When Vampires Attack: How Your Body Reacts to Extreme Blood Loss

Portrait of a little boy dressed up as halloween vampire

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It’s Halloween and the number of vampire attacks in your neighborhood may be on the rise! What would happen to your body if you were unlucky enough to be the victim of a blood-sucking vampire?

The average adult has about 1 to 1.5 gallons of blood circulating in their body. Maintaining this amount of blood is very important—proper blood volume helps keep your blood pressure at a steady level and moves the right amount of blood around your body. As your heart pumps blood through your blood vessels, the blood carries nutrients and oxygen to your organs so that they have energy to do their jobs. The blood also takes away the waste that your organs produce.

When you lose a large amount of blood very rapidly (such as during a vampire attack) your blood pressure drops quickly. This is similar to having a punctured bicycle tire. As the air escapes through the hole, there is less pressure in your tire. During an episode of significant blood loss, your body starts to take action to increase blood volume and blood pressure:

  • Sensors called baroreceptors detect the decrease in blood pressure and cause your heart to pump faster and your blood vessels to narrow (constrict).
  • Your body releases chemicals called catecholamines, which also cause your heart to pump faster and your blood vessels to constrict.
  • Your pituitary gland releases a chemical called vasopressin. Vasopressin constricts blood vessels and helps your body hold on to as much water as possible by decreasing the amount of urine you produce.

When blood vessels constrict, the blood inside the vessels push against the sides of the vessel more, causing blood pressure to increase. Increased blood pressure reduces the amount of blood needed to fill your vessels.

If these actions are unable to restore your blood pressure, you can go into shock. Shock occurs when your blood pressure is so low that not enough blood is getting to your organs. In a state of shock, your heart, liver, kidneys and brain can’t function properly and they start to die from lack of oxygen and nutrients. You’ll eventually lose consciousness if you don’t get urgent medical attention—typically with intravenous fluids—to raise your blood pressure and increase circulation.

If you choose to trick or treat this Halloween, stay safe. Carry some garlic with you to ward off those pesky vampires and dial 911 ASAP if you have a run-in with a fanged stranger.

Dao Ho, PhD

Dao H. Ho, PhD, is a biomedical research physiologist at Tripler Army Medical Center. The views expressed in this blog post are those of the author and do not reflect the official policy or position of the U.S. Department of the Army, U.S. Department of Defense or the U.S. government.

Why Does Air Pollution Affect More Women than Men?

Los Angeles Smog

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A year ago, I went to California to participate in a scientific conference. After a couple of days, my mentor and I started to have trouble breathing. As two healthy adults, we wondered why this was happening. I did not know the answer at that time, but I did notice a pattern: Other female colleagues, especially those with asthma, were also struggling to breathe, but not many men were. Our symptoms got better once we left the conference. A research study we later performed in our lab helped us understand what had happened. We discovered some differences in lung function among male and female mice exposed to ozone and other air pollutants, and we learned that females had worse symptoms than males. So something in the air caused our breathing problems.

In the past decade, air pollution has become the world’s single biggest environmental health risk, causing about 7 million deaths—nearly one of every eight—worldwide each year. According to the Air Quality-Life Index, increased air pollution concentration levels may shorten your lifespan by one month if you live in New York and by up to eight months if you live in California. Exposure to pollutants such as ozone, biomass fuels, and fine particles like soot and smoke has been strongly associated with increased mortality from lung disease. As the evidence piles up, we are starting to realize what a big problem these little molecules create—and that what you can’t see can kill you.

Researchers have shown that women are more susceptible to the negative effects of air pollution than men are. The exact reason remains unclear, but we know that men have more relative fat mass, which gives them a larger distribution volume for chemical particles in the environment. Women’s bodies also metabolize pollutants more quickly than men’s, resulting in higher toxicity. A recent study in the American Journal of Physiology—Lung Cellular and Molecular Physiology has shown that sex steroid hormones are somewhat responsible for the male and female differences, indicating that both sex and air pollution may alter the effectiveness of lung immunity.

The American Lung Association offers these and other tips to help protect you from unhealthy air:

  • Check daily air pollution forecasts.
  • Avoid exercising outdoors when pollution levels are high.
  • Avoid exercising near high-traffic areas.
  • Use less energy in your home.
  • Explore other alternatives to driving your car (bike, walk).
  • Don’t burn wood or trash.
  • Don’t allow anyone to smoke indoors.

October 22–28 is Respiratory Care Week. Let’s help the world breathe better. Your life and the lives of your loved ones may depend on it.

Nathalie Fuentes OrtizNathalie Fuentes is a PhD candidate in the biomedical sciences program at Penn State College of Medicine. Her studies in Dr. Patricia Silveyra’s lab include the development of sex-specific therapies to treat lung diseases, sex differences in asthma-related lung inflammation triggered by ground-level ozone and the role of male and female sex hormones in lung disease. Nathalie is originally from Caguas, Puerto Rico.



Out in the Sun? Think about Your Kidneys!

renal colic - male adult - kidney disease


When your body gets overheated, it responds in several ways as it races to cool you back down and prevent serious health problems. Heat stress is when your internal body temperature rises above the normal range of 97 to 99 degrees Fahrenheit. This triggers physiological responses geared toward maintaining normal body temperature. Our internal body temperature is so tightly regulated that an increase of less than 1 degree activates functions such as sweating to cool our body and restore balance. Heat stress can put strain on many areas of the body, including the kidneys. The kidneys transport nutrients throughout and remove waste from your body.

