Eighty patients , both genders , 20-70 years old , ASA I or II , for hemorrhoidectomy were randomly divided into two groups : Control ( n = 38 ) , epidural anesthesia with 14 mL of ropivacaine 0.75 % plus 0.0266 mL/kg of 0.9 % saline solution ; Experimental ( n = 42 ) epidural anesthesia with 14 mL of 0.75 % ropivacaine plus 4.0 mcg/kg of clonidine .