الفهرس 
Pathophysiology of Polytrauma and Hemorrhagic Shock
Pathophysiology of HypovolemicOnly 14 pages are availabe for public view
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Abstract
Hemorrhage is the most common preventable cause of death in the setting of trauma.
During recent decades, despite our increasing knowledge of the pathophysiology of hemorrhagic shock in trauma patients, the mortality rate continues to remain high.
About one-third of trauma patients will develop a coagulopathy if their hemorrhage leads to multiple organ failure (MOF).
Goals of treatment in trauma patients remain avoiding metabolic acidosis, hypothermia, treating coagulopathy and stabilizing the patient as soon as possible.
Adequate volume therapy appears to be fundamental in the management of the trauma patient.
A large volume crystalloid resuscitation, followed by several units of packed red blood cells then a modest amount of fresh frozen plasma and platelets was accepted as the standard for decades. This is no longer considered appropriate.
Resuscitation of the severely injured patient is a topic of ongoing evolution and controversy.
The choice of fluid therapy engenders the most controversy, and an examination of the body of literature on this subject results in confusion.
Irreversible tissue damage, and even death, may occur despite adequate but delayed resuscitation.
It is recommended that rather than concentrating on fluid protocols, ambulance services should avoid unnecessary delays and speed up transfer to definitive care in the hospital.
In the last few years, there has been a paradigm shift in the management of the severely injured trauma patient. As our understanding of the nature of trauma-related coagulopathy evolved, and with the recent combat trauma experiences, the concept of DCR in trauma was born. Damage control resuscitation (DCR), a combination of permissive hypotension, hemostatic resuscitation and damage control surgery, has been introduced to treat severely traumatized patients in hemorrhagic shock.
Human albumin is the most expensive plasma substitute and has been shown to be a safe plasma substitute؛ however, no beneficial effects on perfusion, inflammation، tissue Edema or organ function and no beneficial effects on morbidity, mortality or the length of stay in ICU have been demonstrated in humans.
Although there is convincing evidence that blood volume is restored more rapidly with colloids than with crystalloids and colloids are also more efficient to improve microcirculation, crystalloids are still often recommended as the first choice to treat hemorrhage.
Using high doses of crystalloids is associated with the risk of fluid overload, and using saline solution is associated with the risk of hyperchloremic acidosis.
Crystalloids are often recommended for treating hypovolemia because they are cheap and are suggested to have only few side effects. Delayed and inadequate restoration of intravascular circulating volume by crystalloids, however, Have been shown to worsen microvascular flow, endothelial integrity, and tissue oxygenation.
HES: The benefit of using HES has been refuted. To the contrary, HES is associated with increased harm. Though it is not clearly associated with increase in mortality, evidence clearly shows increased AKI and use of RRT associated with the use of HES. It is further associated with coagulopathy and increased use of blood transfusion. The effects seem to be dose dependent, but no consensus has been reached as to a safe dose of HES. As such, the use of HES in resuscitation should be avoided.
0.9% saline: The use of NS has been shown to be associated with development of hyperchloremic metabolic acidosis and increased risk of AKI in susceptible patients, especially those with diabetic ketoacidosis. This risk is decreased when balanced salt solutions are used. The use of balanced crystalloid solutions rather than NS when possible should be considered in these populations.
Fluid resuscitation should be applied in a goal-directed manner and targeted to physiologic needs of individual patients. Studies show improved outcomes with the use of goal-directed therapy over fluid-liberal approach.