Intraoperative Oxygen Concentration and Postoperative Delirium After Laparoscopic Gastric and Colorectal Malignancies Surgery: A Randomized, Double-Blind, Controlled Trial

Characteristics associated with effectiveness in postoperative delirium research: a systematic review of randomised controlled trials with meta-regression and meta-analysis

BACKGROUND

Postoperative delirium remains prevalent despite extensive research through randomised trials aimed at reducing its incidence. Understanding trial characteristics associated with interventions' effectiveness facilitates data interpretation.

METHODS

Trial characteristics were extracted from eligible trials identified through two systematic literature searches. Multivariable meta-regression was used to investigate trial characteristics associated with effectiveness estimated using odds ratios. Meta-analysis was used to investigate pooled effectiveness.

RESULTS

We identified 201 eligible trials. Compared with China, trials from the USA/Canada (ratio of odds ratio, 1.89; 95% confidence interval, 1.45-2.45) and Europe/Australia/New Zealand (1.67; 1.29-2.18) had an 89% and 67% higher odds ratio, respectively, suggesting reduced effectiveness. The effectiveness was enhanced when the incidence of postoperative delirium increased (0.85; 0.79-0.92, per 10% increase). Trials with concerns related to deviations from intended interventions reported increased effectiveness compared with those at low risk (0.69; 0.53-0.90). Compared with usual care, certain interventions appeared to have reduced the incidence of postoperative delirium in low-risk trials with low-to-moderate certainty of evidence. However, these findings should be considered inconclusive because of challenges in grouping heterogeneous interventions, the limited number of eligible trials, the prevalence of small-scale studies, and potential publication bias.

CONCLUSIONS

The effectiveness of postoperative delirium trials varied based on the region of trial origin, the incidence of delirium, and the risk of bias. The limitations caution against drawing definitive conclusions from different bodies of evidence. These findings highlight the imperative need to improve the quality of research on a global scale.

SYSTEMATIC REVIEW PROTOCOL

PROSPERO (CRD42023413984).

Preoperative cognitive function as a risk factor of postoperative delirium in cancer surgeries: A systematic review and meta-analysis

Postoperative delirium (POD) after cancer surgeries can be a result of chemo brain, anesthesia, surgery duration, and preoperative cognitive impairment. Although older age and preoperative cognitive dysfunction were reported to increase the risk of POD in noncardiac surgery, the role of preoperative cognitive function and age in the development of POD after all types of cancer surgeries is not clear. This study aimed to determine the relationship between preoperative cognitive function and likelihood of POD after cancer surgeries. This study used three main online databases and followed PRISMA guidelines. English language original articles that examined preoperative cognitive function before solid tumor cancer surgery and assessed patients for postoperative delirium were included. We employed the random effect meta-analysis method. The overall incidence of POD ranged from 8.7% to 50.9%. The confusion assessment method was the most common tool used to assess delirium. Mini-mental state evaluation (MMSE), Mini-cog, and Montreal cognitive assessment were the most common tools to assess cognitive function. The pooled (total observation = 4676) random effects SMD was estimated at -0.84 (95% confidence interval [CI]: -1.30 to -0.31), indicating that lower MMSE scores before surgery are associated with a higher risk of POD. The pooled (total observation = 2668) random effects OR was estimated at 5.17 (95% CI: 2.51 to -10.63), indicating preoperative cognitive dysfunction can significantly predict the occurrence of POD after cancer surgeries. In conclusion, preoperative cognitive function is an independent and significant predictor of POD after solid tumor cancer surgeries.

