Vitreous Potassium Research Articles

Can Vitreous Potassium Concentration Predict Postmortem Interval in Cases of Poisoning and Burns? A Cross Sectional Study from a Medical School

Background: Estimation of time elapsed after death remains one of the most important requirements in medico legal autopsies. Time since death (TSD) provides a clue to the investigating officer to institute suitable inquiries to apprehend the person likely to be responsible for crime and to eliminate the innocent ones. Aim: Aim of the current study was to analyze and ascertain the relationship between vitreous K+ concentration and TSD among poisoning and burn cases. We also aimed to derive a formula for determining TSD from changes in levels of vitreous K + concentration. Methods: The present cross sectional study was carried out among the autopsy cases brought to the mortuary of Department of Forensic Medicine and Toxicology of a medical school for the post mortem examination. All the autopsy cases were entailed the collection of vitreous humour for determination of vitreous potassium. Data of all those autopsy cases was analyzed in which cause of death was either poisoning or burns. Potassium levels were quantified in the collected sample by the ion-selective electrode method. Regression and correlation analysis were performed. Results: Data of 72 study subjects belonging to poisoning and burn cases were analyzed. The mean vitreous

Vitreous potassium concentration as a predictor of postmortem interval: A cross-sectional study among poisoning and burns cases at a tertiary care center in rural Haryana

Background: Time since death (TSD) is an important parameter to the forensic expert. Only a few studies are available in the literature to determine the relationship between vitreous K + concentration and TSD, especially among poisoning and burns cases, and thus information on the same is scant. Therefore the present study was planned. Objective: The main objective was to determine the relationship between changes in vitreous K + concentration with increasing TSD among poisoning and burns cases. An additional objective was to derive a formula for determining TSD from changes in levels of vitreous K + in the study subjects. Materials and Methods: In this study, autopsy cases brought to the mortuary of the Department of Forensic Medicine and Toxicology of a tertiary care center were subjected to collection of vitreous humor for the determination of vitreous K + . Data of 36 cases where autopsy confirmed the cause of death as poisoning or burns were included in this study. Determination of K + level in the collected samples was done by the ion-selective electrode method (Biolyte 2000 autoanalyzer). Results: A linear relationship was observed between vitreous K + concentration and TSD in both the eyes. External factors such as seasonal variations and temperature, gender difference, and age had no appreciable effect on the concentration of vitreous K + in either eye. In this study the linear regression equations obtained from potassium concentration (y) versus time (x) for the two groups among poisoning and burns cases were as follows. For right eye: Regression line (y) = -4.932 x + 1.932; for left eye: Regression line (y) = -5.380 x + 1.990. The K + levels were found to increase up to 40 h after death. Conclusion: This study highlighted the usefulness of the relationship between vitreous potassium concentration and TSD in both the eyes. The formula calculated from the current study could prove to be more appropriate as it is based on more reliable tests.

Thanatochemistry: Study of vitreous humor potassium

This study has been carried out to determine the death interval from the biochemical parameter of vitreous potassium. In 308 medicolegal cases vitreous humor was taken and analyzed for potassium with known time of death. There was a linear rise in potassium concentration with increasing death interval. Regression equation was calculated for the same. The study indicates that potassium levels in vitreous for determining death interval are useful and can afford a good method of determining the death interval along with other traditional methods. Also the previously established formulae for estimating death interval from vitreous potassium were also studied.

A Correlation Study between Post Mortem Interval Estimation and Vitreous Potassium Level

A Correlation Study between Post Mortem Interval Estimation and Vitreous Potassium Level

Estimation of Post Mortem Interval by Means of Changes in the Eye-vitreous Humour Potassium Levels

The present study was carried out in Shri. Vasantrao Naik Government Medical College, Yavatmal. The dead bodies brought to the mortuary were used as material for collection of vitreous humour sample from the eyes of deceased. The vitreous analytes have been investigated to establish their correlationship with PMI or time since death. A significant linear correlationship, at various degrees, was seen to exist between PMI and vitreous potassium

A Study of Correlation of Time Since Death with Vitreous Potassium and Sodium-Potassium Ratio

The interval between the death and the time of the examination of the body is known as postmortem interval. The exact time of death cannot be fixed by any method but only approximate range of time since death can be given because there are considerable biological variation in the individual cases. The present study was carried out in the Morgue and the Department of Forensic Medicine and Toxicology, of Shri V. N. Government Medical College, Yavatmal from Maharashtra. The vitreous humor was sampled from about 201 cases subjected to autopsy.

