Final answer:
The early signs of local anesthetic toxicity are primarily related to CNS excitation, such as muscle twitching and restlessness, and can progress to CNS depression and other severe conditions if not managed promptly.
Step-by-step explanation:
The early signs of local anesthetic toxicity are associated with central nervous system (CNS) excitation. This phase may present symptoms such as muscle twitching, restlessness, tinnitus, and even seizures before progressing to more severe signs like CNS depression or respiratory arrest. Local anesthetics work by blocking nerve conduction and can affect any part of the nervous system, hence depending on the dose and physiological response, they could lead to toxicity.
Increasing concentrations can lead to more severe symptoms eventually culminating in cardiac and respiratory arrest if not managed promptly. While cardiac arrest is a later manifestation, CNS excitation precedes CNS depression in the spectrum of local anesthetic systemic toxicity (LAST). It's important to recognize early signs of toxicity for immediate intervention to prevent progression to life-threatening complications.