Suspended animation for delayed resuscitation from prolonged cardiac arrest that is unresuscitable by standard cardiopulmonary-cerebral resuscitation

Standard cardiopulmonary-cerebral resuscitation fails to achieve restoratio n of spontaneous circulation in similar to 50% of normovolemic sudden cardi ac arrests outside hospitals and in essentially all victims of penetrating truncal trauma who exsanguinate rapidly to cardiac arrest Among cardiopulmo nary-cerebral resuscitation innovations since the 1960s, automatic external defibrillation, mild hypothermia, emergency (portable) cardiopulmonary byp ass, and suspended animation have potentials for clinical breakthrough effe cts. Suspended animation has been suggested for presently unresuscitable co nditions and consists of the rapid induction of preservation (using hypothe rmia with or without drugs) of viability of the brain, heart, and organism (within 5 mins of normothermic cardiac arrest no-flow), which increases the time available for transport and resuscitative surgery, followed by delaye d resuscitation. Since 1988, we have developed and used novel dog models of exsanguination cardiac arrest to explore suspended animation potentials wi th hypothermic and pharmacologic strategies using aortic cold flush and eme rgency portable cardiopulmonary bypass. Outcome evaluation was at 72 or 96 hrs after cardiac arrest Cardiopulmonary bypass cannot be initiated rapidly . A single aortic flush of cold saline (4 degreesC) at the start of cardiac arrest rapidly induced (depending on flush volume) mild-to-deep cerebral h ypothermia (35 degrees to 10 degreesC), without cardiopulmonary bypass, and preserved viability during a cardiac arrest no-flow period of up to 120 mi ns. In contrast, except for one antioxidant (Tempol), explorations of 14 di fferent drugs added to the aortic flush at roam temperature (24 degreesC) h ave thus far had disappointing outcome results. Profound hypothermia (10 de greesC) during 60-min cardiac arrest induced and reversed with cardiopulmon ary bypass achieved survival without functional or histologic brain damage. Further plans for the systematic development of suspended animation includ e the following: a) aortic flush, combining hypothermia with mechanism-spec ific drugs and novel fluids; b) extension of suspended animation by ultrapr ofound hypothermic preservation (0 degrees to 5 degreesC) with cardiopulmon ary bypass; c) development of the most effective suspended animation protoc ol for clinical trials in trauma patients with cardiac arrest; and d) modif ication of suspended animation protocols for possible use in normovolemic v entricular fibrillation cardiac arrest, in which attempts to achieve restor ation of spontaneous circulation by standard external cardiopulmonary resus citation-advanced life support have failed.