| Objective1. To develop a postmortem distribution model and a postmortem diffusion model of phenobarbital in rabbits, and a decomposition kinetics model of phenobarbital in preserved blood.2. To study the postmortem distribution and postmortem diffusion of phenobarbital in rabbits and decomposition kinetics of phenobarbital in preserved specimens of human blood, and to provide a scientific evidence for the forensic identification of phenobarbital poisoning death.Methods1. Six rabbits were randomly allocated to oral and vein administration groups, which were given an intragastric administration or vein administration with a dose of 0.34 mg/kg. As soon as the vital signs disappeared, the rabbits were dissected and the specimens such as heart blood, heart, liver, spleen, lung, kidney, brain,muscle, urine, bile and humor vitreous were sampled immediately, in which the concentration of phenobarbital was determined by a GC and a GC/MS.2. Thirty experimental rabbits were executed by tracheal occlusion and given an postmortem intragastric administration of phenobarbital with a dose of LD50(0.34g/kg) one hour later. Twenty-one rabbits were placed at home temperature. Three animals were randomly dissected after postmortem administration of phenobarbital at 3h,6h,612h,24h,48h,72h and 96h respectively and the specimen such as blood-heart, peripheral blood, bile, urine, vitreous humor, the right upper limb muscles, the right lower limb muscles, chest muscle, heart, liver, spleen, lung, kidney, brain, stomach, were sampled. Other nine rabbits were placed at 20℃, 4℃,-20℃respectively. At 96h after postmortem administration, they were dissected and identical specimens were taken. After being extracted with extract with acid ether, the phenobarbital in the specimen was analyzed using a gas chromatography with internal standard working curve.3. The blank blood 1200 mL was divided into 4 parts, every part 400 mL. Phenobarbital was added to the blank blood at the therapeutic (25μg/mL), toxic(100μg/mL), lethal(150μg/mL) concentration respectedly. The every part was divided into 12 parts, nine of which were 20℃, 4℃,-20℃, other three was added NaF to 1% and was preserved at 20℃. At Od,7d,14d,21d,28d,42d,56d,105d,147d,189d,231d, 1mL blood was taken from every preserved specimen, were acidified, and extracted with ether, in which the concentration of phenobarbital was determined by a GC and a GC/MS.4. Statistics method:The datas were collected by software SPSS 11.5 and expressed by x-±s Results1. Postmortem distribution After the administration of phenobarbital by oral or vein approach, the rabbits showed lethargy state. The oral group rabbits died after the administration for 2.0±0.5h, and the vein group for 2.0±0.1h. The order of phenobarbital concentration of in rabbits was as follows:①oral group:liver (183.22±11.19μg/g)> kidney(143.45±13.02μg/g)> brain (115.47±6.92μg/g), heart(109.24±14.01μg/g)> lung(93.38±8.29μg/g), heart blood (86.80±10.32μg/mL)> spleen (69.69±12.36μg/g), muscle (66.14±4.63μg/g), bile (65.52±4.56μg/mL), urine(52.04±9.62μg/mL)>humor vitreous (29.02±10.86μg/mL).②vein group:urine(311.36±37.26μg/mL)> liver(155.74±29.35μg/g)> brain(104.40±9.43μg/g), heart(96.96±18.91μg/g), kidney(91.13±2.06μg/g), heart blood(89.81±8.32μg/g)> bile(75.19±5.09μg/g), muscle (62.69±6.67μg/g), spleen(57.38±17.06μg/g)> lung(41.32±8.80μg/g), humor vitreous (29.60±8.56μg/mL) (LSD analysis, P<0.05).2. Postmortem diffusion Phenobarbital can not be detected in the urine of 21 rabbits in the first 6 h, but it was detected in other organs and body fluids during 4 days at home temperature. The concetration of phenobarbital in heart showed the same tendency as in lung, which in liver showed the same tendency as in spleen.Phenobarbital was detected in the all specimens of the rabbit preserved at home temperature(20℃) for 4 days, it was not detected in the urine, left leg muscle and right of rabbits preserved at 40℃for 4 days, and was not detected in the urine, vitreous humor, brain,left leg muscle and right leg muscle of the rabbits preserved at home temperature—20℃.3. Decomposition