Anterograde amnesia and disorientation are associated with in-patients without traumatic brain injury taking opioids. Retrograde amnesia (RA) is absent. RA assessment should be integral to post-traumatic amnesia testing.

ABSTRACT

The Glasgow Coma Scale (GCS) only assesses orientation after traumatic brain injury (TBI). 'Post-traumatic amnesia' (PTA) comprises orientation, anterograde amnesia (AA) and retrograde amnesia (RA). However, RA is often disregarded in formalized PTA assessment. Drugs can potentially confound PTA assessment e.g. midazolam can cause AA. However, potential drug confounders are also often disregarded in formalized PTA testing. One study of medium-stay elective-surgery orthopaedic patients (without TBI) demonstrated AA in 80% taking opiates after general anesthesia. However, RA was not assessed. Opiates/opioids are frequently administered after TBI. We compared AA and RA in short-stay orthopaedic surgery in-patients (without TBI) taking post-operative opioids after opiate/opioid/benzodiazepine-free spinal anesthesia. In a prospective cohort, the Westmead PTA Scale (WPTAS) was used to assess AA (WPTAS<12), whilst RA was assessed using the Galveston Orientation and Amnesia Test RA item. Results were obtained in n=25 (60±14yrs, MF 178). Surgery was uncomplicated all were discharged by Day-4. All were taking regular oxycodone as a new post-operative prescription. Only one co-administered non-opioid was potentially confounding (temezepam, n=4). Of 25, 14 (56%) demonstrated AA five (20%) were simultaneously disorientated. Mean WPTAS was 11.08±1.22. RA occurred in 0%. CONCLUSIONS: AA and disorientation, but not RA, were associated with in-patients (without TBI) taking opioids. Caution should therefore be applied in assessing AA/orientation in TBI in-patients taking opioids. By contrast, retrograde memory was robust and more reliable even in older patients with iatrogenic AA and disorientation. RA assessment should therefore be integral to assessing TBI severity in all formalized PTA and GCS testing.