A simple conception of shock is this. Think of the body as nothing more than a self contained hydraulic system, with the heart as the pump at the center of it all. The arteries and veins are the tubes and pipes through which the hydraulic fluid passes to the many and varied apparatuses attached to the system. Each apparatus (kidney, liver, brain, etc.) relies in its entirety on the delivery of this vital hydraulic fluid (the blood).
It is a useful exercise to assume that the size of the tank (the size of the pipes) is fixed. This means that any disturbance which either lessens the amount of fluid circulating in this fixed system (a cut or laceration perhaps) or any derangement of the pump itself (a heart attack maybe) will lessen the amount of fluid getting to those far flung apparatuses (the end organs in med speak).
Shock is defined as a lack of perfusion to those vital end organs.
What can cause it?
There are exactly three ways in which the system can be deranged: pump failure (the heart is not working well); loss of fluid from the system (bleeding); or the size of the tank suddenly increases or decreases in size (turns out the size of those tubes and pipes is NOT fixed; think of this as valves opening and closing that change the size of the tank).
1. Loss of fluid — We got a bleeder!
Laceration. This is simply a cut in the skin and underlying tissue. The rate of bleeding is important, because the body will try to compensate by opening and closing those valves we discussed above. This will be successful if the rate of bleeding is slow enough to be controlled and/or ceases before the critical level at which compensation is no longer possible. Veins bleed slowly and might clot before there is much trouble. Think of a torn jugular vein, which is rarely fatal.
Arteries bleed fast, and with a pumping rhythm. You can tell an artery has been opened because the blood spurts out with each heartbeat. A bleeding vein oozes without this effect. So your beleaguered subject will bleed out fast if you cut the carotid, or a bullet punctures the aorta. A lacerated spleen (which is essentially a huge sponge of blood) might go either way, depending on how badly it is ruptured. You could make this fit any scenario from hours to days or a week or more. A patient would have vague pain from the ruptured spleen, but not necessarily enough to seek medical attention. They might suddenly collapse and die a week after the accident.
All of this is why docs immediately establish an IV on an accident victim and start giving him or her fluid. It is more important to provide fluid of any sort than wait and give only a blood transfusion (in fact, blood transfusion is avoided except in the worst cases; the blood replenishes itself in a matter of days and keeping the volume of fluid up with sugar and salt water (saline solutions; D5NS or D5 half normal are some of the medical terms)).
2. Pump failure — Jesus Christ. The knife’s in her heart. She’s a dead woman.
This is heart failure folks. It can be sudden (heart attack, tension pneumothorax (collapsed lung), a gun shot wound that passes through the heart (which would also be a type of laceration and so the shock has two causes and both need treatment!).
But the failure can also be slow. The is chronic or congestive heart failure. There are many causes of this: pulmonary hypertension, multiple small heart attacks, viral or bacterial infection of the heart muscle, disease of the heart valves making them incompetent, congenital heart disease in which the heart is not formed correctly and slowly fails. There are many drugs that can treat this to some extent; sometimes surgery will help (say with a tumor growing inside the heart and preventing it from filling with blood).
3. The size of the tank. Pressure’s dropping like a rock. Fluid, he needs fluid, god damit!
The big one here is septic shock. In this instance, the body pumps out humors to treat the infection, but these humors essentially poison the pump system and it opens wide (collapses altogether in some cases). The effective treatment is two fold: treat the infection, if possible (antibiotics, antiviral agents); and add volume (the saline solutions we discussed earlier). This is a race against time; if you win, you’re patient survives; if not, well…
Remember also, it is not always about survival, but about quality of survival. If shock goes on long enough and is then effectively treated, the end organs may still have been damaged by the lack of enough blood flow. This could be brain damage (coma, vegetative state, or a prolonged but incomplete recovery with reduced cognitive capacity (he just doesn’t think as well as he did before the accident!)); chronic kidney disease; heart failure because the heart wasn’t being adequately perfused during the shock and the patient had a small heart attack. There are many other scenarios (a not uncommon one is paraplegia because the thoracic spinal cord stroked during the period of shock; you patient is now paralyzed with some reasonable hope of recovery; use this if you need a subject to be paralyzed for a period of time—days to months—and then recover.
Younger people handle shock better than older people. Think of this as sludge building up within the system. If the pressure inside it drops, more of the fluid (blood) will get through if the pipes are not relatively clogged with sludge (atherosclerosis). A rule to remember: old people carry more baggage with them and generally have a more difficult and fraught time in any medical scenario. If you need a character to recover well, or fast, or completely, make him or her young, under thirty perhaps.
That’s just under 1000 words right there folks. Enough about shock. Now go out there and stab, shoot, cut, poke, prod, and scalp your characters. Have fun.
For a thrilling tale about shock, read JUICING OUT by Edison McDaniels. Click the book cover for a sample.
Edison McDaniels is a graduate of Stanford, a brain surgeon, and writes intense medical fiction and supernatural medical thrillers. Visit him on the web at SurgicalFiction.com, check out THE SURGICAL FICTION PODCAST on your favorite podcast app, or contact him with a question about writing medical fiction through the contact page.