Have We Misunderstood Blood Pressure?

Never have two little numbers perplexed the healthcare system as much as your systolic and diastolic blood pressure readings. Hypertension, a condition which costs the US Healthcare System about $48.6 billion each year, is the subject of much research and speculation all the same. However, are YOU even entirely sure what blood pressure means? And what is it about your blood pressure that has doctors so concerned? Is their concern warranted, or do they just need to think about blood pressure from a different angle? Great questions! Let’s take a closer look.

Your blood pressure is regulated by two major systems: the nervous system and urinary system. Your nervous system oversees rapid regulation of the pressure in your arteries because well…we need it! Long before you landed that nice desk job with good benefits (I hope), your ancestors had to hunt and travel for survival. Danger will not wait for your kidneys to get your blood pumping. So, we must rely on the nervous system to prepare us for “fight or flight.” But as civilization advanced, wild deer and boar turned into online job listings, and our predators turned into work bosses and the IRS. This remnant of evolution we affectionately now know as “anxiety.”

Don’t think the nervous system is powerful? Well according to Guyton and Hall, the classic human physiology text for medical schools and chiropractic colleges alike, the nervous system can increase blood pressure to as high as twice normal within 5 to 10 seconds! It does so by simultaneously constricting your arterioles to increase total resistance, constricting veins to rapidly pump blood into the arteries, increasing heart rate to as much as 3 times normal, AND increasing the strength of each heart contraction (beat). Dismissing such power as “white coat hypertension” or “being nervous” is a mistake which can cost billions in unnecessary tests and procedures.

The kidneys are another story. Their main role is eliminating excess fluid volume from the body in response to high arterial pressure, as well as retaining fluid when blood pressure is too low. They accomplish this through the production of several hormones like ADH, Aldosterone, and Angiotensin. Now I’m sure you might have heard the negative association between high salt intake and blood pressure. While an excess of sodium in the diet can lead to health problems down the line, salt is not as powerful as you might think in terms of increasing your chronic blood pressure readings. In fact, chronic increases in the intake of salt and water as high as SIX times normal are usually only associated with small increases in arterial pressure (Guyton). However, there’s a bit of a Catch-22 here because long term high salt intake (we’re talking years) may actually damage your kidneys which would increase your blood pressure. So the moral of that confusing story is if your kidneys are healthy then high salt intake may not increase your blood pressure long term. But also, it is best to make SOME effort to lower your sodium intake lest you run the risk of damaging your kidneys in the long run.

One of my patients had a blood pressure reading of 174/90 (that’s WITH medication) on his first visit. Upon further questioning, I noticed a large part of his hypertension could be due to an exaggerated alarm reaction to having his blood pressure measured. In other words, his nervous system has been trained to rapidly and powerfully increase his blood pressure in response to his worry about his health. This story does have a happy ending though…through retraining his nervous system to not fear the assessment combined with a steady exercise routine, his next reading was 116/66! In only one short month, we were able to identify the TRUE cause for his hypertension. So, I urge you to re-examine the factors that contribute to your hypertension, whether it be with your primary care physician or yours truly!

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