Clinical Toxicology Evaluation & Management

Clinical Toxicology - Initial Evaluation & Management

• Clinical toxicology focuses on the effects of drugs and chemicals on humans (and sometimes other animals).
• It often deals with drug overdoses and poisonings, identifying the substance and its amount in the body.
• It overlaps with other sciences like biochemistry, pharmacology, and pathology.
• It concerns the adverse effects of drugs, chemicals, etc.
• All poisoned patients should be managed as potentially life-threatening, even if their appearance seems normal.
• Initial evaluation should be similar for all cases, irrespective of the toxin ingested (routine poison management).

Outline of Clinical Toxicology

• Clinical Toxicology?
• Approaches and Initial Evaluation
• Management
• Definitive care with poisoning
• Supportive Care and Monitoring

Approach to Poisoned Patients (ABCDEs)

• Airway: Keep airways open, remove any suspected obstructing materials. Loss of airway-protective reflexes can cause death (e.g., flaccid tongue, aspiration of gastric contents).
• Breathing: Evaluate respiratory rate and oxygen saturation. If oxygen saturation monitoring isn't available, but respiratory rate is elevated, consider supplemental oxygen.
• Circulation: Prompt assessment of vital signs and hydration status is crucial. Check blood pressure, pulse rate/rhythm, begin continuous ECG monitoring, secure venous access, draw blood for routine studies, and initiate IV infusion with normal saline or isotonic solution if the patient is hypotensive.
• Disability (Neurological): Decreased level of consciousness is a critical complication. Check blood sugar levels; if below 72 mg/dL, administer 50 mL of 50% dextrose IV. Treat toxic seizures with IV benzodiazepines; refractory seizures may need barbiturates.
• Exposure (Temperature): Consider the possibility of toxic syndromes associated with hyperthermia. Toxic levels of certain drugs can lead to significantly elevated body temperatures.

Definitive Care with Poisoning

• Identify the poison.
• Obtain accurate and complete history from sources other than the patient (e.g., family, friends, pharmacist, scene).
• Determine the time and amount of ingestion.

Supportive Care and Monitoring

• Acute poisoning is a dynamic illness; repeated examinations and ongoing clinical assessment and management are necessary.

Physical Examination

• Important aspects of the physical examination include the following:
  • Vital signs (pulse rate, respiratory rate, blood pressure, temperature, oxygen saturation)
  • Neurological examination (pupil size, Glasgow Coma Scale (GCS), mental status, tone, reflexes, clonus, focal signs)
  • Skin (color, sweating)
  • Mouth/salivation, bowel sounds, urinary retention
  • Evidence of trauma

Risk Assessment

• Early and accurate risk assessment is crucial for managing poisoned patients.
• It helps predict the likely clinical course, potential complications, and develop a management plan.
• Five steps of risk assessment:
  • Agent(s): Assess if the ingested agents are likely to cause significant toxicity.
  • Dose(s): Calculate the dose taken in mg/kg body weight to predict the likelihood of significant toxicity.
  • Time since ingestion: Important for determining the likely clinical progress.
  • Clinical features and progress: Correlate the patient's clinical features and progress with the dose taken and time since ingestion.
  • Patient factors (weight and co-morbidities): Consider individual patient factors that may put the patient at particular risk.

Investigations

• Blood sugar level
• ECG (checking rate: bradycardia/tachycardia; rhythm)

Management of Poisoning

• Focus on:
  • Preventing further absorption of the poison
  • Increasing poison elimination
  • Using an antidote (if appropriate)

Prevention of Further Poison Absorption

• Dermal exposure: Remove all clothing, wash skin with soap and water for at least 30 minutes.
• Eye exposure: Wash conjunctiva with running water or normal saline for 20 minutes. Remove solid corrosives with forceps.
• Gastrointestinal (GIT) exposure: Induce vomiting (if contraindications are absent), perform gastric lavage (if emesis failed), use activated charcoal, use cathartics, and consider whole bowel irrigation.

Induction of Emesis (Vomiting)

• Ipecac syrup is a method to induce vomiting. It's effective within 30 minutes of ingestion but should no longer be used routinely.
• Contraindications for emesis: convulsions, corrosives, hydrocarbons, coma, and age less than 6 months.

Gastric Lavage

• Performed in hospitals when emesis fails or is contraindicated.
• Effective within 4-6 hrs of ingestion; involves an assistant with a suction machine to remove dentures, mucus, vomitus, and selecting appropriate tube size.

Activated Charcoal

• Adsorbs a wide variety of drugs and chemicals, staying in the GI tract until a bowel movement.
• Adult dose: 1 gram per kilogram (gm/kg).
• Indications: ingestion within one hour, patient at risk of significant toxicity, NOT at risk of airway compromise.
• Contraindications: if another oral antidote is given, seizures, coma, or corrosive ingestion. Agents that are not bound to charcoal include hydrocarbons, alcohols, and corrosives (acids, alkalis).

Cathartics (Laxatives)

• Substances that enhance the passage of material through the GIT, decreasing contact time between the poison and absorptive surfaces.
• Types: Osmotic (e.g., magnesium sulfate) and irritant (e.g., castor oil).
• Contraindications: GIT hemorrhage, recent bowel surgery, intestinal obstruction.

Whole Bowel Irrigation (WBI)

• Goal: Clean the GIT of non-absorbed toxins, generally using polyethylene glycol electrolyte solutions.
• Indications: poorly absorbed toxins, massive ingestion of drugs, sustained-release or enteric-coated preparations, or removal of illegal drug packets.

Antidote

• Therapeutic substance to counteract the toxic effects of a specific substance.
• Mechanisms:
  • Form a nontoxic complex that can be excreted (e.g., chelators).
  • Accelerate detoxification of the poison (e.g., N-acetylcysteine, thiosulfate).
  • Decrease rate of conversion of poison into toxic metabolites (e.g., fomepizole).
• Types:
  • Interfere with the poison through physical properties (e.g., adsorption by activated charcoal, coating).
  • Chemical action (e.g., oxidizing agents for cyanide toxicity, reducing agents for methemoglobinemia).
  • Physiological antagonism (e.g., competitive or noncompetitive antagonists, chelating agents - like Dimercaprol (BAL), and specific antibodies or antibody fragments).

Enhancement of Poison Excretion

• Forced diuresis: Increasing urine production to flush out toxins (e.g., manipulating urine pH, mannitol).
• Dialysis: Removing toxins through a semi-permeable membrane when renal function is impaired (e.g., peritoneal dialysis, hemodialysis).
• Hemoperfusion: Using a column containing an adsorbent material (e.g., charcoal or resin) to remove toxins from the blood.

This quiz delves into the initial evaluation and management of clinical toxicology cases, focusing on drug overdoses and poisonings. It explores important approaches, supportive care, and the definitive care needed for poisoned patients. Test your knowledge of the protocols and practices in clinical toxicology.