Some Qs. people asked me on science and my replies to them - Part 72

                                                               Interactive Science Series

BP variations and complications during pregnancy ...

Q: My friend says you cannot get low BP during pregnancy. Is this correct?

Krishna: Drop in blood pressure can occur during pregnancy. It occurs because the circulation expands during pregnancy and hormonal changes cause the blood vessels to dilate, leading to a lowering of blood pressure (less than 90/60).

The blood pressure begins to fall in early pregnancy and is usually at its lowest sometime in the middle of the second trimester.  Women may experience symptoms of low blood pressure during pregnancy. These symptoms are similar to symptoms that anyone with low blood pressure might feel. Most commonly, symptoms of low blood pressure in pregnancy include dizziness and even fainting. The lightheadedness can be worse when standing up suddenly or rising from a reclining position. The extent to which blood pressure drops is variable, but in most pregnant women, the systolic pressure drops by 5 to 10 mmHg. The diastolic pressure can drop up to 15 mmHg in a normal pregnancy. These lowered pressures usually last during the pregnancy and return to original levels afterward.

Other factors that can contribute to low blood pressure include: dehydration, anemia, internal bleeding, prolonged bed rest, certain medications, heart conditions, endocrine disorders, infections, nutritional deficiencies, and an allergic reaction. 

Extremely low blood pressure can lead to falls, organ damage, or shock.

Low blood pressure may also be a sign of ectopic pregnancy, which happens when a fertilized egg implants outside of a woman’s uterus.

Symptoms include dizziness, lightheadedness, especially when standing or sitting up, fainting, nausea, tiredness, blurred vision, unusual thirst. clammy, pale, or cold skin, rapid or shallow breathing, lack of concentration.

Pregnant women who are experiencing dizziness due to low blood pressure can take steps to minimize the symptoms and promote safety, such as the following:

Sitting or lying down if they feel faint, to avoid falls
Avoiding standing up too fast from a seated or lying position
Lying on the left side, to increase blood flow to the heart

trying not to stand for long periods of time

eating small meals throughout the day

avoiding to take very hot baths or showers

drinking more water and wearing loose clothing

If the symptoms are severe, please consult your doctor immediately.

Q: Based on the above question ... can you also throw some light on high BP during pregnancy?

Krishna: Sure. 

 High blood pressure, or hypertension, is defined as blood pressure higher than 140/90 mm Hg. High blood pressure during pregnancy isn’t always dangerous. But it can sometimes cause severe health complications for both mother and developing baby.

There are several possible causes of high blood pressure during pregnancy.

These include: being overweight, failing to stay active, smoking, drinking alcohol, first-time pregnancy, a family history of pregnancy-related hypertension, carrying more than one child, age (over 40), assistive technology (such as IVF).

Types of pregnancy-related blood pressure conditions

As a woman progresses in her pregnancy, her blood pressure may change or return to prepregnancy levels. Reasons for this may include the following.

The amount of blood in a woman’s body increases. According to the journal Circulation , a woman’s blood volume increases by as much as 45 percent during pregnancy. This is an extra amount of blood that the heart must pump throughout the body.

The left ventricle (left side of the heart that does a significant amount of pumping) becomes thicker and larger. This temporary effect allows the heart to work harder to support the increased blood volume.

Thekidneys release increased amounts of vasopressin, a hormone that leads to increased water retention.

In most cases, high blood pressure during pregnancy will subside almost immediately after the baby is delivered. In cases where blood pressure remains elevated, your doctor may prescribe medication to get it back to normal.

*preeclampsia symptoms. Symptoms include:

• protein in a urine sample
• abnormal swelling in hands and feet
• persistent headaches

HELLP is an acronym that stands for hemolysis, elevated liver enzymes, and low platelet count. This condition is severe and life-threatening, and can be a complication of preeclampsia. Symptoms associated with HELLP include nausea, vomiting, headache, and upper abdominal pain. Because HELLP syndrome can severely damage organ systems vital to life, emergency medical care is aimed at reducing blood pressure for the health of the mother and the baby. In some cases, a premature delivery is required.

High blood pressure during pregnancy can also have an effect on the baby’s growth rate. This can result in low birth weight.
other complications include:

placental abruption, a medical emergency during which the placenta detaches from the uterus prematurely
preterm delivery, defined as delivery prior to 38 weeks of pregnancy
caesarean delivery
How to prevent high BP during pregnancy...
Common risk factors for high blood pressure, such as obesity and a history of high blood pressure, can be minimized through diet and exercise. Of course, during pregnancy, it is inevitable that you will gain some weight.
Keep a specific diet plan with the help of a nuritionist.
Pregnant women should steer clear of smoking and drinking alcohol, both of which have been known to raise blood pressure. Pregnancy causes hormone shifts, as well as psychological and physical changes. This can bring on stress, which can make high blood pressure harder to manage. Try stress reduction techniques such as yoga and meditation.

