Temperature change in cryo-containers during short exposure to ambient temperatures

Times have been defined for the handling of 0.25 ml embryo cryostraws and semen, in either 0.5 ml cryostraws or 1.0 ml cryovials containing 0.5 ml material, before potentially detrimental changes in temperature take place. When handling cryovials the time lag is relatively long, with 78.8 +/- 2.6 s being available to manipulate the vials before -80 degrees C is reached and 335.4 +/- 3. 8 s until the eutectic point (approximately -7 degrees C) is reached. However the situation with cryostraws is less tolerant. Both 0.25 and 0.5 ml versions reach temperatures >-80 degrees C within 40 s, and the eutectic point is reached in 79.0 +/- 2.0 s in 0.25 ml cryostraws. These time/temperature data have proved useful in educating new technicians, as well as clinicians and nurses who may also handle frozen human material, in the need to minimize the ambient temperature exposure time of stored specimens so as to maintain optimal post-thaw viability.