Which class of agents is most associated with dizziness, weakness, anxiety, nausea, tachypnea, seizures, and respiratory arrest?

• A. Vesicants
• B. Blood agents
• C. Pulmonary agents
• D. Biological agents

Answer: (B)

Understanding how blood agents affect oxygen use in the body helps explain these symptoms. Blood agents, such as cyanide, block the cell’s ability to use oxygen by inhibiting a key enzyme in the mitochondria (cytochrome c oxidase). Even if oxygen is present in the blood, tissues can’t extract and utilize it, so cells experience functional hypoxia. That rapid disruption of cellular respiration produces early dizziness and weakness, anxiety, and nausea as the brain and other organs become energy-deprived. The body responds with increased breathing (tachypnea) in an attempt to compensate for the hypoxia, and as the toxicity worsens, there can be seizures and ultimately respiratory arrest due to profound CNS and respiratory center involvement.

Other classes don’t fit this pattern as precisely. Vesicants cause skin and mucous membrane blistering rather than rapid CNS and respiratory collapse. Pulmonary agents mainly irritate or injure the respiratory tract, producing coughing and bronchospasm rather than the abrupt systemic hypoxia seen with blood agents. Biological agents are infections with longer incubation periods and different symptom timelines.