The effect of high perioperative inspiratory oxygen fraction for abdominal surgery on surgical site infection: a systematic review and meta-analysis

Guidelines from the World Health Organization strongly recommend the use of a high fraction of inspired oxygen (FiO2) in adult patients undergoing general anesthesia to reduce surgical site infection (SSI). However, previous meta-analyses reported inconsistent results. We aimed to address this controversy by focusing specifically on abdominal surgery with relatively high risk of SSI. Medline, EMBASE, and Cochrane CENTRAL databases were searched. Randomized trials of abdominal surgery comparing high to low perioperative FiO2 were included, given that the incidence of SSI was reported as an outcome. Meta-analyses of risk ratios (RR) were performed using a fixed effects model. Subgroup analysis and meta-regression were employed to explore sources of heterogeneity. We included 27 trials involving 15977 patients. The use of high FiO2 significantly reduced the incidence of SSI (n = 27, risk ratio (RR): 0.87; 95% confidence interval (CI): 0.79, 0.95; I2 = 49%, Z = 3.05). Trial sequential analysis (TSA) revealed that z-curve crossed the trial sequential boundary and data are sufficient. This finding held true for the subgroup of emergency operations (n = 2, RR: 0.54; 95% CI: 0.35, 0.84; I2 = 0%, Z = 2.75), procedures using air as carrier gas (n = 9, RR: 0.79; 95% CI: 0.69, 0.91; I2 = 60%, Z = 3.26), and when a high level of FiO2 was maintained for a postoperative 6 h or more (n = 9, RR: 0.68; 95% CI: 0.56, 0.83; I2 = 46%, Z = 3.83). Meta-regression revealed no significant interaction between SSI with any covariates including age, sex, body-mass index, diabetes mellitus, duration of surgery, and smoking. Quality of evidence was assessed to be moderate to very low. Our pooled analysis revealed that the application of high FiO2 reduced the incidence of SSI after abdominal operations. Although TSA demonstrated sufficient data and cumulative analysis crossed the TSA boundary, our results should be interpreted cautiously given the low quality of evidence.Registration: https://www.crd.york.ac.uk/prospero (CRD42022369212) on October 2022.

[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.

Updated meta-analysis on intraoperative inspired fraction of oxygen and the risk of surgical site infection in adults undergoing general and regional anesthesia

This updated meta-analysis aims at exploring whether the use of systematic high vs low intraoperative oxygen fraction (FiO2) may decrease the incidence of postoperative surgical site infection during general (GA) or regional anesthesia (RA). PubMed, Cochrane CENTRAL, ClinicalTrials.gov databases were searched from January 1st, 1999 and July, 1st 2022, for randomized and quasi-randomized controlled trials that included patients in a high and low FiO2 groups and reported the incidence of SSI. The meta-analysis was conducted with a DerSimonian and Laird random-effects model. Thirty studies (24 for GA and 6 for RA) totaling 18,055 patients (15,871 for GA and 2184 for RA) were included. We have low-to-moderate-quality evidence that high FiO2 (mainly 80%) was not associated with a reduction of SSI incidence compared to low FiO2 (mainly 30%) in all patients (RR 0.90, 95%CI 0.79-1.03). Moderate inconsistency existed between studies (I2 = 38%). Subgroup analyses showed a moderate protective effect in patients undergoing GA (RR 0.86, 95%CI 0.75-0.99) (low level of evidence), while high FiO2 was not associated with a reduction of SSI in patients undergoing RA (RR 1.17, 95%CI 0.90-1.52) (moderate level of evidence). Sensitivity analyses restricted to patients ventilated without nitrous oxide (n = 20 studies), to patients operated from abdominal surgeries (n = 21 studies), and to patients suffering from deep SSI (n = 13 studies), all showed the absence of any significant effect of high FiO2. As a conclusion there is no compelling evidence that high FiO2 can improve postoperative patient's outcome on its own when good SSI prevention practices are properly applied. Recent well-designed and adequately powered randomized controlled trials add further weight to these results.

