Which of the following can lead to a lack of blood supply when used on fingers or earlobes?

Using a local anesthetic such as lidocaine in combination with epinephrine can lead to a lack of blood supply in tissues like the fingers or earlobes. This is primarily due to the vasoconstrictive properties of epinephrine, which is often added to local anesthetics to prolong their effect and minimize bleeding.

When epinephrine is introduced into a localized area, it causes blood vessels in that region to constrict, reducing blood flow. While this can be beneficial in some situations, such as during a surgical procedure where reduced bleeding is desired, it poses risks in areas with limited blood supply or where distal circulation is crucial, such as in the fingers and earlobes. This constriction can compromise the oxygen and nutrient supply to these tissues, potentially leading to ischemia and tissue necrosis if not monitored carefully.

In contrast, lidocaine alone does not have the same vasoconstrictive effect and is less likely to cause significant blood supply issues when used by itself. Therefore, the combination of lidocaine with epinephrine is specifically what can result in reduced blood flow to the fingers or earlobes, making this the correct answer.