The ups and downs of blood pressure

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By Dr. Victor Dumaguing

To Your Health

Friday, March 21, 2014

THE cold and chilly weather that ushered in 2014 has brought unprecedented and significant rise in hospitalization of patients suffering from myocardial infarction (heart attack) and brain attack (stroke) recorded in the January as well as February census of both government and private hospitals in Baguio, compared with the same period last year.

A brief review of the determinants or factors that affect or influence blood pressure readings would help explain the phenomenon. Blood pressure is based on heart's activity- its heart rate and stroke volume, the amount of blood the heart ejects for every contraction.

Normal heart rate is 60-100 beats per minute, although cardiologists recommend a slower rate in the 70s. For healthy hearts, 70-90 ml of blood is ejected per heart beat, so that if we multiply heart rate and stroke volume, the product should be equal or come very close to 5000 ml or five liters which is the normal cardiac output- amount of blood ejeceted by the heart in one full minute of contraction.


The other major and crucial determinant of blood pressure is the total peripheral resistance or simply put, the pressure exerted by the blood on the walls of blood vessels as the blood flows through.

Vasoconstriction is when the lumen or the opening of the blood vessels becomes smaller, thus increasing peripheral resistance, resulting to rise in blood pressure. Thus, vasodilatation, or loosening or widening of the lumen of blood vessels, has the opposite effect, in the sense that the pressure on the walls of blood vessels decreases, leading to a decrease in peripheral resistance, thus, lower blood pressure.

At this juncture, let me share with our readers the influx or shall we say exodus of balikbayans back to dear old Philippines during the Christmas season. Of course, in all probability, it is to come home, renew bonds of friendship, have clan reunions and share with relatives , especially the marginalized ones piles of spam, Irish spring, chocolates, shampoos and towels collected from sales , which are abundant in the US. However, it should also be emphasized that , especially for the senior citizens, coming home to a warmer weather away from the snowstorms, sleet and freezing climes of winter, would significantly reduce their arthritis pains and for those with hypertension and heart disease. Their cardiologists or internist had advised them to seek warmer, more comfortable climes.

Cold weather and freezing temperatures cause the blood vessels to constrict i.e. to make the opening of the vessels much smaller.

Because of the decrease in luminal diameter of blood vessels, the pressure on its walls also increase, thus increasing total peripheral resistance. Now, since there seems to be a "blockade or obstruction" to blood flow because of the smaller opening, the heart has to work harder, that is, pump stronger in order to overcome that resistance in order to bring nutrients and life-saving oxygen to the 75 trillion or so cells of the human body. With an extra burden of work imposed on the heart, obviously, its muscles would need more energy or power to contract stronger. Thus on a background of a heart, which to start with is no longer normal because of disease- cholesterol, triglycerides, diabetes, old age- that heart would easily succumb to a heart attack
Thus when the mercury dipped to the 10s and even 9 degree Celsius, it is highly probable that our beloved patients felt the signs and symptoms of chest pains, easy fatigability, palpitations and the tell-tale signs of an impending stroke like nape pains, dizziness, blurring of vision, numbness of an arm or leg.

March has marched in but the early dawn hours are still chilly at times. Keep warm and healthy.

Next Week. When is Blood Pressure Highest?

Published in the Sun.Star Baguio newspaper on March 22, 2014.


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