Final answer:
A nerve block provides the longest duration of anesthesia by targeting nerve pathways directly, offering precise control and prolonged pain control.
Step-by-step explanation:
The type of injection technique that provides the longest duration of anesthesia is b. nerve block. Nerve blocks involve injecting anesthetic directly near the nerves associated with the surgical site and generally provide longer-lasting numbness compared to other techniques. The mechanism behind this involves local anesthetics blocking nerve conduction temporarily. This method is favorable when prolonged pain control is required, for it targets nerve pathways directly and offers more precise control over the area of anesthesia.
Infiltration involves directly injecting the anesthetic into the tissue around the surgical site, and its effects are shorter in duration compared to nerve blocks. The duration of anesthesia by infiltration can be limited due to faster dispersion and absorption of the anesthetic into surrounding tissues.
A field block is when anesthetic is injected around the area but not directly at the surgical site. It provides a more widespread area of anesthesia by targeting the terminal nerve endings in the tissue. However, it also does not last as long as a nerve block. The choice among these techniques is determined by the type and duration of the procedure, as well as the patient's specific conditions and requirements.