Acute Pain

For Pharmacy Examining Board of Canada (PEBC) MCQ and EE Preparation

Introduction

Acute pain is a common and often distressing experience for patients. It is temporary, ranging from a few minutes to several weeks, and can result from injuries, surgery, or medical conditions. Prompt recognition, accurate assessment, and appropriate treatment of acute pain are crucial to prevent negative physiological and psychological outcomes. This chapter will provide an overview of acute pain management strategies, both pharmacologic and non-pharmacologic, tailored for candidates preparing for PEBC exams.

Goals of Therapy

The main goals in managing acute pain are:

1. Recognizing that the patient is in pain.
2. Relieving the pain while the underlying cause is identified and treated.
3. Minimizing adverse physiological and psychological outcomes associated with untreated pain.
4. Using appropriate analgesic interventions based on the severity of the pain.

Pain Assessment

Accurate pain assessment is crucial for effective pain management. Pain can be assessed using:

●     Verbal Numeric Rating Scale (NRS): Patients rate pain on a scale of 0 (no pain) to 10 (worst possible pain). This is suitable for patients aged ≥6 years.

●     Wong-Baker Faces Pain Rating Scale: Ideal for children aged 3-6 years.

●     PAINAD: A tool used to assess pain in adults with cognitive impairment.

Therapeutic Choices for Acute Pain Management

Non-Pharmacologic Management

●     Immobilization: Stabilizing a fracture or affected limb to reduce pain.

●     Dressing: Apply dressings to burns or wounds to alleviate discomfort.

●     Cold/Heat Application: Ice packs for acute injury; heat packs for muscle relaxation.

●     Distraction Techniques: Visualization and distraction can help reduce the perception of pain, especially in children.

Pharmacologic Management

1. Non-Opioid Analgesics

●     Acetaminophen: Effective for mild to moderate pain. It has a good safety profile with fewer adverse effects compared to NSAIDs but lacks anti-inflammatory properties.

●     NSAIDs: Provide both analgesic and anti-inflammatory effects. Ibuprofen, naproxen, and ketorolac are commonly used. Caution is needed with long-term use due to potential GI, renal, and cardiovascular adverse effects.

○     For example, Ibuprofen 400 mg is more effective than acetaminophen 650 mg and can be used in children (10 mg/kg).

2. Opioid Analgesics

Opioids are recommended for moderate to severe pain or when non-opioid medications are ineffective. They can be administered orally, parenterally, or through patient-controlled analgesia (PCA).

●     Morphine is the gold standard opioid, with predictable pharmacokinetics and a favorable safety profile.

●     Hydromorphone and fentanyl are alternatives, with hydromorphone being more potent and often used for severe pain.

●     Codeine is discouraged due to its variable metabolism (ultra-rapid metabolizers risk respiratory depression).

Algorithm for Acute Pain Management

The following table presents the algorithm based on the image provided, summarizing the step-by-step approach to acute pain management:

Step	Action
Pain Recognized	Recognize the patient is in pain and assess the level using the NRS scale.
Non-Pharmacologic Measures	Apply non-pharmacologic measures such as immobilization, cold/heat application, and distraction.
Mild/Moderate Acute Pain (NRS < 7)	Administer acetaminophen or NSAIDs orally or rectally. Reassess after 1 hour.
Effective	Reassess every 4 hours and continue therapy if effective for ≥4 hours.
Ineffective	Switch to an oral opioid such as morphine. Reassess after 1 hour. If still ineffective, consider NSAID combination or escalate therapy.
Severe Acute Pain (NRS ≥ 7)	Administer parenteral NSAID (e.g., ketorolac) or IV opioid (e.g., morphine). Reassess after 1 hour.
Effective for ≥2 hours	Continue therapy and reassess every 2–4 hours.
Ineffective for <2 hours	Titrate opioid dose or consider a continuous infusion of morphine.

Therapeutic Notes for Exam Preparation

●     First-Line Therapy for Mild to Moderate Pain: Acetaminophen or NSAIDs. Acetaminophen is preferred when anti-inflammatory effects are not required.

●     First-Line Therapy for Severe Pain: Parenteral opioids like IV morphine or fentanyl.

●     Combination Therapy: Non-opioid analgesics (e.g., acetaminophen + NSAID) can be combined with opioids for additive effects.

●     Opioid Use: Use the lowest effective dose to minimize adverse effects (respiratory depression, sedation, constipation).

●     Opioid Rotation: When switching opioids, use caution due to incomplete cross-tolerance. Reduce the dose by 50% when initiating a new opioid.

●     NSAIDs: Avoid in patients with renal failure, heart failure, or peptic ulcer disease. Consider GI protection (PPI or misoprostol) for high-risk patients.

 

Important Points for PEBC Exams

1. Pain Scales: Know the appropriate use of pain scales like NRS, Wong-Baker Faces, and PAINAD.
2. First-Line Treatment: Acetaminophen and NSAIDs for mild/moderate pain; IV opioids for severe pain.
3. Adverse Effects of NSAIDs: Gastrointestinal bleeding, renal impairment, and cardiovascular risks.
4. Opioid Side Effects: Constipation, respiratory depression, sedation, and dependence.
5. Pain Management in Children: Avoid codeine due to variable metabolism and risk of respiratory depression.
6. Opioid Rotation: Understand how to adjust doses when switching opioids due to incomplete cross-tolerance.
7. Non-Pharmacologic Techniques: Immobilization, heat/cold application, and distraction should be part of the pain management plan.
8. Ketorolac: A potent NSAID used parenterally but should not be used for more than 5 days to avoid adverse effects.