Which feature was absent in the initial use of ECT?

The correct choice highlights that muscle relaxation was not a feature in the initial use of electroconvulsive therapy (ECT). In the early days of ECT, the procedure involved administering electrical shocks without pre-treatment measures that would provide muscle relaxation. As a result, patients would often experience intense muscle contractions during the induced seizures, which could lead to complications such as fractures or muscle injuries.

Over time, the practice of ECT evolved, and the importance of muscle relaxation became recognized, leading to the use of muscle relaxants prior to treatment. This change greatly improved the safety and comfort of the procedure. Other practices, such as safety protocols, informed consent, and monitoring vital signs, were either established or became standard in later adaptations of ECT to enhance patient safety and ethical considerations, but muscle relaxation was not a standard practice at the outset.