ABSTRACT
Objective To investigate the effect of dexmedetomidine on norepinephrine(NE)release in midbrain periaqueductal gray(PAG)in a rat model of incisional pain.Methods Twenty-four male Wistar rats in which microdialvsis catheter was successfully placed in the ventrolateral region of PAG without complications were randomly divided into 4 groups(n=6 each):group control(group C);group incisional pain(group IP);group dexmetomidine(group D)and group dexmedetomidine+yohimbine(group DY).Incisional pain was induced by an incision made into the plantar surface of left hindpaw in IP,D,DY groups.Dexmedetomidine 30 μg/kg and dexmedetomidine 30 μg/kg+yohimbine 0.5 mg/kg were given intraperitoneally at 15 min before plantar incision in group D and group DY respectively.Mechanical paw withdrawal threshold(MWT)to von Frey filament stimulation was measured at 30 min before(baseline)and 1,2,3,4 h after operation in C,IP,D groups,and at 30 min before(baseline),and 1 h after operation in group DY.Dialysate samples were collected at 30 min before(baseline)and at evcry 30 min after operation for 4 h via cerebral microdialysis catheter for determination of the NE concentration in C,IP,D groups,and at 30 min before(baseline),30,60 min after operation in group DY.Results Incisional pain significantly decreased MWT and increased the NE concentration in dialysate in group IP.Dexmedetomidine premedication significantly inhibited mechanical hyperalgesia and attenuated incisional pain-induced increase in the NE concentration in dialysate in group D.Yohimbine counteracted effects of dexmedetomidine.Conclusion Dexmedetomidine has analgesic effect though inhibition of NE release from PAG.
ABSTRACT
Objective To investigate the pharmacodynamics of different local anesthetics administered intrathecally for elderly patients undergoing transurethral resection of the prostate (TURP). Methods Ninety ASA Ⅰ - Ⅲ elderly patients, aged 69-82 yr, with body mass index less than 30 kg/m2 , undergoing TURP under combined spinal-epidural anesthesia, were randomly divided into 3 groups ( n = 30 each): levobupivacaine group (group L), ropivacaine group (group R) and bupivacaine group (group B). Group L, R and B received intrathecai (IT) 0.5 % levobupivacaine, 0.5 % ropivacaine and 0.5 % bupivacaine respectively. The initial dose was 7,10 and 6 mg in group L, R and B respectively. The ratio of two successive doses was 0.9. If the upper sensory block reached T10 within the 20 min after IT injection, the IT analgesia was considered to be effective. The median effective dose (EDs0) and 95 % confidence interval (95 % CI) were calculated by Dixon. Results The ED50 and 95% CI of levobupivacaine, ropivacaine and bupivacaine were 6.781 (95% CI 6.561-7.024) mg, 9.135 (95%CI8.670-9.616) mg and 5.170 (95% CI 5.012-5.333) ng respectively. The relative potency ratio between levobupivacaine, ropivacaine and bupivacaine is 0.76∶0.57∶1.00. ConclusionThe relative potency ratio be tween levobupivacaine, ropivacaine and bupivacaine is 0.76∶0.57∶1.00.