Objective To determine the median effective dose (ED50) of prophylactic intravenous lidocaine for the prevention of propofol medium-chain triglyceride/long-chain triglyceride (MCT/LCT) emulsion injection pain. Design Prospective trial, Dixon up-and-down sequential method. Setting Operating room of a single hospital. Patients Thirty patients aged 18–65 years with American Society of Anesthesiologists (ASA) status I or II who were scheduled for elective surgery under general anesthesia (GA) were included. Interventions The initial dose of prophylactic lidocaine before propofol MCT/LCT emulsion injection was set at 0.5 mg/kg lean body weight (LBW). The lidocaine dose was adjusted according to the degree of patients’ injection pain using the Dixon up-and-down sequential method. Measurements The ED50 and 95% confidence intervals (CIs) of lidocaine were calculated using the Dixon–Massey formula. Vital signs and adverse effects were recorded. In the postanesthesia care unit (PACU), patients were asked if they recalled feeling any injection pain with visual analog scale (VAS) evaluation. Results The ED50 of lidocaine for the prevention of propofol MCT/LCT emulsion injection pain was 0.306 mg/kg LBW (95% CI, 0.262–0.357 mg/kg LBW). No adverse reactions to lidocaine occurred. In the PACU, 90.9% of patients who experienced injection pain recalled this pain (VAS score, 2.8±1.8). Conclusions Prophylactic intravenous lidocaine (0.306 mg/kg LBW) effectively prevented propofol MCT/LCT emulsion injection pain in 50% of patients scheduled for elective surgery under GA with no adverse reaction occurring.

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.

Background To investigate the optimal dose of pretreated-dexmedetomidine in fentanyl-induced cough (FIC) suppression. Methods Patients of 180 undergoing elective surgery with general anesthesia, aged 18–65 years, BMI 18.5–30 kg/m 2 , ASA I or II, were equally randomized into four groups ( n = 45) to receive intravenous pretreatment of dexmedetomidine with 0 (group 1), 0.3 (group 2), 0.6 (group 3) and 0.9 (group 4) mcg/kg over 10 mins, respectively. After the pretreatment, all patients were given a 5-s intravenous injection of fentanyl 4 mcg/kg. The symptoms of irritating cough including the severity and onset time were recorded for 1 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 SpO 2 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 onset time of cough in the other 3 groups were delayed significantly ( P < 0.05). Conclusion Pretreated dexmedetomidine 0.6 mcg/kg blous intravenous infusion over 10 mins could reduce FIC effectively without side effects. Trial registration This study was registered in ClinicalTrials.gov (NCT03126422), April 13, 2017.

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