Introduction to toxicology, Slides of Toxicology

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Toxicology

by shareef kavuma

by shareef

IV. Laboratory specimens A. Specimen collection Blood, Urine, Stomach contents, Scene residues (non-biological). B. Specimen transport and storage C. Specimen examination Blood ,Urine, Stomach contents and scene residues. V. Apparatus, reference compounds & reagents A. Apparatus B. Reference compounds and reagents

VI. General laboratory tests in clinical toxicology A. Biochemical tests Blood glucose: Electrolytes, blood gases and pH Plasma enzymes Cholinesterase activity Measurement of serum osmolality B. Hematological tests Leukocyte count Blood clotting Carboxyhemoglobin

Because the financial and personnel resources required for such complete “screens” would be prohibitive, clinical laboratories must employ selective procedures suitable for the victim population in question. Therefore in most cases in clinical or hospital-based settings, tests are done for only a finite number of compounds, generally the more common drugs of abuse. Ideally, a diagnosis of poisoning would be made clinically, with the laboratory playing a confirmatory role. In our coming lectures it is meant to discuss the basic structures which are said to be vital in clinical toxicology laboratory.

I. The role of clinical toxicology laboratory Most poisoned victims can be treated successfully without any contribution from the laboratory other than routine clinical biochemistry and hematology. This is particularly true for those cases where there is no doubt about the poison involved and when the results of a quantitative analysis would not affect therapy. However, toxicological analyses can play a useful role if the diagnosis is in doubt, the administration of antidotes or protective agents is possible, or the use of active elimination therapy is being considered and in drug monitoring.

III. Steps in undertaking an analytical toxicological investigation. The analysis dealing with a case of poisoning is usually divided into pre-analytical, analytical and post-analytical phases. Pre-analytical phase: -

• Obtain details of current admission, including any circumstantial evidence of poisoning and results of biochemical and hematological investigations.
• Obtain victim's medical history, if available, ensure access to the appropriate sample(s), and decide the priorities for the analysis.

Analytical phase: -

• Perform the agreed analyses. Post-analytical phase: -
• Interpret the results and discuss them with the clinician looking after the victim.
• Perform additional analyses, if indicated, on the original samples or on further samples from the victim.

No single specimen type is universally appropriate for identification of toxic agents. The selection of specimen type is based on both the toxicokinetics of the suspected agent and laboratory methodology. In general, quantitative tests are performed on serum or whole blood, and qualitative tests are performed on urine and gastric contents. When in doubt, obtain as many specimen types as possible and forward to the laboratory, where the most appropriate specimens can be selected. For the broadest possible screening (which, again, is rarely needed, especially in emergency toxicology), minimally, blood and urine should be sent (detailed practical aspects of analytical toxicology is discussed later on).

A. Specimen collection Urine, Stomach contents, Scene residues (non- biological), The blood B. Specimen transport and storage C. Specimen examination Urine, Stomach contents and scene residues V. Apparatus, reference compounds & reagents A. Apparatus B. Reference compounds and reagents

Clinical pathology = is the science and practice of medical diagnosis by laboratory examination and analysis of tissue specimens (biopsies), body fluids & other samples. Clinical pathology is subdivided into virology, bacteriology clinical chemistry, serology & pathological histology. Clinical governance = is a systematic approach to raising standards of health care & tackling poor performance in hospitals.

Monitoring = Close surveillance or supervision, especially of people liable to suffer a sudden or dangerous deterioration in health. Monitoring involves checks of various parameters such as pulse rate, respiration rate, temperature, the condition of the pupils, the level of consciousness, the degree of appreciation of pain, and various blood gas concentrations such as oxygen & carbon dioxide. Long-term instrumentation display of the ECG is also common on monitoring and this may also be recorded for diagnostic purposes, using computer analysis.

Knowledge of the approximate dose ingested is important because in certain cases the use of analytic methods designed for therapeutic monitoring, not screening may be necessary. C. Time of ingestion and sampling Knowledge of both ingestion and sampling time is necessary to determine the degree of drug absorption; with serial determinations, knowledge of sampling times is critical, as a single quantitative level may be misleading and must be correlated with the time of ingestion. Serial levels, timed appropriately with respect to the pharmacokinetics of the agent, document that the concentration has peaked, which helps guide further therapy.

D. Clinical presentation Knowledge of the clinical presentation helps the laboratory select the most appropriate screening procedures. The screening procedure for a victim with a depressed level of consciousness is entirely different from conscious victim. E. Location of the victim Location of the victim to the clinical laboratory determines the type of the test that is going to be done (e. g depending on its simplicity).