There are several reports indicating that analgesic and sedative agents routinely used in neonates may lead to amplitude depression on aEEG. However, to our knowledge there are currently no reports of aEEG studies and SWC in newborn infants requiring major non-cardiac surgery during the neonatal period. Studying background activity and emergence of SWC on aEEG in neonates requiring major non-cardiac surgery may provide useful information about the relationship of analgesia and sedation and cerebral function in the post-operative infant. Knowledge of the effects of drugs that may modify cerebral activity is important to the interpretation of aEEG's in critically ill neonates requiring high doses of analgesics and sedatives.