Post mortem and agonal changes

What are agonal changes

Develop in period just before and just after death

What causes passive congestion

Cardiovascular output failure and reduced venous return to the heart

What is pulmonary oedema caused by

Increasing intravascular pressure due to agonal impairment of venous blood return and loss of mechanism to maintain osmolarity

What happens in pulmonary oedema

Fluid leaks out through pulmonary capillaries into alveolar spaces

What causes pulmonary emphysema

Labored active breathing during agonal period causes residual air to remain in alveolar space

What are the common haemorrhages caused by agonal changes

• Cattle and horses - endocardial, epicardial

• Horses - adrenal

• Dog - pancreas

What are the effects of euthanasia

• Crystal formation on serosa or endothelium

• Complete necrosis of parenchyma

What are post mortem changes

• Autolysis of cells and tissues after death

• Growth of bacteria

What do post mortem changes cause

• Colour changes

• Changes in texture

• Tissue detachment

• Damage to cadaver

What does the extent of post mortem changes depend on

• Tissue or origin

• Temperature

• Thickness of fleece, fur and blubber

• Bacterial flora

• Time span between death and necropsy

What causes dark red colour changes

Hypostatic congestion where gravity draws blood to dependant side

What causes diffuse reddish stain

Haemoglobin released by red blood cell breakdown stains tissues

What causes greenish-yellowish colour changes

Bile staining

What causes green-black colour changes

H₂S enteric bacteria and haemoglobin making sulfmethaemoglobin

What changes in eye texture occur

Corneal opacity and reduced ocular turgor

What happens during gas formation causing change in texture

• Accumulates in liver and GI tract

• Bacteria proliferate after death and produce gas to speed up the autolytic processes

What happens in putrefaction

1. Bacteria proliferate in GI tract after death causing gas distension

2. This puts pressure on lungs and GI tract

3. Frothy oedema fluid passes up trachea

4. Rumen contents forced up oesophagus

What causes softening of solid organs

Increased concentration of proteolytic enzymes

What is rigor mortis

Stiffening of body due to depletion of ATP in muscle fibres

What other changes in texture can occur

• Post mortem clots

• Mummification

What tissue can become detached

Mucosa cause epilation of hair

What post mortem cadavar damage can occur

• Handling artefacts

• Scavenging by animals

How are post mortem changes minimised

• Cool carcase immediately after death

• Avoid freezing prior to necropsy