Pain Management

1. Pain Management Lalan S. Wilfong, MD March 25, 2004

2. What is Pain? • Definition by the International Association for the Study of Pain • Unpleasant sensory and emotional experience • Associated with actual or potential tissue damage • Or described in terms of such damage

3. Physiology of Pain • Primary afferent nociceptors • Nerves that respond to painful stimuli • Can respond to many different types of stimuli • Sensitization • Intense, repeated or prolonged stimuli • Threshold for activating nerves is lowered • Inflammatory mediators such as bradykinin, prostaglandins, and leukotrienes

4. Physiology of Pain • Central pathways • Axons of primary nociceptors enter the spinal cord via the dorsal root • Transmits pain signal to brain sites • Axon of each primary contacts many spinal neurons • Each spinal neuron receives convergent input from many primary afferents

5. Referred Pain • All spinal neurons receive input from viscera and skin • Convergence patterns are determined by the spinal segment of the dorsal root ganglion • For example both the diaphragm and the skin of the shoulder have same dorsal root

6. Types of Pain • Somatic • Nociceptors in cutaneous or deep tissues • Dull or aching but well-localized pain • Visceral • Nociceptors from involvement of the viscera • Poorly localized and described as deep, squeezing, and pressure-like • Can be associated with nausea or sweating • Neuropathic • Injury to peripheral or central nervous system • Often severe and described as burning or shock-like

7. Acute Pain • Well-defined temporal pattern of onset • Associated with subjective and objective physical signs • Hyperactivity of the autonomic nervous system • Usually self-limited • Responds to analgesics and treatment of the underlying cause • Two types • Subacute – comes on over several days with increasing intensity • Episodic – occurs during confined periods of time

8. Chronic Pain • Persistence of pain for more than 3 months • Autonomic nervous system adapts • Patients lack objective signs of pain • Leads to changes in personality, lifestyle and functional ability • Treatment requires control of pain and its multidimensional aspects

9. Chronic Pain • Causes are multiple • Trauma, surgery • Cancer, medical conditions • Baseline pain • Average pain intensity for 12 or more hours in a 24 hour period • Breakthrough pain • Transient increase in pain from any cause

10. Measurement of Pain • Important to determine but hard to define • Many scales are used • Mild, moderate, severe, excruciating • Numeric scales: 1 (no pain) – 10 (worst possible pain) • Visual analog scales: faces, 10cm line • All of these are validated instruments

11. Clinical Assessment • Believe the patient's complaint of pain • Take a careful pain history • Evaluate the patient’s psychological state • Perform a careful medical and neurological examination • Order appropriate diagnostic studies • Treat the pain • Reassess response to therapy

12. Pain History • Description of site of pain • Quality of pain • Exacerbating and relieving factors • Temporal pattern • Associated symptoms and signs • Interference with ADL’s • Effect on psychological state • Response to previous and current therapies

13. Three-Step Analgesic Ladder of the World Health Organization Levy, M. H. N Engl J Med 1996;335:1124-1132

14. Management • Modalities • Analgesic drugs • rehabilitation • psychotherapy • cognitive • surgical • Individualize treatment plan

15. Nonopioid Analgesics • Tylenol • Main serious side effect is liver toxicity • Counsel patients on all Tylenol containing drugs • NSAIDS • Main serious side effect is GI ulcers • Risk factors: steroid use, advanced age, higher doses, history of ulcer disease • Most inhibit platelets • Analgesia limited by a ceiling effect • Tolerance and physical dependence do not occur • Mechanism of action is inhibiting prostoglandins

16. Opioid Drugs • Morphine is the prototype • Vary in potency, efficacy, and adverse effects • Produce analgesia by binding to discrete opiate receptors in the peripheral and central nervous systems • Do not have a ceiling effect, but care is needed to balance analgesia vs. side effects • Nausea, mental clouding, sedation, constipation, tolerance, physical dependence, and myoclonus

17. Principles of Opioid Therapy • Start with a specific drug for a specific type of pain • Know the equianalgesic dose of the drug and its route of administration • Administer analgesics regularly after initial titration • Gear the route of administration to the patient’s needs • Use a combination of drugs • Anticipate and treat side effects

18. Points • Morphine is the prototype drug • Oxycodone has street value • Hydromorphone has poor oral availability • Methadone is a great drug, but • Negative pre-conceived notions • Long half-life that is unpredictable • Demerol not a good drug for pain as it’s inactive metabolite can cause seizures • Fentanyl only comes in a patch • Great for patients who cannot take po • Hard to titrate

