Postmortem Chemistries

Question 1

Significance of anatomic site of sample postmortem

Answer 1

• There are significant differences in analytes between specimens taken from the left and right sides of the heart and between central (cardiac) and peripheral blood
• Need to take as much vitreous as possible, which also has variation in analytes centrally and peripherally

Question 2

Postmortem glucose

Answer 2

• serum glucose increases after death 2/2/ hepatic glycogenolysis
• postmortem diagnosis of diabetes should not be made on basis of postmortem blood glucose alone
• vitreous glucose falls after death due to glycolysis; preferred for postmortem diagnosis of diabetic ketoacidosis, which is diagnosed by presence of high vitreous glucose and ketones

Question 3

Postmortem BUN and creatinine

Answer 3

• BUN and creatinine are stable after death
• High BUN in conjunction with hyperNa is useful to diagnose dehydration

Question 4

Postmortem sodium and chloride

Answer 4

• both decrease immediately after death at a rate of 0.9 mEq/L/hour
• vitreous sodium and chloride are stable; can be used in conjunction with BUN and potassium to categorize the patient into 1 of several patterns: dehydrated, uremic, or decomposition

Question 5

Postmortem potassium

Answer 5

• serum and CSF K rise abruptly after death
• vitreous K rises linearly

Question 6

Tryptase and postmortem diagnosis of anaphylaxis

Answer 6

• stable in serum for several days after death
• elevated serum tryptase not entirely specific, but normal postmortem serum tryptase has a high NPV