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Patient-controlled analgesia
CMAJ 2001;164(5):620 [PDF]


See response from: C.H. McLeskey
Patient-controlled analgesia (PCA) is a computer-based medical technology now used extensively in Canada to treat postoperative pain. A typical PCA machine contains an embedded microcomputer programmed to give, for instance, 1 mg of morphine intravenously every time the patient pushes a button on the end of a cable. To prevent excessive drug administration, the onboard computer ignores further patient demands until a lockout period (usually set for 5–10 minutes) has passed.

Recently, the Institute for Safe Medication Practices reported that a patient had received a lethal morphine overdose while connected to the Abbott Lifecare 4100 PCA Plus II machine.1 This machine is easily misprogrammed by caregivers, who must manually enter the PCA parameters, and it needs a more sensible and forgiving user interface.2 A number of patients have received opiate overdoses as a result of PCA errors: insertion of a 5 mg/mL morphine cartridge when the machine is expecting a 1 mg/mL concentration, or acceptance of the default (initial) drug concentration when the correct action is to scroll up to the correct value, among other errors.3,4

In 1997, ECRI documented 3 deaths that occurred while patients were connected to the Lifecare 4100.5 In at least 2 of the cases, the alleged reasons for the deaths were the same. In the mode of operation in use, when nurses program the drug concentration the Lifecare 4100 display shows a particular concentration (e.g., 0.1 mg/mL). Nurses can either accept this initially displayed value or modify it using the arrow controls. The critical flaw in the design is that in this situation the Lifecare 4100 offers the minimal drug concentration as the initial choice. If nurses mistakenly accept the initially displayed minimal value (e.g., 0.1 mg/mL) instead of changing it to the correct (and higher) value (e.g., 2.0 mg/mL), the machine will "think" that the drug is less concentrated than it really is. As a result, it will pump more liquid, and thus more narcotic, into the patient than is desired.

The purpose of this letter is to warn clinicians of continuing fatal drug overdoses from the Abbott Lifecare 4100 PCA Plus II machine. If you use this machine, please contact your risk management officer and your biomedical engineering department for advice. Fortunately, Abbott is not the only supplier of PCA machines.

We have informed American and Canadian regulatory authorities; they are, of course, now studying the problem.

D. John Doyle
Department of Anesthesia
University of Toronto
Toronto, Ont.
Kim J. Vicente
Cognitive Engineering Laboratory
University of Toronto
Toronto, Ont.


References

    1.   Design flaw predisposes Abbott Lifecare PCA Plus II pump to dangerous medication errors. ISMP Medication Safety Alert 2000;5:2. Huntingdon Valley (PA): Institute for Safe Medication Practices; 2000.
    2.   Lin L, Isla R, Doniz K, Harkness H, Vicente KJ, Doyle DJ. Applying human factors to the design of medical equipment: patient-controlled analgesia. J Clin Monit Comput 1998;14:253-63. [MEDLINE]
    3.   Notcutt W. Overdose of opioid from patient controlled analgesia pumps. Br J Anaesth 1992;68:50.
    4.   Grover ER, Heath ML. Patient-controlled analgesia. A serious incident. Anaesthesia 1992;47:402-4. [MEDLINE]
    5.   ECRI. Abbott PCA Plus II patient-controlled analgesia pumps prone to misprogramming resulting in narcotic overinfusions. Health Devices 1997;26:389-91. [MEDLINE]

 

 

Copyright 2001 Canadian Medical Association or its licensors