Incorrect Use of Smart Infusion Pump in the Operating Room (OR) Leads to Milrinone Overdose
Problem: An anesthesia resident wanted to start a milrinone infusion on a perioperative patient who required inotropic support. Milrinone is used in patients with acute decompensated heart failure with reduced ejection fraction, as well as before and after cardiac surgery. The typical dose range is between 0.1 to 0.75 mcg/kg/minute. The resident was unfamiliar with the smart infusion pump available for use in the operating room (OR). He subsequently entered an incorrect milrinone concentration of 200 mcg in 100 mL, when the infusion bag he was hanging contained 20 mg in 100 mL of 5% dextrose. He then programmed the infusion pump to deliver the intended dose-rate of 0.25 mcg/kg/minute.
The resident was using the pump in “anesthesia mode.” Milrinone was not listed in the anesthesia drug library because it was rarely used. Thus, he entered the drug concentration and dose manually. However, if the resident had used the “All Drugs” option available in “anesthesia mode,” he would have been able to access a milrinone infusion entry, which included preestablished low and high concentration limits. Prior to this incident, the resident was not aware of this function. Since the pump did not alert him to the erroneously low concentration entry, the resident initiated the infusion. As an aside, for this pump vendor, hard stops transitioned to soft stops in “anesthesia mode,” thereby allowing overrides of established dosing/concentration limits, even catastrophic limits.
Since the resident did not use milrinone frequently, he was unfamiliar with the Hospira packaging of the premixed infusion. During investigation of the event, the resident felt as though the label on the Hospira premixed bag of milrinone also contributed to the error. The per mL concentration, 200 mcg (0.2 mg)/mL, is the most prominent expression of the drug concentration, listed in large text right below the drug name at the center of a blue background on the label (Figure 1). The total amount per total volume (20 mg/100 mL), which should be the most prominent concentration expression following the drug name, is instead listed on the label in smaller print above the blue background. Thus, the resident mistakenly thought the bag contained a total of 200 mcg/100 mL.
Hypothetically, for an 80 kg patient, the infusion rate to deliver a dose of 0.25 mcg/kg/minute would be 6 mL per hour, using a 20 mg/100 mL milrinone infusion bag. If the pump was programmed with an erroneously low milrinone concentration of 200 mcg in 100 mL, the drug would infuse at a rate of 600 mL per hour. In this case, the 100 mL bag of milrinone completely infused in a very short time, leading the anesthesia resident to realize that an error had been made. Due to the milrinone overdose, the patient required observation and supportive care in an intensive care unit but did not suffer serious adverse effects (e.g., cardiac arrhythmia, significant hypotension).
Safe Practice Recommendations: Leadership must establish that the use of smart infusion pumps with an engaged drug library is an expected practice in the OR for all continuous medication infusions, intermittent and secondary infusions, loading and bolus doses, patient-controlled analgesia infusions, epidural and nerve block infusions, and infusions of hydrating solution (except when the hydrating fluid administration rate is greater than the pump allows). In the hospital where this error occurred, the anesthesia department chair has taken the important step of understanding why smart infusion pumps with an engaged drug library were not being correctly used in the OR by some anesthesia providers, including residents. An initiative was implemented to reduce these barriers, including:
Providing educational programs such as “anesthesia grand rounds,” which included discussions about this event and “hands on” education about smart infusion pump capabilities (e.g., dose/concentration limits and warnings, bolus dose feature)
Performing standardized competency assessments for the use of smart infusion pumps with an engaged drug library for all anesthesia residents, as well as anesthesia providers and other OR practitioners
Opening the lines of communication about future barriers to using smart infusion pumps so they can be addressed rather than result in unsafe practices (e.g., failing to engage the library)
Reissuing a leadership-driven requirement to use smart infusion pumps with an engaged drug library in the OR
When creating the anesthesia drug library, implement upper and lower hard limits whenever possible for medication doses, concentrations, infusion rates, and loading and bolus doses (often different than hard limits for maintenance infusions) used in the OR. The use of hard stops can serve as a forcing function and reduce the incidence of incorrect infusion pump programming. We also recommend limiting the use of “anesthesia mode” in smart pumps that change hard limits to soft limits, to ensure that catastrophic limits produce a hard stop. Use of smart pumps that default to, or require programming within the drug library, can also improve safety in the OR. For additional recommendations, please see the ISMP Guidelines for Optimizing Safe Implementation and Use of Smart Infusion Pumps.
ISMP has contacted Hospira about the milrinone labeling problem, and the company is currently revising the label to present the concentration as the total amount of drug in the container per the total volume, following USP <7> standards.