A postgraduate student is reviewing reference ranges before validating vitreous humour results at autopsy. What is the approximate vitreous potassium concentration in a healthy living person?

• A 0.5 to 1.5 mEq/L
• B 3.5 to 5.5 mEq/L ✓
• C 8 to 12 mEq/L
• D 15 to 20 mEq/L

Explanation

Ante-mortem vitreous potassium lies close to serum potassium, around 3.5 to 5.5 mEq/L, because the vitreous is an ultrafiltrate-like fluid separated from blood by an intact blood-retinal barrier. After death the level climbs steadily from this baseline as intracellular potassium leaks out of retinal cells. The distractor of 8 to 12 mEq/L represents a value reached several hours after death, not the living baseline against which postmortem rise is calculated.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.