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. Anesthesiology. 2013;119:303-316. [PMID: 23719611 DOI: 10.1097/aln.0b013e31829aaff4]

Effects of high vs. low perioperative inspired oxygen fraction on length of hospital stay and postoperative complications: a systematic review, meta-analysis, and trial sequential analysis

INTRODUCTION

Prolonged length of hospital stay (LOS) and postoperative complications in surgical patients are major public health issues worldwide. Perioperative hyperoxia may increase LOS, and the incidence of cardiac, cerebral, renal, and pulmonary injury; however, the supporting clinical evidence is controversial. Therefore, the current meta-analysis included all relevant randomized controlled trials (RCTs) to investigate the effect of high and low inspired oxygen fraction (FiO2) on LOS, according to postoperative complications.

EVIDENCE ACQUISITION

Standard published RCTs were searched from bibliographic databases to identify all evidence reporting perioperative FiO2 for patients undergoing surgeries. The primary outcome was LOS, and the secondary outcomes were postoperative organ complications, surgical site infection (SSI), and postoperative mortality. The relative risk (RR) and Peto-odds ratio (Peto-OR) for dichotomous outcomes and the mean difference (MD) and standardized mean difference (SMD) for continuous outcomes were estimated using a random-effects model. Trial sequential analysis (TSA) was performed in the meta-analysis to evaluate the required information sizes and assess whether the primary outcome in our meta-analysis was conclusive.

EVIDENCE SYNTHESIS

Thirty-one RCTs with 10506 participants undergoing different surgeries were included. The LOS in the high FiO2 group did not differ significantly from that in the low FiO2 group (MD -0.01, 95% CI -0.10 to 0.08, P=0.81). Moreover, we found no meaningful evidence of subgroup differences in the primary outcome, in comparisons of FiO2, RCT type, surgery type, duration of oxygen inhalation or timing of oxygen inhalation. TSA results further suggested that the number of included studies was sufficient for the primary outcome. There was also no significant difference in postoperative organ complications (cardiac, cerebral, renal, and pulmonary), SSI (rate of SSI, ASEPSIS score, and ASEPSIS score > 20 cases), or postoperative mortality. For postoperative atelectasis, sensitivity analysis showed that after exclusion of one study, "Myles 2007," high FiO2 was associated with increased postoperative atelectasis.

CONCLUSIONS

The use of low FiO2 has no effect on LOS, or the incidence of cardiac, cerebral, and renal injury or postoperative mortality. Compared with low FiO2, high FiO2 did not reduce SSI which was contrary to the guidelines. Meanwhile, high FiO2 may increase postoperative atelectasis in surgical patients.

Perioperative oxygen administration for adults undergoing major noncardiac surgery: a narrative review

Perioperative oxygen administration, a topic under continuous research and debate in anesthesiology, strives to optimize tissue oxygenation while minimizing the risks associated with hyperoxia and hypoxia. This review provides a thorough overview of the current evidence on the application of perioperative oxygen in adult patients undergoing major noncardiac surgery. The review begins by describing the physiological reasoning for supplemental oxygen during the perioperative period and its potential benefits while also focusing on potential hyperoxia risks. This review critically appraises the existing literature on perioperative oxygen administration, encompassing recent clinical trials and meta-analyses, to elucidate its effect on postoperative results. Future research should concentrate on illuminating the optimal oxygen administration strategies to improve patient outcomes and fine-tune perioperative care protocols for adults undergoing major noncardiac surgery. By compiling and analyzing available evidence, this review aims to provide clinicians and researchers with comprehensive knowledge on the role of perioperative oxygen administration in major noncardiac surgery, ultimately guiding clinical practice and future research endeavors.

The association of vaping and electronic cigarette use with postoperative hypoxemia and respiratory complications: a retrospective cohort analysis

PURPOSE

Initially introduced as a safer alternative to smoking, electronic cigarettes (e-cigarettes) and vaping have since been associated with lung injury. Nevertheless, there is limited perioperative data on their potential contribution to the harmful effects of mechanical ventilation on the lungs. We hypothesized that, in adults undergoing noncardiothoracic surgeries, preoperative vaping/e-cigarette use is associated with hypoxemia during the first postoperative hour, and with an increased incidence of intraoperative and postoperative pulmonary complications.

METHODS

We conducted a retrospective cohort study in which we included patients reporting as vapers/e-cigarette users within one year before surgery as the exposure group, and nonvapers as the control group. The primary outcome was the time-weighted average (TWA) SpO2/FIO2 ratio in the postanesthesia care unit during the first postoperative hour. The secondary outcome was a composite of intraoperative and postoperative pulmonary complications until discharge. We used entropy balancing to adjust for confounding, and fit weighted linear regression and logistic regression models to estimate treatment effects.

RESULTS

A total of 110,940 patients met the inclusion criteria, and 1,941 of these were vapers/e-cigarette users. The average treatment effect on the treated for TWA SpO2/FIO2 ratio (N = 109,217) was estimated to be a mean difference of 4 (95% confidence interval [CI], 1 to 8; P = 0.007). This is equivalent to a 4% change in SpO2 at a 30% FIO2 (or at a fixed FIO2). The difference was statistically significant. The average treatment effect on the treated for experiencing intraoperative and postoperative pulmonary complications (N = 110,940) was an odds ratio of 1.04 (95% CI, 0.71 to 1.54; P = 0.84).

CONCLUSION

Vaping/e-cigarette use was neither associated with clinically significant hypoxemia during the first hour in the postanesthesia care unit nor with an increase in pulmonary complications. Nevertheless, our findings cannot definitively exclude the deleterious effects of vaping and e-cigarette use on the lungs, and anesthesiologists should consider potential perioperative complications.

Higher fraction of inspired oxygen during anesthesia increase the risk of postoperative pulmonary complications in patients undergoing non-cardiothoracic surgery: a retrospective cohort study

Objective

The ideal intra-operative inspired oxygen concentration remains controversial. We aimed to investigate the association between the intraoperative fraction of inspired oxygen (FiO2) and the incidence of postoperative pulmonary complications (PPCs) in patients undergoing non-cardiothoracic surgery.

Methods

This was a retrospective cohort study of elderly patients who underwent non-cardiothoracic surgery between April 2020 and January 2022. According to intraoperative FiO2, patients were divided into low (≤60%) and high (>60%) FiO2 groups. The primary outcome was the incidence of a composite of pulmonary complications (PPCs) within the first seven postoperative days. Propensity score matching (PSM) and inverse probability treatment weighting (IPTW) were conducted to adjust for baseline characteristic differences between the two groups. Multivariate logistic regression analysis was used to calculate the odds ratios (OR) for FiO2 and PPCs.

Results

Among the 3,515 included patients with a median age of 70 years (interquartile range: 68-74), 492 (14%) experienced PPCs within the first 7 postoperative days. Elevated FiO2 was associated with an increased risk of PPCs in all the logistic regression models. The OR of the FiO2 > 60% group was 1.252 (95%CI, 1.015-1.551, P = 0.038) in the univariate analysis. In the multivariate logistic regression models, the ORs of the FiO2 > 60% group were 1.259 (Model 2), 1.314 (Model 3), and 1.32 (model 4). A balanced covariate distribution between the two groups was created using PSM or IPTW. The correlation between elevated FiO2 and an increased risk of PPCs remained statistically significant with PSM analysis (OR, 1.393; 95% CI, 1.077-1.804; P = 0.012) and IPTW analysis (OR, 1.266; 95% CI, 1.086-1.476; P = 0.003).

Conclusion

High intraoperative FiO2 (>60%) was associated with the postoperative occurrence of pulmonary complications, independent of predefined risk factors, in elderly non-cardiothoracic surgery patients. High intraoperative FiO2 should be applied cautiously in surgical patients vulnerable to PPCs.

