Lecture 11.1: Shock and Cardiac Arrest Flashcards
What is Shock?
Acute circulatory failure with inadequate or inappropriately distributed tissue perfusion
Mean Arterial BP Equation?
Mean Arterial BP = CO x TPR
Cardiac Output Equation?
CO = HR x SV
Fall in Cardiac Output in Shock (3)
- Loss of volume (hypovolaemic)
- Fall in contractility (cardiogenic)
- Reduced cardiac filling (mechanical)
Fall in TPR in Shock (1)
Profound vasodilatation
(distributive)
Causes for Hypovolaemic Shock (4)
- Blood loss (haemorrhage)
- GI loss
- Burns
- Third space loss
What does the Severity of Hypovolaemic Shock depend on? (2)
- The volume lost
- The speed of loss
Pathophysiology of Hypovolaemic Shock: Decreased blood volume results in…? (5)
- Fall in venous pressure
- Reduced EDV [= reduced
preload] - Reduced SV
- Fall in CO
- Fall in mean arterial BP
The reduction in mean arterial BP is detected by baroreceptors, this triggers compensatory mechanisms. Name these. (3)
1) Increased sympathetic nervous
system activity
2) Increased RAAS activity
3) Internal transfusion
Effect of increased Sympathetic NS Activity (4)
- Vasodilation of cerebral/coronary vessels
[Adr on β2] - Increase HR [NA on β1]
- Increase contractility [NA on β1]
- Venoconstriction [NA on ɑ1]
Effect of increased RAAS Activity (2)
- Decrease in BP causes renin release
- Renin –> angiotensin I –> angiotensin II
How does Angiotensin II release increase
MABP? (5)
- Increasing sympathetic activity further by
causing NA release (↑CO /TPR) - Arteries –> vasoconstricton (↑TPR)
- Kidney –> Na+ reabsorption
- Adrenal gland –> aldosterone release –>
Na+ reabsorption - Brain –> ADH release
Effect of Internal Transfusion (2)
- Reduced circulating reduces the
hydrostatic pressure of capillaries - Resulting in a net movement of fluid into
capillaries
What is Decompensated Shock?
- The compensatory mechanisms help a
shocked individual maintain a reasonable
blood pressure and tissue perfusion - However as shock worsens, these
mechanisms become insufficient and
perfusion of vital organs is no longer
maintained
Prolonged peripheral vasoconstriction results in..? (7)
- Impaired tissue perfusion
- Tissue hypoxia
- Release of metabolic vasodilators
- Fall in TPR
- Further fall in mean arterial BP
- Vital organs no longer being perfused
- Multi-system failure
ABCDE Acronym
A: Airway
B: Breathing
C: Circulation
D: Disability (level of consciousness)
E: Environment
What is Mechanical Shock caused by?
Caused by a fall in filling of the ventricles
Why might there be a fall in filling of the ventricles?
- This may be from restriction to filling e.g.
cardiac tamponade - May be from obstruction to filling e.g.
pulmonary embolism, tension
pneumothorax
What is Cardiac Tamponade?
It is a medical or traumatic emergency that happens when enough fluid accumulates in the pericardial sac compressing the heart and leading to a decrease in cardiac output and shock
Signs and Symptoms of Shock (8)
- SOB
- Pleuritic Chest Pain
- Haemoptysis
- Raised JVP
- Tachycardia
- Hypotension
- Pale
- Sweaty
Signs and Symptoms of Cardiac Tamponade (4)
- Becks Triad: ↓ BP + ↑ JVP + Muffled
heart sounds - Tachycardia
- SOB
- Features of compensation
How is Cardiac Tamponade Treated?
- Pericardiocentesis
What is Cardiogenic Shock caused by?
Caused by a fall in contractility so the ventricles are unable to empty properly
Why may ventricle contractility decrease? (3)
- MI
- Acute worsening of heart failure
- Arrhythmia (loss of coordinated pump
action)
What is Distributive Shock?
- Also known as vasodilatory shock
- Profound peripheral vasodilation = Decreased TPR
- Blood volume is the same but the
capacity of the ‘container’ has increased
Why may Distributive Shock occur? (2)
- Septic (Toxic) Shock
- Anaphylactic Shock
What is Septic Shock?
- Bacteria in blood release endotoxins that
stimulate systemic inflammatory response - Vasodilation (fall in TPR)
- Increased vascular permeability (thus fall
in intravascular fluid volume -> fall in CO) - Thus fall in mean arterial BP
Clinical Presentation of Septic Shock (4)
- Tachycardia
- Hypotension
- Warm/Red Extremities
- Fever
Treatment of Septic Shock
SEPSIS-6
What is Anaphylactic Shock caused by?
- Hypersensitive response from the
immune system to usually harmless
substances - Reaction to allergens results in release of
histamine from mast cells
What is the Effect of Histamine on Blood Vessels
- Histamine is a potential vasodilator
- Thus fall in TPR and arterial BP
Clinical Presentation of Anaphylactic Shock (5)
- Tachycardia
- Hypotension
- Warm/Red Extremities
- Airway Swelling: SOB, stridor
- Rash
Treatment of Anaphylactic Shock (3)
- Adrenaline
- Hydrocortisone
- Chlorphenamine
What happens to your various organs during Decompensated Shock? (brain, kidneys, skin)
1) Brain: altered mental status
2) Kidneys: oliguria (decreased urine output)
3) Skin: cool, blue (mottled) peripheries
What is Cardiac Arrest?
- Heart suddenly stops pumping effectively
- Loss of cardiac output
- Due to a loss of effective electrical or
mechanical activity
How does Cardiac Arrest present clinically? (3)
- Loss of Consciousness
- Loss of Pulse
- Loss of Breathing
The 4 H’s & 4 T’s of Cardiac Arrest
- Hypoxia
- Hypothermia
- Hypovolaemia
- Hyper/Hypokalaemia (metabolic)
- Toxin
- Tamponade
- Tension Pneumothorax
- Thrombosis (pulmonary or coronary)
Chain of Survival for Cardiac Arrest (4)
- Early recognition and call for help
- Early CPR
- Early Defibrillation
- Post-resuscitation care
