Basic Sciences and Anatomy Flashcards

A patient has an acute dentoalveolar abscess with local tissue pH of 6.5. The pKa of lidocaine is 7.9. Approximately what percentage of the lidocaine injected into this tissue exists in the ionized (BH⁺) form?

Answer: ~96%, greatly limiting membrane penetration

Using the Henderson-Hasselbalch equation: pH = pKa + log([B]/[BH⁺]). At pH 6.5 and pKa 7.9, log([B]/[BH⁺]) = −1.4, giving a ratio of ~0.04:1 (base:ionized). This means roughly 96% of lidocaine is in the membrane-impermeant ionized form, which explains the profound clinical failure of local anesthetics in infected, acidic tissue.

Which structure is NOT normally found within the pterygomandibular space and therefore would NOT be anesthetized by a properly placed inferior alveolar nerve block?

Answer: Facial nerve (CN VII)

The pterygomandibular space contains the inferior alveolar nerve and vessels, the lingual nerve (anteromedially), and the mylohyoid nerve (which branches just before the mandibular foramen). The facial nerve (CN VII) exits the stylomastoid foramen and distributes superficially over the face — it does not traverse the pterygomandibular space and is unaffected by an IAN block.

The chorda tympani nerve joins the lingual nerve in the infratemporal fossa. Damage to the chorda tympani proximal to this junction would specifically impair which two functions?

Answer: Taste from the anterior two-thirds of the tongue and parasympathetic secretomotor fibers to the submandibular and sublingual glands

The chorda tympani (a branch of CN VII) carries two distinct fiber types: special visceral afferent (SVA) fibers for taste from the anterior two-thirds of the tongue, and general visceral efferent (GVE) preganglionic parasympathetic fibers that synapse in the submandibular ganglion to drive secretion from the submandibular and sublingual salivary glands. The parotid gland is innervated by CN IX via the otic ganglion — not chorda tympani.

Although albumin has greater total binding capacity, which plasma protein has the HIGHEST affinity for amide local anesthetics and most significantly governs their free (active) fraction at clinical concentrations?

Answer: Alpha-1 acid glycoprotein (AAG)

Alpha-1 acid glycoprotein (AAG, also called orosomucoid) is an acute-phase reactant with high affinity but low capacity for amide local anesthetics. At therapeutic plasma concentrations, AAG is the dominant binding protein determining the free drug fraction. Albumin has much higher capacity but lower affinity, becoming more relevant at supratherapeutic concentrations. Conditions that elevate AAG (trauma, surgery, myocardial infarction) reduce free drug and may transiently increase apparent tolerance.

The Gow-Gates mandibular nerve block achieves a higher success rate than the conventional inferior alveolar nerve block partly because it targets the nerve trunk more proximally. What is the precise anatomical target of the Gow-Gates technique?

Answer: The neck of the mandibular condyle just inferior to the insertion of the lateral pterygoid muscle

The Gow-Gates block deposits anesthetic at the neck of the mandibular condyle, just below the insertion of the lateral pterygoid muscle, targeting the entire mandibular nerve trunk before it divides. This single injection can anesthetize the inferior alveolar, lingual, mental, incisive, mylohyoid, and buccal nerves simultaneously. Because the target is far superior and posterior to the conventional IAN injection site, accessory innervation via the mylohyoid nerve is included in the block.

During a vasovagal syncopal episode triggered by dental injection anxiety, which is the MOST accurate description of the primary hemodynamic mechanism?

Answer: Sudden withdrawal of sympathetic tone producing peripheral vasodilation and simultaneous vagally mediated bradycardia (Bezold-Jarisch reflex)

Vasovagal syncope (neurocardiogenic syncope) classically involves an initial sympathetic surge (fear/pain) followed by abrupt withdrawal of sympathetic tone combined with enhanced vagal (parasympathetic) output — together termed the Bezold-Jarisch reflex. The result is peripheral vasodilation (pooling, reduced preload) plus bradycardia, causing a precipitous fall in cardiac output and cerebral perfusion. Local anesthetic cardiotoxicity and histamine release are separate mechanisms with distinct clinical presentations.