It can be varied, and generally the diagnostic line relies as much of symptoms as the exact value, since some people can be fine on 90/50, whereas others can have problems at 100/60.
There are three main causes of low blood pressure:
- Cardiogenic - The heart isn't pumping enough blood around.
- Vasodilation - The peripheral vessels have all dilated, meaning there is a much large space for blood in the body, and there isn't blood to go around.
- Hypovolaemia - There's not enough blood going around
Clinical and Associated Features
That is pretty much it. The other things you might experience will be from the cause, or from complications. So, if you go into shock, you will get reduced capillary refill time, tachycardia, shortness of breath.
A common symptom is postural hypotension, or orthostatic hypotension, where people get light headed on standing. It is diagnosed with a sitting standing blood pressure measurement. Get them to sit for five minutes, take a reading, get them to do one as soon as they stand up. Generally this is treated the same as hypotension.
- Iatrogenic - taking drugs to treat high blood pressure (hypertension) - especially diuretics and alpha blockers.
- Heart - Myocardial infarction and congestive heart failure can lead to cardiogenic shock.
- Diabetes - something to do with the peripheral neuropathy reducing autonomic regulation of peripheral blood vessels.
- Addison's disease - this can lead to cause a loss of sodium, resulting in low blood volume.
- Shock - common causes are loss of blood due to serious injury, loss of fluid due to burns or anaphylaxis.
- Anaesthesia - many types of anaesthetic drug can cause hypotension.
Problematic sustained hypotension without a more sinister cause is very rare. Treat the cause, usually shock or iatragenic, and get on with your life!.