L21: Hypertension, Hypotension, Shock Flashcards
When does venous hypertension develop
Impaired outflow of venous blood a.k.a passive congestion
Give examples of conditions that may lead to venous hypertension pls
Congenital/ acquired arteriovenous anastomosis e.g. congenital hepatic arterioportal fistula
What is a consequence of venous hypertension
INC plasma hydrostatic pressure in tributary veins, venues, capillary beds upstream –> oedema and diapedesis of erythrocytes
What is pulmonary hypertension
sustained increase in systolic BP in pulmonary artery
>30mm Hg dog/cat
What is cor pulmonale
R heart disease caused by pulmonary hypertension
Why does cor pulmonale develop
pressure overload on right ventricle during systole –> R sided congestive heart failure or chronic compensatory concentric hypertrophy of right ventricle
In which circumstances does pulmonary hypertension develop
Congenital anomalies –> L to R shunting blood E.g.
Patent ductus arteriosus
Atrial septal defect
Ventricular septal defect
Inc resistance in pulmonary blood flow E.g.
heart worm
pulmonary neoplasia
Severe chronic diffuse interstitial fibrosis
Whats systemic hypertension
sustained increased in systemic arterial BP
Which diseases can predispose animals to the development of systemic hypertension
Diabetes liver disease glomerular disease renal disease endocrinopathies NSAIDS
Describe how some endocrinopathies can lead to systemic hypertension in animals
middle aged cats can develop nodular hyperplasia of their thyroid gland, generating too much T3, T4
Low thyroid function & obesity in older dogs
Cushing’s (high adrenocortical cortisol)
Why can systemic hypertension be self-perpetuating if not adequately treated
related to underlying disease process –> must treat this to reduce hypertension
Which organs are most susceptible to systemic hypertension
eyes
brian
kiddys
What are some clinical signs that can develop subsequent of systemic hypertension
PU/PD –> reflects both diuresis and underlying primary disease process (E.g. renal failure, diabetes mellitus, hyperthoiridism, hyperadrenocorticism)
Cardiac murmur +/- galloping heart
epistaxis
strokes
What is systemic hypotension
sustained decrease in systemic arterial blood pressure (<60mm cats, dogs or <80mm Hg systolic pressure)
What overall cardiovascular changes can cause systemic hypotension
dec in CO and TPR
What does persistent systemic hypotension lead to
shock
Define shock
generalised phenomenon peripheral circulatory failure, characterised by systemic hypo perfusion and systemic hypotension
What are the types of shock
Cardiogenic shock Hypovolaemic shock Distributive Neurogenic Anaphylactic Septic
What is cardiogenic shock
rapid decrease in systolic CO despite adequate blood volume
what causes cariogenic shock
Severe dilated cardiomyopathy* Myocardial infarction Cardiomyopathy Atrial fibrillation Tachyarrhythmias Rupture chordae tendinae Rapid pericardial effusion Pulmonary hypertension/ severe systemic hypertension Heart worm
What is hypovolaemic chock
significant reduction in circulating blood volume (>20-25%)
what are some causes of hypovolaemic shock
haemorrhage
severe fluid loss (vomiting/ diarrhoea)
or fluid loss through increased vascular permeability
sequestration fluid (e.g. grain overload)
What is distributive shock
inappropriate vasodilation arterioles, pooling of blood in capillary beds & venous channels
(total reduced peripheral vascular resistance, decreased effective circulating blood volume)
What are the 4x types of distributive shock
neurogenic shock
anaphylaxis
sepsis
heat stroke
Describe neurogenic shock
fear/ pain –> brain signals affect vasomotor centre of medulla –> inappropriate peripheral vasodilation/ bradycardia
Describe anaphylactic shock
mass mast & basophil degranulation= mass release vasoactive amines e.g. histamine
What is septic shock
e.g. endotoxin release –> endothelial release vasodilators -> systemic arteriolar vasodilation –> hypotension & decreased effective circulating blood volume
High LPS doses cause also activate platelets, activate cascade, cause widespread vascular injury & thus widespread DIC
What are the 3 stages of shock
- Initial non-progressive stage
- Progressive stage of tissue hypo perfusion
- Irreversible stage
Describe the initial, non progressive stage of shock
COMPENSATED HYPOTENSION
baroreceptors detect hypotension
chemoreceptors detect hypercapnia
Stimulation sympathetic NS
Activation RAAS
What is the outcome of initial non progressive/ compensated shock?
Vasoconstriction of arterioles and venules
Maintenance of blood pressure
Conservation of fluid
In which case is the bodies attempt to compensate for initial non-progressive shock essentially useless?
In cases of distributive shock, where peripheral vasoconstriction is a characteristic, therefore value of compensatory response is diminished
Describe the progressive stage of tissue hypoperfusion as part of shock
sustained vasoconstriction in nonessential organs= hypoxia –> lactic acid –> reversal of vasoconstriction –> pooling of blood in microcirculation
Hypoxic injury can trigger DIC
Oliguria
Describe the irreversible stage of shock
shock will eventually lead to widespread hypoxic ell necrosis, multiple organ failure +/- DIC
Death can’t be prevented in this stage, only in 2nd stage with correction of underlying haemodynamic abnormalities
What are the clinical signs of hypovolaemic and cardiogenic shock
hypotension tachycardia thready pulse tachypnoea MM pallor inc CRT decreased mentation
What are the clinical signs of cardiogenic shock
arrhythmia,
murmur
muffled heart sounds
What are the clinical sings of distributive shock
dark red (injected) MM, rapid CRT
