Magnesium, potassium, sodium and calcium in post-mortem vitreous humour from humans

Decrease in electrolyte after vitrectomy surgery may affect the results of forensic investigations using vitreous humor

PURPOSE

Vitreous humor (VH) is used for postmortem biochemical studies because it is well protected in an uncontaminated state even after death. The goal of this research was to investigate electrolyte concentrations in the VH from human eyes with and without a history of vitrectomy surgery.

METHODS

We analyzed the sodium (Na), potassium (K), chloride (Cl) and magnesium (Mg) concentrations from 34 VH samples from 34 patients. Eleven samples were from eyes with a history of vitrectomy, and the remaining 23 eyes had no history of vitrectomy. The correlations of Na, K, Cl and Mg concentrations with patient age, interval between first and second vitrectomy, and lens status (history of cataract surgery) were also evaluated.

RESULTS

The Na, K, Cl and Mg concentrations in VH from vitrectomized eyes were 134.1 ± 7.9 mmol/L, 3.7 ± 0.2 mmol/L, 99.7 ± 6.7 mmol/L and 0.59 ± 0.09 mmol/L, respectively; all were significantly lower than the corresponding concentrations in VH from control eyes (lower by 5.0%, 11.0%, 11.7%, and 22.6%, respectively). Na, K, Cl and Mg concentrations in VH from vitrectomized eyes did not show significant correlations with patient ages or the interval between their first and second vitrectomies. There were no significant differences in Na, K, Cl and Mg concentrations in VH between phakic eyes and intraocular lens-implanted eyes.

CONCLUSIONS

With the increasing number of vitrectomies being performed, it is necessary to consider the history of vitrectomy when using a subject's VH in forensic examination.

Long-Acting Microparticle Formulation of Griseofulvin for Ocular Neovascularization Therapy

Neovascular age-related macular degeneration (nAMD) is a leading cause of vision loss in older adults. nAMD is treated with biologics targeting vascular endothelial growth factor; however, many patients do not respond to the current therapy. Here, a small molecule drug, griseofulvin (GRF), is used due to its inhibitory effect on ferrochelatase, an enzyme important for choroidal neovascularization (CNV). For local and sustained delivery to the eyes, GRF is encapsulated in microparticles based on poly(lactide-co-glycolide) (PLGA), a biodegradable polymer with a track record in long-acting formulations. The GRF-loaded PLGA microparticles (GRF MPs) are designed for intravitreal application, considering constraints in size, drug loading content, and drug release kinetics. Magnesium hydroxide is co-encapsulated to enable sustained GRF release over >30 days in phosphate-buffered saline with Tween 80. Incubated in cell culture medium over 30 days, the GRF MPs and the released drug show antiangiogenic effects in retinal endothelial cells. A single intravitreal injection of MPs containing 0.18 µg GRF releases the drug over 6 weeks in vivo to inhibit the progression of laser-induced CNV in mice with no abnormality in the fundus and retina. Intravitreally administered GRF MPs prove effective in preventing CNV, providing proof-of-concept toward a novel, cost-effective nAMD therapy.

Estimation of Time Since Death From Potassium Levels in Vitreous Humor in Cases of Unnatural Death: A Facility-Based Cross-Sectional Study

