Association between the spontaneous TOF ratio recovery rate and the late-phase TOF ratio change rate in response to low-dose sugammadex. The quality of the correlation was calculated for all 40 patients: 20 nonelderly (black circles) and 20 elderly (red circles) patients. Recurarization defined as negative values of the late-phase TOF ratio change rate occurred in one nonelderly patient and seven elderly patients. TOF, train-of-four.