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Vitreous analysis (postmortem chemistry)


Sarah Avedschmidt, M.D.

Last author update: 1 March 2016
Last staff update: 19 March 2024 (update in progress)

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PubMed Search: Postmortem chemistry

Sarah Avedschmidt, M.D.
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Table of Contents
Definition / general | Sites | Laboratory | Interpretation | Additional references
Cite this page: Avedschmidt S, Brown TT. Vitreous analysis (postmortem chemistry). PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/forensicschemistry.html. Accessed April 23rd, 2024.
Definition / general
Sites
Blood
  • Peripheral venous / arterial specimens best approximate antemortem values
  • For toxicology, recommended to use femoral or subclavian vessels, via percutaneous collection with large bore needle and syringe
  • 40 - 50 mL required
  • Place portion in fluoride preservative and portion in anticoagulant

Vitreous Humor
  • Most frequently used specimen for postmortem analysis
  • Isolated and protected by the orbit, less subject to putrefaction than blood
  • Not subject to diffusion of drugs and alcohols from the stomach
  • Also free of erythrocytes
  • Collect with small syringe attached to an 18 gauge needle, using gentle suction to remove all vitreous (2 - 5 mL in adult, 1 mL in newborn)
  • Fluid from each eye is stored separately

Synovial Fluid
  • Rarely used as substitute for vitreous humor
  • About 1 mL can be aspirated from each knee joint

Urine
  • Collect with large bore needle attached to syringe once bladder is exposed at autopsy or by urethral catherization before autopsy

Cerebrospinal Fluid
  • Aspirated from cisterna magnum with needle, by standard percutaneous posterior lumbar puncture
  • Aspirate through the spinal foramina after organ evisceration or by inserting a needle into a lateral ventricle after removing the skull cap, reflecting the dura and separating the cerebral hemispheres

Bile
  • Rarely used
  • Aspirate from gallbladder or directly from common bile duct in patients status post cholecystectomy

Gastric Contents
  • Rinse external stomach with water
  • Puncture stomach wall and pour stomach contents into bag

Hair
  • Hair should be obtained by pulling to include hair roots
  • Adequate sample is 0.5 g for DNA analysis, up to 10 g for analysis of heavy metals
  • Tie together while maintaining orientation of hair roots

Fingernails
  • Acquired by clipping or removing the entire nail

Fibroblasts for Tissue Culture
  • Can be used for karyotyping, metabolic assays, enzyme assays and diagnostic ultrastructural studies
  • Collect from skin, fascia, lung, diaphragm, muscle and cartilage
  • Samples are placed in sterile tube containing culture medium (RPMI or MEM)

Tissue
  • Liver, brain, kidney, cardiac muscle, skeletal muscle and peripheral nerve can be used for metabolic studies and nucleic acid analysis
  • Should be obtained shortly after death and frozen rapidly in liquid nitrogen or dry ice and stored at -70°C
Laboratory
Postmortem Chemical Changes in Pathological Conditions

    Diabetic ketoacidosis
    • Vitreous glucose concentration (> 200 mg/dL or > 11.1 mmol/L) is the most reliable marker
    • Also reliable are ketone bodies, urine glucose and glycated hemoglobin

    Dehydration
    • Increased postmortem serum and vitreous urea nitrogen levels (> 40 mg/dL)
    • Increased vitreous sodium (> 155 mEq/L) and chloride levels (> 135 mEq/L)
    • Normal postmortem serum and vitreous creatinine levels

    Endocrine Disorders
    • Pituitary, adrenal cortical and a few other hormone concentrations will reflect antemortem levels
    • Epinephrine and insulin levels are unstable postmortem

    Anaphylaxis
    • Mast cell granules contain proteases such as tryptase and chymase which are degranulated during anaphylactic reactions

    Hypothermia
    Sepsis
    • Serum procalcitonin increases (> 100 ng/ml) in severe systemic bacterial infections
    • Acute phase proteins and cytokines can be used in postmortem chemistry similarly to clinical practice
    • Serum and urine neopterin is increased in cases of fatal bacterial and viral infections

    Insulin Overdose
    • Hypoglycemia cannot be reliably tested
    • Ratio of insulin to C peptide can be used

    Liver Disease
    • Aminotransferases are not reliable postmortem
    • Albumin-globulin ratio is reliable

    Decomposition
    • Decreased sodium and chloride concentrations
    • Increased potassium concentrations (> 20 mEq/L)

    Incomplete suspension / manual strangulation
    • Increased thyroglobulin and T3 concentrations in postmortem serum from heart blood
Interpretation
  • Alcohol misuse: carbohydrate deficient transferrin, ethyl glucuronide, ethyl sulphate
  • Anaphylaxis: tryptase, chymase
  • Cardiac function: atrial natriuretic peptide, brain natriuretic peptide, myocardial ischemia (troponin I, troponin T, myosin, myoglobin, creatine kinase and creatine kinase MB)
  • Electrolytes: sodium, chloride, calcium, magnesium, strontium
  • Glucose metabolism: glucose, glycated hemoglobin, ketone bodies, insulin, peptide C
  • Liver function: total cholesterol, total bilirubin, total protein
  • Renal function: urea nitrogen, creatinine, uric acid
  • Sepsis/Inflammation/Infection: procalcitonin, acute phase proteins and cytokines, neopterin
  • Hormones: adrenocorticotropic hormone; thyroid stimulating hormone / thyroglobulin / thyroid hormones; catecholamines; cortisol; chorionic gonadotropin; erythropoietin ; chromogranin A; S100B; serotonin, myoglobin
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