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Acute Pain Management in Adults

Summary
Basic Information
Treatment
Special Considerations
Follow-Up
Author Affiliations

Apr.19.2024

Acute Pain Management in Adults

Summary

Key Points

Identification and treatment of the underlying cause is important in the treatment of acute pain
Acute pain should be treated using a multimodal approach including nonpharmacologic strategies, medications, and procedures
Nonpharmacologic approaches include ice/heat, rehabilitation psychology support, cognitive strategies (eg, guided imagery, music therapy, relaxation, distraction), physical therapy, massage, use of TENS unit, among other treatments
Acetaminophen and NSAIDs should be considered first line treatment of acute pain, unless contraindicated
A multitude of other nonopioid medications are effective for acute pain including but not limited to steroids, gabapentinoids, IV ketamine, and IV lidocaine
Maximize use of nonpharmacologic and nonopioid pharmacologic therapies and only initiate opioids for acute pain if benefits outweigh potential risks to the patient
Consult an anesthesiologist or acute pain service for consideration of regional anesthesia (particularly epidural or peripheral nerve catheters)
A multimodal approach to acute pain management may reduce development of peripheral and central sensitization, which can increase risk of conversion to chronic pain

Alarm Signs and Symptoms

Severe abdominal pain (concern for gastric ulcer due to NSAIDs)
New onset hypotension or anemia (concern for gastrointestinal bleed due to NSAIDs)
Respiratory depression, sedation (consider naloxone in setting of opioid use)
Acute psychosis (if secondary to ketamine infusion, then discontinue ketamine)
Sedation, ringing in the ears, metallic taste in the mouth (in setting of lidocaine infusion may be early signs of local anesthetic toxicity that may lead to seizure or cardiovascular collapse, in which case discontinue lidocaine)
New severe back pain, new lower extremity deficits not explained by the epidural medication itself, and/or loss of bowel or bladder control (concern for epidural hematoma or abscess in setting of epidural infusion)
Shortness of breath and/or tingling in the arms (in setting of epidural may be signs of epidural too high leading to respiratory failure, in which case discontinue epidural infusion)

Basic Information

Terminology

Pain is "an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage," as defined by the International Association for the Study of Pain
Acute pain is typically:
- Sudden onset
- In response to a specific noxious stimulus
- Self-limited, as it should stop when the underlying cause is treated or healed
- Less than or equal to 1 month in duration
  - Subacute pain is present for 1 to 3 months

Background Information

Acute pain is one of the most common reasons patients present to the emergency department or primary care physicians
Acute pain that does not resolve may become chronic, which is associated with significant morbidity and socioeconomic impact
Acute pain may have an obvious etiology such as postsurgical pain or blunt trauma but may require further workup to diagnose and provide specific treatment
Characterization of pain will aid in diagnosis; important elements include:
- Location
- Intensity
- Quality (eg, sharp, throbbing, burning, tingling, stabbing, aching)
- Duration
- Associated symptoms such as weakness or numbness
Acute pain is most often reported using validated unidimensional assessment tools
- May not account for the complex nature of pain and impact on function
- The patient’s subjective report of pain is also important
- Assessing pain at rest and during mobilization may give a more thorough clinical picture
- Tools include (Figure 1):¹
  - NRS (numeric rating scale) requires patients rate pain intensity from 0 to 10
  - VRS (verbal rating scale) prompts patients to rate pain using a verbal description ranging from none, mild, moderate, to severe
  - VAS (visual analogue scale) asks patients to indicate their pain level along a continuum from no pain to worst pain imaginable

Treatment

Approach to Treatment

For many instances of acute pain, treatment of the underlying cause is required
- Therefore, accurate diagnosis is paramount
Regardless of cause, multimodal treatment is considered standard of care and includes nonpharmacologic management, drug therapy, and/or procedures²
Goals of acute pain management include:
- Reduce suffering
- Facilitate function and participation in therapies to promote healing
- Provide treatment with minimal adverse effects
Some surgical procedures have associated ERAS (enhanced recovery after surgery) protocols that include specific pain management recommendations
- Elements of these protocols may vary by institution though improved functional recovery and decreased complications are common goals
- Colorectal surgery
  - ERAS protocols for colorectal surgery emphasize opioid-sparing analgesia using agents such as oral acetaminophen and gabapentin/pregabalin, ketamine or lidocaine infusions, or thoracic epidural analgesia or transversus abdominus plane blocks, among other options to facilitate early mobility and return of bowel function³
- Spine surgery
  - ERAS protocols for spine surgery have shown shorter length of stay with decreased pain scores with use of acetaminophen, NSAIDs, gabapentin, and ketamine infusions⁴
- Many published, procedure-specific ERAS protocols are available for review²

