McKeown minimally invasive esophagectomy under discontinuous spontaneous ventilating anesthesia by laryngeal mask: a retrospective non-inferiority cohort study

Introduction

McKeown minimally invasive esophagectomy (MIE-McKeown) has been increasingly employed as the primary surgical approach for treating esophageal cancer. However, traditional esophagectomy involving a thoracic incision and mechanical ventilation is associated with 49.2% respiratory complications, such as pneumonia, prolonged mechanical ventilation and the need for reintubation (1-3).

In recent years, the non-intubated anesthesia by laryngeal mask for video-assisted thoracic surgery (NI-VATS) has been increasingly adopted worldwide. During the thoracic procedure, patients maintain spontaneous breathing while receiving intravenous sedation in combination with locoregional anesthesia (4). NI-VATS can mitigate the adverse effects of mechanical ventilation and minimize the potential injury related to intubation (4). This approach contributes to enhanced postoperative recovery and a reduction in both respiratory and overall morbidity (5).

However, the potential advantages of applying discontinuous spontaneous ventilating anesthesia by laryngeal mask techniques to MIE-McKeown remain uncertain. In the present study, we expand the utilization of discontinuous spontaneous ventilating anesthesia by laryngeal mask for MIE-McKeown, describe and evaluate its feasibility, and compare the perioperative outcomes with conventional intubated technique. We present this article in accordance with the TREND reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2272/rc).

Methods

Study design

Medical records were retrospectively reviewed between October 2022 and September 2024 to identify all patients who underwent MIE-McKeown (n=33). The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the First Affiliated Hospital of Guangzhou Medical University Research Ethics Committee (No. 2020-69), and individual consent for this retrospective analysis and case series study was signed and collected from the patients. Their medical data and images were demonstrated with their official permission. The patients were divided into two groups depending on the anesthesia technique, and were not randomized to Group A or Group B, since this study was retrospective. To ensure the non-inferiority of discontinuous spontaneous ventilating anesthesia by laryngeal mask, non-inferiority margin for each outcome indicator was preset, and the specific values are provided below. The patient who received discontinuous spontaneous ventilating anesthesia by laryngeal mask was in Group A. The patient in Group B received bronchial blocker for single-lung ventilation.

Preoperative assessment

All patients received preoperative assessment for surgery, including electrocardiogram, echocardiogram, chest and abdomen computed tomography (CT), ultrasound of the neck, pulmonary function analysis and fiberoptic esophagoscopy.

Criteria of discontinuous spontaneous ventilating anesthesia by laryngeal mask for MIE-McKeown

• Cytological or histological diagnosis of esophageal cancer.
• Age 18–75 years old.
• Clinical stage I–III.
• American Society of Anesthesiologists (ASA) standard grade I–III.
• Body mass index (BMI) <26 kg/m².
• Patients with no clinically significant cardiac history, such as rhythm disturbances, ischemic heart disease or valvular heart disease.
• Patients with no clinically significant pulmonary history, such as bronchiectasis or tuberculosis.
• Patients with no medical history of ipsilateral pulmonary surgery or other conditions which may result in extensive pleural adhesion.

Exclusion criteria of discontinuous spontaneous ventilating anesthesia by laryngeal mask for MIE-McKeown

• Patients with severe pleural adhesion on the operative side.
• Patients with bronchiectasis and excessive phlegm.
• Patients with intracranial hypertension, pulmonary hypertension, and cerebrovascular malformations.
• Patients with valvular heart disease, coronary heart disease.

Anesthetic management in discontinuous spontaneous ventilating anesthesia by laryngeal mask for MIE-McKeown

Monitoring consisted of electrocardiography (ECG), pulse oxygen saturation (SpO₂), invasive blood pressure (IBP), end-tidal carbon dioxide (EtCO₂) and bispectral index (BIS). The arterial blood gases (ABG) were intermittently monitored.

