Lecture 22: Shock Flashcards
What is circulatory shock?
Inadequate peripheral perfusion, lack of tissue oxygenation
Circulatory shock is __________ and ___________ but can cause death
Common and treatable
Inadequate perfusion leads to ________
Cell death
What is Hypovolemic shock?
- Blood loss (trauma)
- Plasma loss (burns)
- Water loss (vomiting, diarrhoea, increased urination and breathing [minor])
Outline the mechanism of uncompensated Haemorrhagic Shock:
Blood loss –> ↓central venous pressure –> ↓EDV –> ↓SV –> ↓CO –> ↓MAP
What happens when you lose ~60% of aortic pressure?
Compensatory mechanisms fail to return to you normal
What is Class 1 haemorrhage and it’s symptoms?
- loss of 0-15%
- slight tachycardia
- usually no significant change in BP, PP or respiratory rate
What is Class 2 haemorrhage and it’s symptoms?
- loss of 15-30%
- HR>100
- Tachypnea
- ↓PP
What is Class 3 haemorrhage and it’s symptoms?
- loss of 30-40%
- Marked tachycardia and tachypnea
- ↓ SBP
- Oliguria (↓urine production)
What is Class 4 haemorrhage and it’s symptoms?
- loss >40%
- Tachycardia
- ↓SBP, ↓PP
- No urinary output
- Immediately life threatening
How does the body respond when you lose 40% of blood volume?
Large sympathetic and adrenal stimulation
What are baroreceptors sensitive to?
- Stretch receptors int eh carotid sinus and aortic arch
- Sensitive to Δ pressure and to the rate of change
↓ in MAP causes a _______ in Barorecptor firing. This causes ___________ activation and __________ inhibition
↓ in BR firing
Sympathetic
Parasympathetic
Chemoreceptors are important when the MAP
60mmHg
Abdominothoracic pump
How do we compensate for hypovolemic shock?
- Increase circulating vasoconstrictors via catelcholamine secretion
- Increase ADH secretion
- increase renal water retention via Angiotensin II
- Increase HR and VR
- Activation of thirst mechanism
- Haematopoesis
- Redistribution of Interstitial fluid
When MAP<60mmHg, cerebral perfusion ↓, what is the response?
Cerebral ischaemia produces a very intense sympathetic discharge
What is decompensated shock?
Severe haemorrhage leads to a positive feedback loop that further decreases MAP.
Describe the mechanism of decompensated shock:
↓↓CO –> ↓MAP –> ↓Coronary Perfusion –> ↓Ionotropy –> ↓CO
↓MAP –> ↓Organ perfusion –> ↓Tissue Hypoxia –> Vasodilation due to sympathetic escape (desensitisation to sympathetics) –> ↓MAP
What does decompensated shock cause:
- Cardiac Failure
- Acidosis
- CNS depression
- Increase capillary permeability
- Toxin formation
- Vessel blockage by thrombosis
What is neurogenic shock?
Distributive shock: Loss of ANS signals to the vascular smooth muscle (due to CNS damage or depression) which causes vasodilation and pooling of blood
What is Psychogenic shock?
Sudden dilation of blood vessels and hypoperfusion of the brain that lead to loss of consciousness brought on my stress, pain or fright
What is Septic Shock?
Shock caused by bacterial infection that leads to vasodilation and increased capillary permeability and activation of clotting (Decrease in Blood volume and flow = ↓MAP)
What is anaphylatic shock?
Severe allergic reaction releases histamine causing vasodilation and blood vessel leakage. Also cause extravascular muscle spasm causes breathing problems.
What is Cardiogenic shock?
Shock related to failure of the heart to pump properly (caused by injury, valve defects, heart failure etc)
What is Obstructive Shock?
Obstruction to blood flow --> ↓CO caused by: - Cardiac Tamponade - Tension Pneumothorax - Pulmonary Embolism
What are the symptoms of shock?
- Restlessness and anxiety
- ↓ level of conciousness
- Dull eyes
- Rapid shallow inspo
- Nausea and vomiting
- Thirst
- ↓ Urine output
- Tachycardia
- Pale, cool and clammy in Hypovolemic and Cardiogenic shock
- Dry flushed skin in sepsis, Anaphylaxis and neurogenic shock
How do we treat shock?
- Increase volume
- Treat cause
- Correct acidosis
- Use ionotropic chronotropic agents
- vasoactive substances to increase SVR
