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1/15What Is Hypovolemic Shock: DefinitionHypovolemic shockis an
urgent medical condition, which occurs when a rapid decrease of the
volume ofthe intravascular fluidusually due to severe
bleedingresults in inadequate perfusion of the peripheraltissues
and, eventually, in multiple organ failure .Hemorrhagic shockis
hypovolemic shock caused by bleeding.Typical symptoms and signs:a
person does not look right, is anxious, has pale, cool and sweaty
skinand weak pulse, is lethargic and may lose
consciousness.Treatmentincludes stopping bleeding, intravenous
fluid infusion, oxygen and drugs.Table 1. Hypovolemic shock at a
glance:vital signs and first aid1,438/10/2015 Hypovolemic Shock
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2/15Causes and Risk FactorsThe most common cause of hypovolemic
shock in adults issevere bleeding,and in childrendiarrhea .Causes
ofhypovolemia:Loss of bloodExternal bleeding:penetrating injury,
heavy menstruation, scalp tearGastrointestinal or rectal bleeding
(blood in the stool):Rupture of the esophageal varices (in chronic
alcohol abuse with liver cirrhosis)Esophageal tear due to violent
vomiting, mostly in alcoholics (Mallory-Weiss syndrome)Rupture of
hemorrhoidsAorto-intestinal fistulaBleeding peptic (gastric or
duodenal) ulcer or gastric perforation (stomach cancer) or
MeckelsdiverticulumUlcerative colitisIschemic colitisIntestinal
perforation (for example, in diverticulitis)Iron toxicityColorectal
cancer (after age of 50)Bleeding disorders, such as hemophiliaOther
causes of internal bleeding:Spleen rupture in car/motorbike
accidentsRupture of the aortic aneurysm or aortic dissectionRupture
of hepatic hemangiomaRetroperitoneal bleeding (anticoagulant
therapy with warfarin or heparin in individuals with deepvenous
thrombosis)Fracture of the pelvis or femurHemorrhagic
pancreatitisDisseminated intravascular coagulation (DIC) after
snake bite or in malariaMinor injuries in hemophiliaBleeding during
or after surgeryPregnancy-related bleeding:Ruptured ectopic
pregnancyPlacenta previaPlacental detachment (abruptio
placentae)Uterine ruptureBleeding after deliveryBlood
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3/15Loss of blood plasmaSevere burns affecting >15% skin
surfaceDecreased water intakeWater lossExcessive sweatingRepeated
vomitingSevere diarrhea: gastroenteritis caused by rotavirus in
small children (stomach flu), choleraExcessive urination or
polyuria:Diabetes mellitus , diabetic ketoacidosisDiabetes
insipidusDiureticsSalt-wasting kidney diseases (polycystic kidney
disease)HypercalcemiaEndocrine causes:Severe, acute thyrotoxicosis
(thyroid storm) with high fever, excessive sweating and
diarrheaAcute adrenal insufficiency (adrenal crisis) in acute
Addisons disease with polyuria, vomiting anddiarrheaSecond
spacing:The fluid moves from the blood into the second space (the
space between the cells,which is also called extracellular or
interstitial space) and causes edema:Hyponatremia(a decrease in
osmotic pressure of the blood results in a shift of water from the
bloodinto the body cells)Congestive heart failure (blood pooling in
the venous system and consequent escape of water intothe
interstitial tissue [edema] and a decrease of the blood volume in
the arteries (arterialhypovolemia)In anaphylactic and septic shock,
the permeability of the blood vessels increases, so some
fluidescapes from the blood into the interstitial spaceThird
spacing:Fluid accumulation in the body spaces where normally is no
or only little fluid (theabdominal cavity, retroperitoneal space,
lungs, pleural space, pericardial sac):Aortic dissection (blood
pooling in the newly formed space in the aortic wall)Burns fluid
accumulation in the skin blistersSoft tissue traumaPancreatitis
pancreatic enzymes and cytokines damage the blood vessels what
results in theescape of fluid from the bloodPeritonitisPulmonary
edemaPleural effusionIntestinal obstruction, paralytic ileus,
