Shock Categories

Why this matters

Shock means organs are not getting enough blood. It is not only a low blood pressure. A patient can be in shock with a “normal” cuff while a fast heart rate and tight vessels compensate. First, spot shock and name the main category. Then match the treatment. Do not give fluid to every patient in shock. Mixed shock is real, such as trauma plus sepsis, or pump failure plus dilated vessels after return of circulation. The four categories are a teaching tool. They are not a perfect label.

Clinical sequence

1. Call it shock when organs are not getting enough blood, not only when the cuff is low.
2. Ask which category fits: not enough volume, blood vessels too dilated (distributive shock), pump failure, or a blockage.
3. Match the treatment to that category. Check the lungs and the mental status after every move. Do not give fluid to every hypotensive patient.
4. Reassess after every move. Mixed shock is real.

Four categories

• Hypovolemic. Not enough volume, from bleeding, dehydration, or burns.
• Distributive. Blood vessels too dilated, as in sepsis, anaphylaxis, and neurogenic shock.
• Cardiogenic. Pump failure from a heart attack, weak heart muscle, or a rate or rhythm that kills output.
• Obstructive. A blockage of flow, such as tension pneumothorax, tamponade, or a massive pulmonary embolism.

Field Clues by Category

Hypovolemic

• Look for bleeding you can see or suspect inside, vomiting, diarrhea, poor intake, heat illness, or burns.
• Neck veins are usually flat. Skin is cool and pale. The heart rate is fast. Capillary refill is slow. Low blood pressure is late.
• Stop the bleeding and keep the trauma scene short. Give volume per protocol, crystalloid or blood. Uncontrolled bleeding without traumatic brain injury often uses limited crystalloid until the bleeding is controlled. That permissive-hypotension idea does not apply the same way to traumatic brain injury. Low blood pressure makes brain injury worse.

Distributive

• Sepsis: an infection source, fever or a low temperature, new confusion, and fast breathing. See the sepsis lesson.
• Anaphylaxis: an exposure, hives, wheeze, swelling, and low blood pressure. Give intramuscular epinephrine early, per protocol.
• Neurogenic shock: a high spinal injury, warm dry skin below the injury, and sometimes a slow heart rate. Fluids are careful. Other drugs follow your protocol.

Cardiogenic

• Chest pain, a history of ischemia, wet lungs, distended neck veins, cool clammy skin, and pulmonary edema.
• Fluids are cautious, often small or none. Treat a rate or rhythm that is causing the failure. Use CPAP and nitrates when you are authorized and the patient is not hypotensive. Use a PCI destination when it applies.

Obstructive

• Tension pneumothorax: trauma or positive-pressure ventilation, one-sided findings, and obstructive shock. Decompress if you are authorized.
• Tamponade: penetrating chest trauma is the classic story. Breath sounds can be equal, with distended neck veins and low blood pressure. Move. Do not stay for a long exam.
• Massive pulmonary embolism: sudden shortness of breath or fainting, plus risk factors. Support them and choose the destination. A clot-busting drug only if protocol or medical control allows it.

How to sort shock

• Recognize shock. Look for altered mental status, weak pulses, low blood pressure or compensated signs such as a fast heart rate, cool skin, and slow capillary refill, plus work of breathing, mottling, and a history of not making urine.
• Control life threats. Airway and oxygen. Massive bleeding. The tension pathway if your protocol says so.
• Name the category: volume, dilated vessels, pump, or obstruction.
• Match the intervention to the category and the protocol. Do not give fluid to every patient in shock. Do not start a vasopressor on every patient in shock. Do not run fluid wide open as the plan.
• Reassess. Every intervention needs vital signs and mental status before and after. Mixed shock exists.

Key points

• Compensated shock can have a “normal” blood pressure. Look at the whole patient, especially children and young adults.
• End-tidal CO2 may be low when perfusion is poor. It is an adjunct, not a diagnosis by itself.
• Say the category on the radio. For example: “Pump-failure shock. Cautious fluids per protocol. PCI pathway if it applies.”
• A trend tells you more than one reading. One better blood pressure after fluid does not mean the problem is solved.
• Keep them warm. Cold makes clotting worse in trauma and in shock.

Common errors

• Do not flood pump failure or obstructive shock with a large fluid bolus.
• Do not miss anaphylaxis because there is no rash.
• Do not call a patient stable because the systolic pressure is 100 while mental status is crashing.
• Do not focus on IV access while external bleeding is still uncontrolled.

Practice

Related: Sepsis recognition, Massive hemorrhage first, Tension pneumothorax.

Sources & Further Study

Named guidelines for further study. They are not clinical orders and do not replace your protocol or medical direction.

• NASEMSO National Model EMS Clinical Guidelines (2022) — U.S. EMS model language; your protocol still decides care
• ATLS shock classification (hypovolemic, distributive, cardiogenic, obstructive)
• AHA 2025 Part 9: Adult Advanced Life Support — Hs/Ts and shock physiology sit beside the arrest algorithms
• Follow your sepsis, anaphylaxis, trauma, and cardiogenic protocols.