Acute and Chronic Pain

Acute and Chronic Pain – Thomas Horton, Soibhan Kelley

  • There are physiological AND emotional components to pain. Biopsychosocial factors must be addressed. Examples include anxiety/depression, physical debility, and poor social support.  Many pts will not be completely free of pain, so it is important to set realistic boundaries and goals along with each individual.
  • Central sensitization is a phenomenon where the nervous system persists in a state of high reactivity which lowers the threshold for pain stimuli.  Two characteristics of centralized pain are allodynia (pain from non-painful stimuli) and hyperalgesia (painful stimuli perceived as more painful).
  • You must ask “why does this particular patient have pain?” Cancer patient vs degenerative disc disease will have different therapeutic plans.

 

Pharmacologic Therapy 

Acetaminophen:  650mg q6hr or 1g q8h. <3g/day. (<2g in liver patients)

  • Avoid if you are worried about masking fevers.

 

NSAIDs:  A great option for acute pain, especially musculoskeletal, HA, and nephrolithiasis in eligible patients (ex: IV/po ketorolac, ibuprofen, naproxen, etc)

  • Avoid in acute or chronic kidney disease and risk of bleeding. Caution in CAD/PVD

 

Topical Analgesics: Best for localized pain but utilized frequently as part of a multimodal regimen

  • Lidocaine ointment, patches (PADR needed at VA for patches. Can get by saying contraindication to TCA/gabapentinoids/SNRIs due to sedation risk)
  • Menthol salicylate gel
  • Diclofenac Gel (PADR needed at VA) 
  • Capsaicin gel    
  • Morphine gel (typically limited to oncology patients with tumor breakdown through skin)

 

Neuropathic Agents: Best for neuropathic pain but can be tried for other chronic pain or as part of acute pain regimen. SNRIs and TCAs can provide additional benefit if a pt has comorbid depression, anxiety or insomnia (TCA).  Most agents take 6-8 weeks for peak effect.

  • Gabapentin (Initial: 100 to 300 mg 1 to 3 times daily). Can be used for acute pain.
  • Pregabalin (Initial: 25 to 150 mg/day in 2 to 3 divided doses). Has better bioavailability. May work in patients who did not tolerate or did not have success with gabapentin.
  • Duloxetine (Initial: 30 mg daily for 1 to 2 weeks, then increase to 60 mg daily as tolerated)
  • Amitriptyline (Initial: 10 to 25 mg once daily at bedtime)

 

Muscle Relaxants: Should be used temporarily and intermittently but some benefit from longer term use. Great for paraplegia, spinal injury, spasticity.

  • Methocarbamol (Initial: 1.5 g 3 to 4 times daily for 2 to 3 days then decrease dose to ≤4.5 g/day in 3 to 4 divided doses). Preferred initial agent as has least SE.
  • Tizanidine (Initial: 2 to 4 mg every 6 to 12 hours as needed and/or at bedtime) – important to watch out for withdrawal in patients that take frequently at home.
  • Cyclobenzaprine (Initial: 5 to 10 mg once daily before bedtime)
  • Metaxalone (Oral: 800 mg 3 to 4 times daily)

 

Opioids: Frequently used in hospital for acute pain. Limit use as much as possible in chronic pain as contributes to long-term central sensitization.  May benefit some patient populations but should always be used as a component of a comprehensive, multimodal, patient-specific treatment plan.

  • Refer to section under Opioids: General Principles & Conversions for OME equivalents
    • If >80 OME per day, ensure patient is prescribed naloxone
    • If >120 OME per day, refer to pain clinic

 

  • Common choices for acute pain in hospital (always start at low end for opioid naïve):
    •    Oxycodone (PO) 5-10mg q4 to 6 hours prn
    •    Hydromorphone (IV) 0.25 to 1mg q2 to 3 hours prn
  • For pts on opioids at home, should always continue in hospital to avoid withdrawal unless clinically contraindicated (e.g., respiratory depression). Can always titrate dose as needed
  • Tramadol:  Has opioid & NSAID properties. Of note, tramadol also inhibits serotonin and norepinephrine reuptake. Metabolized by CYP3A4 and CYP2D6 so there is variability between patients. Typical dose: 25 to 50mg q4 to 6 hours prn.

 

NMDA Antagonists: Usually prescribed by our pain management colleagues but worthwhile to think about as a potential option if a patient’s pain continues to be difficult to control. 

  • Ketamine (IV infusion). SE includes AMS/delirium, hallucinations, and dissociation.
  • Memantine (PO)

 

Alpha 2 agonists (central pain): Not commonly utilized in everyday practice, but helpful in certain patients with chronic pain (off-label). Guanfacine vs clonidine  

 

Non-pharmacologic therapies

Procedural Intervention: Best utilized when there is a specific, targetable

  • Referral to chronic/interventional pain management (Nerve blocks or Radio-ablative therapy)

 

Adjunct Therapies: Patient’s will have varying opinions and responses on adjunctive therapies, but these can be as important as any pharmacologic therapy. CBT, personalized exercise regimen, PT/OT, chiropractor, acupuncture

 

Additional Resources for Residents 

  • Pain Management Center at VUMC 
  • Pain Clinic at the VA. Would specify whether or not you are OK with them initiating opioids.
  • Osher Center for Integrative Health at Vanderbilt. (VA pts may utilize this service if they have private insurance)  

 

Acute pain for special populations

Renal dysfunction: Check meds are renally dosed and start with non-sedating options. Always avoid NSAIDs, morphine and codeine. Acetaminophen and topicals are safe.

  • Opioids: oxycodone 2.5 to 5 mg, IV dilaudid 0.25-0.5mg, fentanyl IV 25 to 50mcg
  • Gabapentin: start with spot 100mg. Be extremely careful with quick uptitration in CKD due to sedation risk.
  • Methocarbamol: no specific renal dosing, try 500-750mg initially

 

Cirrhosis: Always avoid NSAIDs, morphine, codeine, hydromorphone (may be OK in mild to moderate cirrhosis)

  • Acetaminophen (2g max/d) & topicals are safe
  • Gabapentin: start with spot 100mg
  • Methocarbamol: no specific hepatic dosing, try 500 mg initially
  • Other options: consider tramadol 25-50 mg vs oxycodone 2.5 mg

 

History of substance use disorder: Overnight, always review handoff as day team likely has specific plan in place.

  • With substance use history, opioids should be avoided. Rely on multimodal agents as above
  • Patients who are in recovery may prefer to avoid opioids themselves
    • Pts can and do have acute, severe pain due to injury, infections, procedures, et
    • NEVER withhold opiates if clinically appropriate, regardless of substance use history