[A study on diaphragm function after interscalene brachial plexus block using a fixed dose of ropivacaine with...

To compare the effect of interscalene brachial plexus block (ISBPB) on the incidence of diaphragmatic paralysis, respiratory function and post-operative pain control using same dosage of local anesthetics diluted into two different volume and concentrations.

Approved by the Peking University Third Hospital ethics committee, sixty patients undergoing elective arthroscopic shoulder surgery in Peking University Third Hospital from November 2013 to April 2014 were randomly allocated into two groups according to random number table method: before induction of general anesthesia, ultrasound-guided ISBPB was performed using 0.5% ropivacaine 10 ml (Group A) or 0.25% ropivacaine 20 ml (Group B). The incidence of diaphragmatic paralysis, respiratory function and reduction of pulse oxygen saturation at 30 min post-block were recorded and analyzed.Patients were interviewed at 4, 8 and 24 h after block for numerical rating pain score, rescue analgesics requirement and sleep quality.

There were no statistically differences between group A and group B for the incidence of diaphragmatic paralysis at 30 min after block (67% vs 70%, χ(2)=0.077, P>0.05). The change of forced vital capacity ((78±16)% vs (80±18)%, t=0.435, P>0.05), the change of forced expiratory volume in 1 second ((85±16)% vs (78±22)%, t=1.472, P>0.05) and the reduction of pulse oxygen saturation (1(0-3)% vs 2(0-3)%, Z=-0.538, P>0.05) showed no significant differences between the two groups at 30 min after block.There were no statistically differences in terms of the numerical rating pain score, rescue analgesics requirement and sleep quality at 4, 8 and 24 h after block (all P>0.05).

The use of 0.5% and 0.25% ropivacaine 50 mg for interscalene block provides similar effect on the incidence of diaphragmatic paralysis, changes in respiratory function and postoperative analgesia.