Best Practices for Handling and Monitoring LN2 Containers Containing Reproductive Materials

Last year, after the 2018 loss of cryogenically stored human embryos at two plants in California and Ohio in 2018, experts were forced to reconsider the standards by which these facilities maintained their cryogenic systems. Eggschain, an Austin TX-based startup using blockchain technology to provide fertility clinic users and facilities secure tracking and record keeping, investigated the current procedures considered to be routine. Their report, “Best Practices and Policies for Handling and Monitoring Liquid Nitrogen Containers Containing Human Reproductive Specimens,” identifies imperative guidelines for facilities to ensure the safety of users’ samples via proper cryogenic equipment, alarm-monitoring systems and personnel training.

On March 3-4, 2018, disaster struck a facility in Ohio run by University Hospitals Cleveland Medical Center when a liquid nitrogen container holding biological samples experienced a “temperature fluctuation” that resulted in the loss of more than 4,000 eggs and embryos, which resulted in over 100 patient lawsuits.

The organization states that a remote alarm system had been turned off at an unknown time in the days before the accident. A similar situation occurred at the Pacific Fertility Clinic in San Francisco the same weekend. Afterwards, Eggschain advisors Dr. Kenneth Drury and Timothy Beals joined Wei Escala, Eggschain CEO and cofounder, to identify potential procedures and habits that could prevent future such accidents.

One of the primary focuses of the Best Practices report is the maintenance and monitoring of cryogenic equipment—namely liquid nitrogen containers used to store biological materials. While today’s liquid nitrogen storage units have become more reliable, the authors warn of the dangers involved in assuming perfect reliability and stability when operating containers and vapor shippers.

They identify factors that need to be considered to minimize and react to unexpected failures. Specifically, electrical and mechanical components can fail without warning, resulting in disastrous results like those in Ohio and California.

Best Practices dictates that an “In-house Validation Program” be established to define and verify a manufacturer’s specifications prior to the operation of any such container. The principal consideration is the actual level of liquid nitrogen in the system. Continuous monitoring is needed to ensure that, even while a unit is functioning, it is maintaining a suitable level of liquid nitrogen and, thus, cryogenic temperature.

A thorough in-house validation of a new liquid nitrogen tank considers vendor documentation, a visual check of the equipment, a vacuum reading, a sanitization of the tank and included inserts, a test of the liquid nitrogen evaporation phase hold, the addition of required temperature and level sensors, and a test of those sensors.

Other factors include neck opening measurements, static loss rate, static holding time, usable height, sample inventory capacity/type and the equipment’s empty versus loaded weight. The authors advise that users should not add any controller or device, like a liquid flow valve or solenoid, without seeking advice from a qualified cryogenics professional.

Beyond a thorough understanding of hardware, Best Practices illustrates the importance of practicing good handling and utilization techniques when accessing samples. As little as 30 seconds above -135 ˚C, the temperature for glass transition, can initiate the thawing process in samples. Establishing a system that includes not only storage and retrieval procedures, but paperwork and software processes, can minimize the length of time users need to access the system.

Considerations for procedural practices should include identifying the frequency at which a container can be accessed, taking into account liquid nitrogen “top off” schedules, determining whether or not the unit will be exposed to excessive movement to minimize damage to welds or vacuum space, and determining whether or not the sample inventory can be backed up or “split” between two containers in the event of a failure—it’s advised to have an ample number of backup units with a combined equal or larger size to contain samples in case of emergency.

Once they are in operation, it is vital to monitor these units continuously. Monitoring should be performed in real time with temperature sensors placed at the warmest spot of the unit—usually just below the neck opening. One of the key factors of a good monitoring system is a reliable alarm, both local and remote, that will notify technicians of rising temperatures. Alarms should be tested weekly.

Part of continuous monitoring is diligent record keeping: Best Practices suggests that daily, weekly, monthly and biannual inspections of sensors and liquid levels be performed and recorded along with sensor locations and dipstick measurements.

Best Practices concludes with four main points regarding performance evaluation and life expectancy. First, users should monitor and record liquid level and loss rate outside of the original manufacturer’s specifications to notice trends. Second, any signs of condensation should be documented and reported, along with frost or ice buildup, and if detected, users should begin preparing to move samples. Third, the authors advise that users monitor for any impending vacuum failure, usually noted by increases in “top off” frequency. Finally, facilities may consider implementing mandatory replacement times, often ten years, after which units must be replaced.

To read “Best Practices and Policies for Handling and Monitoring Liquid Nitrogen Containers Containing Human Reproductive Specimens.”on the CSA website, visit: Dr. Drury can be reached at ■