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B1. Cardiogenic Shock (the Heart)
B2. Hypovolemic Shock (Blood Volume)
B3. Anaphylactic Shock and Septic Shock (Blood Vessels)
C1. Compensated Phase: Immediate Response
C2. Compensated Phase:Intermediate Response
C3. Compensated Phase: Long Term Response
D. Physical Signs of impending Shock
E. Ultimately: Decompensated Phase (= irreversible)
Definition: Cardiovascular shock (= cardiac shock) is an acute failure to perfuse adequately the organs and the tissues in the body.
This diagram shows the cross section through the vascular system. At the beginning, in the aorta, its cross-section is very small (2.5 cm2). As one moves forward towards the capillaries, then the vessels do become narrower, but the number of vessels increases much more. Therefore, the cross-sections of all these vessels (the “sum”) increase a lot.
The cross section of all the capillaries together is a total of 5000 cm2, compared to only 2.5 cm2 for the aorta (2000x!).
If they were all wide open, their total cross section would be much more than the cross section of the aorta.
In fact, if all the blood vessels were all wide open at the same time, then the blood volume (approx. 5 litres) would easily fit in the small vessels and the blood pressure would drop to zero!
To be precise: this is called cardiovascular shock, to distinguish this from other types of shock such as psychological shock.
The heart can no longer pump properly due to:
External Fluid Loss:
Internal Fluid Loss:
Extreme vasodilation due to an intense allergic reaction (insect bite, allergic to medicine such as penicillin, etc.).
Extreme vasodilation due to bacterial infections and the entry of bacteria and their toxic products (=endotoxins) inside the blood.
Nervous system:
Decrease in parasympathetic and increase in sympathetic activity.
Hormones:
Increases in Angiotensin II, adrenaline and vasopressin (=ADH)Cardiac response:
– Increased chronotropy (tachycardia)
– Increased inotropy (contraction force)
Vascular Response:
Vasoconstriction in muscles, gut, skin and kidney -> increase in the Peripheral Resistance.BUT:
Reduced perfusion in these organs also leads to acidosis, weakness, oliguria (=decreased urine output) and pallor.
Skin:
The skin becomes wet, cold and pale due to the increased sympathetic stimulation.
Vascular Fluid Shift:
Up to 500 ml can be transfused back into the vascular system.
BUT:
This will produce a temporary anaemia (= less oxygen transported, which is bad) but also reduce viscosity (=less work for the heart, which is good!)
Kidney:
Reduction in renal excretion and increase in fluid intake (thirst)
Liver:
Increase in liver glycolysis (induced by adrenal and sympathetic stimulation) -> more blood proteins -> increase in oncotic pressure
Bone Marrow:
Increased production in red blood cells.
It may be interesting to know (and understand) the physical signs of an impending cardiovascular shock:
If the blood loss is too high and /or fluid replacement is started too late: then irreversible damage will occur to several organs or systems.
The most at risk are:
Ultimately: Death
