Postmortem Changes- Immediate and Early

 

Postmortem changes
 

1. Immediate changes: (i) Unconsciousness and loss of reflexes (ii) Permanent cessation of cir­culation (iii) Permanent cessation of respiration.

2. Early changes: (i) Eye changes (ii) Skin changes (iii) Muscular flaccidity (iv) Postmortem lividity (v) Cooling of the body (vi) Rigor mortis.

3. Late changes: (i) Putrefaction (ii) Adipocere (iii) Mummification.
 

Immediate changes
Unconsciousness and Loss of Reflexes
There is loss of consciousness and spinal reflexes with no response to painful stimuli.
Permanent Cessation of Circulation and Respiration
This is ascertained by the careful examination of heart and lungs by stethoscope for 5 minutes that is repeated at short intervals.
 
Early changes
 Changes in the eyes
1.Changes in cornea: After death, the eyeballs become softened, cornea loses its luster, and the corneal reflex is lost. The cornea becomes hazy and opaque.
2.Tache noire de la sclerotique: It appears after the passage of few hours to 2 days after death. It is believed to form due to the desiccation of tissues as it is formed only when the eyelids remain open after death. Tache noir is triangular and is present over cornea, often outside the globe. Base of tache noir is at corneoscleral junction (limbus) and apex is diverted towards canthus of eye.
 

  
                  Tache noire de la sclerotique

 

3.Changes in pupil: The pupils usually assume a mid-dilated position that is the relaxed neutral position of the pupillary muscle, though they may alter in position later due to rigor.

4.Intraocular tension: Intraocular tension beco­mes 14 mm of Hg immediately after death from the nor­mal value of 14-25 mm of Hg and by the end of 2 hours it becomes zero.

5.Ophthalmoscopic examination of retinal vessels: The blood columns of the retinal vessels show fragmentation after death. This is the well-known ‘cattle trucking or Kevorkian sign’ of blood in the retinal vessels, when loss of blood pressure allows blood to break up into segments, like trucks in a railway train.
 

Cattle trucking or Kevorkian sign

 

6.Biochemical changes: 

The vitreous humor is considered the best fluid as it is unaffected by contaminants and is easy to obtain without distorting any body part. Besides potassium, the levels of vitreous sodium, vitamin C, etc. are helpful in estimating the time since death. The levels of enzymes like lactic dehydro­genase (LDH) and glutamic oxalic trans­aminase also increases after death.

Changes in the Skin

The skin becomes pale due to drainage of blood from small vessels and appears ashy white after death. Post­mortem staining is of pinkish or cherry red appea­rance in carbon monoxide poisoning and pinkish  in dead bodies left in cold storage.

Muscular (Primary) Flaccidity

At about the time of death all the muscles of the body relax and lose their natural tone. As a result, the jaw drops, the thorax collapses, and the limbs fall quite loose. This is known as primary flaccidity. This relaxation of the muscles is due to high ATP content that permits splitting of the actin-myosin cross bridges.

Postmortem cooling of the body (Algor mortis)

This fall of body temperature after death is due to radiation and convection. When body lies in a cool atmosphere, conduction also plays a role. The surface of the body cools more rapidly than the interior.

The ideal method to note the body temperature is by recording the visceral temperature. The visceral temperature is recorded by making a small midline incision in the peritoneal cavity and placing the bulb of thermometer in contact with the inferior surface of liver and taking the temperature in situ. Alternatively, the thermometer is inserted this much deep in the rectum enabling recording the temperature of the inner core of the body.

Variations of rectal temperature

Low rectal temperature: Rectal temperature of 32o-34.5oC may be observed in (i) Cholera (ii) Long periods of exposure to cold (iii) Conges­tive cardiac failure and (iv) Cases of severe collapse.
Elevated rectal temperature: Rectal tempe­rature is elevated in (i) CO poisoning (ii) Coronary thrombosis (iii) Ruptured aortic aneurysm (iv) Heat stroke (v) Pontine haemorrhage (vi) Infections (vii) Asphyxial deaths.

 

Postmortem Lividity (Hypostasis, livor mortis, post­mortem staining, cadaveric lividity, suggillations, vibices)

Postmortem livi­dity is the bluish-purple discoloration, which appears under the skin of the dependent parts of the body after death due to capillovenous distention because of accumulation of blood. Postmortem lividity is produced because of: 

(i) Stoppage of circulation (ii) Stag­nation of blood in blood vessels (iii) Tendency of the blood to sink by force of gravity.

