Hypovolemic shock is the most common type of shock seen in infants and children. It means there is not enough fluid or blood inside the blood vessels for the heart to pump well. This lowers blood flow to organs and can cause harm fast if not treated. In PALS, knowing the likely causes helps teams act quickly to restore volume and protect the child.
Main causes of hypovolemic shock in PALS
1. Gastrointestinal losses: vomiting and diarrhea
Children lose a lot of fluid and salts with severe vomiting and diarrhea. Small children have less fluid reserve, so they can become hypovolemic quickly. In many parts of the world, dehydration from gut infections remains a leading cause of hypovolemic shock. Replacement of fluids by the right route is the main treatment.
2. Hemorrhage and trauma
Bleeding from an injury, surgery, or internal bleeding can cause rapid volume loss. Even when blood loss is not visible, bleeding inside the belly, chest, or skull can be large enough to cause shock. In trauma cases, controlling bleeding and restoring blood volume is a priority.
3. Burns and large skin loss
Severe burns cause fluid to leak from blood vessels into the tissues. This fluid shift reduces the circulating blood volume. Burn patients need careful fluid resuscitation because both too little and too much fluid can cause harm.
4. Third spacing
Some illnesses let fluid move out of the blood vessels and collect in body spaces. Examples include severe infections in the belly, pancreatitis, or bowel obstruction. The fluid is still in the body but not in the blood vessels, so circulation falls.
5. Osmotic diuresis and diabetes-related fluid loss
When blood sugar is very high, the body spills sugar into the urine and pulls water with it. Conditions like diabetic ketoacidosis cause large losses of fluid and salts. This can lead to low blood volume if not treated.
6. Excessive sweating, fever, or heat illness
In hot settings or with high fevers, children can lose water and salts through sweat. If fluid is not replaced, intravascular volume falls. This is more likely in very young children and infants.
7. Renal losses and vomiting from illness
Some kidney problems or medicines increase urine output. Ongoing vomiting from severe infections or poisoning also removes fluids and salts. When losses add up faster than replacement, hypovolemia follows.
Why children are more vulnerable
Children have a higher fluid turnover and smaller blood volume than adults. A smaller absolute fluid loss gives a larger relative drop in their blood volume. Also, infants cannot signal thirst clearly and may become dehydrated faster when ill. This is why common illnesses like gastroenteritis can turn serious in children.
How hypovolemic shock looks in PALS assessment (signs to watch for)
Use simple checks. Children may show:
- Fast heart rate and fast breathing
- Pale, cool, or clammy skin
- Delayed capillary refill or weak pulses
- Low urine output
- Less alert or sleepy behavior
If the child is losing blood, look for visible bleeding, swelling of the belly, or signs of fracture. For dehydration, check for sunken eyes, dry mouth, and poor skin turgor. These signs help the team decide whether to give fluids and how fast to act.
PALS-focused causes to remember in a resuscitation setting
When running PALS, suspect hypovolemic shock in these situations:
- Recent trauma or signs of bleeding
- Severe vomiting and diarrhea before the event
- History of diabetes with signs of high blood sugar
- Large burns or recent surgery
- Prolonged fever or heat exposure
Identifying the likely cause guides whether to give IV fluids, blood, or other specific therapy.
Immediate steps in PALS when hypovolemia is suspected
- Keep the airway open and give oxygen as needed.
- Check breathing and circulation. Support breathing if required.
- Establish IV or intraosseous access fast to deliver fluids.
- Give isotonic fluid boluses based on weight and response. Monitor for improvement.
- If bleeding is present, control the source and consider blood transfusion early.
- Reassess often. Watch mental status, heart rate, blood pressure, and urine output.
Preventing hypovolemic shock at the community level
- Encourage prompt treatment for diarrhea and vomiting, including oral rehydration for mild cases.
- Teach caretakers to seek care early for signs like very fast breathing, low urine output, or lethargy.
- For chronic conditions like diabetes, ensure good follow up and quick care when sickness begins.
- In hot weather, give extra fluids and avoid prolonged sun exposure for young children.
