Distributive Shock

What to do right now

If you suspect shock:

1. Call 911 or your local emergency number.
2. Anaphylaxis: give an epinephrine auto-injector into the outer thigh. A second dose can be given after 5 to 15 minutes if there is no improvement.
3. Lay the person flat and raise their legs about 12 inches (30 cm), unless this causes pain, they have a head, neck or back injury, or they are struggling to breathe (then let them sit up).
4. Do not move someone with a possible spinal injury.
5. Keep them warm with a blanket, and give nothing to eat or drink.
6. If they become unresponsive and are not breathing normally, start CPR.

How distributive shock works

Blood pressure depends on three things: how hard the heart pumps, how much blood is in the circulation, and how tight the blood vessels are. Shock types are named after which of these fails:

In distributive shock, inflammatory chemicals, toxins, allergic mediators or loss of nerve signals relax the muscle in the blood vessel walls. The circulation suddenly has far more space than blood to fill it, so pressure falls. Leaky capillaries let fluid escape into tissues, causing swelling and further loss of circulating volume. The heart initially pumps faster to compensate, which is why the skin may feel warm and the pulse bounding at first. Later the heart can tire and the picture becomes "cold" shock.

Hypovolemic shock and cardiogenic shock have their own pages.

Types of distributive shock

Septic shock

The most common type by far. A severe infection triggers an overwhelming immune response. Septic shock is defined as sepsis with low blood pressure that needs vasopressor drugs and a raised lactate despite adequate fluids. Lung, urine, abdominal and skin infections are the usual sources.

Anaphylactic shock

A severe allergic reaction to foods, insect stings, medicines or latex releases histamine and other mediators within minutes. Look for hives, flushing, swelling of the lips and tongue, wheezing, vomiting and collapse. Anaphylaxis is treated first with intramuscular epinephrine.

Neurogenic shock

Injury to the spinal cord in the neck or upper back cuts the sympathetic nerves that keep blood vessels tight and the heart rate up. The result is low blood pressure with a slow heart rate and warm, dry skin below the injury. It follows spinal cord injury and must be distinguished from bleeding, which often coexists after trauma.

Endocrine shock

Adrenal crisis occurs when the body lacks cortisol, for example in Addison's disease or after suddenly stopping long-term steroids. It causes low blood pressure that responds poorly to fluids and pressors until hydrocortisone is given. Severe hypothyroidism (myxedema coma) is a rarer cause.

Other causes

• toxic shock syndrome from staph or strep toxins
• drug and toxin reactions, including some anesthetics and overdoses
• liver failure and severe pancreatitis
• vasoplegia after heart surgery with a bypass machine

Signs and symptoms

• low blood pressure, usually a systolic below 90 mm Hg or a mean arterial pressure below 65 mm Hg
• a fast pulse (slow in neurogenic shock)
• warm, flushed skin early, later cold, mottled or bluish skin
• fast breathing and breathlessness
• confusion, agitation or drowsiness
• very little urine
• fever or a low body temperature below 36 °C (96.8 °F) in septic shock
• hives, swelling and wheeze in anaphylaxis

How it is diagnosed

In the ER or ICU, doctors assess blood pressure, heart rate, breathing, oxygen levels, mental state and urine output. Tests include:

• Lactate: a level above 2 mmol/L signals poor tissue oxygen delivery.
• Blood cultures and other cultures before antibiotics, plus blood count, kidney and liver tests.
• Cortisol if adrenal crisis is possible, and tryptase after suspected anaphylaxis.
• Bedside ultrasound of the heart and major veins to show whether the heart is pumping vigorously and how full the circulation is, helping rule out other shock types.
• Imaging to find a source of infection, or of the spine after injury.

Treatment

• Fluids: intravenous fluids restore volume. In septic shock, about 30 ml/kg of fluid is often given in the first 3 hours, then adjusted.
• Vasopressors: norepinephrine is the first-choice drug to tighten blood vessels, aiming for a mean arterial pressure of about 65 mm Hg. Vasopressin and epinephrine are added if needed.
• Septic shock: broad-spectrum antibiotics within 1 hour, and draining or removing the source of infection, such as an abscess or infected device. Hydrocortisone is added if pressor needs remain high.
• Anaphylactic shock: intramuscular epinephrine, repeated as needed, plus fluids and an epinephrine infusion for refractory cases. Antihistamines and steroids are secondary.
• Neurogenic shock: fluids, vasopressors with heart-rate support, atropine for slow heart rhythms, and spinal immobilization.
• Adrenal crisis: intravenous hydrocortisone and fluids.
• Organ support: oxygen, a breathing machine and kidney dialysis when organs fail.

Complications and outlook

Prolonged shock injures the kidneys, liver, lungs, brain and gut, and can lead to multi-organ failure. Outcome depends on the cause and how quickly treatment starts. Anaphylactic shock treated promptly usually resolves fully within hours. Septic shock remains dangerous, with death rates of roughly 1 in 3 or higher, and survivors may face weakness, fatigue and memory problems for months.

Frequently asked questions

What are the four types of distributive shock?

The main types are septic shock (from severe infection), anaphylactic shock (from a severe allergic reaction), neurogenic shock (from spinal cord injury) and endocrine shock, mainly adrenal crisis. Toxic shock syndrome, drug reactions and liver failure are less common causes.

Why is distributive shock called warm shock?

Early on, widened blood vessels near the skin and a hard-working heart keep the skin warm, flushed and dry, unlike the cold, clammy skin of bleeding or heart-related shock. As shock progresses and the heart tires, the skin can become cold and mottled.

What is the first-line treatment for distributive shock?

Intravenous fluids and norepinephrine are first-line for most types, along with treating the cause: antibiotics within an hour for septic shock, intramuscular epinephrine for anaphylaxis, and hydrocortisone for adrenal crisis. Treatment happens in an emergency department or intensive care unit.

How is neurogenic shock different from other distributive shock?

Neurogenic shock follows a spinal cord injury and causes low blood pressure with a slow heart rate, because the nerves that speed the heart are cut off. Other forms of distributive shock usually cause a fast heart rate. Bleeding must always be ruled out after trauma.

Can you survive distributive shock?

Yes, many people do, especially with fast treatment. Anaphylactic shock treated quickly with epinephrine usually resolves completely. Septic shock carries a higher risk of death, and outcomes improve the sooner antibiotics, fluids and vasopressors are started.