kinetics. The decomposition kinetics of phenobarbital in preserved human blood showed a descend and it met one-compartment open modelwith the first order kinetics, and could be expressed as Ct=D/V*EXP(-K10*t). On 7th day and 231th day, the detected phenobarbital concentration of therapeutic group, toxic group and lethal group blood preserved at 20℃declined to 76.59%,93.58%,88.69% and 5.15%,3.60%,5.02% of initial concentration respectively(P<0.05). The decomposition half-lifes (t1/2) were 70.9d,61.1d and 36.6d. On 14th day and 231th day, the detected phenobarbital concentration of therapeutic group, toxic group and lethal group blood preserved at 4℃declined to 78.72%,90.33%,84.28% and 20.14%,22.78%, 19.50% of initial concentration respectively(P<0.05). The decomposition half-lifes (t1/2) were 105.7d,97.4 dand 88.5d. On 21th day and 231th day, the detected phenobarbital concentration of therapeutic group, toxic group and lethal group blood preserved at-20℃declined to 83.28%, 91.29%,82.75% and 35.05%,35.71%,30.20% of initial concentration respectively(P<0.05). The decomposition half-lifes (t1/2) were 172.2d,147.5d and 143.8d. On 7th day and 231th day, the detected phenobarbital concentration of therapeutic group, toxic group and lethal group blood 1% NaF and preserved at 20℃, declined to 90.13%,94.15%,89.06% and 15.15%,16.25%, 10.07% of initial concentration respectively, and the decomposition half-lifes (t1/2) were 90.4d, 85.6d and 62.2d(P＞0.05). Conclusion1. The postmortem distribution, postmortem diffusion model (LD50, ig or iv) of phenobarbital in rabbits and the decomposition kinetics model of phenobarbital in preserved human blood have been developed. These models can be applied to the forensic identification and forensic toxicokinetics of phenobarbital poisoning death case.2.The results showed that the order of concentration is most in liver, more in kidney and least in humor vitreous by oral approach and the order of concentration is most in urine, more in liver and least in humor vitreous. These results imply that the postmortem distribution of phenobarbital in organs has significantly effected by different administration approach, through which the administration approach can be concluded. So experiment evidence can prefered for forensic identification of phenobarbital poisoning death through the conclusions.3. There was a postmortem diffusion of phenobarbital in rabbits. Lowering the preserved temperature could slow down or even hinder the postmortem diffusion, but it showed less effect on the urine, muscle and brain. The concentration of phenobarbital detected in the rabbits after the postmortem administration of LD50 was lower than after the antetmortem administration with the same dose by oral approach or vein approach. It should be taken into consideration that the postmortem diffusion and postmortem redistribution can affect the analysis of phenobarbital in the forensic identification of phenobarbital poisoning death. The postmortem diffusion can be used for the identification of antemortem administration and postmortem administration of phenobarbital too.4. Phenobarbital in the preserved blood can be decomposed and its concentration decreased. Low-temperature preservation and bacteriostat (1%NaF) can make the decomposition slow down, prolong the decomposition half-lifes (t1/2). It suggests that the specimen for analysis of phenobarbital should be submitted within 7 days in the forensic identification of phenobarbital poisoning death case; otherwise, samples should be frozen or added with the bacteriostat, submitted and analyzed as soon as possible.5. The decomposition kinetics of phenobarbital in stored blood met the one compartment open model with a first order kinetics. In the forensic identification of phenobarbital poisoning death, the equation as Ct=D/V*EXP(-K10*t) and decomposition kinetics parameter can be used to estimated the phenobarbital concentration in the specimens at sampled time, and provide a scientific evidence for the forensic identification of phenobarbital poisoning death case. |
PDF Full Text Request