Effects of intra-operative end-tidal carbon dioxide levels on the rates of post-operative complications in adults undergoing general anesthesia for percutaneous nephrolithotomy: A clinical trial

Intraoperative end-tidal carbon dioxide levels are not associated with recurrence-free survival after elective pancreatic cancer surgery: a retrospective cohort study

Background

Intraoperative end-tidal carbon dioxide concentrations (EtCO2) values are associated with recurrence-free survival after colorectal cancer surgery. However, it is unknown if similar effects can be observed after other surgical procedures. There is now evidence available for target EtCO2 and its relation to surgical outcomes following pancreatic cancer surgery.

Methods

In this single-center, retrospective cohort study, we analyzed 652 patients undergoing elective resection of pancreatic cancer at Heidelberg University Hospital between 2009 and 2016. The entire patient cohort was sorted in ascending order based on mean intraoperative EtCO2 values and then divided into two groups: the high-EtCO2 group and the low-EtCO2 group. The pre-specified primary endpoint was the assessment of recurrence-free survival up to the last known follow-up. Cardiovascular events, surgical site infections, sepsis, and reoperations during the hospital stay, as well as overall survival were pre-specified secondary outcomes.

Results

Mean EtCO2 was 33.8 mmHg ±1.1 in the low-EtCO2 group vs. 36.8 mmHg ±1.9 in the high-EtCO2 group. Median follow-up was 2.6 (Q1:1.4; Q3:4.4) years. Recurrence-free survival did not differ among the high and low-EtCO2 groups [HR = 1.043 (95% CI: 0.875-1.243), log rank test: p = 0.909]. Factors affecting the primary endpoint were studied via Cox analysis, which indicated no correlation between mean EtCO2 levels and recurrence-free survival [Coefficient -0.004, HR = 0.996 (95% CI:0.95-1.04); p = 0.871]. We did not identify any differences in the secondary endpoints, either.

Conclusions

During elective pancreatic cancer surgery, anesthesiologists should set EtCO2 targets for reasons other than oncological outcome until conclusive evidence from prospective, multicenter randomized controlled trials is available.

Low intraoperative end-tidal carbon dioxide levels are associated with improved recurrence-free survival after elective colorectal cancer surgery

STUDY OBJECTIVE

Higher levels of carbon dioxide (CO2) increase the invasive abilities of colon cancer cells in vitro. Studies assessing target values for end-tidal CO2 concentrations (EtCO2) to improve surgical outcome after colorectal cancer surgery are lacking. Therefore, we evaluated whether intraoperative EtCO2 was associated with differences in recurrence-free survival after elective colorectal cancer (CRC) surgery.

DESIGN

Single center, retrospective analysis.

SETTING

Anesthesia records, surgical databases and hospital information system of a tertiary university hospital.

PATIENTS

We analyzed 528 patients undergoing elective resection of colorectal cancer at Heidelberg University Hospital between 2009 and 2018.

INTERVENTIONS

None.

MEASUREMENTS

Intraoperative mean EtCO2 values were calculated. The study cohort was equally stratified into low-and high-EtCO2 groups. The primary endpoint measure was recurrence-free survival until last known follow-up. Groups were compared using Kaplan-Meier analysis. Cox-regression analysis was used to control for covariates. Sepsis, reoperations, surgical site infections and cardiovascular events during hospital stay, and overall survival were secondary outcomes.

MAIN RESULTS

Mean EtCO2 was 33.8 mmHg ±1.2 in the low- EtCO2 group vs. 37.3 mmHg ±1.6 in the high-EtCO2 group. Median follow-up was 3.8 (Q1-Q3, 2.5-5.1) years. Recurrence-free survival was higher in the low-EtCO2 group (log-rank-test: p = .024). After correction for confounding factors, lower EtCO2 was associated with increased recurrence-free survival (HR = 1.138, 95%-CI:1.015-1.276, p = .027); the hazard for the primary outcome decreased by 12.1% per 1 mmHg decrease in mean EtCO2. 1-year and 5-year survival was also higher in the low-EtCO2 group. We did not find differences in the other secondary endpoints.

