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Smart Pump Custom Concentrations without Hard “Low Concentration” Alerts Can Lead to Patient Harm

Problem: Earlier this month, ISMP held its second national summit on smart infusion pumps. The first summit, held in 2008, examined smart pump implementation, drug libraries, and clinical practice, and resulted in publication of the ISMP Guidelines for Safe Implementation and Use of Smart Infusion Pumps in 2009. Since then, smart pump technology has evolved, and its application has spread to nearly all US hospitals. During our latest summit, we focused on optimizing use of the technology during administration of secondary and intermittent infusions, patient-controlled analgesia (PCA), epidural infusions, plain IV solutions, and perioperative/anesthesia medications; preparing for pump-electronic health record (EHR) interoperability; and library analytics.

While preparing for the 2018 national summit, ISMP conducted several surveys to help inform the discussions. One of the surprising results was low compliance with setting hard stops (requires reprogramming) for minimum concentration limits when programming custom concentrations. Sometimes called “wild card” entries, programming a custom concentration entails selecting a drug from the library but then manually entering the concentration (e.g., xx mg/xx mL). According to a survey of more than 600 practitioners, only half of those who answered the question reported a hard stop for minimum concentration limits when programming custom concentrations. The survey also revealed that almost half of all respondents, including 29% who directly manage the drug library, were confused by the question or unsure whether their pumps had a hard stop for minimum concentration limits for custom concentrations.

The misuse of custom concentration options that do not employ a hard minimum concentration limit contributes largely to preventable errors given the counterintuitive, inverse relationship between the concentration and the volume. More concentrated drugs require less volume to deliver a specified dose; less concentrated drugs require more volume to deliver a specified dose. When using “fill-in-the-blank” custom concentrations, the concentration must be programmed into the pump so it can calculate the volume needed to deliver the prescribed dose. If the programmed concentration is lower than the actual concentration in the infusion bag or syringe, the pump will deliver an overdose. If the programmed concentration is higher than the actual concentration in the bag or syringe, the pump will deliver an underdose. Without a hard minimum concentration limit, the former scenario has led to life-threatening events, such as those described below.

A physician prescribed IV HYDROmorphone 20 mg/100 mL (0.2 mg/mL) to infuse at 2.5 mg/hour. The standard concentration for this infusion was 0.1 mg/mL, so the custom concentration of 0.2 mg/mL had to be manually entered into the smart pump. The nurse selected the custom concentration option and then mistakenly entered 2.5 mg/100 mL as the concentration instead of 20 mg/100 mL. Given the erroneously programmed concentration of 0.025 mg/mL, the pump issued a soft (i.e., can be overridden) low concentration alert. The nurse overrode the warning, mistakenly believing the “low concentration” warning was inconsequential. The pump infused the drug at a rate of 100 mL/hour, while the intended rate was 12.5 mL/hour. The pump delivered the entire bag of HYDROmorphone 20 mg to the patient in 1 hour. The clinical outcome of the patient was not reported.

An infusion of IV furosemide 10 mg/hour was prescribed. When programming the smart pump, a nurse selected the custom concentration option and then accidentally entered the concentration as 10 mg/100 mL (0.1 mg/mL) instead of the intended 100 mg/100 mL (1 mg/mL). The pump had a soft low concentration limit set at 0.2 mg/mL, so a soft alert was issued. The nurse bypassed the alert, and the entire bag containing 100 mg of furosemide infused in 1 hour instead of 10 hours. Fortunately, the patient was not harmed.

Milrinone IV was prescribed to infuse at 2.5 mg/hour. The pharmacy dispensed a 20 mg/ 100 mL (0.2 mg/mL) milrinone infusion bag. Using the custom concentration option, a nurse set the concentration as 0.2 mg/100 mL. The entire bag containing 20 mg infused in a matter of minutes instead of infusing over 8 hours. The patient required a bolus of IV fluids to treat hypotension, but no changes in the patient’s heart rhythm were reported.

Other serious smart pump-related errors have occurred when practitioners have unnecessarily selected a custom concentration option, and then entered the wrong concentration, even though a standard concentration option for the drug was available in the pump library. In these cases, programming errors would have resulted in a hard stop had the standard concentration pathways been employed. Examples of this type of error follow.

A physician prescribed IV heparin to infuse at 800 units/hour. The pharmacy dispensed 25,000 units of heparin in a 250 mL bag. Although this standard concentration was in the pump library, the nurse selected the custom concentration option and erroneously entered the heparin concentration as 800 units/250 mL. Given the erroneously programmed concentration of 3.2 units/mL, the pump infused the drug at 250 mL/hour, not the intended rate of 8 mL/hour. The pump delivered 25,000 units of heparin to the patient in 1 hour. The patient required IV protamine but did not experience significant bleeding.

A physician prescribed IV insulin (regular) 12.5 units/hour for a patient with hyperglycemia. A standard insulin infusion of 100 units/100 mL (1 unit/mL) was dispensed from the pharmacy. When programming the pump, the nurse failed to select the standard insulin concentration and instead used the custom concentration option to enter an erroneous concentration of 5 units/100 mL (0.05 units/mL). The pump infused the drug at a rate of 250 mL/hour. The entire bag containing 100 units of insulin infused in approximately 20 minutes. The patient’s outcome was not reported.

