ischaemia, oedema, heart failure

Haemorrhage def

Escape of blood from vascular system

Haemorrhage features

Overt/ internal

Acute/ chronic

Haemorrhage size nomenclature - petechia size

1-2mm

Haemorrhage size nomenclature - purpura size

>3mm

Haemorrhage size nomenclature - ecchymoses size

>1-2cm

Haemorrhage nomenclature - diapedesis

RBC traverse BV wall

Haemorrhage nomenclature - extravasation

Movement of WBC from capillaries to tissues

Haemorrhage nomenclature - haematoma

Solid swelling of clotted blood within tissue

Haemorrhage nomenclature - rhexis

Rupture of BV

Haemorrhage nomenclature - based on body cavities

Haemothorax, haemopericardium/cardiac tamponade, haemoperitoneum/ascites, haemarthrosis

Causes of haemorrhage 9

Physiological, trauma, parasites, bacteria, virus, toxic agents, clotting deficiencies, neoplasm (angiogenesis), agonal (death)

Outcomes of haemorrhage

Haemorrhagic shock, complete recovery, loss of function, iron deficient anaemia

Stages of degradation of haemoglobin by macrophages

Haem → biliverdin → bilirubin → haemosiderin

Oedema def

Accumulation of extravascular fluid (in intercellular tissue space, body cavities)

2 main Causes of oedema + appearance of fluid in each

Imbalance of forces responsible for transudation with normal capillary permeability → colourless fluid, low protein

Increased vascular permeability in inflammation → fibrinous/ purulent exudate

BV pressure changes that can cause oedema

Increased hydrostatic pressure - venous obstruction

Reduced plasma oncotic pressure - hypoproteinaemia

Lymphatic obstruction

Causes of oedema 5

Increased hydrostatic pressure, reduced plasma oncotic pressure, lymphatic obstruction, sodium retention, inflammation

How can sodium retention occur

Excessive uptake with renal insufficiency

Increased tubular reabsorption

How can inflammation lesd to oedema

Increased capillary permeability

Diseases characterised by oedema + how

Cardiac disease - heart failure

Chronic liver disease - decreased protein

Renal disease - protein loss

Chronic parasitism - protein loss

Protein losing enteropathy

Ascites def

Oedema in peritoneum

Anasarca def

Generalised oedema

Oedema from inflammation features

Exudate fluid - high protein, inflammatory cells

Most common site of oedema in dog

Peritoneal cavity

Most common site of oedema in cat

Thorax

Most common site of oedema in sheep (bottle jaw due to hypoproteinaemia)

Submandibular space, peritoneum

Most common site of oedema in horse

Limbs

Most common site of oedema in cattle

Brisket oedema (sc)

How can bottle jaw in sheep, goats, cattle occur

Johne’s disease (mycobacterium), intestinal parasites (haemonchus contortus), hepatic parasites (fasciola hepatica)→ hypoproteinaemia

Causes of pulmonary oedema (frothy)

Irritant gases, inflammation, toxic, agonal change, left sided CHF, passive hyperaemia

Why is CNS susceptible to oedema (hydrocephalus in ventricles, glaucoma)

No lymphatics

Causes of generalised passive hyperaemia

Heart failure, impeded venous return, increased pulmonary resistance

Heart failure def

Heart can’t pump blood at rate needed by tissues

How is arterial pressure + vital organ perfusion maintained (lead to heart failure)

Increased preload of dilation (contractility), myocardial hypertrophy, neurohormonal system (noradrenaline, RAAS, atrial natriuretic peptide)

CHF def

Build up of venous blood in systemic + pulmonary circulation

Consequences of CHF

Oedema, hypoxia, RAAS, chronic lung + liver congestion, fluid in peritoneum + thorax

Types of heart failure

Forward - from reduced CO + underperfusion

Backward/ CHF - from increased venous pressure

Consequences of left heart failure

Pulmonary congestion, pulmonary oedema, renal hypo perfusion → renin

Consequences of right heart failure (pressure overload of RV)

Increased pulmonary resistance, cardiac hypertrophy (concentric- pressure overload→ walls grow inward, eccentric- vol overload→lumen larger)

Effects of angiotensin 2

Arterioconstriction, increase cont, increase PCT na reabsorption, aldosterone release, ADH release (CD water reabsorption)

Noradrenaline - released from

Adrenergic cardiac nerves

Noradrenaline - Effect

Increase HR, increase cont

Atrial natriuretic peptide - release

Increased V load (CHF, chronic renal failure)

Atrial natriuretic peptide - Effects

Counteract RAAS - vasodilation, inhibit Na reabsorption, increase GFR, inhibit aldosterone secretion

What is nutmeg liver

Liver appearance in chronic congestion of central vein dilation due to right sided CHF

Pale hepatocytes

What is shown

Heart failure cells - alveolar capillaries leak → macrophages → haemosiderin (Perl’s Prussian blue stain)