Posttraumatic Hemorrhagic shock

1

What is hemorrhagic shock?

Shock exists when the cardiovascular system is no longer able to meet the body’s metabolic and oxygen needs, resulting in cellular injury. In other words, the tissues are not adequately perfused to meet their oxygen and nutrient requirements. Hemorrhagic is a subtype of shock directly related to blood loss, which decreases oxygen delivery as a result of loss of circulating volume and oxygen-carrying red blood cells. The majority of deaths from bleeding occur within 2 hours of injury.

2

What is the initial management of hemorrhagic or hypovolemic shock?

Depletion of the blood volume results in a decreased driving pressure returning blood to the heart, a decreased end-diastolic ventricular volume, and a decreased stroke volume, resulting in a decreased cardiac output (CO). Therefore, the priorities are to (1) control blood loss and (2) restore circulating blood volume. ATLS guidelines reinforce circulation (C in ABC) in the initial management of an injured patient. Circulation management requires vascular access, either through an IV catheter or intraosseous device. Hemorrhage control includes direct pressure, extremity tourniquets, pelvic binding, resuscitative endovascular aortic occlusion (REBOA), or aortic clamping via thoracotomy.

3

Describe the cellular manifestations of hemorrhagic shock

Inadequate tissue perfusion results in decreased cellular oxygen tension and disruption of normal oxidative phosphorylation with a decrease in the generation of adenosine triphosphate (ATP). The Na+ K+ ATPase slows, and the cell can no longer maintain membrane polarization integrity, impairing a number of important cellular processes. Anaerobic metabolism ensues, resulting in the production of lactic acid, creating a “gap” metabolic acidosis. The first evidence of this dysfunction is swelling of the endoplasmic reticulum, followed by mitochondrial damage, lysozyme rupture, and entry of interstitial water into the cell as intracellular sodium (Na+) accumulates. This loss of extracellular water exacerbates the intravascular volume deficit.

4

What are the clinical manifestations of hemorrhagic shock?

• Heart rate (HR) >110 beats per minute, but can be paradoxically low in profound shock, patients taking cardiac medication may not manifest changes in HR.

• Blood pressure (BP) <90 mm Hg is generally considered shock in adults, but requires age adjustment for pediatric and geriatric populations.

• Altered mental status with lethargy and confusion.

• Decrease in urine output <0.5 mL/kg per hour and low central venous pressure (CVP).

• The skin becomes cool, clammy, and pale. The subcutaneous veins collapse (making it hard to start an IV line). Capillary refill is delayed 2–3 seconds.

5

What is the formula for estimating total blood volume in adult and pediatric patients?

In adults and children, the average blood volume represents 7% and 9% of ideal body weight, respectively. Therefore, in adults, multiply the ideal weight in kg × 7% (70 mL/kg). In children, multiply ideal weight in kg × 9% (90 mL/kg).

6

What are the potential sources of occult blood loss when trying to ascertain a patient’s hemodynamic status?

The pleural spaces, abdominal cavity, retroperitoneal or pelvic space (pelvic fractures), major long bone fractures, and at the scene externally (“on the sidewalk”). Femur fractures can hide >1 L of blood, whereas each rib fracture can account for 150 mL.