Surgical Site Infections and Supplemental Perioperative Oxygen in Colorectal Surgery Patients: A Systematic Review

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.

Laparoscopic Nissen fundoplication: The effects of high-concentration supplemental perioperative oxygen on the inflammatory and immune response: A randomised controlled trial

Background

A number of studies have been reported on the effects of high-concentration oxygen (HCO) on cytokine synthesis, with controversial results. We assessed the effect of administration of perioperative HCO on systemic inflammatory and immune response in patients undergoing laparoscopic Nissen fundoplication (LNF).

Materials and Methods

Patients (n = 117) were assigned randomly to an oxygen/air mixture with a fraction of inspired oxygen (FiO₂) of 30% (n = 58) or 80% (n = 59). Administration was commenced after induction of anaesthesia and maintained for 6 h after surgery. White blood cells, peripheral lymphocytes subpopulation, human leucocyte antigen-DR (HLA-DR), neutrophil elastase, interleukin (IL)-1 and IL-6 and C-reactive protein (CRP) were investigated.

Results

A significantly higher concentration of neutrophil elastase, IL-1, IL-6 and CRP was detected post-operatively in the 30% FiO₂group patients in comparison with the 80% FiO₂group (P < 0.05). A statistically significant change in HLA-DR expression was recorded post-operatively at 24 h, as a reduction of this antigen expressed on monocyte surface in patients from 30% FiO₂group; no changes were noted in 80% FiO₂group (P < 0.05).

Conclusions

This study demonstrated that perioperative HCO (80%), during LNF, can lead to a reduction in post-operative inflammatory response, and possibly, avoid post-operative immunosuppression.

Avoidance versus use of neuromuscular blocking agents for improving conditions during tracheal intubation or direct laryngoscopy in adults and adolescents

BACKGROUND

Tracheal intubation during induction of general anaesthesia is a vital procedure performed to secure a patient's airway. Several studies have identified difficult tracheal intubation (DTI) or failed tracheal intubation as one of the major contributors to anaesthesia-related mortality and morbidity. Use of neuromuscular blocking agents (NMBA) to facilitate tracheal intubation is a widely accepted practice. However, because of adverse effects, NMBA may be undesirable. Cohort studies have indicated that avoiding NMBA is an independent risk factor for difficult and failed tracheal intubation. However, no systematic review of randomized trials has evaluated conditions for tracheal intubation, possible adverse effects, and postoperative discomfort.

OBJECTIVES

To evaluate the effects of avoiding neuromuscular blocking agents (NMBA) versus using NMBA on difficult tracheal intubation (DTI) for adults and adolescents allocated to tracheal intubation with direct laryngoscopy. To look at various outcomes, conduct subgroup and sensitivity analyses, examine the role of bias, and apply trial sequential analysis (TSA) to examine the level of available evidence for this intervention.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, BIOSIS, International Web of Science, LILACS, advanced Google, CINAHL, and the following trial registries: Current Controlled Trials; ClinicalTrials.gov; and www.centerwatch.com, up to January 2017. We checked the reference lists of included trials and reviews to look for unidentified trials.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared the effects of avoiding versus using NMBA in participants 14 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 calculated risk ratios (RRs) and their 95% confidence intervals (CIs). 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 included trials. To reduce the risk of random errors caused by sparse data and repetitive updating of cumulative meta-analyses, we applied TSA.

MAIN RESULTS

We identified 34 RCTs with 3565 participants that met our inclusion criteria. All trials reported on conditions for tracheal intubation; seven trials with 846 participants described 'events of upper airway discomfort or injury', and 13 trials with 1308 participants reported on direct laryngoscopy. All trials used a parallel design. We identified 18 dose-finding studies that included more interventions or control groups or both. All trials except three included only American Society of Anesthesiologists (ASA) class I and II participants, 25 trials excluded participants with anticipated DTI, and obesity or overweight was an excluding factor in 13 studies. Eighteen trials used suxamethonium, and 18 trials used non-depolarizing NMBA.Trials with an overall low risk of bias reported significantly increased risk of DTI with no use of NMBA (random-effects model) (RR 13.27, 95% CI 8.19 to 21.49; P < 0.00001; 508 participants; four trials; number needed to treat for an additional harmful outcome (NNTH) = 1.9, I² = 0%, D² = 0%, GRADE = moderate). The TSA-adjusted CI for the RR was 1.85 to 95.04. Inclusion of all trials resulted in confirmation of results and of significantly increased risk of DTI when an NMBA was avoided (random-effects model) (RR 5.00, 95% CI 3.49 to 7.15; P < 0.00001; 3565 participants; 34 trials; NNTH = 6.3, I² = 70%, D² = 82%, GRADE = low). Again the cumulative z-curve crossed the TSA monitoring boundary, demonstrating harmful effects of avoiding NMBA on the proportion of DTI with minimal risk of random error. We categorized only one trial reporting on upper airway discomfort or injury as having overall low risk of bias. Inclusion of all trials revealed significant risk of upper airway discomfort or injury when an NMBA was avoided (random-effects model) (RR 1.37, 95% CI 1.09 to 1.74; P = 0.008; 846 participants; seven trials; NNTH = 9.1, I² = 13%, GRADE = moderate). The TSA-adjusted CI for the RR was 1.00 to 1.85. None of these trials reported mortality. In terms of our secondary outcome 'difficult laryngoscopy', we categorized only one trial as having overall low risk of bias. All trials avoiding NMBA were significantly associated with difficult laryngoscopy (random-effects model) (RR 2.54, 95% CI 1.53 to 4.21; P = 0.0003; 1308 participants; 13 trials; NNTH = 25.6, I² = 0%, D²= 0%, GRADE = low); however, TSA showed that only 6% of the information size required to detect or reject a 20% relative risk reduction (RRR) was accrued, and the trial sequential monitoring boundary was not crossed.