We inserted a thoracic epidural catheter (T_8–9/T_7–8) with 0.5% ropivacaine infusion rate at 5 mL/h. Anesthesia was induced with propofol by target control infusion (TCI) (2–3 µg/mL), dexmedetomidine (1 µg/kg/h) and sufentanil (0.2 µg/kg). The laryngeal mask airway (LMA) was placed when BIS lowered below 60. A right radial artery catheter and a central venous catheter were inserted.

During the surgery, propofol (TCI) 1.0–2.5 µg/mL, remifentanil 0.03–0.08 µg/kg/min, and dexmedetomidine 0.5 µg/kg/h were continually infused according to BIS (target range, 40–60). The surgeon performed thoracic vagus nerve block on the surgical side after thoracotomy. We induced spontaneous ventilation by manually-assisted ventilation or by reducing anesthetic doses. Patients had spontaneous ventilation during thoracic procedure, which avoided lung injury caused by one-lung mechanical positive pressure ventilation. After the thoracic procedure, the right collapsed lung was inflated with hand-controlled positive pressure. The sealing pressure of the silicone double-tube laryngeal mask can reach 40 cmH₂O, which is enough to meet the pressure of 20 cmH₂O needed for lung inflation. Adjusting anesthetic doses and conversion to synchronized intermittent mechanical ventilation (SIMV) during abdominal and cervical procedures. At this time, due to the two-lung ventilation, the airway pressure is depressed, which can avoid lung injury to the patient. After anastomosing the gastric conduit and the proximal end of the esophagus, a jejunal nutrition tube was indwelled through the deflated cuff of LMA. Patients were transferred to the intensive care unit (ICU) according to the intraoperative and anesthesia situations.

Surgical techniques

All patients underwent MIE-McKeown and achieved the R0 resection standard. The abdominal and cervical procedures are similar to MIE-McKeown under conventional anesthesia, with the main difference being thoracic procedure. The patient was placed on the left lateral decubitus position with 30° anteversion. When applying discontinuous spontaneous ventilating anesthesia by laryngeal mask, we employ a length of 4 cm incision for single-port thoracoscopic technique. When applying conventional intubated anesthesia, we employ three-port thoracoscopic approach and establish artificial pneumothorax (6 mmHg). The mediastinal pleura was incised, and the esophagus was meticulously dissected from the thoracic inlet to the esophageal hiatus at the level of the diaphragm. Then the lymph nodes around the left and right recurrent laryngeal nerves (RLNs) were dissected, as well as lymph nodes adjacent to the esophagus and trachea. It’s worth noting that when applying discontinuous spontaneous ventilating anesthesia by laryngeal mask, due to the absence of an endotracheal airway device, it is necessary to carefully dissect the lymph nodes below the carina to avoid causing iatrogenic airway obstruction. For the abdominal and neck phase of MIE-McKeown, the patient was placed in the supine position. Blunt dissection of the omentum is performed, and the short gastric vessels are dissected. The gastrosplenic ligament is separated, the cardia is freed, the lesser curvature of the stomach is mobilized, the abdominal main lymph nodes and perigastric lymph nodes are removed, and the left gastric vessels are ligated. A 6-cm incision was made under the xiphoid process, the stomach was pulled out, the esophagus was severed at the cardia, and the stomach was freed to the pylorus to make a tubular stomach. In the neck, a 5-cm longitudinal incision was made along the medial edge of the sternocleidomastoid muscle. The cervical esophagus was dissected, and the tubular stomach was lifted to the neck through the esophageal bed and the anastomosis of the tubular stomach and esophagus was performed.

Outcome indicators

Differences in intraoperative and postoperative outcomes between the two groups were compared. Among them, the lowest SpO₂ and peak EtCO₂ were the primary outcome indicators. Operation time, anesthesia time, blood loss, postoperative complication rate, ICU stay and hospital days were the secondary outcome indicators.

