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His blood pressure was 254/150. Readings of 180/120 are considered an emergency.

Energy drinks are pictured on shop shelves in London on August 30, 2018. Credit: Getty | DANIEL LEAL

Sometimes, downing an energy drink can feel like refueling your battery. But with too much, that jolt can turn into a catastrophic surge that fries the wiring and blows a fuse. That was the unfortunate and alarming case for a man in the UK several years ago, according to a case report this week in BMJ Case Reports.

The man, who was in his 50s and otherwise healthy, showed up at a hospital after the entire left side of his body abruptly went numb and he was left with clumsy, uncoordinated muscle movements (ataxia). His blood pressure was astonishingly high, at 254/150 mm Hg. For context, a normal reading is under 120/80, while anything over 180/120 is considered a hypertensive crisis, which is a medical emergency.

The man had suffered a mild stroke, and his extremely high blood pressure was an obvious factor. But why his blood pressure had reached stratospheric heights was far less obvious to his doctors, according to the retrospective case report written by Martha Coyle and Sunil Munshi of Nottingham University Hospital.

Upon examining the man, the doctors described him as fit and healthy. He didn’t smoke, drink, or use any drugs. His blood work was all completely normal. His cholesterol, blood sugar levels, markers for kidney and liver function—everything from routine tests came back normal. Specialized tests for things like autoimmune and clotting disorders were also negative. Heart tests found no problems. Urine tests and abdominal scans found no problems with his other organs.

Power surge

Still, a computed tomography (CT) scan of his head found evidence of spasms in arteries in his brain, which are strongly linked to high blood pressure. And magnetic resonance imaging (MRI) found an infarct (dead tissue) in his thalamus, a central, deep part of the brain, which, among many critical functions, relays sensory and motor signals. In all, it seemed his spasming arteries had cut off blood supply to this part of his brain, causing his stroke, subsequent numbness, and ataxia.

The man was hospitalized and started on treatment and therapy for stroke recovery. He was also put on two blood pressure medications to get his numbers down. Upon discharge three days later, his blood pressure had come down some, but only to 170/80 mm Hg. Still very high, but no longer a crisis. He was told to closely monitor it at home and return for follow-up checks.

In the meantime, the doctors pondered his case, exploring all the possible explanations—an irregular heart rhythm, a cardiac defect, an embolism, plaque in his arteries. There was no clear answer.

Over the next three months, the man came for his follow-up visits. In terms of his stroke, he was making “excellent” functional recovery. But his blood pressure was going back up, particularly the systolic readings—the top number that signifies the pressure in the circulatory system when the heart contracts, in contrast to the bottom, diastolic number, indicating the pressure when the heart relaxes. At his follow-up visits, his systolic reading ranged from 190 to 230. At one point, he was hospitalized again for a hypertensive crisis.

Four weeks into his recovery, he was on five different drugs to try to bring down his blood pressure. At that point, doctors pushed for more lifestyle information from the man, who finally revealed that he had a habit of drinking an average of eight high-potency energy drinks every day.

Cumulating risk

Each of the 16-ounce drinks was labeled as containing 160 mg of caffeine, a stimulant that can raise blood pressure. For reference, there’s about 90 mg of caffeine in a normal cup of coffee. So eight of these energy drinks would be 1,280 mg, the equivalent of a little more than 14 cups of coffee a day. But the doctors point out that the labeled amount of caffeine was only the “pure caffeine” amount. Such energy drinks contain additional ingredients, like guarana (a plant native to the Amazon used as a stimulant), that can contain “hidden caffeine.” Guarana is “thought to contain caffeine at twice the concentration of a coffee bean,” Coyle and Munshi write.

The doctors hypothesize that the combination of ingredients in energy drinks—taurine, guarana, ginseng, and glucuronolactone—can work together to boost the effects of the beverages’ pure caffeine and high sugar content, leading to stroke risk and, in the man’s case, a hypertensive crisis. Further, while a temporary surge after a drink may not lead to an emergency or seem particularly risky, some data has hinted that the effects can add up. For instance, one study looked at blood pressure surges from daily consumption of an energy drink over the course of a week. The blood pressure spikes on day 7 were higher than those on day 1, suggesting a cumulative effect.

Upon hearing about his energy drink habit, doctors immediately told him to stop. He did. After a week, his blood pressure dropped to more normal levels, with systolic readings of 120 to 130. He was weaned off his five blood pressure medications. Three weeks after his energy drink abstinence, he was off all of the drugs and had normal blood pressure readings.

The man has subsequently been followed for eight years, and his blood pressure is still normal without drugs and off energy drinks. However, he still has effects from the stroke.

In a “patient’s perspective” included in the case report, the man said: “I obviously wasn’t aware of the dangers drinking energy drinks were causing to myself, (I) have been left with numbness (in my) left hand side hand and fingers, foot and toes even after 8 years.”

Coyle and Munshi conclude that the case shows that “it is possible that both acute and chronic intake of [energy drinks] may increase [cardiovascular disease] and stroke risk, and importantly, this may be reversible.” They recommend more regulation around the beverages and for doctors to make sure to ask their patients about whether they drink them.

Beth is Ars Technica’s Senior Health Reporter. Beth has a Ph.D. in microbiology from the University of North Carolina at Chapel Hill and attended the Science Communication program at the University of California, Santa Cruz. She specializes in covering infectious diseases, public health, and microbes.