Continuous Infusion Of Propofol Combined With Midazolam For Patients Undergoing Long-Time Microsurgeries

Objective:extremity microsurgeries were usually operated under nerve blocking anesthesia,howerer patients could felt dysphoric and afeard due to long-time caging,reaction to tourniquet,or the experences of multiple operations during the long-time subtile and complicated operation for example finger reconstruction,toenail flap transplanting,articulus transplanting and so on.Not only the patients were hured physically and mentally,but also the operations can't be proceeded swimmingly,even the postoperative recoveries were effected.So it's an important clinical topic to perform sedation for these patients.The purpose of this study is to investigate the sedative effect of propofol combined with different doses of midazolam in patients undergoing long-time microsurgery,taking auditory evoked potential index(AAI)as a parameter,and to provide clinical bases of sedation for patients undergoing these operations.Methods:Forty(American Society of Anesthesiologists)ASAⅠ～Ⅱpatients undergoing microsurgeries with brachial plexus block and combined spinal epidural anesthesia(CSEA)were randomly divided into 4 groups.The process of the operations were anticipated beyond 6 h.These should be excluded:hearing disturbance,history of mental disease and nervous disease,being hyperergic to benzodiazepine(BZ),drug addiction to opioid(including alcohol),myasthenia gravis. MAP(Mean Arterial Pressure),ECG(Electrocardiogram),SpO₂(Pulse Oxygen Saturation)were continuously monitored during anesthesia.AAI(Auditory Evoked Potential Index)were monitored by A-line monitor made by Co.Danmeter in denmark.The CSEA were enforced on L_2～3,0.5%bupivacaine 15 mg was infused into SAS(subarachnoid space).Epidural catheter was inserted by 3cm in cavitas epiduralis. The anaesthesia was maintained by adding 0.75%bupivacaine in cavitas epiduralis. The brachial plexus block was enforced in the intergroove between anterior and medial scalenus muscle by 0.894%ropivacaine 20ml.The operation started when the anaesthetic effect was certain and consummate,and the patients' vital sign were stable. Then the sedation program were executed.Normal saline(NS)2ml for groupâ… , midazolam 0.01mg/kg,0.02mg/kg,0.04mg/kg for Groupâ…¡,â…¢,â…£respectively.1 min after given NS or midazolam,propofol was infused at a rate of 5～10mg/kg·h combined with midazolam at a rate of 0.01mg/kg·h,0.02mg/kg·h,0.04mg/kg·h for Groupâ…¡,â…¢,â…£respectively.After the AAI decreased to 40,the infusion rate of propofol was adjusted to keep AAI at the level of 30～45,and maintained the level by infusing propofol and midazolam for 5 h.The dosages of propofol required for induction and maintenance was recorded. The emergence time and whether patients had awareness during the operation were recorded after the infusion stopped.The AAI,MAP,HR and S_pO₂ were recorded when 1 min after sedation administration,AAI decreasing to 40,the end of the 1st,3rd,5th hour after AAI decreasing to 40.Results:1.Demographic profileThe patients of the four groups were comparable in age,weight,time of operation,there were no differences among them.(P＞0.05).2.The correlation between AAI and Observer's Assessment of alertness/sedation (OAA/S)The OAA/S score was 0～1,when AAI was 30～45.3.MAP,HR and S_pO₂3.1 Change on MAPWithin the groups,MAP decreased after sedation,compared with 1min after administration(P＜0.05).There were no significant differerces at the end of the 1st, 3rd,5th hour after AAI decreasing to 40(P＞0.05).There were no significant differences among the four groups at the corresponding points(P＞0.05).3.2 Change on HRWithin the groups,HR was significantly slower after sedation,compared with 1 min after adminstration(P＜0.05).There were no significant differerces at the end of the 1st,3rd,5th hour after AAI decreasing to 40(P＞0.05).There were no significant differences among the four groups at the corresponding points(P＞0.05).3.3 Change on S_pO₂The S_pO₂ of all the patients were over 99%,and there were no significant differences among the four groups at the corresponding points(P＞0.05).4.Dosage of Propofol,Induction time,Emergence time4.1 sedation inductionInduction time t₁ was obviously shortened in GroupⅡ～Ⅳcompared with Groupâ… (P＜0.01).There were no significant differences amongⅢ～Ⅳ(P＞0.05). Dosage of Propofol was reduced in GroupⅡ～Ⅳcompared with Groupâ… (P＜0.01). There was no significant differences between groupâ…¡andâ…¢,and between groupâ…¢andâ…£.4.2 sedative maintenanceThe dosage of Propofol in both Groupâ… andâ…¡were larger than that in Groupâ…¢andâ…£(P＜0.05).There were no significant differerces between groupâ…¢andâ…£(P＞0.05).4.3 Emergence timeThe emergence time in Groupâ…£was dramatically longer than the other groups(P＜0.01).There were no significant differerces between groupâ…¡andâ…¢(P＞0.05)5.awareness during the operation2 patients in groupâ… could recall a fraction of event during the operation,and the other patients had no remembrance of the operation. Conclusion:1.All the patients could reached a satisfactory sedation by propofol alone or combined with midazolam during long-time microsurgeries.2.The sedation induction period was shortened by combined with midazolam. The dosage of propofol reduced in the period of sedation induction and sedative maintenance.However there were no dependence of dosage between propofol and midazolam.3.At the target sedative level of AAI30～45,the optimal dosage of midazloam for induction of sedation was 0.02mg/kg,and for maintenance of sedation was 0.02 mg/kg·h while combined with Propofol continuous infusion.That could avoid the remembrance during the operation,and the emergence time could not be prolonged.