bleeding is one of the most challenging things to teach. There is so much instinctive
emotion associated with bleeding that separating the objective nature of the
injury from the emotional reaction is difficult to do.
as medicine has advanced over the centuries, one of the most elusive solutions
continues to be bleeding control in both the field and in the hospital.
Advances have been slow in coming and limited at best. In the end, the
principles of bleeding are similar and related to the laws of physics and
cannot be changed. We must work with them in order to come up with solutions.
is all about 1) plumbing and the principles of fluids and flow; and 2) the
physiology of blood and clotting.
Think Pipes and Plumbing
in the human body is moved around by a series of pipes. There are feeds (inflow)
and returns (outflow). Inflow is maintained by arteries and outflow is achieved
by veins. The ultimate reason this
complex series of pipes exists is to provide blood, rich in oxygen, via the
inflow, to the cells in your body that need it. Second, the outflow exists in
order to remove the oxygen depleted and carbon dioxide-rich blood from those
same areas. It is that simple.
pipe system, there are large main pipes, such as the aorta for inflow and the
vena cava for outflow. Both connect directly to the heart, which is the
circulating pump. The aorta and vena cava break off into moderate size vessels
and eventually small ones similar to a tree’s branches. The main arteries and
veins frequently run together but when they branch into smaller networks, they
take separate paths, again, mimicking a tree with small terminal branches and
end, it is a loop. Blood arrives via the arteries and leaves via the veins.
Typically, if the pipe or vessel has a name, it is significant in both importance
and in size.
Pipes Are Protected
human body was designed with a remarkable resilience and with some amazing
protective mechanisms. It is no accident of nature that all your important
pipes of any significant size run deep in the core, along the bony skeleton and
are thus protected. The bigger the pipe, the deeper and more protected it
for example, your aorta and vena cava. These are the largest blood vessels in
the body. They run together in the deepest most protected part of your core. They
run along the front of your spine so they are protected from the back by the
bones of your spine. In the front, they are exposed but still reside deep in
the torso with layers of fat, muscle, intestine, bone and lung providing
shielding. In the end, it is very difficult to get to any of those pipes.
comes to the extremities such as your arms and legs, again, these pipes are
protected by fat and muscle on the exposed sides and by the bones on the
backsides. There is one significant piping
exception. In the upper arms and thighs, we have only one moderately large pipe
from the torso to the elbow and knee. In the arm, this is the brachial artery,
and in the leg this is the superficial femoral artery.
there are some early branches that feed the upper arms and legs, for the most
part, this exposed segment of the piping highway is devoid of branches and is
the only road in for the lower arm and leg.
get to the elbow and knee, these moderately large pipes divide into three
separate tubes, so if one is taken out, the others will compensate and the limb
will not be lost. It is only in the thigh and upper arm that one single pipe
exists and hence this is the vulnerable area as it relates to limb survival,
should it be injured. Even the head has four pipes in and four pipes out, so if
one set is injured, the others will be able to compensate.
High and Low Pressure
other important blood flow concept is that blood pressure varies by blood
vessel. Arteries are high pressure pipes. They are designed with a thick wall
to contain the pressure of the blood flowing through them. Your body uses the
muscles within the walls of the arteries to contract and expand in order to
adjust pressure throughout the system as necessary. The veins, on the other
hand, are a very low-pressure system since they are only transporting the
returning blood which is now far down system and far away from the pump (the
inflow is a high-pressure system and the outflow is a low-pressure system. That
translates to the fact that pressure to shut down any given pipe depends on
what type of pipe it is. If you are trying to shut down or even decrease flow
to an inflow pipe such as an artery, you need to apply significantly more
external pressure than if you were trying to shut down or slow flow to an
outflow pipe such as a vein.
example, if you lacerated a superficial vein on the top of your hand, it may
appear to bleed significantly, especially if it is a big vein; however, a small
amount of pressure over the vein will stop blood flow completely.
from the principles of blood and clotting, there are other simultaneous safety mechanisms
that come into play. One such example is spasm of the vessels. When a pipe is
injured, specifically an inflow pipe such as an artery, the muscle fibers
within the wall of the pipe contract and shrink the tube’s diameter
significantly. This dramatically slows the flow of the blood moving through it,
allowing the protective mechanisms of the blood itself to work, i.e., the blood
triggers cause blood to clot. In this case, a decrease in the speed of
movement, i.e., a decrease in flow and also a disruption in the evenness of
flow. When the inner layers of the blood vessels are injured, they release
chemicals that direct blood to clot. So,
when an injury to a pipe exists, your body shrinks the pipe to slow the flow
and the vessel releases chemical triggers that initiate a clot to form.
clot forms, bleeding stops and the life is potentially saved. This too is where
pressure comes in. Keeping the principles of blood clotting in mind, when
external pressure is applied on a bleeding injury, the pipe is being collapsed,
thus slowing the flow and allowing for a clot to form so bleeding will stop. Again,
we are simply working with the body’s protective mechanisms.
