c-mac video laryngoscope and vs-cmac fiberoptic stylet for awake endoscopic intubation in predicted difficult airways

Conditions: Difficult Airway Intubation

Summary: an anticipated difficult tracheal intubation is recommended to be managed performing the so called "awake tracheal endoscopic intubation" (ati) with the maintenance of patient's spontaneous breathing after an adequate sedation and topical anesthesia of upper airways, providing supplemental oxygen. initially only flexible bronchoscope was considered the device of choice (the gold standard) for ati but in the last decade videolaryngoscopes with hyper-angulated blade have been demonstrated to be an efficacy technique. most recently, endoscopic rigid stylets such as bonfils (carl storz™) and sensacope (acoutronic™) have been proposed as alternative techniques for ati in the event of expected difficult tracheal intubation. however, to date, no comparison studies have been carried out between these two kind of devices, alternative to flexible fiberscope, for ati. this is a clinical prospective randomized-controlled trial of non inferiority. the aim of this study is to compare the intubation success rate between two different devices (c-mac video laryngoscope and vs-cmac fiberoptic stylet) in patients with severe predicted difficult airways scheduled for elective surgery. the primary endpoint is the comparison of success rate for the tracheal intubation, demonstrating the non inferiority of videostylet efficacy compared to the most consolidated technique based on videolaryngoscope.

this is a clinical prospective randomized-controlled trial of non inferiority, set in the operating theatre of a terziary university hospital in ancona (ospedali riuniti ancona). the aim of this study is to compare the intubation success rate, defined as correct positioning of the tracheal tube inside the trachea, between videostylet (vs-carl storz™) and videolaryngoscope with hyperangulated blade (c-mac - carl storz™) in patients with severe predicted difficult airways scheduled for elective surgery. all patients enrolled in the study, examined in the pre-operative visit, will be asked for informed consent and will undergo the same anesthetic protocol consisting in upper airways topicalization with lidocaine and in smooth/moderate sedation (targeted on ramsay sedation scale ≦ 3) by i.v. administration of midazolam 0,03 mg/kg and fentanyl 100 mcg. on arrival in the operating room, nasal oxygen (5 l/min) and routine monitoring of vital signs will be applied to all patients. heart rate and blood pressure will be recorded at the beginning of the procedure and every 3 minutes until the intubation will be performed, while arterial oxygen saturation is continuously recorded. patients enrolled will be randomly divided into 2 groups regarding to the device used for ati: 1. videolaryngoscope (c-mac) with hyperangulated blade (d-blade) 2. videostylet (vs) endotracheal tube will be 6,5-7,0 mm for female and 7,5-8,0 mm for male. the following parameters will be registered: * success rate of the procedure defined as correct positioning of the tracheal tube in the trachea confirmed both endoscopically and through the capnographic curve etco2 * average time of intubation procedure expressed in sec. * operator's assessment of the subjective difficulty / handling of the device by means of a special analogue numerical scale * assessment of the patient's tolerance to the procedure by means of a special analogue numerical scale checked after patient's awakening from anesthesia at the end of the intervention. * occurrence of any complications or adverse event during the procedure (desaturation episodes, hemodynamic changes, oral-pharynx and larynx traumatism) the primary endpoint is the comparison of success rate for the tracheal intubation in patients with anticipated difficult airways, demonstrating the non inferiority of videostylet efficacy compare to the most consolidated technique based on videolaryngoscope. the null hypothesis will be the following: the rate of awake tracheal intubation failure with the vs video stylet is \> 10% compared to video-laryngoscope. considering an unsuccessful intubation rate with the two devices at 10%, a sample of 34 patients (17 per group) is necessary to demonstrate with a power of 90% and alpha error of 0.05 that the rate of intubation failure using the videosylet (study method) does not exceed 10% of the rate of failed intubations through the use of the video laryngoscope (reference method). statistical analysis: normally distributed data will be expressed as mean ± standard deviation and 95% confidence interval, while data with non-normal distribution will be expressed as median and interquartile range. the differences between means will be studied by parametric tests (e.g. student's t) if the data are normally distributed and by nonparametric tests (e.g. wilcoxon) if the distribution is not normal. the kolmogorov-smirnov test will be used to evaluate the normality of continuous variables. the characteristics of the patients in the two groups will be compared using the fisher test or the chi-square test for the nominal variables and the student t test or the mann - whitney u test for the continuous variables. for each test p \< 0.05 will be considered significant. for the primary endpoint: the difference in awake tracheal intubation success rate in the two groups will be assessed using fisher's exact test. the non-inferiority of the use of the videostylet (vs) compared to the standard method (videolaryngoscope with d-blade blade) will be confirmed if the difference, for 95% confidence interval, is less than the margin of non- inferiority established "a priori" as 10% after analysis of the literature (alhomary et al. anaesthesia 2018; 73: 1151-61)9 and according to clinical judgment. for the secondary endpoints of the study a purely analytical-descriptive evaluation will be carried out.

Eligibility criteria:
inclusion criteria: * schedule for elective surgery * detection of one or more of the following anthropometric criteria predictive of difficult intubation at the preoperative visit: 1. limitation of cervical spine movements (traumatic or surgical arthrodesis) 2. mallampati score = 4 3. thyromental distance \< 6 cm 4. interincisor distance \< 3 cm 5. suspected difficult ventilation via face mask 6. previous history of difficult or failed intubation exclusion criteria: * age \<18 years * refusal of the patient * urgent-emergency surgery * patient's respiratory failure

Keywords: difficult airway difficult intubation awake endoscopic intubation rigid fiberoptic stylet