Temperature Excursions in Cold Chain Management-Assessing the Accuracy of Refrigerator Temperature Probes

Background: Medications requiring refrigeration for stability are commonly used across hospitals. Temperature-sensitive medications may not have their temperature requirements maintained due to breaches in the cold chain, especially refrigerator failure. This is usually caused by malfunction of the refrigerator unit or by power outage. After multiple power outages at our institution involving refrigerators with temperature probes located in different areas of the refrigerator, we hypothesised that the fixed temperature probe may not accurately reflect the temperature of the medications themselves. Methods: We conducted simulations of power outages in a commonly used medication refrigerator, using additional temperature data loggers, placed on the refrigerator shelf and inside a cardboard box to replicate the temperature inside medication containers to determine if there was a difference in the time to breach cold chain conditions (>8 degrees C) and to return to appropriate refrigerated temperatures (<8 degrees C) when power was restored. Results: All data loggers took a longer time to breach cold chain conditions than the refrigerator probe (12.5 minutes vs 23-26 minutes) but took longer to return to acceptable temperature after power was restored (17.5 minutes vs 70.5-89 minutes). Conclusion: This exploratory research suggests that temperatures vary within a refrigerator depending on the type and location of probe and that medications within may take longer to breach cold chain conditions but also take longer to return to cold chain conditions compared with fixed refrigerator temperature probes. Further research is required to determine whether these variations occur across different sizes/brands of refrigerators and the effect on stability on refrigerated medications.