Hypovolaemic and distributive shock Flashcards
What is shock?
tissue hypoxia
What can cause shock?
Reduced oxygen delivery to tissues (hypoxaemic e.g., anaemia)
Excessive oxygen demand/usage by tissues (metabolic e.g., hyperthyroidism in cats)
Inadequate utilisation of oxygen by tissues (metabolic e.g., hypoglycaemia, mitochondrial dysfunction)
What can cause reduced oxygen delivery to tissues?
Reduced blood pressure and oxygen delivery:
hypovolaemia - loss of blood volume
Vasodilation - reduced concentration of blood
Blocked pipes - e.g., thrombus
Heart stops working e.g. mechanical or electrical activity
Obstruct the heart e.g., pericardial effusion
What is the cause hypovolaemic shock?
loss of fluid from vascular compartments
What are the different causes of hypovolaemic shock?
Traumatic - blood loss
Haemorrhage from other causes e.g., coagulopathy
Fluid loss e.g., severe vomiting and diarrhoea
What are the clinical signs of hypovolaemic shock?
Increase cardiac output – Tachycardia
Prioritise vital organs – peripheral vasoconstriction – pale mms, prolonged CRT, poor pulse quality.
Reduced mentation due to reduced cerebral oxygen supply
How is hypovolaemic shock diagnosed?
Clinical signs + history
Low BP
Elevated lactate
POCUS (collapsing caudal vena cava, poorly filling heart)
How is hypovolaemic shock treated?
Fluid loss - isotonic fluids (bolus to prevent hypoxia causing brain death)
Blood/plasma loss - transfusion
Always start with isotonic fluids and follow with transfusion if necessary
Hypertonic may be useful in large animals e.g. cow, horse
What is distributive shock?
Normal blood volume is spread across a much larger area => decreased blood pressure
Vasodilation due to inflammation, loss of vascular tone
Can also be caused by leaky vessels
What is the most common cause distributive shock?
Sepsis/SIRS most common - inflammatory cascade releases pro-inflammatory cytokines that promote vasodilation and permeability
What are the clinical signs of distributive shock?
Vasodilation - >
- injected mucous membranes
- shortened CRT (pooling of blood in membrane capillaries)
- bounding/hyperdynamic pulse (big difference between systolic and diastolic pressure
- Tachycardia due to hypotension.
Permeability - >
- peripheral oedema
- pulmonary oedema
- cavitatory effusions.
How is distributive shock diagnosed?
Clinical signs and history
Low BP
elevated lactate
POCUS:
- Collapsing caudal vena cava (flat)
- Poorly filling heart
- Septic focus e.g. septic abdomen (free fluid)
- Evidence of vascular leak e.g. pulmonary oedema, small effusions.
- Gall bladder halo sign (oedema of the wall) - seen in anaphylaxis and sepsis
Why does distributive shock cause a bounding/hyperdynamic pulse?
black line - normal pulse
Red line - distributive shock => decreased diastolic pressure => heart pumps harder to compensate for lower diastolic pressure but volume of blood is lower => short lived, strong beat
Applying pressure to pulse - can easily compress pulse in distributive shock
How is distributive shock treated?
Volume support - fluid bolus
Vascular tone treated:
- vasopressors - causes short lived peripheral vasoconstriction - given over time
- e.g., noradrenaline or dopamine
Permeability support:
- plasma infusion if low albumin
- start feeding
Describe nor-adrenaline/nor-epinephrine as vasopressors
neurological version of adrenaline
catecholamine and potent vasoconstrictor due to high affinity for alpha-1 receptors
useful for managing vascular tone
Potent at high doses - be careful of excessive peripheral vasoconstriction - can lose digits etc
Describe dopamine as a vasopressor
nor-adrenaline precursor - stimulates production of noradrenaline (indirect effect)
Direct dopaminergic effect on both alpha and beta receptors
alpha-1:
- increases systemic vascular resistance
beta-1:
- increases HR
- heart needs to work harder so can cause tachyarryhtmias
Use in lower doses
What would the clinical signs of both hypovolaemic and distributive shock occuring at the same time?
Bounding pulse (weak due to hypovolaemia, but hyperdynamic due to distributive)
Normal CRT (distributive vs hypovolaemia)
Tachycardia (can be bradycardic in cats)
Elevated lactate
Low BP
Normal temp (sepsis vs hypovolaemia)
Normal MM colour (distributive vs hypovolaemia)
Elevated resp rate
Decreased mentation due to hypoxia - biggest sign of shock vs a little bit of pain
How can you treat a patient with both hypovolaemic and distributive shock?
fluid bolus’
vasopressors
both at same time
How can you work out if a patient has both distributive and hypovolaemic shock?
POCUS:
- flat vena cava (hypovolaemic)
- collapsing heart (hypovolaemic)
- fluid in lungs (vascular leak - septic)
- gall bladder halo (vascular leak - septic)
- free fluid in cavities (vascular leak - septic)
How can a patient with both hypovolaemic and distributive shock be monitored during treatment?
lactate and BP
