Hypotension is diminished blood pressure. This could be acute or chronic.
Acute Recumbent Hypotension
A sudden fall in the blood pressure may be due to cardiovascular reasons such as acute myocardial infarction, pulmonary embolism, dissecting aneurysm, ventricular tachycardia, cardiac rupture.
Reduction of intravascular volume contraction due to bleeding , vomiting, diarrhea, burns, intestinal obstruction, periotonitis, etc.
Anaphylaxis and septicemia are other causes.
Acute hypotension is accompanied by tachycardia which is body’s attempt to pump more blood in order to compensate for reduction in available volume. In vasovagal attacks, hypotension is accompanied bradycardia or reduction in heart rate.
Treatment is geared towards correction of blood pressure and the causative disease both. Patient is kept in lying position with legs raised. Steroids, atrpine, vasoconstrictors are the drugs used in correction of blood pressure as well as to treat the causing disease.
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 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 erects posture are abolished.
- Low output cardiac failure
- LV dysfunction
- Cardiac tamponade
- Constructive pericarditis
- Tight mitral stenosis
- Left atrial myxoma
2. Supine hypotension of pregnancy
- Addison’s disease
- Serotonin secreting tumors
- Diabetic neuropathy
- Extensive lumbosacral sympathectomy
- Peripheral neuropathy
- Tabes dorsalis
- Multiple sclerosis
5. Chronic idiopathic orthostatic hyptension
This occurs due to primary autonomic insufficient 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 lachrymal and salivary secretion, bladder atony and impotency.
- Mechanical: Elastic bandages over legs, head up position in bed etc.
- Volume expansion with high fluid and salt intake
- Fludrocortisone supplement
- Sympathomimetics-Ephedrine, amphetamine, L-dopa
- Prostaglandin synthesis inhibitors like indomethacin
- Alpha 2 receptor agonists
- 5. Atrial pacing
This is chronic orthostatic hypotension with degeneration of CNS, mainly involving extrapyrimidal tracts, basal ganglia and dorsal nucleus of Vagus. These patients have 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.