Hypotension is a medical term for low blood pressure especially in systemic circulation [arterial circulation that supplies different organs of the body.
Because the blood pressure is lowered, heart, brain, and other parts of the body do not get enough blood.
The normal blood pressures are in the range of 90/60 mmHg and 120/80 mmHg. Upper value is for systolic blood pressure whereas the lower one [denominator] is diastolic blood pressure.
[Read about how to measure blood pressure]
Hypotension is defined as a systolic blood pressure of less than 90 mm Hg or diastolic of less than 60 mm Hg.
Blood pressure is continuously regulated by autonomic nervous system. The sympathetic nervous system raises the blood pressure and the parasympathetic nervous system lowers it.
Hypotension is the opposite of hypertension which means high blood pressure.
Severe hypotension decreases the brain and other vital organs of oxygen and nutrients and leads to shock, which can be life-threatening.
A number of healthy subjects have a systolic BP of 80-100 mm which is compatible with long life expectancy. Only some patients complain of weakness, lethargy, easy fatiguability, dizziness and fainting on assuming an erect posture or standing inactive for long periods.
This occurs due to interference with neural pathways between the vasomotor center and efferent sympathetic nerve endings in blood vessels and heart so that the normal rise in cardiac output and vasoconstriction on assuming erect posture is abolished.
Causes of Hypotension
- Hypovolemia or decrease in blood volume
- Sudden loss of blood as in hemorrhage
- Insufficient fluid intake
- Excessive fluid loss as in diarrhea, vomiting
- Severe infection
- Severe allergic reaction (anaphylaxis).
- Drugs and substances
- Alcohol
- Anti-anxiety drugs
- Anti antidepressants
- Diuretics
- Antihypertensives
- Heat stroke
- Cardiac Causes
- Low output cardiac failure
- Left ventricular dysfunction
- Cardiac tamponade
- Constrictive pericarditis
- Tight mitral stenosis
- Left atrial myxoma
- Arrhythmia
- Cardiogenic shock
- Endocrine Causes
- Addison’s disease
- Myxedema
- Hypopituitarism
- Serotonin secreting tumors
- Neurogenic Causes
- Diabetic neuropathy
- Extensive lumbosacral sympathectomy
- Peripheral neuropathy
- Tabes dorsalis
- Syringomyelia
- Multiple sclerosis
- Excessive vasodilation
- Autonomic dysfunction
- Sepsis
- Acidosis
- Drugs
- Nitrates
- Calcium channel blockers
- Orthostatic hypotension
- A decrease in blood pressure due to a sudden change in body position.
- For example, stand from lying down position
- Mostly affects elderly
- Neurally mediated hypotension
- Affects young adults and children
- After prolonged standing
- Vasovagal syncope
- Drop in blood pressure while in the upright position.
- Increased activity of the vagus nerve [parasympathetic nervous system]
- Postprandial hypotension
- Decrease in blood pressure half to one hour after a meal
- Due to the diversion of blood to the intestine
- Autonomic dysregulation
Clinical Presentation
Lightheadedness or dizziness are the main symptoms. If the blood pressure is quite low the person may faint. Other symptoms could be
- Blurry vision
- Confusion
- Nausea or vomiting
- Sleepiness
- Weakness
- Cold, clammy, pale skin
- Palpitations
- Rapid, shallow breathing
Acute hypotension could be an emergency and should be attended accordingly.
In addition to the above symptoms, the patient may have symptoms pertaining to the causative disease.
A blood pressure measurement would reveal low values of blood pressure. An adult with a reading of 90/60 mmHg or lower in the presence of symptoms is said to have hypotension.
Chronic idiopathic orthostatic hypotension occurs due to primary autonomic insufficiency due to degeneration of central or peripheral autonomic nervous system. It is common in the elderly who may develop syncope, hypotension, convulsions but no tachycardia on standing. They may have associated anhydrosis, loss of hair, diminished lacrymal and salivary secretions, bladder atony, and impotence.
Shy-Dragger Syndrome is chronic orthostatic hypotension with degeneration of CNS, mainly involving extrapyramidal tracts, basal ganglia and dorsal nucleus of the vagus. These patients have an intact peripheral autonomic nervous system but are unable to activate it. (In primary autonomic insufficiency there is depletion of norepinephrine in the peripheral autonomic ganglia).
In both these, catecholamine blood levels do not rise on standing, although it may be normal at recumbency in chronic orthostatic hypotension but reduced in primary autonomic insufficiency.
Diagnostic Work-up
Following tests are general work-up tests to find the cause if it is already not apparent.
The workup includes blood tests, x-rays, and cardiac tests. These are
- Basic metabolic panel
- Blood cultures to check for infection
- CBC
- ECG and echocardiography [based on ECG findings]
- Urine examination
- Chest X-ray
- Abdominal ultrasound
Treatment of Hypotension
Acute hypotensive patients would need aggressive measures to control blood pressure. Any loss of blood needs to be controlled and fluid replaced.
Those patients who do not have mild symptoms often need no treatment.
For other patients with symptoms, the patient should be treated for an underlying problem, if present.
Vasoconstrictors could help some patients.
Any medication that could be contributing to the problem should be withdrawn or replaced by another.
Increasing salt and fluid intake may improve the symptoms of hypotension. Salt levels can be boosted by taking salt tablets or adding more salt to food. Fluids increase blood volume and prevent dehydration, and this can impact blood pressure levels.
Prevention of Hypotensive Episodes
In the case of chronic problems, preventing low blood pressure episodes can be achieved through simple lifestyle measures.
- Raising the head of the bed when sleeping
- Change the position slowly in case of orthostatic hypotension. For example, move from being seated or lying down to standing slowly
- In the case of postprandial hypotension, eating small meals frequently rather than eating large meals can be helpful
- Avoid prolonged standing or sitting.
- When sitting or standing keep moving ankles or take one-two steps so that the blood does not pool in the legs and is pumped out by muscular action.
- Keep yourself well-hydrated by proper water intake
- Avoid excessive alcohol intake and caffeinated beverages in the evening and night.
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