Achieving a balance between organ perfusion and hemostasis is critical for optimal fluid resuscitation in patients with severe trauma. The concept of "permissive hypotension" refers to managing trauma patients by restricting the amount of resuscitation fluid and maintaining blood pressure in the lower than normal range if there is continuing bleeding during the acute period of injury. This treatment approach may avoid the adverse effects of early, high-dose fluid resuscitation, such as dilutional coagulopathy and acceleration of hemorrhage, but does carry the potential risk of tissue hypoperfusion. Current clinical guidelines recommend the use of permissive hypotension and controlled resuscitation. However, it is not mentioned which subjects would receive most benefit from this approach, when considering factors such as age, injury mechanism, setting, or the presence or absence of hypotension. Recently, two randomized clinical trials examined the efficacy of titrating blood pressure in younger patients with shock secondary to either penetrating or blunt injury; in both trials, overall mortality was not improved. Another two major clinical trials suggest that controlled resuscitation may be safe in patients with blunt injury in the pre-hospital setting and possibly lead to improved outcomes, especially in patients with pre-hospital hypotension. Some animal studies suggest that hypotensive resuscitation may improve outcomes in subjects with penetrating injury where bleeding occurs from only one site. On the other hand, hypotensive resuscitation in blunt trauma may worsen outcomes due to tissue hypoperfusion. The influence of these approaches on coagulation has not been sufficiently examined, even in animal studies. The effectiveness of permissive hypotension/hypotensive resuscitation and restricted/controlled resuscitation is still inconclusive, even when examining systematic reviews and meta-analyses. Further investigation is needed to elucidate the effectiveness of these approaches, so as to develop improved treatment strategies which take into account coagulopathy in the pathophysiology of trauma.
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