shock Flashcards
(19 cards)
what are the three broad categories of shock
- vasoconstrictive
- vasodilatory
- other (not involving vasomotor tone.
What atre the main features of vasoconstrictive shock and why have they occured?
-Increased HR to maintain CO
- Weak PQ, pale mm, slow CRT, cool extremites (blood diverted to central circlation)
- increased SVR, reduced preload, reduced stroke volume.
what are the main features of vasodilatory shock/why
- reduced stroke volume (maldisdribution of vascular volume or myocardial disfunction)
- impaired vascular tone leading to reduced SVR
- bounding pulses, rapid CRT pink mucus membranes and warm extremities.
-heart rate increased to try and compensate reduced stroke volume
What is the key difference n cats presenting in shock? Why?
Often bradycardic
- different mechanoreceptors in the atria and ventricles.
-hypovolaemia activates mechanoreceptors - only allow contraction when certain ventricuar filling pressures are achieved.
-(takes longer in shock so HR reduced)
Describe shock which doesnt fit into the vasodilatory or vasoconstrictive model.
- That which relates to the content or uptake of nutrient delivery to cells.
- eg anaemia, abnormal haemoglobin species, severe respiratory distress, hypoglycaemia
what are the key causes of hypovolaemic shock (4)
- Haemorrhage
- severe dehydration (>12%)
- Third space losses
- severe polyuria or GI loss.
what are the challenges/differences when assining hypovolaemia in the cat
- May be bradycardic (mechanoreceptors)
-Hr less proportional to volume loss in vet setting (high sympathetic tone) - Pulse profiling is harder
- mm colour normally paler
- Hypothermis can cause vaso constriction and cats are more prone.
What are the 3 main causes of cardiogenic shock
- cardiomyopathy (DCM, HCM)
- severe valvular disease
- Dysrhytmias
what is cardiogenic shock
inadequate cardiac output leading to poor perfusion (ie, forward failure)
What clin signs are seen in cardiogenic shock
- changes in perfusion parameters (vasoconstrictive picture)
- presense of cardiac signs (gallop, murmur, rhythmn)
- often have increased volume so may have resp issues
- can have V fast or V slow HR
Give some key causes of obstructive shock (4)
- Tension pneumothorax
- GDV
- PTE
- Cardiac tamponade
What is obstructive shock
Obstruction to normal blood flow leading to reduced venous return,reduced preload and left ventricular filling presure = low CO.
see signs of a vasoconstrictive picture similar to hypovolaemia
What are some causes of distributative shock
- SIRS
- Sepis
- Anaphylaxic
- Neurogenic
what is distributative shock
The redistribution of fluid away from the central circulation (interstitium or peripheral capillary beds) leading to a relative hypovolaemia.
What are the clinical signs of distributative shock
- hyperdynamic/vasodilatory signs
- tachycardia, bright mms, rapid CRT bounding pulses
what can complicate the assessment of late distribuative shock
- patient becomes hypovolaemic if enough fluid is redistributed.
- weaker PQ, slower CRT, severe tachycardia.
- BUT the mm usually remain injected, investigate for underlying inflammation.
How are cats different
- Again they can be bradycardic wiith weak pulses.
- unlikely to have injected mm
Describe anaphylactic shock
- variable, listed as vasodilatory but often more vasoconstrictive clin signs.
- (they have a relative hypovolaemia without the inflammatory cascade - still distributative)
- mast cell degranulation and histamine release.
- can have generalised weakness and syncope
- (may also have GI, resp, or derm concerns)
What is neurogenic shock
- Type of distributative shock resulting from reduced vasomotor tone = increased vascular capacity.
- Decreased sympathetic outflow is the cause
- EG brain injury, deep anaesthesia or epidural complication
