Adductor Canal Block: Before or After the Case?

 

Danube at Kalocsa, Hungary - photo by JoAnn Sturman

Scott Sturman, M.D.

Our department’s preferred method for post op analgesia for ACLs and TKAs includes the placement of an adductor canal block.  At the conclusion of a TKA case last week, the surgeon asked, “Would you put in an ACB before the patient goes to the recovery room?”

“It’s already done.  I placed it before you started,” I responded.

The surgeon replied, “I was told the block doesn’t work well when it is put in before the tourniquet is inflated–something about the Esmark or tourniquet displacing the local anesthetic away from the nerve.”

“I’ve never heard that before.  How would that have any effect on the block?”

There may be a compelling reason for placing the ACB at the conclusion of the case when the tourniquet has been deflated, but it is difficult to support the argument from a fluid dynamic standpoint.  In the first place leg elevation and/or Esmark placement on the lower extremity only affects fluid in blood vessels.  Secondly, the ACB is placed well below the distal edge of the the tourniquet, so its compressive forces would have little influence on 20 or 30 ml of local anesthetic deposited around the superficial femoral artery at the level of the adductor canal.

On POD #1 it is not uncommon for the ACB to be working 24 hours after placement.  The most important considerations are an adequate volume of local anesthetic and making sure it is injected in the adductor canal on both sides of the superficial femoral artery.  

Danube at Budapest - photo by JoAnn Sturman