Anesthesia was induced and maintained with sevoflurane in Group I and TIVA with propofol in Group T. Blood samples were obtained before the induction of anesthesia ( t1 ) , 30 min after tourniquet inflation ( t2 ) , immediately before ( t3 ) , and 5 min ( t4 ) , 15 min ( t5 ) , 30 min ( t 6 ) , 1 h ( t7 ) , 2 h ( t8 ) , and 6 h ( t9 ) after tourniquet release .