GSTM1 and anemia: In conclusion, while our results do not confirm preoperative anaemia as a risk factor for the development of PSII, we were able to show that intraoperative Hb trend as an indicator of intraoperative blood loss is a predictor of an increased risk for the development of PSII independent of the amount of blood transfusions, operation time, number of spinal levels operated on and hospital length of stay.