Causes of hypovolemic shock – diarrhea, blood loss, cholera, sweating, not DI (b/c losing pure water,
and not losing Na, total body Na is NORMAL! Losing water from ICF; no signs of dehydration; when
you lose salt, show signs of dehydration).
Example: lady with hypovolemic shock – when she was lying down, her BP and pulse were
normal; when they sat her up, the BP decreased and pulse went up. What does this indicate?
That she is volume depleted. This is called the TILT test. Normal BP when lying down b/c there is
no effective gravity, therefore normal blood returning to the right side of the heart, and normal
CO. However, when you sit the patient up, and impose gravity, you decrease the venous return
to right heart. So, if you are hypovolemic, it will show up by a decrease in BP and an increase in
Cardiac output is decreased, and the catecholamine effect causes this scenario. How would you
Rx? Normal saline.
Example: pt collapses, and you do a tilt test: 100/80 and pulse of 120 while lying down. Sitting
up, it was 70/60 and pulse of 150. The pt is severely hypovolemic, therefore Rx is normal saline.
Treatment: One liter in, showed no signs, put another liter and the BP becomes normal, and is
feeling better, but still signs of volume depletion (dry mouth). We have the BP stabilized, but
the pt lost hypotonic salt solution, therefore we need to replace this. So on IV, give hypotonic
salt sol’n (b/c was losing hypotonic salt solution). We do not give 5% dextrose and water b/c
there’s not any salt in it. Therefore, we will give ½ normal saline. The treatment protocol is:
when a pt loses something, you replace what they lost. And when pt is hypovolemic, always
give isotonic saline.
Example: DKA, have osmotic diuresis; tonicity of fluid in the urine that has excess glucose is
hypotonic. Hypotonic fluid has a little more fluid than salt. So the pt is severely hypovolemic;
therefore the first step in management is correction of volume depletion. Some people are in
hypovolemic shock from all that salt and water loss. Therefore need to correct hypovolemia
and then correct the blood sugar levels (DKA pts lose hypotonic solution). Therefore, first step
for DKA pt is to give normal saline b/c you want to make them normo-tensive. Do not put the pt
on insulin b/c it’s worthless unless you correct the hypovolemia. It can take 6-8 liters of isotonic
saline before the blood pressure starts to stabilize. After pt is feeling better and the pt is fine
volume wise. Now what are we going to do? The pt is still losing more water than salt in urine,
therefore still losing a hypotonic salt solution, therefore need to hang up an IV with ½ normal
saline (ie the ratio of solutes to water) and insulin (b/c the pt is loosing glucose).
So, first thing to do always in a pt with hypovolemic shock is normal saline, to get the BP normal.
Then to correct the problem that caused the hypovolemia. It depends on what is causing the
hypovolemia (ie if pt is sweating, give hypotonic salt solution, if diarrhea in an adult give isotonic
salt sol’n (ie normal saline), if pt with DI (ie stable BP, pt is lucid) give water (they are losing
water, therefore give 5% dextrose (ie 50% glucose) and water).
Four kinds of shock:
1. Hypovolemic shock: blood loss, diarrhea (adult or child), basically whenever you are lose salt,
you could end up with hypovolemic shock 2. Cardiogenic shock: MC due to MI
3. Neurogenic shock: assoc. with spinal cord injuries
4. Septic shock: MC due to E. coli; also MCC sepsis in hospital and is due to an indwelling of the
urinary catheter. Staph aureus is not the MC cause of IV related septicemia in the hospital,
E.Coli wins hands down. Endotoxin in cell wall is a lipopolysacharide, which are seen in gram
negative bacteria. The lipids are endotoxins. Therefore, gram negatives have lipids (endotoxins)
in their cell wall, gram positive do not. SO if you have E.Coli sepsis, you will have big time
problems, and is called septic shock.
5. Classical clinical presentations:
a) Hypovolemic and cardiogenic shock: you would see cold and clammy skin, b/c of
vasoconstriction of the peripheral vessels by catecholamines (release is due to the decrease
in SV and CO) and AG II. These will vasoconstrict the skin and redirect the blood flow to
other important organs in the body like brain and kidneys, leading to a cold clammy skin. BP
is decreased, pulse is increased.
b) Pouseau’s laws: is a concept that teaches you about peripheral resistance of arterioles
which control the diastolic blood pressure.
TPR = V/r 4
TPR = Total peripheral resistance of the arterioles
V = Viscosity
r = radius of the vessel to the 4 power
The main factor controlling TPR is radius to the 4 power
What controls the viscosity in the blood? Hb. So if you are anemic, viscosity of blood is
decreased (ie low hemoglobin), and if you have polycythemia (high hemoglobin), viscosity
will be increased. Therefore, TPR in anemia will decrease, and in polycythemia will increase.
c) Septic shock – There is a release of endotoxins which activates the alternative
complement system. The complement will eventually release C3a and C5a which are
anaphylatoxins, which will stimulate the mast cells to release histamine. The histamine
causes vasodilation of arterioles (the same ones of the peripheral resistance arterioles).
Therefore blood flow is increased throughout the