lowered, the peripheral pulse may be ab-
sent. The pulse rate in hemorrhagic shock
may reach 140 or higher. An exception is
neurogenic shock, where the pulse rate is
slowed, often below 60.
7. The blood pressure is usually lowered in
moderately severe shock; the systolic
pressure drops below 100 while the pulse
rises above 100. The body is compensating
for circulatory fluid loss by peripheral
vasoconstriction. This process tends to
maintain the blood pressure at nearly a
normal level despite moderately severe
loss of circulating blood volume. A point
comes, however, when decompensation
occurs, and a small additional loss will
then produce an alarming and sudden fall
in blood pressure.
8. There may be nausea, vomiting, and
dryness of the mouth, lips, and tongue.
9. Surface veins may collapse. Veins nor-
mally visible at the front of the elbow,
forearms, and the back of the hands will
be hard to distinguish.
10. There are frequent complaints of thirst.
Even the severely wounded may complain
of thirst rather than pain.
11. The kidneys may shut down. Urine for-
mation either ceases or becomes greatly
diminished if the systolic blood pressure
falls below 80 for long periods of time.
12. The person may faint from inadequate
venous blood return to the heart. This
may be the result of a temporary gravita-
tional pooling of the blood associated
with standing up too quickly.
This condition is also known as oligemic or
hematogenic shock. The essential feature of all
forms of hypovolemic shock is loss of fluid from
the circulating blood volume, so that adequate cir-
culation cannot be maintained to all parts of the
In cases where there is internal or external
hemorrhage due to trauma (hemorrhagic shock)
there is a loss of whole blood, including red blood
cells. The body tends to restore the circulatory
volume by supplying fluid from the body tissues.
There is a resulting progressive fall in the hemato-
crit (ratio of red blood cells to plasma) and in the
red blood cell count due to hemodilution,
However, since hemodilution is not an excessively
rapid process, the hematocrit is a poor indicator
of acute blood loss, i.e., less than 24 hours old,
In burn shock, on the other hand, there is a
progressively increased hematocrit and red blood
cell count due to hemoconcentration from loss of
the plasma fraction of the blood into and through
the burned area.
A third form of hypovolemic shock occurs in
cases of severe diarrhea and vomiting, where body
fluids and electrolytes (sodium, potassium, and
chloride) are lost. This also contributes to a
decrease in circulating blood volume.
Neurogenic shock, sometimes called vasogenic
shock, results from the disruption of autonomic
nervous system control over vasoconstriction.
Under normal conditions the autonomic nervous
system keeps the muscles of the veins and arteries
partially contracted. At the onset of most forms
further constriction is signaled.
However, the vascular muscles cannot maintain
this contraction indefinitely. A number of factors,
including increased fluid loss, central nervous
system trauma, or emotional shock, can override
the autonomic nervous system control. The veins
and arteries immediately dilate, drastically ex-
panding the volume of the circulatory system,
with a corresponding reduction of blood pressure.
Simple fainting (syncope) is a variation of
neurogenic shock. It often is the result of a tempo-
rary gravitational pooling of the blood as a per-
son stands up. As the person falls, blood again
rushes to the head, and the problem is solved. It
may also be induced by fear or horror, which
override the autonomic nervous system control.
Other variations of neurogenic shock that are
important to the corpsman are shell shock and
bomb shock. These are psychological adjustment
reactions to extremely stressful wartime expe-
riences and do not relate to the collapse of the
cardiovascular system. Symptoms range from in-
tense fear to complete dementia and are
manifestations of a loss of nervous control. Care
is limited to emotional support and evacuation to
the care of a psychiatrist or psychologist.
Cardiogenic shock is caused by inadequate
functioning of the heart, not by loss of circulating
blood volume. If the heart muscle is weakened by
disease or damaged by trauma or lack of oxygen,
as in cases of pulmonary disease, suffocation, or