The distribution of postmortem lividity is patchy to start but with passage of time, it gradually enlarges to cover all the dependent areas of the body.

Hypostasis appears on dependent parts of body except pressure areas and its location and distribution depends upon the position of the body after death. In supine position, the postmortem staining appears on the back while in deaths due to hanging, it is well developed on the lower part of legs and forearms.
Any pressure prevents the capillaries from filling such as belts; wrinkles in cloths etc. and such areas remain free from color and are seen as strips or bands called vibices. Contact pallor also caused by pressure of one area of the body with another, in which mirror image blanching will be seen.

Time taken to develop: It is well developed within 4 hours and the maximum development occurs within 6-12 hours after death of the person.

Fixing of Hypostasis: When the body remains static for 6-8 hours at one place, the postmortem lividity will fix, and it is due percolation of RBCs from the capillaries and staining of the nearby tissues.

Shifting of Hypostasis: This is since it takes about 6-8 hours for the stain to fix and prior to that period, the staining can keep on shifting as the blood remain fluid.

Cause of death: By examination of the color and pattern of the staining.

Medico legal aspects of Hypostasis: (i) Early sign of death, (ii) It is suggestive of the time passed since death, (iii) It can signify cause of death, (iv) Distribution of hypostasis helps in deciding the position of body after death, (v) Postmortem lividity with haemorrhage (hemorrhagic lividity) in glove and stocking pattern will be seen prolonged hanging. In supine position the muscles of calf and buttocks remain flat due to loss of muscle tone (Contact flattening). Once hypostasis has appeared these areas are more easily delineated because they are pale. The lividity will be present on dependent parts except pressure areas (Contact Pallor)

Differences between postmortem lividity and congestion
Postmortem lividity	Congestion
Irregular and occurs on dependent parts	Uniform all over organs
Mucous membranes are dull and lusterless	Normal
Stomach and intestine when stretched show alternative stained and unstained areas according to the position of folds and coils	Uniform staining
No inflammatory exudates	Inflammatory exudates are present

 

Rigor Mortis/Postmortem rigidity/Death stiffening/Cadaveric rigidity

Rigor mortis is postmortem stiffening of voluntary and involuntary muscles of the body that develops at variable periods after death and succeeds the state of primary muscular flaccidity. When rigor mortis is developed fully in the joints, they become fixed, extended, or flexed depending on the position of the body at the time of death. Once rigor mortis is broken down by force, it does not reappear. However, when it is not bro­ken it passes off spontaneously and is fol­lowed by a phase of secondary muscular relaxation. Rigor mortis first appears in involuntary muscles like heart. The chemical changes which occur in muscles immediately after death are like those which occur in living muscle. The initial muscle contraction requires immediate energy being supplied by ATP, which is converted to ADP. Rigor mortis starts when muscle ATP is 85% and it’s maximum when its 15 % of the normal level. Terminal phosphate radical in ATP is rich in energy. Phosphagen (crea­tine phosphate) donates phosphate to ADP and ATP is restored. Phosphate freed from ATP is utilized in a complete phosphorylation process, which is necessary for conversion of glycogen to lactic acid. The new energy rich phosphate bonds formed by this process are initially used to resyn­the­size ATP from ADP. Therefore, the fall of level of ATP is related to the onset of rigor mortis.
  

 

