Heart Trouble in Space?

To help protect their health during their extraterrestrial explorations, U.S. astronauts routinely go on special diets prior to launch. The Apollo 16 crew that landed on the moon last week has been on an even more highly specialized diet than usual. For three days before blastoff, the trio ate foods laced with potassium, and even the eggs in their farewell omelets came from hens raised on high-potassium feeds. Their in-flight food was similarly seasoned. The astronauts are not complaining; Ken Mattingly told Mission Control that the potassium even added a certain zest to his tomato soup.

The reason for the astronauts' unusual diet is cautionary rather than culinary. Two members of Apollo 15's crew went through brief periods of heartbeat irregularities, and NASA doctors suspected the reason. The two men who suffered the problem had lost 15% of their normal potassium. They were also the ones who landed and worked on the moon. Potassium, a body salt that affects the electrical conductivity of the heart, is essential to controlling cardiac rhythm.

Most people lose some potassium when subjected to stress, which steps up the body's output of adrenal hormones and leads to increased elimination of the crucial salt. The astronauts, of course, go through heavy physical and emotional strain, and they face another problem as well. The weightlessness experienced in space causes the blood, which normally tends to pool in the lower extremities, to be distributed more evenly. The body senses this redistribution, reacts as if it were carrying excess fluids and attempts to redress matters by extra urination. That causes further potassium loss.

NASA's director of life sciences, Dr. Charles Berry, is unable to explain why the potassium-loss problem, which had not bothered members of earlier missions, surfaced during the last Apollo flight. But the astronauts' physician was determined not to let it become a hazard for Apollo 16. In addition to replenishing the crew's lost potassium through diet, Berry has safeguarded the spacemen by setting up an emergency cardiology service to monitor their heartbeats and transmit their electrocardiograms by telephone to two heart specialists. He has also supplied the astronauts with drugs to be used if the monitors show cardiac irregularities.

Berry hopes his precautions will make medication unnecessary. "Prescribing a cardiac drug on the lunar surface from 250,000 miles away would be a first that I would prefer to avoid," he says. But Berry hopes to score a first by learning--with greater precision than last time--how much potassium is lost by astronauts traveling and working in space. To do this, he determined the preflight potassium levels of each of the Apollo 16 astronauts. He has also asked them to bring back urine samples from a test to be conducted during the flight, and is confident that a comparison of the two levels will prove significant. "Those urine bags," says Berry with a researcher's peculiar enthusiasm, "are pure gold."

This file is automatically generated by a robot program, so reader's discretion is required.