1. The nurse had returned to the operating room before the operation 
started.
2. He did not bandage (he wasn't bandaging-это если показать нужно процесс, который прервался другим действием=кровь пошла)the limb when the bleeding started again.
3. The blood had been transfused by 5 o’clock yesterday.
4. When the assistant came to the laboratory a few glasses had already exploded.
5. The boy had fractured his leg before the help came.
6. We will have held our meeting by the end of the next week.
7. He will have incised the tissues by the time our teacher comes.
8. I will be drawing the scheme of the neuralgia cells today 5 o’clock.
9. By two o’clock the surgeon will have performed appendectomy.(это если в будущем времени, то есть= К двум часам хирург закончит удалять аппендицит, а если по отношению к прошлому времени, тогда By two o'clock(yesterday) the surgeon had performed appendectomy)