Efficacy of brief preoperative cognitive screening using animal fluency test and six-item screener for prediction of postoperative delirium in elderly undergoing orthopedic surgery; a prospective observational study

Baseline cognitive impairment is one of the most significant risk factors for the development of postoperative delirium and neurocognitive disorders in older adults. Preexisting cognitive impairment is both a risk factor and a predictor and/or modifier of postoperative outcomes. Despite this preoperative cognitive screening is inconsistently performed in elderly surgical patients.

Most of the standard bedside screening tests are too time-consuming to be practical in a preoperative evaluation clinic, where daily visit volume is high, and each patient often needs evaluation of multiple organ systems. The challenge, therefore, is to identify a cognitive assessment instrument that is brief, easily administered, and scored. Also, the performance on many of the tests is known to be affected by the education level (not suitable for those who are illiterate or those with low levels of literacy). Hence, there is a need for the exploration of alternative cognitive screening tests for Indian older surgical patients.

We wish to conduct a prospective observational study to assess the association of preoperative cognitive screening tests for predicting postoperative delirium in elderly surgical patients with the primary objective to evaluate and compare the association of animal fluency test and six-item screener with postoperative delirium in patients undergoing lower limb orthopedic surgery and secondary objective to assess the association of baseline characteristics of patients (age, comorbidities, literacy, socio-economic class, etc) with postoperative delirium. 153 patients ≥65 years of age, ASA I and II, presenting for lower limb orthopedic surgery with a duration of at least 2 hours, requiring postoperative stay for at least 72 hours will be included. Those who are unable to speak and understand the Hindi language, have hearing or speaking impairment, or have pre-existing neurological status such as altered mental status, or dementia will be excluded. The cognitive screening will be administered one day before the scheduled surgery during the preanaesthetic visit. The patients will be screened on postoperative day 3 using the Confusion Assessment method.

AFT requires patients to name as many animals as possible within 60 sec, with one point given for each unique animal. Scores< 15 points have demonstrated high sensitivity and specificity (88% and 96%, respectively) for Alzheimer’s dementia in the memory clinic setting. This requires adequate memory as well as effective executive functions. Six-item screener is a simple cognitive screening test consisting of a 3-item recall and a 3-item temporal orientation (day of the week, month, year). Each correct response earns 1 point for a total of 6 points. Administration time is 1 minute, not including the delay for the recall component.