BIOCHEMICAL CHANGES AFTER DEATH AND POST-MORTEM CLOCK BLOOD OCULAR FLUID & CSF

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Biochemical Changes After Death.

These help in various ways,
1. When injury is not present, and autopsy reveals no significant anatomic or pathological abnormality,

2. They also help in evaluation of physiological effect of a recognizable anatomic lesion,
3. Help in estimation time since death.

Three body fluids are important,
BLOOD,
CSF
VITEROUS HUMOUR or OCULAR FLUID

Changes In Blood Biochemistry
Concentration of all blood components changes after death,

FACTORS RESPONSIBLE FOR THESE CHANGES :
Functioning of organ between somatic & molecular death,
Post-mortem action of bacteria & enzymes,
Altered permeability of dying cell membrane.

Changes In Blood Biochemistry
Concentration of all blood components changes after death,
At the time of certain natural deaths, some changes take place in blood, due to altered body functions, like Agonal Acidosis which is associated with,

Marked increase in lactic acid, Non-Protein Nitrogen Over 100 mg %
Increase in Blood Urea Over 75 mg %
Increased Amino Acid Nitrogen Above 12 mg %

ALL THESE CHANGES ARE AS A RESULT OF TISSUE BREAKDOWN.
ph Of Blood
The Ph of blood and tissues fall, i.e.; becomes acidic, due to terminal accumulation of CO2 and Lactic acid after death.
After about 24 hours, due to production of Ammonia from enzymatic breakdown of proteins, ph starts rising & it becomes again Alkaline.

Plasma Chloride
Normal level is 95-105 m.mol/L
Soon after death Chloride in plasma & RBC’s equalize, and becomes 74 m.mol/L
Then the concentration drops due to extracellular diffusion and becomes half i.e.; 37 m.mol/L in 72 hours.
Mgs/dl = 18 m.mol/dl

Mg++
Normal Value is 0.07-1.2 m.mol/L
With the onset of putrefaction, it starts rising and reaches eight times than normal in 72 hours.
K+
Normal value is 3.8 – 5.0 m.mol/L
It starts rising after death, owing to diffusion from vascular endothelium.

Post-Mortem Accumulation Of Various Enzymes In Serum
AMYLASE; 23 – 85 IU/L
LACTIC DEHYDROGENASE : 90 – 250 mU/L
ACID PHOSPHATASE : Up-to 0.7 U/L
ALKALINE PHOSPHATASE : 30 – 95 mU/L
TRANSAMINASE : 5 – 35 mU/L
These enzymes rise in first few hours after death as a result of increased tissue breakdown and this peak activity varies for each enzyme.

Post-Mortem Accumulation Of Various Enzymes In Serum
These enzymes rise in first few hours after death as a result of increased tissue breakdown and this peak activity varies for each enzyme.
Time Of Various Enzymes
Amylase & Phosphatase : 36 – 48 Hours
Transaminase : 48 – 60 hours

Lactic Dehydrogenase : 4th day
Sugar & Urea
Blood Sugar & Blood Urea also rises after death.

Breakdown of liver glycogen results in accumulation of blood dextrose in Inferior Vena Cava & then in Right side of Heart.

Blood sugar rises by more than 300 mg/dL within first 12 hours.

This diffusion does not extend beyond the Heart, as lungs provide an effective barrier.
Examination of peripheral blood might help, if raised more than 200 mg/dL.
Blood Urea concentration can rise also in agonal period to the level of 150 mg/dL, but usually serum level within first 48 hours is never above 100 mg/dL, unless there is an increase in urea concentration during life.
Serum concentration of Urea MORE THAN 300 mg/dL and Creatinine more than 10 mg% undoubtedly indicate renal failure with Uremia.

Cerebro Spinal Fluid
Amount in life is 150 ml,
It starts disappearing in 24 – 48 hours after death.
Time of death cab be estimated with ± 8 hours of actual time
Sample can easily be obtained by tapping Cisterna Magna
In first 12-18 hours after death, it is noted that,
Lactic Acid rise from 15 mg - 200 mg%
Non Protein N from 15 mg – 40 mg %
Amino Acid N from 1 mg - 12 mg %
DUE TO THESE CHANGES THE TIME SINCE DEATH CAN BE ESTIMATED AS,
Amino Acid Nitrogen if is less than 14 mg% - Post-mortem period is Less than 12 hours
Non-Protein Nitrogen, less than 80mg% - Less than 24 hours
Creatinine less than 5 mg% - Less than 12 hours
Phosphorus less than 15 mg% - Less than 10 hours
Ocular Fluid
After death steady rise in K+ if vitreous after death.
There is a linear relationship between K concentration & Post-mortem interval over 100hours after death.
There is a linear relationship between K concentration & Post-mortem interval over 100hours after death.
If the Post-mortem interval is over 100 hours after death, Then
There is a standard error of ± 4.7 hours
3.4 m. equ. / L is the normal
The studies have shown that the rate of increase is 0.17 m. equ. / L/Hour
Ascorbic Acid, Pyruvic Acid, NPN