Study On The Forensic Toxicokinetics Of Lidocaine Metabolites

Objective:1. To establish the simultaneous analysis of lidocaine and its metabolites in living samples by LC-LIT-MS and HPLC.2. To establish the Postmortem distribution, Postmortem diffusion, Postmortem redistribution, metabolic kinetic, decomposition kinetic models of lidocaine and metabolites in dogs.3. To study the Postmortem distribution, Postmortem diffusion, Postmortem redistribution, metabolic kinetic, decomposition kinetic models of lidocaine and metabolites in dogs.Methods:1. Extractionand analysis method: Diazepam(internalstandard), lidocaine, MEGX, GX were added in specimens. Liquid-liquid extraction, online solid-phase extraction method.The qualitative analysis was based on LC-LIT-MS.The quantitative analysis was based on an internal standard method and calibration Curve.2. Postmortem distribution: According to the does of clinical epidural anesthesia(10.665 mg/kg) to inject the lidocaine through subarachnoid, epiduraland and femoral vein.Collecting the brain, spinal cord(neck, chest, lumbar and sacral segment), cardiac, lung,liver, spleen, kidney, blood, peripheral blood, bile after breathing, heartbeat and other vital signs disappear entirely, waiting for detection at-20 ℃.3. Postmortem redistribution: According to 0.5 times(6.34 mg/kg) and five times(63.4mg/kg) does of the clinical epidural anesthesia to inject the lidocaine through subarachnoid,epidural. After breathing, heartbeat and other vital signs disappear entirely, the blood,peripheral blood, liver, brain were collected respectively in 0,12,24, 36 and 72 hours,keeping waiting for detection at-20 ℃.4. Postmortem diffusion: Dogs were killed by air suffocation, to inject lidocaine through the epidural at 1 hour after breathing, heartbeat and other vital signs disappear entirely. Collecting blood, peripheral blood, heart, brain, lung, liver, spleen, kidney, the left leg muscle In 0.5and 72 hours, waiting for detection at-20 ℃.5. Metabolic kinetic of lidocaine: According to the does of the clinical subarachnoid anesthesia(2.665mg/kg) and epidural anesthesia(10.665mg/kg) to inject respectively the lidocaine through subarachnoid, epiduraland and femoral vein. Venous blood was collected After dosing 0, 5, 10, 20, 40, 60, 120, 200, 420, 1440, 2880, 4320 mins, keeping waiting for detection at-20 ℃.6. Decomposition kinetic of lidocaine: According to the does of the clinical epidural anesthesia(10.665mg/kg) to inject the lidocaine through femoral vein. Femoral venous blood were collected about 300 ml after 0.5 h and saved respectively at 20℃, 4℃,-20℃and 20 ℃ + 1% Na F; the blank venous blood were divided into three parts, adding lidocaine, MEGX and GX respectively according to the content of lidocaine, MEGX and GX when the dog died in poisoning group. Each parts of blood was saved respectively at20℃, 4 ℃,-20 ℃ and 20 ℃+1% Na F,which were detected at 1, 10, 15,30,45 days.7. Statistical methods and other software: Using SPSS 20 software for various mean variance analysis and t test data.Win Nonlin pharmacokinetic software.Result:1. The lidocaine,megx,gx could be detected simultaneously by LC-LIT-MS and HPLC.The limit of detection was 0.004 ng for lidocaine, and 0.01 ng for megx and gx respectively.The limit of quantification was 0.01ng/m L for lidocaine,and 0.2ng/m L for megx,gx, the linearity was over the range of 0.01~160 and 0.8~200ng/m L(ng/mg) respectively.2. The highest content of MEGX and GX respectively was in the lung and kidney after dogs death by subarachnoid administration, The least content of MEGX and GX respectively was in thebile; The highest content of MEGX and GX respectively was in the lung after dogs death by epiduraland administration, The least content of MEGX and GX respectively was in thebile; The highest content of MEGX and GX respectively was in thelung after dogs death by femoral vein administration, The least content of MEGX and GX was in the bile.3. Postmortem redistribution: Small dose of lidocaine was injected into the body through subarachnoid.The content of lidocaine was declined with time, but it was on the rise in the brain. MEGX could be detected in Blood, peripheral blood, liver, and brain tissue,its content change was