The effect of intraoperative goal-directed fluid therapy in patients under anesthesia for gastrointestinal surgery

BACKGROUND

Intraoperative fluid management is an important aspect of anesthesia management in gastrointestinal surgery. Intraoperative goal-directed fluid therapy (GDFT) is a method for optimizing a patient's physiological state by monitoring and regulating fluid input in real-time.

AIM

To evaluate the efficacy of intraoperative GDFT in patients under anesthesia for gastrointestinal surgery.

METHODS

This study utilized a retrospective comparative study design and included 60 patients who underwent gastrointestinal surgery at a hospital. The experimental group (GDFT group) and the control group, each comprising 30 patients, received intraoperative GDFT and traditional fluid management strategies, respectively. The effect of GDFT was evaluated by comparing postoperative recovery, complication rates, hospitalization time, and other indicators between the two patient groups.

RESULTS

Intraoperative blood loss in the experimental and control groups was 296.64 ± 46.71 mL and 470.05 ± 73.26 mL (P < 0.001), and urine volume was 415.13 ± 96.72 mL and 239.15 ± 94.69 mL (P < 0.001), respectively. The postoperative recovery time was 5.44 ± 1.1 days for the experimental group compared to 7.59 ± 1.45 days (P < 0.001) for the control group. Hospitalization time for the experimental group was 10.87 ± 2.36 days vs 13.65 ± 3 days for the control group (P < 0.001). The visual analogue scale scores of the experimental and control groups at 24 h and 48 h post-surgery were 3.38 ± 0.79 and 4.51 ± 0.86, and 2.05 ± 0.57 and 3.51 ± 0.97 (P < 0.001), respectively. The cardiac output of the experimental and control groups was 5.99 ± 1.04 L/min and 4.88 ± 1.17 L/min, respectively, while the pulse pressure variability for these two groups was 10.87 ± 2.36% and 17.5 ± 3.21%, respectively.

CONCLUSION

The application of GDFT in gastrointestinal surgery can significantly improve postoperative recovery, reduce the incidence of complications, and shorten hospital stays.

Effect of perioperative sigh ventilation on postoperative hypoxemia and pulmonary complications after on-pump cardiac surgery (E-SIGHT): study protocol for a randomized controlled trial

BACKGROUND

Postoperative hypoxemia and pulmonary complications remain a frequent event after on-pump cardiac surgery and mostly characterized by pulmonary atelectasis. Surfactant dysfunction or hyposecretion happens prior to atelectasis formation, and sigh represents the strongest stimulus for surfactant secretion. The role of sigh breaths added to conventional lung protective ventilation in reducing postoperative hypoxemia and pulmonary complications among cardiac surgery is unknown.

METHODS

The perioperative sigh ventilation in cardiac surgery (E-SIGHT) trial is a single-center, two-arm, randomized controlled trial. In total, 192 patients scheduled for elective cardiac surgery with cardiopulmonary bypass (CPB) and aortic cross-clamp will be randomized into one of the two treatment arms. In the experimental group, besides conventional lung protective ventilation, sigh volumes producing plateau pressures of 35 cmH2O (or 40 cmH2O for patients with body mass index > 35 kg/m2) delivered once every 6 min from intubation to extubation. In the control group, conventional lung protective ventilation without preplanned recruitment maneuvers is used. Lung protective ventilation (LPV) consists of low tidal volumes (6-8 mL/kg of predicted body weight) and positive end-expiratory pressure (PEEP) setting according to low PEEP/FiO2 table for acute respiratory distress syndrome (ARDS). The primary endpoint is time-weighted average SpO2/FiO2 ratio during the initial post-extubation hour. Main secondary endpoint is the severity of postoperative pulmonary complications (PPCs) computed by postoperative day 7.

DISCUSSION

The E-SIGHT trial will be the first randomized controlled trial to evaluate the impact of perioperative sigh ventilation on the postoperative outcomes after on-pump cardiac surgery. The trial will introduce and assess a novel perioperative ventilation approach to mitigate the risk of postoperative hypoxemia and PPCs in patients undergoing cardiac surgery. Also provide the basis for a future larger trial aiming at verifying the impact of sigh ventilation on postoperative pulmonary complications.

TRIAL REGISTRATION

ClinicalTrials.gov NCT06248320. Registered on January 30, 2024. Last updated February 26, 2024.

Oxygenation during general anesthesia in pediatric patients: A retrospective observational study

STUDY OBJECTIVE

Protocols are used in intensive care and emergency settings to limit the use of oxygen. However, in pediatric anesthesiology, such protocols do not exist. This study aimed to investigate the administration of oxygen during pediatric general anesthesia and related these values to PaO2, SpO2 and SaO2.

DESIGN

Retrospective observational study.

SETTING

Tertiary pediatric academic hospital, from June 2017 to August 2020.

PATIENTS

Patients aged 0-18 years who underwent general anesthesia for a diagnostic or surgical procedure with tracheal intubation and an arterial catheter for regular blood withdrawal were included. Patients on cardiopulmonary bypass or those with missing data were excluded. Electronic charts were reviewed for patient characteristics, type of surgery, arterial blood gas analyses, and oxygenation management.

INTERVENTIONS

No interventions were done.

MEASUREMENTS

Primary outcome defined as FiO2, PaO2 and SpO2 values were interpreted using descriptive analyses, and the correlation between PaO2 and FiO2 was determined using the weighted Spearman correlation coefficient.

MAIN RESULTS

Data of 493 cases were obtained. Of these, 267 were excluded for various reasons. Finally, 226 cases with a total of 645 samples were analyzed. The median FiO2 was 36% (IQR 31 to 43), with a range from 20% to 97%, and the median PaO2 was 23.6 kPa (IQR 18.6 to 28.1); 177 mmHg (IQR 140 to 211). The median SpO2 level was 99% (IQR 98 to 100%). The study showed a moderately positive association between PaO2 and FiO2 (r = 0.52, p < 0.001). 574 of 645 samples (89%) contained a PaO2 higher than 13.3 kPa; 100 mmHg.

CONCLUSIONS

Oxygen administration during general pediatric anesthesia is barely regulated. Hyperoxemia is observed intraoperatively in approximately 90% of cases. Future research should focus on outcomes related to hyperoxemia.

Effects of different fractions of inspired oxygen on gas embolization during hysteroscopic surgery: A double-blind, randomized, controlled trial

OBJECTIVE

Gas embolism is a common complication of hysteroscopic surgery that causes serious concern among gynecologists and anesthesiologists due to the potential risk to patients. The factors influencing gas embolism in hysteroscopic surgery have been extensively studied. However, the effect of the oxygen concentration inhaled by patients on gas embolism during hysteroscopic surgery remains elusive. Therefore, we designed a double-blind, randomized, controlled trial to determine whether different inhaled oxygen concentrations influence the occurrence of gas embolism during hysteroscopic surgery.

METHODS

This trial enrolled 162 adult patients undergoing elective hysteroscopic surgery who were randomly divided into three groups with inspired oxygen fractions of 30%, 50%, and 100%. Transthoracic echocardiography (four-chamber view) was used to evaluate whether gas embolism occurred. Before the start of surgery, the four-chamber view was continuously monitored.

RESULTS

The number of gas embolisms in the 30%, 50%, and 100% groups was 36 (69.2%), 30 (55.6%), and 24 (44.4%), respectively. The incidence of gas embolism gradually decreased with increasing inhaled oxygen concentration (P = 0.031).

CONCLUSION

In hysteroscopic surgery, a higher oxygen concentration inhaled by patients may reduce the incidence of gas embolism, indicating that a higher inhaled oxygen concentration, especially 100%, could be recommended for patients during hysteroscopic surgery.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (https://www.chictr.org.cn/showproj.html?proj=53779, Registration number: ChiCTR2000033202).

Postoperative pulmonary complications with high versus standard FiO2 in adult patients undergoing major abdominal surgery: A noninferiority trial

BACKGROUND

Despite the possible clinical benefit of high intraoperative oxygen therapy on surgical site infection, the effect on postoperative respiratory function is debatable. However, it remains yet to be elucidated whether hyperoxia due to a high fraction of inspired oxygen used in conjunction with lung protective ventilation can lead to increased incidence of postoperative pulmonary complications.

