TRANSITION FROM ACUTE TO CHRONIC PAIN

Friedman BW, Abril L, Naeem F, Irizarry E, Chertoff A, McGregor M, Bijur PE, Gallagher EJ. Predicting the transition to chronic pain 6 months after an Emergency Department visit for acute pain: a prospective cohort study.

J Emerg Med 2020 Sep 9. DOI: 10.1016/j.jemermed.2020.07.016

Online ahead of print.

Introduction

From surgical literature it is well known that early interventions can reduce the incidence of chronic pain. If ED patients who are at risk of developing chronic pain could be identified and treated aggressively in the acute phase, this might prevent chronic pain after an ED visit. However, evidence about the transition from acute to chronic pain in ED patients is lacking.

Objectives

1. To describe the frequency of new-onset chronic pain among a cohort of ED patients with acute pain.

2. To determine whether clinical features available earlier in the course of healing can be used to predict the transition to chronic pain.

3. To test the hypothesis that persistent pain 1 week after an ED visit for acute pain would be associated with the development of chronic pain 6 months after the ED visit.

Design

Prospective, observational cohort study

Setting

Two academic, urban EDs in the USA

Population

Patients 18 years and older presenting with acute pain (≤10 days) from any cause who were discharged home from the ED with a prescription of an oral opioid. They could not have experienced pain in the same body region during the previous 6 months, could only be enrolled once and were required to be opioid-naïve (defined as no opioid use in the previous 6 months).

Exclusion criteria: use of any analgesic >10 days per month on average prior to the onset of acute pain; admission to the hospital.

Methods

All consecutive patients were recruited by trained research associates at the end of the ED visit and followed-up at 1 and 2 weeks as well as 3 and 6 months after disposition. 

 

Outcomes

1. New-onset chronic pain (defined as reported pain on ≥50% of days and recorded at 6-months follow-up

2. - Moderate or severe pain in the affected body part at 3 or 6 months follow-up

    - Frequency of pain in the affected body part

    - Ability to resume all activities compared to before the initial ED visit

Results

A total of 733 patients were approached of whom 484 were recruited in the study. 

Median age was 45 years and 56% were female. 

The top-3 of affected body parts were: extremities (46%); neck and back (21%) and abdomen and pelvis (20%). Median duration of pain was 2 days.

At discharge from the ED the prescribed median morphine equivalents was 75mg.

At 6-month follow-up: 27% (95%CI 23-31) met the definition of chronic pain.

 

Regarding moderate to severe pain at different time points:

- after 1 week: 49%

- after 2 weeks: 40%

- after 3 months: 22%

- after 6 months: 17%

At 6-month follow-up 86% were able to resume daily activities. 

Multivariable logistic regression showed associations with development of chronic pain:

- pain in neck and back: OR 2.6 (95%CI 1.3-5.6)

- pain in extremity: OR 2.4 (95%CI 1.2-4.7)

- anticipated duration of pain (by patient) of >1 week: OR 1.9 (95%CI 1.0-3.4)

- some pain at 1-week follow-up: OR 3.8 (95%CI 1.6-8.8)

- some pain at 2-weeks follow-up: OR 14.6 (95%CI 5.1-41.7)

Other factors such as age, gender, depression and opioid use were not associated with chronic pain.

Conclusion

About one-quarter of patients presenting with acute pain from any cause developed chronic pain at 6 months after discharge from the Emergency Department. Persistence of pain at 1 week after presentation might predict patients at risk.

 

Pros

Prospective study in which patients were recruited by independent trained research assistants, available 24 hours per day, 7 days per week. Excluded patients were accounted for in a patient flow chart. A Patient Health Questionnaire-9 depression instrument was used in which several components, such as stressors, attitudes and coping mechanisms were evaluated.

Limitations

Although patient recruitment seems consecutive, a total of 733 patients were approached during the 9-month study period. This appears to be a small number as patients were recruited in two EDs with a combined census of 180,000 annually. However, we assume all consecutive patients were recruited. 

Data were available for the primary outcome in 408 patients (meaning 16% were lost to follow-up), not really a limitation as this is <20% of total population.

The study was performed in a heterogeneous population with pain from any cause. 

Level of evidence 1b

Comments

1. The study was performed in the USA. Due to the opioid epidemic, there are strict regulations regarding opioid prescription, as compared to most European countries. Therefore, it is questionable whether these study results could be extrapolated to ED practice outside the USA.

2. I would love to see the pain scores of the patients, both at baseline and at the moment of discharge from the ED, as I'm curious whether higher pain scores at discharge might influence transition to chronic pain and whether little decreases in pain scores during ED stay might play a role as well.

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