Nondrug and Supportive Care

Nondrug and supportive care should be recommended to all patients given minimal adverse effects, few contraindications, and established efficacy across a variety of pain etiologies⁵
Apply ice and/or heat to affected areas to reduce pain
- Do not apply for excessive length of time or while sleeping to avoid skin irritation or breakdown
Consult rehabilitation psychology support if available
- Consult early, particularly in patients with significant trauma or preexisting mood disorders
Recommend cognitive strategies
- Nursing, psychology consult service, or hospital-provided television programming may assist patients with utilizing these strategies
- Examples include:
  - Guided imagery (eg, encourage patient to imagine walking through snow when experiencing a burning sensation)
  - Music therapy
  - Relaxation (eg, encourage deep breathing and meditation)
    - May be supported by mobile apps or patients’ preexisting practices
  - Distraction (eg, provide a crossword puzzle or coloring book)
  - Virtual reality
  - Hypnosis
    - May be useful for minor procedural pain and some patients may be appropriate for self-hypnosis training⁶
  - Aromatherapy
    - Lavender in particular may have potential for pain reduction⁷
Physical therapy should be engaged early for both outpatients and inpatients
- Special techniques for pain reduction exist for specific conditions; examples include:
  - Mirror therapy for phantom limb pain
  - Graded motor imagery for complex regional pain syndrome
Encourage massage for acute musculoskeletal pain with resulting muscle spasm
- Prescribe massage therapy for outpatients with specific muscular ailments
- Patients can use a self-massage cane at home as an alternative to formal massage therapy
TENS (transcutaneous electrical nerve stimulation) has evidence for benefit in acute pain, with some studies suggesting improved pain and reduced analgesic use compared to placebo in the perioperative period⁵
- Patients can purchase a low-cost device over the counter for home use without a prescription or it can be ordered in the hospital or provided during physical therapy sessions
- The device pads should be placed over the area of pain, along an affected muscle, or on either side of a surgical incision
- The stimulation should be increased to the maximum tolerated intensity for best effect. If it is painful or causing muscle twitching, it is set too high
- Physical therapists can help patients optimize device settings and placement
- TENS should be avoided in patients with:
  - Implanted electrical devices such as a pacemaker
  - Delirium
  - Extensive wounds or skin breakdown
  - Pregnancy, though TENS can be used safely with appropriate counseling regarding placement and during active labor
Consider spiritual care support

