Postmortem Hypostasis – It is usually of two kinds of coloration, that is, This is the bluish-purple or purplish-red (due to deoxyhaemoglobin) discolouration, which appears under the skin in the most superficial layers of the dermis (rete mucosum) of the dependent parts of the body after death, due to capillo-venous distention.
It is also called postmortem staining, subcutaneous Postmortem Hypostasis, livor mortis, cadaveric lividity, suggilations, vibices and darkening of death.
It is caused by the stoppage of circulation, the stagnation of blood in blood vessels, and its tendency to sink by force of gravity. The blood tends to accumulate in the toneless capillaries and venules of the dependent parts of the body.
Filling of these vessels produces a bluish-purple color to the adjacent skin. The upper portions of the body drained of blood are pale. The intensity of the color depends upon the amount of reduced hemoglobin in the blood.
In cases of large amount of reduced hemoglobin before death, the blood has deep purplish-red color. The color of the Postmortem Hypostasis may vary from area to area in the same body.
In the recently dead or dying tissues, oxygen dissociation takes place, which is continued until equilibrium is reached between the tension of the oxygen in the capillaries and the surrounding tissues.
There may also be backward flow of venous blood from the venular end of the capillaries, which adds to the blueness of the blood after death. It is not possible to distinguish the postmortem discoloration from that produced by cyanosis in the living. Therefore, it is not advisable to use cyanosis to describe postmortem appearances.
Development
Postmortem lividity begins shortly after death, but it may not be visible for about half to one hour after death in normal individuals, and from about one to four hours in anemic persons. Dull-red patches of 1 to 2 cm. diameter appear in 20 to 30 minutes to two hours.
These patches then deepen, increase in intensity and become confluent in one to 4 hours to reach maximum extent and intensity within about 6 to 12 hours. In the early stage these patches can be mistaken for bruises.
In doubtful cases, a portion should be removed for microscopic examination. Christison refers to two cases, in one of which two persons were convicted, and in the other three narrowly escaped conviction, upon a mistake of this kind.
Frost erythema, hypothermia induced red- purple spots seen over prominent parts of the body such as shoulder, knee or elbow joints may sometimes be mistaken for hypostatic patches. The areas then enlarge and combine to produce extensive discoloration.
When lividity first develops, if the end of the finger is firmly pressed against the skin and held for a second or two, the lividity at that part will disappear and the skin will be pale or white. When the pressure is released the lividity will reappear.
The plasma tends to cause edema of the dependent parts and contributes to the cutaneous blisters of early putrefaction. In the early stages mottled patches of Postmortem Hypostasis may be seen on the upper surfaces of the body, especially the legs due to uneven dilatation of the vascular bed. These patches soon join together and slide down to the dependent parts.
It is usually well developed within four hours and reaches a maximum between 6 to 12 hours (primary lividity) and persists until putrefaction sets in. It is present in all bodies, but is more clearly seen in bodies of fair people than in those of dark.
It may not be appreciated in old and anemic persons. If the body is moved within few hours after death, patches of lividity will disappear and new ones will form on dependent parts, (secondary lividity), but lividity to a lighter degree remains in the original area, due to staining of the tissues by haemolysis (complete shifting). This may take from a few minutes to up to one hour.
In incomplete shifting, after turning the body over, lividity appears slightly in the downward facing parts. Non-displacement and non-shifting of lividity is due to haemo-concentration by loss of fluid which penetrates the wall of those vessels related to the hydrostatic pressure.
It is intense in asphyxia, where the blood may not readily coagulate, and in cases of sudden death with a short agonal period and a great circulating blood volume.
It is less marked in death from hemorrhage, anemia and wasting diseases due to reduced amount of blood and pigment. It is less marked in death from lobar pneumonia, and other conditions in which the blood coagulates quickly. Sometimes, bluish Postmortem Hypostasis becomes pink along the upper part of the horizontal margin, the lower parts remaining dark. This is due to the hemoglobin being oxygenated where the erythrocytes are less densely packed in the upper layers of postmortem hypostasis.
