Comparison of blind and endoscopic-guided orotracheal intubation on laryngeal and tracheal damage in domestic rabbits (Oryctolagus cuniculus)

Abstract

Objective: To compare blind and endoscopic-guided techniques for orotracheal intubation in rabbits and the number of intubation attempts with laryngeal/tracheal damage.

Study design: Prospective, randomized experimental study.

Animals: A total of 24 healthy, intact female New Zealand White rabbits, weighing 2.2 ± 0.2 kg (mean ± standard deviation).

Methods: Rabbits were randomly assigned to blind (group B) or endoscopic-guided (group E) orotracheal intubation with a 2.0 mm internal diameter uncuffed tube. Intramuscular (IM) alfaxalone (7 mg kg^-1), hydromorphone (0.1 mg kg^-1) and dexmedetomidine (0.005 mg kg^-1) were administered, and additional IM alfaxalone (3-5 mg kg^-1) and dexmedetomidine (0.025 mg kg^-1) were administered to rabbits with strong jaw tone. An intubation attempt was defined as the advancement of the endotracheal tube from the incisors to the laryngeal entrance. Tracheal intubation was confirmed via capnography and anesthesia was maintained with isoflurane for 2 hours. Following euthanasia, laryngeal and tracheal tissues were submitted for histopathology. Quality of anesthesia for orotracheal intubation, intubation procedure and tissue damage were numerically scored. Data were analyzed using Poisson regression, Spearman's correlation, t test, mixed anova, Mann-Whitney U test, Friedman and Chi square tests as appropriate.

Results: Median (range) intubation attempts were 2 (1-8) and 1 (1-3) for groups B and E, respectively. More rabbits in group E (91.6%) required additional alfaxalone and dexmedetomidine than in group B (16.7%). Median (range) cumulative histopathology scores were 6 (3-10) and 6 (2-9) for groups B and E, respectively. Scores were highest in the cranial trachea, but there was no difference between groups and no correlation between laryngeal/tracheal damage and the number of intubation attempts.

Conclusions and clinical relevance: Both orotracheal intubation techniques were associated with laryngeal/tracheal damage. Although blind orotracheal intubation was associated with a higher number of attempts, the tissue damage was similar between groups.

Keywords: alfaxalone; blind orotracheal intubation; endoscopic-guided intubation; rabbit; respiratory tract tissue damage.