Mechanism of rigor mortis
Rigor mortis is commonly described as commen­cing in the neck muscles and lower jaw and then spread­ing to upper limbs, thorax, abdomen, and the pelvis and lastly to the lower limbs. It develops quickly in small masses of muscles than larger muscles. Therefore, variation in different sizes of joints and muscles controls its development. It appears from proximal (bigger joint) to distal (smaller joint). This hypothesis of Shapiro is impor­tant from medico legal point of view as it empha­sizes the difficulty of estimating postmortem interval from distribution of rigor mortis. Rigor mortis takes 12 hours to deve­lop, remains for further 12 hours, and takes next 12 hours to pass off. The body is kept in supine position on the autopsy table and the pathologist tries to lift the leg by putting the hand above the knee joint under the thigh. The knee joint will not flex due to stiffness once rigor has developed. In the same way, there will not be any flexion movements at the elbow joint.
Nysten's rule: It is named after a French pediatrician, Pierre-Hubert Nysten. It describes the sequential onset of rigor mortis in the various muscle groups. The basic sequence of the rigor mortis in body begins from the head down the body, in the order. The rule does not occur in all cases, as described.
Conditions that Influence rigor mortis
1. Environmental temperature: When the environ­mental temperature is high, onset of rigor is rapid, and the duration is short.
2. Degree of muscular activity before death: After prolonged muscle activity and in certain dis­orders, there is rapid onset of rigor mortis, and the duration is short.
3. Nature of death: The development of rigor mortis varies with the nature of death such as:
(i) During exhaustion, in wasting disease like TB, cancer and cholera and in violent deaths such as deaths due to firearm, electrocution and light­ning, it is of rapid onset and of short duration.
(ii) In conditions such as apoplexy, severe haemorrhage, pneumonia, and nervous disease the onset of rigor is delayed.
(iii) It may not appear at all in deaths due to septicemia.
Medico legal aspects: (i) Early sign of death (ii) Time since death can be calculated by ascertaining the presence of rigor mortis in various muscle groups of the body.
Cadaveric Spasm (Postmortem spasm, instantaneous rigor mortis, cataleptic rigidity, or instantaneous rigidity)
A rare form of muscular stiffening that occurs now of death and persists into the period of rigor mortis. Cadaveric spasm can be distinguished from rigor mortis as the former is a stronger stiffening of the muscles that cannot be easily undone, while rigor mortis can. The cause is unknown but is usually associated with violent deaths under extreme physical circumstances with intense emotion.
 

Differences between rigor mortis and cadaveric spasm
Rigor Mortis	Cadaveric Spasm
Starts by 1-2 hours of death and fully established by 6 hours	Instantaneous
Involves involuntary and voluntary muscles	Usually involves a group of muscles
Preceded by primary flaccidity	No primary flaccidity
No predisposing factor	Seen in sudden violent deaths
It is because of depletion of ATP	Exact mechanism is not known
Time since death can be calculated	Manner of death can be decided
Can be broken with moderate force	Greater force is required to break it
Muscles do not respond to electrical stimuli as molecular death has set in	Muscles in this state may respond to electrical stimuli as molecular death has not yet set in

 
Heat rigor (heat stiffening)
Heat rigor occurs in circumstances when death has resul­ted due to fire in multistory buildings, aircraft accidents, motor car accidents, burning etc. Rigor mortis does not develop in the muscles that have undergone heat stiffening, but heat stiffening can occur after rigor mortis. In heat rigor, shortening of the muscles occurs resulting in flexion of the joints of the upper and lower limbs called pugilistic attitude.
 
    

                                            
 Pugilistic Attitude
 
Cold stiffening
Muscles become rigid and hard, and the condition simulates rigor mortis. There is extreme coldness of the body and when the joints are forcefully flexed, crackling of the ice of the synovial fluid in the joints occurs.
Gas stiffening
Gas stiffening occurs in bodies with advanced state of decomposition when a false rigidity is produced due to accumulation of gases in the tissues. The face is swollen, eyes bulge out, abdomen distended, and the scrotum is swollen.
Secondary Relaxation
Muscles become soft and flaccid due to breaking down of actomyosin links.
 

Differences between rigor mortis, heat, and gas stiffening
Rigor mortis	Cold stiffening	Heat stiffening
It is due to loss of ATP with rise of lactic acid	Exposure of dead body to freezing temperature below 3.5oC with solidification of body fats, fluids, and muscles	Exposure of dead body to raised temperature above 65oC
Onset is gradual and progress in a definite order	Quick onset and progress in not in fixed or definite order	Very rapid and no definite order
On thawing after cold stiffening, it appears rapidly and so also disappears. It does not appear after heat stiffening	If body is exposed to freezing temperature before onset of rigor, rigor mortis will be delayed	It can occur in muscles under influence of rigor mortis and body may assume pugilistic attitude with shortening of muscles
It gives an idea about time since death	It suggests the condition in which the body lay after death	It suggests circumstances leading to death
It terminates into state of putrefaction	After thawing rigor mortis will appear but if freezing surrounding persists the body will remain in the state of cold stiffening	The state will merge into stages of putrefaction in due course of time without rigor mortis setting in