Snapshot A 36-year-old man presents to the emergency department with a wound laceration of the hand. He is a construction worker that accidently cut himself with his tools approximately 2 hours prior to presentation. His most recent tetanus vaccination was given 2 years ago. There does not appear to be any possible contamination or foreign body at the site. The wound extends beyond the dermis. Wound irrigation is commenced and a local anesthetic is administered prior to suturing. Introduction Local anesthetics prevent sensory nerve impulses from reaching the central nervous system (CNS) this is accomplished by blocking the inner portion of the sodium channel login to view 2 more bullets structure a lipophilic group is joined to a hydropilic group via login to view 5 more bullets onset and duration of action influenced by login to view 8 more bullets effects local anesthetics can result in vasodilation, which login to view 3 more bullets order of nerve blockade small-diameter fibers > large diameter fibers and myelinated fibers > unmyelinated fibers login to view 1 more bullet order of loss (first) pain → temperature → touch → pressure (last) Medications Medication esters benzocaine, cocaine, procaine, and tetracaine amides bupivacaine, lidocaine, and mepivacaine Clinical use minor surgical procedures spinal anesthesia Adverse effects CNS symptoms excitation or depression cardiovascular toxicity (bupivacaine) arrhythmia methemoglobinemia (benzocaine)