[Effects of different doses and concentrations of ropivacaine in axillary brachial plexus block].

OBJECTIVE: To evaluate clinic pharmacodynamics of ropivacaine hydrochloride, a new long-acting amide type local anaesthetic, in Chinese patients undergoing neurolysis and tendolysis of forearm through axillary brachial plexus block. METHODS: Two hundred ASAI-II persons, aged 18-65,weighing 60-75 kg, undergoing neurolysis and tendolysis of forearm under axillary brachial plexus block were randomly assigned to 4 equal groups to received ropivacaine of the doses of 1.00 mg/kg (Group I), 1.25 mg/kg (Group II), 1.50 mg/kg (Group III), and 2.00 mg/kg (Group IV). Each group was subdivided into 5 equal subgroups according to the concentrations (0.15%, 0.20%, 0.25%, 0.30%, and 0.35%). The effects were analyzed. Results There was no significant difference in starting time, consummating time, and persisting time of sensory and motor nerve block between Group I and Group II (all P > 0.05). The starting time and consummating time of Group III and Group IV were all significantly shorter than those of Group I (all P < 0.05), and the persisting times of Groups III and IV were all significantly longer than those of Group I (P < 0.05). 90 minutes after brachial plexus block the degrees of muscle strength Groups I and II were M1 and M2 respectively, hence, the sensory and motor nerves block was in dissociation. When motor never block was above M3 and M4 the interval of brachial plexus block was 55 min and 27 min in Group III and Group IV respectively. CONCLUSION: Sensory and motor never can be blocked perfectly when the dose of ropivacaine is between 1.5 mg/kg and 2.0 mg/kg and the concentration is between 0.30%-0.35%. When the doses of ropivacaine is 1.25 mg/kg and the concentration is 0.20%-0.25% the starting and consummating time are longer and persisting time is shorter. When the doses of ropivacaine is 1.00 mg/kg and the concentration is 0.15%-0.20% the starting and consummating time are longer and only satisfies external debridement and suture without tourniquets.