CONCLUSIONS

Lower intraoperative EtCO2 target values in CRC surgery might benefit oncological outcome and should be evaluated in confirmative studies.

Ventilation Strategies During General Anesthesia for Noncardiac Surgery: A Systematic Review and Meta-Analysis

BACKGROUND

The optimal ventilation strategy during general anesthesia is unclear. This systematic review investigated the relationship between ventilation targets or strategies (eg, positive end-expiratory pressure [PEEP], tidal volume, and recruitment maneuvers) and postoperative outcomes.

METHODS

PubMed and Embase were searched on March 8, 2021, for randomized trials investigating the effect of different respiratory targets or strategies on adults undergoing noncardiac surgery. Two investigators reviewed trials for relevance, extracted data, and assessed risk of bias. Meta-analyses were performed for relevant outcomes, and several subgroup analyses were conducted. The certainty of evidence was evaluated using Grading of Recommendations Assessment, Development and Evaluation (GRADE).

RESULTS

This review included 63 trials with 65 comparisons. Risk of bias was intermediate for all trials. In the meta-analyses, lung-protective ventilation (ie, low tidal volume with PEEP) reduced the risk of combined pulmonary complications (odds ratio [OR], 0.37; 95% confidence interval [CI], 0.28-0.49; 9 trials; 1106 patients), atelectasis (OR, 0.39; 95% CI, 0.25-0.60; 8 trials; 895 patients), and need for postoperative mechanical ventilation (OR, 0.36; 95% CI, 0.13-1.00; 5 trials; 636 patients). Recruitment maneuvers reduced the risk of atelectasis (OR, 0.44; 95% CI, 0.21-0.92; 5 trials; 328 patients). We found no clear effect of tidal volume, higher versus lower PEEP, or recruitment maneuvers on postoperative pulmonary complications when evaluated individually. For all comparisons across targets, no effect was found on mortality or hospital length of stay. No effect measure modifiers were found in subgroup analyses. The certainty of evidence was rated as very low, low, or moderate depending on the intervention and outcome.

CONCLUSIONS

Although lung-protective ventilation results in a decrease in pulmonary complications, randomized clinical trials provide only limited evidence to guide specific ventilation strategies during general anesthesia for adults undergoing noncardiac surgery.

Association between intraoperative end-tidal carbon dioxide and postoperative nausea and vomiting in gynecologic laparoscopic surgery

Gynecologic laparoscopic surgery has a high incidence of postoperative nausea and vomiting (PONV). Studies suggest that low intraoperative end-tidal carbon dioxide (EtCO₂) is associated with an increased incidence of PONV, but the results have not been consistent among studies. This study investigated the association between intraoperative EtCO₂ and PONV in patients undergoing gynecologic laparoscopic surgeries under general anesthesia. This retrospective cohort study involved patients who underwent gynecologic laparoscopic surgeries under general anesthesia at Kyoto University Hospital. We defined low EtCO₂ as a mean EtCO₂ of < 35 mmHg. Multivariable modified Poisson regression analysis examined the association between low EtCO₂ and PONV during postoperative two days and the postoperative length of hospital stay (PLOS). Of the 739 patients, 120 (16%) had low EtCO₂, and 430 (58%) developed PONV during postoperative two days. There was no substantial association between low EtCO₂ and increased incidence of PONV (adjusted risk ratio: 0.96; 95% confidence interval [CI] 0.80–1.14; p = 0.658). Furthermore, there was no substantial association between low EtCO₂ and prolonged PLOS (adjusted difference in PLOS: 0.13; 95% CI − 1.00 to 1.28; p = 0.816). Intraoperative low EtCO₂, specifically a mean intraoperative EtCO₂ below 35 mmHg, was not substantially associated with either increased incidence of PONV or prolonged PLOS.

