Shock occurs when the oxygen and nutrient supply is insufficient to meet the metabolic demands of the body. Shock can be classified as hypovolemic, septic, distributive, and cardiogenic. Hypovolemic shock is the most common type of shock in children. It is usually the result of fluid-losing states such as diarrhea, blood loss, or burns. The effect is decreased intravascular volume, decreased preload, and decreased stroke volume. When hypovolemic shock occurs as a result of fluid and electrolyte losses, both intravascular and interstitial fluid volume is decreased. Physical signs are classic for dehydration, including sunken eyes, depressed fontanelle, dry mucous membranes, cool extremities, decreased peripheral pulses, and poor skin turgor. In contrast, patients with hypovolemic shock because of increased capillary permeability have intravascular hypovolemia with interstitial euvolemia. Such is the case with burns and nephrotic syndrome. Physical signs include mental status changes, increased capillary refill, decreased peripheral pulses, and decreased urine output without the classic signs of dehydration. Extremities may be edematous. Treatment of hypovolemic shock consists of replacement of fluids. When shock is secondary to blood loss, fluid replacement should include blood products.

Septic shock occurs as a consequence of bacterial, fungal, or viral infection. It is defined as hypotension despite adequate fluid resuscitation and inadequate perfusion. Signs of inadequate perfusion may include lactic acidosis, oliguria, or altered mental status. In children, septic shock can present as classic “warm shock,” with high cardiac output and low systemic vascular resistance, or as “cold shock” with decreased cardiac output and elevated systemic vascular resistance. Septic shock should be treated with IV fluids and broad-spectrum antibiotics. Following resuscitation with at least 60 mL/kg of isotonic fluid, vasopressors may be required to maintain blood pressure. In addition, cortisol replacement may be indicated if adrenal insufficiency occurs.

Distributive shock, also known as vasodilatory shock, occurs because of abnormal regulation of blood flow, resulting in functional hypovolemia.
One example of distributive shock is anaphylactic shock, a hypersensitivity reaction that occurs immediately after exposure to an allergen. The result is an immunoglobulin (Ig)E-mediated massive release of cytokines by mast cells and basophils. Angioedema, hypotension, and third-spacing ensue and can be life-threatening. Immediate treatment with subcutaneous epinephrine, as well as fluid resuscitation, is imperative. In addition, airway management and treatment with antihistamines and steroids are required.