Hi Darun,

            During cardiac surgery, the surgeon needs to works on a still heart so it is necessary to give the patient artificial circulatory and respiratory function. It is the perfusionist's responsibility to operate the heart-lung machine, which is an artificial blood pump, that circulates oxygenated blood while the surgeon operates on the patient's heart. It's also the Perfusionist's responsibility to deliver the drug that stops the heart and also the perfusionist is responsible for managing physiological and metabolical demands of the patient's body while the surgeon operates on the patient's heart. The perfusionist measures various parameters to analyze the appropriate mechanical and pharmacological manipulation to maintain physiological state. Hence a perfusionist must have an in-depth knowledge of both respiratory and circulatory systems and also have good knowledge of operating complex types of equipment. 

So if there are no perfusionist's there'll be a little lag in cardiac surgeries and also lack of professionals with good knowledge in the perfusion procedure.

I hope this helps you.