What Being Cold Does to Blood Pressure!

I just finished the second semester of anatomy and physiology and one of the topics we studied was the heart.  I was hoping one of our final exam essay questions would be on blood pressure because I’ve been measuring mine for over a year and felt I could eloquently discuss the topic, as well as pharmaceutical agents that I no longer feel I need to control it.  Over that time, I have learned what increases my blood pressure, so I was happy to formally learn about this topic in my class.

I can’t remember whether temperature was specifically discussed in the textbook, but I know vasoconstriction was covered and how it affects blood pressure.  We also learned about (I think in first semester anatomy and physiology) the sympathetic nervous system, including sweating and shivering.  I can put all of that together to explain what happened to me this morning at Waffle House!

I decided to go have a nice low-carb breakfast of grilled chicken and scrambled eggs while my car was at the shop.  I chose an out of the way booth, recognizing that it was cold, but not realizing how terrible it would be to sit there.  While I was waiting for my food, I was freezing!  I decided to take my blood pressure… it was 174/121 mmHg (pulse 75)!  There I was again with a hypertensive crisis on my hands!  For comparison, my blood pressure three hours earlier was 112/75 mmHg (pulse 72).

I made it through my meal and the waitress was too busy to give me my check, so I moved to a warmer spot in the restaurant.  I checked it again, 151/106 mmHg (pulse 70).  I finally got to pay and I walked back to the car place.  Upon my return (right after walking), it was 136/96 mmHg (pulse 73).  That’s not the best measurement ever, but it sure beats the “hypertensive crisis” 45-minutes earlier!  Crisis averted!!

So, what happened?  Well, the cold temperatures cause the skin to feel cold.  That stimulates the sympathetic nervous system receptors.  The physiological response to cold is vasoconstriction of the blood vessels in the skin and extremities, such as my arm, where my blood pressure is taken.  This increases my blood pressure and blood viscosity, which decreases cardiac volume.  It also makes the heart work harder to pump blood.  Was I really having a “hypertensive crisis”?  I don’t think so, my body was just telling me to go someplace and warm up!

Should the coldness of Waffle House have that much of an effect on my blood pressure?  Maybe not, but my blood pressure tends to have large daily variations.  The affects of stress, temperature, medication, exercise, etc. is always more extreme than I would expect.

My blood pressure generally follows the expected diurnal pattern: low in the morning, rises throughout the day, declines in the evening, lowest during the night.  I don’t know how much it’s supposed to swing, but it is well documented that there are variations.

Let me change gears here, because I realized my “hypertensive crisis” very well could be a problem for me one day.  Normal blood pressure is now defined as being less than 120/80 mmHg, but there’s really no mention in the recommendations as “when” that should be.

I got diagnosed with high blood pressure before the guideline change because my blood pressure was high during the day, especially when I was at the doctor’s office and felt stressed.  My blood pressure increased more as the doctors became concerned about the fact that my blood pressure was high (do you see the cycle starting here?).

I got put on medication for my high blood pressure and the first time I took it, my blood pressure fell crazy low!  Over time taking the medication, my daily blood pressure continued to be high during my appointments, so it seemed the medication wasn’t helping.  I think my body was even more stressed out that my blood pressure was high and the medication wasn’t working.  I got prescribed an additional medication, which I refused to take.

Over time, the original medication seemed to bring my blood pressure to a place the doctors seemed happy with.  I don’t believe anything changed.  I think what was happening there was my body was getting used to me taking my blood pressure every day and over time, I learned when it was best to take it (and not being in the doctor’s office seemed to help as well). Eventually, I got less nervous that my blood pressure would be insanely high, and it became lower, eventually even in the doctor’s office.

Everyone seemed pleased that the medication was helping my blood pressure, but was it?  My blood pressure was still above 120/80 mmHg, it just wasn’t the 155/110 mmHg kind of values that I was seeing initially.  It probably averaged around 135/85 mmHg (normal back then was under 140/90 mmHg).

I decided that I could get those same values without medication, so I stopped taking it. Guess what?  The medication didn’t make a difference.  My blood pressure remained essentially the same.  It still averages no more than 135/85 mmHg, unless I am super stressed, anxious, taking medicine (DHEA is a great example), cold, etc.  It improved some during my first 90-day challenge, I believe due to yoga, and that’s written about in Blood Pressure – Also on the Decline.

Unfortunately, those stressors I mentioned do happen and that elevates my blood pressure in the short-term. That’s why I started taking my blood pressure six times throughout the day and throwing out the high and low values and averaging the rest to find my daily average blood pressure.  I described that idea in My 2nd 90-Day Goals.

This is a plot of my average blood pressure so far during this 90-days (weekly bins of daily data).  DHEA elevated some measurements of the first two weeks, but with throwing out the high and low, the overall effect is lessened.  Look, my blood pressure averages are around 135/85 mmHg… Is that considered to be good or is that bad?


My average first thing in the morning blood pressure (sitting up, still, after being awake for ~15 minutes) is 120/80 (+/- 7/6) mmHg. Is that good or is that bad?

My average evening blood pressure is 125/84 (+/- 7/7) mmHg.  Is that good or is that bad?

Do I have high blood pressure? Sure, my blood pressure gets high sometimes, but I believe that’s what it’s supposed to do under situations when my body perceives stress!  I am not sure why it was decided that 120/80 mmHg was elevated blood pressure and 130/80 was hypertension stage 1.

With the changes of blood pressure limits came new rules for measuring blood pressure: don’t measure after exercise, caffeine, etc., and sit quietly for 5 minutes before the measurement. Now I don’t know about you, but for me, sitting there for 5 minutes trying to breathe and be calm to make my blood pressure go down often has the opposite effect!!

I think I was much more comfortable with the old rules. The standard was achievable. And even more so, I didn’t feel like I was always being judged for my blood pressure and constantly worried that my value will be above the magic 120/80 mmHg when measured (it still often is in the doctor’s office).

And then, when it’s high, I feel defensive and explain that I get nervous when someone is about to put an IV port in my vein or I’m stressed because I just found out my neighborhood is flooded and I won’t be able to get home any time soon (literally my last two reasons).  Those type of things tend increase my blood pressure and I don’t seem to have any control of that.  That silly sympathetic is causing me problems again!

I then get asked “have you ever been diagnosed with hypertension?” I have to say yes; and then when asked about medication, my response is I don’t take any.

The next question is generally, “how are you controlling your hypertension?” Well, through diet, exercise, and stress reduction – of course; this isn’t helping the latter, in fact, neither are the new guidelines.

I get to have a similar conversation regarding my cholesterol. Only there, I can say that I’ve had a cardiac calcium screen and have zero blockage, despite a higher than 200 total cholesterol and high LDL. Additionally, my HDL, triglycerides, and ratios are good. For cholesterol, I have an answer because I paid to have additional tests done to show that I do not need medication.  I wish I had that “out” here!

One of these days, I’m going to have the dreaded “hypertensive crisis” happen in a doctor’s office and I will be promptly carted to the emergency room, filled with medication and carbohydrates, and treated like I have a horrible disease, when it’s just my sympathetic nervous system trying to help me out.

I am so glad I do yoga… maybe one day my body’s stress response will be a thing of the past, and I will be stoic and calm in all situations. I’m better than I used to be for sure, but I’m certainly not there yet!

I suspect I’m not the only one who is now in this situation… My concern is that other people may just accept their medication more graciously than I do! That makes me sad and likely increases my blood pressure too 😉

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