In Reply:—

Thank you for the opportunity to reply to Dr. Scott Lang's letter, in which he discusses the use of the nerve stimulator to perform thoracic paravertebral block (TPVB). I was aware of various authors alluding to the use of a nerve stimulator to facilitate intercostal nerve block and TPVB. A discussion of this method was not included in my review on TPVB 1because there was a lack of published data on the specifics and safety. However, after the publication of my review, Wheeler reported on the technical details about using a nerve stimulator to perform TPVB 2and Dr. Lang now provides additional information.

Because tactile localization of the TPVS using loss of resistance is subjective and indefinite 1there may be potential merits in using a nerve stimulator to perform TPVB, as suggested by Dr. Lang. Locating the spinal nerve in the TPVS using nerve stimulation is an objective method of performing TPVB and may improve the overall success rate and make the technique safer, especially when clinical conditions make TPVB technically more demanding, such as in patients with morbid obesity or with distorted thoracic anatomy. However, before we can recommend it for routine use there is a need to evaluate its safety, success rate, and complications, because, as outlined by Dr. Lang, there are several potential limitations. These include the need to use relatively high current intensity (1–5 mA) during initial simulation that can induce paresthesia, inability to readily observe a motor response in obese patients, and the need for an assistant to palpate the chest for the motor response. Moreover, local anesthetic injected at one thoracic level can spread to the contiguous levels (depending on David C. Warltier, M.D., Ph.D., was acting Editor-in-Chief for this correspondence. the volume injected) where it may either modify or abolish the intercostal motor response to spinal nerve stimulation predisposing to deep needle insertion and possible pleural puncture during a multiple injection TPVB. Despite some of these potential limitations the technique of using nerve stimulation to perform TPVB is definitely worthy of further investigation.

Karmakar MK: Thoracic paravertebral block. A nesthesiology 2001; 95 (3): 771–80
Wheeler LJ: Peripheral nerve stimulation end-point for thoracic paravertebral block. Br J Anaesth 2001; 86 (4): 598–9