Sorry to hear of your son's medical difficulties. It seems autism can affect memory, sensory perception and movement because it prevents different parts of the brain working together to achieve complex tasks, but most by pass individuals are much older..
It is true there can be short-term confusion, memory loss, and poorer problem solving and information processing are common after bypass surgery, but are usually temporary and reversible. Most people return to their pre-bypass level of function between 3 and 12 weeks after surgery
Not every one is affected subsequent to a bypass, and if your son is affected it can be termporary. Your son is young and may have the physiological resillence better than the older individuals.
Thanks for sharing, and I wish the outcome is favorable for your son. Take care.