Study of vitreous potassium correlation with time since death in the postmortem range from 2 to 110 hours using capillary ion analysis

The time-dependent postmortem increase of potassium concentration in the eye fluids has been studied since the 1960s. However, important discrepancies on the reproducibility of the phenomenon have hampered the use of this parameter in real cases. In recent years, a new analytical approach based on capillary ion analysis (CIA) has been reported. In the present work, the correlation between vitreous potassium and postmortem interval (PMI) has been re-evaluated by using CIA in a group of 164 cases with PMIs ranging from 2 to 110 hours. The correlation of the two parameters was described by the following regression equation: y = 0.1733x + 2.3008 (x = PMI; y = K(+) concentration); correlation coefficient = 0.962. The re-calculation of PMIs on the basis of this equation provided calculated PMIs with an average error of 5.54 hours (SD = 4.16). However, the percent PMI calculation error decreased with the increase of PMI, becoming acceptable for practical application above 24 hours since death.

Vitreous Humor: Biochemical Constituents in Estimation of Postmortem Interval*,†

Analysis of biochemical constituents of the vitreous humor can be useful in determining the postmortem interval as there is proportionate postmortem rise of potassium and fall in sodium concentration. We studied 120 autopsy cases to determine the utility of potassium, sodium, calcium, and chloride levels, and sodium/potassium ratio in estimating the postmortem interval. There was a linear relationship between vitreous potassium concentration and postmortem interval, whereas an inverse relationship between vitreous sodium/potassium ratio and postmortem interval was noted. Other factors like age, sex, cause of death, season of death, and refrigeration of sample did not influence the vitreous humor potassium values. Using the statistical tools, a new formula was derived to determine the postmortem interval based on the potassium concentration and a review of previous literature is presented. Hence, the findings of this study supported a central role of vitreous humor biochemistry in many postmortem forensic and pathological evaluations.

A study of correlation between vitreous potassium level and postmortem interval

A study of correlation between vitreous potassium level and postmortem interval

Postmortem identification of hyperglycemia

The detection of diabetic coma postmortem requires accurate biochemical analysis. Due to continuous consumption of glucose by surviving cells postmortem, blood glucose levels decrease rapidly. Therefore, vitreous fluid has been used as a substitute in forensic practice, since it has a very low cell count. It has been repeatedly reported that the sum value of vitreous glucose and lactate should be used to estimate the original antemortem blood glucose level, based on the assumption that pre-existing glucose is gradually converted to lactate under anaerobic conditions during agonal phase and the early postmortem period. In this study, we applied a strategy including consistent sampling of vitreous fluid from the centre of both eyes of deceased subjects as soon as possible after arrival at the morgue, and immediate bedside analysis using a blood gas instrument. In total, 3076 cases were included during 2004–2006. We found that, after an initial drop of vitreous glucose during the very early postmortem period, the levels stayed stable for appreciable time postmortem. Analysis of a second sample collected at autopsy 1–3 days later gave similar results ( R 2 = 0.90). In contrast, the vitreous lactate levels showed a steady increase. This implies that the sum value of glucose and lactate increases with postmortem time, as reflected by vitreous potassium level. In fact, a statistically significant difference in the sum value was seen between subjects with potassium below 10 mmol/L ( n = 1086) and above 20 mmol/L ( n = 531), p < .001. In addition, in this large material, we did not identify a single case with circumstantial indication of hyperglycemia that only showed high vitreous lactate. We therefore suggest that vitreous glucose alone should be used to diagnose hyperglycemia postmortem and that the limit of 10 mmol/L should have a good specificity for diabetic coma, which theoretically would equal an original blood glucose value of about 26 mmol/L. As to the methodology, we found that sonication, centrifugation and addition of fluoride to the samples are unnecessary procedures when using a blood gas instrument. The strategy resulted in a doubling of the number of diabetic coma identified at our department compared to preceding period when analysis only was performed on selected cases.

Is there recent progress in the estimation of the postmortem interval by means of thanatochemistry?