volvulusA decrease of oncotic pressure of the blood plasma due to
low blood protein levels and2,23232,315
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4/15hypoalbuminemia can result in the escape of fluid from the
blood into the body tissues and cavities:Kidney disease with
nephrotic syndrome with anasarca [generalized edema]Protein
malnutrition [Kwashiorkor]can result in distended bellies in
starving childrenLiver cirrhosis resulting in ascites accumulation
of the fluid in the abdominal cavityProtein losing
enteropathyOvarian hyperstimulation syndromeSickle cell anemia with
splenic sequestration, mostly in young childrenSystemic capillary
leak syndromeNOTE: Many authors use the term third spacing for both
second as third spacing.Differential DiagnosisThere are other types
of shock and other conditions that may resemble hypovolemic
shock:Distributive shockdue to massive vasodilation with an
increase in the volume of the intravascularspace with insufficient
volume of the existing blood to fill this space and therefore a
drop of bloodpressureSeptic shock due to infectionToxic shock
syndrome, mainly in women in which a tampon-associated infection
with staphylococcior streptococci results in vasodilation, high
fever and rash)Anaphylactic shockNeurogenic shock due to spinal
cord injury above Th4 or Th6 (low blood pressure, no
tachycardia,warm skin, paraplegia or tetraplegia, numbnessToxic
shock (poisoning with nitroprusside, bretylium)Cardiogenic shockdue
to heart failure (myocardial infarction, arrhythmia,
cardiomyopathy, heart valvedisease)Obstructive shock:Cardiac
tamponade (muffled heart tones, distended neck veins)Tension
pneumothorax (displaced trachea, decreased breathing sounds on one
side)Hemorrhagic pneumothoraxPulmonary embolismArteriovenous
malformationsVasodilationas a side effect of drugs, such as
barbiturates, nitrates, opiates, antihypertensives (betablockers,
vasodilators)Temporary autonomic dysfunction:Orthostatic
hypotensionVasovagal syncopeThe term relative hypovolemic shock can
be used when the volume of the circulatory system increases
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5/15to vasodilation, for example in neurogenic shock, and the
volume of the blood remains the same butinsufficient to perfuse
peripheral organs.PathophysiologyCompensated ShockShock is
compensated until the cardiac output (CO) and systolic blood
pressure (BP) remain normal and thusmanage to maintain proper
perfusion of peripheral tissues.Baroreceptor reflex.Bleeding or
other cause of fluid loss results in a drop of blood volume and
henceblood pressure, which is detected by baroreceptors in the
aortic and carotid arch. Baroreceptors activatethe sympathetic
systemsympathetic nerves, which release norepinephrine
(noradrenaline) and adrenalmedulla, which releases epinephrine
(adrenaline), which results in the constriction of the
peripheralblood vessels in the skin and increased heart
contractility and heart rate. The brain, heart and kidneyarteries
have an ability of autoregulation, which means they can maintain
adequate blood perfusiondespite a gross reduction of the blood
pressure (systolic BP 60-100 mm Hg). All these changes result inthe
redirection of the blood flow from the skin, muscles and
gastrointestinal tract toward the heart, brainand kidneys.Fluid
retentionAtrial volume receptors sense the drop of the blood volume
and stimulate the release oftheantidiuretic hormone (ADH)from the
pituitary gland, which reduces water excretion throughthe
kidneys.Osmoreceptors in the hypothalamus detect the increase of
blood osmolality and trigger the releaseof the ADH .Decreased
perfusion of the juxtaglomerular apparatus in the kidneys
stimulates renin >> angiotensinI >> angiotensin II and
finallyaldosteronerelease from the adrenal cortex, which causes
theretention of sodium and hence water in the kidneys, which helps
to maintain blood volume.Movement of fluid from intracellular and
interstitial space into the
