Tag: blood pressure

Doctor’s Presence During BP Measurement Triggers Flight-or-fight Response

Photo by Thirdman from Pexels
Photo by Thirdman from Pexels

A small study has shown that a doctor’s presence during a blood pressure measurement skews the results, according to researchers who studied the effect by measuring nerve activity.

The phenomenon known as ‘white coat hypertension‘ is where the mere presence of a medical professional can raise blood pressure. Known about for decades, it occurs in about a third of patients.

In a small study published in the journal Hypertension, researchers probed the effect by measuring blood pressure, heart rate and nerve traffic in the skin and muscles with and without a doctor present.

The researchers found a “drastic reduction” in the body’s alarm response when a doctor was not present, said co-lead author Dr Guido Grassi, professor of internal medicine at the University of Milano-Bicocca.

Blood pressure and heart rate increases in response to a perceived threat, said Dr Meena Madhur, associate professor of medicine in the divisions of clinical pharmacology and cardiology at Vanderbilt University.

“If you’re out in the wild and a bear was charging after you, you’d want your blood vessels in your skin, for example, to constrict and the blood vessels in your muscles to dilate to provide more blood flow to those organs so that you can run really fast,” said Prof Madhur, who was not involved in the new research.

The study included 18 people, 14 of them men, with untreated mild to moderate hypertension. Each participant was examined in a lab, where an electrode measured nerve activity in the skin and muscles. Readings were taken twice in the presence of a doctor and twice without.

Both blood pressure and heart rate rose when the doctor was present, with nerve traffic patterns to the skin and skeletal muscle suggesting a classic fight or flight reaction.

Without the doctor’s presence, cardiovascular and neural responses were “strikingly different,” the researchers wrote. Fight or flight response indications were “entirely absent”.

Peak systolic blood pressure was an average of 14 points lower when the participant was alone than when a doctor was present, and peak heart rate was lowered by nearly 11 beats per minute.

This was the first study to actually measure sympathetic nervous system responses to doctors supervising a blood pressure measurement, the researchers wrote.

The study’s findings illustrated the complexity of blood pressure measurement and how it is affected by involuntary nervous system reactions, Grassi said. “Measurements without the doctor’s presence may better reflect true blood pressure values.”

White coat hypertension is not a new concept, Prof Madhur said, “this just drives home the fact that we should be more conscious of how the blood pressure is taken in the clinic.”

Last year, the American Medical Association and AHA issued a joint report endorsing more blood pressure measurement at home.

Limitations included the small study size due to the complexity of the measurements, the researchers said. Subsequent research would need to examine blood pressure medication as they could affect the fight or flight response, said Orof Madhur.

The work needs to be repeated with more women to examine possible sex differences. And she’d be interested in seeing whether people have the same response to nurses and other medical professionals as they did to doctors in this study.

Previous work shows that when nurses take blood pressure measurements, the white coat effect is reduced.

This latest research emphasises the need for people to handle blood pressure measurements with care, Prof Madhur said.

“I always tell my patients that we really can’t rely on a single office blood pressure measurement, because that’s just a random point in time,” she said.

Prof Madhur said that to take an accurate reading at home, a patient should sit still, with their back straight and supported and feet on the floor, waiting at least a few minutes before recording blood pressure. They should take multiple readings at the same time of day over the course of a week, and bring that log to their doctor’s appointment. Those at-home readings should be the ones used for planning treatment, she said.

“But,” Prof Madhur added, “if we are going to do an office blood pressure reading, it should be taken with the doctor not in the room.”

Source: American Heart Association

Exact Location of Body’s Blood Pressure Sensors Finally Revealed

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After 60 years of fruitless searches by scientists, researchers from the University of Virginia have finally determined the location of our bodies’ natural blood-pressure sensors.

These cellular sensors monitor blood pressure and adjust hormone levels to keep it in check. Scientists have long suspected that these ‘baroreceptors’, may exist in or around specialised kidney cells called renin cells, but no one has been able to locate the baroreceptors within the cell until now.

The new findings, from UVA Health’s Dr Maria Luisa S Sequeira-Lopez and colleagues, finally reveal where the barometers are located, how they work and how they help prevent hypertension or hypotension. The study was published in Circulation Research.

“It was exhilarating to find that the elusive pressure-sensing mechanism, the baroreceptor, was intrinsic to the renin cell, which has the ability to sense and react, both within the same cell,” said Dr Sequeira-Lopez. “So the renin cells are sensors and responders.”

Back in 1957, it was first proposed that a pressure sensor existed inside renin cells because the cells had to know when to release renin, a hormone that helps regulate blood pressure. Though the baroreceptors had to exist, scientists couldn’t tell what it was and whether it was located in renin cells or surrounding cells.

To tackle this decades-old mystery, the study’s researchers used a combination of innovative lab models and determined that the baroreceptor was a ‘mechanotransducer’ inside renin cells. This mechanotransducer detects pressure changes outside the cell, then transmits these mechanical signals to the cell nucleus, akin to how the cochlea turns sound vibrations into nerve impulses.

Through in vitro tests, the researchers found that applying pressure to renin cells triggered changes within the cells and decreased activity of the renin gene, Ren1. The scientists also compared differences in gene activity in kidneys exposed to lower pressure and those exposed to higher pressure.

Ultimately, when the baroreceptors detect excess pressure outside the renin cell, renin production is cut back, while low blood pressure prompts more renin production.

Dr Sequeira-Lopez said she is looking forward to the work to “unravel the signaling and controlling mechanisms of this mechanotransducer and how we can use the information to develop therapies for hypertension.”

Source: University of Virginia