Abstract
Importance: Delirium is a common problem in patients undergoing surgery. Evidence suggests that the type of anaesthesia used and post-operative pain management approach can impact delirium frequency, but there is no consensus on this issue.
Objectives: This study explored the role of peri-operative pain management modalities, including nerve block, in managing postoperative pain and their association with delirium development.
Design: This is a retrospective cohort study of 440 patients who underwent lower limb amputations, and hip and knee arthroplasties between January 2010 and December 2017 were reviewed.
Setting: Charts of patients who underwent surgery and were admitted to the Hunter Holmes McGuire VA Medical Center, Richmond, VA, were reviewed.
Participants: A total of 460 charts were reviewed (20 were excluded) of patients undergoing total hip arthroplasty, above knee amputation, total knee arthroplasty, below-knee amputation and trans metatarsal amputation. As a problem in the post-operative period, delirium had to be clearly stated in the patient’s record.
Main outcome: Development of delirium during the post-operative period associated with the different types of pain management strategies.
Results: A total of 60 patients (13.6%) from the 440 studied developed postoperative delirium. Among the different pain management strategies (IV Acetaminophen, gabapentin, oral narcotics, patient-controlled analgesia, and non-steroidal anti-inflammatory drugs), only gabapentin was associated with delirium, demonstrating 2.27 times higher risk (P=0.0085). We also found that prior narcotic use increased the odds of delirium (P=0.0053). Even after controlling for the anaesthesia type (general, local, regional, spinal and epidural), no association between nerve block and delirium was observed (P=0.41).
Conclusion and Relevance: Taking gabapentin post-operatively for pain management, and having a history of ongoing narcotic usage before surgery, were associated with a higher risk of developing delirium. We found no association between nerve block used and the development of delirium.

Key words: Delirium, Post-operative Pain, Gabapentin, Nerve block, Orthopedic Procedures