How Much Blood Loss?
body has about 5 liters of blood. Of those 5 liters, how much can you lose and
still survive? The answer is not exact, especially since estimating the amount
of loss is very difficult.
blood loss in perspective, when you donate blood you typically give up about a
half a liter of blood. For some, this is significant and can make them dizzy,
while for most others this will be unnoticeable. In the end, any blood loss is
not a good thing, but certainly there are tolerable limits.
The American College of Surgeons offers guidance on
this by breaking blood loss into four categories. Class 1 is a loss of less
than 15 percent of the blood volume. Typically few people feel the effects and
this would be similar to donating blood.
is a loss of 15-30 percent of blood. Here most people will show some of the protective
mechanisms kicking in. We typically see an elevation in heart rate, maybe some
loss of skin color, as they may look a little pale. Some may demonstrate
dizziness, especially if they are standing up where the heart must work harder
to overcome gravity to pump blood to the brain. Typically, however, in class 2
blood loss, the blood pressure is maintained.
reach Class 3 hemorrhage, we have lost greater than 30 percent of our blood
volume, and our protective mechanisms of compensation such as heart rate and
lying down, are barely able to keep up. We begin to see drops in blood
pressure. This frequently results in some deprivation of oxygen to the brain
and thus some confusion may occur.
here we see the body attempt to protect itself. As the blood pressure falls,
the flow through the bleeding vessel is hopefully decreased, thus enhancing the
chance for a blood clot to take form. The temporary treatment for this is to
have the individual lie down, keep him/her as warm as possible, raise the feet,
and begin replacement of the blood loss with fluid and human blood products as
soon as possible.
4 hemorrhage, we have lost greater than 40 percent of our blood volume and we
have exceeded our body’s ability to compensate. Emergent aggressive
intervention with blood, fluids and surgery are typically required.
Survival on the Street
these percentages in mind and how they relate to survival, how do we translate
this to actual practice for the officer on the street? Here is where the
disconnect occurs. How can you estimate a 15 percent blood loss from a 30
percent blood loss? In times of stress, don’t attempt to evaluate the victim’s
heart rate. This will ultimately have little value, especially without a
baseline reference point.
answer is two-fold. First, the goal is not to allow such blood loss in the
first place. So prevention and early
intervention is key. Second, if we arrive late and blood loss has already
occurred, this is where simple treatment methods become universal. The
universal answer is to apply a countermeasure to stop bleeding and to divert as
much blood from other parts of the body to the heart and brain.
equal importance is the need to preserve body warmth. A loss in temperature
prevents blood from clotting, thus causing one to bleed faster and more
extensively. All of this can be accomplished by lying the individual down,
calming him/her, raising the legs, and covering him/her with a blanket or
Blood Loss Intervention
ongoing blood loss and choosing the correct intervention is difficult to teach
for two reasons. First, the sheer emotion to all involved with bleeding. Second,
the lack of reference as to what is severe bleeding and what is not.
we must teach to the most universal solution as everyone’s points of reference
and levels of experience differ. However, I am a big proponent of teaching, not
so much the details in the technique, but in teaching to the final intended
result. It is not always the “means” to the end that matters so much, as it is
the “end” result itself.
case of bleeding, I would rather everyone be able to achieve complete cessation
of bleeding and not worry so much as to how you got there. So, in an effort to
do just that, it is important to understand just a little anatomy and the
associated principles of bleeding so that one’s decisions can be best
yourself this question when looking at a bleeding wound. Is it compressible,
that is, will local direct pressure work? This is certainly the case with
extremity injuries, injuries to the head and scalp, and some neck injuries. All
soft tissue injuries, even in the torso should be amendable to external
injuries to the trunk and core that we must recognize our limitations. Because
these large pipes run deep in the core, essentially within cavities that can
accommodate large amounts of blood without showing signs to the exterior, we
must have respect and be able to recognize them.
is little we can do in the field for such injuries other than simple
countermeasures for shock, i.e., raising the legs, lying down, and keeping
warm. The next most important thing that one can do is to get the person to
definitive care as quickly as possible.