Background Estimation of time since death/postmortem interval (PMI) forms a crucial component for all autopsy surgeons. With the subjectivity that is prevalent with conventional morphological and physical signs of death, newer-age modalities such as chemical analysis provide better precision. The easy accessibility and the resistance to putrefaction make vitreous humor the best choice for such chemical analysis. Thus, the present study's aim is to estimate the time since death in cases of unnatural death by investigating the potassium level changes in the vitreous humor. Methodology This is a facility-based cross-sectional study conducted in the mortuary under the Department of Forensic Medicine in a public tertiary healthcare teaching hospital in South India between August and September 2022. Deceased individuals fulfilling the inclusion and exclusion criteria were recruited in the study. Vitreous samples were collected from a single eye and analyzed using an autoanalyzer for potassium values. After due derivations, postmortem intervals were calculated from potassium values, then they were compared with the PMIs estimated using physical signs and those determined using official police records. Data were entered using MS Excel 20 (Microsoft Corporation, Redmond, Washington) and analyzed using the Statistical Package for the Social Sciences (SPSS) software, version 20 (IBM Corp., Armonk, NY). Results Of the 100 deceased individuals included in the study, 68% were men, and the majority (24%) belonged to the age group of 53-62 years. A linear relationship is said to exist between vitreous potassium concentration and postmortem interval. No correlation was seen between the ambient temperature and the potassium levels of the vitreous humor. PMI confirmed by the potassium levels seconded the PMI given by the police records and physical signs (Rigor mortis) (Spearman's rho was statistically significant at the two-tailed level or at the 0.01 level with a kappa value of 0.88). Conclusion Potassium measurements in the vitreous humor to estimate the PMI are associated with improved accuracy and precision in determining the time since death. They are not affected by external factors, making them a reliable marker for the same.

Detection of Fatal Potassium Overdose: A Case Report and Review of the Literature

Potassium overdose usually occurs accidentally, but potassium is also used for judicial executions, assisted death, and, rarely, suicides. In addition to exogenous overdose, various drugs, and renal failure, diabetic ketoacidosis can cause hyperkalemia. Potassium tablets are used in most cases of suicidal potassium overdose. Suicide by intravenous administration of potassium is rare but usually fatal. The author reports a rare case of suicide with potassium infusion. Autopsy and histology findings, along with post-mortem biochemical analysis of different body fluids and fluid from the infusion set, are reported. Previously published reports of potassium overdose were reviewed, and the detection possibilities of potassium overdose are discussed. The detection possibilities of lethal hyperkalemia are very limited since hyperkalemia produces only nonspecific autopsy and histology findings. Post-mortem potassium concentrations are not indicative of ante-mortem potassium concentrations; therefore, post-mortem biochemical analysis has limited value in determining potassium overdose. The best way to prove potassium overdose is via the collection and analysis of circumstantial evidence.

The significance of post-mortem vitreous calcium concentration in forensic practice

Calcium, as one of the main extracellular ions, maintains a key role in numerous biologic functions. For forensic purposes, it was analyzed mostly for estimation of postmortem interval (PMI). We have designed our experiment with the concept that the repetitive withdrawal of vitreous humor (VH) might clarify the postmortem metabolism of calcium in greater detail to estimate the PMI. Accordingly, 248 samples of VH from 31 autopsy cases were evaluated over three years; samples (0,1 mL of VH) were taken and analyzed at equal time intervals after death-every three hours until 24 h after death. Each sample was centrifuged and analyzed using the ARCHITECT C SYSTEM 8000. Moreover, functional relationship between PMI and calcium concentration was established: PMI (hours) = [Ca²⁺] × 13.696-7.843. Although the concentration of calcium in VH in the analyzed group increases with time, the coefficient of variation for the regression (CVreg = 46.8%) indicates that this correlation is not so strong, meaning that the level of predictiveness of calcium for estimation of time since death is poor when is not used in combination with other relevant substances.

Improvement in estimation of time since death by albumin and potassium concentrations in vitreous humor

The measurement of the potassium concentration (K⁺) in vitreous humor (VH) has been a well-known adjunct for the estimation of the post-mortem interval (PMI) since the early 1960s. For years, however, many authors have been using other biochemical markers in an attempt to improve predictions. In this paper we confirm the role of K⁺ in the determination of the PMI adopting a linear regression model and we investigate whether other biochemical markers could improve the model through a multiple regression analysis. Additionally, the research aims to confirm the data of the analytes of interest among different techniques and instrumentations. We deemed this as an important issue because a primary concern in the literature is that automated analytical methods are often calibrated and, for the most part, validated for serum or urine analysis. Our results confirmed the well-established role of K⁺ as well as highlighted Albumin as a novel marker to be considered for further improvement of prediction models, especially since 72 h after death.