Forecasting adverse surgical events using self-supervised transfer learning for physiological signals

Hundreds of millions of surgical procedures take place annually across the world, which generate a prevalent type of electronic health record (EHR) data comprising time series physiological signals. Here, we present a transferable embedding method (i.e., a method to transform time series signals into input features for predictive machine learning models) named PHASE (PHysiologicAl Signal Embeddings) that enables us to more accurately forecast adverse surgical outcomes based on physiological signals. We evaluate PHASE on minute-by-minute EHR data of more than 50,000 surgeries from two operating room (OR) datasets and patient stays in an intensive care unit (ICU) dataset. PHASE outperforms other state-of-the-art approaches, such as long-short term memory networks trained on raw data and gradient boosted trees trained on handcrafted features, in predicting six distinct outcomes: hypoxemia, hypocapnia, hypotension, hypertension, phenylephrine, and epinephrine. In a transfer learning setting where we train embedding models in one dataset then embed signals and predict adverse events in unseen data, PHASE achieves significantly higher prediction accuracy at lower computational cost compared to conventional approaches. Finally, given the importance of understanding models in clinical applications we demonstrate that PHASE is explainable and validate our predictive models using local feature attribution methods.

Hypercapnia versus normocapnia for emergence from desflurane anaesthesia: Single-blinded randomised controlled study

BACKGROUND

Rapid emergence from general anaesthesia is desirable only if safety is not sacrificed. Mechanical hyperventilation during hypercapnia produced by carbon dioxide infusion into the inspired gas mixture or by rebreathing was reported to shorten emergence time from inhalation anaesthesia.

OBJECTIVES

To test the hypothesis that hypercapnia produced by hypoventilation before desflurane cessation shortens emergence time from general anaesthesia (primary hypothesis) and reduces undesirable cardiorespiratory events.

DESIGN

A single-blinded randomised controlled study.

SETTING

A single university hospital.

PATIENTS

Fifty adult patients undergoing elective abdominal surgery under general anaesthesia using desflurane inhalation and intra-operative epidural anaesthesia.

INTERVENTION

The patients were randomly assigned to either the normocapnia or hypercapnia group.

MAIN OUTCOME MEASURES

Emergence time from desflurane anaesthesia and comparison of the incidence of 11 predefined undesirable cardiorespiratory events during and after emergence from anaesthesia between the groups.

RESULTS

Forty-six patients were included in the analysis. End-tidal carbon dioxide concentrations at cessation of desflurane were 35 ± 6 mmHg (mean ± SD) and 52 ± 6 mmHg in normocapnia (n = 23) and hypercapnia groups (n = 23), respectively. Emergence time was significantly faster in the hypercapnia group than the normocapnia group: 9.4 ± SD min, hypercapnia: 5.5 ± 2.6 min, (P < 0.001) with a difference of 3.8 min on average (95% CI: 2.4 to 5.3). Spontaneous breathing established before recovery of consciousness was more evident in hypercapnia patients (normocapnia: 13%, hypercapnia: 96%, P < 0.001). Hypercapnia patients had more episodes of bradypnoea and apnoea before emergence of consciousness. In contrast, after tracheal extubation, incidences of bradypnoea and hypopnoea were more common in the normocapnia group. Undesirable cardiovascular events were not common, and no group differences were observed during emergence and postextubation periods.

CONCLUSION

Hypoventilation-induced hypercapnia before desflurane cessation shortens the emergence time without causing additional clinically significant undesirable events.

TRIAL REGISTRATION

UMIN Clinical Trials Registry (UMIN000020143) https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi?function=brows&recptno=R000023266&language=E.

Impact of intraoperative hypocapnia on postoperative complications in laparoscopic surgery for colorectal cancer

PURPOSE

In laparoscopic surgery (LS) for colorectal cancer (CRC), the relationship between intraoperative end-tidal carbon dioxide concentration (EtCO₂) and surgery-related complications remains unexplored. This study assessed the impact of intraoperative EtCO₂ on postoperative complications in LS for CRC.

METHODS

In total, 909 patients who underwent LS for CRC were enrolled. Hypocapnia and hypercapnia were defined as EtCO₂ < 35 mmHg and > 40 mmHg, respectively, and the relationships between hypocapnia or hypercapnia duration and postoperative complications were analyzed.

