Obviously sternotomy looks painful, but actually it may be much less than the distress caused by drains!
Also there is a high incidence of PONV after cardiac surgery and short term ileus (?opioids/shock) can be a complicating factor.(women more than men)
Pain from leg vein harvest sites becomes a real problem for some later on the ward.
Always always ask about any nerve injury pain components as chronic pain potential is huge.
Thoracic surgery is intimately linked to good analgesia, PCA, PVB, Epidural etc all need early and effective indivdualised care.