Welcome to HealthcareMagic forum.
The effects of anesthesia
take times to wean off completely. The anesthetic
drugs gets metabolized and excreted out of the body system - bringing the consciousness back to the patients.
The metabolising time varies individually and is proportional to the amount of drugs used, the duration of procedure and presence of other comorbid condition. At an average, during brain surgeries it may last for 6 - 24 hours. Further brain surgery
causes brain edema
which can cause drowsiness
and sleepiness. In any neurological setup, the level of consciousness is documented using a scale known as Glassgow Coma Scale (GCS). Here the level is monitored between 3 and 15 - 3 being comatose and 15 indicate full consciousness.
I expect the medical staff to keep a track of his GCS score periodically. If his GCS score is periodically increasing, then I do not think there is something to worry.
Further if he is breathing on himself and not on a ventilator, it is a good indication that all is well.
Discuss with his treating doctors / medical staffs about these parameters. You can learn about his condition with these factors.
Hope this helps.
Best wishes for his recovery!!!