Anesthesia Techniques Flashcards

During a Gow-Gates mandibular block, the needle target is the condylar neck just below the insertion of the lateral pterygoid muscle. Which landmark is used to establish the correct vertical angulation of the needle?

Answer: The intertragic notch to the corner of the mouth line

In the Gow-Gates technique, the vertical angulation is guided by the intertragic notch-to-corner of mouth line. This directs the needle toward the condylar neck, the intended deposition site. Camper's line (tragus to ala of nose) is used for denture construction. The other landmarks are not standard references for the Gow-Gates technique.

A patient requires a mandibular block but has a bifid inferior alveolar nerve confirmed on CBCT. The standard IANB fails to achieve adequate pulpal anesthesia of the mandibular first molar. Which supplemental technique is MOST likely to achieve profound anesthesia in this anatomical variant?

Answer: Intraosseous injection at the interdental bone mesial to the first molar

A bifid inferior alveolar nerve means a second canal exists, often running inferior or medial to the primary canal. The standard IANB misses the accessory nerve. An intraosseous (IO) injection deposits anesthetic directly into the cancellous bone adjacent to the target tooth, bypassing the nerve trunk anatomy entirely and achieving pulpal anesthesia regardless of canal variants. A higher IANB may miss the accessory branch. The mental/incisive block does not provide pulpal anesthesia to molars. A buccal nerve block only anesthetizes soft tissue.

When administering a Vazirani-Akinosi closed-mouth mandibular block, the needle is inserted parallel to the occlusal plane of the maxillary teeth at the level of the mucogingival junction. What is the PRIMARY reason this technique is selected over a conventional IANB in the appropriate clinical scenario?

Answer: It is preferred when the patient cannot open wide due to trismus or limited opening

The Vazirani-Akinosi technique is a closed-mouth injection, making it the technique of choice when trismus, ankylosis, or other conditions severely limit mandibular opening. The conventional IANB requires adequate opening to visualize and access the retromolar triangle. Both the IANB and the Vazirani-Akinosi technique anesthetize the inferior alveolar, lingual, and mylohyoid nerves. Volume requirements are similar to the IANB. Onset is not necessarily faster with this technique.

A 52-year-old patient on a non-selective beta-blocker (propranolol) requires a maxillary molar extraction. During the injection of 2% lidocaine with 1:100,000 epinephrine, the patient develops a sharp rise in blood pressure followed by reflex bradycardia. What is the pharmacodynamic mechanism responsible for this reaction?

Answer: Beta-blockade unmasks epinephrine's alpha-1 vasoconstrictive effect, causing hypertension and reflex vagal bradycardia

Epinephrine acts on both alpha and beta receptors. In a normal patient, beta-2 vasodilation partially offsets alpha-1 vasoconstriction, and beta-1 stimulation causes tachycardia. When non-selective beta-blockers like propranolol block all beta receptors, epinephrine's alpha-1 vasoconstriction is unopposed, causing a significant hypertensive surge. The baroreceptor reflex then triggers a compensatory vagal (parasympathetic) response, producing bradycardia. This is a classic and clinically significant drug-drug interaction in dental anesthesia.

In the AMSA (anterior middle superior alveolar) injection, a single injection anesthetizes pulpal tissue from which range of teeth?

Answer: Maxillary central incisor through the second premolar, including the palatal tissue (#4–#13)

The AMSA injection targets the branches of the anterior and middle superior alveolar nerves as they converge on the palate, approximately at the junction of the first and second premolars midway between the midpalatal suture and the free gingival margin. A single injection can achieve pulpal anesthesia of the maxillary central incisor through the second premolar (five teeth) along with the associated palatal tissues—eliminating the need for multiple labial and palatal injections. It does not typically reach the first molar reliably.

During nitrous oxide/oxygen sedation, a patient suddenly becomes agitated, laughs uncontrollably, and then loses consciousness momentarily. Oxygen saturation drops to 88%. The most likely cause is:

Answer: Diffusion hypoxia due to rapid displacement of alveolar oxygen by nitrous oxide following a sudden increase in N2O delivery

Diffusion hypoxia (Fink effect) occurs when a large volume of nitrous oxide rapidly exits the bloodstream into the alveoli at the end of or during a sudden change in administration, diluting alveolar oxygen and causing a transient but significant drop in PaO2. This is why 100% oxygen must be administered for 3–5 minutes at case termination. The scenario of an abrupt N2O increase can produce a similar acute dilutional effect. Loss of consciousness and SpO2 drop are consistent with acute hypoxia. Methemoglobinemia from N2O is not a clinical concern at dental concentrations. Laryngospasm from N2O alone is not a recognized phenomenon.