19. Sedation Discontinue all other drugs that can cause this Use drug with shorter ½ life Ritalin, caffeine or an amphetamine can help Respiratory depression Occurs with other CNS symptoms Tolerance develops Can reverse with naloxone Nausea Medullary chemoreceptor trigger zone Tolerance develops Switching drugs can help Constipation START REGULAR BOWEL REGIMEN!! Senna and colace most useful Never gets better Pruritis Tolerance develops Use H1 blockers Side Effects

20. Tolerance • Effectiveness of analgesia diminishes over time • Increase dose of drug • Cross tolerance not complete; so can change drugs • Taper drugs slowly • Withdrawal – agitation, tremors, insomnia, fear, hyperexcitability, and pain • Slowly tapering drug can prevent these symptoms

21. Enhance analgesia especially for neuropathic pain Antidepressants Tricyclic Enhance serotonin activity Paxil Anticonvulsants Stabilize membranes and alter sodium and calcium influx Gabapentin, tegretol, dilantin Steroids Improves mood and appetite as well Helpful in bone or tumor pain Other Benzodiazepines Neuroleptics bisphosphanates Adjuvant Drugs

22. Other Techniques • Psychotherapy • Local anesthesia • Nerve blocks • Intrathecal Opioids

23. Examples • Mr. H is a 50 y/o WM who presents complaining of 2 day history of a painful right great toe • PE reveals a swollen right toe that is very sensitive to the touch • How do you treat him? • NSAIDS such as Indocin

24. Case 2 • John is a 40 year old with AIDS. He has been on AZT and ddc • Presents with burning pain in his hands and feet which he describes as severe and keeps him awake at night • What do you do? • Consider gabapentin, TCA’s, opioids

25. Case 3 • David is a 67 y/o farmer with colon cancer with liver metastases • He reports increasing right upper quadrant pain that he describes as a 4/10 • What do you give him? • Tylenol or NSAIDS? • Mild opioid combination such as Lortab

26. David’s disease progressed He is using 2 lortab (5/500) every 6 hours and 2 Percodan (5/325) every 8 hours without relief What’s wrong with this? Tylenol toxicity You decide to place him on a pure opioid. What do you do? Figure total opioid dose 2 x 5 x 4 = 40mg 2 x 5 x 3 = 30mg Convert to equivalent dose of new drug Both are 1:1 dosing with morphine MsContin 30mg BID Add Breakthrough or Rescue med 10% of total daily dose Lortab 1-2 every 6 hours Case 3 part 2

27. Case 3 part 3 • David now presents with acute n/v after chemotherapy and worsening back pain • Admitted for rehydration • What do you do about his pain? • MsContin 30mg bid and roughly 6 lortab per day • What do you do?

28. Loading dose Drug to control pain initially Eg 5mg morphine every 10 minutes Continuous dose Continuous infusion of pain medication Don’t use for narcotic naïve PCA dose How much patient will get when they hit the button Order dose and time interval Booster dose Nurse can give extra dose if patient in pain Nurse should assess patient first for side effects Lockout dose Usually 4 hours How much is too much? Adjust based on patients age, size, and history of narcotic use PCA

29. Case 3 • Total narcotic dose • 30mg morphine 2x/day • 6 lortab with 5mg hydrocodone per day • Total oral dose of 90mg • Convert to IV dose • Morphine 3:1 oral to IV == 30mg morphine • 1mg/hour continuous infusion of morphine • Breakthrough dose • 1 mg every 10 minutes PRN • Booster dose by the nurses of 1-2 mg every 30 min • Lockout dose – 4 hours max 20 mg

30. Case 3 • Next day, David’s still in 5/10 pain and he used a total of 50mg morphine. • Why is he still in pain? • Tolerance? • Increase PCA dose to 2 mg • Next day, David still in 5/10 pain and he used 60 mg morphine • Increase CI dose to 2 mg/ hour

31. Case 3 (cont) • Next day, David is better. He is eating well and pain controlled on 50 mg total morphine • You want to change to different oral narcotic such as Oxycontin • What do you do? • Convert to oxycodone dose • 50mg IV morphine = 150mg PO morphine • morphine and oxycodone 3:2 equianalgesic • Oxycontin 40 mg bid with oxycodone 5-10 mg every 4 hours for breakthrough

32. Don’t Forget • Bowel regimen • Senna/colace • Lactulose • MOM • Sorbitol • Miralax • Etc • Adjuvant drugs

33. Obligatory Kid Pic