Clinical Study Of Dexmedetomidine’s Sedative Effects And Its Impacts On Respiratory & Cardiovascular Systems During Spinal Anesthesia & General Anesthesia Induction

Part I Comparison of the sedative effects of dexmedetomidine & midazolam during spinal anesthesia, and their impacts on respiratory & cardiovascular systemsObjective:We studied the sedative effect of a single loading dose (1μg-kg-1) of dexmedetomidine in the procedure of employing subarachnoid block in spinal anesthesia to accomplish analgesia and compared it with that of midazolam in the dosage recommended by clinical trials. We evaluated the sedative effects of these two medications by analyzing the collected BIS data and observed their impacts on respiratory & cardiovascular systems.Methods:Forty patients in ASA gradeⅠ～Ⅱ, age 20～60 and BMI 19～26 kg/m2, scheduled to undergo lower extremity surgery with subarachnoid block in spinal anesthesia. They were randomly assigned to one of two groups (n=20 each group). Level of anesthesia was controlled beneath Tio. Group D patients received intravenous infusion of 1μg-kg"1 of dexmedetomidine within a 10-minute period. Group M patients were administrated 50μg-kg-1 of midazolam during 10 minutes as well. We collected BIS, OAA/S, SBP, DBP, HR and SPO2 figures of both groups at pre-anesthesia time (TO), when level of anesthesia stabilized (T1),1 minute (T2),5 minutes (T3),10 minutes (T4),20 minutes (T5) and 30 minutes (T6) subsequent to dosing, respectively.Results:At T4,T5 and T6:BIS of group D patients were significantly lower than those of group M (77.90±2.90 vs 83.20±3.32,71.30±3.39 vs 82.25±3.64,83.75±2.27 vs 86.70±2.52, p<0.05); OAA/S of group D patients were much higher than group M patients (3.05±0.22 vs 2.45±0.76,2.70±0.57 vs 2.60±0.75,3.75±0.55 vs 3.15±0.75, p<0.05). At the corresponding instances (T4, T5 and T6):SBP of group D patients were lower than group M patients (105.25±9.34mmHg vs 114.05±10.22mmHg,107.10±8.37mmHg vs 115.85±9.77mmHg, 11.65±9.18mmHg vs 118.45±10.12mmHg, p<0.05); DBP of group D patients were lower than group M patients were (66.10±6.91mmHg vs 74.05±7.92mmHg,68.75±6.81mmHg vs 74.60±6.94mmHg,71.60±6.86mmHg vs 76.45±6.97mmHg, p<0.05); HR of group D patients were lower than group M patients (60.45±2.34b·min-1 vs 71.30±4.78b-min-1, 61.40±2.68b·min-1 vs 72.10±4.49b·min-1,64.35±2.89b·min-1 vs 74.05±5.09b·min-1, p<0.05). Compared with same group at T1, SBP, DBP, and HR of group D patients went down considerably (p<0.05) at T4, T5 and T6. There were 4 and 13 patients got SPO2<95% in group D and M, respectively. We can see that incidence of minor respiratory depression of group M patients was noticeably higher than that of group D patients (p<0.05).Conclusions:As an adjuvant medication in the procedure of employing subarachnoid block in spinal anesthesia, the sedative effect of 1μg-kg-1 of dexmedetomidine is stronger than that of 50μg·kg-1 of midazolam,the dosage recommended by clinical trials. Compared with midazolam, patients receiving dexmedetomidine stand a better chance to wake up and have lower incidence of respiratory depression. Although the decreases of blood pressure and heart beat rate are substantial, they are yet in the controllable range. Part II The sedative effects of dexmedetomidine during general anesthesia induction & tracheal intubation, and its impacts on cardiovascular systemsObjective:Study the sedative effects of dexmedetomidine in the dose of lμg-kg-1 before general anesthesia induction and haemodynamics during tracheal intubation.Methods:Forty patients in ASA gradeⅠ～Ⅱ, age 20～60, BMI 19～26 kg/m2, scheduled to undergo laparoscopic surgery with general anesthesia. They were randomly assigned to two groups (n=20 each group) as well. Group D patients received intravenous infusion of dexmedetomidine lμg-kg-1 within a period of 10 minutes. Then intravenous infusion of fentanyl 2μg·kg-1. Group F patients, we administrated the same amount of 0.9%Nacl within same time instead of dexmedetomidine before intravenous infusion of fentanyl 4μg·kg-1. Next in two groups we setting plasma concentration as the target and 4μg·ml-1 as the targeting concentration (Cp), we conducted target controlled infusion (TCI) of propofol. We injected 0.6mg·kg-1 of rocuronium when patients’BIS reached 50. In 90 seconds, tracheal intubation was applied. We were monitoring BIS and continued injecting propofol till the targeting plasma concentration was reached. We collected the statistics of BIS, SBP, DBP, HR and at pre-anesthesia time (TO),5 minutes post dosing (T1),10 minutes post dosing (T2), subsequent to induction (T3), at tracheal intubation (T4),1 minute (T5) and 3 minutes (T6) following tracheal intubation, respectively.We logged the time, the amount of propofol required for patients and The propofol effect-site concentration(Ce), when BIS reached 50.Results:At T1, T2, T3, T4, T5 and T6, BIS of group D were significantly lower than group F patients (89.05±5.46 vs 96.15±0.75,79.10±4.73 vs 96.25±0.79,46.00±3.83 vs 51.70±2.36,6.95±4.95 vs 52.80±2.57,1.60±5.56 vs 50.95±1.88 and 38.50±4.65 vs 48.85±2.16, p<0.05), At the instances of T4, T5 and T6, SBP of group D were noticeably lower than those of group F (116.05±12.57mmHg vs 134.05±9.34mmHg,114.10±9.16mmHg vs 129.70±12.28mmHg,109.05±8.80mmHg vs 122.70±11.46mmHg, p<0.05), respectively; DBP of group D were noticeably lower than group F patients (71.00±9.80mmHg vs 84.55±7.85mmHg, 72.05±8.47mmHg vs 82.05±7.57mmHg,68.15±8.50mmHg vs 76.80±6.51mmHg, p<0.05), HR of group D significantly lower than group F(73.60±16.51b-min-1vs 93.90±5.10b-min-1, 68.95±10.48b-min-1 vs 88.95±5.46b-min-1,66.7±9.10b-min-1 vs 80.00±3.52b-min-1, p<0.05). Comparing with same group at T3, figures were considerably higher at T4,T5 and T6 for both groups of patients (p<0.05). For patients to reach BIS of 50, it took (103.55±12.81s vs 145.15±24.93s, p<0.01) for group D and F, it took (8.05±0.76ml vs 10.06±1.51ml, p<0.05) of propofol for group D and F, The effect-site concentration of propofol (Ce) for group D and F (3.04±0.25μg·ml-1 vs 3.32±0.29μg·ml-1, p<0.05), respectively; group D were significantly lower than group F.Conclusions:Applied prior to general anesthesia induction, 1μg·kg-1 of dexmedetomidine has enhanced sedative effect during general anesthesia. Dexmedetomidine effectively suppresses adverse cardiovascular reactions and mitigates haemodynamics during tracheal intubation in general anesthesia induction. It also shortens the time to achieve general anesthesia induction, decreases the amount of fentanyl and propofol in general anesthesia, and works with propofol complementarily.