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THE MORNING REPORT

The Best in FOAM Education

  • Christopher Loh, MD

Approach to Pain Medication in the ED

General Tips

  • Pain is the most common presentation in the ED (75-80%)

  • Pain is a symptom, NOT a diagnosis

  • Pain is unique to the individual and is influenced by a multitude of factors to include culture, sex, age, severity of injury, co-morbidities, etc.

  • Titrate treatment to patient's functionality and pain perception

  • Vital signs cannot be used to accurately assess pain in the ED

  • Achieving analgesia with minimal side effects is important and a nuanced skill

  • Goal of treatment is not complete eradication of pain, but to reduce to acceptable levels for safe discharge or bridge to admission

  • Reassess pain frequently to determine analgesia efficacy

  • avoid relying on personal impressions on suspected pain ratings

Acetaminophen (Tylenol)

  • MOA: COX-3 inhibitor

  • Duration: 4-6hrs

  • Dosing

    • PO: 325mg, 500mg, 650mg, 975mg, 1,000mg every 6hrs

    • IV: 1000mg every 6hrs

    • PR: 650mg every 6hrs

  • Antipyretic and analgesic but NO peripheral anti-inflammatory properties

  • 2017 study found acetaminophen & Ibuprofen is as efficacious as opioid containing combinations for musculoskeletal pain

  • In mild-moderate pain, acetaminophen is the first line analgesic

  • safe in pregnancy and lactation (Category B 1st - 3rd trimester)

  • Maximal daily dose 4,000mg/d or 3,000mg/d in patients with liver disease or the elderly

NSAIDs

  • MOA: nonselective COX-1, 2 inhibitors reducing prostaglandins

  • Common medication dosing

    • Ibuprofen

      • PO: 200mg, 400mg, 600mg every 6hrs

    • Ketorolac

      • IV: 15mg, 30mg every 6hrs

    • Naproxen

      • PO: 500mg every 12hrs OR 250mg every 6-8hrs

  • Evidence to suggest Ibuprofen maximal pain efficacy dose is 400mg. Higher doses do not improve pain efficacy, but increases risks for adverse effects

Opioids

  • MOA: agonistic effects on Mu opioid receptors in central and peripheral nervous system

  • Morphine:

    • IV: 0.1mg/kg every 4-6hrs

    • PO: 10mg every 4-6hrs

    • Adverse effects: Hypotension, respiratory depression, sedation, histaminergic reaction, constipation

    • Metabolites excreted by the kidney, so will cause accumulation in renal failure patients

  • Fentanyl:

    • IV: 1mcg/kg every 1-2hrs.

    • Hemodynamically stable

    • Adverse effects: Sedation, Constipation, rigid chest syndrome

    • metabolized in liver, can cause accumulation in hepatic disease

  • Hydromorphone

    • IV: 0.015mg/kg every 4-6hrs

    • Adverse effects: Hypotension, respiratory depression, sedation, euphoria, constipation, histaminergic reaction

  • Oxycodone/Hydrocodone:

    • PO: 5-10mg every 4-6hrs

    • Adverse effects: Hypotension, respiratory depression, sedation, histaminergic reaction, constipation



IV

PO

IV/PO ratio

Equivalence dose ratio Morphine:X

Morphine

10mg

30mg

1:3

n/a

Hydromorphone

1.5mg

7.5mg

1:5

IV 7:1; PO 4:1

Fentanyl

0.1mg (100mcg)

n/a

n/a

IV 300:1

Oxycodone

n/a

20mg

n/a

PO 3:1

Hydrocodone

n/a

30mg

n/a

PO 1:1


Sodium Channel Blockers

  • MOA: Inhibits sodium channels and inhibits glutamate release

  • Lidocaine

    • Injection 1%, 2%

    • topical 4%, 5%

    • maximal safe dose 4-5mg/kg (5-7mg/kg with epinephrine)

  • Bupivacaine

    • injection 0.25%, 0.5%, 0.75%

    • Maximal safe dose 2-3mg/kg

  • Ropivacaine

    • Injection 0.2%, 0.5%, 1%

    • Maximal safe dose 2-3mg/kg

  • Adverse effects

    • Allergic Reaction: typically in amide compounds (does not cross react to ester compounds)

    • Local Anesthetic Systemic Toxicity (LAST)

      • Cardiovascular effects: bradycardia, hypotension, AV block, decreased cardiac output, leading to cardiac and pulmonary arrest

      • Neurologic effects: numbness, lightheadedness, visual and auditory disturbances, convulsions, coma

Dopamine Receptor Antagonists

  • MOA: antagonism to D2, D3 receptors

  • sometimes used to treat acute headaches, gastroparesis, cyclic vomiting syndrome, cannabinoid-induced hyperemesis