AUTHORS' CONCLUSIONS

This review supports that use of an NMBA may create the best conditions for tracheal intubation and may reduce the risk of upper airway discomfort or injury following tracheal intubation. Study results were characterized by indirectness, heterogeneity, and high or uncertain risk of bias concerning our primary outcome describing difficult tracheal intubation. Therefore, we categorized the GRADE classification of quality of evidence as moderate to low. In light of defined outcomes of individual included trials, our primary outcomes may not reflect a situation that many clinicians consider to be an actual difficult tracheal intubation by which the patient's life or health may be threatened.

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.

Thermoregulation and Risk of Surgical Site Infection

Surgical site infections (SSIs) occur in approximately 2%–5% of patients undergoing surgery in the acute care setting in the United States. These infections result in increased length of stay, higher risk of death, and increased cost of care compared with that in uninfected surgical patients. Given the inclusion of maintenance of perioperative normothermia for all major surgeries as a means of lowering the risk of infection in the Surgical Care Improvement Project 2009, we prepared a summary of the literature to determine the strength and quantity of the evidence underlying the performance measure. Although the data are generally supportive of perioperative normothermia as a means of reducing the risk of SSIs, a more rigorous approach using standard SSI definitions as well as standardized temperature measurements (and timing thereof) will further delineate the role played by temperature regulation in SSI development.

Surgical site infections

Surgical site infections are a major contributor to morbidity and mortality in postsurgical care. Risk for surgical site infection is multifactorial and includes a host of microbial, patient-related, and procedure-related factors. Prevention of surgical infection relies on optimization of patient factors and use of a variety of evidence-based pharmacologic and nonpharmacologic measures. At the forefront of these measures is antimicrobial prophylaxis, which has been shown to be effective at reducing risk of surgical site infection. As guidelines for prevention of surgical site infection become increasingly complex and nuanced, surgical infection outcomes are increasing tied to quality outcome and performances measures.

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.

Obstructive sleep apnea and oxygen therapy: a systematic review of the literature and meta-analysis

BACKGROUND

Hypoxemia is an immediate consequence of obstructive sleep apnea. Oxygen (O2) administration has been used as an alternative treatment in patients with obstructive sleep apnea (OSA) who do not adhere to continuous positive airway pressure (CPAP) in order to reduce the deleterious effects of intermittent hypoxemia during sleep. This systematic review aims to investigate the effects of O2 therapy on patients with OSA.

METHOD

We conducted a systematic search of the databases Medline, Embase, Cochrane Central Register of Controlled Trials (1(st) Quarter 2011), Cochrane Database of Systematic Reviews (from 1950 to February 2011). Our search strategy yielded 4,793 citations. Irrelevant papers were excluded by title and abstract review, leaving 105 manuscripts. We reviewed all prospective studies that included: (1) a target population with obstructive sleep apnea, (2) O2 therapy and/or CPAP as a study intervention, (3) the effects of O2 on the apnea-hypopnea index (AHI), nocturnal hypoxemia, or apnea duration.

RESULTS

We identified 14 studies including a total of 359 patients. Nine studies were of single cohort design, while 5 studies were randomized control trials with 3 groups (CPAP, oxygen, and placebo/sham CPAP). When CPAP was compared to O2 therapy, all but one showed a significant improvement in AHI. Ten studies demonstrated that O2 therapy improved oxygen saturation vs. placebo. However, the average duration of apnea and hypopnea episodes were longer in patients receiving O2 therapy than those receiving placebo.

CONCLUSION

This review shows that O2 therapy significantly improves oxygen saturation in patients with OSA. However, it may also increase the duration of apnea-hypopnea events.

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.

Anesthesia and perioperative management of colorectal surgical patients - specific issues (part 2)

Colorectal surgery carries significant morbidity and mortality, which is associated with an enormous use of healthcare resources. Patients with pre-existing morbidities, and those undergoing emergency colorectal surgery due to complications such as perforation, obstruction, or ischemia / infarction are at an increased risk for adverse outcomes. Fluid therapy in emergency colorectal surgical patients can be challenging as hypovolemic and septic shock may coexist. Abdominal sepsis is a serious complication and may be diagnosed during pre-, intra-, or postoperative periods. Early suspicion and recognition of medical and / or surgical complications are essential. The critical care management of complicated colorectal surgical patients require collaborative and multidisciplinary efforts.

