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?

6 thoughts on “How often do errors with patient-controlled analgesia (PCA) occur?

  1. Bryanne Patel from the Veterans Administration Center for Patient Safety reported at the AAMI/FDA Infusion Safety Summit on PCA events investigated within the VA system. Of 12,000 root cause analyses conducted within the VA system over a 10 year period, 129 involved infusion pumps and 69 of the 129 involved PCA pumps. Based on these findings, the VA’s integrated product team recommended that PCA pumps with an integrated end tidal CO2 monitor is the pump of choice, because use of this technology could have prevented more than 60 percent of adverse events related to PCA pumps.


  2. Dr. Richard Dutton (Executive Director, Anesthesia Quality Institute) emailed the following comment (which is reprinted here with his permission):

    “PCA errors certainly occur, both in programming and in delivery, but any published estimate is likely to be only the tip of the iceberg. While category IV and V errors are probably collected most of the time, categories 1-III are only sporadically collected or reported.”

  3. Dr Stuart Forman (Associate Professor of Anesthesia, Dept. of Anesthesia Critical Care & Pain Medicine, Massachusetts General Hospital) emailed the following comment (which is reprinted with his permission):

    I don’t know of other studies, but my anecdotal experience suggests that you are probably looking at a significant safety issue. Many years ago, when I identified the potential harm and real near misses associated with human errors involving PCA, I was told that “smart pumps” and error-free syringe labeling and computerized prescription technology would make these issues obsolete. A decade has passed and while the orders are computerized, we still have multiple PCA mixes with variable potencies, and we still have manual programming of PCA pumps. I would bet that this situation produces frequent incidents of both under-treatment and over-treatment due to errors where the wrong drug cartridge is used or the pump is mis-programmed.

  4. Respiratory depression occurs more often than most clinicians think with PCA. Detection may vary depending the mode of monitoring. Respiratory depression was detected at a significantly higher rate in the capnography group. In total, 146 episodes of respiratory depression were detected during the 36 hours on the general care nursing unit: 140 in the capnography group and six in the control group. All of these episodes were detected because the patient either took six or fewer breaths per minute or had an episode of apnea lasting longer than 20 seconds. Seventeen patients (15 in the capnography group and two in the control group) accounted for all episodes of respiratory depression. Pauses in breathing while sleeping, an indicator of OSA risk, were detected in the capnography group at twice the rate as in the control group (48% and 24%, respectively).
    reference: Hutchison, R., Rodriguez, L. (2008) “Capnography and respiratory depression.” American Journal of Nursing. 108(2):35-39.

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