The new vitrification and warming protocols: when rapid is not really rapid.

New vitrification and warming protocols have recently been developed to shorten procedure times and reduce exposure to potentially harmful cryoprotectants (CPA). These protocols are often described as 'rapid' or 'ultra-fast' but these terms are misleading. Speed-related terminology in cryopreservation has historically referred to cooling and warming rates, and not the length of time samples spend in solutions. Using 'rapid' warming or 'ultra-fast' vitrification implies that the speed at which a sample goes from cryogenic temperature (-196°C) to body temperature (37°C) or vice versa has been increased. However, most newly proposed protocols shorten exposure times or eliminate steps without altering thermal kinetics or CPA uptake and removal dynamics. Calling them 'rapid' causes confusion and may mislead practitioners. Instead, protocols that only reduce time in CPA solutions or omit steps should be called 'shortened protocols'. Precise language is crucial to ensure clear communication, accurate data interpretation and proper clinical practice. Only protocols that physically speed up cooling or warming rates should be labelled 'rapid' or 'ultra-fast'.