Presentation on theme: "Collection, preservation and dispatch of specimen viscera."— Presentation transcript:
Collection, preservation and dispatch of specimen viscera
Introduction Many specimens and samples are obtained during an autopsy as a routine depending on the nature of the case. Post mortem examination is most probably the single opportunity for a medico legal doctor to obtain any type of specimen. It is wise to obtain as must samples in as much detail as possible and to discard them later if not required. In general, the specimens recovered may be designated for several distinct purposes.
In Pakistan, unfortunately, we do not have sophisticated crime detection laboratories or arrangements for the minute forensic serologic, biological or other examination of the samples. Therefore, generally little attention is paid to these vital aspects of crime investigations.
Specimens for crime detection laboratory Clothing Samples of different types of hair Clippings of the fingernails Combing of the pubic hair in sexual assault cases Samples of foreign material recovered from outside or inside of body Tracing of patterned injuries
Specimens for serological/biological examination In sexual assault cases, perineal, vaginal or oral swabs Samples of clotted blood from victim for ABO or Rh grouping.
Samples for histo pathological examination They are not a routine in medico legal autopsy. However, they are taken to diagnose the responsible or contributing disease process (e.g. Acute Myocardial infarction, brain haemorrhage) in sudden unsuspected deaths. To confirm, if in doubt, ante mortem or post mortem nature of the injury. To estimate the age of some injuries or lesions. To document the presence of foreign material deep inside a tissue e.g. Pigmentation in close contact firearm injury.
Samples for toxicological examination In some cases, it may be necessary to exclude or confirm a poison as the cause of death. The doctor has to collect suitable samples for analysis, and to interpret their results in the light of autopsy findings and the circumstances of the death. It should be remembered that it is the doctor, rather then the forensic toxicologist who has to provide the FINAL OPINION as to the cause of death.
Collection of specimen/ Viscera Mnemonic: bbbvshunc
1. Blood Around 25-30 ml of blood is collected and preserved. It should be collected in a bottle, preferably from a peripheral site, such as vessels of the neck, arm or leg. Blood should never be taken from cavities after evisceration, as it will be contaminated from other body fluids. It is also preferable not to collect blood from the heart except in CO poisoining.
2. Urine Urine is obtained by a catheter of a supra pubic puncture before autopsy or by puncture of the bladder after evisceration. Around 100-200ml is collected. If less, then collect the whole quantity.
3. CSF Cerebrospinal fluid is generally not required for toxicological purposes. If required, it is obtained by cisternal or lumbar puncture, puncture of the lateral ventricles or aspiration from the base of the brain after reflecting the frontal lobes. Collect as much fluid as posisble. If a drug is injected Intravenously after death, it will not cross the blood brain barrier.
4. Bile It is directly collected from the gall bladder, as it is too thick to be aspirated by a syringe. It is helpful in morphine and chlorpromazine poisoning.
5. Vitreous A fine hypodermic needle attached to a 5ml syringe is inserted into the outer canthus of the globe after pulling the eyelids aside. the needle is inserted in the centre of the globe and as much vitreous is aspirated from both eyes. Water is injected with the same syringe to restore the shape of the eyeball.
6.Stomach and contents Stomach contents are collected directly into a wide mouthed bottle. The exterior of the stomach is washed and the greater curvature is opened with large scissors. Then the interior is exposed to see any capsules, tablets, etc and preserved separately.
7.Bone and Bone marrow About 200gms of bone should be collected. It is convenient to remove about 10-15cms of the shaft of the femur. Bone marrow is obtained from the sternum, femur or vertebrae.
8. Hairs An adequate sample of around 10gms of head and pubic hairs should be removed by plucking out, complete with roots, and not by cutting and preserved in separate containers.
9. Nails and skin All the nails should be removed entire, from their bed and collected in separate envelopes. A skin piece of at least 2.5cms square from the affected area in case of corrosive poisoning and from thigh or back in case of suspected heavy metal (arsenic) poisoning is taken. In firearm injury cases, a skin portion of suitable size around the entrance and exit wounds should be excised.
Ideally there should be no delay between the collection of specimens and their analysis in the laboratory. If the delay is short, refrigerated storage may be sufficient to preserve the samples. But the transportation of the viscera to the forensic science laboratory and their examination at the end would naturally take some time. To protect from putrefaction to set in and render chemical analysis difficult, certain preservatives should be used.
Preservative for blood The best preservative for blood samples is sodium (or potassium) fluoride at a concentration of 10mg/ml which preserves blood for more than 3 months at room temperature. 0.5mg sodium citrate plus 0.1 mg mercuric chloride is another suitable preservative. For suspected poisoning case excluding oxalic acid, 10ml of blood is mixed with 30mg potassium oxalate (anticoagulant) and 10mg Na fluoride (enzyme inhibitor). For oxalic acid and ethylene glycol, 30mg sodium citrate should be used instead.
Heparin and EDTA should not be used as an anticoagulants since they interfere with the detection of certain poisons (methanol). In case of Carbon monoxide poisoning, a layer to 1-2cm of liquid paraffin should be added immediately over the collected blood sample to avoid exposure to atmospheric oxygen.
Preservatives for other viscera In all cases of poisoning, inclusive of carbolic acid but exclusive of other acids, rectified spirit is used to preserve viscera as well as urine. Alternatively, saturated solution of common salts should be used to preserve viscera other then blood, In all cases of poisoning, inclusive of carbolic acid but exclusive of other acids. 10% formalin is used as a preservative for tissues meant for histo pathological examination.
Method of preservation The stomach, small intestine and their contents should be preserved in one wide mouthed glass bottle. Pieces of liver, spleen and kidney should be placed in another bottle and urine in the third bottle. When additional material is required to be sent, it should be dispatched in separate bottles. Blood should be sent in vials.
The solid organs are cut into small pieces to ensure penetration of the preservative. The bottle should not be completely filled with preservative however it is necessary that complete immersion of the viscera is done. If the material is not completely submerged in the solution, decomposition will take place with the result that gases may form and either undo the lip spilling the contents or even break the bottle.
The stoppers of the bottle should be well fitted, covered with a piece of cloth and tied or string at the ends sealed using a departmental seal. Each bottle should be labelled properly, containing autopsy number, name of deceased, name of the organ, date, time and place of autopsy followed by signature of doctor. The sealed bottles are then put in a viscera box which is locked and the lock is sealed. The key of the box and a specimen of the seal is put in separate envelope and it is also sealed.
Dispatch of Viscera The sealed box and the envelope containing the key is then handed over to the police constable in return of a receipt. He delivers is personally to the office of Provisional Chemical Examiner after obtaining a receipt for the same.
Other documents Along with viscera box, some other documents are also sent: A copy of Panchnama; brief facts of the case, and the case sheet. A copy of autopsy report A letter requesting him to examine the viscera and inform the medical officer of his finding. Unless the viscera are sent to chemical examiner, they are to be preserved for 6 months and then destroyed after obtaining the magistrate assent, or when the investigating officer informs the laboratory that the case is closed.