How Is Patient-Controlled Analgesia Best Used to Control Pain?

Introduction and Scope of the Problem

Pain is defined as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage.” The experience of pain is subjective, and thus a patient’s self-report of pain is the gold standard for assessment. Pain is a common symptom experienced by patients with serious illness, including 30% to 60% of patients with cancer, 55% of patients with heart failure, and 32% of patients with other serious illnesses, including end stage kidney disease and chronic obstructive pulmonary disease.

Despite the prevalence of pain as a symptom in patients with serious illness, undertreatment is a common problem. Poorly treated pain can result in adverse patient outcomes, including decreased patient satisfaction, depressed mood, decreased quality of life, worsening of functional status, and increased costs resulting from prolonged hospital stays and delayed return to work.

Patient-controlled analgesia (PCA) refers to administration of pain medication immediately upon patient request. While this can include modalities such as epidural, inhalation, oral, and nasal administration, it usually refers to the use of an infusion system that allows a patient to self-administer an intravenous or subcutaneous opioid at a dose and frequency determined by a clinician, sometimes described as IV-PCA. For the purpose of this chapter, PCA will refer to IV-PCA . With built-in safety mechanisms that minimize risk of overdose and toxicity, PCA is a convenient way to deliver opioids to those with moderate to severe pain and is well received by patients. Oral pain medications are recommended for mild to moderate pain, but for severe pain or patients who have difficulty taking medications by mouth, intravenous opioids provide faster time to drug onset. First described by Sechzer in 1968 and introduced into clinical practice in 1976, PCA pumps are now electronic and allow clinicians to collect information about a patient’s analgesic use and pain patterns. PCA allows patients to take control of analgesic dosing, eliminating delays related to clinician-administered intravenous opioids. PCA can be used to manage acute pain—for example, in the postoperative period—or persistent moderate to severe pain in the setting of serious illness such as cancer. It is also appropriate for use in the hospital, home, or health care facility setting, including for those patients in hospice.

Relevant Pathophysiology

Opioid Characteristics Important for PCA Dosing

Intravenous opioids reach peak plasma concentration approximately 6 to 15 minutes after administration, versus 60 to 90 minutes for oral opioids. After a dose of intravenous opioid is administered, waiting until peak analgesic effect has been reached allows for assessment of whether additional medication is needed, as well as assessment of whether sedation or respiratory depression is present. Intravenous opioids other than methadone are inherently short acting, in comparison to long-acting oral opioids which are formulated to last between 8 and 24 hours. Unlike other categories of analgesic medications, opioids do not have an analgesic efficacy ceiling, meaning that higher doses are typically associated with increased pain relief, and doses are mainly limited by development of side effects. Because a patient has to be alert to press the PCA button for a demand dose, sedation generally prevents a patient from administering excessive medication. Therefore adjustment of the PCA settings based on an individual’s usage will allow for superior pain control.

Summary of Evidence Regarding Treatment Recommendations

What Patient Factors Should Be Considered When Prescribing PCA?

The PCA delivery system includes an infusion bag secured in a programmable electronic pump for direct delivery to the patient. Typically, PCA is provided via an intravenous route, but a subcutaneous route can also be used (discussed shortly). It is important to consider patient factors to determine whether PCA is an appropriate tool to treat pain. These factors include cognitive ability, physical ability to use the pump, and comorbidities. Patients treated with PCA typically have moderate or severe pain expected to last more than 24 hours and are often located in the hospital setting. PCA can be used at home or in a facility setting when supervised by a qualified provider. A patient must have the cognitive ability to identify that they have pain and understand how to self-administer the medication when they feel the need to do so. In addition, they must understand that they are the only person who is permitted to press the button to obtain medication. Young or advanced age is not necessarily a contraindication. Children as young as 4 years of age have used PCA safely and effectively. Patients in their late 90s have also demonstrated effective PCA use. In general, a patient who can understand and consistently follow the instructions to press the button for a demand dose when they are experiencing pain can be considered appropriate for PCA.

Because successful PCA use requires intact cognitive function, patients with dementia and/or delirium are unlikely to be able to safely use a PCA device. Another contraindication for PCA use is a short expected pain duration—for instance, if a patient is expected to need an opioid for less than 24 hours. Caution should also be exercised for patients who have comorbidities that may increase the risk of respiratory depression, including sleep apnea, chronic obstructive pulmonary disease, or obesity hypoventilation syndrome. In the setting of severe underlying renal or hepatic impairment, opioid clearance may be decreased, increasing the risk of side effects and adverse events, including respiratory depression. To successfully use PCA, a patient must also have the strength in their hand to activate a demand dose. Patients with a wide variety of medical conditions may be unable to do so.

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here