Which of the following factors increases the risk of toxicity during a local anaesthetic injection?

Injecting in a vascular area significantly increases the risk of toxicity during a local anaesthetic injection. This is because when local anaesthetics are injected into highly vascular regions, they can be rapidly absorbed into the bloodstream. This quicker absorption means that the drug can reach systemic circulation in higher concentrations, potentially leading to overdose or toxicity.

In areas where blood vessels are abundant, such as near large arteries or veins, the chance of the anaesthetic entering the bloodstream directly is heightened. Consequently, the risk of widespread effects on the central nervous system and cardiovascular system increases, which could result in serious adverse effects, such as seizures, cardiac arrhythmias, or even cardiovascular collapse.

Other actions like injecting in a supine position or injecting gently and at a slower rate do not inherently increase risk. In fact, injecting gently and at a slower rate can often help minimize patient discomfort and reduce the risk of complications, including inadvertent vascular injection.