Vitreous humor endogenous compounds analysis for post-mortem forensic investigation

The chemical and biochemical analysis of bodily fluids after death is an important thanatochemical approach to assess the cause and time since death. Vitreous humor (VH) has been used as a biofluid for forensic purposes since the 1960s. Due to its established relevance in toxicology, a literature review highlighting the use of VH with an emphasis on endogenous compounds has not yet been undertaken. VH is a chemically complex aqueous solution of carbohydrates, proteins, electrolytes and other small molecules present in living organisms; this biofluid is useful tool for its isolated environment, preserved from bacterial contamination, decomposition, autolysis, and metabolic reactions. The post-mortem analysis of VH provides an important tool for the estimation of the post-mortem interval (PMI), which can be helpful in determining the cause of death. Consequently, the present review evaluates the recent chemical and biochemical advances with particular importance on the endogenous compounds present at the time of death and their modification over time, which are valuable for the PMI prediction and to identify the cause of death.

Thanatochemistry at the crime scene: a microfluidic paper-based device for ammonium analysis in the vitreous humor

Most of the on-site approaches for inferring of the post-mortem interval are still based on observative data from the direct body inspection, whereas, objective and quantitative analyses, such as potassium in the vitreous humor, are require laboratory instrumentation and skilled personnel. The present paper presents a simple and low cost analytical method suitable for use at the crime scene for inferring the time since death. The method uses a microfluidic paper-based device (μPAD) for the determination of ammonium in the vitreous humor (VH) based on the selective interaction between the ammonium and the Nessler's reagent. The color change was measured in terms of "RGB distance" by using a simple and free smartphone application. The optimized device showed a limit of detection of 0.4 mmol L^-1, with between days precision less than 9.3% expressed as relative standard deviation, and accuracy between days from 94.5% to 104.5%. The selectivity of the Nessler's reaction was tested towards the main vitreous humor compounds, and no significant interferences were found. This paper-based analytical device was successfully used for the determination of ammonium ion in VH samples from forensic autopsies. The results obtained with the proposed method, although for a limited number of cases (n = 25), showed a close correlation with the data obtained with an instrumental analysis based on capillary electrophoresis. Moreover, in order to make the evaluation of results as simple as possible, a direct correlation between the color intensity, expressed as RGB distance, and the post-mortem interval was studied and a significant correlation was found (R² > 0.78). In conclusion, the present preliminary study showes that the proposed device could be an additional tool to the traditional methods for a more accurate, although still presumptive, estimation of the time of death directly at the crime scene.

The persistent problem of drowning - A difficult diagnosis with inconclusive tests

Although the diagnosis of drowning may appear straightforward the reality is that it is sometimes one of the most difficult in forensic pathology. To begin with, there is no universal agreement on what constitutes drowning with some definitions using the term in the absence of a lethal outcome. Next are the significant problems that arise in finding immersed bodies and in assessing the death scene. Prolonged post mortem intervals are associated with artefactual modifications of the body from putrefaction and post mortem animal predation. Both of these may create and disguise injuries. The absence of pathognomonic pathological features at autopsy and the presence of potentially life threatening underlying organic illnesses complicate determination of both the cause and manner of death. There may even be no autopsy findings to indicate that immersion had occurred. Finally, the unreliability of laboratory tests with significant overlap with control cases where death had no association with immersion presents further problems. Thus lethal drowning remains a complex event that requires the use of a wide variety of information sources, not just data gleaned from the dissection table.

Fatal intravenous injection of potassium: Is postmortem biochemistry useful for the diagnosis?

