Toxicology Lecture 3-1 PDF

Toxicology DR.MAMDOUH ORABY  Introduction Principles of management of toxicity  Principles of toxicity management Management of toxicity should focus on seven major areas: 1) Resuscitation (emergency management) 2) Clinical evaluation 3) Lab investigation 4) Decontamination o...

Toxicology DR.MAMDOUH ORABY  Introduction Principles of management of toxicity  Principles of toxicity management Management of toxicity should focus on seven major areas: 1) Resuscitation (emergency management) 2) Clinical evaluation 3) Lab investigation 4) Decontamination of the toxins 5) Enhance elimination of the toxins 6) Administration of specific antidote 7) Supportive treatment 1- Resuscitation (emergency management) ❑ Resuscitation of poisoned patients follows the ABCD protocol: A: Airway management B: Breathing assistance C: Circulation support D: Dextrose administration  Airway management ❑ Performed to avoid the airway obstruction and hypoxia. Causes of airway obstruction: ▪ Flaccid tongue ▪ Pulmonary aspiration of gastric contents ▪ Respiratory arrest. Signs and symptoms of airway obstruction. ▪ Dyspnea, air hunger & hoarseness, cyanosis, sweating & tachypnea.  Airway management a. Finger sweep method: to remove dentures (if present), saliva, vomitus, blood from mouth. b. Optimize the airway position: Force the flaccid tongue forward Maximize airway opening as follows: I. Head-tilt or chin-lift technique (sniffing position). ▪ The neck is flexed forward ▪ The head is extended backwards ▪ Avoided in case of neck injury.  Airway management II. Jaw thrust technique: ▪ Applied in presence of neck injury ▪ Pull the jaw forward by placing the fingers of each hand on the angle of the mandible just below the ear. ▪ This allows forward movement of the tongue without flexing or extending the neck.  Airway management III. Head down, left sided position: Allow the tongue to fall forward Allow the secretions & vomitus to drain out of the mouth. c. Endotracheal (nasotracheal or orotracheal) intubation. d. Surgical airway management: Laryngostomy & Tracheostomy  Breathing ❑ Assessment of breathing is included if the breathing is slow or fast. ❑ Abnormal breathing is provided with: Supplemental oxygen Assisted (Mechanical) ventilation by using a bag- valve mask or positive pressure ventilation. ❑ Measurement of partial arterial blood gases (indicative for alveolar ventilation; PCO2, 35-45 mmHg; PO2, 75-100 mmHg).  Circulation ❑ Management of circulation includes heart rate, blood pressure, and peripheral circulation. ❑ For maintaining the circulation in case of shock: ✓Patients is kept in the head down position. ✓ Vasopressor's amines (ex; dopamine & norepinephrine) should be injected. ✓Injection of I.V bolus fluids ✓ECG should be monitored  2- Clinical evaluation A- History: ❑ The accurate history of the poisoning indicates: Type of the poison Amount & time & length/duration of ingestion / exposure. Source of the poison ❑ If the patient is unconscious or unable to give any form of history, information may be obtained from the patient family members, friends, relatives, or rescuers.  2- Clinical evaluation B- Clinical assessment: Some poisons produce specific clinical features that strongly predict the type of the poison. I. Examination of the skin i. Skin color: (e.g; red color in CO poisoning & cyanosis in cyanide poisoning & Yellow (jaundice) in acetaminophen, CCL4 poisoning). ii. Presence of needle makers (addiction of drug abuse). iii. Presence of excessive sweating and flushing.  2- Clinical evaluation II. Examination of the eye: ❑ Pupil size ▪ Dilated in alcohol & cocaine ▪ Constricted in opium poisoning). ❑ Increased lacrimation (e.g; Narcotic withdrawal)  2- Clinical evaluation III. GIT Examination: ✓ Presence of salivation (organic phosphates) ✓ Excessive dryness of the mouth. ✓ Corrosion in the mouth (corrosives). ✓ Abdominal colic & diarrhea & vomiting. IV. CVS ▪ Tachycardia, bradycardia, blood pressure, ………… V. CNS ✓ Coma, tremors, convulsions, hyperthermia, hypothermia.  