METHODS

In this noninferiority randomized trial, an intraoperative high fraction of inspired oxygen of 0.8 (group H) was compared to a standard fraction of inspired oxygen of 0.3 to 0.4 (group S) in adult patients undergoing major elective or emergency surgery. A lung protective ventilation strategy was employed in all patients, including volume control ventilation with a tidal volume of 6 to 8 mL/kg of predicted body weight, respiratory rate of 12 beats per minute, and positive end-expiratory pressure of 5 to 8 cm H2O. Postoperative pulmonary complications were assessed on postoperative days 3 and 5 by the Melbourne group scale.

RESULTS

In this trial, n = 226 patients were randomized; among them, 130 patients underwent routine surgery, and 96 patients underwent emergency surgery. The median (interquartile range) of the patients was 48 (35-58) years, and 47.3% were female. Melbourne group scale scores at postoperative day 3 (median [interquartile range] 2 [1-4] in group S vs 2 [1-3] in group H; the difference in median [95% confidence interval] 0 [0, -1]; P = .13) and day 5 (median [interquartile range] 1 (0-3) in group S vs 1 [0-3] in group H; the difference in median [95% confidence interval] 0 [0, 0.5]; P = .34) were statistically similar in both the groups and the upper margin was within the predefined margin of 1. Incidence of surgical site infection (P = .46), postoperative hospital stay (P = .29), and days alive without antibiotic therapy at postoperative day 28 (P = .95) were similar in both groups.

CONCLUSION

High intraoperative fiO2 was noninferior to standard fiO2 in postoperative pulmonary complications in adult patients undergoing major surgery.

PCV-VG combined individualized PEEP determination in one-lung ventilated patients with PEEP step change direction: A randomized controlled trial

INTRODUCTION

The efficacy of pressure-controlled volume-guaranteed ventilation (PCV-VG) combined with a gradient-directional change in positive end-expiratory pressure (PEEP) during one-lung ventilation (OLV) in patients who underwent thoracoscopic surgery was investigated.

METHODS

Ninety patients were randomly divided into the PC (PCV-VG + 5 cm H2 O fixed PEEP), PI (PCV-VG + incremental PEEP titration), and PD (PCV-VG + decremental PEEP titration) groups. Hemodynamic (heart rate [HR] and mean arterial pressure [MAP]), respiratory mechanics (Ppeak , Pmean, and Cdyn), and arterial blood gas (pH, PaCO2 , PaO2 , and PaO2 /FiO2 ) indices were evaluated at T1 (10 min of two-lung ventilation [TLV]), T2 (10 min of OLV), and T3 (10 min of recovery, TLV). Enzyme-linked immunosorbent assay was performed to detect neutrophil elastase (NE), clara cell secretory protein (CC16), and interleukin-8 (IL-8) levels at T1 and T3.

RESULTS

At T2 and T3 , Ppeak was lower in the PI and PD groups than in the PC group, while Pmean and Cdyn were higher than in the PC group. Ppeak in the PD group was lower than that in the PI group; however, Pmean was higher at T2 and T3 (P < 0.05). At T2 , PaO2 and PaO2 /FiO2 were higher, but PaO2 /FiO2 and VD /VT were lower in the PD and PI groups than in the PC group (P < 0.05). NE, CC16, IL-6, and IL-8 levels were elevated in all three groups at T3 , but the PI and PD groups had lower levels than the PC group (P < 0.05). The incidences of postoperative pulmonary complications (PPCs) and surgical intensive care unit hospitalizations in the PD and PI groups were much lower.

CONCLUSION

Gradient-directed altered PEEP titration could improve respiratory mechanics, arterial blood gases, and inflammatory responses and reduce the incidence of PPCs in patients undergoing thoracoscopic surgery.

[Perioperative hyperoxia-More harmful than beneficial?]

BACKGROUND

The ideal perioperative oxygen concentration is controversial and study results are inconsistent.

OBJECTIVE

Current knowledge on the beneficial and adverse effects of perioperative hyperoxia.

MATERIAL AND METHODS

Narrative review RESULTS: Perioperative hyperoxia is unlikely to increase the incidence of atelectasis, pulmonary or cardiovascular complications or mortality. Few and small potential beneficial effects, such as reduction of surgical wound infections or postoperative nausea and vomiting have been demonstrated. According to the current state of evidence, it is recommended to avoid perioperative hyperoxia and to aim for normoxia instead.

Postoperative Respiratory Failure and Advanced Ventilator Settings

Postoperative respiratory failure has a multifactorial etiology, of which atelectasis is the most common mechanism. Its injurious effects are magnified by surgical inflammation, high driving pressures, and postoperative pain. Chest physiotherapy and noninvasive ventilation are good options to prevent progression of respiratory failure. Acute respiratory disease syndrome is a late and severe finding, which is associated with high morbidity and mortality. If present, proning is a safe, effective, and underutilized therapy. Extracorporeal membrane oxygenation is an option only when traditional supportive measures have failed.

Perioperative Supplemental Oxygen and Postoperative Nausea and Vomiting: Subanalysis of a Trial, Systematic Review, and Meta-analysis

BACKGROUND

Intraoperative supplemental oxygen may reduce postoperative nausea and vomiting by mitigating hypoxic stress on the gastrointestinal tract. The authors therefore tested the hypothesis that supplemental oxygen reduces nausea and vomiting in adults recovering from colorectal surgery at the Cleveland Clinic between January 28, 2013, and March 11, 2016.

METHODS

Initially, the authors conducted an unplanned subanalysis of a previous trial that evaluated the effect of 80% versus 30% intraoperative inspired oxygen on surgical site infection. Specifically, they assessed the effect of 80% versus 30% oxygen concentration on the incidence of postoperative nausea and/or vomiting. Thereafter, the authors conducted a systematic review and meta-analysis of the effect of supplemental oxygen on postoperative nausea and vomiting.

RESULTS

The authors' underlying analysis included 5,057 colorectal surgeries on 4,001 patients. For 2,554 surgeries, assignment was to 80% oxygen, and in 2,503 surgeries, to 30%. Postoperative nausea and vomiting was 852 of 2,554 (33%) in 80% oxygen and 814 of 2,503 (33%) in 30% oxygen. The estimated relative risk (95% CI) of 80% versus 30% oxygen on postoperative nausea and vomiting was 1.04 (0.96 to 1.12) in a generalized estimating equation model adjusting for within-patient correlation for patients with multiple surgeries, P = 0.355. Furthermore, supplemental oxygen did not reduce antiemetic use (P = 0.911) or the severity of nausea and vomiting (P = 0.924). The authors' meta-analysis included 10 qualifying trials (6,749 patients) and did not find a difference in postoperative nausea and vomiting: relative risk, 0.97 [95% CI, 0.86 to 1.08], P = 0.55, I2 = 52%.

CONCLUSIONS

The incidence of postoperative nausea and vomiting did not differ in patients assigned to 80% or 30% inspired oxygen. A meta-analysis of available trials similarly indicated that supplemental intraoperative oxygen does not reduce postoperative nausea and vomiting. Therefore, supplemental oxygen should not be given in the expectation that it will reduce nausea and vomiting.

EDITOR’S PERSPECTIVE

Practice of oxygen use in anesthesiology – a survey of the European Society of Anaesthesiology and Intensive Care

Background

Oxygen is one of the most commonly used drugs by anesthesiologists. The World Health Organization (WHO) gave recommendations regarding perioperative oxygen administration, but the practice of oxygen use in anesthesia, critical emergency, and intensive care medicine remains unclear.

Methods

We conducted an online survey among members of the European Society of Anaesthesiology and Intensive Care (ESAIC). The questionnaire consisted of 46 queries appraising the perioperative period, emergency medicine and in the intensive care, knowledge about current recommendations by the WHO, oxygen toxicity, and devices for supplemental oxygen therapy.

