Memory for pain after nerve-block injections.

ABSTRACT

OBJECTIVE: To examine the accuracy of memory for pain in patients with chronic pain after injection of a local anesthetic and to investigate psychological factors hypothesized to coincide with distortion of memory. DESIGN: Consecutive patients receiving nerve-block injections recorded pain before the block, during the effect of the block, approximately 2 days after the block, and 2 weeks after the block. Memory for pain during the effect of the block was assessed 2 days and 2 weeks after the block for comparison with recorded pain ratings. SETTING: Outpatient, multidisciplinary pain-treatment center of a university medical center. PATIENTS Forty-nine adult patients with chronic pain. INTERVENTIONS: Local nerve-block injections resulted in a significant, temporary reduction in pain, thus allowing patients to rate, and later recall, intensity of reduced pain. OUTCOME MEASURES: Subjective ratings of pain intensity (numeric rating scale) were compared with recalled pain intensity. Demographic variables and psychological self-report measures were administered at evaluation. RESULTS: Memory distortions are commonplace and are more likely to involve recollection of higher pain levels than were reported at the time of the injection. Psychological self-report measures did not identify subjects who experienced distorted memory for pain relief. CONCLUSIONS: An awareness of these distortions should lead health-care professionals to monitor and refer to patients' actual pain reports made during a treatment intervention rather than relying on patients' recall to gauge the efficacy of interventions. Memory distortions could influence avoidance behaviors implicated in the development of chronic pain by some theories.