Numerous methods have been proposed in the last 60 years for the determination of the time since death by chemical means. Many of them were reviewed by Schleyer in his monograph on the determination of the time since death by means of thanatochemistry about 40 years ago and none of these early methods has gained any practical value since they do not meet the demands in practice (being precise, reliable, giving an immediate result). While the earlier studies were mainly carried out on blood and cerebrospinal fluid (CSF) since the late 60s most investigations have been performed on vitreous humor (VH). This is mainly due to the fact that vitreous humor is topographically isolated and well protected, and thus, autolytic changes proceed slower compared to blood and CSF. The most studied parameter in VH is potassium and even nowadays reports on the postmortem rise of vitreous potassium are published, proposing new analytical methods or statistical evaluations. Chemical parameters studied for the determination of the time since death have to be differentiated according to the underlying process (catabolism, metabolic processes, pure autolysis and diffusion, putrefactive changes). In the present paper, recent studies on thanatochemistry are discussed regarding the underlying process, the analytical methods (for instance H magnetic resonance spectroscopy ( 1H MR spectroscopy), immunohistochemistry), the studied fluid compartment, the statistical evaluation and the precision of death time estimation. The value of chemical methods for the determination of the time since death is up to now very limited. This is supported by the fact that field studies on the reliability and precision of death time estimation by chemical means are still scarce in the literature.

Influence of the nature of an alkali cation on the electrical conductivity of vitreous MePO3 (Me = Li, Na, or K)

The temperature dependence of the electrical conductivity of vitreous lithium, sodium, and potassium metaphosphates is investigated using active electrodes (amalgams of the relevant alkali metals). The decrease in the electrical conductivity in the sequence LiPO3–NaPO3–KPO3 is explained by the fact that the electric current in lithium metaphosphate is carried by lithium ions, whereas the electricity transport in NaPO3 and KPO3 occurs through alkali metal ions together with protons formed upon dissociation of impurity water. The kink observed in the temperature dependence of the electrical conductivity of KPO3 is interpreted in terms of the charge carrier type. It is demonstrated that high-temperature (> 373 K) conduction is provided primarily by migration of potassium ions, whereas low-temperature conduction is due to migration of protons.

No significant differences in the postmortem interval in Myanmar and Japanese using vitreous potassium levels

No significant differences in the postmortem interval in Myanmar and Japanese using vitreous potassium levels

No significant differences in the postmortem interval in Myanmar and Japanese using vitreous potassium levels

Objective : New international criteria for the estimation of the postmortem interval (PMI) in autopsy cases could be useful. At present, there is no published information comparing differences between people of different ethnic origin. To address this, we have carried out an investigation to see if there is any ethnic difference in the postmortem interval in autopsy cases involving Myanmar and Japanese populations estimated using the vitreous potassium (K + ) level in aqueous humor. Results : Estimation of the PMI from the vitreous K + level was investigated using 82 known PMI autopsy samples collected from various sources and backgrounds (e.g., age, sex, cause of death and ambient temperature) from Myanmar and Japanese subjects using a Copenhagen Radiometer (ABL system). The present study shows that raised vitreous K + levels (mean of right and left eyes) from 1 to 60 hr after death are linearly correlated with increased PMI and the regression line follows that of the vitreous K + levels correlated with PMI and show no significant difference between race (Myanmar, r = 0.93 and Japanese, r = 0.91), eyes (right, r = 0.92 and left, r =0.93), sex (male, r = 0.91 and female, r = 0.93) and age ( r = 0.89). The PMI from the vitreous K + levels of Myanmar and Japanese and their 95% limits of confidence was ±13.8 and ±12.7 hr, respectively. Conclusion: The above result shows that measurement of the vitreous K + level of aqueous humor helps in theestimation of PMI and it appears that there is no significant difference between the two ethnic groups studied. In addition, estimation of the vitreous K + level may be a useful international criterion for estimation of the PMIinautopsy cases.

