Methods: After extubation a blinded anesthetist performs eight clinical tests in 165 patients. Test results are correlated to calibrated electromyography train-of-four (TOF) ratio and to a postoperatively applied uncalibrated acceleromyography. A classification and regression tree (CART) is calculated developing the algorithm to identify PORC. This is validated against uncalibrated acceleromyography and tactile judgement of TOF fading in separate 100 patients.