In which situation is it particularly critical to avoid injecting local anesthetics?

Injecting local anesthetics in an infected area is particularly critical to avoid because the presence of infection can alter the effectiveness of the anesthetic. Infected tissues are often acidic, which can change the ionization of the local anesthetic. As a result, the anesthetic may not adequately penetrate the nerve membranes and achieve the desired numbing effect. Furthermore, injecting anesthetics into an inflamed or infected area increases the risk of complications, such as increased pain, inadequate anesthesia, and potential systemic toxicity.

In contrast, injecting in a fasting patient, a well-hydrated patient, or during a surgical procedure typically does not present the same level of risk associated with the presence of infection. Therefore, avoiding injection in an infected area is essential for ensuring patient safety and the effectiveness of the anesthesia.