What are side effects of a cannula during a myocardial perfusion scan using adenosine?

Clarify: I am not sure what is meant by a canula in this context.

Skin irritation: I assume you are talking about an IV cannula used to administer the tracer and adenosine. The side-effects are the same as they would be for anyone else getting a cannula: bruising and skin irritation being most common. Generally, the IV cannula itself, properly placed, causes no side-effects, and the primary side-effect is bruising from missed attempts trying to get the IV started.