Results

Seven hundred ninety-eight ESAIC members (2.1% of all ESAIC members) completed the survey. Most respondents were board-certified and worked in hospitals with > 500 beds. The majority affirmed that they do not use specific protocols for oxygen administration. WHO recommendations are unknown to 42% of respondents, known but not followed by 14%, and known and followed by 24% of them. Respondents prefer inspiratory oxygen fraction (FiO₂) ≥80% during induction and emergence from anesthesia, but intraoperatively < 60% for maintenance, and higher FiO₂ in patients with diseased than non-diseased lungs. Postoperative oxygen therapy is prescribed more commonly according to peripheral oxygen saturation (SpO₂), but shortage of devices still limits monitoring. When monitoring is used, SpO₂ ≤ 95% is often targeted. In critical emergency medicine, oxygen is used frequently in patients aged ≥80 years, or presenting with respiratory distress, chronic obstructive pulmonary disease, myocardial infarction, and stroke. In the intensive care unit, oxygen is mostly targeted at 96%, especially in patients with pulmonary diseases.

Conclusions

The current practice of perioperative oxygen therapy among respondents does not follow WHO recommendations or current evidence, and access to postoperative monitoring devices impairs the individualization of oxygen therapy. Further research and additional teaching about use of oxygen are necessary.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-022-01884-2.

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.

Perioperative oxygen therapy: a protocol for an overview of systematic reviews and meta-analyses

BACKGROUND

Oxygen is routinely given to patients during and after surgery. Perioperative oxygen administration has been proposed as a potential strategy to prevent and treat hypoxaemia and reduce complications, such as surgical site infections, pulmonary complications and mortality. However, uncertainty exists as to which strategies in terms of amount, delivery devices and timing are clinically effective. The aim of this overview of systematic reviews and meta-analyses is to answer the research question, 'For which types of surgery, at which stages of care, in which sub-groups of patients and delivered under what conditions are different types of perioperative oxygen therapy clinically effective?'.

METHODS

We will search key electronic databases (MEDLINE, EMBASE, the Cochrane Database of Systematic Reviews, CENTRAL, Epistemonikos, PROSPERO, the INAHTA International HTA Database and DARE archives) for systematic reviews and randomised controlled trials comparing perioperative oxygen strategies. Each review will be mapped according to type of surgery, surgical pathway timepoints and clinical comparison. The highest quality reviews with the most comprehensive and up-to-date coverage of relevant literature will be chosen as anchoring reviews. Standardised data will be extracted from each chosen review, including definition of oxygen therapy, summaries of interventions and comparators, patient population, surgical characteristics and assessment of overall certainty of evidence. For clinical outcomes and adverse events, the overall pooled findings and results of subgroup and sensitivity analyses (where available) will be extracted. Trial-level data will be extracted for surgical site infections, mortality, and potential trial-level effect modifiers such as risk of bias, outcome definition and type of surgery to facilitate quantitative data analysis. This analysis will adopt a multiple indication review approach with panoramic meta-analysis using review-level data and meta-regression using trial-level data. An evidence map will be produced to summarise our findings and highlight any research gaps.

DISCUSSION

There is a need to provide a panoramic overview of systematic reviews and meta-analyses describing peri-operative oxygen practice to both inform clinical practice and identify areas of ongoing uncertainty, where further research may be required. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42021272361.

Fraction of Inspired Oxygen During General Anesthesia for Non-Cardiac Surgery: Systematic Review and Meta-Analysis

Background

Controversy exists regarding the effects of a high versus a low intraoperative fraction of inspired oxygen (FiO₂) in adults undergoing general anesthesia. This systematic review and meta‐analysis investigated the effect of a high versus a low FiO₂ on postoperative outcomes.

Methods

PubMed and Embase were searched on March 22, 2022 for randomized clinical trials investigating the effect of different FiO₂ levels in adults undergoing general anesthesia for non‐cardiac surgery. Two investigators independently reviewed studies for relevance, extracted data, and assessed risk of bias. Meta‐analyses were performed for relevant outcomes, and potential effect measure modification was assessed in subgroup analyses and meta‐regression. The evidence certainty was evaluated using GRADE.

Results

This review included 25 original trials investigating the effect of a high (mostly 80%) versus a low (mostly 30%) FiO₂. Risk of bias was intermediate for all trials. A high FiO₂ did not result in a significant reduction in surgical site infections (OR: 0.91, 95% CI 0.81–1.02 [p = .10]). No effect was found for all other included outcomes, including mortality (OR = 1.27, 95% CI: 0.90–1.79 [p = .18]) and hospital length of stay (mean difference = 0.03 days, 95% CI −0.25 to 0.30 [p = .84). Results from subgroup analyses and meta‐regression did not identify any clear effect modifiers across outcomes. The certainty of evidence (GRADE) was rated as low for most outcomes.

Conclusions

In adults undergoing general anesthesia for non‐cardiac surgery, a high FiO₂ did not improve outcomes including surgical site infections, length of stay, or mortality. However, the certainty of the evidence was assessed as low.

Intraoperative High Fraction of Inspiratory Oxygen is Independently Associated with Worse Outcome After Living-Donor Liver Transplantation: A Retrospective Study

Background

Ischemia and reperfusion injury is an important factor that determines graft function after liver transplantation, and oxygen plays a crucial role in this process. However, the relationship between the intraoperative high fraction of inspiratory oxygen (FiO₂) and living-donor-liver-transplantation (LDLT) outcome remains unclear.

Patients and Methods

A total of 199 primary adult-to-adult LDLT cases in Kyoto University Hospital between January 2010 and December 2017 were enrolled in this study. The intraoperative FiO₂ was averaged using the total amount of intraoperative oxygen and air and defined as the calculated FiO₂ (cFiO₂). The cutoff value of cFiO₂ was set at 0.5.

Results

Between the cFiO₂ <0.5 (n = 156) and ≥0.5 group (n = 43), preoperative recipients’ background, donor factors, and intraoperative parameters were almost comparable. Postoperatively, the cFiO₂ ≥0.5 group showed a higher early allograft dysfunction (EAD) rate (P = 0.049) and worse overall graft survival (P = 0.036) than the cFiO₂ <0.5 group. Although the cFiO₂ ≥0.5 was not an independent risk factor for EAD in multivariable analysis (OR 2.038, 95%CI 0.992–4.186, P = 0.053), it was an independent risk factor for overall graft survival after LDLT (HR 1.897, 95%CI 1.007–3.432, P = 0.048).

Conclusion

The results of this study suggest that intraoperative high FiO₂ may be associated with worse graft survival after LDLT. Avoiding higher intraoperative FiO₂ may be beneficial for LDLT recipients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00268-022-06544-7.

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.

Oxidative Stress and Endothelial Dysfunction in Sepsis and Acute Inflammation

Significance: Under homeostatic conditions, the endothelium dynamically regulates vascular barrier function, coagulation pathways, leukocyte adhesion, and vasomotor tone. During sepsis and acute inflammation, endothelial cells (ECs) undergo multiple phenotypic and functional modifications that are initially adaptive but eventually become harmful, leading to microvascular dysfunction and multiorgan failure. Critical Issues and Recent Advances: Sepsis unbalances the redox homeostasis toward a pro-oxidant state, characterized by an excess production of reactive oxygen species and reactive nitrogen species, mitochondrial dysfunction, and a breakdown of antioxidant systems. In return, oxidative stress (OS) alters multiple EC functions and promotes a proinflammatory, procoagulant, and proadhesive phenotype. The OS also induces glycocalyx deterioration, cell death, increased permeability, and impaired vasoreactivity. Thus, during sepsis, the ECs are both a significant source and one of the main targets of OS. Future Directions: This review aims at covering the current understanding of the role of OS in the endothelial adaptive or maladaptive multifaceted response to sepsis and to outline the therapeutic potential and issues of targeting OS and endothelial dysfunction during sepsis and septic shock. One of the many challenges in the management of sepsis is now based on the detection and correction of these anomalies of endothelial function.

