Anesthesia Techniques Flashcards

During a Gow-Gates mandibular block, the needle target is the neck of the mandibular condyle. Which landmark is used to orient the syringe barrel during this injection?

Answer: The tragus-corner of mouth line (Camper's line)

The Gow-Gates technique orients the syringe barrel along a line from the intertragic notch (tragus) to the corner of the mouth on the side being anesthetized. This trajectory directs the needle toward the neck of the condyle, where the mandibular nerve trunk lies before it branches, providing more comprehensive mandibular anesthesia than a conventional IANB.

A patient receiving an inferior alveolar nerve block develops anesthesia of the lower lip but the first mandibular molar remains sensitive to pulpal testing. Which supplemental technique is MOST appropriate as the next step?

Answer: Perform an intraosseous injection at the interproximal site adjacent to the molar

When the lip is numb (confirming the IANB reached the nerve) but the molar remains sensitive, the issue is typically inadequate diffusion through dense cortical bone — especially common in mandibular molars with inflamed pulps (lowered pH reduces anesthetic efficacy). An intraosseous injection delivers anesthetic directly into the cancellous bone adjacent to the tooth apex, bypassing the cortical barrier and achieving rapid pulpal anesthesia.

Which of the following physiological mechanisms explains why local anesthetics are LESS effective when injected into an acutely infected, abscessed area?

Answer: The acidic pH of inflamed tissue increases the ionized form of the anesthetic, reducing membrane penetration

Local anesthetics are weak bases that exist in equilibrium between ionized (RNH⁺) and un-ionized (RN) forms. Only the un-ionized free base crosses the lipid nerve membrane, but the ionized form binds the sodium channel receptor intracellularly. In infected tissue, the pH is acidic (~6.0–6.5 vs. normal 7.4), which shifts the equilibrium heavily toward the ionized form, dramatically reducing the fraction able to penetrate the nerve sheath. This is the primary pharmacological reason for reduced efficacy.

An adult patient with a documented allergy to para-aminobenzoic acid (PABA) requires local anesthesia. Which agent is the SAFEST choice?

Answer: Articaine with epinephrine

Procaine, benzocaine, and tetracaine are all ester-class local anesthetics that are hydrolyzed to PABA derivatives, making them contraindicated in patients with PABA allergy. Articaine is an amide anesthetic (with a unique thiophene ring) and does not metabolize to PABA. Amide anesthetics as a class are safe alternatives for PABA-sensitive patients. Note that articaine is an amide despite containing an ester linkage in its side chain — it is still classified and metabolized as an amide.

During administration of a posterior superior alveolar (PSA) nerve block, a hematoma rapidly forms in the infratemporal fossa. Which vessel is MOST likely responsible?

Answer: Pterygoid plexus of veins

The pterygoid plexus of veins is a dense venous network surrounding the lateral pterygoid muscle within the infratemporal fossa — exactly where the PSA needle travels. Because the PSA block requires inserting the needle superiorly, posteriorly, and medially at a 45° angle, it passes close to this plexus. Needle penetration causes rapid venous hemorrhage that disperses into the loose connective tissue of the fossa, producing a hematoma. This is the most common complication of the PSA block.

A 70 kg adult patient has already received two cartridges of 2% lidocaine with 1:100,000 epinephrine. The clinician needs additional anesthesia and is considering a third cartridge. What is the PRIMARY concern regarding the epinephrine dose, and what is the maximum recommended epinephrine dose for a healthy adult?

Answer: Cardiovascular toxicity; maximum is 0.2 mg epinephrine for healthy adults

Each 1.8 mL cartridge of 1:100,000 epinephrine contains 0.018 mg of epinephrine. Two cartridges deliver 0.036 mg. For healthy (ASA I–II) adults, the ADA/Malamed guideline permits a maximum of 0.2 mg epinephrine per appointment. The primary concern with excess epinephrine is cardiovascular toxicity: tachycardia, hypertension, and arrhythmia. For cardiac-compromised patients (ASA III–IV), the limit is reduced to 0.04 mg. With two cartridges used, a third (0.054 mg total) remains well within the healthy adult limit, but the clinician must track the cumulative dose.