with normal FIO2 to 19.5% with high FIO2; risk ratio, 0.79 (95% CI, 0.66-0.93). In patients receiving inhalational anesthetics without prophylactic antiemetics, high FIO2 provided a significant protective effect against both nausea and vomiting. Nine trials (3,698 patients) reported on pulmonary outcomes. The risk of atelectasis was not increased with high FIO2.

CONCLUSIONS

Intraoperative high FIO2 further decreases the risk of SSI in surgical patients receiving prophylactic antibiotics, has a weak beneficial effect on nausea, and does not increase the risk of postoperative atelectasis.

Prevention of surgical site infection in colorectal surgery

SUMMARY The rate of surgical site infection (SSI) for colorectal surgery is among the highest of all operations performed, ranging between 12 and 26% depending on definition applied, surveillance, the prevalence of emergency surgery and the penetration of laparoscopic surgery. With over 135,000 colorectal cancer operations per year, the cost of SSI to the healthcare system are in excess of US$1 billion a year. The Surgical Care Improvement Project (SCIP) has linked hospital reimbursement to compliance with five preventative process measures in colorectal surgery. The success of SCIP in reducing SSI is in doubt, but the addition of other evidence-based measures to SCIP might improve SSI rates. These measures, as well as the contributions of SCIP, are discussed in detail in this review. Implementation of some or all these measures, in addition to SCIP, should be considered by key stakeholders for baseline data collection, monitored for effectiveness and modified as necessary to improve outcomes.

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.

Surgical-site infection after abdominal wall closure with triclosan-impregnated polydioxanone sutures: results of a randomized clinical pathway facilitated trial (NCT00998907)

BACKGROUND

Wound infections after abdominal surgery are still frequent types of nosocomial infections. Suture materials might serve as a vehicle for mechanical transport of bacteria into the surgical wound. To prevent the contamination of suture material in surgical wounds, triclosan-coated suture materials with antibacterial activity was developed. We here report a prospective randomized pathway controlled trial investigating the effect of triclosan impregnation of polydioxanone sutures used for abdominal wall closure on the rate of surgical-site infections.

PATIENTS AND METHODS

A total of 856 patients included in this trial underwent a standardized clinical pathway documented abdominal wall closure after abdominal surgery. Patients were randomized to have the fascia closed with either a 2-0 polydioxanone loop or a triclosan impregnated 2-0 polydioxanone loop. The primary outcome was the number of wound infections. Risk factors for poor wound healing were collected prospectively to compare the two groups.

RESULTS

When a PDS loop suture for abdominal wall closure was used, 42 (11.3%) patients with wound infections were detected. The number of patients with wound infections decreased significantly to 31 when the PDS plus for abdominal wall closure was used (6.4%, P < .05). Other risk factors for the development of side infections were comparably in the two groups.

CONCLUSION

This clinical pathway facilitated trial shows that triclosan impregnation of a 2-0 polydioxanone closing suture can decrease wound infections in patients having a laparotomy for general and abdominal vascular procedures.

Should perioperative supplemental oxygen be routinely recommended for surgery patients? A Bayesian meta-analysis

OBJECTIVE

The purpose of this study is to use updated data and Bayesian methods to evaluate the effectiveness of hyperoxia to reduce surgical site infections (SSIs) and/or mortality in both colorectal and all surgery patients. Because few trials assessed potential harms of hyperoxia, hazards were not included.

BACKGROUND

Use of hyperoxia to reduce SSIs is controversial. Three recent meta-analyses have had conflicting conclusions.

METHODS

A systematic literature search and review were performed. Traditional fixed-effect and random-effect meta-analyses and Bayesian meta-analysis were performed to evaluate SSIs and mortality.

