What would you call this specific war scene effect?

The Freeze Response.

What you are seeing in this scene is the freeze response--a human/animal response to danger or threats in which the subject freezes and assumes a defensive posture. We often think of threat response in terms of fight or flight, but it is more accurate to say fight, flight, or freeze. The cinematic alterations to the character's perception--blurring, loss of clarity in sound, time slowing--may be Hollywood license to show the character is frozen in fear and not just sitting there; however, this paper indicates that the freeze response causes those suffering from it to process coarse information but not detailed information. This might indeed cause sound to seem more distant and more like a dull roar and vision to seem blurred. As for things slowing down, that is a trick our memory plays on us when we recall dangerous situations. People who have frozen in combat may sometimes recall time slowing down for them in that situation.

This is referred to in the military as "Shell Shock". To quote a piece of the wiki:

The term "shell shock" came into use to reflect an assumed link between the symptoms and the effects of explosions from artillery shells. The term was first published in 1915 in an article in The Lancet by Charles Myers. Some 60–80% of shell shock cases displayed acute neurasthenia, while 10% displayed what would now be termed symptoms of conversion disorder, including mutism and fugue.