1 Define acute pain

Pain is defined as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” Acute pain refers to pain of short duration (<3 months), usually associated with surgery, trauma, or an acute illness. Acute pain differs from chronic pain because:

Its cause is usually known.

It is usually temporary and located in the area of trauma or damage.

It resolves spontaneously with healing.

2 Why has acute pain been undertreated?

There are numerous reasons acute pain is typically undertreated. Physicians get very little education regarding pain management during the course of medical school and residency training. Many providers overestimate the risks associated with the use of opioids, such as respiratory depression and addiction. Health care providers are also often afraid of scrutiny from regulatory boards that they believe may result from regularly prescribing opioid narcotics. In reality, the fact that poorly treated pain may result in higher morbidity and mortality rates has become appreciated only recently. There is now a greater emphasis being placed on not undertreating pain; lawsuits have successfully been brought against physicians for not providing enough pain medication. Pain is now considered the fifth vital sign.

3 How is pain assessed?

Pain is subjective and cannot be measured even with the most sophisticated medical equipment. Changes in vital signs such as blood pressure or heart rate correlate poorly with the degree of pain control.

The magnitude of pain and the response to treatment can be monitored in several ways. A visual analog scale may be used in which the patient chooses a mark on a 10-cm line corresponding with the perceived amount of pain being experienced. Scales using color (from blue for minimal pain through violet hues to bright red for maximal pain) or numbers (from zero for no pain through ten for maximal pain) have been devised for adults (Figure 77-1). A scale of 10 faces, ranging from very happy to very sad, can be used in young children. The child points to the face matching the way he or she feels. Verbal descriptive scales such as the McGill Pain Questionnaire are useful both for clinical and research purposes. Functional ability is also a useful measure of pain. In some patients, especially those who also have chronic pain, assessing ability to perform regular functions such as activities of daily living, performing at work, or ability to participate in leisure activities may be more useful than collecting pain scores. In a hospital setting the number of times a patient spontaneously leaves the room may provide a more accurate assessment than pain scores. Pain scores with activity may be a more sensitive measure of analgesia because it is easier to control pain at rest. The pain scale can be used to ensure that an intervention such as an increased dose of opioids is effective in decreasing the patient’s pain.

Figure 77-1 Pain scales for children and adults.

(From Wong D, Whaley L: Clinical manual of pediatric nursing, St. Louis, 1990, Mosby.)

4 What medications are useful in treating acute pain?

The medications useful in treating acute pain are similar to those used in treating other types of pain. The World Health Organization analgesic ladder developed for treating patients with cancer pain also provides a useful approach to treating acute pain (Figure 77-2). At the lowest level (mild pain), nonopioid analgesics such as nonsteroidal antiinflammatory drugs (NSAIDs) (e.g., ibuprofen or acetaminophen) are useful. Such drugs have an analgesic ceiling; above a certain dose no further analgesia is expected. For moderate pain compounds combining acetaminophen or aspirin with an opioid are useful. The inclusion of acetaminophen limits the amount of such agents that should be used within a 24-hour period because toxic accumulations can occur. The next step to consider would be adding an agent such as tramadol. Tramadol has a dual mechanism of action as a weak μ-opioid agonist and a weak inhibitor of reuptake of norepinephrine and serotonin. Care should be taken when concurrently prescribing with selective serotonin reuptake inhibitors since there is a potential increased incidence of serotonin syndrome (although there are very few reported cases). With severe levels of pain an opioid such as morphine or hydromorphone is a better choice; such opioids have no analgesic ceiling. Most postoperative or trauma patients initially respond better to morphine or other opioids. Intravenous agents are usually faster, and patients report more satisfaction with analgesia after surgery or trauma. By the time the patient is eating and ready for discharge, opioid-acetaminophen agents or NSAIDs are often adequate.

Figure 77-2 World Health Organization analgesic ladder.

5 Do all types of pain respond equally to medication containing opioids?

Not all types of pain respond equally to the same medication. Opioid analgesics are helpful in controlling somatic or visceral pain. Bone pain may be helped partially by opioids. However, NSAIDs and steroids are highly effective in treating bone pain. The combination of NSAIDs and opioids is synergistic in controlling pain. Neuropathic pain, often described as pain with a burning, hyperesthetic quality, responds to a diverse group of drugs, including antidepressants (amitriptyline), anticonvulsants (carbamazepine or gabapentin), antiarrhythmics (mexiletine), muscle relaxants (baclofen), and α-adrenergic agonists (clonidine). Opioids may also be helpful. Frequently pain control is improved after 1 to 2 days of using adjuvant drugs. Alternative medications may also help to control somatic or visceral pain. Drugs that control pain by different mechanisms may be synergistic when used together (such as NSAIDs and opioids). By using lower doses of two different agents, the patient may have good pain control with fewer side effects. Another option for mild to moderate pain is use of topical agents such as patches impregnated with lidocaine (Lidoderm) or diclofenac (Flector). In addition, topical gels or ointments can be considered, including 5% lidocaine ointment, 1% Voltaren gel, 1.3% diclofenac, or 4% ketamine compounded ointment. These patches and topical agents can also be used in conjunction with oral medications.

6 What is the risk of addiction with opioids?

Addiction (or psychologic dependence) needs to be differentiated from physical dependence. Physical dependence, a physiologic adaptation of the body to the presence of an opioid, develops in all patients maintained on opioids for a period of several weeks. If the opioid is stopped abruptly without tapering, the patient may show signs of withdrawal. The patient can stop opioids at any time and avoid withdrawal symptoms by tapering down. Tolerance is the need for a higher dose of opioid to produce the same pharmacologic effect. Neither physical dependence nor tolerance indicates addiction. The psychologic dependence seen with addiction is characterized by a compulsive behavior pattern involved in acquiring opioids for nonmedical purposes (psychic effects) as opposed to pain relief. The risk of iatrogenic addiction is very low; several studies have shown it to be less than 0.1%. Patients who are inadequately treated may seem to be drug seeking, because they repeatedly request opioids and are concerned with the timing of their next dose. Such pseudo addiction