other volatile compounds MON 8 2

Question 1

GHB

Answer 1

 Early study suggesting postmortem formation
 Y-hydroxybutyrate conc in pre- and postmortem blood and urine
 Limited study
o Blood: n = 20
o Urine: n = 8

Question 2

Carbon monoxide

Answer 2

carboxyhemoglobin is a very stable compound
Decomp of blood results in the formation of pigments which cause misleading
results when analyzed by spectrophotometry
Oxygen competing with CO at heme binding site
o Oxidation of COHb to Met-Hb
o Loss of CO binding capacity of Hb
Studies suggested formation of CO in postmortem tissues with apparent accumulation to
toxicologically significant conc
o Generally associated with drowning cases
o Thoracic cavity fluids
many times CO not formed during decomp but microorgainsim

Question 3

Cyanide

Answer 3

Measurement and interpretation of CN- [prussic acid], important in many cases
o Suspected poisoning by CN- of cyanogenic compounds
o Consideration in injury or death due to fire
 Found in low levels in the tissues of healthy subjects
o Result of normal metabolism
o Eating of cyanogenic foods
o Cigarette smoking

Question 4

toxic conc. of cyanide

Answer 4

1-2 mg/L

Question 5

What is cyanide decrease dependent on

Answer 5

Time and temperature

Question 6

what is cyanide loss due to

Answer 6

o Evaporation
o Thiocyanate formation
o Rxn with tissue components
o Rxn with embalming fluid

Question 7

PM formation of Cyanide

Answer 7

o Attenuated by addition of sodium fluoride
o Arises in part by conversion of thiocyanate to cyanide
o Storage temp
o Possible microbial action
 Cryogenic

Question 8

cyanide dose is detoxified by

Answer 8

About 80% of cyanide dose is detoxified by conversion via the liver enzyme rhodanese to
thiocyanate

Question 9

Conversion of thiocyanate to cyanide

Answer 9

o Thiocyanate can be converted, in vitro, to cyanide in the presence of erythrocytes
o Ballantyne (1977) demonstrated a positive correlation between thiocyanate conc
and whole blood cyanide conc
 Sample storage temp also impacted the amount of cyanide detected
o Seto (1995) demonstrated oxidative conc of thiocyanate to cyanide by
oxyhemoglobin during acid denaturation

Question 10

Formation of CN in postmortem tissues: Temperature

Answer 10

Conflicting evidence in the literature in regards to the levels of cyanide produced
in stored blood
showed no cyanide production during two week period at room temp
max. heated-induced cyanide production which was less than 0.05mg/L, did not exceed that witch was toxicologically signiifcant

Question 11

CN microbial

Answer 11

demonstrated in a number of orgainsms
Bacillus pyrocyaneus
psuedomas pyrocyaneus

Question 12

Methemoglobin

Answer 12

product of hemoglobin oxidation
ferrous to ferric unable to combine with oxygen
increased concetration of metHB–nitrogenoxides
action of certain drugs and chemicals anbd rare congential definceies in metHB reductase pathwasys
“sniffing” butyl nitrite
limited use in std cases; may have benefit in fire deaths if collected
shortly after death
1.5normal