Statistical analysis

Categorical variables were presented as a count and percentage. Normally-distributed measurement data are presented as mean ± standard deviation, while non-normally distributed measurement data were presented as median (interquartile range). t-test was used for normally distributed data and Wilcoxon’s ranked sum test for non-normally distributed data. A P value <0.05 was statistically significant. All statistical analyses were performed on a per-protocol basis using R software version 4.4.1 (2024-06-14 ucrt). A one-sided non-inferiority test was conducted for the primary outcome by comparing the 95% confidence intervals (CIs) from unpaired t-tests between groups for the lowest SpO₂ levels and the peak EtCO₂ levels against the predefined non-inferiority margins.

Results

A total of 33 patients underwent MIE-McKeown in our center between October 2022 and September 2024. Twenty (60.6%) patients in Group A and 13 (39.4%) in Group B for MIE-McKeown.

The clinical characteristics of the patients are shown in Table 1. Age, BMI, comorbidities, pre-operative forced expiratory volume in 1 s percent predicted (FEV1%) and smoking history of Group A were not different from Group B. However, there were no females in Group A compared to 5 females in Group B (0 vs. 5, P=0.18). The FEV1 of Group A was greater than that of Group B (2.80 vs. 1.98, P<0.001).

All surgeries were performed by one surgical team. In Group A, 10 patients received thoracic epidural anesthesia (TEA) at T_8–9 level while 6 patients received TEA at T_7–8 level.

Primary outcomes

Figure 1 demonstrates the mean differences in the lowest SpO₂ between the two groups. The non-inferiority analysis focused on the lowest SpO₂ and peak EtCO₂ levels at various surgical procedures, comparing the outcomes between Group A and Group B.

Figure 1 Forest plot of lowest SpO₂ levels. CI, confidence interval; SpO₂, pulse oxygen saturation.

Lowest SpO₂ levels

The mean difference of the lowest SpO₂ in thoracic procedure and the lower limit of 95% CI of the mean difference of the lowest SpO₂ in cervical procedure and abdominal procedure were higher than the predefined noninferiority margin of −3.

• Thoracic procedure: the mean lowest SpO₂ was 96.90%±3.63% in Group A and 98.54%±1.71% in Group B. The mean difference was −1.64% (95% CI: −3.48% to 0.20%).
• Cervical procedure: the mean lowest SpO₂ was 99.80%±0.51% in Group A and 99.62%±0.77% in Group B. The mean difference was 0.18% (95% CI: −0.29% to 0.66%).
• Abdominal procedure: the mean lowest SpO₂ was 99.75%±0.54% in Group A and 99.85%±0.38% in Group B. The mean difference was −0.10% (95% CI: −0.41% to 0.22%).

These results indicated that discontinuous spontaneous ventilating anesthesia by laryngeal mask was non-inferior to intubated anesthesia in maintaining the lowest SpO₂ across all surgical procedures.

Peak EtCO₂ levels

Figure 2 shows that the upper limit of 95% CI of the mean differences in peak EtCO₂ between the two groups during cervical and abdominal procedures was within the predefined non-inferiority margin of 5, while the thoracic procedure exceeded the margin, suggesting inferiority in that procedure.

• Thoracic procedure: the mean peak EtCO₂ was 57.05±9.12 mmHg in Group A and 45.38±3.97 mmHg in Group B. The mean difference was 11.67 mmHg (95% CI: 6.99 to 16.34), exceeding the non-inferiority margin.
• Cervical procedure: the mean peak EtCO₂ was 38.40±4.43 mmHg in Group A and 36.69±1.38 mmHg in Group B. The mean difference was 1.86 mmHg (95% CI: −0.23 to 3.95).
• Abdominal procedure: the mean peak EtCO₂ was 44.65±3.72 mmHg in Group A and 43.23±3.40 mmHg in Group B. The mean difference was 1.37 mmHg (95% CI: −1.18 to 3.91).