If you are suffering from more complications, please consult your doctor. 

Q: My blood pressure will be high when I take it in a hospital. When I use my own meter at my home, the reading will be less. Why is this?

Krishna: Recent research suggests that you should take atleast three readings and then take an average of the three for the best result. Moreover, you should calibrate [correlate the readings of (an instrument) with those of a standard in order to check the instrument's accuracy] your BP machine properly to get the right reading. 

Most people feel nervous when they visit a hospital. "White coat hypertension" is a syndrome whereby a patient's feeling of anxiety in a medical environment results in an abnormally high reading when their blood pressure is measured.

Your doctor also should do these things before taking your BP readings ...

1. Ask if you have eaten, drunk or smoked in the last 30 mins? This can add over 10 points to your numbers
2. Look under the table to check your feet were not crossed (this can add another 4 or 5 to the score, if you crossed your legs)
3. Take your BP at the end of the consultation to make sure you were seated for at least 10 mins before taking a reading
4. Arrange for a high back chair and made sure you were not leaning forward.

Watch this video that tells how you should take BP readings

Updates: 

We now have information that says ... Your Blood Pressure May Vary Significantly Depending on Where on Your Body It's Taken

Even in the same patient, blood pressure readings taken on opposite sides or at different places on the leg or arm could yield significantly different results, and this extreme variability might be putting already vulnerable lives at risk.

For decades now, physicians have largely assumed there's little difference in non-invasive blood pressure measurements taken at different points on a person's body. No matter where you cuff it, on the upper arm, wrist or thigh, the readings will lie in the same ball park.

Even when more invasive methods are used, like inserted catheters that read arterial blood pressure at great accuracy, the readings are predicted to generally match blood pressure in the upper arm. But is that really right?

To test these various assumptions, researchers at the University of Texas Southwestern worked with 80 patients in the NSICU, split almost equally between men and women who were around the age of 53.

These patients had been admitted to the unit for several serious neurological problems, including stroke, subarachnoid hemorrhages, and brain tumours.

Sitting upright in their hospital beds, the patients had their blood pressure taken on both upper arms and then on their wrists. At the same time, 29 of these patients were also given arterial blood pressure sensors.

Usually, the differences between blood pressure sites don't differ by more than a few points, but in some patients, the authors found dramatic 40 point discrepancies that could radically impact how the patient is cared for.

In total, the range of mean differences between systolic blood pressure readings - from site to site and method to method - were all 10 to 11 points apart.

"This is significant since even 5 mmHg on the SBP is enough to make a difference when deciding to intervene or withhold treatment.

Comparing the systolic pressure in both left and right upper arms, the authors found an average difference of 8 points, while diastolic measures varied by 6 points.

"If we take pressure in one arm, a patient seems fine, but in the other arm, they're in a crisis", teh researchers say.

And that's also true for the same arm and wrist.The upper arm had consistently lower measurements than the wrist, which, the authors argue, is probably because the wrist's tendons and bones are less reactive to external pressure than a muscle.

Whatever the cause, these two sites differed on average by up to 13 points in systolic pressure and about 5 points in diastolic measures. The authors say this "consistent mismatch" is worth considering in the clinical setting and in practice. In other words, avoid wrist cuffs if at all possible.

The authors aren't sure why these differences exist - blood pressure exists in a complicated web of physiological processes - only that their results indicate blood pressure is not the same throughout the body at any given time.

Even arterial pressure, which is considered a gold standard in medicine, was found to vary from the cuff measurements by as much as 15 points give or take.

Of course, the sample size in this study is quite small and only among a niche subset of patients. Nevertheless, previous research has also suggested blood pressure differs between the left and right arms.

"Therefore," the authors conclude, "location does matter when measuring BP; however, this study cannot conclusively recommend which site to use above others."

Further investigation is needed through larger trials, testing different sites of the body and blood pressure methods, but if the discrepancies keep popping up we might need to change our protocols.

Perhaps, for instance, taking several readings at different sites around the body and averaging them is a better way to predict how our blood is actually pumping at any given moment.

The study was published in Scientific Reports.

https://www.nature.com/articles/s41598-020-60414-7#Sec5

https://www.sciencealert.com/your-blood-pressure-may-vary-quite-a-l...