Drug Therapy

NSAIDs and acetaminophen (Table 1)
- Administer acetaminophen and NSAIDs as first line medications, either as a sole agent for mild pain complaints or in conjunction with other medications for more severe pain⁸
  - Unless contraindicated, consider scheduling acetaminophen to ensure patient timely dosing
- Adverse effects:
  - With prolonged use, all NSAIDs may cause:
    - Gastrointestinal bleeding
    - Gastric ulcer
    - Renal dysfunction
    - Cardiac events
  - NSAIDs carry a black box warning for use after coronary artery bypass graft⁹
  - Studies have evaluated the effect of NSAIDs on delayed bone healing and anastomotic closure. Some surgeons may prefer NSAIDs be avoided after certain surgeries. However, prudent use of limited duration (less than 10 days) is unlikely to have a clinically significant impact⁵
Steroids (Table 2)
- Consider systemic steroids if the patient has a significant inflammatory component to pain that is not responsive to NSAIDs; however, evidence is variable depending on indication
  - Systemic corticosteroids may improve pain more quickly due to acute radiculopathy but are likely no more effective than placebo in nonradiculitis pain¹⁰
- Indications for steroids include but are not limited to:
  - Bursitis
  - Tendinitis
  - Severe arthritis flair
  - Acute radicular pain
  - Cancer pain
- Adverse effects
  - Avoid use of steroids concurrently with NSAIDs to avoid gastric adverse effects
  - Steroids are associated with a multitude of other adverse effects including:
    - Elevated blood glucose
    - Elevated blood pressure
    - Increased appetite
    - Immune suppression
    - Poor sleep
    - Mood destabilization
    - Adrenal suppression with prolonged use
  - Use steroids with caution in patients with:
    - Diabetes
    - Uncontrolled blood pressure
    - Ongoing infection
    - Concern for poorly controlled mood disorder or history of mania
Opioids (Table 3)
- Reference the CDC Clinical Practice Guideline for Prescribing Opioids for Pain¹¹ as well as any opioid prescribing guidelines published by your state to ensure compliance with the most recent recommendations and rules
- Opioids are effective for moderate to severe acute pain
  - Maximize use of nonpharmacologic and nonopioid pharmacologic therapies and only initiate opioids for acute pain if benefits outweigh potential risks to the patient¹²
  - Prescribe the lowest effective dose
  - Adverse effects
    - Prescribe the lowest effective dose to minimize adverse effects including:
      - Respiratory depression
      - Sedation
      - Nausea and vomiting
      - Constipation
      - Pruritis
      - Urinary retention
      - Altered mental status
  - Cautions
    - Monitor patients at risk for respiratory effects such as those with chronic obstructive pulmonary disease or obstructive sleep apnea
    - Minimize concurrent use of other sedating medications such as benzodiazepines and Z-drugs
    - For patients chronically prescribed these medications, consider halving or holding home dosages until the effect of opioids is clear
    - Do not use long-acting oral opioids for acute pain due to safety concerns and inability to titrate doses easily
      - The fentanyl patch carries a black box warning for use in acute pain
  - Administration
    - Oral routes of opioids are preferred over IV due to longer duration of action with similar analgesic effects
    - Consider PCA (patient-controlled analgesia) when parenteral route is required
      - Do not use basal infusions in opioid-naïve adults due to increased risk of adverse effects without proven analgesic benefit
      - Minimize basal infusions in opioid-tolerant patients
Anticonvulsants/membrane stabilizers (Table 4)
- Medications such as gabapentin and pregabalin are commonly used as part of a multimodal pain strategy, particularly during the perioperative period⁵
  - Multiple dosing strategies have been studied with no clear best regimen¹³
    - Medication can be prescribed 2 to 3 times daily until acute pain has subsided or given as a single periprocedural dose
- Gabapentin/pregabalin are particularly beneficial in spine surgery, thoracotomy, amputation, and joint replacement. Adverse effects include:
  - Sedation
    - Reduce dose in renal dysfunction (though drugs themselves are not nephrotoxic) and in geriatric population
  - Peripheral edema
  - Dizziness
  - Tremor
- Cautions
  - In 2019 the FDA issued a statement warning that breathing difficulties may occur in patients using gabapentin and pregabalin who have respiratory risk factors such as concurrent use of opioids or other central nervous system depressants, COPD, or are older aged
  - Taper anticonvulsants over 1 week or more in patients predisposed to seizures rather than abruptly discontinuing
  - For patients already taking anticonvulsants for other indications such as topiramate for migraine headache or lamotrigine for mood stabilization, the addition of gabapentin or pregabalin is likely low yield for pain reduction
Specialized infusions (Table 5)
- Consult appropriate hospital resources (acute pain service, anesthesiology, ICU) for consideration of specialized infusions for acute pain. Ketamine infusions for acute pain (low dose) can be safely administered on regular inpatient hospital floors, though may require oversight by acute pain services or anesthesiology per local hospital policies⁵
  - Consider requesting evaluation for ketamine when pain continues to be difficult to manage despite multimodal analgesia
  - Indications
    - Ketamine is particularly useful in patients with opioid tolerance
    - Shown to be beneficial in spine surgery, thoracotomy, and many other surgeries
  - Adverse effects
    - Hallucinations, nightmares, nystagmus, increased salivation, increased sympathetic activity
    - Adverse effects more likely to occur at higher doses; low-dose infusions tend to be well tolerated
  - Contraindications
    - Although not absolutely contraindicated, use caution in those with poorly controlled psychiatric comorbidities such as psychosis, mania, and posttraumatic stress disorder
    - Avoid in patients with significant intracranial pathology as it may increase intracranial pressure at higher doses
    - Avoid in unstable coronary artery disease due to increased sympathetic activity
- Lidocaine infusions for acute pain are typically administered on regular inpatient hospital floors, though similar to ketamine may require oversight by acute pain services or anesthesiology per local hospital policies⁵
  - Indications
    - Postoperative pain (particularly beneficial for intraabdominal surgery and spine surgery)
    - Potentially useful in migraine headache, acute radiculopathy, renal colic
  - Adverse effects
    - Dizziness, tinnitus, perioral numbness, seizures, conduction delay, bradycardia
  - Contraindications
    - Absolutely contraindicated in Wolff-Parkinson-White syndrome and severe sinoatrial, atrioventricular, or intraventricular heart block
    - Use caution or avoid in patients with significant hepatic dysfunction as reduced clearance increases risk of local anesthetic toxicity
    - Avoid in patients with history of seizures, those unable to self-report adverse effects, or those taking medications that inhibit CYP1A2 and CYP3A4
    - Consult cardiology to assess risks for patients on additional antiarrhythmic agents, β-blockers, or α-2 agonists
- Dexmedetomidine infusions most often require continuous monitoring in the ICU as they can be sedating and cause hemodynamic changes¹⁴
  - Due to monitoring requirements, dexmedetomidine is usually reserved for cases when pain has not been sufficiently treated by other means
  - Indications
    - Postoperative pain
  - Adverse effects
    - Sedation, severe hypotension, bradycardia
    - May cause hypertension when stopped
  - Contraindications
    - Avoid if adequate monitoring not available (ICU) or concern for oversedation
- Magnesium is a less commonly used infusion¹⁵
  - Indications
    - Not a primary analgesic but may enhance role of other analgesics used in perioperative period
    - May be given as part of intraoperative analgesia
  - Contraindications
    - Will enhance effects of nondepolarizing muscle relaxants used in operating room
- Be aware that much of the literature supporting use of specialized infusion therapies comes from studies in perioperative management and there is little guidance for optimal postoperative dosing strategies
Adjunct agents
- Other agents that may have some utility in acute pain include:
  - Clonidine¹⁶
    - Typical dose 0.2 to 0.3 mg PO twice daily
    - May cause hypotension and rebound hypertension when discontinued
    - Avoid concurrent use with other antihypertensives
  - Dextromethorphan¹⁷
    - Typical dose 30 mg PO every 6 hours PRN pain
    - Can be considered an oral option of an NMDA (N-methyl-D-aspartate) receptor antagonist. However, supporting data in comparison to ketamine IV are extremely limited so it should be considered an end-of-the-line option
    - Can cause sedation
Muscle relaxants (Table 6)
- Evidence for use of muscle relaxants in acute pain is mixed and therefore not generally recommended in practice guidelines¹⁸
- If other analgesics have been insufficient or a patient endorses prior benefit, they can be trialed
- Given no one agent is known to be superior for acute pain, choose based on adverse-effect profile¹⁸
Topical agents (Table 7)
- Topical application of medications should be considered for acute pain and present less concern for systemic adverse effects

Table 1. Common dosing of acetaminophen and common NSAIDs.¹⁹
Drug	Dose	Comments
Acetaminophen	Oral/IV: 325-1000 mg every 4-6 hours¹⁹ Maximum: 4 g/day in typical adult. Consider dose reduction to 2-3 g/day in older adults²⁰ and patients with significant hepatic dysfunction²⁰	May cause hepatotoxicity
Ibuprofen	Oral: 400 mg every 4-6 hours Reduce dose to 200-400 mg in older adults	In patients with history of GERD or gastric ulcer, may add proton pump inhibitor as prophylaxis
Ketorolac	IV: 15-30 mg every 6-8 hours Reduce dose to 7.5 mg in older adults	Recommend limiting duration to 5 days to reduce incidence of adverse effects
Celecoxib	Oral: 100-200 mg twice daily Maximum: 400 mg/day	Reduced risk of bleeding due to selective COX-2 inhibition
Naproxen	Oral: 250-500 mg twice daily Higher doses of 750 mg can be given as a first dose for acute gout,²¹ bursitis, tendinitis, or other acute pain. Total daily dose should not exceed 1250 mg	If an NSAID must be used in a patient with preexisting cardiac disease, naproxen is likely the safest option

