If there is acute inflammation at the planned injection site, what is the status of PSA nerve block?

• A. It is contraindicated
• B. It is indicated
• C. It depends on patient
• D. It is preferred if only soft tissue is involved

Answer: (A)

Acute inflammation at the planned injection site makes a PSA nerve block contraindicated. In inflamed tissue, the environment becomes acidic and edematous, which affects how local anesthetics work. Local anesthetics are weak bases, and in an acidic setting fewer molecules are in the uncharged form needed to diffuse across nerve membranes, so onset is slower and the block is less reliable. Edema and increased tissue vascularity in inflammation also wash the drug away more quickly, further reducing effectiveness. There’s also a concern that injecting near an infected area can spread bacteria or lead to less controllable spread along tissue planes, increasing the risk of complications. Because of these issues, it’s better to avoid the PSA block in the presence of acute inflammation and use infiltration in non-infected tissue or postpone until inflammation subsides.