Suspended Animation: Fact or fiction?

The Lazarus effect

The first preliminary experiment Roth carried out was to measure the development of zebrafish embryos under anoxic conditions in the absence of oxygen. He discovered that their development came to a halt and the heart was shut down. He found that the embryos could survive for 24 hours and then resume normal development after re-exposure to oxygen.

These dangerously low levels of oxygen appear to kill the animals but they recover later. Roth notes that a similar 'Lazarus effect' has been observed in patients such as those mentioned above who have been pronounced dead after exposure to extreme cold.

When the oxygen levels are too low for respiration but high enough to allow metabolic activity, damage occurs because the cells continue to struggle to live. Under these conditions, seizures, cell death, coma and finally death can occur.

However, decreasing the oxygen levels significantly stops all metabolic activity and the animals enter a state of suspended animation.

Roth then decided to try low doses of the gas to induce suspended animation in mice. He found that he could reversibly reduce the metabolic rate of mice by first exposing them to 80 parts per million of hydrogen sulfide and then exposing them to low oxygen.

In just a matter of minutes, mice entered into what is called a "hibernation-like" state, where their core temperature was reduced to 11 degrees and their respiration dropped from the normal 120 breaths per minute to 10 or less breaths per minute.

In his preliminary mammal experiments, Roth kept the animals in this state for 6 hours and they recovered completely. After the gas was removed, normal metabolic function and activity resumed. In both of these studies, he found discrete and lethal oxygen levels exist just above the oxygen level that enables suspended animation.

Uses for suspended animation

Reduced levels of oxygen supply specifically, can be a major cause of cellular and tissue damage in donor organs and in the bodies of individuals that have suffered severe blood loss or blood flow obstruction in such cases as strokes or heart attacks.

In cases such as these, restoring an adequate oxygen supply is not always easy. In the future, agents such as hydrogen sulfide that alter the metabolic rate of mammals by reducing the need for oxygen could prevent tissue damage and death in stroke or heart attack victims, preserve transplantable organs for longer and buy time for human trauma patients.

In addition, exposure to hydrogen sulfide may improve cancer treatment by allowing patients to tolerate higher radiation doses without damaging healthy cells. Cancer cells aren't dependent on oxygen to grow and are therefore more resistant to radiation than surrounding healthy cells, which need oxygen to live.

Roth hypothesizes that temporarily reducing oxygen consumption in healthy cells could make them a less-vulnerable target for radiation and chemotherapy and thus spare normal tissue during high-dose cancer therapy.

This work could also be used to put astronauts in suspended animation on long space flights thereby decreasing the need for food and oxygen.

The Future of Suspended Animation

Dr. Mark Roth's discovery of this novel way of inducing reversible metabolic hibernation has sparked interest in the idea of suspended animation. Based on the stories of individuals reviving after being in a hypothermic state, researchers in other institutions hypothesized that significantly decreasing body temperature induces suspended animation. However, after carrying out hypothermic experiments, they discovered that this can only be done for a short amount of time and even then, there is a risk of tissue and brain damage.

Chemically induced suspended animation seems to be the method of choice to achieve a state of metabolic hibernation. Researchers at Massachusetts General Hospital have repeated the hydrogen sulfide studies of Dr. Roth and have obtained the same results. Thus far, no ill side effects have been observed Further development of this method could have a tremendous impact in the fields of critical care, neurological, surgical and organ transplant medicine.

For more information

BBC - Fish in Suspended animation
BBC News/

Syndney Morning Herald - Doctors claim suspended animation success
www.smh.com.au