Efficacy of a glucagon-like peptide-1 agonist and restrictive versus liberal oxygen supply in patients undergoing coronary artery bypass grafting or aortic valve replacement: study protocol for a 2-by-2 factorial designed, randomised clinical trial

INTRODUCTION

Coronary artery bypass grafting (CABG) and/or aortic valve replacement (AVR) are associated with risk of death, as well as brain, heart and kidney injury. Glucagon-like peptide-1 (GLP-1) analogues are approved for treatment of type 2 diabetes, and GLP-1 analogues have been suggested to have potential organ-protective and anti-inflammatory effects. During cardiopulmonary bypass (CPB), consensus on the optimal fraction of oxygen is lacking. The objective of this study is to determine the efficacy of the GLP-1-analogue exenatide versus placebo and restrictive oxygenation (50% fractional inspired oxygen, FiO2) versus liberal oxygenation (100% FiO2) in patients undergoing open heart surgery.

METHODS AND ANALYSIS

A randomised, placebo-controlled, double blind (for the exenatide intervention)/single blind (for the oxygenation strategy), 2×2 factorial designed single-centre trial on adult patients undergoing elective or subacute CABG and/or surgical AVR. Patients will be randomised in a 1:1 and 1:1 ratio to a 6-hour and 15 min infusion of 17.4 µg of exenatide or placebo during CPB and to a FiO2 of 50% or 100% during and after weaning from CPB. Patients will be followed until 12 months after inclusion of the last participant. The primary composite endpoint consists of time to first event of death, renal failure requiring renal replacement therapy, hospitalisation for stroke or heart failure. In addition, the trial will include predefined sub-studies applying more advanced measures of cardiac- and pulmonary dysfunction, renal dysfunction and cerebral dysfunction. The trial is event driven and aims at 323 primary endpoints with a projected inclusion of 1400 patients.

ETHICS AND DISSEMINATION

Eligible patients will provide informed, written consent prior to randomisation. The trial is approved by the local ethics committee and is conducted in accordance with Danish legislation and the Declaration of Helsinki. The results will be presented in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT02673931.

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.

Progress in research of postoperative nausea and vomiting after painless gastrointestinal endoscopy

Postoperative nausea and vomiting (PONV) refers to nausea and vomiting occurring within 24 h after surgery. PONV seriously affects the quality of postoperative recovery after painless gastrointestinal endoscopy. In this paper, we review the progress in the research of PONV after painless gastrointestinal endoscopy to provide clinical guidance for improving the medical safety and service quality of painless and comfortable anesthesia. PONV after painless gastrointestinal endoscopy has unique factors and characteristics. On the basis of comprehensive evaluation and according to the patient's specific situation, the doctors should identify the risk factors, optimize the anesthesia scheme, choose anesthetics and analgesics rationally, and take comprehensive diagnostic and therapeutic measures.

Effect of intra-operative high inspired fraction of oxygen on postoperative nausea and vomiting in children undergoing surgery: A prospective randomised double-blind study

BACKGROUND

Administration of high inspired fraction of oxygen (FiO2) during anaesthesia has been proposed to decrease postoperative nausea and vomiting (PONV) in adults but has not been extensively studied in children.

OBJECTIVES

The primary objective of this study was to evaluate the effect of 80% FiO2 on the incidence of PONV in children undergoing surgery.

DESIGN

Prospective, randomised, study.

SETTING

Single-centre, teaching hospital.

PATIENTS

Children of either gender in the age group of 5 to 15 years scheduled for elective surgeries were assessed for eligibility. In cases of emergency surgeries; patients receiving supplemental oxygen pre-operatively or on mechanical ventilation; sepsis; bowel obstruction or ischaemia; poor nutritional status; anaemia (Hb <8 g%) or surgeries lasting less than 1 h or greater than 4 h were excluded from the study.

INTERVENTIONS

After induction of anaesthesia, children were randomised to receive either 30 or 80% oxygen in air, till the end of surgery.

MAIN OUTCOME MEASURES

Incidence of PONV within 24 h; surgical site infections (SSI)s; serum serotonin and TNF-α levels and the incidence of postoperative pulmonary complications (PPC)s were studied.

RESULTS

The overall 24 h incidence of PONV was not different between the low and high FiO2 groups [24 vs. 23%; P = 0.84; odds ratio (OR) 0.92; 95% confidence interval (CI), 0.44 to 2.06]. The incidence of SSIs (15 vs. 12%; P = 0.61; OR 0.77; 95% CI, 0.28 to 2.10) and PPCs (12 vs. 8%; P = 0.38; OR 0.59; 95% CI, 0.18 to 1.92) were not significant between the low and high FiO2 groups, respectively. Intragroup and intergroup comparisons of serum serotonin and TNF-α showed no significant difference either at baseline or at the end of surgery.

CONCLUSION

High intra-operative FiO2 of 80% does not provide additional protection against PONV in children.

TRIAL REGISTRATION

The study was registered with Clinical Trials Registry of India (CTRI) with trial registration no: CTRI/2018/07/014974.

Target arterial PO2 according to the underlying pathology: a mini-review of the available data in mechanically ventilated patients

There is an ongoing discussion whether hyperoxia, i.e. ventilation with high inspiratory O2 concentrations (FIO2), and the consecutive hyperoxaemia, i.e. supraphysiological arterial O2 tensions (PaO2), have a place during the acute management of circulatory shock. This concept is based on experimental evidence that hyperoxaemia may contribute to the compensation of the imbalance between O2 supply and requirements. However, despite still being common practice, its use is limited due to possible oxygen toxicity resulting from the increased formation of reactive oxygen species (ROS) limits, especially under conditions of ischaemia/reperfusion. Several studies have reported that there is a U-shaped relation between PaO2 and mortality/morbidity in ICU patients. Interestingly, these mostly retrospective studies found that the lowest mortality coincided with PaO2 ~ 150 mmHg during the first 24 h of ICU stay, i.e. supraphysiological PaO2 levels. Most of the recent large-scale retrospective analyses studied general ICU populations, but there are major differences according to the underlying pathology studied as well as whether medical or surgical patients are concerned. Therefore, as far as possible from the data reported, we focus on the need of mechanical ventilation as well as the distinction between the absence or presence of circulatory shock. There seems to be no ideal target PaO2 except for avoiding prolonged exposure (> 24 h) to either hypoxaemia (PaO2 < 55-60 mmHg) or supraphysiological (PaO2 > 100 mmHg). Moreover, the need for mechanical ventilation, absence or presence of circulatory shock and/or the aetiology of tissue dysoxia, i.e. whether it is mainly due to impaired macro- and/or microcirculatory O2 transport and/or disturbed cellular O2 utilization, may determine whether any degree of hyperoxaemia causes deleterious side effects.

Magnitude and associated factors of intraoperative nausea and vomiting among parturients who gave birth with cesarean section under spinal anesthesia at South Gondar zone Hospitals, Ethiopia

BACKGROUND

Intraoperative nausea and vomiting are common intraoperative events by which parturient feel discomfort and disturbed after spinal anesthesia.

METHODS

Hospital-based cross-sectional study was conducted on mothers who underwent cesarean section with spinal anesthesia. Descriptive analysis and chi-square test were employed. Bivariable and multivariable logistic regressions were used to measure the association of factors with the outcome variable intraoperative nausea and vomiting. A p-value of ≤0.05 was used to decide statistical significance for multivariable logistic regression.

