The effects of propofol or halothane on free radical production after tourniquet induced ischaemia-reperfusion injury during knee arthroplasty

Background: Ischaemia-reperfusion injury following tourniquet release is a good in vivo model for evaluating acute conditions. The aim of the study wa s to investigate the effects of propofol or halothane anaesthesia on oxidat ive stress by determining malondialdehyde (MDA) levels during knee arthropl asty. Methods: Thirty patients undergoing orthopaedic surgery were divided into t wo groups. Anaesthesia was induced with either fentanyl 100 mug and propofo l 2 mg kg(-1) (Group 1) or fentanyl 100 mug and thiopentone 5 mg kg(-1) (Gr oup 2) and maintained with infusion of propofol in Group 1 or inhalation of halothane in Group 2. ECG, SpO(2), EtCO2, and mean arterial pressure (MAP) were monitored. Venous and arterial blood samples were obtained at differe nt measurement times for MDA and blood gas analyses. Results: There was a significant decrease in MAP in the 1(st) and 5(th) min utes after tourniquet release (ATR) when compared with the 5(th) minute bef ore tourniquet release (BTR) in both groups. Heart rate (HR) increased sign ificantly in the 1(st) minute ATR in Group 1 only. EtCO2 increased signific antly in the 1(st) and 5(th) minutes ATR, SpO(2) decreased in the 1(st) min ute ATR vri both groups. There was a significant decrease in pH and increas e in pCO(2) at 1, 5; and 30 min ATR in both groups. pO(2) values decreased in the 1(st) minute ATR in Group 1 only and returned to control values at 5 min ATR and decreased at 30 min ATR in the recovery room in both groups. T he differences in SaO(2) were similar to SpO(2). MDA levels decreased befor e and after release of tourniquet when compared to baseline in both groups. However, there was a statistically significant decrease only in Group 1. Conclusion: Propofol may be a good choice of anaesthetic when an ischaemia- reperfusion injury is anticipated as in orthopaedic surgery requiring a tou rniquet, due to its antioxidant properties, but halothane needs further stu dy.