When a hospital does a barrage of tests after being admitted for passing out does it mean that they are concerned that something serious is wrong?

When my mother was 83 she passed out and was taken to the hospital where they gave her all the tests for a TIA or mini stroke. They also took blood and urine analysis to determine if there was an infection. My understanding is that infections ( in her case a urinary tract infection), can cause severe dehydration which in turn can cause a sudden drop in blood pressure and cause a person to pass out, that is exactly what happened to her.