By Jörg Blech
In other experiments, scientists have already shown that the principle of suspended animation could revolutionize emergency medicine. Professor Behringer's research team in Vienna, for example, has focused its research efforts on saving people who collapse after a heart attack and then often die of cardiac failure. The Vienna researchers have replicated this process in animal experiments. Pigs are fully anesthetized and then given an electric shock to the chest, stopping the heart and replicating a heart attack.
After 15 minutes of complete cardiac arrest and 20 minutes of resuscitation using such conventional methods as heart compression massage, electroshocks and medication, the Viennese are able to revive very few of these pigs. And those that do make it end up having severe neurological damage.
The results are vastly superior when the researchers, before attempting resuscitation, flush three liters of saline solution into the main arteries of the lifeless pigs, thereby deliberately cooling down the brain and heart (in contrast to the experiments in Boston, these animals are not allowed to bleed to death). After a 20-minute waiting period -- simulating the time it might take to transport a trauma patient to a hospital emergency room -- the animals are connected to a heart-lung machine, reanimated, and then, using medication and ice cubes, kept in a recuperative state of semi-narcosis at a body temperature of 33° C (91.4° F) for 24 hours. Only then, says Behringer, are they "permitted to wake up again." Eighty-five percent of the pigs wake up, without significant consequential damage.
Hasan Alam's group, whose research is directed at saving people who would normally bleed to death, has reported similar results. In their experiments, the scientists used scalpels to inflict potentially fatal injuries on the pigs, then waited half an hour before beginning to suture the wounds. All the animals that received no cooling fluid died. Other pigs were quickly cooled from a body temperature of 37°C (98.6° F) to 10° C (50° F) in 28 minutes. Eighty-seven percent of these animals were saved with emergency surgery and revived after more than an hour.
The surviving pigs were given behavioral tests, which they passed with flying colors. They were able to find hidden raisins and apples just as effectively as normal control animals. Analyses of their brain tissue revealed that the pigs had survived their death-excursions without neurological damage.
All of this seems incompatible with the rules of biology. Until now it was considered incontrovertible that the brain will if it's deprived of oxygen for only a few minutes (four to five minutes in human beings). Heart cells and other tissue are also irreversibly destroyed if the oxygen supply drops below a critical level.
But it seems the shock of cold temperature can interrupt these processes. For every 10° C (18° F) drop in human body temperature, the metabolic rate drops by 50 percent. This reduction also slows down the process of dying, explains Hasan Alam. At a body temperature of 30°C (86° F), the brain can survive without oxygen for 20 minutes. Decrease the temperature to 10° C (50° F) and the brain can survive for as long as 90 to 120 minutes.
This phenomenon explains those legendary cases in which people have survived extremely long periods of oxygen deficiency. In the spring of 2000, for example, a three-year-old girl in a stroller rolled down an embankment and sank into the cold water of the Neckar River in southern Germany. The water temperature was 10° C (50° F). Even though the girl was under water for 45 minutes, emergency personnel were able to revive her. Scientists also know that heart attack patients' chances of survival increase when their bodies are cooled.
Researchers don't understand the details of why cold temperatures protect the body against death. They do know that metabolism continues in the body's cells for a short period of time after a person is already dead; but the remaining oxygen in the blood is no longer sufficient to produce energy. Instead, the cellular respiratory chain produces toxic free oxygen radicals at a higher rate than normal, killing the cells. In other words, the cellular metabolism continuing in a cell after death is in fact the cell's own downfall.
Apparently, the cool saline solution puts a stop to this process. First, the cold temperature dramatically reduces metabolic activity. Second, the solution completely flushes the blood and, along with it, the remaining oxygen out of the body tissue. There is nothing left to fuel the respiratory chain, and free radicals can no longer be produced to kill off the cells. The result? The body glides into a state of suspended animation.
Using the same logic, this sleep of death should also set in if cell respiration is interrupted by other means. This is precisely what 47-year-old cell biologist Mark Roth of the University of Washington in Seattle has demonstrated in a series of elegant experiments. To conduct the experiments, he used gases like carbon monoxide and hydrogen sulfide, which interfere in oxygen-consuming metabolic processes, binding to the same proteins and enzymes in the body and thus destroying cellular respiration.
When Roth administered a gaseous mixture of hydrogen sulfide and normal air to laboratory mice, the animals sank into an artificial hibernation. Their heart rates declined from 120 to 10 beats per minute. Their body temperatures dropped from 37° C (98.6° F) to as little as 15° C (59° F), which was slightly higher than the temperature in the room. After six hours, their metabolic rate had dropped by 90 percent. The resuscitation of these deep sleepers was remarkably simple. After being kept in fresh air and at normal room temperature, the mice woke up on their own and were as healthy as before. Roth plans to repeat his experiments with larger animals, and is ultimately aiming for human tests.
Just how long these excursions into the afterworld can be drawn out remains unknown. In any case, no one is likely to be booking trips to faraway galaxies anytime soon. It may be that the records achieved so far -- three hours in dogs and six hours in mice -- already represent the upper limit.
Freezing entire bodies in liquid nitrogen is not an alternative. In fact, scientists are now convinced that this approach is mistaken. Although human metabolism comes to an abrupt halt at -196° C (-320° F), ice crystals forming in the cells at this temperature destroy the tissue.
Of course, this discovery comes a bit late for those trusting souls who had their remains put to rest in nitrogen. "All those whose bodies were deliberately frozen," says Viennese physician and scientist Behringer, "will never be thawed and brought back to life."
Translated from the German by Christopher Sultan
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