Local Anesthesia and Pain Management
Nerves, drugs, and dose math
Maxillary anesthesia: posterior superior alveolar for molars (except the mesiobuccal root of the first molar, which may need supplemental infiltration), middle superior alveolar for premolars, anterior superior alveolar for anteriors, greater palatine for posterior palatal tissue, and nasopalatine for the anterior palate. Mandibular: inferior alveolar block, with Gow-Gates and Vazirani-Akinosi as alternatives, plus long buccal and lingual injections; the mental and incisive nerves supply premolars and anteriors.
Cartridge math is heavily tested. A cartridge is 1.8 mL, and mg = percent concentration × 10 × mL. One cartridge therefore contains 36 mg of 2% lidocaine, 72 mg of 4% articaine, and 54 mg of 3% mepivacaine. Maximum recommended doses: lidocaine 4.4 mg/kg (absolute max 300 mg), articaine 7 mg/kg (500 mg), mepivacaine 6.6 mg/kg (400 mg), prilocaine 8 mg/kg (600 mg), bupivacaine 1.3 mg/kg (90 mg). Epinephrine 1:100,000 delivers 0.018 mg per 1.8 mL cartridge; a healthy adult limit is about 0.2 mg.
Traps: articaine's association with lingual paresthesia after mandibular blocks; methemoglobinemia with prilocaine and benzocaine; epinephrine with nonselective beta blockers, uncontrolled hyperthyroidism, or pheochromocytoma. Syncope is the most common adverse reaction. Other complications include hematoma, trismus, and needle breakage.
Rule of thumb: calculate before injecting - a 60 kg patient at 4.4 mg/kg allows 264 mg, about 7 cartridges of 2% lidocaine.