This retrospective study was approved by the Research Board of the National Medical Center (Institutional Review Board number: H-1806-091-003). We retrospectively investigated the medical records of MG patients who underwent BVET between August 2016 and January 2018.
The inclusion criteria were as follows: age 18–65 years, American Society of Anesthesiologists (ASA) physical status I–III, preoperative vital capacity (VC) > 2 L, no history of sternotomy, and no cardiothoracic disease. Patients who underwent conversion from OLV to TLV or changed VATS to sternotomy were excluded. We divided patients into two groups: group D (the double-lumen tube [DLT] group), including patients who underwent ventilation for one lung, and group S (the single-lumen tube [SLT] group), including those who underwent ventilation for two lungs during surgery. Finally, 83 patients were enrolled in the present study.
We set nine anesthesia time points (T0–T8) and collected the data. The time points were set as follows: T0 was immediately after tracheal intubation, T1 was the time of incision on the right side, T2 was set as 10 min after the CO2 gas insufflation of the right lung, T3 was set as 30 min from the right lung CO2 gas insufflation, T4 referred to the transition period from the right to the left side (in group D, TLV), T5 was the time of incision on the left side, T6 was set as 10 min after the CO2 gas insufflation of the left lung, T7 was set as 30 min after the left lung CO2 gas insufflation, and T8 referred to the end of the left side operation (in group D, TLV).
The basic characteristics of the patients, such as age, sex, body mass index (BMI), ASA physical status, Myasthenia Gravis Foundation of America (MGFA) class, operation, and anesthesia time were recorded. The end-tidal CO2 (EtCO2), peak inspiratory pressure (PIP), respiratory rate (RR), peripheral capillary oxygen saturation (SpO2), PaO2, FiO2, arterial oxygen index (PaO2/FiO2), mean blood pressure (MBP), heart rate (HR), and cardiac index (CI) were recorded at T0–T8. Postoperative complications, intensive care unit stay time, and hospitalization day (HD) were also recorded.
None of the patients received premedication. Intraoperative monitoring included noninvasive blood pressure measurement, invasive arterial blood pressure monitoring, electrocardiography, pulse oximetry, capnography, bispectral index (BIS) monitoring, and neuromuscular function assessment (TOF Watch SX monitor®, Organon, Ireland). General anesthesia was induced using total intravenous anesthesia. Propofol and remifentanil were administered to the end organ concentrations of 4–5 and 3–4 ng/mL, respectively, using a target-controlled infusion pump (Orchestra®, Fresenius Vial, France). Rocuronium (0.6 mg/kg) was administered to facilitate intubation. In group D, a 35-F or 37-F left-sided DLT was inserted using videolaryngoscopy, and its correct position was confirmed by auscultation and eventually by bronchoscopy. In group S, a 7.0 mm or 8.0 mm I.D single-lumen tube was inserted using videolaryngoscopy. Mechanical ventilation with O2 and air (FiO2, 0.5) was started with tidal volumes (TVs) of 8–10 ml/kg and an initial RR of 9–10 breath/min. In group D, passive lung collapse and contralateral OLV were started just before the first trocar insertion. During OLV, the FiO2 was adjusted to 0.5–1.0, the TV was reduced to 6–8 ml/kg to maintain a PIP of < 35 cm H2O, and the RR was increased to avoid respiratory acidosis. In group S, the TV was reduced to 6–8 ml/kg. Propofol and remifentanil infusions were titrated to maintain an MBP within 20% of the baseline during anesthesia and to maintain BIS < 50. Rocuronium was continuously injected to maintain a TOF count of 1 or 2. A radial arterial pressure line was placed, and a central venous catheter was inserted via the right internal jugular vein. CI was monitored using a minimally invasive hemodynamic monitor (FloTrac System®, Edwards Lifesciences, USA).
The BVET was performed with patients in the supine position with 15° reverse Trendelenburg position. Both arms were placed at the 90° forearm abduction external rotation position without any pressure on the brachial plexus nerve. The right-side approach was always performed first. First, a 5-mm trocar was placed along the upper edge of the fifth intercostal space in the midaxillary line. After inspecting the right thoracic cavity to evaluate the adhesions and pathology, CO2 insufflation was installed using a pressure limit of 8–14 mmHg and a flow of 4 L/min. Under thoracoscopic guidance, a second 5-mm trocar was inserted near the anterior axillary line of the sixth intercostal space, and a third 5-mm trocar was placed in the sixth or seventh intercostal space near the sternum without injury of the internal mammary vessel. The procedure on the left side was performed in the same manner.
At the end of the surgery, fentanyl (25 mcg) was injected intravenously, and intravascular patient-controlled analgesia was connected for postoperative pain control. Additionally, neuromuscular relaxation was reversed with sugammadex (2 mg/kg). After a TOF ratio > 0.9 was achieved, the tracheal tube was removed, and all patients were transferred to the intensive care unit (ICU).
The Statistical Package for the Social Sciences program was used for the statistical analysis. Variables with a normal distribution are indicated by the mean value (standard deviation), and variables with a non-normal distribution are indicated by the median (25–75% interquartile ranges). The Student’ s unpaired t-test and Mann-Whitney U test were used for the continuous variables, and the chi-squared test was used for the categorical variables. A P value < 0.05 was considered statistically significant.