Figure 2 Forest plot of peak EtCO₂ levels. CI, confidence interval; EtCO₂, end-tidal carbon dioxide.

These findings suggest that discontinuous spontaneous ventilating anesthesia by laryngeal mask achieved non-inferiority in the cervical and abdominal procedures but not in the thoracic procedure concerning the peak EtCO₂.

Secondary outcomes

Two groups had comparable operation time, anesthesia time and blood loss. None of the patients required conversion to intubated anesthesia in Group A. None of the patients required thoracotomy in two groups (Table 2).

After surgery, eight patients in Group A and 10 patients in Group B were transferred to ICU. There were no statistically significant differences observed among postoperative ICU stay (0 vs. 1, P=0.17) and postoperative hospital stay data analyzed (11 vs. 11, P=0.57). Postoperative complications occurred in three patients in Group A and four patients in Group B (Table 3). In Group A, pleural effusion occurred in one patient, which was managed with thoracocentesis, and respiratory failure occurred in two patients one day after esophagectomy. In Group B, respiratory failure occurred in two patients and paralysis of RLN occurred in one patient. There were no cases of perioperative mortality.

Discussion

To the best of our knowledge, this is the first study to describe and assess the techniques of discontinuous spontaneous ventilating anesthesia by laryngeal mask for MIE-McKeown and compare the outcomes with the conventional intubated techniques. The perioperative outcomes of this study show that discontinuous spontaneous ventilating anesthesia by laryngeal mask is feasible and as safe as intubated techniques for MIE-McKeown.

The technique of NI-VATS has been developed worldwide over the last decade (6,7). During the surgery, the patient has spontaneous breathing without intubation under mild sedation in combination with a locoregional anaesthetic technique. Our center started NI-VATS program since 2011, and we have now accomplished NI-VATS in the management of lobectomy, sleeve lobectomy, mediastinal mass resection, and even tracheal resection and reconstruction (8-10). The advantages of NI-VATS are less respiratory complications and shorter hospital stay, particularly in elderly patients and in those with compromised respiratory function (11). However, the discontinuous spontaneous ventilating anesthesia by laryngeal mask is mostly applied for pulmonary surgery and tracheal surgery. Until 2021, Xu et al. first reported that 3 patients underwent MIE-McKeown under spontaneous ventilating anesthesia by LMA (12). Two of them were accomplished under discontinuous spontaneous ventilating anesthesia by laryngeal mask, the subsequently abdominal and cervical procedure was managed under LMA with appropriate muscle relaxation. One patient converted to intubation due to hypercapnia (EtCO₂ >75 mmHg). This new attempt suggested the feasibility of applying discontinuous spontaneous ventilating anesthesia by laryngeal mask for MIE-McKeown.

This pilot study compared perioperative outcomes of discontinuous spontaneous ventilating anesthesia by laryngeal mask and the conventional intubated techniques for MIE-McKeown. The data showed that discontinuous spontaneous ventilating anesthesia by laryngeal mask for MIE-McKeown in this setting was as safe as conventional intubated techniques. By comparing the lowest SpO₂ and peak EtCO₂ between the two groups, we found that the perioperative vital signs of group A were non-inferior to group B. The preoperative data of subgroups were equivalent. The postoperative ICU stays, postoperative hospital stay and complications were equivalent in two groups.

There are some concerns with discontinuous spontaneous ventilating anesthesia by laryngeal mask for MIE-McKeown. The main concern is hypoxemia. In our study, SpO₂ dropped to 92% in one patient during thoracic procedure, and it was managed by reducing the dose of anesthetic and manually assisted ventilation. The lowest SpO₂ during thoracic procedure was 96.90%±3.63%, and no patient had anesthesia conversion due to persistent hypoxemia. A previous study reported the incidence of hypoxemia during NI-VATS was low (13). After thoracotomy, iatrogenic pneumothorax created and the operated lung collapses gradually. The airway resistance of the operated lung is higher than that of the non-operated lung, contributing to most ventilated gases enter the contralateral lung. Due to the effect of gravity, the pulmonary blood is more distributed in the non-operated lung. Therefore, blood shunt is improved and oxygenation is maintained (10).