The extent and the time of appearance of lividity
If mainly depends upon :
(1) the volume of blood in circulation at the time of death, and
(2) the length of time that the blood remains fluid after death. Hypostatic congestion resembling postmortem postmortem hypostasis may be seen a few hours before death in case of a person dying slowly with circulatory failure, e.g. cholera, typhus, tuberculosis, uremia, morphine and barbiturate poisoning, congestive cardiac failure, deep coma, and asphyxia.
In such cases, postmortem hypostasis will be marked shortly after death. If death has been taking place slowly over a period, early hypostases may be present before death has actually occurred, especially when the affected part is already engorged.
The distribution of P.M. postmortem hypostasis
The distribution of the stain depends on the position of the body.
First – In a body lying on its back (supine) it first appears in the neck, and then spreads over the entire back extending up the flanks and sides of the neck, with the exception of the parts directly pressed on, i.e. occipital scalp, shoulder blades, buttocks, posterior aspects of thighs, calves and heels.
Any pressure prevents the capillaries from filling, such as the collar band, waist band, belts, wrinkles in the clothes,etc. and such areas remain free from color and are seen as strips or bands called vibices.
This is also caused by pressure of one area of the body with another; in which case “mirror image” blanching may be seen (contact pallor, contact blanching). Such pale areas should not be mistaken for marks due to beating, or when they are present on the neck, due to strangling.
Postmortem hypostasis is usually well-marked in the lobes of the ears and in the tissues under nails of the fingers. As the vessel walls become permeable due to decomposition, blood leaks through them and stains the tissues.
At this stage, postmortem hypostasis does not disappear, if finger is firmly pressed against the skin. The pattern of lividity may be modified by local changes in the position of the body , e.g., if the head is turned to one side and slightly flexed on the neck for some hours after death blood may gravitate into a linear distribution determined by the folds formed in the skin and subcutaneous tissues. If such a body is examined after the neck has been straightened, the linear discoloration of the stains may be mistaken for marks due to beating.
Second – If the body is lying in prone position, the lividity appears in the loose connective tissues in front, the color is intense and Tardieu spots are common. Sometimes, the congestion is so great that minute blood vessels are ruptured in the nose, and cause bleeding.
In persons who die in prone position, petechiae, ecchymoses and cutaneous blood blisters may develop after death, in areas of deep postmortem hypostasis especially in the shoulders or over the chest, which may be mistaken for asphyxial death.
In sudden infant death syndrome and in drunken persons and epileptics who die face down on a pillow or other surface, white areas are often seen on the face around the nose and mouth due to pressure against the supporting surface.
This should not be mistaken for suffocation. Circulatory stasis in the aged, and sometimes the effect of cold, may resemble the effects of violence. Such marks are usually found on ears, shins, forearms and hands, where the circulation is comparatively poor and the skin is exposed.
Third – If the body has been lying on one side, the blood will settle on that side, and if lying on back the staining will be seen on the back.
Fourth – If the body is inverted as in drunken persons who slide out of bed, postmortem hypostasis will appear in the head and neck. The eyes may suffuse, and numerous hemorrhages may appear in the conjunctiva and hypostatic areas. This may give rise to suspicion of suffocation or strangulation.
Fifth – Sometimes, blotchy areas of lividity appear on the upper surface of the limbs due to some irregularity of capillary dilatation at the time of death. The internal jugular veins are markedly engorged due to the blood which has drained from the head. This blood cannot drain away below due to the heart, and the valves in the sub-clavain veins prevent the drainage of blood into the upper limbs. As a result of this, the tributaries of the superficial veins in the neck cannot be effectively drained, due to which isolated areas of lividity may develop on the front and sides of the neck resembling bruises. In certain cases, isolated patches of lividity remain separate from the large areas of lividity resembling contusions.
Sixth – If the body has been suspended in the vertical position as in hanging, postmortem hypostasis will be most marked in the legs and hands, and if suspension be prolonged for a few hours, petechial hemorrhages are seen in the skin.
