Univent Tube for Thoracoscopic Thymectomy in Myasthenic Patients
Condition: Myasthenia Gravis
MeSH terms: Myasthenia Gravis
Study type: Observational

Summary: 
      This observational study included consecutive MG patients who underwent thoracoscopic
      thymectomy with Univent tube intubation under general anesthesia without NMBAs and combined
      with airway topical anesthesia between January 2016 and December 2019. The investigators
      focus on intubation conditions, surgical conditions, intraoperative respiratory, and airway
      complications
    

Detailed description: 
      This prospective study was conducted on MG patients who underwent thoracoscopic thymectomy
      under general anesthesia without NMBAs using Univent tube at Vietnam Military Hospital 103
      from January 2016 to December 2019. MG was definitively diagnosed based on clinical features,
      electromyography results, and/or circulating antibodies against acetylcholine receptors and
      classified according to the Osserman Classification. Preoperative evaluations included CT
      scans, pulmonary function tests, and routine exams. The operative risk and airway assessments
      were evaluated by expert anesthesiologists and excluded patients with preexisting hoarseness
      or sore throat. This study was approved by Hanoi Medical University's ethics committee
      (No.168-QĐ/ĐHYHN) and Military Hospital 103. All patients were anesthetized and intubated by
      one anesthesiologist assigned to the thoracic surgery unit.

      Anesthesia procedure

      In the operating theatre, the standard monitoring included electrocardiogram (ECG), invasive
      arterial blood pressure (IABP), peripheral oxygen saturation (SpO2), end-tidal capnography
      (EtCO2), ventilation peak and plateau pressures, continuous spirometry, and entropy (response
      entropy-RE and state entropy-SE; Datex Omeda S/5 Advance, GE, USA). Neuromuscular monitoring
      was recorded in the left forearm using TOF (train-of-four)-WatchsSX (Organons, Oss, the
      Netherlands).

      Patients were pre-oxygenated with 100% oxygen for 5 minutes before induction with sufentanil
      at 0.5 µg.kg-1 and propofol at 2-3 mg.kg-1. When patients lost their eyelash reflex,
      lidocaine 10% was initially sprayed in the oral cavity, oropharynx, and upper part of the
      larynx. Subsequently, lidocaine 2% was administered using The MADgic Laryngo-Tracheal Mucosal
      Atomization Device (Teleflex, Wayne, Pennsylvania, USA) to cover the oral cavity, oropharynx,
      larynx, vocal cords, and as deep as possible into the trachea.

      Once the SE value reached 50 or lower, a Univent tube (Fuji Systems, Tokyo, Japan) was
      intubated using conventional direct laryngoscopy. The tube size was standardized based on the
      patient's sex, with an 8.0-mm inner diameter (ID) used for men and a 7.0-mm ID used for
      women. Depending on the side of the chest for approaching the anterior mediastinum, the
      endobronchial blocker was carefully guided into either the right (for a right-sided approach)
      or left mainstem bronchus (for a left-sided approach) using flexible fiberoptic bronchoscopy.
      The tracheal and blocker cuffs were gently inflated, ensuring that the intracuff pressure
      stayed below 30 cmH2O, as measured by a noninvasive manometer. Following the secure
      positioning of patients in a 45° lateral decubitus orientation for surgery, with their heads
      firmly fixed, the correct placement of the blocker was reassessed through bronchoscopy.

      Anesthesia maintenance was guided by Entropy, utilizing either propofol TCI or sevoflurane to
      keep the SE index within the 40-60 range throughout the surgical procedure. Additionally, a
      continuous infusion of sufentanil at 0.2 µg.kg-1.hr-1 was administered, and the patient's
      temperature was carefully regulated with a heating blanket.

