Shock
Some common signs:
Paleness or cyanosis
Hypotension
Cold and clammy skin
Oliguria
Dulled sensorium
Traditional view : Hypotension
Traditional treatment principle: Raise BP
Today's point of view:
modern view : low perfusion
modern treatment principle :Improve perfusion
blood pressure ×
blood flow √
Content you should know:
I.Concept
II.Classification
III.Stages and their pathological changes and mechanisms
IV.Organ dysfunction
V.Treatment principles
First of all the Concept of a Shock:
What actually shock is ?
Shock is a dangerous clinical pathological process characterized by an acute circulatory failure, inadequate blood flow and oxygen delivery to the tissue of the body.
II. Classifications of shock:
According to:
Cause
Perfusion factors
Cardiac output
Causes:
Common character :Sharp drop of the ECBV
According to the causes：
1-Hypovolemic shock
2-Burn shock
3-Traumatic shock
4-Infectious shock
5-Cardiogenic shock
6-Neurogenic shock
7-Anaphylactic shock
Perfusion Factors
Three determinants of effective perfusion
Sufficient blood volume
Normal function of heart pump
Normal vasomoter function
three types ：
Hypovolemic shock
Cardiogenic shock
Vasogenic shock
Cardiac output:
◆ Hypodynamic shock (Cold Shock): inadequate or falling cardiac output
Vasoconstriction
seen in most of the shock
◆ Hyperdynamic shock (Warm shock): normal or high cardiac output
Vasodilation
seen in anaphylactic shock , neurogenic shock and part of infectious shock
III. Stages and their pathological
changes and mechanisms :
Phased basis:
The changes of microcirculation
The normal structure of microcirculation
Outflow: Venule
Take Hypovolemic shock as an example:
Stages:
Ischemic hypoxia Stage
↓
Organic failure Stage
1. Ischemic hypoxia Stage:
(1) Changes of microcirculation
Decreased blood volume
↓
Sympathetic-adrenal system activation
↓ ↓
Capillary constriction Arteriovenous shunt open
↓ ↓
Tissue hypoxia
(2) Significance of compensation
1- Auto blood transfusion
Sympathetic-adrenal system activation
↓
constriction of the capacitance vessel
↓
Disgorging stored blood
↓
“The first-line defensive response”
2- Auto fluid transfusion
Mechanism of auto fluid transfusion
Sympathetic-adrenal system activation
↓
precapillary resistance > postcapillary resistance
↓ Hydrostatic pressure↓
↓
promoting tissue fluid reflow to blood
“The second-line defensive response”
3- Redistribution of blood volume
Redistribution of blood volume
obvious constriction in Some organs’ vessel ,others are not
↓
ensure adequate blood flow through the brain and heart
“The third-line defensive response”
(3) Clinical Manifestation
What are the determinants of Bp？
-Blood volume
-Heart pump
-Peripheral resistance
Mechanism of blood pressure does not drop：
Auto-transfusion
Auto-perfusion
RAAS
ADH
During the early stage of hypovolemic shock,
the patient can maintain the normal BP.
Acute or Severe blood loss and fluid loss Should be excepted
Question :
Is Bp the most important index in diagnosis and management of shock？
NO！
Other Manifestations ：
Sympathetic - adrenal system activation
↓ ↓ ↓
↓ small blood vessel constriction Activation of the sweat glands
↓ redistribution of blood
↓ ↓ ↓ ↓
↓ GFR↓ ↓ ↓
↓ ↓
HR↑ Urine output ↓ cool and moist skin
How about the consciousness of patient?
agitate, restless
2. Stagnant hypoxia Stage
Prolonged excitation of Sympathetic adrenal system
↓ ↓
Widespread tissue hypoxia ↓
↓
Acid metabolites produced: Endothelial cell injury
Lactic acid,Histamine,Adenosine ,NO,etc
↓ ↓ ↓ ↓
precapillary postcapillary resistance is still high permeability↑ ↓
resistance↓
↓ ↓
blood fluid slowly,Congestion < ::::::: RBC aggregation WBC rolling and block
↓ platelet aggregation and adhension
Tissue hypoxia
↓
Acidosis and some cytokines
↓
precapillary resistance < postcapillary resistance
↓
Slow blood flow
↓
Stagnant hypoxia :::::: > vicious circle
Clinical Manifestation
Stasis in microcirculation
↓
Returned blood volume↓ Congestion↓ ↓
CO ↓ Cyanosis
↓ ↓ ↓
Renal blood flow ↓ Cerebral ischemia
↓ ↓ ↓
Oliguria Bp ↓ coma
3. Organ Dysfunction Stage
severe hypoxia in tissue level
↓
Cell injury, Blood vessel injury ,Collagen exposure
Blood coagulation factors activation Acidosis
↓
DIC
(disseminated intravascular coagulation)
DIC is an acquired hemorrhagic syndrome
in which both clotting and bleeding occur
simultaneously. Widespread clotting in small
vessels leads to consumption of the clotting
factors and platelets, which in turn leads
to bleeding.
DIC <::::::::> shock
MSOF----multiple system organ failure
MODS is the progressive dysfunction of two or more organ systems resulting from an uncontrolled inflammatory response to a severe illness or injury.
Review
Ischemic hypoxia Stage
↓
Stagnant hypoxia Stage
↓
Organic failure Stage
IV. Organ dysfunction
1. Shock lung
Shock lung or the adult respiratory distress syndrome (ARDS) is a form of respiratory failure that can follow severe shock. Alveolar capillary permeability is increased and interstitial edema develops, the lung becomes engorged and gas exchange is impaired, hyaline membrane develops.
Shock lung
Rapid and labored respiration
PaO2↓
Diffusion impairment
Ventilation-perfusion imbalance
2. Acute renal failure
Renal failure- Oliguria
- Azotemia
- Hyperkalemia
- Metabolic acidosis
Functional renal failure
Parenchymal renal failure
3. Heart failure
Heart failure
- Acidosis
- Hyperkalemia
- Decreased PO2
- DIC
- Endotoxin
4. Gastrointestinal dysfunction
ischemic injury
redistribution of blood flow
DIC
Endotoxin
↓
Gastric mucosal damage, intestinal ischemia and stress ulcer
↓
Clinical manifestation:
Abdominal pain
Vomiting blood
Blood in stool
V. Treatment:
Shock is easier to prevent than to cure.
Don’t wait for symptoms to develop before beginning the treatment for shock.
prevention first
1. Blood and Plasma transfusion:
Lose?
The amount is based on how much patients do
Need?
2. Vasoactive Drugs:
Note: a precondition
expansion of blood volume
Vasodilator substance.
Vasoconstrictive substance.e.g;
neurogenic shock
anaphylactic shock
3-Other treatment measures:
-Oxygen therapy
-treatment on acidosis
-treatment by the head-down position
-treatment with glucocorticoids
Questions just for review!
1. What is the concept of shock?
2. What are the major causes of shock?
3. How many stages are there in hypovolemic shock? What are they?
4. What are the compensatory mechanisms and significance in first stage of hypovolemic shock?
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