RESUMEN
Objective To compare the EEG complexity between rats under awaking and differ-ent depth of anesthesia via analyzing sample entropy and fractal dimension.Methods Sixteen SD rats were intraperitoneally injected with urethane twice,first with 500 mg/kg and second with 800 mg/kg one hour later.The scalp EEG was collected in stage of awaking (W),light anesthesia (LA)and heavy anesthesia (HA).The sample entropy (SampEn)and fractal dimension (FD)were computed by MATLAB.The characteristic values were denoised by linear dynamic system method during the whole process.Results The value of SampEn and FD gradually dropped from awaking to heavy anes-thesia.The SampEn and FD in W was significantly higher than the value in LA or in HA (P <0.05). The SampEn and FD in HA was significantly lower than that in LA (P < 0.05 ).Conclusion The SampEn and FD of EEG could be used to monitor the depth of anesthesia.