Improved estimation of postmortem interval based on differential behaviour of vitreous potassium and hypoxantine in death by hanging

Many formulae are available to estimate the relation between the potassium ([K +]) and hypoxantine ([Hx]) concentration in the vitreous humour and the postmortem interval (PMI). Typically these have been based on a correlation test and linear regression using the postmortal interval as the independent variable and [K +] or [Hx] as the dependent variable in order to estimate the confidence interval. However, a recent study has shown that a more precise measurement of PMI can be obtained if [K +] is used as the independent variable. The regression lines obtained from the most recent deceased subjects with forensic relevance received for autopsy in the Institute of Legal Medicine are [K +]=5.589+0.174PMI and [Hx]=26.459+3.017PMI, by changing the variables, we obtain PMI=3.967[K +]−19.186 ( R 2=0.688, P<0.001) and PMI=0.172[Hx]+0.170 ( R 2=0.518, P<0.001). In this paper we propose the cause of death as an extra factor which modifies the relationship and gives even greater precision in estimating PMI. In cases of death by hanging the results are considerably improved with [K +]=5.224+0.225PMI and [Hx]=15.161+4.957PMI, respectively, and consequently, PMI=3.631[K +]−17.334 ( R 2=0.818, P<0.001) and PMI=0.153[Hx]−0.368 ( R 2=0.757, P<0.001): the slope is less and the precision is obviously enhanced.

Electrolyte Concentration Differences Between Left and Right Vitreous Humour Samples

Between-eye differences in electrolyte concentrations were studied in 200 medico-legal autopsies using an ion-specific electrode system. Taking the highest of the paired vitreous potassium concentrations, cases < 15 mM/L were classified as biochemically nonputrefied (Cat.1, n = 124), cases 15 to 20 mM/L as early putrefaction (Cat.2, n = 51), and cases > 20 mM/L as biochemically putrefied (Cat.3, n = 25). Mean paired vitreous sodium for all cases (n = 200) was 112 to 173 mM/L (mean 148, standard deviation (SD) = 8.9); between-eye differences were 0 to 8 mM/L (0% to 5.1% of mean), averaging 1.5 mM/L (1%) and with only one case (in Cat.3) outside instrument accuracy (+/- 3 mM/L). Mean paired vitreous chloride for all cases was 73 to 124 mM/L (mean 109, SD = 7.8); between-eye differences were 0 to 9 mM/L (0% to 8.8% of mean), averaging 1.7 mM/L (1.5%) and with 5 of 200 cases outside instrument accuracy (+/- 3 mM/L). Thus between-eye concentration differences of sodium and chloride are tolerable using this methodology. Previous reports of greater variability likely reflect errors introduced by sample manipulation prior to analysis. By contrast, between-eye differences in potassium in Cat.1 cases were 0 to 2.34 mM/L (0% to 21.8% of mean) averaging 0.37 mM/L (3.3%). Significant and erratic between-eye differences in potassium undermine the usefulness of vitreous potassium in estimation of time of death.

Capillary ion analysis of potassium concentrations in human vitreous humor.

Capillary ion analysis (CIA) is a form of capillary electrophoresis which uses the differential electrophoretic mobility of ions to perform a separation of an ionic mixture. Application of this technique for direct detection of potassium concentrations in human vitreous humor was the purpose of this investigation. CIA was performed using a Waters Quanta 4000 Capillary Electrophoresis System with a 745 Data Module using a 75 microm x 60 cm capillary and a run electrolyte of 67.7 mg hydroxyisobutyric acid (HIBA), 52.8 mg 18-crown-6-ether and 64 microL UV-CAT-1 reagent (4-ethylbenzylamine) in a volume of 100 mL water (18 Mohm) with a voltage of 20 kV using ultraviolet absorption detection at 214 nm. Migration times were: ammonium ion, 2.86 min; potassium, 3.24 min; calcium, 3.84 min; sodium, 3.98 min; barium (internal standard), 4.68 min; and lithium, 4.79 min. Correlation coefficients (r) between peak area ratios and concentration ranges of 2.5-144 mmole/L (100-1000 ppm) were from 0.9855 to 0.9999. Coefficients of variation (CV) ranged from 1.45 to 13.8% between days and from 1.38 to 9.43% within-day. Application of this methodology to twenty-five vitreous humor specimens from forensic cases was compared to analysis by ion-specific electrode for potassium concentration. Comparison of CIA to ion-specific electrode analysis of vitreous humor potassium concentrations revealed a correlation coefficient of 0.9642. CIA is applicable to forensic analysis of potassium concentration in forensic vitreous humor specimens. Quantitation of numerous cation concentrations is possible by direct CIA of vitreous humor.

Vitreous humor analysis for selected biochemical parameters from cervids in Idaho.

