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Ultrasound vs Neurostimulation for Placement of Interscalene Catheters

Title
A prospective randomized comparison of ultrasound and neurostimulation as needle end points for interscalene catheter placement
Authors
Frederickson MJ, Ball CM, Dalgleish AJ et al.
Journal
Anesthesia and Analgesia 2009; 108: 1695-700.

 

Study Summary

 

The study enrolled 81 patients undergoing shoulder surgery with a interscalene nerve block catheter placed for postoperative analgesia. Patients were randomized to one of two groups: 1) appropriate needle tip position confirmed by ultrasonographic visualization, or 2) by an appropriate motor response to neurostimulation. All the blocks were performed by a single experienced operator, who set himself a maximum time limit of 5 minutes for obtaining either a satisfactory ultrasound image or appropriate motor response upon needle insertion. The catheter itself was advanced blindly 2-3 cm beyond the needle tip and 30 mls of 0.5% ropivacaine was delivered through the catheter. All patients received a general anesthetic in addition to the block.

 

The US-guided technique was associated with statistically significant (but clinically insignificant) decreases in needle-under-skin time (30 seconds) and block associated pain scores. Measures of postoperative analgesic quality were equivalent between groups. Three patients in the US-guided group and 6 patients in the NS-guided group had transient neurological symptoms (overall incidence 11%).

 

This study demonstrates that both techniques are equally effective in experienced hands. It should be noted that the operator failed to obtain an adequate ultrasound image within the stipulated time limit in one patient, who subsequently had a successful neurostimulation-guided block. Ultrasound is clearly not infallible, and operator experience and expertise are definitely factors that affect the success of the techqniue. We agree with the authors when they recommend that neurostimulation should always be available for use if necessary. At the same time, there are multiple studies indicating that the sensitivity and specificity neurostimulation is also not ideal. In our practice, we commonly combine both ultrasound and neurostimulation as endpoints for needle placement; we view both techniques as complementary and not mutually exclusive.