The Influence Of Dexmedetomidine Administered At Different Time On Postoperative Pain After Laparoscopic Surgery

Objective:This study was to observe the influence of dexmedetomidine (DEX) administered at different time on postoperative pain, together with palinesthesia, so as to find the best time to administer this drug.Methods:Ninety patients ASA physical status Ⅰ and Ⅱ patients undergoing laparoscopic ovarian cyst/tumor decollement were randomly divided into three groups:group A (DEX would be administered15minutes ahead of induction, perfusing in15minutes with the concentration of4μg/ml in the dose of1μg/kg), group B (DEX would be administered at the end of the surgery, perfusing in15minutes with the concentration of4μg/ml in the dose of1μg/kg) and group C (normal saline instead of DEX). All the patients received routine anesthesia induction:midazolam0.05mg/kg, propofol1～2.5mg/kg, until the patient’s eyelid reflex was lost, then remifentanil1μg/kg perfusion for1minute,cis-atracurium0.2mg/kg. Endotracheal intubation was administered by the same anesthesiologist until the BIS value got to50and the neuromuscular relaxation was achieved. Anesthesia and analgesia were maintained by the continuous infusion of propofol (concentration of1%and rate of4～12mg/kg/h) and remifentanil (concentration of25μg/ml and the rate of0.2μg/kg/min). Atracurium was administered intermittently in the dose of0.2mg/kg every30minutes for muscular relaxation and the last time to administer it should be30minutes before the surgery finished. At the time of the cysts/tumor was striped,1μg/kg fentanyl and5mg tropisetron would be intravenoused. Controlled mechanical ventilation was adjusted to maintain the PETCO2between35and45mmHg, and BIS index was monitored between40and60. All the patients would be sent to the PACU after operation. If the patient felt pain and the Visual Analogue Scale (VAS) degree got to or was greater than4score,1mg/kg tramadol should be intravenoused intermittently until the VAS degree got to or was lower than4score.During the perioperative period, the mean arterial pressure (MAP), heart rates (HR), pulse oxygen saturation (SpO2) and bispectral (BIS) index were monitored continuously and recorded at nine time points:To (baseline), T1(after DEX or NS administered and before the induction), T2(the time after intubation), T3(the time of intubation), T4(the time of skin incision), T5(1min after the pneumoperitoneum be administered), T6(the end of the pneumoperitoneum), T7(the end of the surgery),T8(the time of extubation). The time of recovery, extubation and back to the ward were all recorded. We evaluated the sedation degree five minutes after extubation with the Ramsay Score, and the pain degree with VAS Score at eight time points:5minutes,0.5hour,1hour,2hours,4hours,6 hours,12hours and24hours after the extubation. Recorded3groups the duration of the operation, consumption of propofol intraoperatively, case number needing tramadol and the consumption of tramadol postoperatively. Recorded adverse events in24hours.Results:1. General information:No significant differences were found in age, weight, ASA status, operative time or the average amount of propofol intraoperatively among three groups (p>0.05).2. Hemodynamic changes:No significant differences were found in the variability of MAP or HR among three groups(p>0.05). And the variation in group A was more stable than both group B and C. There was no significant difference in SPO2either (p>0.05). There was no significant difference in BIS value (p>0.05) but at time T1(p<0.05). At T1,the BIS value of group A was lower than group B and C.3. Consumption of propofol:no significant difference (p>0.05) was found in consumption of propofol intraoperatively among three groups.4. Evaluation of pain:significant difference in the VAS score was found among the three groups during the12hours after extubation (p<0.05), but not after24hours(p>0.05). There was no significant difference in the VAS score between group A and B during the24hours after extubation (p>0.05).The VAS scores of goup A and B were both lower than group C. There was no significant difference in the number of case needing tramadol nor in tramadol consumption for group C comparing with group A or group B during the24hours after extubation (p<0.01). But there was no significant difference between group A and group B (p>0.05).5. Evaluation of palinesthesia:There were no significant differences in the time of palinesthesia, extubation, back to Patients’Room or Ramsay Score among three groups (p>0.05).6. Adverse events:There were no significant difference in adverse events during24hours after operation among three groups (p>0.05).Conclusion:1. It can relieve postoperative pain for DEX administered either15minutes before induction or15minutes before the end of the surgery. And the effect is similar.2. DEX application15minutes either before the induction or before the end of the surgery will not prolong the patients’ recovery, extubation and returning to the ward. Ramsay scores were not affected either, without increasing the side effect.3. DEX application15minutes before induction can maintain the stability of the hemodynamic changes better.