CHAPTER 18 Pain Management
I. DefinitionPain is a common condition that manifests as many different forms and severities. Pain is defined as an unpleasant sensory and emotional experience associated with damage to body tissues, including organs, bones, and muscles. Acute pain occurs after tissue injury and often resolves soon after the body has healed. Chronic pain occurs either from continual damage or constant stimulation of nerve fibers lasting at least 6 months. The cause of some chronic pain may not be known. The treatment of pain depends upon the causes of the pain and the individual’s tolerance of pain.
II. Types of Pain The different types of pain include acute pain, chronic pain, nerve pain, nociceptive pain, and psychogenic pain.
A. Acute pain: results from injury to tissues and/or inflammation. Acute pain generally has a sudden onset. For example, after trauma or surgery, acute pain may be accompanied by anxiety or emotional distress.
B. Chronic pain: Pain signals keep firing in the nervous system for weeks, months, even years. Initial injuries, such as an infection, sprained back, or sprained muscle, may cause acute pain that may lead to chronic pain. There may be an ongoing cause of pain, such as in back pain, arthritis, diabetes (diabetic neuropathy), or cancer.
C. Nerve pain (neuropathic pain): pressure or damage to nerves or the spinal cord. Nerve pain can be caused by tumors; injury, such as during surgery or falls; chemical damage, such as with mercury, lead, chemotherapy, and radiation; or viruses, such as herpes zoster (shingles or chicken pox).
IV. Chronic Pain Control
VI. Patient Assessment
VII. Patient Management
VIII. Pharmacologic Therapies
A. Acetaminophen (paracetamol; tylenol)
1. Mechanism of action: not fully understood at this time; possibly centrally acting; derivative of p-aminophenol; analgesic
2. Maximum dose 4 g/day for adults (lower maximum dosages currently under consideration by Food and Drug Administration [FDA]); less with hepatic dysfunction and/or alcohol use
B. Nonsteroidal anti-inflammatory drugs (NSAIDs) (Table 18-1)
1. Mechanism of action: nonspecific inhibition of cyclooxygenase (COX)-2 and COX-1 receptors, decreasing prostaglandins produced by the arachidonic acid cascade in response to noxious stimuli, thereby decreasing the number of pain impulses received by the central nervous system (CNS)
2. Use lowest effective dose for shortest possible duration; OTC NSAID not to exceed 10 days unless a physician directs otherwise
3. Caution: Avoid in patients with recent coronary artery bypass graft surgery (CABG). Caution in bleeding disorders, hepatic or renal disease, GI disorders; women who are pregnant or lactating or who are trying to conceive
C. Aspirin
2. Mechanism of action: irreversibly inhibits COX-1 and COX-2, decreasing prostaglandins produced by the arachidonic acid cascade in response to noxious stimuli, thereby decreasing the number of pain impulses received by the CNS
4. Caution: bleeding disorders, hepatic and/or renal disease, GI disorders, use in children, pregnancy, fertility, lactation
D. COX-2 inhibitors (a subset of NSAID class) (Table 18-2)
1. Mechanism of action: selectively inhibits the activity of the enzyme COX-2, resulting in a decreased prostaglandin production, thereby decreasing the number of pain impulses received by the CNS
3. Common side effects: peripheral edema, abdominal pain, diarrhea, dyspepsia, flatulence, nausea, back pain, dizziness, headache, insomnia, pharyngitis, rhinitis, sinusitis
5. Avoid in patients with recent coronary artery bypass graft surgery (CABG), creatinine clearance <30 mL/min
E. Narcotic analgesics (Table 18-3)
1. Overview
a. Mechanism of action: binds to opiate receptors in the CNS causing inhibition on ascending pain pathways thereby altering the perception of and response to pain
2. Morphine
5. Synthetic and semisynthetic narcotics
a. Oxycodone (OxyContin)
b. Meperidine (Demerol)
d. Fentanyl (Actiq, Duragesic, Fentora)
5) No maximum dose: must titrate up slowly to lessen side effects, especially respiratory depression
3. Drugs used in treatment of narcotic dependency
a. Methadone (Dolophine)
b. Buprenorphine (Suboxone and Subutex)
1) Both products are available as 2-mg and 8-mg sublingual (under the tongue) tablets; buprenorphine injection is also available.
2) Mechanism of action: produces effects typical of both pure mu agonists and partial agonists depending on dose and pattern of use
F. Narcotic antagonists
G. Antidepressants used for pain management
H. Anticonvulsants used for pain management
2. Liver function tests (LFT) should be obtained at baseline and throughout use with many of these drugs (e.g., phenytoin, valproic acid, carbmazepine).
