For estimating a prolonged postmortem interval exceeding 24 hours, which additional vitreous analyte rises steeply and can complement potassium, which tends to plateau later in the postmortem period?

• A Calcium, mobilised from bone adjacent to the orbit
• B Chloride, released from lysed erythrocytes
• C Ammonia, produced by deamination of amino acids and adenine nucleotides ✓
• D Bicarbonate, generated by continuing carbonic anhydrase activity

Explanation

Vitreous ammonia rises progressively after death from deamination of purines, amino acids and adenosine monophosphate, and unlike potassium it does not flatten early, so it extends the usable range of biochemical interval estimation into later postmortem periods. Chloride and bicarbonate fall after death rather than rise, and calcium is relatively stable and not derived from orbital bone. Combining ammonia or hypoxanthine with potassium improves discrimination at long intervals.

Reference: Knight's Forensic Pathology, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.