Complex sentence: The key is to prevent exacerbation of hemorrhaging until definitive vascular control can be achieved, the theory being that if clots have formed within a vessel then increasing the patients blood pressure might dislodge those established clots resulting in more significant bleeding.
Split into simpler sentences: The key is to prevent exacerbation of hemorrhaging until definitive vascular control can be achieved. The theory being that if clots have formed within a vessel then increasing the patients blood pressure might dislodge those established clots resulting in more significant bleeding.