2- Clinical evaluation VI. Respiratory examination: ▪ Hypoventilation, hyperventilation, pulmonary edema. C. Toxidrome: ▪ Is a group of signs & symptoms associated with exposure to a particular category of drugs and toxins. ▪ Presence of specific toxidrome may help identify the toxin(s) or drug(s) and the crucial body systems that may be involved.  Clinical evaluation C.1. Sympathomimetic Toxidrome: ▪ Results from toxins that stimulate the catecholamines release / prevent its uptake ▪ Ex; Cocaine, Amphetamines ▪ Characterized by dilated pupils, tachycardia, hypertension, agitation/seizures, diaphoresis. C.2. Cholinergic Toxidrome: ▪ Results from excess acetylcholine ▪ Ex; Organophosphate & carbamate insecticide poisoning.  Clinical evaluation ▪ Characterized by Diarrhea, Urination, Miosis, Bradycardia, Bronchospasm, Lacrimation, Lethargy, Emesis, Salivation, Sweating (DUMBLES syndrome). C.3. Opioid Toxidrome: ▪ Results from stimulation of opioid receptors ▪ Symptoms include miosis, CNS depression, and hypoventilation. ▪ Ex; Heroin & Morphine.  3- Laboratory investigation ▪ Laboratory screening is done on biological fluids ▪ Facilitate the identification of the toxic agent & organ functions ▪ It can be also performed on tissues of dead victims. ❑Examples of laboratory investigations: ✓Arterial blood gases; measuring PO2 & PCO2 (hypoventilation; ↑ PCO2 & ↓ PO2). ✓Electrocardiogram (ECG). ✓Kidney function tests: e.g: Creatinine & Albumin & BUN ✓Liver function tests: e.g: ALT & AST  Laboratory investigation ✓ Electrolytes: such as Na+, K+, Cl-, Mg+2, Ca+2, HCO3-. ▪ Ex: Digitalis overdose causes hypokalemia (↓ K+). ❑ N.B: Anion gap is the measurement of the difference between anions and cations in the blood. ▪ Anion gap = (Na + + K+) - (HCO3- + Cl -) ▪ The normal value for the anion gap is about (8 to 16 mEq/L). ▪ High anion gap may indicate metabolic acidosis that can result from accumulation of acids in the blood (ex: salicylates)  Laboratory investigation ❑ blood or urine is frequently used for Lab investigation ❑ Saliva, spinal fluid may also be used. ❑ Hair can be used as an indicator for specific toxins. ❑ The test sample must be collected while the drug or its metabolite is in the body fluid or tissue used for testing. Ex: Cocaine is a rapidly metabolized drug; however, its metabolite, benzoylecgonine, can be detected in the urine for several hours after cocaine use.  4- Decontamination ❑ Performed to prevent or delay the absorption of the toxic agent. 1- Decontamination from dermal exposure: ❑ Rapid decontamination of corrosives & easily absorbed toxins from the skin through: ✓Transfer the patient from toxic environment. ✓Remove contaminated clothes, wash the skin with warm water or saline. ✓All towels and clothes should be put into hazardous waste bags. ✓Topical agents for chemical exposure could be used: ▪ Olive oil for phenol toxicity ▪ Calcium gluconate gel for oxalic acid & hydrofluoric acid  Decontamination ▪ Soap water for organophosphorus skin toxicity 2- Decontamination of eye exposure ✓Remove contact lenses, if present. ✓Irrigate the eyes for at least 15 min. with normal saline or tap water (irrigation should be continued till pH of tears returns to normal). ✓ Application of anesthetic drops if the eye is affected by corrosives. ✓Patient should be referred to an ophthalmologist.  Decontamination 3- Decontamination of GIT exposure A- Forced emesis: I. Ipecac syrup: an emetic agent (easily administered at home). ▪ It contains irritating chemicals (emetine & Cephaeline ) that: Activate the peripheral sensory receptors in GIT. Activate the vomiting center in the brain (CTZ). ▪ It induces emesis within 30 min. ❑ Indications for using forced emesis: 1) Conscious patients (not more than 4-6 hr post ingestion of a poison). 