Shock is inadequate tissue perfusion, manifested clinically based upon hemodynamic disturbances and organ dysfunction. Hemodynamic presentation of shock can include altered mental status, tachycardia, hypotension, cool extremities, prolonged capillary refill (> 2 seconds), weak peripheral pulses, and narrowing of the pulse pressure (<25 mmHg). Initial management of the patient in shock is focused on restoring intravascular volume, maintaining adequate oxygen delivery, limiting ongoing blood loss, and preserving organ function.
Shock at the cellular level results from poor oxygenation and hypoxia. Loss of circulating blood volume from hemorrhage is the most common cause of shock in the trauma patient (Britt et al., 1996). Other causes or contributing factors to the development of shock include mechanical obstruction (from cardiac tamponade, tension pneumothorax), inadequate oxygenation, neurologic dysfunction (high spinal cord injury), and cardiac dysfunction (Britt et al., 1996). Shock is second only to brain injuries as cause of death in the trauma population, and the most common cause of shock in the trauma patient is hemorrhagic. Fortunately, shock is typically responsive to treatment (Britt et al., 1996). Approximately 30% of the circulating blood volume is lost before a change in blood pressure is noted (American College of Surgeons Committee on Trauma, 2012). A temporary response to one or more fluid boluses indicates the patient has ongoing hemorrhage and is in a persistent state of shock. Initial treatment of shock entails 2 L normal saline (NS). Care should be taken as large amounts of NS may result in metabolic acidosis. The goal is a mean arterial pressure (MAP) between 65 and 90 mmhg (MAP = diastolic blood pressure × 2 added to diastolic blood pressure ÷ 3) (Alam & Rhee, 2007). However, in blunt trauma or traumatic brain injury, a MAP above 105 mmhg is acceptable (Alam & Rhee, 2007). Use of colloids can increase intravascular volume and maintain plasma oncotic pressure. Unfortunately, a systematic review of clinical trials comparing resuscitation fluids found colloids did not improve mortality or morbidity among trauma patients compared to NS (Perel, Roberts, & Ker, 2012). Central venous pressure (CVP) measurements can assist in differentiating cause of shock (Perel, Roberts, & Ker, 2012). See Table 17-4.