blood.Bronchodilationandhyperventilationtriggered by increased
sympathetic activity results in increasedoxygen delivery to the
tissues.ReferencesProgressive or Decompensated ShockShock is
decompensated when cardiac output and blood pressure drop to the
point where they can notmaintain proper perfusion of the tissues
any more. This results in decreased oxygen delivery to the
tissuesand switch from aerobic to anaerobic metabolism, which
results in lactate production andlactic acidosis.Irreversible
Shock451,13,23,388/10/2015 Hypovolemic Shock Pathophysiology,
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6/15Shock is irreversible when the damage of the vital organs is so
extensive that death cannot be preventeddespite treatment. The
patient can still survive up to three weeks after the onset of
irreversible shock .Table 2. Stages(Classes, Grades) ofHypovolemic
Shock; Vital SignsCompensated DecompensatedStage 1 Stage 2
Stage3Stage 4Bloodvolumeloss40%(>2,000
mL)(immediatelylifethreatening)2CardiacoutputCompensatedbyconstriction
ofvascular bedLower Lower LowerSystolicbloodpressureNormal Normal
120/min >140/minPulse Normal Weak Weak Weak
orabsentCapillaryrefillNormal (2sec)Delayed(>2
sec)AbsentUrineoutputNormal (>30mL/hour)20-30mL/hour40% blood
loss or brain or heart involvement (coma,
bradycardia)ReferenceEarly/First SymptomsClinical symptoms and
signs may not be present until 10-20% of the total blood volume in
adults or up to 30%in infants is lost.Thirst due to hypovolemia
(hypovolemic thirst) can appear after 15% blood lossNauseaAnxiety,
irritability, agitation, sleepiness, confusionPale, clammy skin
(indehydration, especially inheat stroke, skin is initially dry and
warm)Symptoms of bleeding: vomiting blood (hematemesis), blood in
the stool (melena), blood in the urine,bruising, chest or back pain
(rupture of the thoracic aorta), abdominal orflank pain(rupture of
theabdominal aortic aneurysm, stabbing), vaginal bleeding outside
of menstruation.Early SignsPaleness, excessive sweating
(diaphoresis)NOTE: in heat stroke, the skin would be dry and
warmDilated pupilsIncreased heart rate (tachycardia; may not occur
early in patients who take beta-blockers)Weak, wide pulse,
initially due to increased adrenaline release and subsequent
peripheralvasoconstriction and increased diastolic blood
pressureBlood pressure may not fall until about 20% blood (in
infants 30%) is lost. Older people with high bloodpressure or
atherosclerosis may be in the stage of decompensated shock even if
their blood pressure isat 120 mm Hg or above .Increased breathing
frequency (tachypnea)Capillary refill time (CRT)>2 seconds in
infants, children and adults (CRT in healthy, especially in old
people can beprolonged in cold ambient)>3 sec corresponds to
~10% drop of blood volumeBody weight is decreased in external
bleeding and dehydration, but not changed in internal
bleeding,septic, anaphylactic or toxic shock.Early signs of
dehydration: poorskin turgor, sunken fontanelle in infants,
decrease in body weightSigns of internal bleeding: abdominal
tenderness, swelling, discoloration, guarding, bruising pattern
ofGrey, Turner sign and Cullens signSigns of gastrointestinal
bleeding: blood in the nose, mouth, throat or rectum (rectal
examination).NOTE: In infants, early symptoms and signs of
hypovolemic shock are less obvious than in adults .5353238/10/2015
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9/15Late SymptomsEarly symptoms plus the
following:DizzinessFaintingWeaknessConfusionLethargyLate SignsEarly
signs plus the following:Mottled, cyanotic skinIncrease of
tachycardia for at least 30/min upon standing , or bradycardia;
arrhythmiaIncreased breathing rate (tachypnea: >30/min) or
decreased breathing rate (bradypnea: 5 seconds or absentDecreased
body temperature (hypothermia)Low, narrow blood pressure (systolic
pressure falls earlier than diastolic, because it is more
dependenton blood volume; systolic blood pressure may not fall
until 30% blood is lost).Decreased or absent urination (