quite stable;Large dose of lidocaine was injected into the body through subarachnoid, the content of lidocaine was on the rise in blood, peripheral blood and brain over time, MEGX could be detected in the liver. Small dose of lidocaine was injected into the body through epidural,the content change of lidocaine was similar in blood, peripheral blood and brain over time,it is relatively stable in the liver. blood, MEGX could not be detected in Blood, peripheral blood, liver and brain; Large dose of lidocaine was injected into the body through epidural, the content of lidocaine was declined in the blood over time, the content change of lidocaine was relatively stable in the peripheral blood and liver, brain, but it is on the rise in brain, MEGX could be detected in the liver.4. The vital signs of dogs were disappear entirely after 0.5h, the content of lidocaine in peripheral blood was the highest, the second was in the brain, the least was spleen. The content of lidocaine in the brain was the highest at 72 h, followed by peripheral blood, the least was spleen. MEGX and GX could not have been checked out in all the samples.5. Metabolic kinetic: The absorption half-life of GX, MEGX in femoral venous blood were 24.65 and 4.81 min through subarachnoid, elimination half-life was 265.08 and71.53 min. Tmax was 93.13 and 20.09 min respectively. Elimination half-life of Lidocaine was 72.31 min.The absorption half-life of GX, MEGX in femoral venous blood were 24.65 and 4.31 min through epidural, elimination half-life was 514.54 and 162.56 min. Tmax was113.49 and 23.19 min respectively. The absorption half-life of GX, MEGX in femoral venous blood were 49.15 and 0.22 min through femoral vein, elimination half-life was218.33 and 81.88 min. Tmax was 136.46 and 1.89 min respectively. Elimination half-life of Lidocaine was 49.22 min.6. The blank group was stored in 20 ℃ + Na F and 20 ℃, MEGX and GX could be detected in adding lidocaine blood on the 81 th day, the MEGX and GX could be detected in blood added lidocaine and stored different condition on the 115 th day. The decomposition of MEGX and GX was slow in blank group at-20 ℃, the decomposition of MEGX and GX was from fast to slow in infected group: 20 ℃ > 20 ℃ + Na F >4 ℃>-20 ℃.Conclusion:1. A simultaneous detection of lidocaine and its metabolites was established in specimen by LC-LIT-MS and HPLC, which could be used for the detection of lidocaine and its metabolites in the study on the forensic toxicokinetics and the forensic identification of lidocaine poisoning death.2. Lidocaine and its metabolites MEGX, GX could be detected in poisoned dogs by different way. The postmortem distribution characteristic of lidocaine was similar through subarachnoid and epidural injection, but different from intravenous; The lung could be as the first choice for examination when MEGX and GX need to be detected in the forensic identification of lidocaine poisoning death cases.3. There was a postmortem redistribution of lidocaine through subarachnoid and epidural anesthesia in dogs, MEGX wasn’t.4. Lidocaine could occur postmortem diffusion. Lidocaine, MEGX and GX could be deteted in poisoned blood and tissue of the living dogs, but lidocaine was only detected in in poisoned blood and tissue of postmortem dogs, MEGX and GX could not be detected.According to the detection of MEGX and GX or not could distinguish infected and infected after death of lidocaine.5. Metabolism discipline of lidocaine, MEGX and GX was different in poisoned dogs through different ways. Using relationship equation ratio of lidocaine, MEGX and GX with time to calculate using drug theory time of lidocaine, which closed to actual time, the inference method was expected to be the forensic identification of lidocaine poisoning death cases.6. Lidocaine, MEGX and GX could decompose in poisoned blood and blank added blood, decomposition product was the same to its metabolites; Decomposition of lidocaine,MEGX and GX in the poisoned group was faster than the blank added group under the same condition; Decomposition of lidocaine, MEGX and GX in poisoned and the blank added group at-20 ℃ was slower than at 20 ℃ + Na F, 20 ℃ and 4 ℃. Specimen should be kept at low temperature and were timely detected.