Figure 1. Patient State Index (PSI) and Modified Observer’s Assessment of Alertness/Sedation (MOAA/S) scale relationship are shown. A reduction of PSI value is correlated with the decreasing MOAA/S scale (r = 0.87667). Score of 5 of MOAA/S scale represents responds readily to name spoken in normal tone and score 0 represents no response to noxious stimuli.