N. Dover

Background: Postoperative delirium, an acute manifestation of delirium occurring after anesthesia, presents variably in terms of symptoms and timing of onset.^1,2,3,8 Like classical delirium, postoperative delirium may include symptoms such as disorganized thinking, general confusion, and fluctuating mental status.⁸ Importantly, it is associated with increased mortality, prolonged hospital stays, and potential long-term cognitive decline, similar to that observed in dementia.⁷ Despite these significant impacts, the underlying mechanisms of postoperative delirium remain poorly understood.⁸ While the etiology of the disease remains unclear, known predisposing factors include advanced age and existing comorbidities.⁷ This study aims to assess the likelihood that perioperative risk factors contribute to the onset of postoperative delirium.

Methods: A database search in PubMed was performed including the terms: “Postoperative Delirium,” “Postoperative Delirium Risk Factors,” and “Postoperative Delirium Incidence.”

Results: No statistical significance was found in the outcome of postoperative delirium between general and regional anesthesia or between an IV versus an epidural route of delivery.^1,5 However, researchers found that postoperative delirium occurred at a rate of 41% with the use of fentanyl, and other studies have tied the use of both opiates and benzodiazepines to a high incidence of postoperative delirium.^5,3 Similarly, deep anesthetics have been shown to cause postoperative delirium at a statistically significant higher rate (28% of cases) than do light anesthetics (19% of cases).² Another  study including children aged 3-7 who were shown a breathing technique video preoperatively demonstrated a significantly reduce incidence of postoperative delirium.⁴ Finally, a Chinese study notes that patients enrolled in a Family-Involved Hospital Elder Life Program had a postoperative delirium rate of 2.6% compared to the 19.4% in the standard care group.¹

Conclusions: Despite extensive research, the true cause of postoperative delirium largely remains a mystery.^1,2,3 However, several risk factors have been identified, such as old age, other comorbidities, or electrolyte imbalances.⁷ Additionally, certain classes and combinations of drugs are known to increase the risk of postoperative delirium at higher rates, such as opioids and benzodiazepine.³ Furthermore, other studies found social structure factors to play a role in decreasing the incidence of the disease, such as access to family care or a preoperative controlled breathing technique video.^1,4 Further studies analyzing the role of social structures on the prevention of this disease hold the potential to both reduce postoperative delirium and further clarify the underlying mechanism.

Works Cited:

1.  Li T, Li J, Yuan L, et al. Effect of Regional vs General Anesthesia on Incidence of Postoperative Delirium in Older Patients Undergoing Hip Fracture Surgery: The RAGA Randomized Trial [published correction appears in JAMA. 2022 Mar 22;327(12):1188]. JAMA. 2022;327(1):50-58. doi:10.1001/jama.2021.22647
2. Evered LA, Chan MTV, Han R, et al. Anaesthetic depth and delirium after major surgery: a randomised clinical trial. Br J Anaesth. 2021;127(5):704-712. doi:10.1016/j.bja.2021.07.021
3. Shin HJ, Woo Nam S, Kim H, et al. Postoperative Delirium after Dexmedetomidine versus Propofol Sedation in Healthy Older Adults Undergoing Orthopedic Lower Limb Surgery with Spinal Anesthesia: A Randomized Controlled Trial [published correction appears in Anesthesiology. 2023 Apr 1;138(4):456]. Anesthesiology. 2023;138(2):164-171. doi:10.1097/ALN.0000000000004438
4. Zhang LN, Liu Y, Guo QQ, et al. Pre-operative breathing training based on video learning reduces emergence delirium in preschool children: A randomized clinical trial. J Clin Anesth. 2022;79:110788. doi:10.1016/j.jclinane.2022.110788
5. Williams-Russo P, Urquhart BL, Sharrock NE, Charlson ME. Post-operative delirium: predictors and prognosis in elderly orthopedic patients. J Am Geriatr Soc. 1992;40(8):759-767. doi:10.1111/j.1532-5415.1992.tb01846.x
6. Chen H, Mo L, Hu H, Ou Y, Luo J. Risk factors of postoperative delirium after cardiac surgery: a meta-analysis. J Cardiothorac Surg. 2021;16(1):113. Published 2021 Apr 26. doi:10.1186/s13019-021-01496-w
7.  Bramley P, McArthur K, Blayney A, McCullagh I. Risk factors for postoperative delirium: An umbrella review of systematic reviews. Int J Surg. 2021;93:106063. doi:10.1016/j.ijsu.2021.106063
8. Oh ST, Park JY. Postoperative delirium. Korean J Anesthesiol. 2019;72(1):4-12. doi:10.4097/kja.d.18.00073.
9. Xiao MZ, Liu CX, Zhou LG, Yang Y, Wang Y. Postoperative delirium, neuroinflammation, and influencing factors of postoperative delirium: A review. Medicine (Baltimore). 2023;102(8):e32991. doi:10.1097/MD.0000000000032991