Suspended Animation - A Brief Review

Abstract Suspended animation (SA) is the temporary (short- or long-term) slowing or stopping of biological processes. Here, we will briefly review the current state of human long-term SA. There are two main fields where long-term SA constitutes an irreplaceable technology, namely manned deep space travel and cryonics, the cryopreservation of humans after clinical death with the aim to reanimate them in the future. In cryonics, much effort has been focused on the initial post-deanimation procedures collectively known as Standby, Stabilization and Transport (SST). Currently, shortly after death, bodies are stabilized and then transported to the cryopreservation organization, where cryoprotective perfusion takes place. Stabilization procedures range from covering the patient´s body with water ice, the simplest, to performing sophisticated procedures like emergency preservation and resuscitation (EPR) or deep hypothermic circulatory arrest (DHCA), in which the patient is taken to a condition of clinical death, characterized as electroencephalographic silence and cardiac arrest. The use of EPR and DHCA is unfeasible in the field. Experience shows that significant tissue damage occurs during the SST window. Bodies are finally placed in liquid nitrogen (-196 °C) for long-term storage. Concerning reanimation, the use of the nematode Caenorhabditis elegans (C elegans) is proposed as a suitable animal model for studying reanimation. These worms tolerate cryopreservation in LN and can be efficiently reanimated without affecting memory integrity. Thus, C elegans may allow us to explore the mechanisms that allow the nervous system of these worms to tolerate storage in LN, keeping the integrity of its memory after reanimation. Keywords: Spacetravel; Cryoprotection; CPA; Reanimation; EPR; DHCA; C elegans