Circulatory shock Flashcards
What is meant by circulatory shock?
- It is the inadequate blood flow to the body that results in tissue damage
What are the causes of circulatory shock?
1) With decreased CO:
- Cardiac abnormalities that decrease the pumping action of the heart (like MI)
- Factors that decrease the venous return (like Hemorrhage)
2) Without a decrease in CO:
- Excessive metabolic rate
- Abnormal tissue perfusion patterns (like an impairment to diffusion)
Is arterial blood pressure a good indicator of circulatory shock?
No, as there are a lot of mechanisms that maintain it
- Arterial blood pressure can be misleading in evaluating the circulatory shock patient
What is the effect of hemorrhage on cardiac output and arterial blood pressure?
In severe hemorrhage and hypovolemic shock, the cardiac output decreases first while the systemic arterial blood pressure decreases later on, in addition to the fact that the sympathetic effect is better at compensating the arterial pressure compared to the cardiac output
What are the different stages of shock?
1) Non-progressive stage (full recovery without therapy)
2) Progressive stage (it will become irreversible without therapy)
3) Irreversible stage (no therapy will help)
What are the different negative feedback mechanisms that combat the non-progressive shock?
1) Baroreceptor reflex
2) Central nervous system ischemic response
3) Reverse stress-relaxation of the circulatory system (vasoconstriction)
4) Angiotensin formation by the kidneys
5) Vasopressin (ADH) secreted by the posterior pituitary gland
6) Blood volume compensatory mechanism
When is a shock reversible?
Non-progressive could become progressive depending on the amount of blood loss, for example, most people wouldn’t survive after a drop in BP to 45 mmHg
Generally, what is the positive feedback regarding progressive shock?
In progressive shock, the CO declines and thus cardiac contractility and VR will decrease too, in an attempt to reduce blood loss
What are the different cellular deterioration that occurs in severe shock?
- When the body reaches an irreversible stage, damage starts to occur on a cellular and tissue level:
1) Diminished Na+-K+ ATPase in the cell membrane leading to the swelling of the cells
2) Depressed mitochondrial activity especially in the liver which leads to liver necrosis
3) Lysosome breakdown, with intracellular release of hydrolase causing further cellular deterioration
4) Depressed cellular metabolism of nutrients and hormonal action
- All of those factors would ultimately lead to the deterioration of many organs like the liver, lung, and heart
Will transfusion help the patient if he is in the irreversible stage?
NO
Transfusion won’t make the patient survive if he is in the irreversible stage, it can cause a transient return of Cardiac output but it will fail again due to the irreversible tissue damage
What are the different types and causes of shock?
- Circulatory shock is due to a decrease in MAP (CO * TPR)
- CO can decrease due to:
1) Weakened heart (cardiogenic shock)
2) Loss of blood volume (hypovolemic shock “severe hemorrhage, vomiting, urinary losses, diarrhea, etc)
- Decreased total peripheral resistance, which is due to a widespread vasodilation that could be due to:
1) Vasogenic shock
- Septic shock (vasodilators released from bacteria)
- Anaphylactic shock (histamine released in severe allergy)
2) Neurogenic shock (loss of vascular tone due to decreased sympathetic stimulation)
What is meant by cardiogenic shock?
When a circulatory shock occurs due to decreased CO from a weakened heart
What is meant by vasogenic shock?
It is when a shock results from vasodilation due to histamine from allergy (anaphylactic) or vasodilators released from bacteria (septic)
What is meant by neurogenic shock?
It is a shock that results from loss of vascular tone due to decreased sympathetic nerve stimulation
What is meant by obstructive shock?
- Shock due to obstruction of blood flow:
- Tension pneumothorax
- Pulmonary embolism
- Cardiac tumor
- Cardiac tamponade
