Effects of surgical stress and nitrous oxide anaesthesia on peri-operativeplasma levels of total homocysteine - A randomised, controlled study in general surgery

Previous studies of patients have shown that anaesthesia with nitrous oxide (N2O) increases the plasma levels of total homocysteine. In a randomised, controlled trial we measured the plasma total homocysteine levels in patien ts undergoing general surgery before and after anaesthesia with and without N2O. Plasma total homocysteine levels were measured before anaesthesia and 1, 3-5 and 24 h after incision in 24 patients randomly allocated to anaest hesia with N2O (n = 12) and without N2O (n = 12). Total homocysteine levels significantly decreased from 10.4 +/- 2.7 to 8.2 +/- 2.9 mu mol.l(-1) in t he non-N2O group 24 h after incision (p < 0.02), while they tended to incre ase slightly in the N2O group from 10.5 +/- 4.5 to 10.9 +/- 4.3 <mu>mol.l(- 1) (p > 0.05). Our randomised controlled study indicates that total homocys teine decreases after general surgery in patients in whom anaesthesia is ma intained without N2O, but not in patients in whom anaesthesia is maintained with N2O.