cardiogenic and obstructive shock Flashcards
what is cardiogentic shock?
a disorder of cardiacfunction in the form of a critical reduction of theheart’s pumping capacity, caused by systolic ordiastolic dysfunction leading to a reduced ejectionfraction or impaired ventricular filling
can also be bradycardia, tachycardia
what are the causes of cardiogenic shock?
- Myocardial failure – end stage heart disease e.g. DCM, or sometimes seen in sepsis/SIRS
- Arrythmias – could be primary cardiac disease or secondary to external factors e.g. brady-arrythmia with hyperkalaemia, or tachy-arrythmias in splenic disease or hypoxia (i.e. another form of shock affecting oxygen supply to the heart)
- Valvular disease – severe failure preventing appropriate output – not common.
what are the clincal signs of cardiogenic shock?
Clinical signs are associated with poor output and peripheral vasoconstriction:
poor pulses, pale mms, prolonged CRT, reduced temperature (lack of blood to bum), but the heart rate can vary depending on cause.
if rectal temp is normal it is not cardiogenic shock/disease
what is the diagnostics for cardiogenic shock?
Clinical signs and history plus:
Low systolic blood pressure (< 90mmHg SAP)
Elevated Lactate.
Point of care ultrasound:
* Poorly contracting heart
* Evidence of cardiac disease
ECG
* Brady-arrythmia e.g. atrial standstill or AV block with escape complexes
* Tachy-arrythmia e.g. ventricular tachycardia and evidence of output failure e.g. pulse deficits.
Bloods for electrolytes
what is the treatment for cardiogenic shock?
Depends on the cause!
Hyperkalaemia – can be directly treated with glucose, insulin and fluid therapy (sodium glucose cotransport into cells, then the cell will pump back out the sodium in exchange for pottasium therefore reducing K conc inthe blood)
Splenic disease – remove the spleen
Other forms of shock leading to hypoxia – treat them
Myocardial failure - > Positive inotrope therapy
how does dobutamine work for cardiogenic shock?
Positive inotrope (Beta 1 agonist) makes heart pump harder, will increase myocardial oxygen demand. consider O2 support
Rapidly metabolised – constant rate infusion.
Commonly used in equine for cardiovascular support when anaesthetised.
how does pimobendan work for cardiogenic shock?
Phosphodiesterase III inhibitor – increases intracellular calcium sensitivity – positive inotropy. puts more calcium into the muscles therefore causes the muscles to contract harder
Does not increase myocardial oxygen demand.
can also be given for heart disease that is sub clinical as will increase pressure and therefore slow progression
what is obstructive shock?
Obstructive shock is a condition caused by the obstruction of the great vessels or the heart itself
what are the causes of obstructive shock?
Lesser circulation:
- reduced filling of the right side of the heart - > e.g. Cardiac Tamponade (pericardial effusion severe enough to equal right filling pressures)
- increased workload for the right ventricle e.g. pulmonary thromboembolism, or mediastinal mass compressing pulmonary vasculature.
Greater circulation:
- impedance in a major vessel e.g. severe aortic stenosis.
Reduced preload – i.e. reduced venous return - > vena cava compression e.g. neoplasia, GDV or tension pneumothorax (air pressure in the thoracic cavity is equal to caval pressure preventing venous return)
The location of the obstruction is key to determining the clinical signs, regardless, they will all result in reduced diastolic filling and therefore reduced output signs like cardiogenic shock.
what is the diagnosis of obstructive shock?
Clinical signs and history plus:
Elevated lactate
Point of care ultrasound:
* 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
what is the treatment for obstructive shock?
Relieve the obstruction if possible:
Cardiac tamponade – pericardiocentesis
Tension pneumothorax – thoracocentesis
GDV – gastric decompression
If immediate removal is not possible, supportive care:
PTE – platelet inhibitors (stops it getting worse and body will deal with it) and oxygen therapy
Neoplasia – force preload through a fluid bolus before surgery
name two postive inotropes
Pimobendan
Dobutamine
