Understanding Chronic Pain: The Transition from Acute Pain and Effective Treatment Strategies

1. Supported in part by Arkansas Blue Cross and Blue Shield and the Office of the Arkansas Drug Director and in partnership with the Arkansas Academy of Family Physicians (AAFP), the Arkansas Medical Society (AMS), the Arkansas State Medical Board (ASMB), the Arkansas Department of Health (ADH) and its Division of Substance Misuse and Injury Prevention (Prescription Drug Monitoring Program—PDMP) Continuing Education Credit: TEXT: 501-406-0076 Event ID:29509-24581

2. The Transition Johnathan Goree, MD Director of Chronic Pain Division Assistant Professor Department of Anesthesiology University of Arkansas for Medical Sciences

3. Poll Everywhere • Phone • Text JOHNATHANGOR491 to 37607 to respond • Computer • Respond at Pollev.com/johnathangor491

4. Disclosures • I have no financial interests to disclose related to this presentation • I will present some non-FDA approved uses of medications which include steroids (dexamethasone) for lumbar epidural steroid injections and anti-convulsants/anti-depressants for the treatment of neuroinflammatory chronic pain. Both of these medications have been used for these indications for over 20 years.

5. Definition of Pain • International Association for the Study of Pain • An unpleasant sensory and emotional experience arising from actual or potential tissue damage or described in terms of such damage • Sensory, emotional, cognitive, and behavioral components that are interrelated with environmental, developmental, socio-cultural, and contextual factors

6. Nocioceptive Somatic Bone, joint, muscle, skin, or connective tissue Well localized Aching & throbbing Visceral Visceral organs such as GI tract Poorly localized Cramping Neuropathic Central Injury to peripheral or central nervous system causing phantom pain Dysregulation of the autonomic nervous system (e.g. Complex regional pain syndrome) Peripheral Peripheral neuropathy due to nerve injury Pain along nerve fibers Classification of Pain http://www.med.umich.edu/PAIN/pediatric.htm

9. Chronic Pain • “…the use of opioids in treating chronic pain (pain lasting longer than 3 months or past the time or normal tissue healing)” • CDC Guidelines for Prescribing of Opioids for Chronic Pain

10. Question? • If Chronic Pain is purely determined by time (3 months)… why do opioids work well for ACUTE pain but poorly for CHRONIC pain? Laceration? Broken Leg? Wisdom Tooth Surgery? Back Pain?

11. The Transition • Spinal Cord • Periphery • Brain

12. At the Spinal Cord

13. Acute v. Chronic Pain • AMPA receptor • Primary Excitatory receptor • Glutamate is primary agonist • Permeable to Na • Causes basic membrane depolarization • Propagation of action potential

14. Acute v. Chronic Pain • NMDA receptor • Glutamate is primary agonist • Blocked by Mg at resting state • Mg is expelled with repeated depolarization or high levels of Glutamate • NMDA is permeable to Na AND Ca • Calcium sets off cascade of events which include • It makes AMPA receptors more permeable • Adds more AMPA receptors to the synapse

15. At the Periphery

16. Chronic Inflammation • Prolonged inflammation causes continued release of inflammatory mediators • Through various intracellular mechanisms • Pain threshold in presynaptic neuron decreases • Increased Substance P release • Causes neurogenic inflammation • May affect mood, cause stress From: Transition from acute to chronic pain ContinEducAnaesthCrit Care Pain. 2014;15(2):98-102. doi:10.1093/bjaceaccp/mku044

17. At the Brain

18. Mind • Changes in ability to cope with pain • Increased rates of anxiety and depression • Higher rates of substance misuse and addiction

19. How fast does this happen? • Maybe faster than we think

20. Remifentanil • 3 minute half life • Dream for anesthesiology • Can use for severe pain of surgery • Will be out of system by the time the patient wakes up • Decreased use of long term opioids!

21. Remifentanil • Patients who received remifentanil in the operating room have: • increased peak POD1 pain scores • Increased rates of opioid induced hyperalgesia • Lower satisfaction

22. What does this mean clinically? • Poorly treated ACUTE pain leads to CHRONIC pain. • Recognize who is at risk

25. Maybe opioids don’t work for chronic pain because the mechanisms are different?

26. Questions? • Cases?

27. Discussion • Patient is a 54 y/o male with severe axial back pain for 1 month after lifting a bag of mulch from his trunk. Patient has taken ibuprofen and tramadol without much relief. Patient said that this pain has gotten worse over the past 2 weeks and it is limiting his mobility. • Is this poorly treated acute pain or chronic pain?

28. Supported in part by Arkansas Blue Cross and Blue Shield and the Office of the Arkansas Drug Director and in partnership with the Arkansas Academy of Family Physicians (AAFP), the Arkansas Medical Society (AMS), the Arkansas State Medical Board (ASMB), the Arkansas Department of Health (ADH) and its Division of Substance Misuse and Injury Prevention (Prescription Drug Monitoring Program—PDMP) Continuing Education Credit: TEXT: 501-406-0076 Event ID: 29509-24581