Since general anesthesia first became widely used in late 1846, assessment of anesthetic depth was a problem.
To determine the depth of anesthesia, the anesthetist relies on a series of physical signs of the patient.
At that time, intravenous anesthetic agents were not yet in common use, and neuromuscular-blocking drugs were not used at all during general anesthesia.
It is divided into four planes: Stage IV: from stoppage of respiration till death.
Anesthetic overdose-caused medullary paralysis with respiratory arrest and vasomotor collapse.