In Act 5 scene 5 how does Macbeth react to the news that his queen is dead?
Macbeth already knew that the queen was not doing well. In act 5, scene 3, the Doctor tells him that Lady Macbeth is "troubled with thick-coming fancies / That keep her from her rest" (5.3.47-48). Macbeth, in reply, does not really display anything that looks like compassion. He essentially tells the doctor to fix it. He asks,
Canst thou not minister to a mind diseased, . . .
And with some sweet oblivious antidote
Cleanse the stuffed bosom of that perilous stuff
Which weighs upon the heart? (5.3.50-53)
In other words, he just wants the doctor to give Lady Macbeth something to make her feel better, less guilty, to make her "oblivious"—so, perhaps, to make her feel nothing at all; either way, his reply seems to me to lack any real concern for the state of his wife's health. Therefore, when he learns that she is dead, I interpret his words to be the verbal equivalent of a shoulder shrug. He says,
She should have died hereafter.
There would have been a time for such a word. (5.5.20-21)
"Should" seems to me to mean "would" here, and he means that she would have died sometime later regardless, and so the news—or "word"—of her death would have come at that time. However, it seems like all the same to him: now or later, she's dead, and the news is likely not unexpected given that Macbeth was aware of the Doctor's inability to help her.
Macbeth's reaction to the news that his wife is dead is sadness mixed with regret. He says, "She should have died hereafter; / There would have been a time for such a word." He means that he wishes she would have died when he had the time to properly mourn her. He goes on then to bemoan the current state of his life; how everything has gone badly and life has lost its meaning. He has become a man driven by his own ambition run amuck as though he were in a car he started but now the gas pedal is stuck fully to the floor and he can't stop it. The only course of action he can take now is to try to preserve his own life because that is all he has left. And that, he observes, is pretty much meaningless.
Of course there is sadness, but I have always read this as Macbeth reacts in a sort of "Well, she would have died sooner or later, but this is really bad timing" attitude. He is busy preparing for battle with Macduff and his armies. However, he does take time in his famous "tomorrow, tomorrow, and tomorrow" speech to say that if he and Lady Macbeth had remained honorable, perhaps their deaths could be more dignified than they are destined to be. They should be receiving rewards and accolades in their old age, but instead, they are mostly alone and unrespected due to what they have done.
Macbeth's reaction to the death of his wife is very different from what we, as an audience expect from a man who shared a very intimate and close understanding with his better half. Macbeth, early in the play, derived trememdous insipration from, and was heavily influenced by his wife, Lady Macbeth, who then, seemed to be one of the most ruthless, power-hungry female characters created by Shakespeare.
However, it were the circumstances coupled with his loss in faith concerning his kingship and lack of military support that caused him to evolve into a different individual who reacted to his wife's death in a very stoic fashion.
He said that she was to die some day or the other. He also said that death was like an 'illusion' and that the passing of everyday brought a man closer and closer to his impending death. He says that death is like an actor who worries about his time on stage and then ultimately is never heard from ever again, in other words, all achievements, fulfilled dreams and conquered hopes in one's life pose no barrier to the coming of death. He also says that death is like a story told by an idiot full of enery and emotional disturbance, but devoid of any true meaning.