SymptomHeart & circulation
Severe Hypotension (Dangerously Low Blood Pressure)
Severe hypotension is blood pressure low enough that organs such as the brain, heart and kidneys are not getting enough blood. It is usually defined as a systolic (top) reading below 90 mm Hg with symptoms, or a mean pressure under 65 mm Hg. Signs include fainting, confusion, cold clammy skin, fast weak pulse and little urine. It is a sign of shock, caused by sepsis, heavy bleeding, dehydration, anaphylaxis or heart failure, and needs emergency treatment.
Also called: Dangerously low blood pressure, profound hypotension, hypotensive crisis, circulatory shock
At a glance
- What it is
- Blood pressure too low to supply vital organs, usually systolic below 90 mm Hg with symptoms.
- Main causes
- Sepsis, blood loss, severe dehydration, anaphylaxis, heart attack or heart failure, adrenal crisis.
- Warning signs
- Fainting, confusion, cold clammy skin, fast weak pulse, fast breathing, little or no urine.
- How serious
- Life-threatening. Organ damage can start within hours.
- Treatment
- Emergency fluids, medicines to raise pressure, and treatment of the cause.
When to get help
Call 911 or go to the ER
- Low blood pressure with confusion, fainting, cold clammy or mottled skin, or a fast weak pulse: call 911 or your local emergency number
- Swelling of the lips or tongue, hives, wheezing or collapse after a sting, food or medicine: use an epinephrine auto-injector if available and call 911
- Signs of internal bleeding: vomiting blood, black or bloody stools, or a fall in blood pressure after an injury
- Low blood pressure with chest pain, severe breathlessness or a fever and feeling very unwell
- A person on long-term steroids or with Addison's disease who is vomiting and collapsing
See a doctor within a day or two
- Repeated dizziness or near-fainting with readings below 90/60 mm Hg
- Vomiting or diarrhea with inability to keep fluids down and very little urine
Book a routine appointment
- Low readings without symptoms, or light-headedness only on standing up
What counts as dangerously low blood pressure
There is no single number that is dangerous for everyone. Many healthy people, especially young women and athletes, run at 90/60 mm Hg and feel fine. Blood pressure becomes dangerous when it is too low to perfuse organs, which shows up as symptoms.
Doctors use these markers:
- Systolic pressure below 90 mm Hg, or a fall of more than 40 mm Hg from your usual level.
- Mean arterial pressure (MAP) below 65 mm Hg. MAP is roughly diastolic plus one third of the difference between systolic and diastolic.
- Signs of poor perfusion: confusion, cold extremities, slow capillary refill, low urine output and high lactate in the blood.
Symptoms of severe hypotension
- dizziness, light-headedness or fainting
- confusion, agitation or drowsiness
- cold, pale, clammy or mottled skin (warm, flushed skin early in sepsis)
- a fast, weak or thready pulse
- fast, shallow breathing
- little or no urine
- nausea, extreme thirst
- chest pain if the heart muscle is short of blood
Causes: the types of shock
| Type | Mechanism | Examples |
|---|---|---|
| Hypovolemic shock | Too little blood or fluid | Bleeding, severe vomiting or diarrhea, burns |
| Septic shock | Blood vessels dilate and leak in severe infection | Pneumonia, urinary or abdominal infections |
| Anaphylaxis | Allergic release of chemicals widens vessels | Insect stings, foods, medicines |
| Cardiogenic shock | The heart cannot pump enough | Heart attack, severe heart failure, arrhythmia |
| Obstructive shock | Blood flow is blocked | Pulmonary embolism, tension pneumothorax, cardiac tamponade |
| Other distributive causes | Loss of vessel tone | Spinal cord injury, adrenal crisis, drug overdose |
Medicines can also cause severe hypotension, particularly in overdose or combination: blood pressure tablets, nitrates with erectile dysfunction drugs, opioids, sedatives and some antidepressants.
What to do while waiting for help
- Call 911 or your local emergency number.
- Lay the person flat. Raise their legs about 12 inches (30 cm) if there is no head, neck, back or leg injury, unless this makes breathing harder.
- If anaphylaxis is suspected, use their epinephrine auto-injector into the outer thigh. A second dose can be given after 5 to 15 minutes if there is no improvement.
- Press firmly on any external bleeding.
- Keep them warm and do not give food or drink.
- If they become unresponsive and are not breathing normally, start CPR.
How doctors treat severe hypotension
- Assessment: blood pressure, heart rate, oxygen levels, ECG, blood tests (lactate, blood count, kidney function, cultures), ultrasound of the heart and abdomen, and a search for the cause.
- Intravenous fluids: given quickly for most types except cardiogenic shock, where fluid can worsen lung congestion.
- Blood transfusion and urgent control of bleeding for hemorrhage.
- Vasopressors: medicines such as norepinephrine to tighten blood vessels, given in intensive care. The usual target is a mean arterial pressure of at least 65 mm Hg.
- Treating the cause: antibiotics within the first hour for septic shock, epinephrine for anaphylaxis, opening a blocked coronary artery after a heart attack, steroids for adrenal crisis, clot treatment for a pulmonary embolism.
Complications
Prolonged severe hypotension damages organs: acute kidney injury, heart attack, stroke, liver injury, gut ischemia and multi-organ failure. The faster pressure is restored, the better the outcome.
Severe vs everyday low blood pressure
Low blood pressure without symptoms needs no treatment. Brief light-headedness when standing up quickly is often orthostatic hypotension, which is common in older adults, with dehydration and on blood pressure medicines. It is usually managed by rising slowly, drinking enough fluid and reviewing medicines. See hypotension for these milder forms.
Frequently asked questions
What blood pressure is too low?
A reading below 90/60 mm Hg is considered low, but it is only dangerous when it causes symptoms such as fainting, confusion, cold clammy skin or reduced urine. A systolic pressure below 90 mm Hg with these signs, or a mean pressure below 65 mm Hg, needs emergency care.
What are the signs of shock from low blood pressure?
Signs include confusion, drowsiness, cold and clammy or mottled skin, a fast weak pulse, fast breathing, very little urine and fainting. In early septic shock, skin may be warm and flushed. Any of these with low blood pressure is an emergency.
What is the most common cause of severe hypotension?
In hospitals, sepsis is one of the most common causes. In the community, bleeding, severe dehydration from vomiting and diarrhea, anaphylaxis and heart problems are common causes. Medicine side effects and overdoses are also frequent contributors.
Can dehydration cause dangerously low blood pressure?
Yes. Severe fluid loss from vomiting, diarrhea, heat or not drinking reduces blood volume and can cause hypovolemic shock, especially in babies, older adults and people on diuretics. Signs include extreme thirst, little urine, dizziness and confusion.
How is severe hypotension treated in hospital?
Treatment starts with intravenous fluids and, if needed, blood transfusion. If pressure stays low, vasopressor medicines are given in intensive care. At the same time, doctors treat the cause, such as antibiotics for sepsis or epinephrine for anaphylaxis.
Sources
This guide was written from current patient and clinical guidance, including:
- Surviving Sepsis Campaign: International guidelines for management of sepsis and septic shock
- American Heart Association: Low blood pressure, when blood pressure is too low
- MedlinePlus: Shock
- NHS: Low blood pressure (hypotension)
- American College of Surgeons: ATLS hemorrhagic shock classification