Peripheral Vasoconstriction

How peripheral vasoconstriction works

The walls of small arteries contain smooth muscle controlled mainly by the sympathetic nervous system, the "fight or flight" system. When noradrenaline (norepinephrine) acts on alpha receptors in the vessel wall, the muscle contracts and the vessel narrows. Skin and limb vessels respond strongly, so blood is diverted to the brain, heart and other organs.

This helps in two situations:

• Cold: narrowing skin vessels reduces heat loss and keeps the core temperature stable.
• Low blood volume or blood pressure: after bleeding, severe dehydration or heart failure, vasoconstriction maintains blood pressure to vital organs.

Problems arise when the response is too strong, lasts too long, or signals a serious underlying illness.

Signs of peripheral vasoconstriction

• Cold hands, feet, nose and ears
• Pale, white, bluish or mottled (blotchy purple) skin
• Numbness, tingling or clumsiness in the fingers
• Slow capillary refill: after pressing a fingernail for 5 seconds, color takes more than about 2 to 3 seconds to return
• Weak pulses at the wrist or foot
• Pain and throbbing as blood flow returns

Normal causes

• Cold exposure
• Emotional stress, fear and pain
• Smoking or vaping nicotine: each cigarette causes temporary narrowing
• Caffeine in large amounts
• Fever onset: chills and cold hands occur as the body raises its temperature set point

Abnormal or serious causes

Raynaud's phenomenon

An exaggerated vasospasm of the fingers and toes triggered by cold or stress. The digits turn white (no blood), then blue (low oxygen), then red as blood returns, with numbness and throbbing. Primary Raynaud's is common in young women and usually harmless. Secondary Raynaud's is linked to systemic sclerosis, lupus and other connective tissue diseases, and can cause ulcers. See Raynaud's phenomenon.

Shock

In shock from bleeding, dehydration, heart failure or some infections, intense peripheral vasoconstriction keeps blood pressure up. Cold, clammy, mottled skin with a fast pulse and confusion is a warning sign of circulatory failure. (In early septic shock, skin can be warm and flushed instead.)

Medicines and drugs

• Beta-blockers (cold hands and feet are a common side effect)
• Migraine medicines: triptans and ergotamines
• Decongestants such as pseudoephedrine
• ADHD stimulants and amphetamines
• Some chemotherapy drugs
• Vasopressors used in intensive care to raise blood pressure
• Cocaine, which can cause severe vasospasm, heart attacks and tissue damage

Cold injuries

Prolonged vasoconstriction in severe cold leads to frostbite, chilblains and, if body temperature falls, hypothermia.

Blood vessel diseases

Buerger's disease (in heavy smokers), atherosclerosis and blood clots reduce flow by blocking vessels rather than by vasoconstriction, but they cause similar cold, pale extremities and can worsen with vasospasm.

Vasoconstriction vs blocked arteries

How doctors assess it

A doctor will ask about triggers, color changes, medicines, smoking, drug use and symptoms of connective tissue disease, then examine pulses, skin, capillary refill and fingertips. Tests may include:

• Nailfold capillaroscopy: magnified view of the small vessels at the nail base, which are abnormal in secondary Raynaud's
• Blood tests: antinuclear antibodies (ANA), blood count, inflammation markers, thyroid function
• Ankle-brachial index or Doppler ultrasound to rule out artery disease
• In suspected shock: blood pressure, lactate, oxygen levels and urgent treatment of the cause

Management

• Keep warm: dress in layers, wear gloves and warm socks, use hand warmers, and warm the whole body, not just the hands.
• Stop smoking and avoid nicotine products.
• Avoid triggering medicines where possible; ask your doctor about alternatives to beta-blockers or decongestants.
• Manage stress with relaxation techniques.
• During a Raynaud's attack: move somewhere warm, run hands under warm (not hot) water, and wiggle the fingers or swing the arms.
• Medicines such as calcium channel blockers (for example nifedipine) relax vessel walls in troublesome Raynaud's. Other vasodilators are used for severe cases or ulcers.
• Shock is treated in hospital with fluids, blood, oxygen and treatment of the cause.

Frequently asked questions

What is peripheral vasoconstriction?

It is the narrowing of small blood vessels in the skin, hands and feet, controlled by the nervous system. It reduces blood flow to the extremities to conserve heat or to keep blood pressure up for vital organs. It makes fingers and toes cold and pale.

What causes peripheral vasoconstriction?

Normal causes are cold, stress, pain and nicotine. Abnormal causes include Raynaud's phenomenon, shock from blood loss or heart failure, and medicines such as beta-blockers, triptans, decongestants and stimulants. Cocaine causes severe, dangerous vasoconstriction.

Is peripheral vasoconstriction dangerous?

Usually not. It is a normal protective response to cold. It becomes dangerous when it is prolonged or severe enough to starve tissue of oxygen, as in severe Raynaud's, frostbite or cocaine use, or when it is a sign of shock, which is a medical emergency.

Why are my hands and feet always cold?

Common reasons are a naturally strong vasoconstriction response, low body fat, smoking, and medicines such as beta-blockers. Raynaud's phenomenon, an underactive thyroid, anemia and poor circulation are other causes. See a doctor if color changes, numbness or sores occur.