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Friday, October 24, 2014
Failure of Bier Block-is this common?
About 2 months ago, I had ulnar nerve and carpal tunnel surgery on my right arm/hand with a Bier Block, which was awesome. I didn`t want any IV sedation unless absolutely necessary (previous bad experience with this) and the CRNA complied with this request giving me 45mg of propofol and 4ml of fentanyl total during the procedure, which took just over 1 hour. I was awake and aware, just as I wanted to be and the numbness in my arm was absolute. Last week I went back to have the other arm/hand done, everything else the same and it was a very painful procedure; despite them using a lot more propofol and fentanyl....But the procedure came out well; I`m not complaining. My arm never got numb and it was a long and painful experience. I have to undergo another procedure shortly in which this same type of block is used; my question is: how common is it for these blocks to fail? My right arm/hand were about the same as far as the EMG/NCV tests went and everything else was the same, the block just didn`t seem to work. Thanks.
A Bier block is a safe and effective anesthetic for short surgical procedures on the arm, and, less commonly, the leg. Bier block is also known as intravenous regional block. I don't have any statistics on how often Bier blocks fail, but this does happen occasionally.
For a Bier block to be effective, the arm must be exsanguinated as much as possible (the arm is elevated and venous blood is squeezed out of the arm using a long elastic bandage). Then the blood pressure cuff is inflated above systolic blood pressure. If the inflation pressure is not high enough, or the exsanguination is done poorly, the block is less likely to succeed because the local anesthetic is diluted. If you have high blood pressure a Bier block is less effective.
A variety of different drugs have been used in Bier blocks. The main agent is a local anesthetic like lidocaine, but additional drugs ("adjuvants") have been used to make the block more effective or last longer. Sometimes the continued pressure applied by the cuff becomes very uncomfortable, even unbearable, and this is the main reason why some intravenous sedation is necessary. Finally, Bier blocks have a finite duration, related to the duration of action of the local anesthetic but also to the length of time that the tissues of the arm can tolerate being without their blood supply. The maximum time is about 90 minutes.
Gareth S Kantor, MD
Assistant Professor of Anesthesiology
School of Medicine
Case Western Reserve University