8 - Circulatory Shock Flashcards
What is shock?
Shock can be thought of as a generalized state of tissue hypoperfusion with relatively or absolutely inadequate cardiac output
What is cardiogenic shock?
When the etiology of the shock is related to severely depressed cardiac function
What is hypovolemic shock?
When the etiology of the shock is related to reduced circulating blood volume
What is distributive, vasogenic or low-resistance shock?
When the etiology of the shock is related to severely reduced resistance
What is ostructive shock?
When the etiology of the shock is related to obstructive pathologies
What is another name for hypovolemic shock?
“Cold shock”
This is because blood pressure is low causing cold, pale, clammy skin
How does heart rate and respiratory rate respond to hypovolemic shock?
With the low blood volume, the reflex mechanism is to increase heart rate and increase respirations
What causes hypovolemic shock?
Hemorrhage
Lack of blood decreases both venous return and cardiac output
What accounts for the cyanosis seen in hypovolemic shock from hemorrhage?
Underperfusion of the skin
What is the result of this underperfusion?
Anaerobic glycolisis with large amounts of lactic acid as a by-product
If there is severe lactic acidosis, cardiac function depresses myocardial function, decreases the responsiveness of peripheral vasculature to catecholamines and the patient may lose consciousness
With the decreased blood pressure, baroreceptors will be activated - what is the result?
The baroreflex causes tachycardia, activation of the chemoreflex and therefore tachypnea
So pretty much…
- The patient will have a racing heart rate due to low BP
- The patient will have a rapid respiratory rate due to low oxygen and high CO2 in the blood
What will result from a severe sustained hemorrhage?
Phasic changes in heart rate
Describe the phasic changes in heart rate resulting from a severe sustained hemorrhage
The once fast heart rate slows down due to vagal activation
Tachycardia will then return
The cycle will continue like this
What happens to the vasculature in severe sustained hemorrhage?
Widespread vasoconstriction in both arteries and veins
- This helps sustain cardiac filling pressure
What happens to renal function in severe sustained hemorrhage?
- Renal function is depressed
- Metabolic products are retained and can further damage renal function, and combined with hypotension, can lead to acute renal failure
Describe the recovery period from moderate hemorrhage
Recovery can occur in 12-72 hours
- Hepatic protein synthesis restores plasma proteins within several days
- Epo (erythropoietin) restores red cell concentration within one week
How do you treat shock?
Treatment of shock must be targeted to the cause and helping the physiological mechanisms activated as a result of the shock
How do you treat shock from hemorrhage?
For hemorrhage, rapid restoration of volume by transfusion of whole blood is indicated
How do you treat shock from a burn?
For shock associated with burn, primarily plasma volume is lost, so the treatment includes replacement with plasma
What is important to keep in mind when treating patients with shock?
Tissue dehydration can ensue if a patient is treated with hypertonic solutions, as fluid is drawn from the tissues to equilibrate with the capillary (Starling forces)
So pretty much, don’t treat them with fluid too rich in sodium or other ions because it will dehydrate the tissue in order to balance it out
What are the three main cardiovascular crises that lead to shock?
1 - Severely depressed myocardial functional ability
2 - Grossly inadequate cardiac filling (due to low mean circulatory filling pressure)
3 - Profound systemic vasodilation either due to abnormal presence of vasodilators or an absence of neurogenic tone from sympathetics
Describe some situations in which cardiogenic shock would occur
Cardiogenic shock occurs whenever cardiac pumping ability is compromised
- Result of severe arrhythmias
- Abrupt valve malfunction
- Coronary occlusions
- Myocardial infarction
What is the direct consequence of cardiogenic shock?
Significantly decreased cardiac output
Describe some situations in which hypovolemic shock would occur
- Significant hemorrhage (usually greater than 20% of blood)
- Fluid loss from severe burn
- Chronic diarrhea
- Prolonged vomiting