You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Anesthetic agent with vasoconstrictor is contraindicated in? and explain in detail?
The use of vasoconstrictors (epinephrine or adrenaline) along with a local anesthetic is usually avoided in case of ring block or finger block as it causes severe vasocontriction (direct alpha adrenergic effect). As this vaso-constriction in the end aeries can lead to gangrene formation. Ref: Neural blockade in clinical anesthesia and management of pain, Issue 494 - Page 124, By Michael J. Cousins, Phillip O. Bridenbaugh; Fundamentals of Surgical Practice By Andrew Kingsnoh, Douglas Bowley, Page 147.