Approval for the study was granted by Shanghai Renji Hospital Ethics Committee(Ethical number: 2016). Written informed consents were obtained from patients undergoing elective intra-thoracic surgeries required double-lumen intubation. The present trial was registered at http://www.chictr.org.cn (the registration number is ChiCTR1900025718, principal investigator: Z.L.H., date of registration: Septembere 06, 2019).
Including criteria were adult patient between 18–75 years old, ASA I–II, BMI < 35 kg/m2, with Mallampati score of 1 or 2. All the Mallampati scores were assessed by the same observer. Exclusion criteria included presence of any predictors of difficult intubation, including Mallampati score > = 3, decreased inter-incisor distance (< 3 cm), short thyromental distance (< 6 cm), and reduced neck extension(< 80°from neck flexion), cervical spine instability, having a history of difficult endotracheal intubation or difficult mask ventilation, severe pulmonary ventilation dysfunction or risk of pulmonary aspiration. 90 patients were randomly allocated to GlideScope, C-MAC(D) or Macintosh group. This was done by a closed envelope technique using a computer generated block randomization method in blocks of 15. Before study, the computer randomization was performed and the allocation result was put in individual numbered and sealed envelopes. The researcher responsible for recruitment was unknown of the allocation result. After the patient was consented for the study, the allocation was revealed. All endotracheal intubations were performed by five anesthesiologists with ten years working experience skilled in videolaryngoscope.
Leftside or rightside 32Fr/35Fr Mallinckrodt™ DLT (Mallinckrodt Medical, Athlone, Ireland) was selected for female patients and 35Fr/37Fr DLT for male patients depended on whether their height was below or above 155 cm for female and 165 cm for male respectively. If operation side was the left, right-side DLT was used, otherwise left-side DLT was selected. In order to facilitate intubation, the distal 10–12 cm concavity of the DLT (with the stylet in situ) was moulded along the blade convexity in each group. The tracheal and the bronchial cuffs of the DLT were lubricated with surgilube sterile.
No premedication was given before induction. Standard monitor including Electrocardiogram (ECG), invasive arterial blood pressure, pulse oximetry saturation (SpO2) and end-tidal carbon dioxide were established before induction of anesthesia. After pre-oxygenation with 100% oxygen, patients were induced with intravenous midazolam 0.05 mg.kg− 1, propofol1.5 mg.kg− 1, fentanyl 5 µg.kg− 1, rocuronium 0.6 mg.kg− 1 was given to facilitate tracheal intubation. Ninety seconds after rocuronium administration, intubation with the DLT was performed by the laryngoscope allocated. DLT was inserted with the distal concavity facing anteriorly until the bronchial lumen cuff passed the vocal cord. The stylet then removed, the rotation was performed while tube was advanced. The left DLT rotated 90° counterclockwise while the right DLT rotated 90°clockwise to facilitate the tip entered the left or right main bronchus. Hemodynamic changes were monitored during induction. If systolic blood pressure was below 80 mmHg, ephedrine 5 mg was administrated intravenously, atropine 0.5 mg was given when heart rate was below 50 beats per minute. After the tip of the DLT was located in the targeted bronchial, the tracheal cuff was inflated and ventilation of the lungs started. Fibreoptic bronchoscopic assessment of adequate bronchial cuff placement was followed by DLT placement.
The time of DLT insertion was recorded as the time when the laryngoscope passed between the patient’s lips until three complete cycles of end-tidal carbon dioxide was displayed on the monitor. Success at the first attempt at intubation was also recorded by the same observer. The difficulty of DLT insertion and delivery were assessed by the operator, using NRS ranging from 0 to 10. The NRS results were grouped into 0 = ‘none’, 1–3 = ‘mild’, 4–6 = ‘moderate’ and 7–10 =‘severe’. C/L degree was classified as four degrees (I/IIA/IIB/III), and assessed by the operator. If it was not class I, external laryngeal pressure were provided by an assistant. The time taken for fibreoptic bronchoscopy was defined as the time from endobronchial intubation until fibreoptic bronchoscopic confirmation of adequate placement; The operator examined for blood on blades’ surface after it was removed from mouth. Hemodynamic parameters (mean arterial blood pressure and heart rate) were recorded 10 minutes before and 1, 3 and 5 minutes after intubation. After the assessment by fibreoptic bronchoscopy, the oral cavity, pharynx, larynx and teeth were examined by an independent investigator, who was unaware of the type of laryngoscope used for signs of laceration or bleedings. One day after surgery an independent investigator interviewed patients to assess the presence of sore throat and the incidence of hoarseness of voice.
Based on previous studies [13, 14], we determined that the mean intubation time for the Glidescope was 45.6 s with a standard deviation of 10.7 s, the C-MAC(D) videolaryngoscope was 32.27 s with a standard deviation of 11.13 s . Factoring possible drop-outs, we recruited 30 patients in each group, with an alpha value of 0.05 and a beta value of 0.2.
Data are expressed as median (IQR[min-max]), mean ± sd, or absolute numbers, as required. Statistical analysis was performed using SPSS 13.0. The Kruskal-waillis test was used to analyse independent samples (the time for successful intubation, the times of intubation attempts and the success at the first attempt, C/L degree, NRS of DLT delivery and insertion). The Chi-square test and the Student-New Man-keuls test were used to analyse demographic data and the incidence of complications. For the analysis of hemodynamic response to intubation, a repeated-measures analysis of variance was used. Statistical significance was considered at P < 0.05.