The Application And Evaluation Of Using Low-dose Dexmedetomidine During Tracheal Extubation After General Anesthesia

Objective:To investigate the effectiveness of using low-dose dexmedetomidine in maintaining hemodynamic stability, sedation and analgesia during tracheal extubation in patients recovering from general anaesthesia. Methods:Sixty patients, aged 18-60 years, ASAⅠ～Ⅱ, scheduled for modified radical mastectomy or TAH (transabdominal hysterectomy) and needing tracheal extubation after general anesthesia, were divided randomly into two groups(n=30 each):the control group (NS group) and experimental group (dexmedetomidine group). A prospective, randomized, double-blind, placebo-control trial was used in this study. All patients were stopped eating 12h and drinking 4h before operation and did not taken any preoperative medication. All patients received a preoperative infusion of Ringer's lactate solution with the rate of 12～15ml·kg-1·h-1 and continuous monitoring the BP,HR, ECG, SpO2. The depth of anesthesia was indicated by the BIS monitor.Fentanyl 2ug·kg-1 and propofol 1～2mg·kg-1 was used for induction of anesthesia,and atracurium was used when BIS values droped to 45～55,endotracheal intubation was performed after 2～3min and then intermittent positive pressure ventilation mode was used.Remifentanil 0.1～0.2ug·kg-1·min-1,atracurium 4～8ug·kg-1·min-1 and 2～3% sevflurane were used to maintain anesthesia during the operations. Atracurium was stopped and sevoflurane and remifentanil were reduced 30min and 10min before the end of surgery, respectively. At lOmin before the end of surgery, we started to infuse dexmedetomidine 0.2ug/kg (experimental group) or the same volume of saline (control group) using microcomputer pump. At the end of surgery, sevoflurane and remifentanil were stopped immediately and neostigmine 1mg and atropine 0.5mg were injected intravenously. The extubation was performed when BIS values were over than 75, SPO2>95% when the patients breathing air. All monitoring indicators included:SBP, DBP, MAP, HR, OAA/S (Observe's assessment of alertness/sedation scale), VDS (Verbal descriptors scale),BIS value,extubation time, CETSev(sevoflurane concentration end-tidal) in the period of extubation and time-point of collected experimental data included:T0 (preanesthesia), T1(5min before injecting experemental drugs),T2(5min after injecting experemental drugs), T3(10min after injecting experemental drugs), T4(5min before extubation), T5(extubated instantly), T6(3min after extubation), T7(5min after extubation), T8(10min after extubation), T9(20min after extubation), T10(30min after extubation). Results:1. The demographic and perianesthesia data:the difference between two groups about age, weight, hemorrhagic volume, transfusion volume, urine volume, operation time and anesthesia time was not significant(p>0.05).2. Hemodynamic changes:1) SBP: there was no difference between the two groups at T0 and T1, the experimental group was higher than control group at T2, T3, T4, but there was no significance (p>0.05). The control group was significantly higher than experimental group at T5, T6, T7, T8, T9 (p<0.05). DBP:there was no significant difference between the two groups at T0, T1, T2, T3, T4(p>0.05).Control group was significantly higher than experimental group at T5, T6, T7, T8, T9 (p<0.05).2) Comparison within groups:Both SBP and DBP at T5 were significantly higher than any other time in two groups (p<0.05).3) HR:control group was significantly higher than experimental group (p=0.04).3. OAA/S sedation score and BIS values:control group was significantly higher than experimental group at T7, T8, T9, T10 of OAA/S and control group was significantly higher than experimental group at T6, T7, T8, T9 (p<0.05).4. VDS5 pain score:control group was significantly higher than experimental group at the T9(p<0.05). T9 and T10 was significantly higher than T6 in two groups (p<0.05). The patients who were injected tramadol in 30 min after extubation in control group were more than experiment group(p=0.03).5. Extubation:the time of the patients open the eyes, recover spontaneous breathing, raise the heads for over than 5 seconds, be extubated and recovery from anesthesia between the two groups were not significantly different.(p>0.05).6. CETSev:there was no significant difference between the two groups (p>0.05).7. The use of vasocative drugs during extubation:the patients of control group was more than experimental group to used urapidil (p<0.05). Conclusion:1.Application of 0.2ug·kg-1 dexmedetomidine can significantly reduce the increased of BP and HR for suction, incision pain and extubation stimulation of general anesthesia extubation period, so can be used to prevent stress hypertension in general anesthesia extubation period; 2. Application of 0.2ug·kg-1 dexmedetomidine can provide invariably analgesic and sedative in the early postoperation and would not prolong extubation time.