Convulsions Induced by Ropivacaine During Interscalene Brachial Plexus Block

To the Editor:

We read with interest the case report of Korman and Riley ^[1]. We agree that ropivacaine possesses a greater margin of security ^[2] and may progressively replace bupivacaine when large doses of local anesthetics must be given. Indeed, to avoid this complication and to improve the educational value of this case report, we believe a few more details are needed.

The administration of a test dose in this patient is debatable. Indeed, the intravascular injection of ropivacaine 15 mg (2 mL of 0.75%) is not likely to cause any relevant clinical symptoms. McClure ^[2] reported an inadvertent IV injection of ropivacaine 70-200 mg in five patients, none of whom showed any sign of cardiotoxicity. Convulsions occurred in one patient, who received ropivacaine 200 mg intravascularly during axillary brachial plexus block. The reduced central nervous toxicity of ropivacaine suggests that this drug is not reliable as a test dose. It would be interesting to know whether epinephrine or some other adjuvant had been added to ropivacaine. Ropivacaine 15 mg alone is not sufficient to uncover an inadvertent IV injection. An aspiration test also is not reliable, because multiple reports of an intravascular injection of a local anesthetic after negative aspiration are available ^[3,4]. Although the use of epinephrine as a test dose does not meet the desired criteria of simplicity, easy monitoring, and clear end points, we believe that, in such a doubtful situation (previous blood aspiration), the addition of a small dose of epinephrine (15 [micro sign]g) in a normotensive and calm patient could have been more helpful.

Finally, some technical points deserve mention when dealing with interscalene blocks. At which level was the needle inserted? Was it at C6, according to Winnie ^[5]. How was the needle orientated? This point is important because most complications appear when the needle is medially and coronally directed ^[6,7]. To perform a single-shot interscalene block, the needle should be posteriorly, medially, and particularly slightly caudally directed, as recommended by Winnie ^[3]. We also wonder why the authors intentionally produced paresthesias, although they were using a neurostimulator. One of the reasons to use a neurostimulator is to avoid the elicitation of paresthesia! As this is the first reported case of convulsions following the use of ropivacaine in this clinical setting, it would be interesting to know whether the authors measured the actual blood levels of ropivacaine. Interscalene block is a very useful anesthetic technique for shoulder surgery, and certain technical principles must be respected to avoid serious complications.

A. Borgeat, MD

Y. A. Ruetsch, MD

M. Jorg, MD

Department of Anesthesiology; University Clinic of Zurich/Balgrist; CH-8008 Zurich, Switzerland