Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
Medical Author: Benjamin C. Wedro, MD, FAAEM
Medical Editor: Melissa Conrad Stöppler, MD
The ambulance call comes in.
"We're running lights and siren with a 67 year old male.
He's confused, lethargic, blood pressure 80 over 40, thready pulse (a pulse that
is very fine and barely perceptible) and sweaty. We'll be at your
door in a couple of minutes."
The nurses start setting up the equipment to care for the patient. We've been
through this drill before when someone arrives at the ER with low blood
pressure. I hope it's an easy diagnosis and something that we can treat quickly.
IV's are set up, monitor pads ready. The respiratory tech arrives with her
machines just in case they are needed.
The EMTS unload a man in obvious distress, sweaty, struggling to breathe, and
limp.
"He's had a fever for a couple of days with a
cough. Past history of
COPD, heart problems, and
smokes."
The diagnosis could be easy, but there are a variety of factors that could
be causing this man's condition. He is in
shock; his
blood
pressure is so low there is not
enough pressure to provide blood flow and oxygen to his brain. That's why he is
lethargic. No doubt the rest of his organs are at risk too. But why?
The word shock is used differently by the medical community and the general public. The connotation by the public is an intense emotional reaction to a
stressful situation
or bad news. The medical definition of shock is much different.
Medically, shock is defined as a condition where the tissues in the body don't receive enough oxygen and nutrients to allow the cells to function. This ultimately leads to cellular death, progressing to organ failure, and finally,
if untreated, whole body failure and death.
How the body works
Cells need two things to function: oxygen and glucose. This allows the cells to generate energy and do their specific jobs.
Oxygen in the air enters the body through the lungs; where oxygen molecules cross into the smallest blood vessels, the capillaries, and are picked up by red blood cells and attached to hemoglobin molecules. The red blood cells are pushed through the body by the actions of the pumping heart and deliver the oxygen to cells in all the tissues of the body. The hemoglobin then picks up carbon dioxide, the waste product of metabolism, where it is then taken back to the lungs and breathed
out into the air, whereby the whole cycle begins again.
Glucose is generated in the body from the foods we eat. Glucose travels in the
blood stream and uses an insulin molecule to
"open the door," where it then enters the cell to provide energy for cellular metabolism.
Shock Causes
When things go wrong
If cells are deprived of oxygen, instead of using aerobic (with oxygen) metabolism
to function, the cells use the anaerobic (without oxygen) pathway to produce energy. Unfortunately, lactic acid is formed as
a by product of anaerobic metabolism. This acid changes the acid-base balance in the blood,
making it more acidic, and
this leads to situation in which cells begin to leak toxic chemicals into the bloodstream, causing blood vessel walls to become damaged.
The anaerobic process ultimately leads to the death of the cell. If enough cells die, organs start to fail, and the body
starts to fail and death occurs.
Think of the cardiovascular system of the body as similar to the oil pump in your car. For efficient functioning, the electrical pump needs to work to pump the oil, there needs to be enough oil, and the oil lines need to be intact. If any of these components fail, oil pressure falls and the engine may be damaged. In the body, if the heart, blood vessels, or bloodstream (circulation) fail, then the body fails.
Where things go wrong
The oxygen delivery system to the body's cells can fail in a variety of ways.
The amount of oxygen in the air that is inhaled can be decreased.
Inflammation of the sac around the heart (pericarditis) or inflammation of
the heart muscle due to infections or other causes, in which the effective
beating capabilities of the heart are lost.
There may not be enough red blood cells in the blood. If there aren't enough red blood cells (anemia), then not enough oxygen can be delivered to the tissues with each heart beat.
Examples of causes may include:
inability of the bone marrow to make red blood cells, or
the increased destruction of red blood cells by the body (an example,
sickle cell disease).
There may not be enough other fluids in the blood vessels. The blood stream contains the blood cells (red, white, and platelets), plasma
(which is more than 90% water), and many important proteins and chemicals. Loss of body water or
dehydration can cause shock.
The blood vessels may not be able to maintain enough pressure within their walls to allow blood to be pumped to the rest of the body. Normally, blood vessel walls have tension on them to allow blood to be pumped against gravity to areas above the level of the heart. This tension is under the control of the unconscious central nervous system, balanced between the action of two chemicals,
adrenaline (epinephrine) and acetylcholine. If the adrenaline system fails, then the blood vessel walls dilate and blood pools in the parts of the body closest to the ground
(lower extremities), and may have a difficult time returning to heart to be pumped around the body.
Since one of the steps in the cascade of events causing shock is damage to blood vessel walls, this loss of integrity can cause blood vessels to leak fluid, leading to dehydration which initiates a vicious circle of worsening shock.
An insulin reaction occurs when a person with diabetes becomes confused or
even unconscious because of hypoglycemia (hypo=low + glycol
= sugar + emia = in the
blood) caused by insulin or oral diabetic medications. (Please note that for this article blood sugar and blood glucose mean the same
thing and the terms may be used interchangeably.)
The terms insulin reaction, insulin shock, and hypoglycemia (when associated
with a person with diabetes) are often used interchangeably.
In normal physiology, the body is able to balance the glucose (sugar levels)
in the bloodstream. When a person eats, and glucose levels start to rise, the
body signals the pancreas to secrete insulin. Insulin "unlocks the door" to
cells in the body so that the glucose can be used for energy. When blood sugar
levels drop, insulin production decreases and the liver begins producing
glucose.
