What good studies are out there? The only one I've seen is one from Mexico using 3-5cc of local, but it was a pretty bad study...the reason I am using 40cc of 0.5% with epi (fresh) is to try to get 24-36 hours out of the block...are you able to get that duration consistently with 10cc? just curious...any direction would be appreciated
Wow, 24-36 hrs??? We usually are aiming to get about 12-18 hrs max out of the blocks, hence our results with lesser volumes (10ml 0.5% Bupiv + Epi) are yielding fairly similar results as the study I mentioned before, which is here:
1: Br J Anaesth. 2008 Oct;101(4):549-56. Epub 2008 Aug 4. Links
Effect of local anaesthetic volume (20 vs 5 ml) on the efficacy and respiratory consequences of ultrasound-guided interscalene brachial plexus block.
Riazi S, Carmichael N, Awad I, Holtby RM, McCartney CJ.
Department of Anesthesia, Sunnybrook Health Sciences Center, University of Toronto, 2075 Bayview Avenue, Toronto, Ontario, Canada M4N 3M5.
BACKGROUND: Interscalene brachial plexus block (ISBPB) is an effective nerve block for shoulder surgery. However, a 100% incidence of phrenic nerve palsy limits the application of ISBPB for patients with limited pulmonary reserve. We examined the incidence of phrenic nerve palsy with a low-volume ISBPB compared with a standard-volume technique both guided by ultrasound. METHODS: Forty patients undergoing shoulder surgery were randomized to receive an ultrasound-guided ISBPB of either 5 or 20 ml ropivacaine 0.5%. General anaesthesia was standardized. Both groups were assessed for respiratory function by sonographic diaphragmatic assessment and spirometry before and after receiving ISBPB, and after surgery. Motor and sensory block, pain, sleep quality, and analgesic consumption were additional outcomes. Statistical comparison of continuous variables was analysed using one-way analysis of variance and Student's t-test. Non-continuous variables were analysed using chi(2) tests. Statistical significance was assumed at P<0.05. RESULTS: The incidence of diaphragmatic paralysis was significantly lower in the low-volume group compared with the standard-volume group (45% vs 100%). Reduction in forced expiratory volume in 1 s, forced vital capacity, and peak expiratory flow at 30 min after the block was also significantly less in the low-volume group. In addition, there was a significantly greater decrease in postoperative oxygen saturation in the standard-volume group (-5.85 vs -1.50, P=0.004) after surgery. There were no significant differences in pain scores, sleep quality, and total morphine consumption up to 24 h after surgery. CONCLUSIONS: The use of low-volume ultrasound-guided ISBPB is associated with fewer respiratory and other complications with no change in postoperative analgesia compared with the standard-volume technique.