Fatal cases of potassium overdoses have traditionally been considered indemonstrable due postmortem biochemical investigation limits (mainly potassium determination in postmortem serum and vitreous humor). Nevertheless, some authors have expressed a divergent opinion over the years based on the results of their own investigations. In this study, we investigated left vitreous, right vitreous, postmortem serum from peripheral blood, postmortem serum from cardiac blood, urine, pericardial and cerebrospinal fluid potassium concentrations in 21 forensic autopsy cases. One of these was a case of accidental, fatal intravenous potassium injection in a hospitalized patient. The other twenty cases were subjects with various causes of death unrelated to potassium administration and comparable postmortem intervals. Our aim was to assess whether postmortem biochemical investigations performed in several biological samples may be useful in diagnosing exogenous potassium administration. No statistically significant differences were observed between the measured concentrations in the fatal case of potassium intravenous administration and the control cases in any of the tested samples. Potassium concentrations in the investigated case of exogenous potassium injection were within the range of those measured in the control cases, irrespective of the tested biological sample. Our findings corroborate the conclusions of former authors who highlighted that circumstantial evidence provides the greatest diagnostic contribution in situations of suspected potassium poisoning. This is due to the objective limitations demonstrated by postmortem biochemical investigations in such cases, even when potassium measurements are carried out in several biological samples of satisfying quality and within a relatively short postmortem interval.

Degradation of Kidney and Psoas Muscle Proteins as Indicators of Post-Mortem Interval in a Rat Model, with Use of Lateral Flow Technology

We investigated potential protein markers of post-mortem interval (PMI) using rat kidney and psoas muscle. Tissue samples were taken at 12 h intervals for up to 96 h after death by suffocation. Expression levels of eight soluble proteins were analyzed by Western blotting. Degradation patterns of selected proteins were clearly divided into three groups: short-term, mid-term, and long-term PMI markers based on the half maximum intensity of intact protein expression. In kidney, glycogen synthase (GS) and glycogen synthase kinase-3β were degraded completely within 48 h making them short-term PMI markers. AMP-activated protein kinase α, caspase 3 and GS were short-term PMI markers in psoas muscle. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was a mid-term PMI marker in both tissues. Expression levels of the typical long-term PMI markers, p53 and β-catenin, were constant for at least 96 h post-mortem in both tissues. The degradation patterns of GS and caspase-3 were verified by immunohistochemistry in both tissues. GAPDH was chosen as a test PMI protein to perform a lateral flow assay (LFA). The presence of recombinant GAPDH was clearly detected in LFA and quantified in a concentration-dependent manner. These results suggest that LFA might be used to estimate PMI at a crime scene.

Review of Postmortem Interval Estimation Using Vitreous Humor: Past, Present, and Future

For decades, forensic scientists have sought a means of estimating the postmortem interval using laboratory analyses. The best known of these attempts uses a linear regression formula based on the increasing concentration of potassium ions in vitreous humor following death. Like all laboratory analyses, the determination of a potassium concentration is subject to pre-analytical, analytical, and post-analytical errors. Any error is magnified when entered into a regression formula that itself is subject to statistical variation, typically with a 95% confidence interval. Estimating the postmortem interval based solely on the concentration of potassium in vitreous humor proved too simplistic for accurate modeling of the myriad factors that influence postmortem changes. Research continues, using more complicated algorithms involving multivariate ion and chemical analyses and genomic sequencing of the postmortem biome. However refined estimates of the postmortem interval based on laboratory analysis become, sound medical practice will still require the integration of scene findings and information concerning the last time that a given decedent was known to be alive with the results of postmortem examination and laboratory analyses into a medical opinion concerning the postmortem interval.

Forensic application of microRNA-706 as a biomarker for drowning pattern identification

Forensic research using microRNA has been used so far only for the identification of body fluids, but its use in understanding biological processes in post-mortem pathology has not been studied before. Therefore, we performed experiments in mice to compare between freshwater and saltwater drowning models, and miRNA expression was analyzed in the brain through a forward bioinformatics screening approach. In this study, we identified eight specific microRNAs whose expression increased in freshwater and decreased in saltwater. Among them, miR-706 - targeting HCN1 - was identified as a potent biomarker for the drowning pattern identification. A higher expression of miR-706 was detected in the freshwater drowning compared to the control and saltwater drowning group (p<0.05, and p<0.01, respectively). HCN1 mRNA expression, a suggested candidate target for miR-706, was lower in the freshwater (p<0.01) than in the saltwater drowning group, and showed statistical difference between freshwater and saltwater drowning (p<0.01). miR-706 was specifically expressed in the hippocampal neurons as detected by in situ hybridization. Our data suggest that a specific microRNA may provide clues to understanding some crime scene investigations and pathobiological processes in the dead body.

