Difficult tracheal intubation in randomized controlled studies: ethical considerations

Abstract

To the Editor, We read with great interest the article by Thiboutot et al. published recently in the Journal. The authors evaluated the effects of manual in-line stabilization (MILS) of the cervical spine on the rate of difficult orotracheal intubation without cervical trauma in adult patients under general anesthesia. The study hypothesis was that the rate of failed tracheal intubation would be significantly greater with MILS than without. Although the results are convincing and the methodology seems correct, we believe this study raises an important ethical problem. While MILS is a maneuver frequently used while securing the airway of patients with a known or a potentially unstable cervical spine, its effect is known to impair visualization of the larynx with a reduction in the incidence of Cormack and Lehane’s grade 1 laryngeal visualization and an increased incidence of grades 2, 3, and 4. In Thiboutot et al.’s study, 50% of patients in the MILS group had an unsuccessful intubation and a significantly longer time for successful tracheal intubation than the control group. Manual in-line stabilization was also associated with a negative impact on glottic exposure during laryngoscopy. In our opinion, the patients included in the MILS group had an exposure to an unacceptable iatrogenic morbidity because the predictable risk they might have incurred was not in proportion with the expected benefit. More frequent tracheal intubation attempts increase intubation difficulty, and it is known that difficult intubation is associated with a higher rate of complications. Unfortunately, the incidence of side effects was not reported in this study. In our view, the prerequisites for ethical approval to conduct a randomized controlled trial should include confirmation that the intervention will not expose the test group to potential complications without complete disclosure to the patient of the associated risks and benefits.