2) Substances that aren’t well absorbed by activated charcoal (Enteric coated or sustained release tablets).  Decontamination 3) The presence of bulk quantities of undissolved tablets or capsules. ❑ Contraindications of using forced emesis: 1. Corrosive acid or alkali & Convulsant & hydrocarbon. ▪ Emesis of corrosive → further damage to the esophagus. ▪ Emesis of a convulsant may worsen seizures. ▪ Petroleum ingestion → aspiration pneumonia 2. Unconscious or comatose patients or patients with severe CVS disease.  Decontamination ❖ In unconscious patients, vomitus can be aspirated into the lungs causing pneumonia. 3. Young infants less than 6 months. ❑ Dose ▪ Adults 30 ml. ▪ Children (5-12 years) 20 ml. ▪ Children (1-5 years) 15 ml. ▪ Children (6 months-1 year) 10 ml. II. Apomorphine (S.C): produce rapid emetic action within 1-3 min Stimulates vomiting center in the brain (CTZ).  Decontamination B- Gastric Lavage: ▪ Process of washing out stomach with solutions such as saline, water, Na+ bicarbonate, Ca+2 salts,…………….. ▪ Lavage is indicated when: ✓ Emesis is contraindicated/ ineffective ✓ The poison must be quickly removed from the stomach.  Decontamination ❑ Indications: ✓ Semiconscious & unconscious patients. ✓ When emesis is ineffective or contraindicated. ❑ Contraindications: ✓ Corrosives & petroleum distillate (risk of aspiration) ✓ Seizures ❑ Complications/hazards: ✓ Esophageal rupture & bleeding ✓ The tube may be accidentally inserted into the trachea ✓ ↑ the risk of gastric delivery of tablets into intestine ✓ Aspiration of gastric content  Decontamination C- Oral adsorbents: ▪ Adsorbents are solid substance that attracts and holds another substance to its surface (adsorption) → ↓ poison absorption from GIT ▪ Ex; Activated charcoal ❑ Activated charcoal adsorbs or traps the drug / toxin to its large surface area → charcoal-chemical complex ▪ It is a fine, black powder given as a slurry with water ▪ Given orally or by nasogastric / orogastric tube after ingestion of the toxin.  Decontamination ❑Contraindications: ✓ Absence of bowel sounds ✓ Bowel obstruction ❑ Adverse effects: ✓ Constipation (cathartics are used) ✓ Distension of the stomach (↑ risk of pulmonary aspiration). ❑ N.B: in children, sorbitol is added to charcoal to improve the taste, and serve as a cathartic)  Decontamination ❑ Charcoal should be taken within 30 min. of poison ingestion Except in: i. Anticholinergics & sedatives → slow gastric emptying Charcoal can be given up to 6-8 hr. following poison ingestion. ii. Salicylates ingestion → salicylates stick to gastric mucosa Charcoal can be given 9-10 hrs. later ❑ N.B: Charcoal isn’t effective for adsorbing hydrocarbons, heavy metals, iron, inorganic corrosives, cyanide.  Decontamination ❑ Caution: ▪ Charcoal should not be given within 30 min of Ipecac unless the patient has already vomited? ✓Because the active substances (emetine & Cephaeline) found in Ipecac syrup can be adsorbed by the activated charcoal, preventing the vomiting effect of Ipecac.  Arsenic Decontamination D- Cathartics: ▪ Commonly used cathartics are: ✓ Saline ✓ Magnesium sulphate & citrate ✓ Sodium citrate ✓ Sorbitol ❑ Cathartic is usually given with activated charcoal to: Quicken the excretion of charcoal toxin complex Counteract the constipating effect of charcoal.  Arsenic Decontamination E- Whole bowel irrigation: ▪ Polyethylene glycol electrolyte solution cleans the entire bowel through the enteral administration. ▪ Used for sustained release & enteric-coated drugs & iron & and packets of illicit drugs. ▪ Polyethylene glycol is administered through a nasogastric tube until the rectal effluent resembles the infusate. It can be also given orally. Thank You