Anesthesia and postoperative cognitive dysfunction in the elderly: a review of clinical and epidemiological observations

Amnesic effects of anesthesia were first reported two hundred years ago, bu t the term postoperative cognitive dysfunction (POCD) has appeared only rec ently, covering a larger range of neuropsychological modifications resultin g from surgical intervention. The clinical description of POCD is highly va riable, ranging from concentration impairment to delirium. Significant shor t-term POCD is common in elderly persons, and can persist several months, v arying both in time and intensity and affecting the full-range of cognitive functions (visual and auditory attention, primary and secondary memory, im plicit memory, and visuospatial functioning). Incidence rates vary widely a ccording to surgery type but also between studies for a given surgical proc edure, as a result of methodological difficulties and limitations. Variabil ity is largely attributable to the absence of a standardized POCD definitio n, the heterogeneity of procedures to measure cognitive deficits and the me thods used for statistical analyses, but is also related to the disparity i n targeted populations. The wide variation in study design and target popul ations precludes the application of formal meta-analysis procedures. We rev iew the definition, epidemiology, etiology, pathophysiology and the clinica l and public health implications of POCD. The effects of anesthetics are de scribed in relation to ageing-related physiological changes. It is conclude d that the complex interaction of etiological factors makes it difficult to determine at this point of time to what extent POCD may be attributed spec ifically to anesthetic agents.