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Maintaining the Cold Chain for Medical Products

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Medical tissue samples, critical vaccines, pharmaceutical products and other frozen or refrigerated inventory can be ruined if the exact temperature is not maintained while in storage. Or they can fall out of compliance if their temperature is regulated. In addition, several regulating bodies provide temperature standards, including the Centers for Disease Control (CDC), Vaccines for Children (VFC) Program, and state and local health departments. Storing cold pharmaceutical products presents additional challenges.

Monitoring pharmaceuticals

Manufactured drugs have evolved, and they now contain more high-value ingredients. This means they often have a shorter shelf life and stricter temperature requirements for storage. In addition, a new class of drugs called biologics is growing, and they require temperature-controlled distribution. Ensuring product quality requires strict temperature monitoring, and the most common acceptable temperature range for pharmaceutical products is 2 °C – 8 °C. All people dealing with cold medical products, including pharmaceuticals, must understand the cold chain.

What is the cold chain?

A cold chain is a temperature-controlled supply chain. All links in the chain must remain unbroken to maintain product integrity. (See the illustration below of a cold chain flow chart for vaccines.)  In order for the cold chain to remain unbroken, the temperature must remain steady (refrigerated or frozen) from production through transportation and storage until distributed or given as treatment to a patient.

Cold Chain Flowchart

What happens if the chain breaks?

If the temperature goes out of range, the product quality and effectiveness or safety can suffer. For example, with vaccines, failure to maintain the correct temperature often reduces their potency, which can’t be restored. Vaccines can be ruined from excessive heat, cold or light, and you usually can’t tell a ruined vaccine from a good one. This means that the only real way to safeguard them is to be proactive about maintaining the correct temperature. And if you are a VFC provider, you must follow VFC guidelines and be able to demonstrate that the vaccines you are storing never fell out of the recommended temperature range.

Other medical assets like drugs, blood and tissue samples can be just as temperature-critical as vaccines. These assets typically spend most of their time in storage waiting to be used, so the storage link is critical in the chain. 

How can you ensure a constant temperature?

The CDC provides specific guidelines for vaccines (shown below), but we have similar recommendations for all medical products which center on using remote monitoring technology. We suggest you monitor both the alarm panel on the refrigerator and the actual temperature inside the refrigerator using a temperature sensor/probe. They are wired or wirelessly connected to a more intelligent device that continually displays and records the temperature readings. That device is typically called a “data recorder,” “data logger” or “remote monitoring system.” Think of a home alarm system. The sensors are the devices that measure whether a window or door opens, and the wall unit records the information and triggers alarms when needed.

We also recommend using a temperature buffer. The buffer acts as a cushion against temperature fluctuations in a freezer or refrigerator. A typical buffer is a bottle filled with a glycol solution or glass beads in which a probe or sensor is inserted. Without a buffer, the probe or sensor is measuring the atmosphere inside the storage unit, which can change rapidly with defrost cycles, the opening of doors, and fans circulating the air. The air temperature of the storage unit changes much more quickly than the temperature of vaccines and pharmaceutical products, so a buffered probe reading more accurately represents the temperature of medical assets.

CDC Thermometer Recommendations

Continuous recording of storage temperatures

Traditionally, facilities used a manual method to keep an ongoing record of temperatures. They would post log sheets on each refrigerator and freezer, and a designated staff member would record the temperature at a set time each day and record the temperature in the log. These days, data loggers are available that continuously read the temperature from the probes in the refrigerators and store the readings. Users can view the data from a computer or tablet at any time. Besides providing documentation, the data logger can alarm when temperatures go out of range.

A remote monitoring system includes a data logger, but takes things a step further by automatically storing the data in a remote location that can be accessed by any desktop, tablet or phone. This means that personnel no longer need to be physically at the location of the refrigerators and freezers.

You can log data at user-customizable intervals, and you can log separate intervals when in an alarm state. The data is downloaded remotely through a website, either via a local network or cloud, where it can be printed or exported as a .pdf, Excel spreadsheet or .csv.

Remote monitoring systems also provide alarming functionality. When a temperature is logged that falls outside a preset range, the system sends a phone call, text or email to the designated contacts, so that they can take preventive action.

Remote monitoring advantages

Remote monitoring systems are the most effective monitoring technology because they help you verify that everything is constantly stored at the correct temperature. You get a cost-effective early warning system, detailed data logs and trending data to demonstrate compliance.

Remote monitoring systems require a greater initial investment but cost far less when factoring in labor costs of manual recording and the “costs” of financial risk of compromised vaccines and other assets.

Validation, compliance and potential consequences

The CDC and local immunization programs are sending strong warning messages to hospitals and clinics to discard compromised vaccines. If the compromise happens while the vaccines are in storage at a hospital or clinic, that facility has to pay for the loss. Ultimately a practice will be held responsible for the thousands of dollars in losses if the log files and inventory are not properly recorded and documented. That can hit their bottom line hard.

For this reason, the pressure is on for vaccine providers to take the appropriate measures to store vaccines at the proper temperature and maintain that temperature until they are administered. They also need a system in place that documents their temperature history with hard data.

Thermal monitoring of the refrigerated items helps validate the cold chain. The CDC recommends and the VFC requires using calibrated temperature monitoring devices with a Certificate of Traceability and Calibration Testing. Once the device is installed, the CDC recommends that you do calibration testing every one to two years. A National Institute of Standards and Technology (NIST) traceable calibration performed by an A2LA or similarly accredited laboratory is the best way to ensure your data logger’s accuracy. Documentation is critical, so having a temperature data logger makes that process automatic and ongoing.

Cold medical assets like vaccines, pharmaceuticals and research samples are expensive and sometimes irreplaceable. Their temperature has to be maintained during storage until they are ready to be used. Remote monitoring systems and data loggers protect these assets 24/7 and provide an audit trail documenting their correct storage. The devices are so inexpensive to install and maintain, you can’t afford to be without this monitoring technology. 


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