Promising blood-derived biomarkers for estimation of the postmortem interval

A linear correlation between blood putrefaction time and biochemical parameter concentrations was obtained. Two mathematical models that may have predictive value for estimation of thepostmorteminterval were developed. The obtained results might be complementary procedures for the methodologies already used.

Metals and (metallo)proteins identification in vitreous humor focusing on post-mortem biochemistry

Evaluation of metals and (metallo)proteins in vitreous humor samples at different post-mortem intervals.

Postmortem vitreous chemistry--an evaluation of sodium, potassium and chloride levels in estimation of time since death (during the first 36 h after death)

Estimation of time since death is a paramount medico-legal issue in any postmortem examination. The present study is intended to study the correlation between postmortem interval and vitreous humor chemistry for sodium, potassium, and chlorides. The study is aimed to find male-female differences and differences between right and left eyes in vitreous chemistry. The vitreous humor samples were collected in 114 autopsies conducted in the study center and analyzed biochemically. All the cases where exact time of death was known and where the time since death ranged between 0 and 36 h were included in the study. Data obtained was analyzed statistically using spss version 11.0. The present research did not find a significant correlation between vitreous chemistry and postmortem interval. The differences in vitreous sodium, potassium, chloride levels and the sodium potassium ratio among males and females and between right and left eyes were not found to be statistically significant.

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.

Postmortem biochemistry

Postmortem biochemistry may provide significant information in determining the cause of death. Due to the rapid postmortem breakdown of metabolism and active membrane transport only analytes which are stable in blood can be determined on this fluid compartment, other parameters have to be analysed on other fluid compartments like vitreous humor (VH). However, using another fluid compartment as a mirror of blood at the moment of death involves severe methodical problems. The conceptual problems of reference values in vitreous humor as a mirror of blood are addressed. Additionally, the necessary steps to be taken before calculating the discriminating values between "normal" and "diseased" are described. For all chemical determinations, a clear definition of the site of sample acquisition is necessary. Up to now chemical determinations on alternative fluids have mainly been carried out using instruments calibrated for urine or serum. Developing calibrated methods for analysis of alternative fluids is a further task for the future.

Postmortem diagnosis of hypertonic dehydration

Beside morphological signs of hypertonic dehydration as tinting of skin, sunken eyes, dry surface of the galea or dry cutting areas of organs, a chemical profile of vitreous humor was proposed as a diagnostic tool for the diagnosis of hypertonic dehydration. The profile consists of an elevation of sodium >155 mmol/l, chloride >135 mmol/l and urea >40 mg/dl. This profile was named dehydration pattern. The value of this dehydration pattern for the diagnosis of hypertonic dehydration will be discussed by a short review of the literature and case reports. So far, the published literature on the dehydration pattern is not a sound scientific basis for the diagnosis of dehydration.

Evaluation of postmortem serum calcium and magnesium levels in relation to the causes of death in forensic autopsy

There appears to be very poor investigation of postmortem serum calcium (Ca) and magnesium (Mg) for diagnostic evidence to determine the cause of death. The aim of the present study was a comprehensive analysis of the serum levels in relation to the causes of death in routine casework. Autopsy cases (total, n=360; 5-48 h postmortem), including blunt injury (n=76), sharp injury (n=29), asphyxiation (n=42), drownings (n=28: freshwater, n=11; saltwater, n=17), fire fatalities (n=79), methamphetamine (MA) poisoning (n=8), delayed death from traumas (n=37), and acute myocardial infarction/ischemia (AMI, n=61), were examined. In total cases, there was no significant postmortem time-dependent rise in serum Ca and Mg. Both Ca and Mg levels in the heart and peripheral blood were significantly higher in saltwater drowning compared with those of the other groups. In addition, a significant elevation in the Ca level was observed in freshwater drowning and fire fatalities, and in the Mg level in fatal MA intoxication and asphyxiation. Topographic analyses suggested a rise in serum Ca and Mg due to aspirated saltwater in drowning, that in serum Ca in freshwater drowning and fire fatalities of peripheral skeletal muscle origin and that in serum Mg in MA fatality and asphyxiation of myocardial and/or peripheral origin. These markers may be useful especially for diagnosis and differentiation of salt- and freshwater drownings and may be also helpful to determine the causes of death involving skeletal muscle damage, including burns and MA intoxication.

