How often do errors with patient-controlled analgesia (PCA) occur?

by Michael Wong

Many readers of this website have asked, how often do errors with patient-controlled analgesia (PCA) occur?

In a retrospective analysis lead by Rodney Hicks (who at the time of the study was Manager, Patient Safety Research and Practice, United States Pharmacopeia), the magnitude, frequency, and nature of non-harmful and harmful medication errors associated with PCA were studied. (Professor Hicks is now Professor, Western University College of Graduate Nursing, Pomona, California).

Over the five-year review period, of the 919,241 medication errors records from the 801 reporting healthcare facilities, just 1% (or 9,571) were associated with PCA. Although 1% may seem insignificant, this analysis was based on the voluntary medication error reporting program, MedMarx.

“Although generalization of voluntary reported findings to the general population should be done cautiously,” as Professor Hicks points out, “The general rule of thumb is that for every reported event, there can be between 300-1,000 unreported events.”

Using this rule of thumb, based on 9,571 reported events, this would mean that between 2.8 million and 9.6 million total events (unreported & reported) occurred over the five-year period from July 1, 2000 to June 30, 2005. On an annualized basis, this would mean that about 600,000 to 2 million events per year could involve PCA.

“A further study would need to be done to ascertain the total number of PCA events,” explains Professor Hicks, “but the problem is extensive in my opinion.”

Moreover, when the study looked at the number of events that caused harm, there were 624 records of PCA associated with harm, corresponding to 6.5% of the patients. Again, while 6.5% may seem small, as the study found, “By comparison, during the same period, only 1.5% of all other errors reported to MedMarx led to harm. This represents a fourfold higher relative risk of harm for PCA events.”

“All health care disciplines were implicated in the errors, including physicians, pharmacists, and nurses” Hicks reported.  “Therefore, it will take an inter-disciplinary team to resolve the problems”.

As Professor Hicks concludes:

Our analysis was in no means trying to discourage the use of PCA pumps. Many studies have shown the benefits of using PCA, including improved pain management, better utilization of nursing resources, increased patient satisfaction, and improved pulmonary function.

However, this is clearly an area that standardization needs to occur and organizations need to invest in training and policies and procedures as well as equipment – all areas to promote safety.

Moreover, although elimination of error is critical, studies have shown even a correctly programmed PCA pump poses patient safety risks. In their study, “Continuous Oximetry/Capnometry Monitoring Reveals Frequent Desaturation and Bradypnea During Patient-Controlled Analgesia”, Dr. Frank Overdyke and his colleagues point out, “The most serious complication of patient-controlled analgesia (PCA) is respiratory depression (RD).” They found that:

continuous respiratory monitoring is optimal for the safe administration of PCA, because any RD event can progress to respiratory arrest if undetected.

As Ray Maddox and his colleagues point out in their study “Intravenous Infusion Safety Initiative: Collaboration, Evidence-Based Best Practices, and ‘Smart’ Technology Help Avert High-Risk Adverse Drug Events and Improve Patient Outcomes”:

Even correctly programmed, appropriate doses of opiates can suppress respiration and decrease heart rate and blood pressure. Episodes of bradypnea and desaturation can escalate to respiratory depression (RD) requiring rescue. The success rate for in-hospital cardiopulmonary resuscitation remains less than one in five patients. If detected early, most cases of opioid-induced respiratory depression can be treated with naloxone. However, severe cases can be fatal. The risk of patient harm due to medication errors with PCA pumps is 3.5-times the risk from any other type of medication administration error.

These researchers therefore recommend:

Capnographic monitoring—measurements of ventilation using respiration and exhaled carbon dioxide (EtCO2)—is particularly important because it can provide an earlier warning of respiratory depression than pulse oximetry (SpO2) in some patient populations.

What do you think? Are you aware of any other studies that have looked at PCA error incidence rates?