Two Pressure Levels
deep penetrating and blunt torso injuries, extremity injuries and soft-tissue
injuries should be able to be managed in the field to a definitive end—the
cessation of active bleeding. All such injuries will subscribe to the concepts
of pressure, recognizing that there are extremes of pressure. Keeping in mind
what you are trying to achieve, it is critical to choose the method that suits
the moment and the injury.
dynamic tactical moment where fighting is still occurring or the area of
operation is hostile may dictate different countermeasures than a safe covered
area. Tactics should come first as good tactics are the best medicine.
the two different levels of pressure. Depending on the injury, the type of
pressure is the next step in solving the bleeding problem. If we base our
response on what is most common, then we should recognize direct injury to a
large artery is possible, but due to its protected positioning, it is
common is the injury of smaller arteries and veins within muscles and soft
tissues. These can appear to be significant, and certainly can be, but because
they are more often than not, very amendable to compression, the use of some
form of moderate pressure will often suffice.
cases, this pressure can be accomplished by a wide circumferential pressure
dressing or by simple firm, direct pressure. If there is significant tissue
loss and a large cavity, then filling the space with gauze or some other
material will allow the superficial pressure from the wound surface to be
directed downward into the depths of the wound, thus achieving the necessary
result. This is known as wound packing.
will be occasion where moderate pressure either circumferential or direct is
not enough to stop bleeding. This should signal a deeper, more significant
injury to a larger pipe. Although not very common, these injuries do exist and
we should all be prepared to address them. This is where a circumferential
pressure dressing with a pressure bar can be of great assistance. This allows
one to convert moderate pressure to greater extremes partially or totally
shutting off inflow from the deep pipe/artery and thus allowing a clot to set
however, this is still insufficient, then the next step would be a tourniquet.
The definition of tourniquet is a device intended to “stop” blood flow both in
and out. Recognize even moderate pressure
will stop outflow but preserve inflow. A tourniquet is essentially a shut-off
valve placed above the point of injury, but close to it. It will completely
shut down flow to the limb from the point it is placed.
extreme measure is very useful where limb loss has already occurred and there
exists an open-ended vessel or where there is clear bright red, fountain-like
high-pressure bleeding occurring in large volumes, such as one could anticipate
liters of blood loss in a short period of time.
mind, the placement of a tourniquet is extremely painful. It hurts terribly at
the place it is applied simply by compressing the skin and tissues beneath it. It
also causes extreme pain downstream from where it has shut off the blood flow
as tissues deprived of oxygen are very painful.
application of a tourniquet frequently demands medication to modify the
significant associated pain. If it does not hurt to an extreme, then it is likely
not applied tight enough. If that is the case and bleeding has been stopped,
one should consider re-evaluating the actual need for a tourniquet.
important to understand that tourniquets have saved thousands of lives in the
military. However, the injury patterns associated with such saves are
frequently limb loss or limb destruction in the field and the extreme has been
reached. Also, even the applications in the military are frequently applied too
loose or the device was not needed.
advice to all who carry tourniquets, and I think we should all have them, is to
be able to articulate in clear and certain terms the reasons behind its uses
should you ever choose to apply it in the street.
about hemostatic agents? This is a commonly asked question and in my mind, the
answer is relatively straightforward and simple. In the end, if a hemostatic
agent is applied and it required nothing else, then the bleeding was quite
insignificant and probably did not warrant even the application of the
when it comes to these products, they must be thought of as adjuncts to the
means to the end. No hemostatic agent alone can stop significant bleeding. All
must be coupled with pressure and the principles of flow and blood clotting. When
applied in conjunction to pressure, then the product can certainly accelerate
clotting and thus slow and stop bleeding. Such agents work great as the
material used to pack deep wounds and when combined with surface pressure, the
results are commonly favorable.
end, bleeding is just plumbing. It subscribes to the same rules of physics as
any fluid flowing through pipes with the added benefit of blood’s ability to
clot. If one understands the associated principles and that all the techniques
from pressure to tourniquets are simply variations of pressure intended to
achieve the same end, then one’s decisions can be best fortified so as to
achieve the desired outcome.
Dr. Andrew Dennis is a trauma & burn
surgeon at the Cook County Trauma & Burn Unit in Chicago. He is a police
officer and Director of Medical Operations for the Cook County Sheriff’s Office
and the Northern Illinois Police Alarm System. Dr. Dennis is the CEO of
Leomedicus and the developer of the Medical Tactics for Law Enforcement
program. He is the author of the recently published and acclaimed book Officer
Down, a Practical Tactical Guide to Surviving Injury in the Street. He can be reached at firstname.lastname@example.org