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Two case reports illustrate that low doses of local anaesthetics such as bupivacaine 2.5 mg and a mixture of bupivacaine i .25 mg and lidocaine 5 mg can induce grand real seizures if injected into the vertebral artery during stellate ganglion block.The effect of the dose of local anaesthetic agent and technique of administration into the stellate ganglion region discussed as is the relationship between vertebral artery blood flow and cerebral intravascular local anaesthetic concentration required to produce seizure activily. Suggestions are made concerning possible modification of the technique of anterior approach to the stellate ganglion, including test dose size, to reduce the incidence of inadvertent injection into the vertebral artery and subsequent central nervous system toxicity.KEY WORDS: ANAESTHETIC TECHNIQUES, regional, stellate block; COMPL1CA-XlONS, convulsions, local anaesthetics.THE ANTERIOR paratracheal approach at C61 is a technique commonly employed for blockade of the stellate ganglion. One of the serious potential complications with the use of this technique is inadvertent injection of the local anaesthetic solution into the vertebral artery. Previous case reports indicate that doses of bupivacaine as low as 7.5 mg and probably lidoeaine 10 mg can produce grand mal seizures when injected into the vertebral artery. 2"3 The symptoms associated with inadvertent injection of local anaesthetic into the vertebral artery range from transient nausea, dizziness, slurred speech and sedation to temporary blindness, loss of consciousness and, finally, grand mai seizures. The following two case reports document grand mal seizures that occurred during stellate ganglion block with doses of local anaesthetic much lower than those previously reported. The effect of mass of local anaesthetic agent and technique of administration of the drug into the stellate ganglion region is discussed, as is the relationship between vertebral artery blood flow and cerebral intravascular local anaesthetic coneentration required to produce seizure activity.Based on two case reports, some suggestions are made concerning possible modification of the technique of anterior approach to the stellate ganglion, including test dose size, to reduce the incidence of inadvertent intravertebral artery injection and subsequent central nervous system toxicity. CASE REPORTS Case IA diagnostic stellate ganglion block was planned for a 55 year old 60 kg man with diffuse burning pain in the left upper extremity.An intravenous infusion was established in the opposite arm. The patient was placed in a 20 degree head up position and the neck was fully extended. A paratracheal approach was used with a 25 gauge 3.75 cm needle attached to a 10 ml syringe. Bony contact was made at the level of C6 and the needle was then withdrawn 3 mm. Following negative aspiration, a test dose of 0.5 ml of bupivacaine 0.5 per cent was injected.Within five seconds after the injection generalized rigidity developed, which was followed by a grand mal seizure. The s...

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