| Ropivacaine (RP) is a new, long-acting aminoamide local anesthetic. It is a pure S-(-) enantiomer monohydrate of the hydrochloride salt. It is close to bupivacaine and mepivacaine in that it has a propyl group on the piperidine nitrogen atom, whereas mepivacaine has a methyl group and bupivacaine has a butyl group. Both mepivacaine and bupivacaine are the racemic mixtures of the enantiomers. The physicochemical properties of ropivacaine and bupivacaine apper are similar. Ropivacaine is slightly less potent compared with bupivacaine. The onset time is short and the duration of action is long. The central nervous system toxicity and cardiotoxicity of ropivacaine is lower than that of bupivacaine. Ropivacaine produces markedly sensory motor separation and has an intrinsic vasoconstricting property when used in low concentration. The pharmacodynemics and pharmacokinetics of ropivacaine used for lumber epidural or brachial plexus had been studied in some countries. This study is to investigate the pharmacodynemics and pharmacokinetics of ropivacaine, to confirm the necessity of ropivacaine with adrenaline for upper thoracic epidural anesthesia (UTEA). Material and MethodThis study included 20 female patients scheduled to undergo breast surgery under continuous UTEA(ASA I ~ II, aged 20~47 years). They were randomly divided into two groups: Group RP (ropivacaine group, n=10)and Group RP+AD (ropivacaine withadrenaline group, n=10). UTEA was performed at the T3-4 interspace by using epidural catherter. Patients of Group RP and RP+AD received 5mg ?L-1 RP 1.3mg ?kg-1 and 5mg ?L-1 RP 1.3mg ?kg-1 plus adrenaline 5 g . kg epidurally in 2 min, respectively. Sensory block was determined using a blunt point needle to test for loss and return of sensation to pin-prick. Motor block was assessed using a myodymamia scale (0 V). Assessments of sensory and motor block were performed at 1 min or 3 min intervals in first 30 min after injection of total dose, and thereafter at 30 min intervals until normal sensation and motorfunction had been reestablished. During anesthesia, SBP, DBP, MAP, HR, ECG and SpO were continuously recorded by automatic monitor. RR were counted by anesthetist and FVC was measured by spivometer. The adverse reactions were recorded during anesthesia. Twenty patients had peripheral venous blood samples (4mL) collected for assay of the total plasma concentration of RP. Samples were taken immediately prior to the start of epidural administration(time 0 )and 10, 20, 30, 40, 50, 60, 90, 120, 150, 180, 240, 360 and 720 min after injection.The samples were drawn into heparinized tubre, centrifuged and frozen at -20 癈 until drug assay. The total plasma concentration of RP was determined by high performance liquid chromatography. The pharmacokinetic parameters were determined from plasma concentration-time data with 3P97 software package. Results1. Comparison of pharmacodynemic index between groups: the Group RP and RP+AD were similar with respect to epidural block characteristics. No significant difference in onset time, time to maximum spread, segment of spinal nerve blocked and onset time of motor block were observed between two groups (p>0.05). The number of patients with different degrees of motor block was similar in the two groups (p>0.05). Compared withGroup RP, the duration of sensory and motor block prolonged slightly, and no significant difference observed (see Tab. 3). 2. The changes of index for circulation and respiration: At 10,20,30 min after injection, there was a little decreased in SBP relative to baseline (p>0.05) in two groups; DBP and MAP decreased slightly and had no significant difference than the baseline (p>0.05) in Group RP; the DBP and MAP decreased markedly and had significant differences than the baseline (p<0.01) (DBP:66.611.4, 60.5 9.8, 62.8 ?3.2 vs 76.1 ?.7mmHg and MAP:82.9?.7,75.5?.7,78.2?.2 vs 90.15.7mmHg);HR had a larger decreased c...
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