Table 2. Sample dosing strategies of commonly used steroids for acute pain.
Drug	Dose	Indication
Prednisone	40-60 mg PO daily, tapered over 3 weeks²²	Herpes zoster Note: Although this is commonly done, evidence is limited
Prednisolone	35 mg PO daily for 5 days²³	Acute gout
Methylprednisolone	24 mg PO for 1 day, 20 mg PO for 1 day, 16 mg PO for 1 day, 12 mg PO for 1 day, 8 mg PO for 1 day, 4 mg PO for 1 day²⁴	Sports-related injury, bursitis, tendonitis
Dexamethasone	0.1-0.2 mg/kg IV once²⁵	May be given preoperatively as adjunct to postoperative pain management

Table 3. Commonly used opioid medications with suggested starting dose.²⁶
Route	Drug	Starting dose	Comments
Oral	Oxycodone	5-10 mg every 4 hours PRN Reduce to 2.5 mg in geriatric patients
	Hydromorphone	2-4 mg every 4 hours PRN
	Morphine	7.5-15 mg every 4 hours PRN	Avoid in geriatric patients and patients with renal impairment
	Hydrocodone-acetaminophen	5-325 mg every 4 hours PRN	Ensure patient does not exceed maximum dose of acetaminophen per 24 hours Hydrocodone paired with 325 mg acetaminophen is known as Norco. When paired with 500 mg it was known as Vicodin and is no longer available
	Tramadol	50-100 mg every 4 hours PRN Do not exceed 400 mg in 24 hours Do not exceed 300 mg in 24 hours in patients older than 75 years	Has relatively low potency compared to other opioids so may be useful in patients sensitive to opioid-related adverse effects. However, can still cause somnolence and dizziness Use with caution in patients on SNRIs/SSRIs, TCAs, or similar agents due to risk of serotonin syndrome
IV	Hydromorphone	0.2-0.4 mg IV every 4 hours PRN PCA: demand dose 0.2 mg, lockout 10 minutes. Reduce demand dose to 0.1 mg in geriatric patients. May increase to 0.3 mg in opioid-tolerant²⁷	When using PCA, a loading dose may be required to bring a patient to a therapeutic window that is then maintained by the patient (eg, consider a loading dose that is twice the patient demand dose every 10 minutes × 3 doses)
	Morphine	1-2 mg IV every 4 hours PRN PCA: demand dose 1 mg, lockout 12 minutes. May increase to 1.5 mg in opioid-tolerant²⁷	Avoid in geriatric patients and patients with renal impairment
	Fentanyl	25-50 mcg IV every 4 hours PRN	Due to short duration of analgesia of 30-60 minutes, best reserved for specific painful procedure or wound care Hospitals may have specific policies regarding where fentanyl can by administered
	Meperidine	50-150 mg IV every 4 hours PRN Maximum 600 mg in 24 hours	Generally not recommended for pain management due to risk of neurotoxicity (particularly seizure) and available safer alternatives Concomitant use of cytochrome P450 3A4 inhibitors or monoamine oxidase inhibitors, or discontinuation of P450 inducers may result in fatal reactions
	Nalbuphine	5-10 mg IV every 4 hours PRN	As a lower potency opioid agonist-antagonist, may be useful in geriatric or frail patients 5 mg IV is given routinely as an effective treatment for opioid-induced itching
Other	Fentanyl lozenge	200 mcg transmucosal daily	Allows patient to self-administer medication by rubbing on inside cheek Only FDA-approved for management of breakthrough pain in opioid-tolerant patients with cancer
Other	Buprenorphine-naloxone	Sample dose: ¼ of buprenorphine-naloxone 2 mg-0.5 film SL 4 times daily PRN for pain (equivalent of 0.5 mg buprenorphine per dose)	Off-label use of suboxone Dosage for pain is significantly lower than that used for opioid use disorder Buprenorphine 0.5 mg SL is not expected to precipitate withdrawal, regardless of prior opioid administration. This dose is commonly used for microinduction of buprenorphine²⁸

Table 4. Anticonvulsant dosing strategies.^5,¹³
Drug	Dose
Gabapentin	Oral: 600-1200 mg 1-2 hours preoperatively, 600 mg postoperatively (single or multiple doses) Can consider continuing 600-900 mg 2-3 times daily in subacute phase though supportive evidence of this practice is inconsistent Renal dysfunction/geriatric patients: Reduce dose to 100-300 mg. Consider dosing immediately following dialysis²⁹
Pregabalin	Oral: 150-300 mg preoperatively followed by same dose 12 hours later Can consider continuing 75-150 mg 2-3 times daily in subacute phase though supportive evidence of this practice is inconsistent Renal dysfunction/geriatric patients: Reduce dose to 25-50 mg 2 times daily³⁰

Table 5. IV infusions for pain.
Drug	Dose
Ketamine^5,³¹	IV bolus: 0.3-0.5 mg/kg Infusion: 0.1-0.2 mg/kg/hour
Lidocaine⁵	IV bolus: 1.5 mg/kg Infusion: 1-2 mg/kg/hour
Dexmedetomidine¹⁴	IV bolus: 0.25-1 mg/kg over 10 minutes Infusion 0.2-1 mg/kg/hour
Magnesium¹⁵	IV bolus: 30-50 mg/kg Infusion: 6-20 mg/kg/hr