RESULTS

The median (range) durations of hypocapnia and hypercapnia were 2.0 (0-8.3) h and 0.3 (0-5.8) h, respectively. Complications were observed in 208 cases (23.0%), which included 37 (4.1%) instances of anastomotic leakage and 86 (9.5%) of superficial surgical site infection (SSI). While the hypercapnia duration was not associated with the short-term outcomes, prolonged hypocapnia was significantly correlated with complications (p = 0.02), specifically superficial SSI (p = 0.005). Multivariate analyses adjusted for confounding factors confirmed that hypocapnia prolongation was an independent risk factor for postoperative superficial SSI [OR 1.19; 95% confidence interval (Cl) 1.03-1.36, p = 0.01].

CONCLUSION

Intraoperative hypocapnia may be a risk factor for postoperative complications, in particular superficial SSI, in LS for CRC.

Correlation of Intraoperative End-Tidal Carbon Dioxide Concentration on Postoperative Hospital Stay in Patients Undergoing Pylorus-Preserving Pancreaticoduodenectomy

Background

Hypocapnia has been traditionally advocated during general anesthesia, even though it may induce deleterious physiological effects that result in unfavorable outcomes in patients. This study investigated the association between intraoperative end-tidal carbon dioxide (EtCO₂) and length of hospital stay (LOS) in patients who underwent pylorus-preserving pancreaticoduodenectomy (PPPD).

Methods

The medical records of 759 patients from 2006 to 2015 were reviewed. The patients were divided into two groups based on the mean EtCO₂ value during general anesthesia: the hypocapnia group (< 35 mmHg) and the normocapnia group (≥ 35 mmHg). The primary outcome was LOS between the groups. Secondary outcomes included the length of intensive care unit (ICU) stay, postoperative 30-day, 1-year, and 2-year mortality, and perioperative factors associated with LOS.

Results

A total of 727 patients were finally analyzed. The median LOS of the hypocapnia group was significantly longer than that of the normocapnia group (22 days vs. 18 days, respectively; p < 0.001). Postoperative mortality did not differ between the groups. Cox regression analysis revealed that hypocapnia was an independent risk factor for longer LOS (hazard ratio [HR], 1.61; 95% confidence interval [CI], 1.37–1.89; p < 0.001). Age and postoperative pancreatic fistula were also risk factors for a longer LOS.

Conclusions

It was concluded that low levels of intraoperative EtCO₂ during general anesthesia were associated with an increased LOS for patients undergoing PPPD.

The association of intraoperative end-tidal carbon dioxide with the risk of postoperative nausea and vomiting

PURPOSE

Patients undergoing gynecological surgery are considered to be a high-risk cohort for postoperative nausea and vomiting (PONV). The purpose of this study was to assess the association of intraoperative end-tidal carbon dioxide (EtCO₂) with risk of PONV in patients underwent gynecological open surgery.

METHODS

In this single-center retrospective observational study, we included patients aged 20-60 years who underwent elective gynecological open surgery. We obtained data for the incidence of PONV within 24 h after operation. We collected EtCO₂ every minute during the operation, and determined the lowest value of EtCO₂. We compared the lowest EtCO₂ between patients with and without PONV. Multivariate logistic regression analysis was performed to assess the independent association of EtCO₂ with the risk of PONV.

RESULTS

A total of 146 patients were included in the current study. There were 81 patients with PONV within 24 h after the operation. The median lowest value of EtCO₂ in patients with PONV was significantly lower than that in patients without PONV (31 vs 33 mmHg, p = 0.02). In the multivariate logistic regression model, we found that lowest EtCO₂ ≤ 31 mmHg was independently associated with increase in the risk of PONV (adjusted odds ratio = 3.37, p = 0.02).

CONCLUSION

In this retrospective observational study, low intraoperative EtCO₂ was shown to be independently associated with increased risk of PONV. However, this result may be skewed by uncollected information including previous PONV, motion sickness or other unknown bias, so future studies should be conducted to refute or confirm our findings.