Hypovolemic Shock Overview
Hypovolemic shock occurs as a result of a reduction in intravascular fluid volume. This reduction of the intravascular fluid volume causes a decrease in stroke volume because of the resulting decrease in preload.
The decrease in preload impairs cardiac output which ultimately leads to inadequate delivery of oxygen and nutrients to the tissues and organs (shock).
The loss of intravascular fluid volume which causes hypovolemic shock can have a number of causes including dehydration from vomiting and diarrhea, hemorrhage, decreased intake of fluids, pathologic urinary losses (e.g. diabetic ketoacidosis, diabetes insipidus), and translocation of body fluids (e.g. burns, peritonitis, small bowel obstruction).
Hypovolemic shock is the most common form of shock that occurs in children. The most common cause of hypovolemic shock and infant deaths worldwide in the pediatric population is dehydration resulting from diarrhea.
Remember: Heart Rate x Stroke Volume (preload, afterload, contractility) = Cardiac Output.
When preload is decreased, there are three compensatory mechanisms that can be possibly altered. The three compensatory mechanisms are increased HR, increased afterload, and/or increased contractility. These three compensatory mechanisms can be altered in an attempt to maintain cardiac output and may be used to help identify the presence of shock.
Signs and Symptoms of Pediatric Hypovolemic Shock
The Primary Assessment (ABCDE) of the Pediatric Systematic Approach Algorithm can be used to identify symptoms consistent with hypovolemic shock. The Primary Assessment acronym stands for Airway, Breathing, Circulation, Disability, and Exposure.
- A: Typically the airway of the child with hypovolemic shock will not be significantly affected.
- B: The patient may experience some Breathing changes and this may be recognized by a nonlabored tachypenea.
- C: The most notable changes will likely be seen with circulation. These circulation changes include tachycardia, narrowing pulse pressure, possible systolic hypotension, capillary refill time > 2 seconds, cool/pale skin, weak to absent peripheral pulses, reduced urine output.
- D: Disability or neurological changes include decreased level of consciousness.
- E: Exposing the patient to observe the child’s skin and extremities will often reveal cool, pale, and mottled extremities.
The table below outlines the major clinical signs and symptoms associated with fluid volume deficit.
There is a period of time when the above symptoms will be present, but compensatory mechanisms are able to maintain systolic blood pressure. This window of time is classified as compensated shock. Early recognition and treatment of hypovolemic shock during this window of time provides the best chance for survival and recovery.
If compensatory mechanisms fail and hypotensive shock (low systolic BP) develops, the chances of survival and recovery are significantly decreased.
Treatment of Pediatric Hypovolemic Shock
The main treatment for the critically-ill child with hypovolemic shock is fluid resuscitation. Fluid resuscitation consists of rapid boluses of isotonic crystalloid IV fluids (NS-normal saline or LR-lactated Ringer’s). This treatment is primarily focused on correcting the intravascular fluid volume loss.
The normal minimum dosing is at least three fluid boluses of 20 ml/kg each. As each 20 ml/kg fluid bolus is given, the Evaluate → Identify→ Intervene Sequence of the Systematic Approach Algorithm is carried out.
The child’s response to each fluid bolus should dictate the course of further treatment. Each bolus should be given over 5-10 minutes and reevaluation should take place.
When reevaluation takes place, typical signs that would indicate improvement are decrease in heart rate, improved urine output, decreased respiratory rate, and improved level of consciousness.
If the hypovolemic shock is a result of blood loss, this is classified as hemorrhagic hypovolemic shock. For hemorrhagic hypovolemic shock, boluses of isotonic crystalloid IV fluids are indicated, but the shock may not improve significantly.
In this case, packed red blood cells (PRBCs) are indicated, and the standard dosing of PRBCs for refractory hemorrhagic hypovolemic shock is 10 mL/kg.