pressure of 70–90 mmHg, or the re-establishment of peripheral pulses and adequate ability to think. Hypertonic saline has been studied and found to be of little difference from normal saline. As no intravenous fluids used for initial resuscitation have been shown to be superior, warmed Lactated Ringer's solution continues to be the solution of choice. If blood products are needed, a greater use of fresh frozen plasma and platelets instead of only packed red blood cells has been found to improve survival and lower overall blood product use; a ratio of 1:1:1 is recommended. The success of platelets has been attributed to the fact that they may prevent coagulopathy from developing. Cell salvage and autotransfusion also may be used. Blood substitutes such as hemoglobin-based oxygen carriers are in development; however, as of 2013 there are none available for commercial use in North America or Europe. These products are only available for general use in South Africa and Russia. Medications Tranexamic acid decreases death in people who are having ongoing bleeding due to trauma, as well as those with mild to moderate traumatic brain injury and evidence of intracranial bleeding on CT scan. It only appears to be beneficial, however, if administered within the first three hours after trauma. For severe bleeding, for example from bleeding disorders, recombinant factor VIIaa protein that assists blood clottingmay be appropriate. While it decreases blood use, it does not appear to decrease the mortality rate. In those without previous factor VII deficiency, its use is not recommended outside of trial situations. Other medications may be used in conjunction with other procedures to stabilize a person who has sustained a significant injury. While positive inotropic medications such as norepinephrine sometimes are used in hemorrhagic shock as a result of trauma, there is a lack of evidence for their use. Therefore, as of 2012 they have not been recommended. Allowing a low blood pressure may be preferred in some situations. Surgery The decision whether to perform surgery is determined by the extent of the damage and the anatomical location of the injury. Bleeding must be controlled before definitive repair may occur. Damage control surgery is used to manage severe trauma in which there is a cycle of metabolic acidosis, hypothermia, and hypotension that may lead to death, if not corrected. The main principle of the procedure involves performing the fewest procedures to save life and limb; less