I. Local anesthetics
Table 18-1 Nonsteroidal Anti-inflammatory Drugs (NSAID)
| NSAID | Usual Oral Adult Doses | Comments |
|---|---|---|
| Ibuprofen (Motrin) | 200–400 mg PO q4–6h prn | Maximum 1200 mg/day (OTC); 3200 mg/day (Rx) |
| Naproxen (Aleve, Naprosyn, Anaprox) | 200–400 mg PO (initial dose), followed by 200 mg PO q8–12h | Maximum 600 mg/day (OTC); 1000 mg/day (Rx) |
| Diclofenac (Cataflam, Voltaren) | ||
| Etodolac (Lodine) | Immediate release 200–400 mg PO 6–8h prn | Maximum 1200 mg/day |
| Fenoprofen (Nalfon) | 200 mg PO every 4–6h prn | |
| Flurbiprofen (Ansaid) | Postoperative/dental pain 50 mg PO 4–6h prn | |
| Ketoprofen (Orudis, Orudis KT, Oruvail) | 12.5 mg PO 4–6h prn, may initiate with 25 mg | Maximum 75 mg/day (OTC); 300 mg/day (Rx) |
| Indomethacin | 75–150 mg/day PO in 3 or 4 divided doses for 7–14 days | |
| Nabumetone (Relafen) | 1000–2000 mg/day PO divided 1 or 2 times | |
| Ketorolac (Toradol) | Only used acutely following IV or IM dosing; give 20 mg × 1 dose, then 10 mg PO 4–6h prn | Maximum 40 mg/day PO; maximum combined duration of parenteral and oral routes is 5 days; if ≥65 years of age OR weight <50 kg do not exceed 10 mg PO 4–6h prn |
| Piroxicam (Feldene) | 20 mg/day PO | |
| Sulindac (Clinoril) | 150–200 mg PO twice a day | Maximum 400 mg/day |
Table 18-2 COX-2 Inhibitors—Adult Recommended Dose
| COX-2 Inhibitors | Dose |
|---|---|
| Celecoxib (Celebrex) |
Table 18-3 Actions of Opiate Receptors
| Opiate Receptor | Action |
|---|---|
| Mu-1 | Analgesia |
| Mu-2 | |
| Delta | Analgesia |
| Sigma | |
| Kappa | |
| Epsilon | Analgesia |
PATIENT PROFILE
Allergies: Codeine (rash, itching)
Alcohol use: Frequent, drinks several beers per day
Current Medications: No regular medications at present time at home.
Postoperative medications include:
Lorazepam 1 mg IV q4–6h as needed (PRN) for anxiety
PATIENT PROFILE QUESTIONS
1. The pain management team decides that initial pain management will be in the form of patient-controlled analgesia (PCA) because this will likely provide the best pain control in the immediate postoperative period. Which medications would be appropriate to use for DB in a hospital setting using a PCA device?
2. The pain team decides that morphine will be used for the initial PCA regimen. Which of the following represents a practical initial PCA order for DB?
a. After the initial loading dose for acute pain control, begin morphine PCA at 1 mg bolus with a 10-minute lockout interval.
b. After the initial loading dose for acute pain control, begin morphine PCA at 10 mg bolus with an 8-minute lockout interval.
3. After several weeks, DB is taking food well and recovering nicely despite his injuries. He still needs a significant amount of medication to manage his pain, especially during rehabilitation sessions. He will be released to home with a prescription for Percocet 5/325, 1 tablet PO q6h as needed for pain and a prescription for ibuprofen 400 mg PO q6h for inflammation and pain. What should patient counseling for DB regarding the Percocet prescription include?
II. DB should avoid the use of alcohol because this can increase the side effects of Percocet such as dizziness, drowsiness, and difficulty breathing, or the risk for liver problems.
III. DB should not exceed the recommended dosage for Percocet and not take additional acetaminophen (e.g., Tylenol) because this could result in acetaminophen overdosage.
REVIEW QUESTIONS
(Answers and Rationales on page 369.)
3. Which of the following anesthetic/partition coefficient/minimum alveolar concentration would have the fastest onset of action?
4. Which of the following anesthetic/partition coefficient/minimum alveolar concentration would have the least effect on uterine smooth muscle?
5. Which of the following anesthetic/partition coefficient/minimum alveolar concentration would have the highest potency?
6. Which of the following anesthetic/partition coefficient/minimum alveolar concentration would have the lowest potency?
14. Which of the following is a neuromuscular blocking agent that may cause muscarinic side effects?
28. Which of the following anesthetic/partition coefficient/minimum alveolar concentration should be avoided in epileptic patients?
29. A 36-year-old man is taken to the emergency department with respiratory depression. Which of the following drugs is a likely culprit?
32. Which of the following anesthetic/partition coefficient/minimum alveolar concentration is not used due to nephrotoxicity?
39. Which of the following is the most common pulmonary complication associated with opioid ingestion?
46. Which of the following can be used to prevent abstinence withdrawal syndrome in heroin-addicted patients in the inpatient setting?
56. A patient undergoing a dental procedure should stop aspirin therapy for how many days before his appointment?
62. The Pain Ladder, a widely accepted three-step approach to implementing the three categories of pain medication, was developed by the?
63. Which of the following anesthetic/partition coefficient/minimum alveolar concentration is most likely to produce hepatitis?
64. Which of the following has minimal effects on the cardiovasculature and has depressant CNS effects?
77. A ceiling dose is?
