PM changes and artefacts Flashcards
what is algor mortis
cooling after death
which cells have the lowest resistance to hypoxia?
brain and spinal cord (4mins)
Which cells have the greatest resistance to hypoxia?
bone and corneas (48hrs)
PM artefact that occurs following resuscitation attempt (incl. masks/intubation) against buccal mucosa are which type of injury?
mucosa of cheek against teeth = abrasion
Person who had MI in street and ambulance attempted CPR is found to have abrasions to face and a perforated stomach - explain this.
Abrasions from fall to ground
Stomach can tear when pressure applied during chest compressions, especially when stomach is full.
bacteria favours which kind of putrefaction?
wet putrefaction is favoured by bacteria
Adipocere is favoured in dry conditions - true or false?
false
adipocere is favoured in wet conditions
mummification favoured in dry conditions
A foetus lost to intra-uterine death will have which sign of putrefaction?
maceration of foetus due to sterile but wet environment of placenta.
When determining the PMI, the rate method observes what?
Rate method observes/measures changes which occur at a known rate.
E.g. vitreous K+, rigor, cooling, putrefaction, lividity
What does the concurrence method use in determining PMI?
Events which occurred at known times e.g. watch which stopped by blow, digestion of meal, or CCTV footage.
algor mortis is a good indicator of PMI after 24hrs - true or false
false
algor mortis is a good indicator of PMI in first 24hrs
What do you need to bear in mind when using cooling to determine PMI?
Should only be used in cool and temperate climates.
The body temperature at time of death is unknown and can be higher/lower depending on CoD.
The environmental temperature during cooling period has likely fluctuated.
Newton’s cooling curve shifts left when?
Curve shifts left in hypothermia, thin people, cool climates
Newton’s cooling curve shifts right when?
Shifts right in hyperpyrexia, warm climate, heavy clothing,.
The Henssge nomogram allows correction for…?
body weight, clothing, drafts, water
factors applied to body weight
When can Henssge nomogram NOT be used?
Strong heat source nearby Cooling source nearby Underlying surface conducts away heat (metal table) Abnormal body temp. at death Body has been moved
What does Henssge nomogram assume?
normal body temp at time of death and no change in cooling conditions.
What are the stages of muscle flaccidity?
- Primary flaccidity
- Rigor mortis
- Secondary flaccidity
Primary flaccidity is permanent - true or false
false
primary flaccidity = no tone
secondary flaccidity = permanent
rigor is postponed in freezing - true or false
true
Describe the muscle stiffening that occurs in hot temperatures.
accelerates rigor process
protein coagulation and shortening of muscles -> pugilistic posture
In life, formation of actin-myosin bridges stimulates muscle contraction. How is this affected in death?
Ca2+ still floods into cells and the actin-myosin bridges form however they cannot relax due to lack of ATP (required for breakdown) -> sustained contraction.
Fully formed rigor can be broken and re-form - true or false
false
fully formed rigor if ‘broken’ by force (undressing) will not reform
Partially formed rigor will continue to form even if broken - true or false
true
What factors effect the rate of rigor development?
onset/duration depend on:
environmental temperature
muscle activity prior to death
Rapid onset of rigor is associated with shorter duration - true or false
true
Rapid onset of rigor is associated with short duration (will lessen faster)
rigor develops in smallest muscles first then larger muscle groups affected next - true or false
FALSE
rigor develops simultaneously in all muscles
smaller muscles groups are COMPLETELY involved earlier vs. larger muscles and this passes off (putrefaction) in the same sequence
onset of rigor mortis is a useful indicator of PMI - true or false
false
onset of rigor is an unreliable indicator of PMI
What is the average time until first appearance of rigor mortis?
first appearance on average 3hr pm
Rigor is fully established on average by 8hrs PM, but what is the range in which this can occur?
fully established by 8hrs but range is 2-20hrs
How long does rigor often last for?
