To the Editor:
The administration of opioids via patient-controlled analgesia (PCA) pumps is common. In the Pharmacia Deltec model #5800, the pumping mechanism involves two valves in sequence which infuse medication by peristalsis. The opioid cassette is attached via a hinge system and aligns the tubing to the valve-expulsor system. If the hinges of the cassette become disengaged, the tubing is not compressed and the medication flow is regulated by gravitational forces.
Uncoupling of the cassette from the PCA pump is a rare but potentially fatal complication. We report a case of a patient receiving an accidental overdose when the rigid cassette containing the opioid was disengaged from the pump. The pump was suspended from an intravenous pole, and 26 mL of morphine (5 mg/mL) freely flowed into the patient. The patient was successfully and uneventfully resuscitated with the help of intravenous naloxone, and both the Food and Drug Administration and Pharmacia Deltec were duly notified.
To avoid this complication, the integrity of the pump's locking mechanism should be verified as recommended in the Pharmacia Deltec operating manual. In addition to this precaution, we now incorporate a one-way pressure-driven valve (Braun normally closed backcheck valve BC-1000) in the tubing which obstructs the gravitational flow of medication but does not impede the pumpdriven flow of medication.
Teresa M. Ulrey, MD
Mary Whitley, MD
Department of Anesthesia, Georgetown University Medical Center, Washington, DC 20007-2197