Which dermatome requires blocking to effectively perform an inguinal hernia repair?

The correct choice is T12 for an inguinal hernia repair because this dermatome is responsible for sensation in the area around the lower part of the abdomen and the groin region. During an inguinal hernia repair, it is essential to block sensation across the lower abdomen and the groin to manage pain effectively and allow the surgical procedure to be performed with minimal discomfort to the patient.

Since the inguinal region is innervated by the ilioinguinal nerve, which arises from the L1 nerve root, there is also some involvement of L1. However, T12 can often overlap in sensation and is important for ensuring the entire area is adequately anesthetized, particularly because the T12 nerve contributes to the feeling in the lower abdomen.

Blocking T12 helps in providing anaesthesia across a broader range, including the lower part of the abdominal wall and also ensures that sensation is adequately managed post-surgery.