With the more typical intravenous PCA, the computerized pump allows for a number of variables, including:
- An initial bolus or loading dose to bring the pain under immediate control—an important but sometimes overlooked consideration in the successful use of PCAs;
- The patient-initiated or demand dose, available to the patient at the press of a button;
- The delay interval or lockout, typically between six and 15 minutes, allowing the analgesic to achieve its peak effect before another dose can be administered. The number of unsuccessful demands by patients during lockout periods is important for the physician to know;
- A continuous infusion or basal rate to provide continuous pain relief, although this may be contraindicated for opioid-naïve patients starting on PCAs.4 For those receiving opioids for chronic pain, the basal rate could be their current analgesic dose converted to the intravenous equivalent. Alternatively, the patient could receive this dose in a long-acting oral analgesic, with the PCA used for incidental or breakthrough pain. A basal rate also helps patients sleep, their pain controlled without having to wake up to press for a dose;
- A maximum volume of drug to be administered within a defined period of one, four, eight, or 24 hours, calculated to prevent an opioid overdose—regardless of how many times the PCA button gets pushed; and
- Monitoring devices such as pulse oximeter or end-tidal carbon dioxide monitor may be part of the PCA system to help warn of emerging respiratory depression.
The fundamental challenge for physicians lies in balancing the loading, basal, and patient-initiated doses with an appropriate maximum to make sure the patient gets adequate pain relief but doesn’t overdose. This is a more complex, multifaceted mathematical formula than ordering opioids to be administered two, three, or four times a day.
A basic safeguard of the PCA for preventing overdose is that when the opioid analgesic starts to make the patient drowsy, he or she is likely to stop pressing the button for another dose. However, for this to work, the PCA must be patient-controlled. If a nurse or family member pushes the button on the patient’s behalf out of a well-meaning desire to keep pain in check, this raises the risk of overdose.
In the past few years, several national quality and safety organizations have issued alerts about the danger of such patient-controlled analgesia by proxy. The Institute for Safe Medication Practices (ISMP) in Huntington Valley, Pa., issued two safety alerts in July 2003 discussing how potentially life-threatening errors can occur with PCAs and offering ways to prevent such errors.
U.S. Pharmacopeia’s summer 2004 USP Quality Review also offered safety recommendations based on analysis of medical errors directly resulting from PCA by proxy. The Joint Commission issued a Sentinel Alert on Dec. 20, 2004, noting that “serious adverse effects can occur when family members, caregivers or clinicians who are not authorized become involved in administering the analgesic for the patient by proxy.”5 Earlier this year the American Society for Pain Management Nursing issued clinical practice recommendations for how nurses can deal with the problem of PCA by proxy.6
Well-designed hospital PCA protocols will address this problem by including clear instructions to family members not to push the button for the patient, with an explanation of why this can be dangerous. Printed brochures and signs in the patient’s room are also helpful.
The Need for Training
“Physicians, as a rule, don’t receive adequate training in the PCA,” says Jean Youngwerth, MD, hospitalist, palliative care consultant and fellowship associate director at the University of Colorado Health Sciences Center in Denver. “Then you’re expected to know how to use it. There clearly is a need for this kind of training in the basics of the PCA, but a brief in-service should be sufficient.”