NEW YORK (Reuters Health) — A shock from a Taser doesn’t have any short-term adverse effects on healthy people, once its immobilising effects wear off, a new study shows.But the study, the first non-industry-funded investigation of the device in humans, doesn’t answer the question of how Taser use might affect extremely agitated people, those on illicit drugs like methamphetamine or cocaine, or individuals with heart problems.

“It’s a limited study. It’s a piece of the puzzle,” Dr. Gary Vilke of the University of California, San Diego Medical Center, the study’s lead author, told Reuters Health.

Concerns have been raised that Tasers and similar devices, which temporarily paralyse a person by disassociating the nervous and muscular systems with a five-second electrical shock and are used by roughly one third of US law enforcement agencies, might be a factor in some deaths of people in police custody.

To better understand how Taser exposure affects the heart and blood chemistry, Vilke and his colleagues examined 32 male and female volunteers before and one hour after they received a single five-second shock with the device.

Aside from a slight drop in blood pressure, which probably occurred due to anxiousness before the test, the researchers found no clinically significant changes in heart function or blood chemistry.

Vilke will present the findings this afternoon at the Society for Academic Emergency Medicine’s annual meeting in Chicago.

Acidity of the blood is a particular concern, Vilke noted in an interview. People agitated due to drug use or uncontrolled psychiatric disorders, or both, have increased blood acidity, while extreme exertion can also acidify the blood, he said. If the Taser further boosts blood acidity, he added, it could have harmful effects.

He and his colleagues are now planning to test the device in healthy people after vigorous exercise to approximate the agitated state of some individuals being taken into police custody.