Reduced total antioxidant capacity predicts ischaemia–reperfusion injury after femorodistal bypass

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Abstract
Background: Antioxidant defence systems are essential to protect the body from harmful free radicals released following ischaemia–reperfusion. The aim of this study was to examine the total antioxidant capacity (TAC) of patients with chronic critical leg ischaemia undergoing femorodistal bypass and to correlate this with lipid peroxidation, changes in capillary permeability and clinical outcome. Methods: Twenty-five patients, 15 men and ten women of median age 71 (range 62–79) years, and 15 matched controls were studied. Blood was taken before operation and after reperfusion, with assays performed for malondialdehyde (a product of lipid peroxidation) and total antioxidant capacity. Changes in capillary permeability were measured by changes in the urinary albumin:creatinine ratio (ACR) following reperfusion of the ischaemic leg and expressed as a percentage increase from the preoperative value. Clinical outcome in terms of the systemic inflammatory response syndrome (SIRS) was recorded. Results: Vascular patients who developed clinical evidence of a systemic inflammatory reaction following revascularization had a significantly reduced TAC compared with the controls (490 versus 860 µmol/l; P < 0·01, Mann–Whitney U test). These patients also demonstrated an increase in lipid peroxidation (0·5 versus 0·25 µmol/l, P < 0·05) and vascular permeability, as measured by the percentage increase in ACR (365 versus 130 per cent, P < 0·01). Conclusion: Vascular patients with a lower TAC developed increased capillary permeability as a result of ischaemia–reperfusion, which progressed to SIRS. TAC may provide a test to identify ‘at risk’ patients. It may be possible to augment their defence with exogenous antioxidants.