Toxicology Principles and Management

Toxicology Introduction

The study of toxicology focuses on the effects of poisonous substances on living organisms.

• Principles of Toxicity Management

Management of toxicity involves seven key areas:

Resuscitation (emergency management)

Clinical evaluation

Laboratory investigation

Decontamination of toxins

Enhancing elimination of toxins

Administration of specific antidotes

Supportive treatment

• Resuscitation (Emergency Management)

  Resuscitation of poisoned patients follows the ABCD protocol:

Airway management (avoiding obstruction and hypoxia)

Finger sweep (remove dentures, saliva, etc.)

Optimize airway position (head-tilt/chin-lift or jaw thrust) - avoiding neck injuries

Head down, left sided position (for secretions to drain).

Endotracheal intubation (nasotracheal or orotracheal)

Surgical airway management (laryngostomy and tracheostomy)

Potential causes: flaccid tongue, pulmonary aspiration of gastric contents, respiratory arrest

Signs/symptoms: dyspnea, air hunger, hoarseness, cyanosis, sweating, tachypnea.

Breathing assistance (supplemental oxygen, assisted/mechanical ventilation)

Circulation support (measuring heart rate, blood pressure; vasopressors [e.g. dopamine and norepinephrine] for shock; intravenous fluids; ECG monitoring)

The need for dextrose administration is mentioned but the specific conditions are not explained.

• Clinical Evaluation

History: Gathering information about the incident (type of poison, ingestion amount, duration, source).

• Obtaining info from patients, family, friends, or rescuers if unable to provide their history.

Clinical Assessment: Physical examination helps identify specific clinical features for quicker poison identification/ diagnosis.

Skin color (e.g., red in CO poisoning)

Presence of needle marks (possible drug abuse)

Increased sweating and flushing

Eye examination; Pupil size (dilated or constricted in response to different poisons)

Lacrimation (increased tears)

General GIT (Gastrointestinal Tract) assessment (salivation, dryness, corrosion, abdominal pain, diarrhea & vomiting etc.)

CVS (Cardiovascular System) assessment (tachycardia, bradycardia, blood pressure)

CNS (Central Nervous System) assessment (coma, tremors, convulsions, hyperthermia/hypothermia)

Respiratory Examination: checking for breathing abnormalities like hypoventilation, hyperventilation, pulmonary edema.

Toxidrome: Group of signs & symptoms that occur from exposure to a particular drug or toxin. It can aid identification

C.1. Sympathomimetic Toxidrome:

Results from toxins that stimulate the catecholamines release or toxins preventing catecholamine uptake,

Symptoms include dilated pupils, tachycardia, hypertension, agitation, seizures, diaphoresis. (Drugs such as cocaine, amphetamines)

C.2. Cholinergic Toxidrome:

Results from excess acetylcholine,

Symptoms commonly observed in organophosphate & carbamate insecticide poisoning.

C.3. Opioid Toxidrome:

Results from stimulation of opioid receptors,

Common symptoms include miosis (constricted pupils), CNS depression, and hypoventilation. (Drugs such as heroin and morphine)

• Laboratory Investigation

  Laboratory screening of biological fluids (blood, urine, saliva, spinal fluid, hair etc.) is to help identify toxic agents/ functions of affected organs,

Examples:

Arterial blood gases (measuring PO2 and PCO2)

Electrocardiogram (ECG)

Kidney function tests (creatinine, albumin, BUN)

Liver function tests (ALT, AST)

Electrolytes (Na+, K+, Cl-, Mg+2, Ca+2, HCO3−)

Anion gap (measurement to define the difference between anions and cations in the blood)

Laboratory tests are also performed on tissues of deceased patients.

Testing can be done while toxins/drugs/metabolites are present in the body fluid or tissues.

• Decontamination

Dermal Exposure:

Remove the affected person from the hazardous environment.

Remove contaminated clothing.

Wash the affected area thoroughly with water and/or saline.

• Towels, cloths, etc., must be put into hazardous waste bags.

Topical agents for specific toxins such as olive oil for phenol or calcium gluconate gel for oxalic/hydrofluoric acid, etc.

• Soap water for organophosphorus skin toxicity.

Eye Exposure:

Remove contact lenses (if worn).

Irrigate the eye with normal saline or tap water for minimum 15 min. until tears return to normal pH.

Anesthetic eye drops for corrosive exposure.

• Refer to an ophthalmologist is needed.

GIT Exposure:

Forced emesis (Ipecac syrup): Use to induce vomiting in conscious patients (within a few hours post-ingestion.) Avoid in cases with corrosive toxins or if unconscious/comatose, etc.

Gastric Lavage: Wash out the stomach when emesis is ineffective/contraindicated.

Oral Adsorbents: Activated charcoal (fine, black powder given as slurry with water) is used orally or through a tube to bind to ingested toxins, preventing them from being absorbed into the body,

Whole bowel irrigation: Polyethylene glycol electrolyte solution to flush toxins from the entire bowel.

Contraindications for forced emesis - corrosives, hydrocarbons, petroleum distillates

Other considerations like the lack of bowel sounds, bowel obstruction, constipation, stomach distention & risk of pulmonary aspiration.

Charcoals effectiveness depends on the type of toxin

Charcoal should not be given with Ipecac unless the patient has already vomited.

Cathartics: Saline, magnesium sulfate, citrate, sorbitol. Use with activated charcoal to improve excretion.