An 23yo 81kg male underwent uneventful I.S. block for shoulder surgery using a nerve stimulator. Versed 5mg was given, along with 20cc 0.5% marcaine and 20cc 2% lidocaine. The patient tolerated the procedure well and had no indication of intravascular injection. He went into the OR about 20 minutes later and was sedated with diprivan(no lido) for approx 1.5 hours without incident. Ancef was the only other drug given. When the patient arrived in PACU, he was just waking up and was shivering and also appeared "twitchy" to all observers. His VS were stable but he couldn't verbalize and was noted to be grinding his teeth and having uncoordinated movements of all extremities except the blocked arm. Demerol was given initially to decrease the shivering but the other symptoms persisted. A presumptive diagnosis of LA toxicity was reached even though the block had been done approx 2 hours before. I have seen LA toxicity post block 3 times, once c/w inadvertent vascular injection and twice c/w absorption of the drugs. This patient's clinical picture was c/w a delayed absorption and I opted to treat it with lipids. 250cc 20% lipids was hung and infused over 20 min. After about half the bag was in, the patient was able to be still and answer questions by nodding. After the whole bag was infused, the patient could verbalize but was still a little sedated. 30 minutes after the infusion, he was alert and appropriate, without complaints. He does not give any history of prolonged action of LAs in the past. Perhaps he has a defect in metabolism of these drugs and this is his first large exposure...I discussed this with him in PACU and gave him a copy of my progress note for future anesthesia providers to review. I am convinced that the lipid emulsion improved this patient's condition.

Hey Jim, Thanks for posting this very interesting case. If you've heard me talk, I always point out that the rapid onset of symptoms generally given in classic text book version of LA toxicity might be classic, but isn't typical. Only about 40% are immediate, about 40% are delayed 10-15 minutes and as many as 10-20% are delayed even longer. There are reports in the literature similar to yours...delays of 90 minutes or longer. This is probably even more common but just underdiagnosed. If it looked like the lipid made things better, I'm betting you got it right. I always trust the experienced eyes in the field; Thanks for the post.
guy