The aim of the article is to review the latest progresses in the research of postoperative cognitive dysfunction (POCD) after cardiac and noncardiac surgery in elderly patients.
While it is not yet possible to provide definite answers to some questions regarding POCD and additional work is required before a complete understanding of the mechanisms involved, we investigate the definition criteria for POCD, its incidence, medical complications and the social impact of POCD following anaesthesia and surgery. The article also reviews the POCD risk factors and the recent advances in identifying specific POCD biomarkers as well as the vulnerable cognitive areas of POCD and the neuropsychological instruments most frequently used to define and to survey the long-term follow-up of POCD.
Keywords: cognitive dysfunction, neuropsychological tests, elderly
Postoperative cognitive dysfunction (POCD) in the elderly patient is an unwanted complication of the postoperative period, relatively frequent and most of the time underestimated. POCD is particularly characterized, but not only, by the alteration of memory and concentration performances. It is, for the time being, only detectable through the usage of neuropsychological tests (Rasmussen et al. 2003).
Although it was described more than 50 years ago by Bedford (1955) and largely debated within various seminars and conferences, POCD remains a puzzle awaiting an answer. There are some major questions that we are trying to answer in the present article, reviewing some of the most relevant papers published on the topic: 1. Is POCD induced by a certain type of surgical interventions or by the anesthetic technique?; 2. Are there any risk factors which are specific to POCD development?; 3. Which areas of cognition are particularly affected within the POCD?; 4. Is there any genetic context which can favor or which can be related with a higher incidence of POCD?; 5. Are there any biological markers of diagnostic value in POCD?; 6. Which is the duration of POCD and to what extent is the quality of life of POCD patients affected?; 7. Which are the most appropriate instruments and neuropsychological tests to evaluate the postoperative cognitive decline?
Many of the published studies that relate to this topic are descriptive, involving relatively small groups of patients, without control groups and the conclusions are sometimes speculative.
We reviewed (no time limit, up to January 2008) the main medical English language databases, i.e. Embase, Medline, Cochrane Library, MD Consult and PsycInfo, the keywords being: POCD, anesth*, anaesth*, postoperat*, surg*, and cerebral dysfunction, neurocognitive, neuropschycholog*, neurobehaviour*, quality of life. We used the same inclusion criteria like the ones of the recent review of Newman et al. (2001): a. patients undergoing cardiac and non-cardiac surgery; b. the evaluation of the cognitive function after more than 7 days, postoperatively (to differentiate the POCD by a postoperative delirium and to minimize the influence of the residual effect of the neurodepressive perioperative medication). Carotid vascular reconstructive surgery was used as an exclusion criterion. A number of 38 studies have been identified which met the above mentioned criteria. Out of these, 21 are cohort studies, divided as follows: 8 studies without control group, with the POCD evaluated as compared to preoperative status; 13 studies with control group. The remaining 17 studies (most of them randomized) compared groups of patients undergoing different anesthetic techniques (general, regional, local or other) for major or minor surgical procedures.
The POCD definition should start with a clear differentiation between POCD and postoperative delirium. The postoperative delirium is a fluctuant and transitory alteration of consciousness, developed within the immediate postoperative period; the diagnosis of POCD can only be established in the later postoperative period and the cognitive decline has an insidious and slower onset, requiring evaluation through neurocognitive tests (Bryson et al. …