Optimal dose of pretreated-dexmedetomidine in fentanyl-induced cough suppression: a prospective randomized controlled trial

Background: To investigate the optimal dose of pretreated-dexmedetomidine in fentanyl-induced cough suppression. Methods: Patients of 180 undergoing elective surgery with general anesthesia, aged 18-65 years, BMI 18.5-30 kg/m2, ASA I or II, were equally randomized into four groups (n = 45) to receive pumped pretreatment of dexmedetomidine with 0 (group 1), 0.03 (group 2), 0.06 (group 3) and 0.09 (group 4) μg•kg-1•min-1 for 10 min, respectively. After the pretreatment, all patients were given a 5-sec intravenous injection of fentanyl 4 µg/kg. The symptoms of irritating cough including the severity and onset time were recorded for one min after fentanyl injection. General anesthesia induction was completed with midazolam, propofol and cisatracurium, then endotracheal tube or laryngeal mask was inserted and connected to an anesthesia machine. MAP, HR and SpO2 at the beginning of pretreatment (T0), 3 min (T1), 6 min (T2), 9 min (T3) and 12 min (T4) after the beginning of pretreatment were recorded. Side effects of dexmedetomidine, such as bradycardia, hypertension, hypotension, and respiratory depression were also recorded during the course. Results: Totally 168 patients completed the study. The incidences of cough were 52.4%, 42.9%, 11.9%, and 14.3% in groups 1, 2, 3, and 4, respectively, with no significant differences between groups 1 and 2 ( P > 0.05) and between groups 3 and 4 ( P > 0.05). The incidence and severity of cough in groups 3 and 4 were significantly lower than those in groups 1 and 2 ( P < 0.05). Compared to T0, HR at T2 ( P < 0.05), T3 ( P < 0.01), and T4 ( P < 0.01) decreased significantly and MAP at T4 decreased significantly ( P < 0.05) in group 4. Bradycardia occurred in 1 case and respiratory depression occurred in 1 case in group 4. Compared to group 1, the time points of cough in the other 3 groups were delayed significantly ( P < 0.05).  Conclusion: Pretreated dexmedetomidine 0.06 μg•kg-1•min-1 pumped intravenously for 10 min could reduce FIC effectively without side effects. Trial registration: This study was registered with ClinicalTrials.gov (NCT03126422) in April 13, 2017. Keywords: Dexmedetomidine; Fentanyl; Cough.