In the hospital setting, various regulatory agencies require the pharmacy to follow specific storage indications for temperature sensitive medications as determined by the medication manufacturers. These indications, which include the ability to consistently monitor and document the temperatures within refrigerated storage areas, are designed to protect the integrity of these medications to ensure patient safety, but a failure to follow such indications also can result in costly losses of medication inventory.

In order to facilitate regulatory requirements and avoid unnecessary wasting of medications, the MD Anderson Division of Pharmacy implemented a radio frequency identification (RFID) system to enable wireless temperature monitoring and reporting functionalities to be deployed in areas with wireless access, thereby ensuring the safety and integrity of temperature-sensitive medications. 



Wi-Fi based RFID temperature tags use standard Wi-Fi networks to monitor temperatures in real time, in addition to other location and status information. Through the RFID application software, automatic alerts can be set to trigger if environmental conditions exceed specific, pre-defined thresholds. In this context, the ability of RFID to enable real-time monitoring of temperature status was particularly appealing to us because in the event of a refrigeration unit failure, we wanted to have accurate temperature information delivered to us as quickly as possible. However, in addition to this, we were also curious as to whether our temperature readings were consistent within each individual refrigerator.

In general, the use of temperature monitoring probes—whether they be RFID-based, wired, or wireless—is becoming more ubiquitous in hospital pharmacies, but the types of probes, their shapes and combinations (eg, a metal probe inside a vial of glycol versus a vial of glass beads), as well as the methods by which those probes gather information, differ. With this in mind, we wondered if temperature readings would fluctuate based on the physical placement of probes within refrigerators. With a goal of maximizing the effectiveness of our temperature monitoring method, we endeavored to identify the ideal locations within our pharmacy refrigerators to place the RFID temperature monitoring tags in order to better understand the temperature variations that exist inside medical grade refrigerators.

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Ideal Placement for Temperature Tags and Probes
Although some refrigeration units are designed with a small footprint and offer minimal interior space, other units can be quite large with significant square footage of storage space. So, when developing our implementation plans for RFID temperature monitoring, we were surprised to discover a lack of definitive guidance on determining the best and most appropriate placement of temperature tags—as well as the eventual medication stock—within a refrigerator. Therefore, we decided to test the temperature variation inside pharmacy refrigerators in order to determine ideal tag placements. To study this, we tested four refrigerators used in our pharmacy—three large, medical-grade refrigerators and one small, commercial dorm-style refrigerator; two of the large medical grade refrigerators were the same brand. We then randomly selected nine RFID temperature monitoring tags certified by the National Institute of Standards and Technology (NIST), all of which were configured to record real-time, ambient temperature data. The same nine tags were placed inside each pharmacy refrigerator for each test—one placed in each of the eight interior corners (top and bottom of the unit) and one in the center—and tag temperature data was collected for multiple days. Descriptive statistics were collected for each tag and each refrigerator—including refrigerator mean temperature, standard deviation, and median, minimum, and maximum temperatures—and an analysis of variance was used to evaluate the effect of a refrigerator’s height, width, and depth on its inside temperature. 

Impact of Temperature Variation on Practice
The results of our study demonstrated that temperature variations existed between tag locations inside the medication refrigerators. On average, we discovered a 4-6°C difference from the coldest location to the warmest location in each refrigerator for the tested periods. The coldest location inside a refrigerator differed from refrigerator to refrigerator, even for units of the same brand; however, generally, the coldest location inside a refrigerator was determined to be near the fan. Ultimately, it was clear that the internal location of a refrigerator’s temperature monitoring probe or tag affects its temperature reading.

The results of this study have served to raise significant awareness of the issue of temperature variation within refrigeration units and have spurred further discussion over how best to maintain refrigerated products throughout the facility. In order to gain the most reliable temperature readings, we now place our probes in the center of cold temperature storage units. Although specific recommendations are still pending, our pharmacies do now avoid placing fluid medications near the refrigerator fan. Given that temperature fluctuations differed among units both of the same brand and of different brands, it is recommended that hospitals assess the conditions within their refrigerators and freezers in individual units and across facilities.

Conclusion
The USP and the Texas State Board of Pharmacy define a proper refrigeration temperature range of 2-8°C in order to protect the stability and viability of medications requiring refrigeration. After discovering a wide range of temperature ranges among the different types of refrigerators in use in our pharmacy, we recommend running an assessment plan in your own pharmacy to better understand and optimize the utilization of medication refrigerators. This includes, but is not limited to identifying and marking appropriate placement locations in individual refrigerators for medications more susceptible to temperature variations outside of the recommended range. 

As with all automation and technology designed to protect product integrity and ensure safety, the mechanisms by which that protection is provided must be understood and monitored as well. We cannot simply assume that protection is provided in a universal way. Although modern medical-grade refrigeration is robust and effective, it too has subtle nuances that require a close eye in order to protect overarching medication safety plans.

This project was the result of collaboration between the department of pharmacy informatics, the department of pharmacy academic affairs, and the office of performance improvement at the University of Texas MD Anderson Cancer Center. The following staff contributed to this article: Chun Feng, MA, ASQ BB, senior informatics analyst; Howard Ritter, RPh, quality assurance specialist; Kristy S. Fitzgerald, PharmD, MBA, RPh, senior pharmacy clinical informatics specialist; James A. Terrell, MS, ASQ BB, CQE, CRE, principal—applied statistics (recognized posthumously); Trong C. Truong, BS, systems analyst II; and Jon W. Vanderhoofven, RPh, MBA, director—pharmacy informatics.