Electrolyte concentration differences between left and right vitreous humor samples

Understanding electrolyte levels in postmortem samples is critical for forensic investigations. Prior studies have suggested that vitreous humor electrolytes could help estimate time of death. However, inconsistencies in results have raised concerns about reliability. Some reports noted large variations between eyes, but the source of this variability remained unclear. Researchers have long debated whether these differences stem from biological factors or sample handling. This uncertainty has limited the practical use of vitreous electrolytes in forensic contexts. A key challenge is distinguishing true physiological changes from analytical errors. The current study aims to clarify the extent of between-eye variability. It also evaluates whether this variability affects the utility of potassium as a time-of-death marker. By focusing on methodological accuracy, the research addresses a critical gap in forensic science.

The study aimed to assess the reliability of electrolyte measurements in vitreous humor samples from both eyes. Researchers wanted to determine if between-eye differences were consistent or if they introduced errors. They focused on sodium, chloride, and potassium, which are commonly used in postmortem analysis. The goal was to evaluate whether these differences could be attributed to sample handling or natural variation. By categorizing cases based on potassium levels, the team sought to isolate the effects of putrefaction. The study also aimed to test the precision of ion-specific electrode systems. This approach allowed for a more controlled comparison of electrolyte values. Ultimately, the researchers hoped to improve the accuracy of time-of-death estimation using vitreous humor.

The study analyzed 200 medico-legal autopsy cases using an ion-specific electrode system. Researchers measured sodium, chloride, and potassium in paired vitreous humor samples. Cases were grouped based on potassium levels to reflect putrefaction stages. Sodium and chloride levels were compared between eyes to assess variability. The team calculated mean values and standard deviations for each electrolyte. They also evaluated the percentage of cases outside instrument accuracy. Data were categorized into three groups based on potassium concentration thresholds. This method allowed for a systematic comparison of between-eye differences.

The average sodium concentration across all cases was 148 mM/L with a standard deviation of 8.9. Between-eye differences ranged from 0 to 8 mM/L, averaging 1.5 mM/L. Only one case exceeded the instrument accuracy range of +/- 3 mM/L. For chloride, the mean was 109 mM/L with a standard deviation of 7.8. Between-eye differences averaged 1.7 mM/L, with 5 cases outside the accuracy range. Potassium showed greater variability in non-putrefied cases. The average between-eye difference was 0.37 mM/L, but this represented 3.3% of the mean. In non-putrefied cases, differences ranged up to 21.8% of the mean. These findings suggest potassium is less reliable for time-of-death estimation.

The study found that sodium and chloride levels showed minimal between-eye variability. This suggests the methodology is reliable for these electrolytes. However, potassium levels exhibited significant and erratic differences. These variations are not easily explained by biological factors alone. The authors propose that sample handling may contribute to potassium variability. The findings challenge the usefulness of vitreous potassium in estimating time of death. The study highlights the importance of standardized sample collection. It also suggests that prior reports of high variability may reflect procedural errors. Researchers recommend caution when using potassium for forensic time-of-death assessments.