Prehospital Academy Lesson 27.8
Toxicology: Asphyxiant and Inhalants
This lesson delves into the critical area of asphyxiant and inhaled toxidromes, providing advanced EMS providers with the knowledge to identify, assess, and manage patients exposed to these highly dangerous substances. Prompt recognition and aggressive intervention are paramount for patient survival.
Carbon Monoxide (CO) Poisoning
Carbon monoxide is a colorless, odorless, and tasteless gas, making it particularly insidious. It is a common EMS call, especially during colder months.
Sources:
Gas-powered heaters in confined spaces, house fires, running vehicles in closed garages, faulty furnaces, generators.
Pathophysiology:
CO displaces oxygen at the hemoglobin level due to its much higher affinity for hemoglobin (200-250 times greater than oxygen).
This forms carboxyhemoglobin (COHb), which prevents oxygen from binding to hemoglobin and also shifts the oxygen-hemoglobin dissociation curve to the left, hindering oxygen release to tissues.
Cellular suffocation occurs, not due to lack of air movement (asphyxiation), but due to the inability of red blood cells to deliver oxygen at the cellular level.
Clinical Presentation:
Symptoms are highly variable and often vague, mimicking other conditions (e.g., flu, food poisoning).
Mild: Headache (often "band-like"), fatigue, nausea, dizziness.
Moderate: Tachycardia, tachypnea, confusion, weakness, blurred vision.
Severe: Unconsciousness, seizures, coma, cardiac arrest, ultimate asphyxia.
"Cherry-red" skin: A classic but rare and late sign.
Management:
Scene Safety: Crucial. Responders must ensure the environment is safe (e.g., CO detectors, fire department clearance) before entry.
Remove from Environment: Immediately move the patient to fresh air.
Oxygenation: Administer 100% oxygen via a non-rebreather mask or bag-valve mask. This helps displace CO from hemoglobin.
Airway/Breathing: Establish and maintain an airway. Assist ventilations if inadequate. Consider CPAP or intubation/mechanical ventilation for severe cases.
Monitoring: Pulse oximetry may be falsely high (due to COHb being read as oxyhemoglobin); use CO-oximetry if available. Monitor ECG.
Transport: Rapid transport. Consider transport to a facility with hyperbaric oxygen therapy (HBOT) if available, as HBOT is the definitive treatment for severe CO poisoning.
Chlorine Gas Toxicity
Chlorine gas (Cl2) is a highly reactive chemical commonly used in industrial processes, water purification, and found in some household cleaning products. Accidental exposure can occur from mixing incompatible cleaning agents (e.g., bleach and ammonia).
Pathophysiology:
Chlorine gas reacts with water in mucous membranes (respiratory tract, eyes) to form hydrochloric acid (HCl) and hypochlorous acid (HClO).
These acids cause direct corrosive injury, inflammation, and cellular damage to the respiratory tract.
Severity of injury is dose-dependent and related to water solubility. Chlorine is moderately water-soluble, so it tends to cause both upper and lower airway irritation.
Clinical Presentation:
Minor Exposure: Burning sensations in eyes, nose, throat; slight cough, irritation.
Moderate Exposure: Dyspnea, wheezing, bronchospasm, chest tightness, excessive secretions, eye irritation, lacrimation.
Severe Exposure: Cyanosis, severe respiratory distress, pulmonary edema, seizures, shock, cardiac arrest.
Management:
Scene Safety: Remove patient from the area. Triage (if multiple patients). Responders may require SCBA.
Decontamination: Remove contaminated clothing. Irrigate eyes and skin with large amounts of water or saline.
Airway/Breathing: Priority is respiratory support. Administer high concentrations of humidified oxygen. Be prepared to treat bronchospasm (e.g., albuterol via nebulizer) and pulmonary edema.
IV Access/Fluids: Establish IV access for supportive care.
Transport: Rapid transport to a medical facility. Patients with respiratory distress are the priority.
Cyanide Poisoning
Cyanide (hydrogen cyanide, HCN) is a rapid-acting and deadly poison, often colorless with a bitter almond scent (though not everyone can smell it).
Sources:
House fires (combustion of plastics, wool, silk, polyurethane), industrial chemicals, certain pesticides, some plants.
Pathophysiology:
Cyanide binds to cytochrome oxidase in the mitochondria, blocking cellular respiration and preventing cells from utilizing oxygen for energy production (histotoxic hypoxia).
Cells literally suffocate, even though oxygen is present in the blood.
Clinical Presentation:
Extremely rapid onset, especially via inhalation. Death can occur within seconds to minutes.
Early: Headache, nausea, vomiting, anxiety, vertigo, weakness, dyspnea.
Late/Severe: Altered mental status, seizures, coma, hypotension, bradycardia, cardiac arrest.
Skin: May appear pink or flushed, but can progress to cyanosis.
Odor: Bitter almond odor on breath (if detectable).
Management:
Scene Safety: Paramount. Responders must be protected (SCBA).
Remove from Environment: Immediately move the patient to fresh air.
Oxygenation: Administer 100% oxygen via non-rebreather mask or bag-valve mask ventilation.
Antidotes (ALS/Paramedic Level): Treatment must be initiated as quickly as possible.
Cyanide Antidote Kit (e.g., Cyanokit - hydroxocobalamin, or Lilly kit - amyl nitrite, sodium nitrite, sodium thiosulfate): These kits are generally not on every ambulance but should be accessible via ALS units or hospitals.
Goal: To displace cyanide from cytochrome oxidase or to bind with cyanide to form non-toxic compounds.
Supportive Care: Manage airway, breathing, circulation. Treat seizures.
Transport: Rapid transport to a medical facility. Notify receiving facility immediately of suspected cyanide poisoning.
Critical Thinking Questions
You respond to an unconscious patient found in a garage with a running car. The patient is pale, tachypneic, and disoriented. What is your primary suspicion, and what immediate, critical intervention is required?
Explain why pulse oximetry readings may be unreliable in carbon monoxide poisoning and what alternative monitoring strategy would be more accurate.
A patient is exposed to chlorine gas after mixing cleaning products. What are the expected physiological effects, and what key prehospital interventions are necessary to mitigate respiratory compromise?
You encounter a patient with rapid onset of collapse, presenting with altered mental status and an odor of bitter almonds on their breath, having been rescued from a burning building. What is the most likely toxic agent, and why is prompt antidote administration critical?
Discuss the importance of scene safety and personal protective equipment for EMS providers responding to incidents involving asphyxiant and inhaled toxidromes.