Analgesia and other causes of amnesia that mimic post-traumatic amnesia (PTA): A cohort study

Objective. This study explores the possibility that a post-traumatic amnesia (PTA) like phenomenon is caused by the administration of drugs in hospital following injury and that this may be observed in patients who have not suffered a traumatic brain injury (TBI). This work also explored the possibility for an additional contribution to this phenomenon of demographic and psychological variables. Method. Sixty-three orthopaedic patients with no evidence of brain injury were recruited to a two-phase study. Medication records, demographic, and psychological data were obtained at the phase 1. At follow-up interviews (phase 2), psychological data (mood and post-traumatic stress disorder, PTSD) were again obtained and retrospective assessment of PTA using the Rivermead PTA protocol was carried out in 47 patients. Results. Thirty-eight per cent (N=18) of the total sample (N=47) reported a PTA-like phenomenon despite not having suffered TBI. A logistic regression model including the receipt of opioids, surgery, and anxiety-related variables, was significant in predicting this phenomenon (χ²=22.054, df=4, p≤.01) and accounted for up to 57.5% of variation in the data. Age, either alone or in interaction with opioid use, depression, and PTSD symptoms were not significant predictors. PTA-like phenomenon did not occur without at least one predictive factor. Conclusion. Receiving opioids, undergoing surgery, and suffering clinical levels of anxiety at an early stage following injury, can lead patients who have not suffered a TBI to report a PTA-like phenomenon at follow-up. This suggests that retrospective PTA assessment on actual brain injury patients may also be influenced by these factors.