Cardiogenic and obstructive shock Flashcards
What is cardiogenic shock?
heart is not working => poor perfusion
What are causes of cardiogenic shock?
myocardial failure e.g., DCM, sepsis induce cardiomyopathy (SICM)
Arrythmias - primary cardiac disease or secondary to external factors e.g., brady-arrhythmias with hyperkalaemia, tachy-arrhythmias in hypoxia
Valvular disease - severe failure preventing appropriate output
What are the clinical signs of cardiogenic shock?
associated with poor output and peripheral vasoconstriction (compensation):
- poor pulse
- pale MMs
- prolonged CRT
- reduced temp (always)
Same as hypovolaemic shock
How can you diagnose cardiogenic shock?
Clinical signs and history
Low BP
Elevated lactate
POCUS:
- poorly contracting heart
- evidence of cardiac disease
ECG:
- brady-arrhythmia e.g., atrial standstill - no P wave - hyperkalaemia is immediate problem
- tachy-arrhythmia e.g., ventricular tachycardia => pulse deficits (ventricular contraction with no output - pulse does not align)
Bloods for electrolytes
How can cardiogenic shock be treated?
depends on cause:
Hyperkalaemia - direct treatment with glucose, insulin and fluid therapy
Splenic disease => Vtach - splenectomy
Myocardial failure - positive inotrope therapy (pimobendan + dobutamine)
How does dobutamine treat myocardial failure?
Positive inotrope (Beta 1 agonist), will increase myocardial oxygen demand.
Rapidly metabolised – constant rate infusion.
Commonly used in equine for cardiovascular support when anaesthetised.
Fast acting - good in acute patients
How does pimobendan treat myocardial failure?
Phosphodiesterase III inhibitor – increases intracellular calcium sensitivity – positive inotropy.
Improves contraction efficiency
Does not increase myocardial oxygen demand
What is obstructive shock?
Obstructed blood flow => tissue hypoxia
What are the causes of obstructive shock?
Lesser circulation - reduced filling of right side of heart e.g., cardiac tamponade (severe pericardial effusion that equals right side filling pressures
Increased workload of right ventricle e.g., pulmonary thromboembolism or mediastinal mass compressing pulmonary vasculature
Greater circulation - impedance of major vessel e.g., severe aortic stenosis
Reduced preload - reduced venous return => vena cava compression e.g., GDV, neoplasia, pneumothorax (air in chest at high enough pressure to equal caval pressure, preventing venous return)
How is the the cause obstructive shock diagnosed?
POCUS:
- Loss of glide sign – tension pneumothorax
- Pericardial effusion and right sided collapse of ventricle and atria – cardiac tamponade
- Right ventricular enlargement – pulmonary hypertension – pulmonary thromboembolism
- CVC distension (downstream occlusion) or compression
- Aortic outflow obstruction
- Neoplasia
How is obstructive shock treated?
Relieve obstruction:
- Cardiac tamponade – pericardiocentesis
- Tension pneumothorax – thoracocentesis
- GDV – gastric decompression
Follow removal of obstruction - find reason for obstruction
Supportive care if immediate obstruction removal not possible:
- pulmonary thromboembolism – platelet inhibitors and oxygen therapy
- Neoplasia – force preload through a fluid bolus before surgery
What is respiratory/hypoxic shock?
Poor lung function - V/Q mismatch and/or increased difficulty of oxygen diffusion into vessels:
- ventilatory problems e.g., primary respiratory failure, airway blockage, pneumothorax etc.
- alveolar or interstitial disease increasing gradient e.g., pulmonary oedema, drowning
=> shock
what is a global hypoxic-ischaemic event?
descriptive term meaning the whole body has had a period of severe hypoxia.
What is cryptic shock?
Refers to localised hypoxia, specifically where organ damage may be occurring, but the situation is not obvious clinically yet
What are the 4 main types of shock?
Hypovolaemic:
- haemorrhagic
Distributive:
- septic/SIRS
- anaphylactic
- neurogenic
Cardiogenic
Obstructive
