Toxicology CEN Study Guide

Toxicology CEN Study Guide

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Practicing with Practice CEN Study Guide enables students to develop efficient test-taking strategies, such as elimination techniques and time management.

Toxicology CEN Study Guide

Acids and Alkalis

Pathophysiology    

Acids are compounds that release hydrogen ions and taste sour; alkalis are compounds that accept hydrogen ions and are slippery or soapy. On the pH scale (1 to 14), acids have a value lower than 7, alkalis have a value greater than 7, and 7 is neutral. Ingestion of acids and alkalis is most common in young children. Ingestion in adults is usually linked to severe mental illness or suicidal behaviors.

  • Common household acids: swimming pool and toilet cleaners, battery acid, anti-rust cleaners
  • Common household alkalis: common bleach, drain cleaner

Ingestion of acids usually causes injuries to the upper respiratory tract as the pain and sour taste prompt gagging or spitting, which may lead to aspiration. The acid may also cause coagulative necrosis in the stomach. Alkali ingestion will cause liquefactive necrosis in the esophagus and will continue to cause damage until it has been neutralized.

Physical Examination

  • Drooling
  • Dysphagia 
  • Excessive thirst
  • Visible oral burns
  • Gi pain
  • Emesis (can appear brown)
  • Bleeding in mouth, throat, or stomach
  • Signs and symptoms of esophageal perforation
  • Stridor or dyspnea

Diagnostic Tests

  • Upper GI endoscopy to evaluate damage

Management

  • Manage airway; intubation for patients with severe oropharyngeal edema or necrosis
  • Supportive care for symptoms: analgesics, IV fluids

Contraindicated treatments include

  1. Gastric emptying by emesis
  2. Activated charcoal 
  3. Neutralizing agents
  4. Gastric lavage
  5. Nasogastric tube
  • Immediate surgery for perforation or necrosis

Carbon Monoxide

Pathophysiology

Carbon monoxide (CO) displaces oxygen from hemoglobin, which prevents the transport and utilization of oxygen throughout the body. Mild CO poisoning can be resolved in the ED; severe CO poisoning can lead to myocardial ischemia, dysrhythmias, pulmonary edema, and coma. Sources of CO include smoke from fires, malfunctioning heaters and generators, and motor vehicle exhaust. CO poisoning and cyanide poisoning often occur together.

Physical Examination    

  1. Headache
  2. Altered LOC or confusion
  3. Dizziness
  4. Visual disturbances
  5. Dyspnea on exertion
  6. Nausea and vomiting
  7. Muscle weakness and cramps
  8. Syncope, seizure, or coma

Diagnostic Tests

CO-oximetry: normal range is <3% (<12% for smokers)

Management    

  • 100% oxygen through non-rebreather 
  • Hyperbaric oxygen may be used to treat patients with
  • Carboxyhemoglobin level greater than 25%
  • Cardiopulmonary complications
  • Loss of consciousness
  • Severe metabolic acidosis

Cyanide

Pathophysiology    

Cyanide interferes with the production of ATP in mitochondria. Cyanide poisoning is rare but usually fatal without medical intervention. Sources of cyanide include smoke from fires, medications (e.g., sodium nitroprusside), and pits/seeds from the family Rosaceae (which includes bitter almonds, apricots, , peaches, and apples). 

Physical Examination

  • Bitter almond smell on breath
  • Anxiety or agitation
  • Headache
  • Confusion
  • Bloody emesis
  • Diarrhea
  • Flushed, red skin
  • Tachycardia and tachypnea
  • Hypertension

Management    

  • Decontaminate patient
  • 100% oxygen through a non-rebreather; intubation usually required
  • IV fluids
  • Activated charcoal if airway is not compromised
  • Cyanide antidotes include: hydroxocobalamin, amyl nitrite, sodium nitrite, and sodium thiosulfate

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