RESULT

A total of 246 parturients were participated in this study. The incidence of intraoperative nausea and vomiting was 40.2%. According to multivariable logistic regression, age greater than 30 years (AOR, 6.26; 95%CI, 2.2-17.78; p-value 0.001), primiparous (AOR, 3.72; 95%CI, 1.35-10.24; p-value, 0.011), having motion sickness (AOR, 7.1; 95%CI, 2.75-18.33; p-value 0.001), emergency cesarean sectin (AOR, 9.85; 95%CI, 3.19-30.38; p-value 0.001), oxygen suplimentation (AOR, 0.021; 95%CI, 0.005-0.08; p-value 0.0001) and uterotonic agent (AOR, 2.99; 95%CI 1.24-7.22; p-value 0.015) had statistically significant association with intraoperative nausea and vomiting.

CONCLUSION

In our study, the overall incidence of intraoperative nausea and vomiting after spinal anesthesia was 40.2%. Parturients with age greater than 30 years, having motion sickness, didn't get intraoperative supplemental oxygen, oxytocin used for the uterotonic purpose, emergency surgery, and primiparous were at increased risk of intraoperative nausea and vomiting.

Etomidate attenuates hyperoxia-induced acute lung injury in mice by modulating the Nrf2/HO-1 signaling pathway

The present study aimed to investigate the protective effects of etomidate on hyperoxia-induced acute lung injury in mice, particularly on the nuclear factor-erythroid 2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1) pathway. Fifty specific pathogen-free mice were randomly divided into the blank control, model, high oxygen exposure + low etomidate dose (0.3 mg·kg^-1), a high oxygen exposure + moderate etomidate dose (3 mg·kg^-1), and a high oxygen exposure + high etomidate dose (10 mg·kg^-1) groups, with ten mice allotted per group. After 72 h, the mice were sacrificed and the lung tissues were harvested, and the wet-to-dry (W/D) ratio of the tissues was calculated. Hematoxylin-eosin staining was performed to observe the pathological changes in the lung tissues, and the lung injury score (LIS) was calculated. The mRNA and protein expression levels of Nrf2 and HO-1 were measured. The malondialdehyde (MDA), myeloperoxidase (MPO), superoxide dismutase (SOD) and catalase (CAT) levels were also measured, and interleukin (IL)-1β, IL-6, tumor necrosis factor alpha (TNF-α) and IL-10 concentrations in the bronchoalveolar lavage fluid were determined. At low and moderate doses, etomidate decreased pathological damage in the lung tissue, decreased the LIS and W/D ratio, upregulated Nrf2 and HO-1 mRNA and protein expression, decreased IL-1β, IL-6, and TNF-α concentrations, increased MPO activity and IL-10 levels, suppressed the production of the oxidation product MDA, and enhanced the activities of the antioxidant enzymes CAT and SOD. Within a certain dose range, etomidate enhanced antioxidant and anti-inflammatory effects in mice, thereby decreasing lung injury induced by the chronic inhalation of oxygen at high concentrations. Furthermore, the underlying mechanism may be associate with the upregulation of the Nrf2/HO-1 signaling pathway.

Frequency of hyperoxaemia during and after major surgery

The oxygen concentration (FiO₂) and arterial oxygen tension (PaO₂) delivered in patients undergoing major surgery is poorly understood. We aimed to assess current practice with regard to the delivered FiO₂ and the resulting PaO₂ in patients undergoing major surgery. We performed a retrospective cohort study in a tertiary hospital. Data were collected prospectively as part of a larger randomised controlled trial but were analysed retrospectively. Patients were included if receiving controlled mandatory ventilation and arterial line monitoring. Anaesthetists determined the FiO₂ and the oxygenation saturation (SpO₂) targets. An arterial blood gas (ABG) was obtained 15-20 minutes after induction of anaesthesia, immediately before the emergence phase of anaesthesia and 15 minutes after arrival in the post-anaesthesia care unit (PACU). We defined hyperoxaemia as a PaO₂ of >150 mmHg and included a further threshold of PaO₂ >200 mmHg. We studied 373 patients. The median (interquartile range (IQR)) lowest intraoperative FiO₂ and SpO₂ values were 0.45 (IQR 0.4-0.5) and 97% (IQR 96-98%), respectively, with a median PaO₂ on the first and second ABG of 237 mmHg (IQR 171-291 mmHg) and 189 mmHg (IQR 145-239 mmHg), respectively. In the PACU, the median lowest oxygen flow rate was 6 L/min (IQR 3-6 L/min), and the PaO₂ was 158 mmHg (IQR 120-192 mmHg). Hyperoxaemia occurred in 82%, 73% and 54% of participants on the first and second intraoperative and postoperative ABGs respectively. A PaO₂ of >200 mmHg occurred in 64%, 41% and 21% of these blood gases, respectively. In an Australian tertiary hospital, a liberal approach to FiO₂ and PaO₂ was most common and resulted in a high incidence of perioperative hyperoxaemia.

Association of Intraoperative Ventilator Management With Postoperative Oxygenation, Pulmonary Complications, and Mortality

BACKGROUND

"Lung-protective ventilation" describes a ventilation strategy involving low tidal volumes (VTs) and/or low driving pressure/plateau pressure and has been associated with improved outcomes after mechanical ventilation. We evaluated the association between intraoperative ventilation parameters (including positive end-expiratory pressure [PEEP], driving pressure, and VT) and 3 postoperative outcomes: (1) PaO2/fractional inspired oxygen tension (FIO2), (2) postoperative pulmonary complications, and (3) 30-day mortality.

METHODS

We retrospectively analyzed adult patients who underwent major noncardiac surgery and remained intubated postoperatively from 2006 to 2015 at a single US center. Using multivariable regressions, we studied associations between intraoperative ventilator settings and lowest postoperative PaO2/FIO2 while intubated, pulmonary complications identified from discharge diagnoses, and in-hospital 30-day mortality.

RESULTS

Among a cohort of 2096 cases, the median PEEP was 5 cm H2O (interquartile range = 4-6), median delivered VT was 520 mL (interquartile range = 460-580), and median driving pressure was 15 cm H2O (13-19). After multivariable adjustment, intraoperative median PEEP (linear regression estimate [B] = -6.04; 95% CI, -8.22 to -3.87; P < .001), median FIO2 (B = -0.30; 95% CI, -0.50 to -0.10; P = .003), and hours with driving pressure >16 cm H2O (B = -5.40; 95% CI, -7.2 to -4.2; P < .001) were associated with decreased postoperative PaO2/FIO2. Higher postoperative PaO2/FIO2 ratios were associated with a decreased risk of pulmonary complications (adjusted odds ratio for each 100 mm Hg = 0.495; 95% CI, 0.331-0.740; P = .001, model C-statistic of 0.852) and mortality (adjusted odds ratio = 0.495; 95% CI, 0.366-0.606; P < .001, model C-statistic of 0.820). Intraoperative time with VT >500 mL was also associated with an increased likelihood of developing a postoperative pulmonary complication (adjusted odds ratio = 1.06/hour; 95% CI, 1.00-1.20; P = .042).

CONCLUSIONS

In patients requiring postoperative intubation after noncardiac surgery, increased median FIO2, increased median PEEP, and increased time duration with elevated driving pressure predict lower postoperative PaO2/FIO2. Intraoperative duration of VT >500 mL was independently associated with increased postoperative pulmonary complications. Lower postoperative PaO2/FIO2 ratios were independently associated with pulmonary complications and mortality. Our findings suggest that postoperative PaO2/FIO2 may be a potential target for future prospective trials investigating the impact of specific ventilation strategies for reducing ventilator-induced pulmonary injury.

Perioperative Hyperoxyphobia: Justified or Not? Benefits and Harms of Hyperoxia during Surgery

The use of an inspiratory oxygen fraction of 0.80 during surgery is a topic of ongoing debate. Opponents claim that increased oxidative stress, atelectasis, and impaired oxygen delivery due to hyperoxic vasoconstriction are detrimental. Proponents point to the beneficial effects on the incidence of surgical site infections and postoperative nausea and vomiting. Also, hyperoxygenation is thought to extend the safety margin in case of acute intraoperative emergencies. This review provides a comprehensive risk-benefit analysis for the use of perioperative hyperoxia in noncritically ill adults based on clinical evidence and supported by physiological deduction where needed. Data from the field of hyperbaric medicine, as a model of extreme hyperoxygenation, are extrapolated to the perioperative setting. We ultimately conclude that current evidence is in favour of hyperoxia in noncritically ill intubated adult surgical patients.

