Dexmedetomidine Mixed In A Low Concentration Of Ropivacaine In Tranversus Abdominis Plane Block

Objective:Transversus abdominis plane (TAP) block when used for post-operative pain control in patients with low abdomen surgery, such as laparoscopic colorectal surgery, will need bilateral block and the total local anesthetic volume may need up to40-60ml. Thus there is a risk of local anesthetic toxicity.Dexmedetomidine is an alfa-2-receptor agonist which might be used as an additive to local anesthetics for various regional anesthetic techniques. The hypothesis was that dexmedetomidine as an adjuvant mixed in a low concentration of ropivacaine in ultrasound-guided transversus abdominis plane block could maintain the effect and reduce the risk of ropivacaine toxicity.Methods:Sixty (60) patients underwent laparoscopic colorectal surgery were enrolled in this prospective, randomized, double-blind controlled clinical study. The inclusion criteria were ASA I-III, either gender, age18-80, weigh45-90kg. Patients were randomly allocated to three groups and accepted bilateral transversus abdominis plane block under ultrasonography guidance after surgery with60ml of different local anesthetic compounds:0.19%ropivacaine and saline (19R group, n=20),0.19%ropivacaine plus50mcg dexmedetomidine (19RD group, n=20), or0.25%ropivacaine with saline (25RD group, n=20). Patient controlled intravenous analgesia (PCIA) sufentanil was provided to all the patients.The pain score of visual analogue scale (VAS) at rest and at cough, and Ramsay sedation score were evaluated at2,4,8,12and24h after operation. The time to the first request of PCIA after surgery, the total consumption of sufentanil with in24h after operation, the number of successfully PCIA delivered doses and the number of PCIA demand within24h after operation were recorded. The patient satisfaction and the adverse reactions were also recorded.Results:Comparing to that of group19R, the visual analogue scores for pain at rest in group19RD and group25R were significantly lower at2, A,8,12h after surgery (p<0.05). And during coughing, the visual analogue scores were significantly lower at2,4and8h in groupl9RD and group25R after surgery (p<0.05) but not different at12or24h.The time to the first request of PCIA after surgery was significantly sooner in the19R group comparing to that in the19RD group or the25R group (p<0.05). The consumption of sufentanil with in24h after operation, PCIA deliver and demand were all significantly higher in the19R group. But comparing between group19RD and25R, there were no significant difference. The incidence of postoperative nausea and vomiting was not significantly different among the groups. There were no complications associated to transversus abdominis plane block in all groups. The patient satisfaction scores were significantly lower in group19R (p<0.05).Conclusion:We found that50mcg dexmedetomidine as an adjuvant mixed in low concentration (0.19%) of ropivacaine in ultrasound-guided transversus abdominis plane block provided as effective block as0.25%ropivacaine did, and might improve the safety by reducing ropivacaine dose in post-operative analgesia for laparoscopic colorectal surgery patients.