During the primary survey of the patient in hemorrhagic shock, a circulatory assessment should include the insertion of two large bore IVs (16-18 gauge) bilaterally to facilitate the fastest administration of fluids.  If this is not available, then a large bore CVC such as a Cordis or a standard 7 French triple lumen CVC should be placed.  The reason which 2 large bore peripheral IVs is more successful than a CVC in rapid fluid resuscitation is due to Poiseuille’s law which states that fluids passing through a lumen can be transfused most quickly when there is laminar flow (width and length affect velocity).  This law also states that the longer the lumen through which the fluids pass, the less laminar flow there is.  Therefore, two short peripheral IVs of sufficient diameter are more expedient in transfusions than one large long CVC catheter. 

Initial hemorrhagic shock resuscitation begins with administration of IV fluids, followed transfusion of blood products at a 1:1:1 ratio.  The initial IV fluids should be a 2L bolus of 0.9% normal saline or two 20mL/kg boluses by patient weight.  The patient is then determined to be either a responder, transient responder, or nonresponder to IV fluids based on their improvement.  Typically, patients in Class I or II can be treated initially with a trial bolus of crystalloids, but patients in Class III or IV should be getting blood products immediately with the first bolus of crystalloids.  The amount of blood transfused depends on a variety of factors, but is specifically centered around the concept of “permissive hypotension”.  Permissive hypotension is the idea that a patient in active hemorrhagic shock should be transfused just enough blood products to retain a systolic blood pressure above 70 mmHg.  Then, after hemorrhage is controlled, the patient can be transfused to retain a systolic blood pressure above 90 mmHg[1].  As a rule of thumb, one can expect roughly a loss of 1L blood with a femur fracture, and at least 1L blood loss with a pelvic fracture.  Other long bone fractures such as the humerus, tibia or fibula can also account for as much as 500cc each of blood loss.  As such, a patient with bilateral femur fractures or a pelvic fracture can already be assumed to be approaching stage III or IV of hemorrhagic shock.  As the saying goes in accounting for blood loss in hemorrhagic shock, “blood on the floor, plus four more”.  This phrase meaning basically that a life-threatening amount of blood can be lost as active hemorrhage outside the body, in the thigh compartments of bilateral femur fractures, the pelvis, abdomen, or chest.  It should also be noted that no number of transfusions should be used as a substitute for definitive control of an active bleed.

During the transfusion process in hemorrhagic shock, it is common for transfusion requirements to extend past the initial products given.  Most all hospitals incorporate a “massive transfusion protocol” into this process, with a “massive transfusion” being the replacement of one entire blood volume (or 10 U pRBCs) in 24 hours[2].  A rapid infuser can be used which warms the products as they are transfused, thus improving their ability to clot appropriately.  As stated previously, the patient’s clinical status and vital signs help to gauge the rate of transfusion, but frequent checks on the patient’s CBC, PT, PTT, INR, fibrinogen, and ionized Ca should be made roughly every 5-10 U pRBCs given.  This is to ensure not only appropriate improvement in measured hemoglobin, but that the patient has not developed a dilutional thrombocytopenia or coagulation factor deficiency during massive transfusion.  Ionized calcium (iCa) is monitored as it can be reduced rapidly, causing hypocalcemia in light of a massive transfusion.  Citrate circulating in the bloodstream acts to chelate iCa, thereby inactivating it.  A unit of pRBCs contains roughly 3mg of citrate in the CPDA-1 used for storage.  Typically, this is rapidly cleared by the liver within 5 minutes, but with massive transfusions it can become overwhelming, causing mass chelation of the body’s iCa[3].  10-20cc Ca gluconate or 2-5cc CaCl should be administered via IV for every 500cc blood products given.

Shock resuscitation remains clinically significant simply due to the lifethreatening nature of blood loss.  Due to the body's ability to bleed a significant amount into either the chest, abdomen, pelvis or thighs, the first signs of hemorrhagic shock may not always be so easily noticed.  In addition, many cases of shock resuscitation are not prompted by traumatic events, but by other forms of blood loss.  Whether it be due to a GI bleed, or hemorrhage due to coagulopathy, physicians must be mindful of changes in vital signs should they occur in order to recognize shock.  Furthermore, the patients general appearance may be helpful in determining the diagnosis.  If the patient appears diaphoretic and visibly uncomfortable along with having vital signs suggestive of early stages of hemorrhagic shock, clinical suspicion for shock should be high.

As previously stated, a common sign of impending shock can be the decrease in pulse pressure, an increased heart rate, or a slight increase in breathing.  Most important of all, the clinical evidence of decreased urine output can indicate impending shock as kidneys become slightly hypoperfused.  A decrease of urine output below 30cc/hr, or more exactly less than 0.5cc/kg/hr, suggests renal hypoperfusion and could be the first sign of stage I shock.  Of course, there are other reasons which could be causing renal hypoperfusion.  It is vital to keep in mind the patient's full history and physical exam, as these may suggests other etiologies besides blood loss.  For example, if a patient has been taking a new beta-blocker, they hay be having decreased blood pressure and renal hypoperfusion unrelated to blood loss.  Physical exam must be used to assess the chest, abdomen, pelvis and thighs to ensure there is no evidence of blood loss present.  These signs could be as apparent as decreased breath sounds due to blood in the pleural space, or increased abdominal distention or pain due to blood in the abdomen.  Patients with some level of coagulopathy may also have hematomas which may develop along the psoas, which may be difficult to diagnose on exam along.  Any new pain in lower extremity flexion/extention should be reason for concern.  A CT of the abdomen/pelvis with contrast can be helpful in diagnosing a psoas hematoma, or retroperitoneal bleed.

There are a variety of products which can be beneficial on shock resuscitation, but the three typical products used in the acute care setting are packed red blood cells (pRBCs), fresh frozen plasma (FFP), and platelets.  The U.S. military discovered issues with ARDS and MODS developing in patients with large volume resuscitation with strict crystalloids as early as 1996.  Then, it was studies of the early 2000’s such as the PROMTT study (2013) and PROPPR trial (2015)[4] which further refined our resuscitative use of blood products to its current form.  The PROMTT study was a prospective, multicenter observational cohort in which a varying ratio of blood products (1:1:1 vs. 1:1:2) were administered to shock patients to determine any changes in 6 hour survival rates.  it was found that 1:2 ratios or higher had a higher likelihood of dying in the first 6 hours, and that earlier transfusion of blood products and earlier use of FFP showed to have decreased 24 hour and 30 day mortality.  In a similar vein, the PROPPR trial was a randomized clinical trial where 1:1:1 and 1:1:2 ratios for transfusions were compared specifically for any difference in mortality at 24 hours and then again at 30 days.  While there was no significant difference in mortality rates, the 1:1:1 group did experience lower rates of death from exsanguination at 24 hours as well as less instances of ARDS, MODS, sepsis, infection, or VTE.  Today, the concept of “balanced fluid resuscitation” is the standard of care, with the usual intent of a 1:1:1 ratio of FFP: platelets: pRBCs to be given.  It was discovered that this ratio tended to result in greater 6 hour survival, fewer morbidities, and fewer deaths from exsanguination within the first 24 hours of injury.