Was Lazarus in a coma?
The short answer is no.
In fact the Gospel according to St. John is very clear on the subject matter.
The resurrection of Lazarus is one of Jesus’ public miracles. Being in a coma would not have made such a great manifestation of Jesus’ power to make the impossible possible. People occasionally come out of comas. People do not normally raise from the the dead!
Jesus’ words to his apostles were very clear on this issue: ”Then therefore Jesus said to them plainly: Lazarus is dead.”
11 Now there was a certain man sick, named Lazarus, of Bethania, of the town of Mary and Martha her sister.
2 (And Mary was she that anointed the Lord with ointment, and wiped his feet with her hair: whose brother Lazarus was sick.)
3 His sisters therefore sent to him, saying: Lord, behold, he whom thou lovest is sick.
4 And Jesus hearing it, said to them: This sickness is not unto death, but for the glory of God: that the Son of God may be glorified by it.
5 Now Jesus loved Martha, and her sister Mary, and Lazarus.
6 When he had heard therefore that he was sick, he still remained in the same place two days.
11 These things he said; and after that he said to them: Lazarus our friend sleepeth; but I go that I may awake him out of sleep.
12 His disciples therefore said: Lord, if he sleep, he shall do well.
13 But Jesus spoke of his death; and they thought that he spoke of the repose of sleep.
14 Then therefore Jesus said to them plainly: Lazarus is dead.
15 And I am glad, for your sakes, that I was not there, that you may believe: but let us go to him.
32 When Mary therefore was come where Jesus was, seeing him, she fell down at his feet, and saith to him: Lord, if thou hadst been here, my brother had not died.
33 Jesus, therefore, when he saw her weeping, and the Jews that were come with her, weeping, groaned in the spirit, and troubled himself,
34 And said: Where have you laid him? They say to him: Lord, come and see.
35 And Jesus wept.
36 The Jews therefore said: Behold how he loved him.
37 But some of them said: Could not he that opened the eyes of the man born blind, have caused that this man should not die?
38 Jesus therefore again groaning in himself, cometh to the sepulchre. Now it was a cave; and a stone was laid over it.
39 Jesus saith: Take away the stone. Martha, the sister of him that was dead, saith to him: Lord, by this time he stinketh, for he is now of four days.
40 Jesus saith to her: Did not I say to thee, that if thou believe, thou shalt see the glory of God?
41 They took therefore the stone away. And Jesus lifting up his eyes said: Father, I give thee thanks that thou hast heard me.
42 And I knew that thou hearest me always; but because of the people who stand about have I said it, that they may believe that thou hast sent me.
43 When he had said these things, he cried with a loud voice: Lazarus, come forth.
44 And presently he that had been dead came forth, bound feet and hands with winding bands; and his face was bound about with a napkin. Jesus said to them: Loose him, and let him go.
45 Many therefore of the Jews, who were come to Mary and Martha, and had seen the things that Jesus did, believed in him. - John 11:1-6;11-15;32-45
Now if Jesus said plainly that Jesus said that Lazarus is dead, it is not possible that Lazarus was in a coma.
St. Augustine equally wrote (quoted in St. Thomas Aquinas's Catena Aurea on John 11):
He then declares His meaning openly: Then said Jesus to them plainly, Lazarus is dead.
He had been sent for to restore Lazarus from sickness, not from death. But how could the death be hid from Him, into whose hands the soul of the dead had flown? And I am glad for your sakes that I was not there, that you might believe; i.e. seeing My marvelous power of knowing a thing I have neither seen nor heard. The disciples already believed in Him in consequence of His miracles; so that their faith had not now to begin, but only to increase. That you might believe, means, believe more deeply, more firmly.
Theophylactus in the same source is quoted as the following:
Some have understood this place thus. I rejoice, He says, for your sakes; for if I had been there, I should have only cured a sick man; which is but an inferior sign of power. But since in My absence he has died, you will now see that I can raise even the dead putrefying body, and your faith will be strengthened.
Thus Lazarus was dead and not in a coma!