Dear Science,
A few weeks ago, I saw a picture of a cyclist smashed under an SUV in West Seattle—dragged 50 feet and seemingly mashed into a paste. He apparently lived. That's somewhat amazing to me. What happens to someone dragged under a car for several city blocks? What do they do to people at Harborview Medical Center that they can eventually go home?
Marveled At Medicine
Barring instant death—evisceration (in which a quorum of internal organs become external and inoperative), obliteration of the brain (or the totality of the body, such as in an explosion), and the ilk—after trauma, we typically die of bleeding and shock. Your blood and beating heart have a primary goal of getting enough oxygen and fuel to all of your body's tissues, as well as clearing away the wastes with some efficiency. Blood pressure generated by the heart pushes the blood through the circuit of arteries, capillaries, and veins back to the heart. Shock sets in when this circuit of blood starts to peter out, due to the pump failing (heart failure), the pipes stretching out, or massive blood loss. With too little blood flow, tissues (and eventually you) start dying. (Bleeding into your head is also a bad idea. The neurosurgeons have drills to fix that.)
To understand blood loss, we visit Dr. Alfred Blalock and Vivien Thomas. When at Vanderbilt University, these pioneers in surgical science bled experimental animals—re-creating the conditions of hemorrhagic shock in the lab. A human being contains about four liters of blood. One can lose up to 15 percent of that before even really noticing it. From 15 to 30 percent, you start feeling pretty miserable. Lose more than a third of your blood, and things start getting dicey. A person can lose a dangerous amount of blood in a handful of ways: through a laceration on their head, or internally into their chest, abdomen, pelvis, or thigh. Between WWI and WWII, Blalock and Thomas came up with the basic game plan that doctors still use today: If the body is lacking blood, replace it. Use blood if it's available. If not, use salt water matched to the tonicity of blood. Give it early, often, and in good chunks. When you come into Harborview bleeding, you can expect to get two liters right off the bat.
Much of what happens to someone as they roll into a trauma center is turned into routine. (This is for the best; surgeons aren't renowned for their thoughtfulness.) Your airway is secured (typically by sticking a tube down your throat to your lungs). Your breathing is done by a machine. Your circulation is supported by those liters of fluid or blood. Once that's completed, you're stripped naked. Sources of bleeding are discovered by physical exam, ultrasound, and CT scan. And then you're off to the operating room to plug up the bleeds.
Circulatingly Yours,
Science
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