Postmortem lung weight in drownings: a comparison with acute asphyxiation and cardiac death

There are several controversial findings and arguments about the lung weight as a marker of drowning. The aim of the present study was to examine the difference in the lung weight and the amount of pleural effusion between freshwater and saltwater drownings (n=70 and n=75, respectively), in comparison with asphyxiation (n=85) and acute cardiac death (n=82), for the diagnosis of drowning. In drowning cases, a gradual postmortem time-dependent decrease in the lung weight and a reciprocal increase in the pleural effusion suggested postmortem transudation from the lungs. The decrease in the total value of the combined lung weight and the amount of pleural effusion was marked in saltwater immersion after 3 days postmortem, suggesting a leakage of the effusion out of the thoracic cavity under an osmotic effect of the immersion medium. In cases within 3 days postmortem, when the combined lung weight and amount of pleural effusion were added to estimate possible combined lung weight at the time of death, there was a gross difference among the causes of death: the value was the largest in saltwater drowning, followed by freshwater drowning, acute cardiac death and asphyxiation. However, the value depended on the gender and age of the subjects, suggesting a relation to the individual physical constitution and survival time or vital activity. These factors should be taken into consideration in evaluation of the lung weight in the diagnosis of drownings.

Possible postmortem serum markers for differentiation between fresh-, saltwater drowning and acute cardiac death: a preliminary investigation

The aim of the present study was to investigate the differences in postmortem blood biochemistry between fresh-, saltwater drowning and acute myocardial infarction/ischemia (AMI) (n=11, n=15 and n=23, respectively; postmortem interval <48 h). Left and right cardiac blood samples were examined for the serum markers: sodium (Na), chloride (Cl), magnesium (Mg), blood urea nitrogen (BUN), creatinine (Cr), pulmonary surfactant-associated protein A (SP-A) and cardiac troponin T (cTn-T). The most efficient markers were the left-right cardiac BUN ratio for determination of drowning (hemodilution) and the left heart blood Mg level for differentiation between fresh- and saltwater aspiration. A characteristic feature of saltwater drowning was a low left-right BUN ratio and a marked elevation in the serum Cl, Mg and Ca levels of the left heart blood. Serum cTn-T level was usually low in drownings, showing a difference from most cases of AMI. Freshwater drowning showed a significant elevation of serum SP-A, although there was considerable overlapping with saltwater drowning and AMI. These findings suggested the usefulness of serum markers in the investigation of death from drownings.

Pericardial fluid postmortem: Comparative study of natural and violent deaths

Thanatochemistry is an increasingly important ancillary procedure in forensic practice. Alterations are known to take place in biochemical components during the postmortem period, particularly in the blood, and both research results and their interpretation have been the object of some controversy. For that reason, emphasis has been placed on the examination of fluids that are neither altered nor contaminated as rapidly as blood after death. This study tested the hypothesis that pericardial fluid (PF) may be a suitable medium for biochemical analysis in corpses. The study sought to determine concentrations of urea, creatinine, glucose, creatinine kinase 2, proteins, calcium, sodium, and potassium, in the pericardial fluid of corpses. The study sample was divided into two groups, natural deaths and violent deaths. Intergroup results were compared, using Mann-Whitney's U test for paired data. No significant differences were obtained between the natural death and violent death groups for the parameters studied, with the exception of urea (p < .05). Further studies are required to compare these results and create the possibility for new conclusions.