Vitreous humor is a fluid that is relatively well protected from postmortem degradation and contamination. Due to its postmortem stability, vitreous humor has high utility in forensic pathology. Vitreous humor biochemical constituents, especially potassium, have been widely used in the postmortem interval (PMI) estimations. The time dependant rise of vitreous potassium levels in the postmortem period has been considered to be helpful in PMI determinations. The relative stability of vitreous biochemistry is useful in assessing the antemortem metabolic status and in predicting the antemortem serum biochemistry of an individual. However, the validity of vitreous biochemistry in forensic applications has been questioned in light of the reported concentration differences of various biochemical constituents in the same pair of eyes at identical PMI. This study hypothesized that the concentration of vitreous biochemical constituents in the same pair of eyes change at the same rate and this change that occurs in a time dependent fashion may be utilized in accurately estimating the PMI. It was further hypothesized that postmortem vitreous humor biochemistry closely mimics antemortem serum biochemistry and may be a useful aid in establishing a postmortem diagnoses of hyperglycemia.
To test these hypotheses, vitreous humor samples were collected from a total of 103 autopsies (Female, 35 and Male, 68; Mean Age ± SD, 60.6 ± 17.6) conducted at Royal University Hospital morgue between January 2003 to February 2005. In 61 of these subjects, the precise time of death was known. Right and left eye vitreous humor samples were collected separately through a scleral puncture at the lateral canthus. Most of the biochemical analyses were carried out immediately post-extraction. After centrifugation, the supernatant of the fluid were analyzed for sodium, potassium, chloride, calcium, magnesium, urea, creatinine, glucose and lactate on an LX-20 Analyzer (Beckman-Coulter). Osmolality was measured on an Osmometer model 3900 (Advanced Instruments Inc.). Vitreous humor hypoxanthine and xanthine were analyzed using a colorimetric method (Amplex® Red Xanthine/ Xanthine Oxidase Assay Kit, Molecular Probes Inc.). Vitreous humor lipid hydroperoxides were measured using the Ferrous Oxidation in Xylenol Orange assay version 2 (FOX 2). The data was statistically analyzed by paired t-test, linear regression analysis and Mann-Whitney test using Statistical Package for Social Sciences (SPSS) for Windows version 13.0.
The results of this study indicated that there were no significant between-eye differences for all of the vitreous biochemical constituents that were studied. It was observed that there was a significant correlation between vitreous potassium (R, 0.731; P, <0.0001), hypoxanthine, (R, 0.450; P, <0.0001), xanthine (R, 0.590; P, <0.0001), lactate (R, 0.508; P, <0.0001), calcium (R, 0.33; P, <0.01) and PMI. The corresponding formulae derived from the linear regression equations to estimate PMI were for potassium (6.41 (K+) 46.25), hypoxanthine (0.32 (Hypoxanthine) 60.94), xanthine (0.14 (Xanthine) 50.08), lactate (5.21 (Lactate) 27.69) and calcium (200 (Ca2+) 380.4). On a comparison of the actual PMI and the estimated PMI calculated using the formulae derived from the linear regression correlationship, it was found that the lowest standard deviation and the highest correlationship was obtained for vitreous potassium. The mean paired actual and estimated PMI values were significantly correlated for potassium (P, <0.0001), hypoxanthine (P, <0.0001), xanthine (P, <0.0001), lactate (P, <0.0001) and calcium (P, <0.01). Only vitreous potassium along with lactate and xanthine were significantly correlated with PMI in the same linear regression model. It was found that there was a highly significant correlation between antemortem serum and postmortem vitreous urea (R, 0.967; P, < 0.0001) and antemortem serum and postmortem vitreous creatinine (R, 0.865; P, <0.0001) concentrations. There was a significant difference (P, <0.05) between the postmortem vitreous glucose levels in the diabetic subjects as compared to the non-diabetic subjects. Vitreous lactate and lipid hydroperoxide levels did not exhibit any significant differences in these two diagnostic subgroups.
The results of the present study suggest that the previously reported between eye differences for various vitreous biochemical constituents in the same pair of eyes are insignificant so far as forensic applications are concerned. Vitreous potassium is a useful biochemical marker for PMI estimations. Vitreous hypoxanthine, xanthine, lactate and calcium are all significantly correlated with PMI and if used in conjunction with vitreous potassium may possibly enhance PMI estimations by narrowing the error margin. The knowledge of vitreous urea and creatinine levels are a useful index in predicting the antemortem metabolic and renal status of the deceased subject.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:SSU.etd-08032005-104652 |
| Date | 04 August 2005 |
| Creators | Mulla, Amith A |
| Contributors | Qureshi, Mabood, Prasad, Kailash, Massey, K. Lorne, Kanthan, Rani, Kalra, Jawahar (Jay), Saxena, Anurag |
| Publisher | University of Saskatchewan |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-08032005-104652/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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