He realizado la siguiente búsqueda en Google:

• http://www.google.com/search?num=20&hl=en&site=webhp&q="pati...

Las comillas agrupan términos y he eliminado de la búsqueda la posibilidad de que el texto contenga "light headed". Los textos hallados indican que "light" se refiere a una reducción de los efectos de la anestesia (digamos que es lo opuesto de "heavily under anesthesia"). Cito algunas instancias fuera de contexto:

• appellee became anesthetically "light" during the procedure.
• he never saw appellee move or become light
– http://www.leagle.com/decision/1991988200GaApp788_1715

• Said patient became "light" and experienced "bucking" during the course of the operative procedure.
– http://phes.co/IMP files/DHFiles/0101029836Order10051988.pdf

• Dr. Rice testified the patient started kicking during the procedure and several people had to restrain him. He stated it was not unusual for a patient to "become light" for 15 to 30 seconds but it was unusual for the patient to remain light for several minutes, as occurred in this case. He stated the operation had to be interrupted for 2 to 3 minutes because of the excessive movement. He recalls Dr. Davies ordering the anesthetic to be increased and remembers the patient quieting down some but stated the patient never went "completely back under."
– http://www.leagle.com/decision/19811614405So2d1209_11404

• In some cases the patient became light during surgery. In such cases 10 cc. of the solution were administered rapidly and the patient returned to a deep sleep.
– http://www.google.com.br/patents/US4017619

Entonces, no es desacertada la sugerencia de DLyons de utilizar "semiconsciente", excepto que este término solamente se refiere a una reducción del estado hipnótico de la anestesia y no a la de sus efectos analgésicos y miorrelajantes. Como vemos en los textos anteriores, el paciente "light" también comienza a moverse, para lo cual no necesariamente hay que estar consciente. ¡Necesitamos algo que comunique la idea de "subanestesiado/desanestesiado"!