  • Metoclopramide

    • IV/PO: 5mg, 10mg, 20mg q4-12hrs

    • Max dose 40mg/d

  • Prochlorperazine

    • IV/IM/PO: 10mg q6hrs

    • Max dose 40mg/d

  • Chlorpromazine

    • IV/PO: 10mg q6hrs

    • Max dose: 25mg/d

  • Haloperidol

    • IV/IM/PO: 5-10mg q4hrs

  • Droperidol

    • IV/IM 1.25-10mg q1-2hrs

  • Adverse effects: Cardiac arrhythmia (QT prolongation), Extrapyramidal Syndromes, Constipation, Hypotension, Dry mouth

Dexmedetomidine

  • MOA: alpha 2 adrenergic receptor agonist dampening CNS sympathetic pathways

  • Dose

    • Bolus: 0.5-1 mcg/kg

    • Infusion: 0.4-1.4 mcg/kg/hr

  • Adverse effects: Hypotension, Bradycardia

Ketamine

  • MOA: NMDA receptor antagonist

  • Pain/subdissociative dose

    • Bolus: 0.1-0.5mg/kg

    • Infusion: 0.1-0.2mg/kg/hr

  • Adverse effects: agitation, emergence reaction

Anticonvulsants

  • MOA: sodium channel inhibitors

  • Gabapentin

    • PO: 100mg TID, titrated up to 1,200mg TID

    • Max dose: 3,600mg/d

  • Pregabalin

    • PO: 50-75mg, titrated up to 300mg

    • Max dose: 600mg/d

  • Adverse effects: fatigue, dizziness, ataxia, thrombocytopenia, angioedema, rhabdomyolysis

Clinical Pearls: Back Pain

  • Back pain leads to more disability than any other condition (depression, stress, exacerbation of underlying conditions)

  • Pain recurs in approximately 70% of patients treated in the ED

  • 1st line treatments: NSAIDs, trigger point injections, topical lidocaine, muscle-relaxants

  • 2nd line agents: Opioids

  • Resume activity as soon as possible

  • Recent systematic review and meta-analysis found NSAIDs resulted in a small but clinically significant improvement in back pain with an NNT = 6 (95% CI 4-10) to achieve clinically important pain reduction over placebo. NSAIDs were also shown to increase the risk of GI adverse events by 2.5x (95% CI 1.2-5.2)

  • Meta-analysis assessing acetaminophen for low back pain resulted in no difference in pain reduction between paracetamol (4g/d) and placebo at 1w, 2w, 4w, 12w for back pain reduction. Additionally, paracetamol did not affect quality of life, function, global impression of recovery, and sleep quality for all included periods.

  • 2017 ACP/APS joint recommendations indicate that acetaminophen, either as mono-therapy or combined with NSAIDs, is not effective for lower back pain.

  • Opioid combination analgesics (acetaminophen-oxycodone) were no more effective than NSAIDs alone for acute musculoskeletal pain relief, with the opioid combinations being associated with increased adverse effects

  • Research shows that those patients who received greater than a one-week prescription for opioids were twice as likely to have continued work-related disability at one-year follow-up.

  • Several SMRs have been shown to be superior to placebo in short-term pain reduction associated with acute, non-radicular back pain.

  • Due to lack of efficacy over NSAIDs alone as well as high risk of adverse effects, SMRs should be limited to patients who cannot tolerate NSAIDs or have not reported sufficient relief with NSAIDs.

  • If provider Discretion indicates that the benefit outweighs the risks, a short 2 to 3 day prescription with a full patient discussion regarding patient anticipated side effects should be considered

  • Benzodiazepines (diazepam) as an NSAID adjunct offers no improvement in functional outcomes or pain at one week and three months follow-up compared to NSAIDs alone

  • Use of benzodiazepines for acute back pain must further be weighed against the adverse effects.


Christopher Loh, MD


References

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  • Friedman BW, Conway J, Campbell C, Bijur PE, John Gallagher E. Pain One Week After an Emergency Department Visit for Acute Low Back Pain Is Associated With Poor Three-month Outcomes. Acad Emerg Med. 2018;25:1138-1145.

  • Qaseem A, Wilt TJ, McLean RM, Forciea MA, Clinical Guidelines Committee of the American College of P. Noninvasive Treatments for Acute, Subacute, and Chronic Low Back Pain: A Clinical Practice Guideline From the American College of Physicians. Ann Intern Med. 2017;166:514-530.

  • Chou R, Qaseem A, Snow V, et al. Diagnosis and treatment of low back pain: a joint clinical practice guideline from the American College of Physicians and the American Pain Society. Ann Intern Med. 2007;147:478-491.

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  • Tisdale SA, Jr., Ervin DK. A controlled study of methocarbamol (Robaxin) in acute painful musculoskeletal conditions. Curr Ther Res Clin Exp. 1975;17:525-530.

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