      For two-lung ventilation, the ventilator was initially set in A/C mode (FiO2 = 60%,
      respiratory rate of 14 breaths.min-1, tidal volume of 8-10 ml.kg-1, inspiration-expiration
      ratio of 1:2). When establishing one-lung ventilation, investigators adjusted the tidal
      volume (to 5-7 ml.kg-1) and respiratory rate to maintain EtCO2 between 35-40 mmHg and Ppeak <
      35 cmH2O; oxygen was given at 100% and gradually reduced by 10% while aiming for SpO2 > 95%.
      Trocars were placed and the tumor was dissected and removed. Following the insertion of the
      drainage tube, the collapsed lung was inflated and re-ventilated at the end of the surgery.
      Patients meeting extubation criteria were extubated in the operating room; otherwise, they
      were transferred to the postoperative care unit.

      Data collection and criteria

      Characteristics of the study population included demographic data (age, gender, BMI), disease
      characteristics (classification, disease duration, symptoms, diagnostic tests), laboratory
      data, preoperative pulmonary function status, surgical characteristics (tumor features,
      surgical side), and duration of surgery and anesthesia.

      Intubating conditions and intubating variables

      The intubating score was assessed following the consensus conference guidelines on Good
      Clinical Research Practice in Pharmacodynamic Studies of Neuromuscular Blocking Agents. This
      evaluation included laryngoscopy difficulty (categorized as easy, fair, or difficult), vocal
      cord position (described as abducted, intermediate/moving, or closed), and the patient's
      reaction to tracheal tube insertion and cuff inflation (evaluated based on diaphragmatic
      movement/coughing, categorized as none, slight, or vigorous/sustained). These criteria were
      used to assign an overall intubation condition score of excellent, good, or poor.

      Additionally, the following intubation-related variables were recorded: Mallampati score,
      mask ventilation categorized as "easy" (successful mask ventilation with or without an oral
      airway), "difficult" (inadequate or unstable ventilation, requiring two practitioners), or
      "impossible" (unable to ventilate without a muscle relaxant), the number of intubation
      attempts, the time required for intubation and bronchial blocker placement (measured in
      seconds, from the start of laryngoscopy to successful bronchial blocker positioning), and the
      TOF (train-of-four) value at the time of intubation (%).

      Device conditions and surgical variables

      During the surgical procedure, the malposition of the bronchial blocker were noted. After
      opening the pleura and directly examining the lungs, the quality of lung collapse were
      recorded as follows: 1 - spontaneous; 2 - assisted with suction; or 3 - manual. The surgeon
      was asked to provide an overall assessment of lung isolation and rated the surgical
      conditions as follows: 1 - excellent (complete collapse with perfect surgical exposure); 2 -
      fair (total collapse, but the lung still has residual air); 3 - poor (no collapse or partial
      collapse with interference in surgical exposure).

      Respiratory evaluations

      The lung mechanical ventilation parameters, oxygenation, and capnography parameters were
      documented. Arterial blood gas analysis was also performed during two-lung ventilation and
      after 30 minutes of one-lung ventilation. Hypoxemia during surgery was defined as a drop in
      SpO2 below 90% at any point during the intraoperative period.

      Postoperative airway injuries, sore throat, and hoarseness After surgery, all patients
      underwent bronchoscopy examination while still under anesthesia to assess their bronchial
      lesions. Following successful extubation, a flexible laryngoscopy was performed to evaluate
      potential vocal cord injuries. Results from both examinations were recorded and analyzed by
      an experienced ear, nose, and throat specialist. Airway injuries were classified as redness,
      edema, or hematoma.

      Postoperative sore throat and hoarseness were assessed immediately after anesthesia emergence
      and on days 1, 2, and 3 post-surgeries. Sore throat was defined as continuous throat pain and
      postoperative hoarseness was categorized as a change in acoustic quality from the patient's
      previous voice (yes or no). Daily follow-up examinations were conducted until complete
      resolution.
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        MG patients who underwent thoracoscopic thymectomy under general anesthesia without NMBAs
        using Univent tube. MG was definitively diagnosed based on clinical features,
        electromyography results, and/or circulating antibodies against acetylcholine receptors and
        classified according to the Osserman Classification
      
Keywords: Univent tube; thoracoscopic thymectomy; myasthenia gravis; neuromuscular blocking agents