POST MORTEM CHANGES
Subtopics:
A. Death is usually a process rather than an event. Clinical and molecular death.
Sings of death :
Immediate
Early
Late
Phases of death
Preagony
Terminal phase
Agony
Clinical death
Biological death
Clinical death
Circulatory cessation criteria
Absence of Central pulse (carotid)
Absence of heart sound on repeated prolonged auscultation
Flat ECG
Respiratory cessation criteria
Absence of respiratory movement
Absence of breath sound on chest auscultation
Nervous system cessation criteria
Generalised flaccidity + generalized anesthesia
Dilated pupils , no pupillary light reflex
Absence of response to any pain stimuli
Absence of corneal reflexes
Normal postmortem changes
B. The peri-mortem and immediate post-mortem changes.
Hypoxia
Electrolytes derragements
Lactic acidosis
Rigor mortis
Livor mortis
Algor mortis
C. The early changes: the ‘algor-livor-rigor’ triplets and their role in helping to estimate the time since death.
Algor mortis
Body temperature ( algor mortis )
( 98.6° F - rectal temp )/ 1.5
Livor mortis stages
Hypostasis
Stasis
Imbibition
Rigor mortis stages
Primary relaxation (1-2 hours)
Rigor mortis(2-3 days)
Secondary relaxation (>3 days)
Estimation of time of death
Body warm + non-stiff = <3 hours
Body warm + stiff. = 3-8 hours
Body cool. + Stiff. = 8-36 hours
Body cool + non-stiff. = > 36 hours
Cadaveric spasm
Desiccation
Putrefaction (days 4-10)
Cell autolysis (days 10-20 )
Dry decay (days 20-50)
D. The late changes and the ultimate disintegration of the organic body into its inorganic components.
Autolysis
Putrefaction
Change in color
Red
Green ( 1-2 days)
Black (3-4 days)
Gas formation
Liquidation of tissue
Loss of organic substances by decay followed by loss of inorganic substances
POST MORTEM CHANGES
Death is usually a process rather than an event. Clinical and molecular death.
Death may be defined as permanent and irreversible cessation if there are interlinked vital systems of the body , called the tripod of life namely - the nervous system , circulatory and respiratory systems.
Death is not an event but a process that can be either rapid or slow depending upon the cause and the deceased person's endurance & state. Some stages are:
Preagony : it contains falling of blood pressure , loss of consciousness, decreased metabolism.
Terminal phase - blood pressure and respiration are reduced , function of the nervous system deteriorates.
Agony - further fall of the blood pressure and cessation of breathing and a sudden return of life ( the last spark of life) , steep reduction of all vital functions and progression to clinical death
Clinical death also called somatic or systemic death means complete and irreversible stoppages of vital functions .it results loss of sensibility and ability to move the body.It may be confused with suspended animation which is a condition in which the vital functions of the body are at such a low level that they cannot be appreciated by clinical examination.it can be performed voluntarily by some yogis for few minutes and is involuntary during drowning , electrocution , heat strike etc. the cells of the tissue are still alive and die progressively at different rates . Muscles still respond to the electrical stimuli .Organs can be removed for transplantation. It is this organ transplantation which makes the death to be defined clearly . A living person cannot be used for organ transplantation.he /she must be declared dead before becoming an organ donor.
Molecular death refers to cessation of cellular respiration and metabolism of the body tissue which is followed by progressive disintegration of the tissue.in absence of perfusion and ventilation of the organs , different tissues die at different pace.organs are not viable since the tissues have already died so organ transplantation is useless yet keratoplasty can be performed.
The peri-mortem and immediate post-mortem changes.
The perimortem changes usually starts when both circulation and respiration ceases.After the stoppage of these vital functions , lack of oxygen causes adaptive changes which eventually after the irreversible cell injury leads to pathological changes in organs and tissues.The blood circulation tries to centralize the blood pool to brain or say central pooling which causes microcirculation disorders in the periphery.
Hypoxia leads to anaerobic respiration which causes lactic acidosis.The peripheral vessels paralyzes due to lack of oxygen , which eventually leads to decrement of contractile myocardium function and stoppage of heart.
Immediate signs of death include loss of response to stimulus i.e. loss of sensation and voluntary power. The respiratory function stops which is at least more than three minutes. The movement of heart and blood ceases . Absence of heart beat for 5 minutes suggests terminal stage.
The early changes: the ‘algor-livor-rigor’ triplets and their role in helping to estimate the time since death.
Early changes comprise pallor and loss of elasticity of the skin , Wounds caused during life will retain their characteristic feature. The ocular changes include corneal changes like dry , cloudy , opaque changes , loss of ocular reflexes .Fall in intraocular tends eye balls to sink in the orbit . The blood flow in the retina becomes dotted and segmented, which is known as the kevorkian sign . If the eyes remain open after death, the areas of the sclera exposed to the air dry out, which results in a first yellowish, then brownish-blackish band like discoloration zone called TACHE NOIRE.It is seen mostly after 7 to 8 hours after death.
Algor mortis means falling down if the body temperature after death.It is due to imbalance of heat production and heat loss .There are there process which are responsible for the loss of body heat i.e.
