Standard cardiopulmonary-cerebral
resuscitation fails to achieve restoration of spontaneous circulation in approximately 50% of normovolemic sudden cardiac arrests outside hospitals and in essentially all victims of penetrating truncal
trauma who exsanguinate rapidly to
cardiac arrest. Among cardiopulmonary-cerebral
resuscitation innovations since the 1960s, automatic external defibrillation, mild
hypothermia, emergency (portable)
cardiopulmonary bypass, and suspended animation have potentials for clinical breakthrough effects. Suspended animation has been suggested for presently unresuscitable conditions and consists of the rapid induction of preservation (using
hypothermia 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 delayed
resuscitation. Since 1988, we have developed and used novel dog models of
exsanguination cardiac arrest to explore suspended animation potentials with hypothermic and pharmacologic strategies using aortic cold flush and emergency 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 degrees C) at the start of
cardiac arrest rapidly induced (depending on flush volume) mild-to-deep cerebral
hypothermia (35 degrees to 10 degrees C), without
cardiopulmonary bypass, and preserved viability during a
cardiac arrest no-flow period of up to 120 mins. In contrast, except for one
antioxidant (
Tempol), explorations of 14 different drugs added to the aortic flush at room temperature (24 degrees C) have thus far had disappointing outcome results. Profound
hypothermia (10 degrees C) during 60-min
cardiac arrest induced and reversed with
cardiopulmonary bypass achieved survival without functional or histologic brain damage. Further plans for the systematic development of suspended animation include the following: a) aortic flush, combining
hypothermia with mechanism-specific drugs and novel fluids; b) extension of suspended animation by ultraprofound hypothermic preservation (0 degrees to 5 degrees C) with
cardiopulmonary bypass; c) development of the most effective suspended animation protocol for clinical trials in
trauma patients with
cardiac arrest; and d) modification of suspended animation protocols for possible use in normovolemic
ventricular fibrillation cardiac arrest, in which attempts to achieve restoration of spontaneous circulation by standard external
cardiopulmonary resuscitation-advanced life support have failed.