Effects of individualized PEEP on postoperative delirium among older patients in prone position: study protocol for a prospective randomized controlled trial

BACKGROUND

Postoperative delirium (POD) is an acute mental disorder that often occurs in the elderly after surgery. It can delay functional recovery, extend hospital stay, and increase 1-year mortality and financial costs. Studies have shown that inflammation and cerebral desaturation are the potential pathogenesis of postoperative delirium. Prone-position surgery increases peak airway pressure and decreases lung compliance, exacerbating ventilator-induced inflammation response, as well as the decrease of the patient's cerebral oxygen saturation. Recent studies demonstrated that lung-protective ventilation strategy could reduce inflammatory response and improve cerebral oxygen saturation (rSO₂) to prevent POD. In this trial, we aim to investigate the effect of the individualized PEEP on postoperative delirium in elderly patients during prone position.

METHODS

A prospective, randomized clinical trial will be performed in Hebei General Hospital. 106 patients undergoing elective surgery in prone position will be randomly divided into controlled group (group C) and individualized PEEP group (group I). Lung-protective ventilation with tidal volume of 6ml/kg predictive body weight (PBW) and positive end-expiratory pressure (PEEP) of 5 cm H₂O will be applied to patients in group C. Patients in group I will receive the same tidal volume as described in group C plus individualized PEEP corresponding to the maximum dynamic compliance (Cdyn) in the titration method. Our primary endpoint is the prevalence of postoperative delirium based on the Confusion Assessment Method (CAM) until postoperative day 3. Secondary endpoints include the intraoperative rSO₂, respiratory variables, arterial blood gases, lung ultrasound score (LUS), postoperative VAS score, and plasma concentrations of IL-6, IL-1β and neuron-specific enolase (NSE).

DISCUSSION

The results of the current protocol might provide evidence for individualized PEEP to prevent POD among older surgical patients in prone position.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (ChiCTR2200056001). Registered 2022 January 30, http://www.chictr.org.cn/index.aspx .

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.

Association between the reactivity of local cerebral oxygen saturation after hypo-to-hypercapnic tests and delirium after abdominal surgery in older adults: A prospective study

OBJECTIVE

This study aimed to investigate the correlation between changes in regional cerebral oxygen saturation (rSO2) and postoperative delirium in older adults undergoing major abdominal surgery.

MATERIALS AND METHODS

This prospective study enrolled older adults scheduled for elective major abdominal surgery at the Second Affiliated Hospital of Anhui Medical University from August 2021 to January 2022. The change in rSO2 from baseline was determined using the hypo-to-hypercapnic test. The main study outcome was the occurrence of postoperative delirium.

RESULTS

A total of 101 participants were included for analysis, of whom 16 (15.8%) developed postoperative delirium. Compared with non-delirium participants, the mean arterial pressure and heart rate were not significantly different in the postoperative delirium group at T0, T1, T2, T3, T4, and T6 (all P_interaction > 0.05), but the delirium group had lower pH, lower PaO2, and higher lactate levels at T4, T5, and T6 (all P_interaction < 0.05). rSO2 at T0, T1, T2, T3, T4, and T6 was 69.0 (63.2-75.2), 70.7 ± 7.3, 68.2 ± 7.5, 72.1 ± 8.0, 69.9 ± 7.8, 67.4 ± 7.2, and 71.7 ± 8.1, respectively. The postoperative change in rSO2 during the hypercapnia test (TΔrSO2%) was 6.62 (5.31-9.36). Multivariable analysis showed that the Cumulative Illness Rating Scale (odd ratio, OR = 1.89, 95% confidence interval, CI: 1.10-3.25, P = 0.021), preoperative albumin levels (OR = 0.67, 95% CI: 0.48-0.94, P = 0.022), rSO2 at T4 (OR = 0.61, 95% CI: 0.41-0.89, P = 0.010), and postoperative TΔrSO2% (OR = 0.80, 95% CI: 0.66-0.98, P = 0.028) were independently associated with postoperative delirium in older adults undergoing elective abdominal surgery.

CONCLUSION

The rSO2 measured at T4 and postoperative TΔrSO2% were independently associated with postoperative delirium in older adults undergoing elective abdominal surgery.