Abstract
Introduction
Medicines acting on the central nervous system can increase the risk of postoperative delirium, but the specific medicines associated with greatest risk remain unclear.
Objectives
We aimed to examine the risk of individual central nervous system-acting medicines used preoperatively on delirium after hip or knee surgery.
Methods
A matched case-control study was conducted using data from the Australian Government Department of Veterans’ Affairs. We included people aged 65 years or older who had knee or hip surgery between 2000 and 2019. People with hip or knee surgery who developed postoperative delirium were cases and controls were people with hip or knee surgery but who did not develop postoperative delirium. Use of medicines including anxiolytics, sedatives, and hypnotics, opioid analgesics and antidepressants prior to surgery was compared between cases and controls.
Results
A total of 2614 patient cases with postoperative delirium were matched by same sex, age (±2 years), and year of admission (±2 years) with 7842 controls without postoperative delirium. Cases were more likely to be exposed to nitrazepam (odds ratio [OR] = 1.81, 95% confidence interval [CI] 1.24–2.64), sertraline (OR = 1.50, 95% CI 1.20–1.87), mirtazapine (OR = 1.38, 95% CI 1.11–1.74), venlafaxine (OR = 1.42, 95% CI 1.02–1.98), citalopram (OR = 1.54, 95% CI 1.19–1.99), escitalopram (OR = 1.42, 95% CI 1.06–1.89) or fluvoxamine (OR = 5.01, 95% CI 2.15–11.68) prior to surgery than controls. At the class level, exposure to benzodiazepines (OR = 1.20, 95% CI 1.05–1.37) and antidepressants (OR = 1.64, 95% CI 1.47–1.83) prior to surgery was significantly higher in cases than in controls. The numbers needed to treat to harm for one additional delirium case were 43 for sertraline, 40 for citalopram, 57 for mirtazapine and 26 for nitrazepam. Whereas, the numbers needed to treat to harm were found to be 20 for sertraline, 17 for citalopram, 19 for mirtazapine and 10 for nitrazepam in the 85 years or older age group, indicating that the harmful effect of these medicines is pronounced as age advances.
Conclusions
People who developed delirium following hip or knee surgery were more likely to be exposed to nitrazepam, sertraline, mirtazapine, venlafaxine, citalopram, escitalopram or fluvoxamine at the time of admission for surgery. Planning to reduce use of these medicines well prior to surgery may decrease the risk of postoperative delirium.
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References
Bruce AJ, Ritchie CW, Blizard R, et al. The incidence of delirium associated with orthopedic surgery: a meta-analytic review. Int Psychogeriatr. 2007;19(2):197.
Santos FS, Wahlund LO, Varli F, et al. Incidence, clinical features and subtypes of delirium in elderly patients treated for hip fractures. Dement Geriatr Cogn Disord. 2005;20(4):231–7.
Wang C-G, Qin Y-F, Wan X, et al. Incidence and risk factors of postoperative delirium in the elderly patients with hip fracture. J Orthop Surg Res. 2018;13(1):1–7.
Aldwikat RK, Manias E, Nicholson P. Incidence and risk factors for acute delirium in older patients with a hip fracture: a retrospective cohort study. Nurs Health Sci. 2020;22(4):958–66.
Ozbas A, Ak ES, Cavdar I, et al. Determining the incidence of postoperative delirium in elderly patients who undergo orthopaedic surgical interventions in Turkey. JPMA. 2018;68(6):867–71.
Lee K-H, Ha Y-C, Lee Y-K, et al. Frequency, risk factors, and prognosis of prolonged delirium in elderly patients after hip fracture surgery. Clin Orthopaed Relat Res. 2011;469(9):2612–20.
Mangusan RF, Hooper V, Denslow SA, et al. Outcomes associated with postoperative delirium after cardiac surgery. Am J Crit Care. 2015;24(2):156–63.
Mitchell R, Harvey L, Brodaty H, et al. One-year mortality after hip fracture in older individuals: the effects of delirium and dementia. Arch Gerontol Geriatr. 2017;72:135–41.
