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What is Low Blood Pressure?

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Updated July 13, 2007

Question: What is Low Blood Pressure?
Answer: First off, "low blood pressure" is not strictly defined. While high blood pressure has clear numerical definitions, low blood pressure is not defined by a universally accepted value. In the past, some attempts were made to standardize the meaning of "low blood pressure," but no official set of guidelines is currently supported by any medical authority.

Generally speaking, doctors sometimes refer to a blood pressure of 90/60 as a rough rule of thumb when evaluating patients because experience seems to show that this is the point at which symptoms tend to develop.

In general, if you have no history of medical problems and are not experiencing any symptoms, a low blood pressure reading is not cause for concern. If you discover on your own that your blood pressure is below 120/80, you should mention it to your doctor during your next visit but probably don’t need to schedule a special appointment unless you know that the low reading represents a significant change from your average blood pressure.

Is Low Blood Pressure Dangerous?

With very few exceptions, chronic blood pressure below 120/80 is not dangerous. Low blood pressure is usually considered dangerous only when it causes symptoms or results from sudden blood pressure decreases. In cases where the blood pressure drops suddenly, it isn’t actually the low blood pressure itself that causes the danger, but rather the sudden change from a higher value to a lower value. Sudden changes in blood pressure can cause interruptions in the blood supply to the heart, kidneys and brain, and will almost always be accompanied by distinctive symptoms. An example of this situation is orthostatic hypotension, where changes in body position (usually a change from sitting to standing) are accompanied by a rapid drop in blood pressure. Usually, sudden episodes of low blood pressure are a sign that something else might be wrong, and are typically an indication for a full medical workup.

There is some recent research that suggests chronic low blood pressure may be of unique importance in people who have underlying kidney disease. For these people, chronic low blood pressure appears to trigger a complicated cascade of events that can lead to blood vessel damage and may lead to a stroke. Because this data is relatively new, no clear blood pressure guidelines for these patients have yet been developed.



More About Low Blood Pressure:

Sources:

  1. Christensen KL, Mulvany MJ. Vasodilatation, Not Hypotension, Improves Resistance Vessel Design During Treatment of Essential Hypertension: A Literature Survey.Journal of Hypertension. 2001 Jun;19(6):1001-6.
  2. Palma Gamiz JL, et al. Iberian Multicenter Imidapril Study on Hypertension: A twelve-week, multicenter, randomized, double-blind, parallel-group, noninferiority trial of the antihypertensive efficacy and tolerability of imidapril and candesartan in adult patients with mild to moderate essential hypertension: the Iberian Multicenter Imidapril Study on Hypertension (IMISH).
  3. Shin DD, et al. Review of Current and Investigational Pharmacologic Agents for Acute Heart Failure syndromes. American Journal of Cardiology. 2007 Jan 22;99(2A):4A-23A.
  4. Verheij J, et al. Cardiac response is greater for colloid than saline fluid loading after cardiac or vascular surgery. Intensive Care Medicine. 2006 Jul;32(7):1030-8.
  5. Eldadah BA, et al. Failure of propranolol to prevent tilt-evoked systemic vasodilatation, adrenaline release and neurocardiogenic syncope. Clinical Science (London). 2006 Sep;111(3):209-16.
  6. Naschitz JE, Slobodin G, Elias N, Rosner I. The patient with supine hypertension and orthostatic hypotension: a clinical dilemma.Postgraduate Medical Journal. 2006 Apr;82(966):246-53.
  7. Tipre DN, Goldstein DS. Cardiac and extracardiac sympathetic denervation in Parkinson's disease with orthostatic hypotension and in pure autonomic failure. Journal of Nuclear Medicine. 2005 Nov;46(11):1775-81.
  8. Peacock WF 4th, et al. Observation unit treatment of heart failure with nesiritide: results from the proaction trial. Journal of Emergency Medicine. 2005 Oct;29(3):243-52.

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