After trauma, hypovolemic shock can be due to all EXCEPT:
Head injury REF: Fluid and Electrolyte Balance by Norma Metheny, Norma Milligan Metheny Page 221 Losing about 1/5 or more of the normal amount of blood in your body causes hypovolemic shock. Intracranial injuries alone do not produce circulatory inadequacy until brain stem and its reticular activating system is profoundly involved. Therefore the presence of shock in a head injury patient indicates a search for another cause.
Pelvic fracture
Head injury
Blunt trauma to abdominal viscera
Hemothorax