title: The role of preconditioning and N-acetylcysteine on oxidative stress resulting from tourniquet-induced ischemia-reperfusion in arthroscopic knee surgery.
abstract: BACKGROUND
  The aim of this study was to investigate the effects of ischemic preconditioning (IPC) and N-acetylcysteine (NAC) on oxidative stress resulting from tourniquet-induced ischemia-reperfusion (IR) period in arthroscopic knee surgery.
  
  
  METHODS
  Forty-five patients who had arthroscopic knee surgery for meniscal and chondral lesions and for pathologic medial plica were included in this study. They were assigned to the following treatment groups: control (group C; n=15), IPC (group P; n=15), and NAC (group N; n=15). Subjects in the control group underwent routine surgical procedures. Subjects in the preconditioning group were subjected to temporary ischemia, with tourniquet performed by three compression cycles of 5 minutes followed by 5 minutes of reperfusion just before the application of tourniquet inflation. Subjects in the NAC group received 10 mg/kg NAC dissolved in 100 mL 0.9% normal saline intravenously 30 minutes before tourniquet inflation. An hour before the tourniquet was applied (preischemia) and 2 hours after tourniquet was removed (reperfusion), blood samples (to test for metabolites) were obtained. Levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), total antioxidant capacity (TAC), and total oxidant status (TOS) were measured in all serum samples. Results were compared between preischemia and reperfusion in three groups.
  
  
  RESULTS
  MDA in the control group was found to be increased significantly compared with preischemia, whereas MDA in IPC and NAC groups did not change insignificantly. SOD and GSH activities in the control group were found to be increased significantly, whereas SOD and GSH activities in IPC and NAC groups did not change significantly after reperfusion. TAC in the control group was found to be decreased and TOS was found to be increased significantly, but TAC and TOS in IPC and NAC groups were not significantly different after reperfusion. Mean serum MDA, TOS, SOD, and GSH-Px levels were lower in group P than group C at reperfusion period (p<0.05). Mean serum SOD levels were lower in group P than group N at reperfusion period (p<0.05).
  
  
  CONCLUSIONS
  Tourniquet-induced IR period in routine arthroscopic knee surgery resulted in oxidative stress by increasing MDA, SOD, GSH-Px, TOS and decreasing TAC. NAC and IPC had protective effect on occurrence of oxidative stress resulting from IR period by preventing MDA, SOD, GSH-Px, TAC, and TOS changes in routine arthroscopic knee surgery.
authors: Department of Orthopedic Surgery, Gulhane Military Medical Academy, Etlik-Ankara 06300, Turkey. drkenankoca@yahoo.com
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