ABSTRACT
With the promotion of the concept of " precise anesthesia",it is important to achieve both the anesthetic effect and the avoidance of a series of side effects caused by overdose of anesthetic drugs in anesthesia management.How to determine the optimal dose of anesthetic drugs and maintain the appropriate depth of anesthesia has become a problem that anesthesiologists must focus on and urgently needs solving.First of all,maintaining adequate depth of anesthesia requires adequate sedation and analgesia.At present,there are many clinical monitoring methods for the depth of anesthesia (sedation and analgesia).Several tools,including bispectral index and entropy index,which have been proved to reflect the depth of sedation well,but they are not sensitive to noxious stimuli such as pain during surgery.This article reviews a recently developed method for monitoring surgical pleth index (SPI),and describes the research background,research principles,relevant influencing factors,and research progress in detail.