Abstract
The use of opioids to treat chronic noncancer pain has increased significantly over the last 15 years, in spite of very limited evidence to document its safety or efficacy. As the use of prescription opioids has increased, so has the misuse and abuse of prescription opioids. In the preoperative period, health care providers are faced with the challenge of managing patients on escalating doses of opioids. Pain control in the patient on chronic opioid therapy should rely on multimodal analgesia rather than just opioid dose escalation. Moreover, these patients frequently suffer from extensive comorbidities, including obstructive sleep apnea and polypharmacy, that can be fatal if not screened for properly.
Keywords
opioids, chronic, pain, morphine equivalents, multimodal, abuse
Case Synopsis
A 38-year-old woman is transported to the emergency department (ED) via ambulance following a motor vehicle crash. Her medical history is notable for hypothyroidism, as well as a history of an intravenous (IV) opioid use disorder diagnosed at the age of 25. Her opioid use disorder is managed with medication-assisted treatment (MAT), which was started 10 years ago. She is currently receiving buprenorphine/naloxone 8 mg/2 mg twice daily. Following her evaluation in the ED, she is diagnosed with a femur fracture and scheduled for urgent surgical correction.
Problem Analysis
Definition
The use of opioids to treat chronic noncancer pain has increased significantly over the last 15 years, despite very limited evidence to document its safety or efficacy. As the use of prescription opioids has increased, so has the misuse and abuse of prescription opioids. Addiction to prescription drugs, most often opioids, has skyrocketed, and more people than ever are dying from the adverse effects of opioids. Misuse and abuse of prescription drugs is commonly associated with the dramatic rise of heroin abuse and the subsequent rise in heroin overdose deaths.
Tolerance develops following chronic use of many drugs, including opioids. Tolerance can be defined as a change in a patient’s response to a medication over time such that an increased dose is needed to achieve the same effect. Opioids are associated with differential tolerance, in that tolerance to the various effects of opioids (i.e., analgesia, ventilation, sedation, constipation) appears to develop at different rates and to different degrees. Tolerance to the analgesic effects can occur quickly, whereas tolerance to the effects of opioids on ventilation occurs more slowly and to a lesser degree than observed with analgesia. As a result, aggressive up-titration of opioids to achieve analgesia in an opioid-tolerant patient appears to have an increased risk of respiratory-related complications compared with patients who have not been exposed to opioids. The Food and Drug Administration defines opioid tolerance as being present when a patient has received at least 60 mg a day of morphine or morphine equivalents for at least 1 week.
Addiction is a term that remains in common use, although the term has been replaced as a diagnosis in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) with the term substance use disorder. The American Society of Addiction Medicine defines addiction as
a primary, chronic, neurobiologic disease, with genetic, psychosocial, and environmental factors influencing its development and manifestations. It is characterized by behaviors that include the following: Impaired control over drug use, craving, compulsive use and continued use despite harm. [emphasis added]
The diagnostic criteria for opioid use disorder were revised in the DSM-5 (see Box 4.1 in Chapter 4 ). The new diagnosis attempts to capture the essence of addiction while avoiding categorizing patients properly using chronic opioids under physician supervision as having an addiction disorder.
When discussing chronic opioid therapy, an important concept to understand is how to properly quantify daily opioid dose. A common method for doing this is through the use of “morphine equivalent dose” (MED). The total daily opioid dose is determined, then the dose is expressed in MED using an opioid conversion table. The patient’s MED may be used to guide proper opioid prescribing and may be predictive of the patient’s postoperative pain experience.
Recognition
A careful history and physical examination is essential to guide clinical decision making. It is important to carefully determine what medications the patient is taking. Likewise, it is critical for the physician to carefully determine the current opioid dose and if the opioid dose has recently been started or is chronic.
Patients with chronic pain conditions and patients with substance use disorders both have an increased risk of mental health disorders, including depression and anxiety disorders. In addition, patients with substance use disorders are more likely than the general population to have a history of posttraumatic stress disorder, as well as an Axis II disorder. The presence of these conditions may affect perioperative care, as will the use of medications to treat these conditions.
Risk Assessment
Patients taking chronic opioids at the time of surgery are more likely to experience poorly controlled pain following surgery. The presence of differential tolerance following chronic opioid use, combined with complaints of poor pain control, likely increases the risk of respiratory-related complications including respiratory arrest and death following aggressive use of systemic opioids to treat pain. Risk of harm is increased significantly if benzodiazepines are administered in combination with opioids.
Patients with sleep-disordered breathing, including obstructive sleep apnea (OSA) or central sleep apnea, are at increased risk of compromised ventilation following the administration of systemic opioids. There may be an increased risk for central sleep apnea in patients receiving greater than 100 mg/day MED of chronic opioids. OSA is often present but not diagnosed or properly treated. Therefore many providers are advocating for perioperative screening for OSA and increased monitoring and intervention to ensure proper oxygenation and ventilation in patients identified to be at high risk for OSA. Likewise, early identification of patients on high doses (greater than 80–100 MED) of opioids may allow for institution of monitoring and early intervention when indicated.
Implications
There is growing evidence in the literature that outcomes following elective surgery may be compromised in patients on high doses of chronic opioids. For example, patients taking more than 80 mg MED of chronic opioids often report poor acute and chronic pain control and no or limited improvement in physical functioning following joint replacement surgery. Therefore early identification of patients on chronic opioids and consideration of efforts to decrease the prescribed dose of opioids preoperatively may lead to improved outcomes following surgery.
Patients receiving chronic opioids are at high risk for the development of opioid withdrawal symptoms if opioids are abruptly discontinued. The time to onset of withdrawal symptoms varies with the pharmacokinetics of the consumed opioid ( Table 5.1 ). Although not usually life threatening, opioid withdrawal symptoms can be very distressing, and when unrecognized can lead to extensive unnecessary medical evaluation when the symptoms present following surgery. Patients on chronic opioids will, of course, experience severe pain following surgery if their chronic opioids are not continued following surgery. Therefore it is important to identify patients on chronic opioids before surgery and put into place a proactive plan to avoid opioid withdrawal and treat anticipated pain as best as one can.
| Opioid | Onset | Peak Intensity | Duration |
|---|---|---|---|
| Meperidine Fentanyl | 2–6 hours | 6–12 hours | 4–5 days |
| Morphine Heroin | 6–12 hours | 36–72 hours | 7–10 days |
| Methadone | 24–48 hours | 3–21 days | 6–7 weeks |
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