Memory for pain after nerve-block injections.

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.