Houston doctors warn Texas heat affects blood pressure medicine

Houston doctors warn Texas heat affects blood pressure medicine

Enrique Barrientos pulled weeds in his garden for about 10 minutes before the energy left his body.

The 69-year-old Katy resident loves yardwork. It helps him decompress after long days in front of his computer. But on this hot afternoon in early May, the combination of sweltering temperatures and newly prescribed blood pressure medication left him feeling depleted.

He walked inside and passed out.

“At this moment I’m not doing anymore outside activity,” said Barrientos, who is now recovering from the incident with an adjusted dosage. “Especially these days, because the temperature is so high.”

As Houston sets heat records and other parts of the world see unusually high temperatures, people taking certain medications — including those that reduce blood pressure — face an increased risk of exhaustion and dehydration. In more serious cases, the combination can lead to fainting, kidney failure or life-threatening heart problems.

Doctors stress that people should not stop taking prescribed medications simply because of the heat. But “as a general rule of thumb, if you’re on blood pressure medications, you should probably take extra caution, especially in the hotter months of the year,” said Dr. Wafi Momin, the cardiologist at UTHealth Houston and Memorial Hermann Katy Hospital who treated Barrientos.

Nearly one out of two adults in the U.S. have high blood pressure, according to the Centers for Disease Control and Prevention. In the summer, people who regulate it through medication should generally avoid outdoor activity between 11 a.m. and 5 p.m., doctors say. Common heat safety measures — staying hydrated, wearing loose-fitting clothes, seeking shade and frequent breaks — reduce the risk for those who need to be outdoors.

Barrientos struggled with high blood pressure and cholesterol before suffering a heart attack in April. He was raking leaves in the peak afternoon heat for more than an hour when exhaustion and dizziness crept in. Then he felt chest pain, which he chalked up to a stomach problem.

The pain lingered throughout the following day. His family took him to the emergency room at Memorial Hermann Katy Hospital, where doctors pinpointed a blockage in one of his coronary blood vessels. He received stents and returned home with Metoprolol, a beta blocker, in addition to his previously prescribed blood pressure medicine.

Momin believes Barrientos’s underlying coronary disease — not his medication — triggered that heart attack. The fainting incident, however, was more likely due to his new medication, he said, adding that heat risks are higher for patients still acclimating to newer therapeutics.

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Metoprolol causes the heart to beat slower and widens the veins and arteries to improve blood flow. Barrientos was already taking Lisinopril, an ACE inhibitor, which also dilates the blood vessels. Both of these medications, coupled with high temperatures, can cause blood pressure to “drop way too much,” said Momin.

“When that happens, you can get dizzy, lightheaded, and … you can end up passing out,” he said.

That’s what happened to Barrientos when he returned to the yard, a few weeks after he left the hospital. The symptoms could be more severe.

ACE inhibitors can impair the kidneys’ ability to regulate heat-related injuries, which, in rare cases, may lead to cardiac arrest, said Dr. Donald Molony, professor of renal diseases and hypertension with McGovern Medical School at UTHealth Houston and nephrologist at Memorial Hermann.

Other medications can become dangerous with prolonged heat exposure.

Diuretics, commonly used to reduce blood pressure, expel water from the body through urination and increase the risk of dehydration. Widely used anti-depressants — including Prozac, Zoloft and Lexapro – can cause excessive sweating, which also leads to dehydration.

Dr. Asim Shah, professor and executive vice chair in the Menninger Department of Psychiatry and Behavioral Sciences at Baylor College of Medicine, said the mixture of heat and anti-depressants also increases the risk of serotonin syndrome, which causes confusion, agitation, sweating, shivering, diarrhea and muscle twitching.

The hotter weather triggers long-term concerns for those who treat people more prone to heat-related injuries. Momin said more patients are complaining of excessive heat and asking questions about their dosage. Public officials are taking notice, too. U.S. Rep. Sylvia Garcia, a Houston Democrat, recently proposed legislation to establish mandatory paid work breaks on construction sites.

For outdoor laborers, increasing the frequency of water breaks is an important way to guard against heat stroke, said Molony. But “getting out of the heat is just as important as anything else,” he said.

“(The heat) does worry me,” he said. “And it should worry everyone, because we’re not biologically prepared to endure these kinds of heat environments and still work outside.”

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