Overview

Postoperative cognitive dysfunction refers to a persistent cognitive dysfunction that occurs subsequent to surgery and anesthesia that is beyond postoperative delirium, a transient state of cognitive change. Until recently, the majority of research on postoperative cognitive dysfunction has focused on cardiac surgery. However, emerging evidence has found the presence of postoperative cognitive dysfunction after major non-cardiac surgery (1). The cause of postoperative cognitive dysfunction is unknown due to the heterogeneity of this population. However, people of older age and who have a history of brain insults such as stroke or trauma are at higher risk of developing postoperative cognitive dysfunction. There is currently no standard treatment for postoperative cognitive dysfunction. Pharmacologic and behavioral solutions for other neurological conditions may be helpful, although their efficacy in this population has yet to be studied.

Symptoms

Cognitive deficits associated with postoperative cognitive dysfunction include difficulty with learning and memory, attention, mental processing speed, language comprehension, and executive functioning (e.g., reasoning, planning/organizing, and problem solving) (2,3).

Prevalence and Risk Factors

The cause of postoperative cognitive dysfunction is not well understood; however, certain populations have a greater risk of developing postoperative cognitive dysfunction. Older individuals are more likely to have postoperative cognitive dysfunction, occurring in 10-54% of cases. The greatest incidence of postoperative cognitive dysfunction is among patients who underwent cardiopulmonary bypass surgery (53% at hospital discharge and 36%, 24%, and 42% at 6 weeks, 6 months, and 5 years post-surgery, respectively), which may be caused by decreased blood flow and small blood clots (4).

Other risk factors for postoperative cognitive dysfunction include lower level of education, history of stroke without enduring impairment, history of alcohol abuse, history of brain trauma (even without symptoms), preoperative cognitive impairment, and postoperative delirium (3,5). Given the links between postoperative cognitive dysfunction and education and preoperative cognitive/neurological functioning, Postoperative cognitive dysfunction may be related to lower cognitive reserve, or ability to buffer against aging and disease pathology (6). Research has shown that there is no significant difference in the development of postoperative cognitive dysfunction between those who received general and regional anesthesia (5,7). However, some studies have linked inhalational anesthetic agents (used in general anesthesia) with increased Alzheimer’s disease pathology (3). Interestingly, low oxygen supply and hypotension do not predict the incidence of postoperative cognitive dysfunction (8).

Course

The evidence for postoperative cognitive dysfunction one week after major non-cardiac surgery is clear, but only a few studies has demonstrated the presence of postoperative cognitive dysfunction 22 to 132 days after surgery (Newman et al., 2007). Most patients recover three months after surgery; however postoperative cognitive dysfunction can persist in some individuals (2,9). Studies linking postoperative cognitive dysfunction and mortality are mixed, with some studies finding increased mortality rates and others finding no such association (2,10).

Treatments

There is currently no standard treatment for postoperative cognitive dysfunction. Anti-inflammatory medications and cognitive remediation may ameliorate the cognitive symptoms of postoperative cognitive dysfunction, but the utility of these treatments has not been examined in this population (2).

Limitations of Research

Of note, there are various methodological issues with postoperative cognitive dysfunction studies. The definitions of postoperative cognitive dysfunction, type/range of assessment, types of surgery and anesthesia, presence/type of a control group, and mode of analysis vary among studies (1). Many investigations also have insufficient sample sizes and lack neurological examinations to complement the neuropsychological assessment (5). It is also possible that postoperative cognitive dysfunction is related to generalized illness (cause for surgery), rather than the surgery itself (1).

By Michelle Chen

References

  1. Newman, S, Stygall, J, Hirani, S, Shaefi, S, & Maze, M (2007). Postoperative Cognitive Dysfunction after Noncardiac SurgeryA Systematic Review. Anesthesiology: The Journal of the American Society of Anesthesiologists106(3), 572-590.
  2. Grape, S, Ravussin, P, Rossi, A, Kern, C, & Steiner, L (2012). Postoperative cognitive dysfunction. Trends in Anaesthesia and Critical Care2(3), 98-103. Newfield, P. (2009). Postoperative cognitive dysfunction. F1000 medicine reports,
  3. Monk, T, & Price, C (2011). Postoperative cognitive disorders. Current opinion in critical care17(4).
  4. Hanning, C (2005). Postoperative cognitive dysfunction. British journal of anaesthesia95(1), 82-87.
  5. Newfield, P (2009). Postoperative cognitive dysfunction. F1000 medicine reports1.
  6. Feinkohl, I, Winterer, G, Spies, C, & Pischon, T (2017). Cognitive reserve and the risk of postoperative cognitive dysfunction: a systematic review and meta-analysis. Deutsches Aerzteblatt International114(7), 110.Monk, T. G., & Price, C. C. (2011). Postoperative cognitive disorders. Current opinion in critical care17(4), 110-117.
  7. Rasmussen, L, Johnson, T, Kuipers, H, Kristensen, D, Siersma, V, Vila, P, & Bonal, J (2003). Does anaesthesia cause postoperative cognitive dysfunction? A randomised study of regional versus general anaesthesia in 438 elderly patients. Acta Anaesthesiologica Scandinavica47(3), 260-266.
  8. Moller, J, Cluitmans, P, Rasmussen, L, Houx, P, Rasmussen, H, Canet, J & Langeron, O (1998). Long-term postoperative cognitive dysfunction in the elderly: ISpostoperative cognitive dysfunction1 study. The Lancet351(9106), 857-861.
  9. Johnson, T, Monk, T, Rasmussen, L, Abildstrom, H, Houx, P, Korttila, K, & Canet, J (2002). Postoperative cognitive dysfunction in middle-aged patients. The Journal of the American Society of Anesthesiologists96(6), 1351-1357.
  10. Steinmetz, J, Christensen, K, Lund, T, Lohse, N, & Rasmussen, L (2009). Long-term consequences of postoperative cognitive dysfunction. The Journal of the American Society of Anesthesiologists110(3), 548-555.