Benefits and harms of increased inspiratory oxygen concentrations

PURPOSE OF REVIEW

The topic of perioperative hyperoxia remains controversial, with valid arguments on both the 'pro' and 'con' side. On the 'pro' side, the prevention of surgical site infections was a strong argument, leading to the recommendation of the use of hyperoxia in the guidelines of the Center for Disease Control and the WHO. On the 'con' side, the pathophysiology of hyperoxia has increasingly been acknowledged, in particular the pulmonary side effects and aggravation of ischaemia/reperfusion injuries.

RECENT FINDINGS

Some 'pro' articles leading to the Center for Disease Control and WHO guidelines advocating perioperative hyperoxia have been retracted, and the recommendations were downgraded from 'strong' to 'conditional'. At the same time, evidence that supports a tailored, more restrictive use of oxygen, for example, in patients with myocardial infarction or following cardiac arrest, is accumulating.

SUMMARY

The change in recommendation exemplifies that despite much work performed on the field of hyperoxia recently, evidence on either side of the argument remains weak. Outcome-based research is needed for reaching a definite recommendation.

Effects of oxygen on post-surgical infections during an individualised perioperative open-lung ventilatory strategy: a randomised controlled trial

BACKGROUND

We aimed to examine whether using a high fraction of inspired oxygen (FIO₂) in the context of an individualised intra- and postoperative open-lung ventilation approach could decrease surgical site infection (SSI) in patients scheduled for abdominal surgery.

METHODS

We performed a multicentre, randomised controlled clinical trial in a network of 21 university hospitals from June 6, 2017 to July 19, 2018. Patients undergoing abdominal surgery were randomly assigned to receive a high (0.80) or conventional (0.3) FIO₂ during the intraoperative period and during the first 3 postoperative hours. All patients were mechanically ventilated with an open-lung strategy, which included recruitment manoeuvres and individualised positive end-expiratory pressure for the best respiratory-system compliance, and individualised continuous postoperative airway pressure for adequate peripheral oxyhaemoglobin saturation. The primary outcome was the prevalence of SSI within the first 7 postoperative days. The secondary outcomes were composites of systemic complications, length of intensive care and hospital stay, and 6-month mortality.

RESULTS

We enrolled 740 subjects: 371 in the high FIO₂ group and 369 in the low FIO₂ group. Data from 717 subjects were available for final analysis. The rate of SSI during the first postoperative week did not differ between high (8.9%) and low (9.4%) FIO₂ groups (relative risk [RR]: 0.94; 95% confidence interval [CI]: 0.59-1.50; P=0.90]). Secondary outcomes, such as atelectasis (7.7% vs 9.8%; RR: 0.77; 95% CI: 0.48-1.25; P=0.38) and myocardial ischaemia (0.6% [n=2] vs 0% [n=0]; P=0.47) did not differ between groups.

CONCLUSIONS

An oxygenation strategy using high FIO₂ compared with conventional FIO₂ did not reduce postoperative SSIs in abdominal surgery. No differences in secondary outcomes or adverse events were found.

CLINICAL TRIAL REGISTRATION

NCT02776046.

PROtective Ventilation with a low versus high Inspiratory Oxygen fraction (PROVIO) and its effects on postoperative pulmonary complications: protocol for a randomized controlled trial

BACKGROUND

Postoperative pulmonary complications (PPCs) are the most common perioperative complications following surgical site infection (SSI). They prolong the hospital stay and increase health care costs. A lung-protective ventilation strategy is considered better practice in abdominal surgery to prevent PPCs. However, the role of the inspiratory oxygen fraction (FiO₂) in the strategy remains disputed. Previous trials have focused on reducing SSI by increasing the inhaled oxygen concentration but higher FiO₂ (80%) was found to be associated with a greater incidence of atelectasis and mortality in recent research. The trial aims at evaluating the effect of different FiO₂ added to the lung-protective ventilation strategy on the incidence of PPCs during general anesthesia for abdominal surgery.

METHODS AND DESIGN

PROtective Ventilation with a low versus high Inspiratory Oxygen fraction trial (PROVIO) is a single-center, prospective, randomized controlled trial planning to recruit 252 patients undergoing abdominal surgery lasting for at least 2 h. The patients will be randomly assigned to (1) a low-FiO₂ (30% FiO₂) group and (2) a high-FiO₂ (80% FiO₂) group in the lung-protective ventilation strategy. The primary outcome of the study is the occurrence of PPCs within the postoperative 7 days. Secondary outcomes include the severity grade of PPCs, the occurrence of postoperative extrapulmonary complications and all-cause mortality within the postoperative 7 and 30 days.

DISCUSSION

The PROVIO trial assesses the effect of low versus high FiO₂ added to a lung-protective ventilation strategy on PPCs for abdominal surgery patients and the results should provide practical approaches to intraoperative oxygen management.

TRIAL REGISTRATION

www.ChiCTR.org.cn , identifier: ChiCTR18 00014901 . Registered on 13 February 2018.

Positive End-Expiratory Pressure During Anesthesia for Prevention of Postoperative Pulmonary Complications: A Meta-analysis With Trial Sequential Analysis of Randomized Controlled Trials

BACKGROUND

Whether intraoperative positive end-expiratory pressure (PEEP) can reduce the risk of postoperative pulmonary complications remains controversial. We performed a systematic review of currently available literature to investigate whether intraoperative PEEP decreases pulmonary complications in anesthetized patients undergoing surgery.

METHODS

We searched PubMed, Embase, and the Cochrane Library to identify randomized controlled trials (RCTs) that compared intraoperative PEEP versus zero PEEP (ZEEP) for postoperative pulmonary complications in adults. The prespecified primary outcome was postoperative pulmonary atelectasis.

RESULTS

Fourteen RCTs enrolling 1238 patients met the inclusion criteria. Meta-analysis using a random-effects model showed a decrease in postoperative atelectasis (relative risk [RR], 0.51; 95% confidence interval [CI], 0.35-0.76; trial sequential analyses [TSA]-adjusted CI, 0.10-2.55) and postoperative pneumonia (RR, 0.48; 95% CI, 0.27-0.84; TSA-adjusted CI, 0.05-4.86) in patients receiving PEEP ventilation. However, TSA showed that the cumulative Z-curve of 2 outcomes crossed the conventional boundary but did not cross the trial sequential monitoring boundary, indicating a possible false-positive result. We observed no effect of PEEP versus ZEEP ventilation on postoperative mortality (RR, 1.78; 95% CI, 0.55-5.70).

CONCLUSIONS

The evidence that intraoperative PEEP reduces postoperative pulmonary complications is suggestive but too unreliable to allow definitive conclusions to be drawn.

Predicting surgical site infections using a novel nomogram in patients with hepatocelluar carcinoma undergoing hepatectomy

BACKGROUND

Surgical site infections (SSI) remain a major cause of morbidity after hepatectomy for hepatocellular carcinoma (HCC).

AIM

To identify the risk factors associated with SSI, and develop a nomogram to predict SSI among patients undergoing hepatectomy.

METHODS

We retrospectively reviewed the data of patients diagnosed with HCC undergoing hepatectomy at two academic institutions in China, and evaluated the occurrence of SSI. Independent risk factors for SSI were identified using univariate and multivariate analyses. Based on these independent risk factors, a nomogram was established using the data of patients in the first institution, and was validated using data from an external independent cohort from the second institution.

