Bleeding: Types of bleeding

Causes, prevalence, and risk factors
Hemorrhage generally becomes dangerous, or even fatal, when it causes hypovolemia (low blood volume) or hypotension (low blood pressure). In these scenarios various mechanisms come into play to maintain the body's homeostasis. These include the "retro-stress-relaxation" mechanism of cardiac muscle, the baroreceptor reflex and renal and endocrine responses such as the renin - angiotensin - aldosterone system (RAAS).

Certain diseases or medical conditions, such as haemophilia and low platelet count (thrombocytopenia) may increase the risk of bleeding or may allow otherwise minor bleeds to become health or life threatening. Anticoagulant medications, such as warfarin can mimic the effects of haemophilia, preventing clotting, and allowing free blood flow.

Death from hemorrhage can generally occur surprisingly quickly. This is because of 'positive feedback'. An example of this is 'cardiac repression', when poor heart contraction depletes blood flow to the heart, causing even poorer heart contraction. This kind of effect causes death to occur more quickly than expected.