Hyperoxia may be beneficial

The current practice of mechanical ventilation comprises the use of the least inspiratory O2 fraction associated with an arterial O2 tension of 55 to 80 mm Hg or an arterial hemoglobin O2 saturation of 88% to 95%. Early goal-directed therapy for septic shock, however, attempts to balance O2 delivery and demand by optimizing cardiac function and hemoglobin concentration, without making use of hyperoxia. Clearly, it has been well-established for more than a century that long-term exposure to pure O2 results in pulmonary and, under hyperbaric conditions, central nervous O2 toxicity. Nevertheless, several arguments support the use of ventilation with 100% O2 as a supportive measure during the first 12 to 24 hrs of septic shock. In contrast to patients without lung disease undergoing anesthesia, ventilation with 100% O2 does not worsen intrapulmonary shunt under conditions of hyperinflammation, particularly when low tidal volume-high positive end-expiratory pressure ventilation is used. In healthy volunteers and experimental animals, exposure to hyperoxia may cause pulmonary inflammation, enhanced oxidative stress, and tissue apoptosis. This, however, requires long-term exposure or injurious tidal volumes. In contrast, within the timeframe of a perioperative administration, direct O2 toxicity only plays a negligible role. Pure O2 ventilation induces peripheral vasoconstriction and thus may counteract shock-induced hypotension and reduce vasopressor requirements. Furthermore, in experimental animals, a redistribution of cardiac output toward the kidney and the hepato-splanchnic organs was observed. Hyperoxia not only reverses the anesthesia-related impairment of the host defense but also is an antibiotic. In fact, perioperative hyperoxia significantly reduced wound infections, and this effect was directly related to the tissue O2 tension. Therefore, we advocate mechanical ventilation with 100% O2 during the first 12 to 24 hrs of septic shock. However, controlled clinical trials are mandatory to test the safety and efficacy of this approach.

Colectomy for refractory constipation

OBJECTIVE

This study evaluated the type of colectomy, postoperative complications, functional results, and satisfaction in patients with constipation refractory to conservative therapy. Further, colonic transit time (CTT), faecal load (coprostasis), and colon length (redundancies) were compared between operated and non-operated patients.

MATERIAL AND METHODS

Out of 281 patients, 30 women and 5 men underwent surgery. All patients were evaluated by clinical and physiological investigations. Forty-four randomly selected healthy persons constituted the control group.

RESULTS

Twenty-one patients had at hemicolectomy, 11 patients a subtotal colectomy and 3 patients an ileostomy. Two patients had an anastomotic leak and one died. In 11 patients, further surgery was necessary, because of recurrent constipation. Abdominal pain disappeared and defecation patterns improved significantly to 1-4 per day after a colectomy with no uncontrolled diarrhoea. The mean CTT was 65.0 h for patients operated, 37.9 h in non-operated patients and 24.75 h in controls (p < 0.05). Abdominal bloating and pain and defecation parameters correlated significantly positively with CTT and faecal loading, which were significantly increased in operated patients (p < 0.05). The colon was significantly longer in operated patients compared to non-operated, which significantly increased CTT and aggravated symptoms. The histology of the removed colon revealed degenerative changes.

CONCLUSIONS

A segmental or a subtotal colectomy reduced bloating and pain and improved defecation patterns significantly. Although patient satisfaction was rather high, there are significant risks of postoperative complications and future operations. The operated patients had a significant increased CTT, faecal load and colon length, compared to non-operated patients.

Perioperative supplemental oxygen in colorectal patients: a meta-analysis

BACKGROUND

Perioperative supplemental oxygen has been proposed to decrease the incidence of surgical site infection (SSI) in colorectal surgery. A number of randomized controlled trials (RCTs) have been reported with inconsistent results. In addition, relevant clinical outcomes other than SSIs have been collected in these studies and have been equivocal. A meta-analysis of RCTs was performed to elucidate the effects of perioperative supplemental oxygen in colorectal surgery on SSI incidence, mortality, ICU admission, and length of stay.

MATERIALS AND METHODS

A literature search of MEDLINE, PubMed, EMBASE, the Cochrane Library, and the Cochrane Clinical Trials Registry was performed in duplicate. In addition, bibliographic searches were performed, and experts were contacted for unpublished data. RCTs involving colorectal patients that included perioperative supplemental oxygen as a treatment arm and defined SSI as an outcome were included.

RESULTS

Five studies met inclusion criteria. Using a random-effects model, perioperative supplemental oxygen did not significantly reduce SSIs (OR = 0.69, 95% CI [0.43, 1.10], P = 0.12). However, a significant mortality benefit was observed (OR = 0.18, 95% CI [0.05, 0.69], P = 0.01). There was no significant difference in the rate of ICU admission or length of stay. Tests of heterogeneity were performed, and significant heterogeneity was only present with respect to length of stay.

CONCLUSIONS

Perioperative supplemental oxygen in colorectal surgery does not significantly reduce SSI. However, supplemental oxygen appears to confer a mortality benefit, a previously unreported finding. Further RCTs are required to confirm these conclusions.