Cold chain monitoring during cold transportation of human corneas for transplantation

Background. As recommended by international standards the cornea should be maintained in a specific temperature range (2degrees-8degreesC) to guarantee its viability. However, there is no standard packaging method to maintain these conditions during transport. Our packaging system is similar to those used by the main eye banks in Spain and elsewhere in Europe. The objective is to monitor the cold chain in the current packaging method to validate the maintenance of temperature within the adequate range for a minimum 24-hour period. Methods. The effects of the following variables were studied: number and freezing temperature of the cold packs; air volume in the packaging system; position of the cornea in the packaging system; and the wall section of the container. Exterior temperature was maintained constant at 20degrees to 24degreesC. The cold chain was monitored using a device that measures temperature continuously and for which a histogram of temperature variation can be downloaded to a computer for further analysis. Results. When the cold packs were frozen to -40degreesC or the number of cold packs increased to four, the temperature decreased quickly to 0degreesC and the transport period was not prolonged. The main objective was to improve isolation by reducing inner air volume, and maintaining the position of the cornea in the container. Conclusions. The currently used cold packaging systems (not frozen, 4degreesC) do not maintain the temperature within the accepted range for the required distribution period. The improved system maintains the cornea at between 2degreesC and 6degreesC for a minimum of 24 hours.