Abstract ID: A16
Abstract Title: Nerve Stimulator or Ultrasound for Coracoid Infraclavicular Brachial Plexus Block: Influence of needle position on nerve stimulation and spread of injectate.
Poster Type: Discussion
ABSTRACT BODY
Purpose
Both ultrasound and nerve stimulation are useful methods of localization during coracoid infraclavicular brachial plexus block. However, combined use of ultrasound and nerve stimulation has not been evaluated. We aimed to determine if (i) ultrasound facilitates block needle placement to obtain distal muscle stimulation in the upper limb and if (ii) local anesthetic spread correlated with needle tip location, type of muscle stimulation and successful block.
Methods
After REB approval and informed consent, 26 patients scheduled for surgery distal to the elbow underwent infraclavicular brachial plexus block. Nerve stimulation (Stimuplex, Braun) and ultrasound guidance (linear 4-7 MHz probe, Philips HDI 5000 unit) was used to seek muscle stimulation distal to the elbow with a 17 G insulated needle (Arrow, Reading, PA). The site of muscle contraction and the minimum stimulating current were recorded. After negative aspiration, 40 mL Lidocaine 1.5% with 1:200,000 epinephrine was administered in 5 ml increments via the needle or catheter. Block success was defined as the presence of surgical anesthesia within 30 minutes of injection. The final position of the catheter (or needle tip) and the pattern of local anesthetic spread following injection were subsequently correlated with block success.
Results
The overall block success rate was 81% (21/26 patients). The relationships between catheter position, stimulation type, local anesthetic spread and block success are summarised in Table 1.
Distal muscle stimulation was found in 12 patients when the needle was positioned under ultrasound guidance posterior to the 2nd part of the axillary artery (PA position) and in 4 patients when the needle was between the axillary artery and vein (AV position). All 16 patients had successful block (see table).
In the remaining 10 patients, distal muscle stimulation could not be obtained in any position around the axillary artery: in 9 of these patients the catheter was positioned posterior to the artery (PA) before injection. Successful block occurred in 5/9 (56%) of these patients.
There was one case of vascular puncture whilst attempting to place the needle in the AV position.
Conclusion
Ultrasound guidance is a useful method for placing the needle around the axillary artery during infraclavicular block.
The most reliable predictor of block success was distal stimulation prior to injection either through needle or catheter (16/16, 100%).
In addition successful block was usually preceded by visualization of local anesthetic spread posterior to the axillary artery (95%, 20/21).
No spread of local anesthetic anterior to the axillary artery was observed in any patient with successful block.
In a significant number of patients (10/26, 38.5%), we were unable to identify distal muscle stimulation superior, inferior or posterior to the 2nd part of the axillary artery. Ultrasound can be used to facilitate block placement in these cases.
ATTACHED FILES
A16_ASRA infraclavicular ultrasound table.doc
Reg Anesth Pain Med 2004; 29(2):A16