Effect of intravenous fentanyl on cough reflex and quality of endotracheal intubation in cats

To assess the effects of intravenous (IV) fentanyl on cough reflex and quality of endotracheal intubation (ETI) in cats. Randomized, blinded, negative controlled clinical trial. A total of 30 client-owned cats undergoing general anaesthesia for diagnostic or surgical procedures. Cats were sedated with dexmedetomidine (2 μg kg–1 IV), and 5 minutes later either fentanyl (3 μg kg–1, group F) or saline (group C) was administered IV. After alfaxalone (1.5 mg kg–1 IV) administration and 2% lidocaine application to the larynx, ETI was attempted. If unsuccessful, alfaxalone (1 mg kg–1 IV) was administered and ETI re-attempted. This process was repeated until successful ETI. Sedation scores, total number of ETI attempts, cough reflex, laryngeal response and quality of ETI were scored. Postinduction apnoea was recorded. Heart rate (HR) was continuously recorded and oscillometric arterial blood pressure (ABP) was measured every minute. Changes (Δ) in HR and ABP between pre-intubation and intubation were calculated. Groups were compared using univariate analysis. Statistical significance was set as p < 0.05. The median and 95% confidence interval of alfaxalone dose was 1.5 (1.5–1.5) and 2.5 (1.5–2.5) mg kg–1 in groups F and C, respectively (p = 0.001). The cough reflex was 2.10 (1.10–4.41) times more likely to occur in group C. The overall quality of ETI was superior in group F (p = 0.001), with lower laryngeal response to ETI (p < 0.0001) and ETI attempts (p = 0.045). No differences in HR, ABP and postinduction apnoea were found. In cats sedated with dexmedetomidine, fentanyl could be considered to reduce the alfaxalone induction dose, cough reflex and laryngeal response to ETI and to improve the overall quality of ETI.