Effects of Inhalation versus Total Intravenous Anaesthesia on Long-Term Mortality in Older Patients after Noncardiac Surgery: A Retrospective Observational Study

Academic Background

With the global aging phenomenon, the number of elderly patients undergoing surgery is increasing year by year. Elderly patients are more susceptible to adverse effects of surgery and anesthesia due to decreased organ function and a higher prevalence of comorbidities. Additionally, the sensitivity of elderly patients to anesthetic agents increases, which may lead to delayed postoperative recovery and a higher risk of perioperative complications. Therefore, balancing optimal surgical conditions with minimizing the adverse effects of anesthesia in elderly patients has become a critical issue in the field of anesthesiology.

The choice of anesthesia method is one of the key decisions an anesthesiologist makes when formulating an individualized treatment plan for a patient. Inhalation anesthesia and total intravenous anesthesia (TIVA) are two commonly used maintenance methods. Inhalation anesthesia has been widely used for a long time due to its simplicity, rapid onset, and quick recovery, and it may provide multi-organ protection by reducing inflammatory responses. TIVA, which primarily uses propofol, has advantages such as reduced postoperative nausea and vomiting and smoother emergence from anesthesia. It is also believed to have neuroprotective effects, potentially reducing postoperative cognitive dysfunction in elderly patients. However, there is currently no consensus on the impact of these two anesthesia methods on long-term mortality in elderly patients undergoing noncardiac surgery. Although a Cochrane review found no significant difference in 30-day mortality between inhalation anesthesia and TIVA in elderly noncardiac surgery patients, the evidence is limited due to small sample sizes or low mortality rates. Therefore, this study aims to explore the effects of inhalation anesthesia and TIVA on long-term mortality in elderly noncardiac surgery patients and evaluate their impact on postoperative complications.

Source of the Paper

This paper was co-authored by Ah Ran Oh, Jungchan Park, Jong-Hwan Lee, Joonghyun Ahn, Dongjae Lee, and Seung Yoon Yoo from the Department of Anesthesiology and Pain Medicine at Samsung Medical Center in South Korea. It was published in the British Journal of Anaesthesia, Volume 133, Issue 4, in 2024. The paper was published online on August 5, 2024, with the DOI: 10.1016/j.bja.2024.07.008.

Study Design and Methods

Study Design and Population

This retrospective observational study used data from the Samsung Medical Center-Non Cardiac Operation (SMC-NOCOP) registry, which recorded adult patients who underwent noncardiac surgery at Samsung Medical Center in Seoul, South Korea, between January 2011 and June 2019. Patients under 60 years old, those who did not receive general anesthesia, or those with anesthesia durations of less than 2 hours were excluded, resulting in a final cohort of 45,879 patients. These patients were divided into two groups based on the anesthesia maintenance method: the TIVA group (7,273 patients, 15.9%) and the inhalation anesthesia group (38,606 patients, 84.1%).

Data Collection and Potential Confounders

Data on patient characteristics, social and medical history, preoperative medication history, type of surgery, and surgical risk were collected through the electronic medical record system. The Charlson Comorbidity Index was used to assess the overall health status of the patients. To reduce the influence of confounding factors, the study employed the inverse probability of treatment weighting (IPTW) method for adjustment.

Study Outcomes and Definitions

The primary outcome was all-cause mortality within 1 year after surgery. Secondary outcomes included postoperative complications (postoperative pulmonary complications, perioperative adverse cardiovascular events, and acute kidney injury) as well as 3-year and 5-year mortality rates. Postoperative complications were defined based on International Classification of Diseases codes or clinical definitions.

Anesthesia Management

Anesthesia management was determined by the anesthesiologist based on the patient’s specific condition. Inhalation anesthesia was induced intravenously (using thiopental, propofol, or etomidate) and maintained with inhalation agents (sevoflurane, desflurane, or isoflurane). TIVA was maintained through continuous intravenous infusion of propofol and remifentanil.

