What is the outcome when local anesthetic is injected intravascularly?

Injecting a local anesthetic intravascularly can lead to systemic toxicity, which is why this outcome is the correct choice. When a local anesthetic is inadvertently introduced directly into the bloodstream, it can achieve higher than intended systemic concentrations, resulting in potentially harmful effects on various body systems, particularly the cardiovascular and central nervous systems.

Systemic toxicity can manifest through a variety of symptoms, including cardiovascular complications such as arrhythmias or hypotension, as well as central nervous system effects like seizures, dizziness, or even loss of consciousness. This is a critical consideration during procedures, as the goal is to provide localized anesthesia without affecting overall systemic health.

The other options suggest that intravascular injection could somehow enhance the benefits of local anesthetic, such as increased effectiveness or prolonged numbness, which are not accurate in this context. Instead, the priority during anesthesia administration is to avoid intravascular injection to prevent such toxic outcomes.