Vitreous humor and liver samples were collected from hunter-harvested elk (Cervus elaphus) and mule deer (Odocoileus hemionus) in Idaho (USA). Concentrations of calcium, chloride, potassium, sodium, urea nitrogen and selenium were determined and evaluated according to species, age, gender, geographic location, and time elapsed following death. Vitreous humor analysis yielded reliable biochemical information for < or = 96 hr subsequent to the death of the animal. Vitreous potassium concentration changes over time could be used to estimate the time that elapsed following death.

Human postmortem interval estimation from vitreous potassium: an analysis of original data from six different studies

The investigation of the postmortem interval (PMI) by determining potassium levels in the vitreous humor (KV) has been a subject of forensic pathology research for more than a quarter of a century. The numerous studies to date have yielded a variety of linear or piecewise-linear relationships between KV and PMI, i.e., different estimated intercepts and slopes of regression line(s) as well as different reliabilities of these estimates. This lack of agreement is due in part to the variable numbers of cases reported from study to study, differing observed ranges of KV and PMI, and the unaccommodated effects of factors on potassium concentration, including age of subject, amount of urea nitrogen, ambient temperature, and presence of illness. Original data from six of these studies, for a total of 790 cases, are reanalyzed together. The relationship between KV and PMI is not completely linear, and the residual variability of KV as a function of PMI is not constant. Thus, two main assumptions of the simple linear model, linearity and constant variance, are not supported by the data. It is clearly problematic to report statistical summaries such as the slope of an estimated regression line and the reliability of that estimate based on a model with faulty assumptions. Yet even after rescaling the data in an attempt to achieve linearity in the KV-PMI relationship and to stabilize residual variation, the relationship continues to be non-linear and its variability unstable. A new approach is developed for modeling KV and PMI that accommodates non-linearities and changing residual variability. A local regression model, specifically a loess smooth curve, is fitted separately to the data from each of the six studies. The loess smooth curve adapts locally to the changing and possibly non-linear relationship between KV and PMI across their observed ranges. The data from all six studies are then combined to yield a single loess curve with 95% confidence bands. The estimated loess curve and confidence bands are used in an inverse prediction method to construct low, middle and high PMI estimates at given values of KV. The reliability of estimated PMI decreases as KV increases. Although the confidence bands surrounding the overall curve widen in the extreme high end due to there being fewer available data in that region, PMI estimates are more precise over the entire range of KV and PMI than those obtained from any single study alone. A cross-validation procedure provides an independent check of the predictive performance of the method.

Human postmortem interval estimation from vitreous potassium: an analysis of original data from six different studies

The investigation of the postmortem interval (PMI) by determining potassium levels in the vitreous humor (KV) has been a subject of forensic pathology research for more than a quarter of a century. The numerous studies to date have yielded a variety of linear or piecewise-linear relationships between KV and PMI, i.e., different estimated intercepts and slopes of regression line(s) as well as different reliabilities of these estimates. This lack of agreement is due in part to the variable numbers of cases reported from study to study, differing observed ranges of KV and PMI, and the unaccommodated effects of factors on potassium concentration, including age of subject, amount of urea nitrogen, ambient temperature, and presence of illness. Original data from six of these studies, for a total of 790 cases, are reanalyzed together. The relationship between KV and PMI is not completely linear, and the residual variability of KV as a function of PMI is not constant. Thus, two main assumptions of the simple linear model, linearity and constant variance, are not supported by the data. It is clearly problematic to report statistical summaries such as the slope of an estimated regression line and the reliability of that estimate based on a model with faulty assumptions. Yet even after rescaling the data in an attempt to achieve linearity in the KV-PMI relationship and to stabilize residual variation, the relationship continues to be non-linear and its variability unstable. A new approach is developed for modeling KV and PMI that accommodates non-linearities and changing residual variability. A local regression model, specifically a loess smooth curve, is fitted separately to the data from each of the six studies. The loess smooth curve adapts locally to the changing and possibly non-linear relationship between KV and PMI across their observed ranges. The data from all six studies are then combined to yield a single loess curve with 95% confidence bands. The estimated loess curve and confidence bands are used in an inverse prediction method to construct low, middle and high PMI estimates at given values of KV. The reliability of estimated PMI decreases as KV increases. Although the confidence bands surrounding the overall curve widen in the extreme high end due to there being fewer available data in that region, PMI estimates are more precise over the entire range of KV and PMI than those obtained from any single study alone. A crossvalidation procedure provides an independent check of the predictive performance of the method.