The second concern is hypercapnia. Due to decreased minute ventilation during thoracic procedure and carbon dioxide pneumoperitoneum in abdominal procedure, hypercapnia is common in these two procedures of MIE-McKeown. In our study, hypercapnia were observed and tolerated in all patients and it did not cause tachypnoea or arrhythmia. After switching to two lung ventilation in cervical procedure, we observed a gradual decrease in arterial partial pressure of carbon dioxide (PaCO₂) values. A study has proposed that permissive hypercapnia, defined as PaCO₂ between 45 and 55 mmHg during major surgeries, results in increased cerebral oxygen saturation and a lower incidence of postoperative delirium compared to targeting normocapnia, while maintaining equivalent postoperative cognitive function (14). In our study, even though EtCO₂ levels were significantly higher in the spontaneous breathing group than in the intubation group during thoracic procedures, they still fell within the definition of permissive hypercapnia. Furthermore, no significant hypoxemia was observed, confirming the acceptability and safety of this approach (15).

The third concern is the potential risk of aspiration. We used a visual second-generation LMA as an airway device, which has higher sealing pressure and a gastric drainage channels (16). The vision of glottis can be checked during the surgery. To reduce the incidence of aspiration, esophageal ligation was performed in the initial phase of thoracic procedure. Numerous studies have now demonstrated that second-generation LMA with esophageal drainage tube can be safely used in patients undergoing laparoscopic surgeries without difficult ventilation or an increase in the risk of aspiration (17-19).

To ensure patient safety, the anesthesia conversion criteria were determined before the operation (Table 4). In addition, the anesthesiologists should be able to intubate in the lateral decubitus position and accomplish anesthesia conversion in a short time during operation. A bronchial blocker is the primary choice for anesthesia conversion, then confirmed under fiberoptic bronchoscopy.

The limitations of this pilot study include the following: (I) it is a retrospective study; (II) the sample size is too small to assess whether discontinuous spontaneous ventilating anesthesia by laryngeal mask technique improves outcome after MIE-McKeown; (III) there is significant selection bias in this study. In conclusion, discontinuous spontaneous ventilating anesthesia by laryngeal mask technique appears safe and equivalent to conventional intubated anesthesia for MIE-McKeown as evidenced by equivalent perioperative outcomes. The following studies should focus on whether discontinuous spontaneous ventilating anesthesia by laryngeal mask improves postoperative outcome after MIE-McKeown in poor respiratory function patients.

Conclusions

This study demonstrates that discontinuous spontaneous ventilating anesthesia by laryngeal mask with spontaneous breathing is a feasible and safe technique for MIE-McKeown. The results indicate that discontinuous spontaneous ventilating anesthesia by laryngeal mask achieves comparable perioperative outcomes to conventional intubated anesthesia, including non-inferior levels of lowest SpO₂ during all surgical stages and tolerable levels of peak EtCO₂, even though thoracic procedures showed higher values. Importantly, no severe complications or anesthesia conversions were required in the non-intubated group. Therefore, under strict preoperative evaluation and skillful surgical technique, discontinuous spontaneous ventilating anesthesia by laryngeal mask can be used as a valid alternative method for MIE-McKeown under conventional intubation anesthesia.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the TREND reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2272/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2272/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2272/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2272/coif). J.H. serves as an unpaid Executive Editor-in-Chief of Journal of Thoracic Disease. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Research Ethics Committee of the First Affiliated Hospital of Guangzhou Medical University (No. 2020-69), and individual consent for this retrospective analysis and case series study was signed and collected from the patients. Their medical data and images were demonstrated with their official permission.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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