Postoperative Delirium
Introduction
Post operative delirium remains common, especially in older adults, with estimates of 10%-50% depending on the type of surgery. Previously this condition was thought to only impact the acute postoperative period, however evidence suggests it can have long term sequelae including longer hospitalization as well as cogitative decline [1][2]
Features
Delirium is defined as an acutely altered and fluctuating mental status with features of inattention and an altered level of consciousnesses, which can be divided into hypoactive, hyperactive, and mixed. Hypoactive delirium presents as lethargy, decreased alertness, loss of focus/attention and unawareness. Conversely, hyperactive delirium presents with a restless, irritable, combative, or agitated patient. The mixed type can have features of both hypoactive and hyperactive delirium that fluctuate with time. Post-operative delirium should be suspected following patient evaluation and only after ruling out other causes of altered mental status including infectious, metabolic, or toxic. See helpful pneumonic here.
Confusion Assessment Method-Intensive Care Unit (CAM-ICU)
The CAM-ICU assessment focuses on the evaluation of mental status, inattention, disorganized thinking, and an altered level of consciousness. Sedation is assessed with the Richmond Agitation and Sedation Score (RASS). An example calculation tool can be found here.
Risk Factors
Risk factors can be split into patient-specific vs surgical/operation specific.
The biggest patient-specific risk factors for development of post operative delirium include pre-existing dementia, older age, functional impairment, greater co-morbidities, and psychopathological symptoms. Pre-existing dementia appears to be the strongest predicting factor.
Operation-specific risk factors are generally related to the degree of operative stress. Low operative stress procedures such as cataract surgery result in 4% incidence vs high surgical risk procedures such as vascular operations which result in delirium in 36% of cases. [3]
Reducing Delirium
Depth/type of anesthesia
Data from the ICU demonstrates reduced delirium associated with a reduced level of sedation, however it is unclear if this association extends to the operating room.
A recent study comparing postoperative delirium between spinal anesthesia with sedation versus general anesthesia in patients undergoing spinal fusion. The depth of anesthesia was guided by bispectral index (BIS) values in both groups. Median BIS values in spinal group were 62 (53-70) versus 45 (41-50) in the GA group. Postoperative delirium incidence (measured by CAM) was not statistically different between the two groups (25% vs 18.9% respectively, P=.0259, RR=1.22 (95%CI .85-1.76)). [3] In summary, spinal anesthesia with BIS targeted sedation is not effective in reducing postoperative delirium in older adults following lumbar fusion. This study did not evaluate sedatives other than Propofol, such as dexmedetomidine.
Drug avoidance
Specific drugs are known to trigger or worsen delirium, most commonly associated drugs include anticholinergics and benzodiazepines.
Summary
Delirium remains a common, likely under recognized, and clinically relevant adverse event following anesthesia.
References
- ↑ Brown IV, C. H., Probert, J., Healy, R., Parish, M., Nomura, Y., Yamaguchi, A., ... & Hogue, C. W. (2018). Cognitive decline after delirium in patients undergoing cardiac surgery. Anesthesiology, 129(3), 406-416.
- ↑ Schubert M, Schürch R, Boettger S, Garcia Nuñez D, Schwarz U, Bettex D, Jenewein J, Bogdanovic J, Staehli ML, Spirig R, Rudiger A. A hospital-wide evaluation of delirium prevalence and outcomes in acute care patients - a cohort study. BMC Health Serv Res. 2018 Jul 13;18(1):550. doi: 10.1186/s12913-018-3345-x. PMID: 30005646; PMCID: PMC6045819.
- ↑ 3.0 3.1 Charles H. Brown, Charles Edwards, Charles Lin, Emily Ledford Jones, Lisa R. Yanek, Melody Esmaili, Yara Gorashi, Richard Skelton, Daniel Kaganov, Ryan Curto, Noah L. Lessing, Stephanie Cha, Elizabeth Colantuoni, Karin Neufeld, Frederick Sieber, Clayton L. Dean, Charles W. Hogue; Spinal Anesthesia with Targeted Sedation based on Bispectral Index Values Compared with General Anesthesia with Masked Bispectral Index Values to Reduce Delirium: The SHARP Randomized Controlled Trial. Anesthesiology 2021; 135:992–1003 doi: