Vitreous humour is preferred over blood for postmortem biochemistry because it is relatively protected from putrefaction. Which ion shows the MOST reliable postmortem rise in vitreous humour and is used as a marker of the time since death in the early postmortem period?
- A Potassium ✓
- B Sodium
- C Chloride
- D Calcium
Correct answer: A. Potassium
Explanation
Vitreous potassium rises in a relatively linear fashion after death due to leakage from photoreceptor cells; normal ante-mortem vitreous K+ is ~5 mmol/L and rises at approximately 0.14–0.17 mmol/L per hour. This can be used to estimate the postmortem interval within the first 24–72 hours using the Sturner formula. Sodium and chloride fall post-mortem but are less reliable for PMI estimation. Calcium changes are not used for this purpose.
Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.