RESULTS

Traditional meta-analysis yielded a relative risk of an SSI with hyperoxia among all surgery patients of 0.84 [95% confidence interval (CI): 0.73-0.97] and 0.84 (95% CI: 0.61-1.16) for the fixed-effect and random-effect models, respectively. The probabilities of any risk reduction in SSIs among all surgery patients were 77%, 81%, and 83% for skeptical, neutral, and enthusiastic priors. The subset analysis of colorectal surgery patients increased the probabilities to 86%, 89%, and 92%. The probabilities of at least a 10% reduction were 57%, 62%, and 68% for all surgery patients and 71%, 75%, and 80% among the colorectal surgery subset.

CONCLUSIONS

There is a moderately high probability of a benefit to hyperoxia in reducing SSIs in colorectal surgery patients; however, the magnitude of benefit is relatively small and might not exceed treatment hazards. Further studies should focus on generalizability to other patient populations or on treatment hazards and other outcomes.

Surgical site infections and their prevention

PURPOSE OF REVIEW

Recent studies have assessed interventions and bundles of interventions to prevent surgical site infections (SSIs). We reviewed numerous studies to identify those with the strongest evidence supporting interventions for preventing SSIs.

RECENT FINDINGS

Bundles that included more than one intervention to decrease the risk of Staphylococcus aureus wound contamination, such as chlorhexidine bathing and nasal application of mupirocin, had the strongest supporting evidence. However, bundles should be tested to ensure that their components are not antagonistic. Vancomycin prophylaxis and extended antimicrobial prophylaxis should not be used routinely, but should be reserved for high-risk populations such as patients who carry methicillin-resistant S. aureus (MRSA). Novel interventions to prevent SSIs (e.g., topical or oral antimicrobial agents, skin sealant, and antimicrobial sutures) need further evaluation before surgeons implement them routinely.

SUMMARY

There is some evidence that bundled interventions can reduce SSIs. However, more research should be done evaluating the effectiveness of these interventions. Future studies of bundles should use robust methodologies, such as randomized controlled trials, cluster randomized trials, or quasi-experimental studies analyzed by time series analysis.

Brief review: theory and practice of minimal fresh gas flow anesthesia

PURPOSE

The aim of this brief review is to provide an update on the theory regarding minimal fresh gas flow techniques for inhaled general anesthesia. The article also includes an update and discussion of the practical aspects associated with minimal-flow anesthesia, including the advantages, potential limitations, and safety considerations of this important anesthetic technique.

PRINCIPAL FINDINGS

Reducing the fresh gas flow to < 1 L·min(-1) during maintenance of anesthesia is associated with several benefits. Enhanced preservation of temperature and humidity, cost savings through more efficient utilization of inhaled anesthetics, and environmental considerations are three key reasons to implement minimal-flow and closed-circuit anesthesia, although potential risks are hypoxic gas mixtures and inadequate depth of anesthesia. The basic elements of the related pharmacology need to be considered, especially pharmacokinetics of the inhaled anesthetics. The third-generation inhaled anesthetics, sevoflurane and desflurane, have low blood and low tissue solubility, which facilitates rapid equilibration between the alveolar and effect site (brain) concentrations and makes them ideally suited for low-flow techniques. The use of modern anesthetic machines designed for minimal-flow techniques, leak-free circle systems, highly efficient CO(2) absorbers, and the common practice of utilizing on-line real-time multi-gas monitor, including essential alarm systems, allow for safe and cost-effective minimal-flow techniques during maintenance of anesthesia. The introduction of new anesthetic machines with built-in closed-loop algorithms for the automatic control of inspired oxygen and end-tidal anesthetic concentration will further enhance the feasibility of minimal-flow techniques.

CONCLUSIONS

With our modern anesthesia machines, reducing the fresh gas flow of oxygen to 0.3-0.5 L·min(-1) and using third-generation inhaled anesthetics provide a reassuringly safe anesthetic technique. This environmentally friendly practice can easily be implemented for elective anesthesia; furthermore, it will facilitate cost savings and improve temperature homeostasis.