RESULTS

The nomogram was established using data from 309 patients, whereas the validation cohort used data from 331 patients. The operation duration, serum albumin level, repeat hepatectomy, and ASA score were identified as independent risk factors. The concordance index (C-index) of the nomogram for SSI prediction in the training cohort was 0.86; this nomogram also performed well in the external validation cohort, with a C-index of 0.84. Accordingly, we stratified patients into three groups, with a distinct risk range based on the nomogram prediction, to guide clinical practice.

CONCLUSION

Our novel nomogram offers good preoperative prediction for SSIs in patients undergoing hepatectomy.

Dose variability of supplemental oxygen therapy with open patient interfaces based on in vitro measurements using a physiologically realistic upper airway model

BACKGROUND

Supplemental oxygen therapy is widely used in hospitals and in the home for chronic care. However, there are several fundamental problems with the application of this therapy such that patients are often exposed to arterial oxygen concentrations outside of the intended target range. This paper reports volume-averaged tracheal oxygen concentration measurements (FtO2) from in vitro experiments conducted using a physiologically realistic upper airway model. The goal is to provide data to inform a detailed discussion of the delivered oxygen dose.

METHODS

A baseline FtO2 dataset using a standard, straight adult nasal cannula was established by varying tidal volume (Vt), breathing frequency (f), and continuous oxygen flow rate (QO2) between the following levels to create a factorial design: Vt = 500, 640, or 800 ml; f = 12, 17, or 22 min- 1; QO2 = 2, 4, or 6 l/min. Further experiments were performed to investigate the influence on FtO2 of variation in inspiratory/expiratory ratio, inclusion of an inspiratory or expiratory pause, patient interface selection (e.g. nasal cannula versus a facemask), and rapid breathing patterns in comparison with the baseline measurements.

RESULTS

Oxygen concentration measured at the trachea varied by as much as 60% (i.e. from 30.2 to 48.0% of absolute oxygen concentration) for the same oxygen supply flow rate due to variation in simulated breathing pattern. Among the baseline cases, the chief reasons for variation were 1) the influence of variation in tidal volume leading to variable FiO2 and 2) variation in breathing frequency affecting volume of supplemental oxygen delivered through the breath.

CONCLUSION

For oxygen administration using open patient interfaces there was variability in the concentration and quantity of oxygen delivered to the trachea over the large range of scenarios studied. Of primary importance in evaluating the oxygen dose is knowledge of the breathing parameters that determine the average inhalation flow rate relative to the oxygen flow rate. Otherwise, the oxygen dose cannot be determined.

Effectiveness and pulmonary complications of perioperative laryngeal mask airway used in elderly patients (POLMA-EP trial): study protocol for a randomized controlled trial

Background

With the increasing amount of geriatric surgery, it has become a great challenge for anesthesiologists to reduce the incidence of postoperative pulmonary complications (PPCs). The two most popular airway management methods, laryngeal mask airway (LMA) and endotracheal intubation (ETI), both have their unique advantages in specific clinical settings. For the purpose of helping clinicians make better decisions on airway management during geriatric surgery, we designed this multi-center clinical trial to compare the influence of LMA and ETI on PPCs.

Methods/design

In this multi-center, randomized, parallel clinical trial, a total of 6000 elderly patients, aged ≥ 70 years, with an American Society of Anesthesiologists classification level of 1–2 and a body mass index ≤ 35 kg/m², undergoing elective surgery will be enrolled and randomized into the LMA or the ETI group. Both groups will receive usual perioperative care except for the adoption of LMA/ETI. Primary outcomes are the occurrence of PPCs and patients’ perioperative mortality rates. Ease of intubation, anesthetics consumption, treatment for PPCs, duration of surgery, anesthesia recovery time and performance, time of PPC onset, postanesthesia care unit stay, intensive care unit admission and stay, in-hospital days, re-admission rates, hospitalization cost, and patients’ satisfactory scores will be secondary outcomes. Follow-up will be conducted through phone-call visits until 12 weeks after discharge.

Discussion

This trial will assess the possible benefits or disadvantages of perioperative LMA use in elderly patients compared with ETI regarding the occurrence of PPCs and clinical prognosis. We expect that this trial will also add to the current understanding of PPCs in geriatric populations and contribute to the international recommendations of geriatric surgery management.

Trial registration

ClinicalTrials.gov, NCT02240901. Registered on 16 September 2014.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3351-2) contains supplementary material, which is available to authorized users.

The Effects of Intraoperative Inspired Oxygen Fraction on Postoperative Pulmonary Parameters in Patients with General Anesthesia: A Systemic Review and Meta-Analysis

High intraoperative inspired oxygen concentration is applied to prevent desaturation during induction and recovery of anesthesia. However, high oxygen concentration may lead to postoperative pulmonary complications. The purpose of this study is to compare the postoperative pulmonary parameters according to intraoperative inspired oxygen fraction in patients undergoing general anesthesia. We identified all randomized controlled trials investigating postoperative differences in arterial gas exchange according to intraoperative fraction of inspired oxygen (FiO₂). A total of 10 randomized controlled trials were included, and 787 patients were analyzed. Postoperative PaO₂ was lower in the high FiO₂ group compared with the low FiO₂ group (mean difference (MD) −4.97 mmHg, 95% CI −8.21 to −1.72, p = 0.003). Postoperative alveolar-arterial oxygen gradient (AaDO₂) was higher (MD 3.42 mmHg, 95% CI 0.95 to 5.89, p = 0.007) and the extent of atelectasis was more severe (MD 2.04%, 95% CI 0.14 to 3.94, p = 0.04) in high intraoperative FiO₂ group compared with low FiO₂ group. However, postoperative SpO₂ was comparable between the two groups. The results of this meta-analysis suggest that high inspired oxygen fraction during anesthesia may impair postoperative pulmonary parameters. Cautious approach in intraoperative inspired oxygen fraction is required for patients susceptible to postoperative pulmonary complications.

Guidelines for Perioperative Care in Elective Colorectal Surgery: Enhanced Recovery After Surgery (ERAS®) Society Recommendations: 2018

BACKGROUND

This is the fourth updated Enhanced Recovery After Surgery (ERAS®) Society guideline presenting a consensus for optimal perioperative care in colorectal surgery and providing graded recommendations for each ERAS item within the ERAS® protocol.

METHODS

A wide database search on English literature publications was performed. Studies on each item within the protocol were selected with particular attention paid to meta-analyses, randomised controlled trials and large prospective cohorts and examined, reviewed and graded according to Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system.

RESULTS

All recommendations on ERAS® protocol items are based on best available evidence; good-quality trials; meta-analyses of good-quality trials; or large cohort studies. The level of evidence for the use of each item is presented accordingly.

CONCLUSIONS

The evidence base and recommendation for items within the multimodal perioperative care pathway are presented by the ERAS® Society in this comprehensive consensus review.

Respiratory complications of anaesthesia

Postoperative pulmonary complications are a major determinant of outcome for patients and consume huge resources within hospital, particularly in critical care. Prediction and anticipation of postoperative pulmonary complications are vital for patient selection and, in some cases, for informed patient consent. Being able to assess the likelihood of postoperative pulmonary complications also allows research into methods to reduce them by allowing allocation of patients to the appropriate arms of research trials. Some patients have pre-operative characteristics or belong to patient groups such as those with chronic obstructive pulmonary disease or obstructive sleep apnoea, where techniques and evidence-based guidance to avoid or reduce complications are becoming established. Intra-operative ventilation and the use of lung-protective ventilation may be helpful during major surgery, but studies looking at reduced tidal volumes, recruitment and levels of positive end-expiratory pressure, have this far only led to a degree of consensus in terms of tidal volume, although parameters that predispose to postoperative pulmonary complications are becoming clearer. Optimal postoperative care in terms of analgesia, positioning, physiotherapy and mobilisation is another developing area. Techniques such as continuous positive airways pressure, non-invasive ventilation and high-flow nasal humidified oxygen appear to show some benefit, but the exact roles, pressures and timings of each are currently being explored. Much remains to be researched and developed into evidence-based practice.