Table 6. Example muscle relaxant dosing and adverse effects.
Drug	Dose	Adverse effects/comments
Cyclobenzaprine³²	5-10 mg PO every 8 hours PRN	Sedation, associated with anticholinergic effects, avoid in patients at risk for arrhythmia or seizure, monitor for serotonin syndrome if used with other serotonergic agents; pregnancy category B
Methocarbamol³³	500-1500 mg PO every 6 hours PRN	Sedation, though low dosage may be associated with less sedation May cause black/green urine
Tizanidine³⁴	2-4 mg PO every 6 hours PRN	Hypotension, hepatotoxicity, sedation, interacts with CYP1A2 pathway (concomitant use with ciprofloxacin or fluvoxamine is contraindicated), use with other strong 1A2 inhibitors or oral contraceptives should be avoided (if clinically indicated start tizanidine at low dose and monitor closely for adverse effects)
Carisoprodol³⁵	350 mg PO every 8 hours PRN	Due to potential for addiction with lack of clear benefit, initiating carisoprodol is not recommended. Given potential for withdrawal syndrome, it is acceptable to continue in an acute setting, though consider reducing dose if patient is receiving other sedating agents
Diazepam³⁶	2-4 mg PO every 6 hours PRN	Generally avoided due to concern for respiratory depression when combined with other sedating agents in acute setting as well as potential for dependency and abuse. May be a role for use in spasticity
Baclofen³⁷	5 mg PO every 8 hours for 3 days, followed by 10 mg PO every 8 hours. May be titrated to 40-80 mg daily when used for spasticity	As an antispasticity agent, baclofen is considered off-label for use in skeletal muscle spasm. It is associated with a life-threatening withdrawal syndrome, especially at higher doses—caution should be used in patients with poor medication compliance

Table 7. Selection of topical agents and uses.^38,³⁹
Medication	Use
Lidocaine patch	To be applied over painful area. Intended to be used for superficial pain such as that associated with postherpetic neuralgia. Can be used around a surgical incision or drain. Available in OTC and prescription strength
Lidocaine gel/cream	Most useful for superficial pain. Can be used prior to procedures such as IV line placement in patients sensitive to needles. Available in OTC and prescription strength
Viscous lidocaine	Consider for use in wound care. For example, may soak burn wounds prior to dressing changes. Alternatively, can be used as a swish-and-swallow agent for patients with sores in mouth or sore throat (use caution in patients with aspiration risk). Typically used inpatient or in emergency department
Menthol cream	Particularly beneficial for musculoskeletal and joint pain. May combine with massage for acute massage spasm. Available OTC
Diclofenac gel	Particularly beneficial for musculoskeletal and joint pain with inflammatory component. This medication is intended to be used regularly 4 times per day rather than as needed. Available OTC
Capsaicin cream	Intended to be used for superficial neuropathic pain. If patient finds application painful, the area can be pretreated with lidocaine gel/cream. Available OTC

