Critical bleeding is a term used to describe a range of clinical scenarios where bleeding may result in significant patient morbidity or mortality. Broadly, critical bleeding falls into one of two categories (which may overlap):

• major haemorrhage that is life threatening and is likely to result in the need for massive transfusion
• haemorrhage of a smaller volume in a critical area or organ (e.g. intracranial, intraspinal or intraocular), resulting in patient morbidity or mortality.

For the purpose of this document, critical bleeding will refer only to the first category.