| The estimation of the time since death is one of the key problems in forensic medicine. It could be called the estimation of postmortem interval (PMI) as well. It is also one of the important problems to be solved for the forensic autopsy. To estimate the PMI correctly is great value to detect a crime and to judge a case in the forensic medicine.The current methods to estimate the PMI mainly include algor mortis, supravital reaction, digestive concentrations in the stomach and intestines, DNA degradation, enzymehistochemistry and histological observation and entomology.The methods mentioned above were mainly semi-quantitative. Their results were too subjectively affected and the applications were limited as well. However, the present method depending on analyzing the changes of chemical compositions of the cadaver body fluid mainly trends to quantitative research that is objective and convenient to be applied. The body fluid mainly contains blood, cerebrospinal fluid and human vitreous humour and so on . Due to the special location in the eyeballs, the human vitreous humour are lightly affected by the damage of the cadaver and the outside contamination as well as the environment factors (except the temperature), so this method is the most dependable and it has always been one of the researching focuses for forensic medicine experts.Objectives1. The referrenced values of human vitreous humour are absent in clinical medicine so far. Therefore it is very necessary to survey the chemical compositions of normal human vitreous humour.2. To estimate the PMI with multi-index and set up its separate regression equation so as to analyze comprehensively and try to make the reliability enhance to the highest degree. Thus we could make human vitreous humour be widely used in forensic medicine practices.Methods1. Auto-biochemistry instrument OLYMPUS AU5400 was used to analyze all collected samples.2. Samples of checking the refferenced values of human vitreous humour were taken from the dead body having antemortem healthy data, and the cause of death was all craniocerebral injury.3. The checking sampling of human vitreous humour in different time after death: such human vitreous humour was taken from the dead body whose PMI within 0. 5 to 216 hours.4. Collected data were statistically analyzed using SPSS software.Results1. Referrenced values of chemical compositions of human vitreous humour were as flows: glucose 3.70mmol/L, urea 3.50mmol/L, creatinine 40.41ummol/L, uric acid 41.93umol/L, sodium 144.84mmol/L, potassium 5.70 mmol/L, chlorine 120.41mmol/L,calcium 1. 36mmol/L, magnesium 0.80mmol/L, inorganic phosphorusus 0.32mmol/L, micro-protein 0.19 g/L.2. The levels of chemical compositions in human vitreous humour in different time after death was as follows: The levels of glucose, sodium, chloride, in human vitreous humour were gradually reduced with the time since death; while the concentrations of urea, creatinine, uric acid, potassium, calcium, magnesium, phosphorusus, micro-protein were ascend with the time since death. The concentrations of glucose was reduced to zero in normal tempreture within 24 hours after death. The linear relation between the concentrations of potassium and the PMI was definetely within 72 hours and the equation is as following: Y= -27.40+5.17X, R2=0. 934. Here Y stands for PMI, X stands for the concentrations of potassium in human vitreous humour. Within 171 hours, the linear relation between the concentrations of inorganic phosphorusus in human vitreous humour and PMI was very clear and gradually ascend with the time since death. Its equation is: Y= -2.34+ 29.06X, R2=0.899. here Y stands for PMI, X stands for the concentrations of inorganic phosphorusus.3. The related analysisFrom 0. 5 to 72 hours postmortem, the related coeff ient of PMI and the levels of chemical compositions (such as glucose, urea, creatinine, uricacid, sodium, potassium, chloride, calcium, magnesium, inorganic phosphorusus, micro-protein) in human vitreous humour were respectively the following: -0. 824,0. 765,0. 787,0. 350,-0. 438,0.967, -0.462, 0.420, 0.530, 0.880, 0.153, P<0.01. The positive number here shows that the concentrations of related composition ascend with PMI, the negative number is reverse.4. The analysis of regressionThe stepwise regression equation of PMI within 0. 5-72 hours is: Y=-35.15+6. 05X, R2=0. 957. Here Y stands for PMI and X stands for concentrations of potassium in humam vitreous humour. Y=-27.83+5.49X,-1.35X2, R2=0.960. Y stands for PMI.X, stands for concentrations of potassium in humam vitreous humour. X2 stands for concentrations of glucose in humam vitreous humour. Y=-16. 37+3. 93X.-2. 29X2+5. 36X3, R2=0. 966. Y stands for PMI. X, stands for concentrations of potassium in humam vitreous humour. X2 stands for concentrations of glucose in humam vitreous humour. X3 stands for concentrations of inorganic phosphorusus in humam vitreous humour.Conclusions1. The referrenced values of chemical compositions in the human vitreous humour were provided and the data for clinical and forensic medicine applications were accumulated.2. The results indicated that the concentrations of these chemical compositions including the glucose, urea, creatinine, uric acid, sodium, potassium, chloride, calcium, magnesium, inorganic phosphorusus, magnesium and micro-protein vary with the time since death. Among which the concentrations of potassium and Inorganic phosphorusus in humam vitreous humour appeared best linear relationship with PMI.3. The accuracy for the estimation of PMI would be improved by using the method of stepwise regression and equation of multi-regression.Innovations1. The project was completed by arduously sampling and the valuable data were obtained by hard work. The levels of chemical compositions of human vitreous humour were detected and the referrenced values of normal human vitreous humour were provided to the clinical and forensic medicine.2. The changes of chemical concentrations in vitreous humour for estimating the PMI by means of complex index and comprehensive analysis were suggested.
|
PDF Full Text Request