Postoperative Analgesia Using A Bolus Technique For Continuous Adductor Canal Block After Total Knee Arthroplasty: A Randomized Controlled Trial

Objective:Comparing two different regimens which include continuous infusion and intermittent bolus administration of ultrasound-guided continuous adductor canal block for postoperative analgesia,quadriceps muscle strength and early ambulation,to search the suitable mode of administration and to provide an effective basis for clinical practice.Methods:Sixty-seven patients scheduled for unilateral total knee arthroplasty undergoing spinal anesthesia,13 males and 54 females,aged 18-85 years,BMI 18-30kg/m~2,ASA physical statusⅠ-Ⅲ,were randomly divided into the continuous infusion group A(n=34)and the intermittent bolus group B(n=33).After the operations,ultrasound-guided Continuous adductor canal block were administered and 20 ml of 0.2%ropivacaine was given as the loading dose.From then on,patients in both groups used electronic analgesic pumps containing 240 ml of 0.2%ropivacaine for postoperative analgesia.5 ml/h of 0.2%ropivacaine was continuously infused for 48 hours in the group A.5 ml of 0.2%ropivacaine was intermittently injected every 60 minutes in the group B.All infusion pumps were setted the bolus dose being 5 ml,with a lock time of 30 minutes.The visual analogue scale(VAS)pain score at rest and quadriceps muscle strength were recorded preoperatively(T0),and at4,6,8,12,24,48 h(T1~T6)after surgery.The first time for straight leg raising and VAS pain score during 45°flexion of knee and active range of knee flexion were also recorded at 24(T5),48 h(T6)postoperatively.The ambulation distance at 48(T6),72 h(T7)and concentration of substance P were recorded preoperatively(T0),6(T2),24 h(T5)after surgery.Besides,the 48 h consumption of dezoine,press times of analgesic pump,postoperative analgesia satisfaction and occurrences of adverse reactions were recorded in both groups.Results:The VAS pain score at rest T4,T5,T6 and on knee flexion 45°at T5,T6 of group B were significantly reduced than group A(P<0.05).The 48 h total dezoine consumption and effective press times of group B were significantly reduced than group A(P<0.05)and the concentration of substance P at 24 h was lower than group A.The active range of knee flexion at T5,T6 and the ambulation distance at T6,T7 of group B were significantly higher than group A(P<0.05).The incidence of nausea and vomiting at 48 h of group B was significantly lower than group A(P<0.05).There were no statistical difference in quadriceps muscle strength,first time for straight leg raising and postoperative analgesia satisfaction between group A and group B(P>0.05).Conclusion:Compared with the continuous infusion group,the intermittent boluses group for continuous adductor canal block after total knee arthroplasty can provide better analgesic effect,decrease the use of remedial analgesic drugs postoperatively and reduce incidence of related adverse reactions,without increasing effect on quadriceps muscle strength,promoting early ambulation.