24-36hrs
Why does muscle activity or starvation prior to death hasten rigor?
glycogen stores are depleted
What situations hasten rigor onset?
high environmental temp
muscle activity or starvation prior to death
septicaemia
children, elderly
you need to be careful not to confuse intensity of rigor with…?
degree of development
e.g., stronger intensity of rigor in strong adult males vs. elderly woman but this does not mean it is further ahead in process
stiffening that occurs at moment of death and persists into period of rigor mortis is known as ?
cadaveric spasm - rare, instantaneous form of rigor
Rule of thumb: warm + flaccid =
warm + flaccid = dead <3hrs
Rule of thumb: warm + stiff =
warm + stiff = dead 3-8hrs
Rule of thumb: cold + stiff =
cold + stiff = dead 8-36hrs
Rule of thumb: cold + flaccid =
cold + flaccid = dead >36hrs
what is lividity?
the gravitational settling of liquid blood in capillaries - seen as purple discolouration in dependent areas
punctate haemorrhage is seen in which type of lividity?
punctate haemorrhage within intense lividity
what is lividity a good indicator of?
position of body since death
When is lividity first noticeable and when is it well-formed?
red patches often within 30mins (up to 2hrs)
wellformed by 4hrs
Lividity is at its maximum intensity when?
8-12hrs
Lividity that no longer blanches tells you … ?
Lividity is fixed after 12hrs and no longer blanches
Which patients have minimal lividity?
delayed or minimal lividity in anaemia or haemorrhage
Fixation of lividity is absolute - true or false.
false
fixation is when lividity no longer blanches on pressure but it is relative, not absolute.
Primary lividity pattern fades away on moving a body and a new secondary pattern forms - how long is the PMI?
Movement before 6hrs (before well-formed) -> fading of primary and onset of secondary pattern
Primary lividity remains on moving a body but a new secondary pattern still forms - how long is PMI?
Movement after 10hrs (well-formed but not fully fixed)
Primary pattern fixed enough to remain but enough fluid blood to form a new secondary pattern -> dual distribution e.g., front and back
Primary lividity pattern remains on movement of body, no secondary pattern forms - how long is PMI?
Movement after 24hrs (well-formed and fully fixed)
Not enough fluid blood to create secondary pattern
what does contact pallor show in relation to lividity?
contact pallor shows areas of pressure between lividities
within an area of lividity there are some burst blood vessels - what is this called?
punctate hypostasis = burst blood vessels within congested areas of lividity
bright pink lividity is a sign of carbon monoxide poisoning - true or false
FALSE
bright pink: refrigeration, hypothermia
cherry pink: CO
chocolate brown lividity is seen in which deaths?
methaemoglobin (chlorate) deaths
cyanide poisoning causes scarlet lividity - true or false
true
An MI can be confused with normal lividity of the heart - true or false
true
the lividity of the heart mimics an MI with the posterior surface congested and the front pale
slow initial cooling delays onset of putrefaction - true or false
false
slow initial cooling e.g., due to clothing or bedding will hasten putrefaction
Describe the process of putrefaction.
Green discolouration in abdomen RIF Passage of rigor Marbling Skin blisters and slippage Gas production and bloating Loss of hair and nails, liquefaction skeletonisation
2 days into putrefaction process - what change is seen?
green discolouration starting in RIF of abdomen
What causes the marbling sign in putrefaction?
blood vessels are mapped out by bacteria
What part of putrefaction begins at 1 week?
gas production and bloating
methane, H2, H2S, NH3
Ptomains (putrescine, cadaverine) -> sniffer dogs!
How long does skeletonisation take?
normally years
can occur in days if body is in warm environment with insects
Which 2 organs will be softened and honeycombed by gas from internal putrefaction?
liver and brain are softened and honeycombed by gas
Which organs are slow to putrefy?
uterus and prostate are slow to putrefy since more fibrous
Internal putrefaction makes heart look …?
heart is dilated and flabby from internal putrefaction
When can stomach contents be useful for PMI?
useful if time of last meal is known since food typically remains in stomach for up to 3-4hrs
NB. food can persist undigested for several day s following severe trauma (e.g. those in ITU)
blue bottle and greenbottle flies are attracted by smell - true or false
true
Which bacteria is important in the saponification process?
clostridium welchii
The saponification process becomes visible after weeks/months. Where on the body might you see it?
cheeks, breasts, buttocks
mummification is more common in adults vs. children - true or false
false
more common in infants vs. adults
partial mummification can occur in some adults during summer months (fingers and toes normally)