Liang C-K, Chu C-L, Chou M-Y, et al. Interrelationship of postoperative delirium and cognitive impairment and their impact on the functional status in older patients undergoing orthopaedic surgery: a prospective cohort study. PLoS ONE. 2014;9(11):e110339.
Benoit AG, Campbell BI, Tanner JR, et al. Risk factors and prevalence of perioperative cognitive dysfunction in abdominal aneurysm patients. J Vasc Surg. 2005;42(5):884–90.
Catic AG. Identification and management of in-hospital drug-induced delirium in older patients. Drugs Aging. 2011;28(9):737–48.
Clegg A, Young JB. Which medications to avoid in people at risk of delirium: a systematic review. Age Ageing. 2011;40(1):23–9.
Hein C, Forgues A, Piau A, Sommet A, Vellas B, Nourhashémi F. Impact of polypharmacy on occurrence of delirium in elderly emergency patients. J Am Med Dir Assoc. 2014;15(11):850.e11-5.
Kassie GM, Nguyen TA, Ellett LMK, et al. Preoperative medication use and postoperative delirium: a systematic review. BMC Geriatr. 2017;17(1):1–10.
Litaker D, Locala J, Franco K, et al. Preoperative risk factors for postoperative delirium. Gen Hosp Psychiatry. 2001;23(2):84–9.
Marcantonio ER, Juarez G, Goldman L, et al. The relationship of postoperative delirium with psychoactive medications. JAMA. 1994;272(19):1518–22.
Australian Government Department of Veterans’ Affairs D. Stats at a glance 2019. https://www.dva.gov.au/about-dva/statistics-about-veteran-population#ataglance. Accessed 14 Jan 2019.
World Health Organization Collaborating Centre for Drug Statistics Methodology. Anatomical Therapeutic Chemical Code Classification Index with Defined Daily Doses. Oslo: World Health Organization Collaborating Centre for Drug Statistics Methodology, 2004 [on-line]. Available at https://www.whocc.no/atc_ddd_index/. Accessed 22 Feb 2019.
Australian Government Department of Health. Schedule of Pharmaceutical Benefits: Commonwealth of Australia; 2020. http://www.pbs.gov.au/browse/publications. Accessed 9 June 2020.
World Health Organization. International statistical classification of diseases and related health problems: 10th revision (ICD-10). Available from: http://www.who.int/classifications/apps/icd/icd1992. Accessed 28 Feb 2019.
Pottegård A, Hallas J. Assigning exposure duration to single prescriptions by use of the waiting time distribution. Pharmacoepidemiol Drug Saf. 2013;22(8):803–9.
Hallas J. Drug utilization statistics for individual-level pharmacy dispensing data. Pharmacoepidemiol Drug Saf. 2005;14(7):455–63.
Australian Bureau of Statistics. Census of Population and Housing: Socio‐Economic Indexes for Areas (SEIFA), Australia, 2016. https://www.abs.gov.au/websitedbs/censushome.nsf/home/seifa. Accessed 2 Nov 2021.
Pratt NL, Kerr M, Barratt JD, et al. The validity of the Rx-risk Comorbidity Index using medicines mapped to the Anatomical Therapeutic Chemical (ATC) classification system. BMJ Open. 2018;8(4):e021122.
Menendez ME, Neuhaus V, van Dijk CN, Ring D. The Elixhauser comorbidity method outperforms the Charlson Index in predicting inpatient death after orthopaedic surgery. Clin Orthopaed Relat Res. 2014;472(9):2878–86.
Bjerre LM, LeLorier J. Expressing the magnitude of adverse effects in case-control studies:“the number of patients needed to be treated for one additional patient to be harmed.” BMJ. 2000;320(7233):503–6.
Maldonado JR. Acute brain failure: pathophysiology, diagnosis, management, and sequelae of delirium. Crit Care Clin. 2017;33(3):461–519.
Kudoh A, Takase H, Takahira Y, et al. Postoperative confusion increases in elderly long-term benzodiazepine users. Anesth Analg. 2004;99(6):1674–8.
Nandi S, Harvey WF, Saillant J, et al. Pharmacologic risk factors for post-operative delirium in total joint arthroplasty patients: a case-control study. J Arthroplasty. 2014;29(2):268–71.