Seventh – In drowning, postmortem staining is usually found on the face, the upper part of chest, hands, lower arms, feet and the calves, as they are the dependent parts. If the body is constantly moving its position, as after drowning in moving water, the staining may not develop.
Until recently it was though that fixation of p.m. postmortem hypostasis was due to clotting of blood in blood vessels, but it is not correct.
The physical factors for fixation of p.m. staining are:
(1) Blood cannot pass out of the capillaries after formation of postmortem hypostasis.
(2) Rigor mortis obliterates the big vessels, and as such the blood cannot pass through these vessels to settle in venules and capillaries in a new area.
(3) After full development of rigor mortis, venules and capillaries are compressed and almost empty and cannot be easily distended by the resettling blood. Postmortem hypostasis becomes fixed when blood leaks into the surrounding soft tissues due to haemolysis and breakdown of blood vessels. This usually occurs in 6 to 12 hours or more, but the condition of blood at the time of death exerts a considerable influence. Fixation occurs earlier in summer and is delayed in asphyxial deaths and in intracranial lesions. Some authors are of the opinion that hypostasis does not get fixed.
Calorimetry shows an increasing paleness of the postmortem hypostasis between 3 to 5 hours, from a wavelength of 575 nm at 3 hours at an average rate of 2 nm per hour. Vanezis claims that there is a linear relationship between the fading color of the hypostasis and time during the first 24 hours, after which the relationship in unpredictable.
Tiny, often spot-like, sometimes confluent oval to round, bluish-black hemorrhages (death spots, postmortem ecchymoses), are exclusively limited to areas of postmortem hypostasis as a result of mechanical rupture of subcutaneous capillaries and venules. They are seen commonly in the back of the shoulders and neck, and sometimes on the front of the chest, even when the body is lying on its back. They are common in cyanotic congestive types of death, and appear more prominent with the increase in postmortem interval, and may blacken the face and skin. They are more prominent when the body lies with the head downwards,
Postmortem hypostasis may be sparse or even absent in deaths where considerable blood loss of at least65% of the circulating blood volume in adults and 45% in infants, occurs before death due to trauma.In severe anemia lividity will be absent.
In asphyxia, the color of the stains is deeply bluish-violet or purple. A brownish postmortem hypostasis may be seen in methaemoglobinaemia and rarely a bronze color in Clostridium perfringens septicemia usually associated with septic abortion. In septic abortion from Cl. Welchii, greenish-brown color is seen. A bright pink color is seen in hypothermia and bodies taken from cold water, and in refrigerated bodies as the wet skin allows atmospheric oxygen to pass through, and also at low temperatures hemoglobin has a greater affinity for oxygen. This may be most marked over large joints and dependent areas. Refrigerated bodies may also assume a pink color. In mummification, lividity may turn from brown to black with drying of the body.
Infection combined with disseminated intravascular coagulation sometimes causes blotchy purplish, red or pink rashes which may be mistaken for bruises or abrasions.
Internal postmortem hypostasis
When a body is in supine position, hypostasis is seen in the posterior portions of the cerebrum and cerebellum, the dorsal portions of the lungs, posterior wall of the stomach, dorsal portions of the liver, kidneys, spleen, larynx, heart, and the lowermost coils of intestine in the pelvic cavity. Postmortem hypostasis in the heart can simulate myocardial infarction, and in the lungs it may suggest pneumonia; dependent coils of intestine appear strangulated.
Color changes in Poisoning
The hypostatic areas have distinct color in certain cases of poisoning, e.g.
(1) In carbon monoxide poisoning, the color is cherry-red.
(2) In hydrocyanic acid poisoning and sometimes in burns the color is bright-red.
(3) In poisoning by nitrites, potassium chlorate, potassium bicarbonate, nitrobenzene, acetanilide, bromates, and aniline (causing methaemoglobinaemia) the color is chacolate or copper brown.
(4) In poisoning by phosphorus the color is dark-brown or yellow.
(5) In poisoning by hydrogen sulphide, the colour is bluish-green.