Treatment Procedures

Neuraxial or peripheral regional anesthesia can be performed in conjunction with the nonpharmacologic and pharmacologic modalities listed above to enhance pain relief and potentially minimize opioid use⁴⁰
- Consultation with anesthesiology, acute pain service, interventional radiology, or appropriately trained clinician or consult service is appropriate for consideration and placement of nerve blocks
Neuraxial blocks (epidural, spinal, or combined spinal/epidural)
- Provide effective analgesia in the chest, abdomen, pelvis, or lower extremities depending on level of placement
- May be used as part of a surgical anesthetic and/or for ongoing pain relief outside of surgery (eg, pain control for rib fractures)
  - Spinal injections allow direct administration of local anesthetic with or without opioid to the central nervous system
    - Most appropriate for a surgical anesthetic and not solely pain relief
  - Epidural anesthesia involves placement of a catheter to allow continuous administration of local anesthetic with or without opioid
    - May provide ongoing pain relief
  - Combined spinal epidural analgesia is used if both rapid onset of surgical anesthesia and prolonged pain relief are desired
- The area covered by an epidural is dependent on:
  - Level of placement
  - Rate and volume of medication being infused
  - Position of the patient
  - Height of the patient
- The density of the block or perceived numbness by the patient is dependent on the concentration of local anesthetic ordered and volume
  - When using an epidural for pain control, lower concentrations are used to prevent motor block, which may otherwise present fall risk for a patient
    - Thorough neurologic examination of patients with lumbar epidurals should be done before allowing ambulation
    - Thoracic epidurals are not typically associated with weakness in the legs and should not preclude ambulation (also referred to as "walking epidurals")
      - However, if the spread of an epidural is too high, the patient may get numbness in the arms
      - Depending on local anesthetic concentration the patient may also experience weakness of the upper extremities or intercostal muscles and become short of breath
- Adverse effects
  - Expected adverse effects such as hypotension may also limit the dose of local anesthetic that can be used
  - Urinary retention is common with lumbar epidurals, though some patients may be able to urinate with the lower concentrations of local anesthetic often used for pain
  - Thoracic epidurals are less likely to be associated with urinary retention and use of a Foley catheter is not required
- Epidurals may have a simple continuous infusion rate or a defined intermittent bolus dose, or be programmed to have PCEA (patient-controlled epidural analgesia) allowing the patient to push a button to administer themselves a small bolus of medication through the epidural at a defined interval
  - If the patient has PCEA with opioid in their epidural, generally it is safest to avoid administering additional opioids through other routes
    - If pain control is not sufficient, opioid should be removed from the epidural and patient may receive additional opioids PO or IV
  - IV lidocaine infusions should not be given to patients receiving neuraxial anesthesia due to risk of local anesthetic toxicity
- Contraindications to neuraxial anesthesia include:
  - Patient refusal
  - Coagulopathy
    - Strict anticoagulation guidelines exist to minimize risk of epidural hematoma, which can result in paraplegia if not identified and treated rapidly^41,⁴²
  - Infection, either systemic or at site of insertion
  - Hemodynamic instability
    - Sympathectomy from epidural will predispose to hypotension
  - Transverse process, spine fractures, or other anatomic anomalies that impact ability to reliably predict the level of the spinal cord or access of epidural space based on tactile feedback using the loss of resistance technique
- Cautions
  - Monitor patients with epidural catheters for new severe back pain, changes in neurologic examination not explained by medications being infused through epidural, and redness or swelling at the epidural catheter insertion site
    - Patients who are unable to self-report or easily be monitored for symptoms related to epidural complications may not be appropriate for this treatment modality
Peripheral nerve blocks
- Ideal in management of a focal area of pain as they involve injecting local anesthetic either perineurally or in a plane where nerves are expected to be in order to reduce sensation in a specific distribution
- Peripheral nerve blocks achieve different goals by using different concentrations and doses of local anesthetics
  - A very dilute local anesthetic may just "take the edge" off of pain where a dense local anesthetic can achieve a complete numbness with motor block for a period of time (typically intended for surgical anesthesia rather than pain)
- Duration of a peripheral nerve block can be extended by:
  - Increasing the dose of local anesthetic (volume and/or concentration)
  - Inserting an indwelling catheter
    - Some institutions may have an option to send a patient home with an ambulatory infusion pump to continue using a catheter for several days
  - Adding pharmacologic adjuncts to the local anesthetic injected such as clonidine, dexmedetomidine, dexamethasone, or magnesium
    - Though these are usually given perineurally, there may still be some systemic absorption that could cause adverse effects such as hypotension or elevated blood glucose
  - Use of novel products such as liposomal bupivacaine, though evidence varies for different indications
- Contraindications include:
  - Patient refusal
  - Coagulopathy
    - Low-risk peripheral nerve blocks can still be performed if site is compressible and risks are outweighed by potential benefits^41,⁴²
  - Infection, either systemic or at site of insertion
  - Special considerations for specific blocks
    - Interscalene block causes hemidiaphragmatic paresis leading to possible desaturation in patients with impaired lung function
    - Concern for fall risk with sciatic or femoral nerve block (generally not appropriate to perform bilaterally in an ambulatory patient)
      - Recommend use of crutches
    - Mild hypotension following paravertebral blocks

Persistent or Recurrent Disease

Acute pain that persists beyond 3 months is considered chronic pain
Persistent postsurgical pain is common with estimates ranging from 10% to 50%⁴³
- Procedures associated with a greater risk of persistent postsurgical pain include:
  - Thoracotomy
  - Cardiac surgery
  - Sternotomy
  - Breast surgery
  - Limb amputation
  - Hernia repair
- Risk factors include:
  - Preoperative anxiety and/or depression
  - High level of catastrophizing
  - Preexisting pain before surgery
  - Significant acute pain in the first 3 to 4 postoperative days
  - Surgery involving division or prolonged retraction of nerves
  - Younger age
  - Female sex
  - Genetic susceptibility
The conversion of acute to chronic pain is a complex process involving both peripheral and central sensitization
- Identifying risk factors and employing a multimodal approach early on can help combat sensitization^44,⁴⁵
- Perioperative psychological interventions can be effective in reducing conversion to subacute and chronic pain

Admission Criteria

Inpatient admission for pain should be predicated on the underlying etiology and whether hospital admission is needed for treatment or additional workup
A select few patients may require inpatient admission if they are unable to achieve adequate relief with oral pain medications or there is concern for safety due to medication adverse effects

Special Considerations

Older Adults

Use the ADD protocol (assessment of discomfort in dementia) (Figure 2)⁴⁶ or other special assessment tools for patients with dementia
Older adults are more susceptible to adverse effects particularly from opioids, gabapentinoids, and NSAIDs
- Consider use of low potency opioids such as hydrocodone-acetaminophen as an oral agent or nalbuphine as an IV agent
- Avoid use of morphine due to reduced renal clearance in older patients
- Consider dose reductions of pain medications
Note that both pain itself and pain medications can contribute to delirium

Patients With Chronic Pain

When treating acute pain in patients with preexisting pain, determine the patient’s baseline pain level and functional status; it is unlikely you will be able to improve upon this during an acute pain situation
Ensure patients receive their home pain medications, including long-acting opioids
- Confirm with patient when they last took their medication before ordering
- For controlled substances, check the state prescription drug monitoring program and pharmacy records to confirm the patient’s prescription and compliance
- For patients taking multiple doses of tramadol daily, abruptly stopping may feel similar to withdrawal from an SSRI (selective serotonin reuptake inhibitor)⁴⁷
  - In this instance, tramadol can be scheduled and treated similarly to a long-acting opioid
- Buprenorphine products should be continued similarly to any other long-acting opioid, unless there has been a significant disruption in receiving it (48-72 hours)
  - If there has been a significant disruption, reinduction or a microinduction may be required to restart the medication and pain specialist consultation is appropriate
  - Full agonist opioids can be given to treat pain in a patient taking buprenorphine with good effect, contrary to prior understanding of buprenorphine⁴⁸
- For patients prescribed fentanyl or buprenorphine patches chronically, consider replacing the patch if it is unclear when it was last changed or if it may have been exposed to extreme temperatures affecting absorption (such as under a heated blanket in the operating room)
- Long-acting opioids should not be used for treatment of acute pain¹¹

