Acute and Chronic Pain¶

Thomas Horton, Soibhan Kelley

There are physiological AND emotional components to pain. Biopsychosocial factors must be addressed. Ex: anxiety/depression, physical debility, and poor social support. Many pts will never be completely free of pain, so it is important to set realistic expectations
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)

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
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. 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.
Complementary and Integrative Health consult at VA
Osher Center for Integrative Health at Vanderbilt

Acute pain for special populations¶

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

Acetaminophen and topicals
Opioids: oxycodone 2.5 to 5 mg, IV hydromorphone 0.25-0.5mg, fentanyl IV 25 to 50mcg
Gabapentin: start with spot 100mg. Be extremely careful with quick up titration 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, typically rely on multimodal agents as above. Patients who are in recovery may prefer to avoid opioids themselves
However, patients with OUD can and do have acute, severe pain due to injury, infections, procedures, etc. NEVER withhold opiates if clinically appropriate, regardless of substance use history

Last update: 2022-06-24 16:11:24