Hello Googoo21,
"In Stage I of shock, when low blood flow (perfusion) is first
detected, a number of systems are activated in order to
maintain/restore perfusion. The result is that the heart beats faster,
the blood vessels throughout the body become slightly smaller in
diameter, and the kidney works to retain fluid in the circulatory
system. All this serves to maximize blood flow to the most important
organs and systems in the body. The patient in this stage of shock has
very few symptoms, and treatment can completely halt any progression.
In Stage II of shock, these methods of compensation begin to fail. The
systems of the body are unable to improve perfusion any longer, and
the patient's symptoms reflect that fact. Oxygen deprivation in the
brain causes the patient to become confused and disoriented, while
oxygen deprivation in the heart may cause chest pain. With quick and
appropriate treatment, this stage of shock can be reversed.
In Stage III of shock, the length of time that poor perfusion has
existed begins to take a permanent toll on the body's organs and
tissues. The heart's functioning continues to spiral downward, and the
kidneys usually shut down completely. Cells in organs and tissues
throughout the body are injured and dying. The endpoint of Stage III
shock is the patient's death."
http://www.healthatoz.com/healthatoz/Atoz/ency/shock.jsp
"The human body responds to acute hemorrhage by activating 4 major
physiologic systems: the hematologic, cardiovascular, renal, and
neuroendocrine systems.
The hematologic system responds to an acute severe blood loss by
activating the coagulation cascade and contracting the bleeding
vessels (by means of local thromboxane A2 release). In addition,
platelets are activated (also by means of local thromboxane A2
release) and form an immature clot on the bleeding source. The damaged
vessel exposes collagen, which subsequently causes fibrin deposition
and stabilization of the clot. Approximately 24 hours are needed for
complete clot fibrination and mature formation.
The cardiovascular system initially responds to hypovolemic shock by
increasing the heart rate, increasing myocardial contractility, and
constricting peripheral blood vessels. This response occurs secondary
to an increased release of norepinephrine and decreased baseline vagal
tone (regulated by the baroreceptors in the carotid arch, aortic arch,
left atrium, and pulmonary vessels). The cardiovascular system also
responds by redistributing blood to the brain, heart, and kidneys and
away from skin, muscle, and GI tract.
The renal system responds to hemorrhagic shock by stimulating an
increase in renin secretion from the juxtaglomerular apparatus. Renin
converts angiotensinogen to angiotensin I, which subsequently is
converted to angiotensin II by the lungs and liver. Angiotensin II has
2 main effects, both of which help to reverse hemorrhagic shock,
vasoconstriction of arteriolar smooth muscle, and stimulation of
aldosterone secretion by the adrenal cortex. Aldosterone is
responsible for active sodium reabsorption and subsequent water
conservation.
The neuroendocrine system responds to hemorrhagic shock by causing an
increase in circulating antidiuretic hormone (ADH). ADH is released
from the posterior pituitary gland in response to a decrease in BP (as
detected by baroreceptors) and a decrease in the sodium concentration
(as detected by osmoreceptors). ADH indirectly leads to an increased
reabsorption of water and salt (NaCl) by the distal tubule, the
collecting ducts, and the loop of Henle.
The pathophysiology of hypovolemic shock is much more involved than
what was just listed. To explore the pathophysiology in more detail,
references for further reading are provided in the bibliography. These
intricate mechanisms list above are effective in maintaining vital
organ perfusion in severe blood loss. Without fluid and blood
resuscitation and/or correction of the underlying pathology causing
the hemorrhage, cardiac perfusion eventually diminishes, and multiple
organ failure soon follows."
http://www.emedicine.com/emerg/topic532.htm
"... But in some instances, low blood pressure can be a sign of
serious, even life-threatening disorders. And although the reason for
lower than normal blood pressure isn't always clear, doctors know that
the following factors can cause or contribute to low and sometimes to
dangerously low readings:
* Pregnancy. Because a woman's circulatory system expands rapidly
during pregnancy, blood pressure is likely to drop. In fact, during
the first 24 weeks of pregnancy, systolic pressure commonly drops by
five to 10 points and diastolic pressure by as much as 10 to 15
points.
* Medications. A number of drugs can cause low blood pressure,
including diuretics and other drugs that treat hypertension; heart
medications such as beta blockers; drugs for Parkinson's disease;
tricyclic antidepressants; Viagra, particularly in combination with
nitroglycerine; narcotics, and alcohol. Other prescription and
over-the-counter medications may cause low blood pressure when taken
in combination with high blood pressure drugs.
* Heart problems. Among the heart conditions that can lead to low
blood pressure are an extremely low heart rate (bradycardia), problems
with heart valves, heart attack and heart failure. These are
conditions in which your heart may not be able to circulate enough
blood to meet your body's needs.
* Endocrine problems. These include an underactive or overactive
thyroid (hypothyroidism and hyperthyroidism), adrenal insufficiency
(Addison's disease) low blood sugar and in some cases, diabetes.
* Dehydration. Fever, vomiting, severe diarrhea, overuse of
diuretics, and strenuous exercise can all lead to dehydration, a
potentially serious condition in which your body loses more water than
you take in. Even mild dehydration, a loss of as little as 1 percent
to 2 percent of body weight, can cause weakness, dizziness and
fatigue. Far more serious is hypovolemic shock, a life-threatening
complication of dehydration. It occurs when low blood volume causes a
sudden drop in blood pressure and a corresponding reduction in the
amount of oxygen reaching your tissues. If untreated, severe
hypovolemic shock can cause death within a few minutes or hours.
* Blood loss. A significant loss of blood from major trauma or
severe internal bleeding reduces blood volume, leading to a severe
drop in blood pressure."
http://www.mayoclinic.com/health/low-blood-pressure/DS00590/DSECTION=3&
"Symptoms
The most common symptoms of shock include:
* a fast, weak pulse
* low blood pressure
* feeling faint, weak or nauseous
* dizziness
* cold, clammy skin
* rapid, shallow breathing
* blueness of lips."
Simply put, the body will try to conserve blood and other body fluids
by dropping blood pressure, slowing blood filtering by the kidneys,
slowing the heartbeat, keeping blood closer to vitsal organs. This is
why lips and fingers turn blue. The vessels contract so less blood
volume travels to distal parts of the body.
http://www.bbc.co.uk/health/conditions/shock1.shtml#physiological_(circulatory)_shock
Other useful links:
http://www.nlm.nih.gov/medlineplus/ency/article/000668.htm
http://www.paracademy.com/edprogrm/ema2_courses/pr_hypovolemia.html
http://www.med.uiuc.edu/m2/Pathology/FLUID.htm
I hope this has explained your question! If not, please request an
Answer Clarification, before you rate. I will be glad to respond to
this question.
Regards, Crabcakes
Search Terms
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Hypovolemia + cardiovascular system
septic shock + blood loss |