Patients With Substance Use Disorder

Methadone
- Patients taking methadone for opioid use disorder should have methadone resumed after the dose has been confirmed with their clinic
  - Confirm with patient the last time they took methadone
  - If the dose is unable to be confirmed due to clinic hours, it is reasonable to start 30 mg PO daily, as this is a common starting dose for methadone⁴⁹
  - For inpatients, methadone can be given as a single daily dose or divided into every-6-hour or every-8-hour doses
    - Divided dosing may give some advantage in treatment of pain due to methadone’s 6-hour analgesic window and also allows for additional safety by allowing doses to be held in patients that are critically ill⁵⁰
    - Some patients may prefer once-daily dosing
  - The patient may need an increased dose of opioid for treatment of acute pain given opioid tolerance
Buprenorphine-naltrexone SL (sublingual)
- Patients taking buprenorphine-naltrexone SL for opioid use disorder should have the medication continued to prevent destabilization of addiction⁵¹
  - Buprenorphine-naltrexone prescriptions should be confirmed using the state prescription monitoring program and pharmacy records
  - Confirm with the patient when they last took their medication
    - If more than 48 to 72 hours has passed since the last dose and other full agonist opioids have been administered, resumption of moderate-high doses of buprenorphine can precipitate withdrawal; in this case, the patient will need to undergo another full induction or microinduction if receiving full agonist opioids
    - For patients on higher doses of buprenorphine and with history of difficult-to-control postoperative pain while taking buprenorphine, consider reducing the dose to 16 mg per day or less to optimize µ opioid receptor availability
  - Similar to methadone, dividing buprenorphine-naloxone into every-6-hour or every-8-hour dosing will take better advantage of the medication’s analgesic window
    - However, patients will still have analgesic benefit when the medication is at a steady state if dosed daily or twice daily (the typical dosing schedule for addiction management); patient preference should be considered
  - Pain can be adequately treated in patients taking buprenorphine despite prior assumptions that it cannot⁴⁸
    - A multimodal approach should be used as with any patient
    - Full agonist opioids can be successfully used to treat pain
      - Start at typical doses and increase based on effect, similar to any opioid tolerant patient
    - In very-high-risk patients consider additional buprenorphine-naloxone SL as an alternative to full agonist opioids
Patients with active opioid use disorder and not engaged in treatment
- Consider offering to start medication-assisted therapy
- Starting dose of methadone is typically 30 mg PO daily (methadone solution)
  - Give all at once if patient is acutely experiencing withdrawal; otherwise can give in divided doses such as 10 mg PO every 8 hours⁵²
  - Some hospital systems may be able to help facilitate intake appointments at methadone clinics after discharge
    - If the patient is unable to be established at a methadone clinic after discharge, do not prescribe methadone tablets
      - Prescribing methadone for MOUD (medication for opioid use disorder) outside a treatment center is against the law
    - If the patient will not be able to access a methadone clinic after discharge, buprenorphine may be a better option for MOUD as it may be prescribed and dispensed from a regular pharmacy
- Buprenorphine products can be initiated through traditional induction if the patient experiences withdrawal or microinduction if receiving other opioid for acute pain
  - As a patient’s dose of buprenorphine increases, their use of full agonist opioids for acute pain should reduce
Naltrexone
- Given the interaction between naltrexone and opioids, patients taking naltrexone for alcohol use disorder or opioid use disorder should pause this medicine while requiring opioid medications for acute pain and discuss when to resume it with their prescriber⁵³
Methamphetamine use disorder
- Patients that regularly use methamphetamines can be challenging to treat while experiencing methamphetamine withdrawal
- Reduced doses of pain medications may be required due to sedation

Pregnant Patients

Acetaminophen should be considered a first line agent
NSAIDs can be used in the first and early second trimester of pregnancy but should be avoided after 20 weeks due to risk of kidney problems resulting in low amniotic fluid⁵⁴
Limited short-term use of opioids is acceptable, though it can cause respiratory depression
IV ketamine is contraindicated in treatment of acute pain in pregnancy, though it can be used as part of an anesthetic during delivery⁵⁵
The safety of IV lidocaine in pregnancy is unclear due to limited studies in the population⁵⁶
Regional anesthesia techniques are safe and often preferable to systemic therapies⁵⁷
Nonpharmacologic therapies should be encouraged such as:
- Acupuncture
- Massage
- Physical therapy (including pelvic floor physical therapy)
- Hot and cold packs
- Meditation/mindfulness

Breastfeeding Patients

Acetaminophen and NSAIDs should be considered as first line agents
Use of opioids while breastfeeding can cause infant drowsiness and central nervous system depression
- Low-dose morphine may be preferable to other opioids⁵⁸
Avoid meperidine⁵⁹
- Infants have an impaired metabolism and higher oral bioavailability than adults
- The active metabolite normeperidine causes more central nervous depression in newborns than in adults
Avoid tramadol⁶⁰
- Ultrarapid metabolism to M1 (O-desmethyltramadol) can cause life-threatening respiratory depression in the infant
Avoid codeine⁶⁰
- Ultrarapid metabolism to morphine can cause life-threatening respiratory depression in the infant
Nonpharmacologic therapies should be encouraged such as:
- Acupuncture
- Massage
- Physical therapy (including pelvic floor physical therapy)
- Hot and cold packs
- Meditation/mindfulness

