Reduction of ischemia‐reperfusion syndrome after abdominal aortic aneurysmectomy by N‐acetylcysteine but not mannito1,2

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Abstract
Background:Abdominal aortic aneurysmectomy results in a general ischemia‐reperfusion syndrome accompanied by an acute rise in mean pulmonary artery pressure (MPAP). Severe and sometimes fatal postoperative cardiopulmonary complications have been described.Methods:This pilot study examined whether N‐acetyl‐cysteine (NAC), a precursor of the most important physiological antioxidant glutathione (reduced form: GSH; oxidized form: GSSG), or the hydroxyl radical scavenger mannitol (MAN) modifies these events. The patients received 150 mg/kg b.m. NAC (n=9) 30 minutes before infrarenal aortic clamping or 500 mg/kg b.m. MAN (n=10) 10 minutes before declamping. 11 patients had no additional treatment (control).Results:In the control group, a significant increase in plasma levels of oxidized glutathione and lipid peroxides was observed after declamping. Additionally, a significant increase in plasma levels of the stable metabolites of thromboxane (TXB2) and prostacyclin (6‐keto‐PGF1α) was measurable after declamping. There was a transient increase in MPAP and pulmonary vascular resistance (PVR), both of which returned to normal values within 20 minutes. Six hours after surgery, pulmonary dysfunction was manifest by increase in the intrapulmonary shunt fraction. Relative to the control group, NAC pretreatment led to a complete lack of changes in plasma lipid peroxide, thromboxane and prostacyclin levels after declamping; there was a significant increase in plasma GSH concentration persisting over a period of 12 hours. MPAP, PVR and Qs/QTvalues were unchanged. MAN pretreatment showed similar effects on the parameters obtained in the acute phase after declamping like the control group.Conclusions:Pretreatment with NAC, but not mannitol, may help prevent ischemia‐reperfusion syndrome following aortic clamping.