Statistical Analysis

The study used the IPTW method to adjust for confounding factors and compared mortality rates between the two groups using Kaplan-Meier analysis and Cox proportional hazards regression models. Postoperative complications were analyzed using logistic regression models. Additionally, subgroup analysis and sensitivity analysis were conducted to validate the robustness of the results.

Study Results

Patient Characteristics

A total of 45,879 patients were included in the study, with 7,273 in the TIVA group and 38,606 in the inhalation anesthesia group. There were some differences in baseline characteristics and perioperative variables between the two groups, but after IPTW adjustment, the variables were well-balanced.

Primary Outcome

The all-cause mortality rate within 1 year after surgery was 5.8% (2,⁶⁴³⁄₄₅,879). The 1-year mortality rate was 4.4% (³²⁰⁄₇,273) in the TIVA group and 6.0% (2,³²³⁄₃₈,606) in the inhalation anesthesia group. After IPTW adjustment, there was no significant association between the type of anesthesia and 1-year mortality (HR=0.95; 95% CI 0.84-1.08).

Secondary Outcomes

The 3-year and 5-year mortality rates were higher in the inhalation anesthesia group, but after IPTW adjustment, there was no significant difference between the two groups. However, the incidence of postoperative complications was significantly higher in the inhalation anesthesia group, including postoperative pulmonary complications (OR=1.30; 95% CI 1.22-1.37), perioperative adverse cardiovascular events (OR=1.34; 95% CI 1.22-1.48), and acute kidney injury (OR=2.19; 95% CI 1.88-2.57).

Subgroup Analysis

Subgroup analysis revealed that the effect of anesthesia type on 1-year mortality differed in female patients and those undergoing emergency surgery. Inhalation anesthesia was associated with increased mortality in female patients (HR=1.24; 95% CI 1.02-1.50) but was associated with reduced mortality in emergency surgery patients (HR=0.70; 95% CI 0.53-0.93).

Sensitivity Analysis

Sensitivity analysis using propensity score matching (PSM) and inverse probability of censoring weighting (IPCW) methods yielded results consistent with the primary analysis, further validating the robustness of the study.

Discussion

This study indicates that the choice of anesthesia method does not significantly affect 1-year mortality in elderly noncardiac surgery patients. However, inhalation anesthesia is associated with an increased risk of postoperative complications, particularly in female patients and those undergoing emergency surgery. The protective effect of inhalation anesthesia in emergency surgery may be related to its role in modulating inflammatory responses.

Conclusion

In elderly patients undergoing noncardiac surgery, the choice of anesthesia method does not affect 1-year mortality. However, the type of anesthesia may have differential effects on mortality in female patients and those undergoing emergency surgery. Both inhalation anesthesia and TIVA can be safely used in elderly patients, and the choice of anesthesia should be tailored based on the patient’s specific condition and the anesthesiologist’s preference.

Study Highlights

1. Large-Sample Retrospective Study: This study included 45,879 elderly patients, providing high statistical power.
2. Long-Term Mortality Assessment: The study not only focused on 1-year mortality but also evaluated 3-year and 5-year mortality, offering a more comprehensive long-term prognosis.
3. Subgroup Analysis: The study revealed the differential effects of anesthesia type on female patients and those undergoing emergency surgery, providing a basis for individualized anesthesia plans.
4. Rigorous Statistical Methods: The study employed multiple statistical methods, including IPTW, PSM, and IPCW, effectively controlling for confounding factors and enhancing the reliability of the results.

Study Significance

This study provides important clinical evidence for the choice of anesthesia method in elderly noncardiac surgery patients. Although the choice of anesthesia does not affect long-term mortality, inhalation anesthesia may increase the risk of postoperative complications, particularly in female patients. Therefore, anesthesiologists should consider the patient’s specific condition and the type of surgery when selecting an anesthesia method to achieve optimal anesthesia outcomes and patient prognosis.