Upon the approval of institutional Ethics Committee and informed consent , forty patients ASAII or III aged 52-77 yr with BMI ( body mass index ) < 30 kg/m ( 2 ) , undergoing OPCABG , were randomly divided by random numbers into two groups ( n = 20 each ) : thoracic paravertebral block for postoperative analgesia group ( group P ) and patient-controlled intravenous analgesia ( PCIA ) group ( group I ) .