Critically Ill Patients

Communication barriers such as sedation, delirium, or presence of airway devices make assessment of pain challenging in critically ill patients
- CPOT (Critical-Care Pain Observation Tool) uses observations of facial expressions and body movement to extrapolate a level of pain (Table 8)⁶¹
Difficulty in assessment of adverse effects of treatment in intubated/sedated patients will impact treatment options
- Peripheral nerve blocks such as erector spinae or serratus anterior have a lower risk profile than epidural analgesia
- Symptoms of local anesthetic toxicity may not be detected early on during lidocaine infusion
- Opioids may be given more liberally while a patient is intubated as the airway is protected
  - Explore other options when nearing extubation
- Careful consideration of risks versus benefits should be given on a case-by-case basis

Table 8. CPOT.
Indicator	Description	Score
Facial expression	No muscular tension observed	Relaxed, neutral	0
	Presence of frowning, brow lowering, orbit tightening, and levator contraction	Tense	1
	All of the above facial movements plus eyelid tightly closed	Grimacing	2
Body movements	Does not move at all	Absence of movements	0
	Slow, cautious movements; touching or rubbing the pain site; seeking attention through movements	Protection	1
	Pulling tube, attempting to sit up, moving limbs/thrashing, not following commands, striking at staff, trying to climb out of bed	Restlessness	2
Muscle tension Evaluation by passive flexion and extension of upper extremities	No resistance to passive movements	Relaxed	0
	Resistance to passive movements	Tense, rigid	1
	Strong resistance to passive movements, inability to complete them	Very tense or rigid	2
Compliance with the ventilator (intubated patients) OR Vocalization (extubated patients)	Alarms not activated, easy ventilation	Tolerating ventilator or movement	0
	Alarms stop spontaneously	Coughing but tolerating	1
	Asynchrony: block ventilation, alarms frequently activated	Fighting ventilator	2
	Talking in normal tone or no sound	Talking in normal tone or no sound	0
	Sighing, moaning	Sighing, moaning	1
	Crying out, sobbing	Crying out, sobbing	2
Total, range			0-8

Follow-Up

Monitoring

Vital sign monitoring
- Elevated heart rate and blood pressure are consistent with a stress response during acute pain
  - However, it is important to not assume these elevations are due to pain
  - Also note that pain can be present without these
Monitoring for resolution of acute pain can be tracked by:
- Participation in therapies
- Duration and quality of sleep
- Trending pain scores
- Change in usage of PRN pain medications

Complications

Poorly controlled acute pain increases risk of:
- Development of chronic pain⁶²
- Delay in recovery or hospital discharge⁶³
- Delirium⁶⁴

Prognosis

Expected course of acute pain is dependent on etiology
Acute low back pain
- Meta-analysis of acute low back pain revealed significant improvement within the first 6 weeks followed by slower improvement⁶⁵
Surgical procedures can be categorized into:⁶⁶
- Expected rapid recovery
  - NSAIDs and/or acetaminophen and nonpharmacologic therapies may be sufficient
  - If opioids are required, 3 days or less are recommended
  - Examples include oral surgery, laparoscopic appendectomy, inguinal hernia repair, carpal tunnel release, thyroidectomy, breast biopsy/lumpectomy, meniscectomy, vaginal hysterectomy, among others
- Expected medium-term recovery
  - NSAIDs and/or acetaminophen and nonpharmacologic therapies are first line
  - Opioids should be prescribed for 7 days or less for severe pain
    - Exceptional cases may warrant greater than 7 days of opioid treatment, though patients should be reevaluated by surgeons in the weeks following surgery and taper off within 6 weeks after surgery
  - Examples include anterior cruciate ligament repair, rotator cuff repair, laminectomy, open or laparoscopic colectomy, open small bowel resection, laparoscopic hysterectomy, simple mastectomy, cesarean section, among others
- Expected longer-term recovery
  - NSAIDs and/or acetaminophen and nonpharmacologic therapies are first line
  - Opioids should be prescribed 14 days or less for severe pain
    - Exceptional cases may warrant greater than 14 days of opioid treatment, though patients should be reevaluated by surgeons prior to refilling opioids and taper off within 6 weeks after surgery
  - Examples include lumbar fusion, knee/hip replacement, abdominal hysterectomy, modified radical mastectomy, ileostomy/colostomy creation or closure, thoracotomy, among others

Referral

Consult anesthesiology or a specialized pain service for:
- Inadequately controlled pain
- High risk of inadequately controlled pain⁶⁷
  - History of long-term opioid therapy
  - History of substance use disorder
- Consideration of regional anesthesia
- Management of specialized medications such as IV ketamine or IV lidocaine
Consider referral to a chronic pain specialist when:
- Acute pain is not resolving within the expected time course despite resolution of underlying etiology
- Concern for development of CRPS (complex regional pain syndrome)
  - Classically this includes pain out of proportion to the inciting event and no other diagnosis better explains the signs and symptoms
  - Symptoms may include:
    - Hyperesthesia or allodynia
    - Asymmetry in temperature or sweat patterns
    - Decreased range of motion and/or motor dysfunction
    - Edema
    - Trophic changes of hair/nails/skin
  - Early treatment of CRPS will improve prognosis⁶⁸
Consider referral to an addiction medicine specialist if there is concern for opioid misuse or dependency

Author Affiliations

Katherin Peperzak, MD
Assistant Professor, Medical Director Center for Pain Relief at UWMC-Roosevelt
Anesthesiology & Pain Medicine
University of Washington

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