[Subdural, extra-arachnoid block as a complication of stellate ganglion block: documentation with ultrasound]

We present a patient who developed a high central neural block after stellate-ganglion-blockade. The underlying pathophysiology was assessed via sonographic imaging. Stellate ganglion block was performed in a 19-year old patient according to the standard technique. Multiple aspiration tests were negative and a test dose of 3 ml bupivacaine 0.25% was injected. After a 3 min interval another 5 ml were injected. Two minutes after the local anaesthetic administration the patient reported nausea and sensations in the upper extremity. Spontaneous respiration efforts stopped, and the patient became unconscious. Tracheal intubation was performed, and the patient was ventilated in a controlled mode for two hours. Heart rate as well as blood pressure remained within the normal range. Neurologic recovery occurred rapidly and extubation was performed about two and a half hours after the event. Our sonographic studies demonstrated a local anaesthetic depot directly at the root of C 6, with a mean diameter of 10 mm and a length of 5 to 6 cm (about a third smaller than expected). Sonographic studies and clinical symptoms of our patient are most likely to occur with a subdural extra-arachnoidal block. Ultrasonographic guided puncture enhances the patient's safety by the opportunity to directly visualise transverse process, nerval root as well as local anaesthetic depot. In case of depot formation directly at the nerval root, injection may be stopped and the needle repositioned. Furthermore, direct visualisation of the great vessels (A. vertebralis) prevents intravascular injection and haematoma formation.