Inclusion of aspiration of vitreous humor in fatal aircraft accident autopsy protocol

In aviation accident investigation, the toxicology and biochemistry forms a very important role in finding out the antecedent cause of death of the pilot or the crew. In many instance, the body of the deceased is recovered after a significant time. This results in coagulation/thrombosis of the peripheral blood. Blood and serum is however required for various parameter analysis. In case there is a difficulty in aspirating blood for this purpose, then vitreous can be used as a more suitable alternative. The protected location of the vitreous in the orbit renders the fluid less susceptible to putrefaction than blood. The main objective of this study was to establish correlationship between antemortem serum and postmortem vitreous biochemistry. Over last 14 months, 13 requests for embalming of bodies were received from NOK of patients dying in an AF Hospital. After obtaining written informed consent, the vitreous humour from the deceased was sampled by special technique discussed in the paper. Simultaneously prior to performing the embalming an intravenous blood sample was also taken. Following biochemical test were performed in both these samples: Potassium, Sodium, Glucose, & BUN Creatinine. The samples for electrolytes were analysed in AVL9180 electrolyte analyzer and biochemical analysis was carried out in Erba Chem 5 plus and EM 360 biochemistry analyzers. _The results indicated that postmortem vitreous Urea (R = 0.967; P< 0.0001) Sodium (R = 0.844; P= 0.003) and Creatinine (R = 0.865; P< 0.0001) levels were highly correlated with antemortem serum levels. This finding Is consistent with a few earlier observations that reported a marked stability of postmortem Urea and Creatinine concentrations in the vitreous humor. The postmortem stability of vitreous urea, sodium and creatinine and their strong correlation with the antemortem serum biochemistry is helpful in providing reliable information about the antemortem renal status of the deceased subject or in making a postmortem diagnoses of renal failure. The sodium was stable in our study unlike abovementioned studies, probably because the vitreous collection was done in most of the cases within 6 hrs of death. The other parameters that can be assessed have been discussed in the paper. Overall, only postmortem Vitreous Urea, Sodium and Creatinine were significantly correlated with their corresponding antemortem serum concentrations. Although a diagnosis of hypoglycemia cannot be reliably made in the postmortem period, high level of vitreous glucose levels can be considered to accurately reflect antemortem hyperglycemic status (Diabetes Mellitus). Ketoacidosis and Hyperlactemia can also be detected in post mortem vitreous analysis. Vitreous Potassium levels should be estimated to determine the post mortem interval (time since death) using regression formulas.