Conduction
Convection
Radiation
During the first 1-3 hours , the rate is gradual and the inner core may even rise for a transient time due to glycogenolysis .Then the cooling is rapid after 6-9 hours and inner core temperature falls rapidly. After 15-29 hours , the process becomes slower and eventually the body temperature is almost equal to the surrounding.Different factors like body measurements , surrounding temperature and conditions , posture , clothing ,obesity , emaciation can change the rate of cooling.temperature is recorded by chemical thanatometer which is inserted par rectal.
Postmortem caloricity is a phenomenon where the body temperature of a corpse rises or remains unusually high for up to 2 hours after death instead of falling.
Livor mortis is the bluish purple /purplish red discoloration of the skin of the dependent parts.The cessation of the circulation and the relaxation of the muscular tone of the vascular bed allow simple fluid movement to occur within blood vessels.Dependant filing of blood vessels follows passive settling RBC in the tonless capillaries of Rete Mucosum under the influence of gravity in the lowest areas of the body. Distribution of livor mortis is of forensic interest.The color may vary from deep pink to purple violet. Cherry red is observed in CO poisoning , brick red in cyanide poisoning , dark purplish violet in asphyxia but dark brown in phosphorus poisoning.it disappears after the onset of putrefaction and mummification.pinkis hypostasis is seen in bodies preserved in cold or dying from hypothermia.
Postmortem lividity means discoloration or staining of the skin and organs due to accumulation of fluid (blood) in the dependent parts of the body.it may bkt In forensic science , it is a reliable sign of death. It gives information about the position of the body at the time of death . Time of death can also be estimated but intrinsic and extrinsic factors must be taken into consideration.
Distribution of lividity has medicolegal importance as it can give information about the manner of death.
Confusion may arise if the discolored area is contusion or hypostasis . A small incision on the surface and cleansing it by pouring in with running water differentiate it. The discoloration would not wash off in contusion but gets completely washed in hypostasis.
Rigor mortis is shortening and contraction of muscles that occur after death and result in stiffness and immobilisation of the body. It begins in the anterior portion and progresses in a posterior direction and disappears in the same fashion. Small muscles having precise functions are usually seen first. The action may be quickened. By high temperature, violent exercise or violent muscle contractions.It is very rarely seen in premature infants and slow adolescents.In wasting diseases or great exhaustion as seen in plague , typhoid , TB, cancer , cholera etc. , the onset is fast and disappears soon. But , the opposite happens in diseases like pneumonia , asphyxia and nervous condition.Dry and cold air has a slower onset and disappearance than warm and moist air.
Primary flaccidity lasts for 1-2 hours. It is estimated that rigor takes 12 hours to complete and lasts for about the next 12 hours. Rigor can be tested by putting gentle pressure from one to two fingers.
Cadaveric rigidity or Cadaveric spasm is stiffness of muscles with immediate onset after death. This stiffness, unlike rigor mortis, does not pass through the stage of primary flaccidity.it is seen in dead bodies died at extreme emotional and physical stress as seen in drowning person grasping weeds or person attempting suicide found tightly gripping the trigger.
The late changes and the ultimate disintegration of the organic body into its inorganic components.
Decomposition is the late presentation of the dead body which includes autolysis and putrefaction. It is the surest sign of death .
Casper’s dictum states that if all other factors are equal, then, when there is free access to air, a body decomposes twice as fast as if immersed in water and eight times faster than if buried in earth. Temperatures are usually lower in water than on land.
Autolysis refers to autodigestion due to intracellular enzymes. It is not accompanied by gas release. Tissue having high enzymatic activity and warmth lyses faster than the tissue having low enzyme content.it is usually seen first in pancreas.
Putrefaction includes the final disintegration of soft tissue by the microorganisms ( Clostridium perfringens, staphylococcus sp. , streptococcus sp. , Bacillus sp. ) . The first sign includes the colour changes viz. A green discoloration over Right Iliac fossa due to sulph-methohemo globulin. Foul smelling gases are developed and released .The gases trapped causes blisters , shifting of postmortem staining , expulsion of gastric contents and evacuation if feces , uterine prolapse , bursting of thoracoabdominal cavity , floating of drowned body etc.Saprophytic Insects like maggots appears and eventually the whole body leads to colliquative necrosis. The mucous membrane of the larynx and trachea are first decomposed while the non gravid uterus and prostate gland are the last one due to fibrous tissue. Other late changes includes :
Adipocere formation which is a chemical change in the fat, which is hydrolyzed to a waxy substance not like soap and is commonly observed in bodies found in wet conditions.
Skeletonization means decomposition and disappearance of the soft tissue. It depends on ambient temperature , insect colonisation , scavenger activity. It occurs quickly in a body on surface than a body buried.generally it completes within two years.
Mummification is observed in the body in dry conditions which may be natural ( climatic) or artificial ( microenvironment) . They are dry and leathery and often brown in color.
The blood profiles are usually deranged after death by the hemolysis and osmotic changes.The vitreous humor can be the most useful chemical estimation for time of death estimations, electrolytes derangement , hydration status , starvation profile etc.