study of sodium level in vitreous humour to estimate since death
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To determine whether vitreous humor sodium levels might be of use in evaluating deaths associated with immersion, samples of vitreous humor were prospectively evaluated at autopsy over a 4-year period from 2006 to 2009. There were 19 cases of saltwater immersion (age range 9-76 years; mean age 44 years; M:F, 2.8:1) and 16 freshwater immersions (age range 2-81 years; mean age 27 years; M:F, 2.2:1). In the group of saltwater drownings, vitreous humor sodium levels were elevated, ranging from 145 to 184 mM (mean = 160.2 ± 9.9 mM), and in the cases of freshwater drowning, the levels were reduced, ranging from 73 to 148 mM (mean = 129.8 ± 17 mM; p < 0.0001). Alterations in electrolyte levels may have been because of hemoconcentration or dilution from electrolyte fluxes in the lungs, or from passive diffusion during immersion. This study has demonstrated that vitreous sodium level is an easily performed test that may be a useful adjunct to the investigation of possible immersion deaths.
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Answer:
Vitreous fluid is ideal for postmortem chemical analysis, as it is relatively isolated from blood and other body fluids that are affected by postmortem changes such as redistribution and hemoconcentration. It also resists putrefaction longer than other body fluids, although it is not entirely immune to it.