Early signs and symptoms of local anesthetic toxicity include all but one of the following. Indicate the exception:
A. Tinnitus
B. Perioral numbness
C. Dizziness
D. Hypertension
Correct Answer: D. Hypertension
Manifestations of local anesthetic toxicity typically appear 1-5 minutes after the injection, but onset may range from 30 seconds to as long as 60 minutes. Initial manifestations may also vary widely. Classically, patients experience symptoms of central nervous system (CNS) excitement such as the following: Circumoral and/or tongue numbness, metallic taste, lightheadedness, dizziness, visual and auditory disturbances (difficulty focusing and tinnitus), disorientation and drowsiness.
Option A: Local anesthetic systemic toxicity (LAST) is a life-threatening adverse event associated with the increasingly prevalent utilization of local anesthetic (LA) techniques throughout various health care settings, with an incidence currently estimated to be 0.03% or 0.27 episodes per 1,000 peripheral nerve blocks.
Option B: Increasing plasma concentrations of LA initially compromises cortical inhibitory pathways by blockade of NaV channels, disrupting inhibitory neuron depolarization. Inhibiting these pathways leads to excitatory clinical features of sensory and visual changes, muscular activation, and subsequent seizure activity. As the plasma concentrations of LA rise, excitatory pathways are affected, producing a depressive phase of neurological toxicity, with loss of consciousness, coma, and respiratory arrest.
Option C: Prompt and effective airway management is crucial to prevent hypoxia, hypercapnia, and acidosis (metabolic or respiratory), which are known to potentiate LAST. The airway should be secured and 100% oxygen administered, bearing in mind that hyperventilation and respiratory alkalosis have also been demonstrated to be injurious.