A review published in Comprehensive Physiology evaluated how the cardiovascular system and kidneys respond to heat stress. When your body overheats, your heart pumps more blood, the blood vessels in your organs narrow, and the blood vessels in your skin widen to help decrease the excess heat. While this redistribution of blood to the skin is a positive response to help cool you down, it also decreases blood flow and volume to the kidneys by up to 30 percent. Restricted blood flow reduces the amount of oxygen and nutrients that is delivered to the kidneys. Prolonged exposure to heat stress and decreased blood flow to the kidneys can lead to kidney damage and even kidney failure.

Heat stress can be life-threatening to people who have medical problems that affect body temperature regulation or are otherwise vulnerable to overheating. Seniors, children, people who work outdoors (including military personnel and firefighters) and those who live in parts of the world where it is extremely hot may have an increased risk of heat stress. Some common signs of heat stress include muscle cramps and dehydration. People suffering from heat stress may also experience symptoms of heat exhaustion (pale skin, extreme fatigue, dizziness, heavy sweating, headache and blurred vision) and heat stroke (high body temperature, convulsions, confusion and even unconsciousness). It is important to recognize these signs and get medical help as soon as possible.

The next time you’re out in the hot weather, stay hydrated. Drink water often—even before you get thirsty. The Occupational Safety and Health Administration suggests that outdoor workers drink water every 15 minutes. Finally, limit your sun exposure by taking frequent rest breaks under the shade or inside an air-conditioned building in order to protect your kidneys.

Ijeoma ObiIjeoma Obi, MS, is a PhD candidate in the University of Alabama at Birmingham’s Department of Medicine, Nephrology Division, Section of Cardio-Renal Physiology and Medicine.

Muscle Rebuilding on the Colorado Trail

autumn mountain biking woman

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“That day, for no particular reason, I decided to go for a little run. … For no particular reason I just kept on going. I ran clear to the ocean. And when I got there, I figured, since I’d gone this far, I might as well turn around, just keep on going.” – Forrest Gump

The feats of ultra-endurance athletes are remarkable and sometimes incomprehensible. There are few published data on how the body deals with the stresses of an ultra-endurance event because the fieldwork is difficult to perform without interfering with the athlete’s performance. A new study published in the Journal of Applied Physiology explores how muscle deals with prolonged exercise performed in an “unfriendly” environment (high mileage at high altitude). The primary question these researchers wanted to know: In an event that requires a lot of energy, would the muscles have enough energy to rebuild and adapt to the stress?

The researchers studied a single cyclist during a mountain bike race that spanned 497 miles from Denver to Durango, Colorado, along the high-altitude Colorado Trail. The participant rode 19 to 20 hours each day for five days. The investigators took muscle and blood samples at the beginning and end of the race and compared the changes to a period of normal exercise training.

They found that during the race, the muscles were able to make mitochondria—which are responsible for producing energy in the cells—at an extremely high rate. In addition, the mitochondria increased their ability to use fat energy sources, an important adaptation for long-term exercise. The proteins that contract the muscle also continued to build, but not at a rate fast enough to maintain the muscle’s size, which led to the muscle shrinking in size. In addition, there was significant muscle damage and inflammation. The blood samples also showed evidence of significant stress with changes that were consistent with impaired kidney and liver function.

Overall, this study suggests that when the body is performing an exceptionally, energetically challenging activity, muscle is able to rebuild at an extremely high rate, although maybe not enough, to try to adapt to its new demands. In this case, the extreme stress of the race caused significant muscle damage and organ dysfunction. Scientists hope to continue to find new approaches to study the demands of ultra-endurance athletes to better understand the limits of human performance.


Ben MillerBenjamin Miller, PhD, is an associate professor in the department of Health and Exercise Science at Colorado State University. He co-directs the Translational Research in Aging and Chronic Disease (TRACD) Laboratory with Karyn Hamilton, PhD.

Traumatic Brain Injury: More Than a Kick in the Head

Brain Injury

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Traumatic brain injury (TBI) can be caused by many things, including car accidents, sports injuries, falls, domestic violence and explosions during combat. In the past few years, research has shown American football to be a major contributor to TBI. The media has also highlighted this, especially as iconic athletes speak about their experiences and detrimental effects after they stop playing.

What exactly is traumatic brain injury? The Mayo Clinic defines TBI as an injury that occurs when an external mechanical force—such as a blow to the head—causes the brain to stop functioning normally. Brain injuries are similar in some ways to injuries to other parts of the body that cause limited use of that area. However, TBI is different because it can cause problems throughout the body, such as coma, paralysis or seizures. The potential for widespread damage is perhaps the most devastating aspect of TBI. This kind of injury can alter memory, hand-eye coordination, communication and the ability to multitask. Emotional and social behavior may change so much that a person may not seem like the person they were before the injury.

Advanced imaging techniques—think very high-powered cameras—have made it possible for doctors to see bleeding, bruising, clotting and swelling in the brain. Pairing imaging tests with a physical and neurological examination helps doctors determine the severity of the TBI. These tests measure patients on their ability to listen to and follow directions, move their limbs and form complete thoughts and sentences.

Researchers are just beginning to understand some of the molecular changes that occur following TBI. They know that certain proteins are elevated in the area surrounding the injury and in the blood for a short period after the injury. Because it’s almost impossible to predict an injury or accident that causes TBI, there is no way to prevent this spike in protein levels. However, the development of car airbags, technological advances in sports helmets and mouth guards, teaching of proper tackling techniques in football, and restricting young soccer players from heading the ball have increased our awareness about TBI risk factors and may help more people avoid sustaining these injuries. Hopefully in the future, fewer people will have to live with the challenges of TBI.

Adam MorrowAdam Morrow, PhD, is an assistant professor of biochemistry at the Alabama College of Osteopathic Medicine.