REDUCTION OF ISCHEMIA-REPERFUSION SYNDROME AFTER ABDOMINAL AORTIC ANEURYSMECTOMY BY N-ACETYLCYSTEINE BUT NOT MANNITOL

Background: Abdominal aortic aneurysmectomy results in a general ische mia-reperfusion syndrome accompanied by an acute rise in mean pulmonar y artery pressure (MPAP). Severe and sometimes fatal postoperative car diopulmonary complications have been described. Methods: This pilot st udy examined whether N-acetyl-cysteine (NAC), a precursor of the most important physiological antioxidant glutathione (reduced form: GSH; ox idized form: GSSG), or the hydroxyl radical scavenger mannitol (MAN) m odifies these events. The patients received 150 mg/kg b.m. NAC (n=9) 3 0 minutes before infrarenal aortic clamping or 500 mg/kg b.m. MAN (n=1 0) 10 minutes before declamping. 11 patients had no additional treatme nt (control). Results: In the control group, a significant increase in plasma levels of oxidized glutathione and lipid peroxides was observe d after declamping. Additionally, a significant increase in plasma lev els of the stable metabolites of thromboxane (TXB(2)) and prostacyclin (6-keto-PGF(1 alpha)) was measurable after declamping. There was a tr ansient 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 intrap ulmonary shunt fraction. Relative to the control group, NAC pretreatme nt led to a complete lack of changes in plasma lipid peroxide, thrombo xane and prostacyclin levels after declamping; there was a significant increase in plasma GSH concentration persisting over a period of 12 h ours. MPAP, PVR and Q(S)/Q(T) values were unchanged. MAN pretreatment showed similar effects on the parameters obtained in the acute phase a fter declamping like the control group. Conclusions: Pretreatment with NAG, but not mannitol, may help prevent ischemia-reperfusion syndrome following aortic clamping.