A physiostimulator

A physiostimulator was a medical instrument in use aboard the USS Enterprise in 2268. It was used to stimulate cardiopulmonary and neural activity in comatose or near-comatose patients.

Though it was never made definitively clear in Star Trek: The Original Series, physiostimulators could be presumed to be of broader scope of usefulness and effect than cardiostimulators were.

Doctor Leonard McCoy used a physiostimulator to return Captain James T. Kirk to consciousness after the latter was subjected to a "Vulcan death grip" aboard a Romulan vessel. (TOS: "The Enterprise Incident")