What is a common sign of local anaesthetic systemic toxicity?

The common sign of local anaesthetic systemic toxicity is agitation. When local anaesthetics enter the systemic circulation, they can affect the central nervous system (CNS). Early signs of CNS toxicity often manifest as agitation, which may progress to more severe symptoms such as confusion, seizures, and ultimately central nervous system depression. Agitation can result from the excitatory phase of this toxicity, where patients may display restlessness and heightened anxiety.

Although confusion can also be a symptom of systemic toxicity, it typically appears later in the course of toxicity after initial signs like agitation. Increased blood pressure may occur in some cases, but it's not the most characteristic or reliable sign; blood pressure responses can vary widely. Rapid heartbeat, or tachycardia, may occur as well, but again, agitation is one of the first and most consistent signs observed when local anaesthetic systemic toxicity develops.