[Conventional intubation and laryngeal tube in cervical spine instability : Changes in the width of the dural sac in unfixed human body donors]

Background: Airway management in patients with an unstable cervical spine requires a cautious approach if secondary damage is to be prevented but the question regarding the optimum method remains unresolved. The primary aim of the study was to investigate whether there were differences between intubation by conventional Macintosh laryngoscopy and placement of a laryngeal tube (LTS-D) with respect to dural sac compression on an unfixed human cadaver model with unstable injuries of the upper cervical spine. Secondary parameters that could be relevant in patients with unstable spinal injuries were also investigated.

Material and methods: Orotracheal intubation by conventional direct laryngoscopy using a Macintosh blade and placement of a laryngeal tube (LTS-D) were performed in six fresh human cadavers. The dural sac was filled with contrast dye to allow continuous myelography by lateral fluoroscopy. Changes in the width of the dural sac at the cervical segments (C) C0/C1 and the C1/C2 levels as well as secondary parameters (angulation, distraction, intervention time) were assessed in the intact spine as well as in the presence of combined atlanto-occipital dislocation and atlanto-axial instability. The intubation methods were considered independent and examined using the Mann-Whitney U‑test.

Results: At the C0/C1 level in the intact spine, conventional laryngoscopy caused less reduction of the width of the dural sac than placement of the LTS-D (0.33 mm vs. 0.46 mm, p = 0.035); however, in the presence of combined atlanto-occipital dislocation and atlanto-axial instability, placement of the LTS-D caused less reduction in the width of the dural sac than conventional intubation (1.18 mm vs. 0.68 mm, p = 0.005). At the C1/C2 level no differences were found with respect to changes in the width of the dural sac, neither in the intact spine nor in combined atlanto-occipital dislocation and atlanto-axial instability. Conventional intubation caused more angulation than placement of the LTS-D at both levels measured. Both methods did not cause distraction. The intervention times for placement of the laryngeal tube were shorter.

Conclusion: In an unfixed human cadaver model with combined atlanto-occipital dislocation and atlanto-axial instability, placement of the LTS-D caused less reduction in the width of the dural sac than conventional intubation at the level of the craniocervical junction. The LTS-D also caused less angulation and could be placed faster. It could therefore also be advantageous over conventional intubation in living patients with an unstable cervical spine.