A physician prescribed morphine PCA for an opioid-tolerant patient with a demand dose of 1.5 mg, a lockout of 10 minutes, and a basal rate of 1.5 mg/hour. The pharmacy dispensed a 60 mL syringe of morphine 55 mg/55 mL. Instead of using the standard concentration (1 mg/mL) option in the library, the nurse entered a custom concentration of 1.5 mg/55 mL, which resulted in a concentration of 0.027 mg/mL. Given the basal rate of 1.5 mg/hour, the patient received the entire 55 mg of morphine within an hour and was transferred to an intensive care unit for treatment. No outcome was reported.

Some of the above-cited errors appear to be mental mix-ups in which the “dose per hour” was paired with the total infusion volume—for example, a heparin dose of 800 units/hour from a 25,000 units/250 mL bag ended up as a concentration of 800 units/250 mL. One of the errors appears to be a mix-up in which the “per mL” concentration was paired with the total infusion volume—for example, a 0.2 mg/mL concentration of milrinone in a 20 mg/ 100 mL bag ended up as a 0.2 mg/100 mL concentration. Sometimes, the way the concentration is expressed on labels, particularly if the label includes technician instructions for admixture, has also contributed to mistaken concentrations. Custom concentration options that inadvertently remain in the drug library after a limited number of standard concentrations have been added to the library is another factor associated with errors. Custom concentrations may be required for some medications that are dosed according to body weight or surface area. But leaving the option open to enter the concentration of infusions that have since been standardized needlessly increases the risk of patient harm.

Another factor in some of the above-cited errors is misunderstanding the significance of a soft low concentration alert. Since the primary emphasis on averting IV errors is often on doses that exceed maximum limits, “low concentration” soft alerts may be misinterpreted as being similar to “low dose” alerts. Pharmacists responsible for building and maintaining pump libraries also may not fully appreciate the importance of building hard stops for low concentration alerts, particularly for high-alert medications.

Safe Practice Recommendations: There are several lessons to be learned from these events to maximize safety when using custom concentrations with smart infusion pumps. 

Standardize concentrations. When possible, use a single, standard concentration for each drug infusion. If more than one concentration is necessary, limit the number of concentrations to two, and avoid concentrations that differ by a factor of 10 (e.g., 0.1 mg/mL and 1 mg/mL, 1 mg/mL and 10 mg/mL), which could be confused by a misplaced decimal. Be sure the pump library reflects the standard concentration(s) used for each drug. Use of custom concentrations should be curtailed and, when possible, restricted to selected patient care areas. Remove custom concentration options from the pump library when a standard concentration for that drug has been established and built into the library.

Set hard minimum concentration limits. For each drug, especially a high-alert medication, that allows a custom concentration option in the library, set a hard minimum concentration limit that requires reprogramming to avoid a catastrophic overdose.

Educate staff. Educate staff regarding the inverse relationship between the concentration and the volume, and the significance of low concentration alerts.

Distinguish custom concentrations. Should a custom concentration be unavoidable, make the container label distinctive compared to labels on containers containing a standard concentration. Affix auxiliary labels as appropriate.

Require doses to be expressed in the metric unit. Ensure that doses in protocols and order sets for infusions include the metric unit of dosing (mg/hour, mcg/kg/hour, etc.). An order for an infusion with just the infusion rate (e.g., mL/hour) should not be accepted, even if only one standard concentration of the medication is being used hospital-wide. Standardized order sets and electronic prescribing systems should allow the prescriber to select only the standard concentration(s) when applicable. Also, orders for infusions should not be prescriptive regarding the concentration—only the patient’s dose (mg/hour, mcg/kg/min, etc.) should be specified to avoid the risk of variable concentrations being ordered. If fluid restrictions are necessary for a patient, a “double” or “triple” concentration can be prescribed without specifying the amount of drug per mL.

Tailor labels to MAR/pump settings. The medication administration record (MAR) and the infusion label should present the drug and concentration (and infusion rate, if provided) in the same units and sequence required when programming the pump, with specific instructions for custom concentrations as necessary. Technician preparation instructions (e.g., calculations) should not be included on the final product label.

Verify pump programming. At hospital-defined steps (e.g., new bag/bottle/syringe, change in the rate of infusion) for selected high-alert medications, require an independent double check using the EHR/MAR/eMAR and available technology (e.g., smart pumps, barcode scanning technology) to verify and document the following before starting the infusion: drug/solution, drug concentration, rate of infusion, patient, channel selection, and line attachment. (With interoperability, the latter two elements still require practitioner verification if technology is employed to verify/autopopulate the other elements.) Exception: Titrated medications (e.g., vasopressors) to effect. Be sure the final infusion rate falls within an expected range. Entering an erroneous, low concentration will often result in a high, atypical infusion rate, which should serve as a signal to reverify the pump settings.

Analyze data. Routinely evaluate the metrics that are available with smart pumps to identify the use of custom concentrations, hard stops for minimum concentrations, soft alert overrides, actions taken in response to these alerts, and other vulnerabilities that may lead to errors. Take action to reduce identified risks. If nurses are using the custom concentration option to program standard concentration infusions that are available in the library, investigate the underlying reasons that may be driving this practice.

Look for our updated smart pump guidelines later this year! We will let readers know when the draft guidelines are available on our website for public comment. 

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