But Pearl also notes that the MGH experiment leaves a lot of unanswered questions about the effects of the gas on humans. Mice are smaller than humans and may respond to the gas differently. Also, the mice in the experiment had no heart defects and didn’t undergo surgery. Furthermore, their brains weren’t assessed for a long enough time after the procedure. Some children who undergo long periods of blood flow stoppage to the brain, even when protected by cooling and seemingly fine post-operative care, experience “learning problems later in life,” Pearl says. Using hydrogen sulfide gas on humans “is an interesting concept,” he adds, “but that’s all it is at the moment.”
In fact, many heart surgeons are looking for ways to perform these complex operations while keeping the blood flowing to the brain, rather than searching for methods like gas or cooling to prevent brain damage from stopping the flow.
The MGH group will present their results this week at the American Physiological Society conference in Virginia Beach, VA. And they plan to keep investigating the gas technique; they will measure how long mice can stay under its influence with no harm to body, brain, or behavior; test different gas concentrations; and assess whether the gas is safe and effective on larger mammals such as pigs and sheep. “If this doesn’t work in bigger animals, that may be the end of the story,” Ichinose says.