Convulsions associated with ropivacaine 300 mg for brachial plexus block

Editor—We thank Drs Gayer and Palte and Prof. Kumar for this important note regarding the technical side of using ultrasound for regional anaesthesia in eye surgery. We are aware of the potential risk of ultrasound waves, especially for sensitive structures like neuroretinal tissue. Our cadaver study was intended to prove the concept of a new technique without danger to patients. We investigated the ultrasound-guided correct placement of the needle and the proper spread of the applied drug. The bioeffects of ultrasound were not in the scope of our investigation. The ultrasound device used for our study on cadavers did not meet the quoted FDA limits, especially not the limits for the MI which was 0.4 and therefore higher than 0.23. In this case, the energy applied to the eyes did not make any difference as the subjects were cadavers. We agree that the use of ultrasound for eye block anaesthesia should improve the safety rather than represent a potential risk to the eye tissues. Therefore, only orbital-rated transducers for in vivo sonography meeting FDA recommendations should be used for clinical studies and daily routine practice. The lower output energy of these transducers does not impair the detection of intraorbital structures or needles used for the eye block—and the method described in our study is also valuable with other small curved array transducers. Companies providing ultrasound equipment will produce suitable transducers in the near future which will be in accordance with the regulations.