Carpenter CR. Insufficient evidence exists about which drugs are associated with delirium; benzodiazepines may increase risk. Ann Intern Med. 2011;154(24):JC6-10.
Grundström R, Holmberg G, Hansen T. Degree of sedation obtained with various doses of diazepam and nitrazepam. Acta Pharmacol Toxicol. 1978;43(1):13–8.
Pandharipande P, Shintani A, Peterson J, et al. Lorazepam is an independent risk factor for transitioning to delirium in intensive care unit patients. J Am Soc Anesthesiol. 2006;104(1):21–6.
Zaal IJ, Devlin JW, Hazelbag M, et al. Benzodiazepine-associated delirium in critically ill adults. Intensive Care Med. 2015;41(12):2130–7.
Behrends M, DePalma G, Sands L, et al. Association between intraoperative blood transfusions and early postoperative delirium in older adults. J Am Geriatr Soc. 2013;61(3):365–70.
Xue P, Wu Z, Wang K, et al. Incidence and risk factors of postoperative delirium in elderly patients undergoing transurethral resection of prostate: a prospective cohort study. Neuropsychiatr Dis Treat. 2016;12:137.
Huang J, Bin Abd Razak HR, Yeo SJ. Incidence of postoperative delirium in patients undergoing total knee arthroplasty: an Asian perspective. Ann Transl Med. 2017;5(16):321.
Gustafson Y, Berggren D, Brännström B, et al. Acute confusional states in elderly patients treated for femoral neck fracture. J Am Geriatr Soc. 1988;36(6):525–30.
Delić M, Pregelj P. Delirium during i.v. citalopram treatment: a case report. Pharmacopsychiatry. 2013;46(01):37–8.
Wakeno M, Okugawa G, Takekita Y, et al. Delirium associated with paroxetine in an elderly depressive patient: a case report. Pharmacopsychiatry. 2007;40(05):199–200.
Brown CH IV, LaFlam A, Max L, et al. Delirium after spine surgery in older adults: incidence, risk factors, and outcomes. J Am Geriatr Soc. 2016;64(10):2101–8.
Lejoyeux M, Adès J, Mourad S, et al. Antidepressant withdrawal syndrome. CNS Drugs. 1996;5(4):278–92.
Van Noorden M, Vergouwen A, Koerselman G. Delirium during withdrawal of venlafaxine. Ned Tijdschr Geneeskd. 2002;146(26):1236–7.
Oldham MA, Hawkins KA, Lin I-H, et al. Depression predicts delirium after coronary artery bypass graft surgery independent of cognitive impairment and cerebrovascular disease: an analysis of the neuropsychiatric outcomes after heart surgery study. J Am Geriatr Soc. 2019;27(5):476–86.
Elsamadicy AA, Adogwa O, Lydon E, et al. Depression as an independent predictor of postoperative delirium in spine deformity patients undergoing elective spine surgery. J Neurosurg Spine. 2017;27(2):209–14.
Pisani MA, Murphy TE, Araujo KL, et al. Benzodiazepine and opioid use and the duration of ICU delirium in an older population. Crit Care Med. 2009;37(1):177.
Acknowledgements
This research was funded by the Australian Government Department of Veterans’ Affairs as part of the delivery of the Veterans’ MATES program.
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Ethics approval was obtained from the University of South Australia, and the Departments of Defence and Veterans’ Affairs Human Research Ethics Committees.
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This observational study was based on administrative claims data and did not require patient consent. Patients and/or the public were not involved.
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GMK: study design, data analysis and interpretation and drafting of the manuscript. EER, TAN, NLP, and LMKE: study design, data interpretation and critical revision of the manuscript for important intellectual content. All authors read and approved the final version of this article.
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Kassie, G., Roughead, E.E., Nguyen, T.A. et al. The Risk of Preoperative Central Nervous System-Acting Medications on Delirium Following Hip or Knee Surgery: A Matched Case-Control Study. Drug Saf 45, 75–82 (2022). https://doi.org/10.1007/s40264-021-01136-1
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DOI: https://doi.org/10.1007/s40264-021-01136-1