Pulmonary Toxicology

Question 1

What is pulmonary toxicology?

Answer 1

Direct exposure - inhalation of toxic airborne products
Toxin-induced respiratory distress
Agents that produce pathological changes to pulmonary system - pulmonary target organ toxicology

Question 2

List exposure for pulmonary toxicology

Answer 2

Volatile compounds 
Suspended particles 
Inhalation
Direct acute or chronic effects 
Systemic toxicology

Question 3

Give agents causing pulmonary injury

Answer 3

SIMPLE ASPHYXIANTS

IRRITANTS

Question 4

What are simple asphyxiants?

Answer 4

nitrogen, noble gases, CO2 –> cause oxygen displacement, hypoxia and CNS symptoms

Recover on removal from source

Question 5

What are water soluble irritants?

Answer 5

Ammonia, chlorine, sulphur dioxide - upper respiratory symptoms, sense of burning, running nose, watery eyes –> lead to respiratory sensitisation (asthma like_

Question 6

What are water insoluble irritants?

Answer 6

Oxides of nitrogen, phosgene) - delayed onset, lower respiratory symptoms–> pulmonary oedema and fibrosis on healing

Question 7

What are direct airway injury examples?

Answer 7

Thermal/physical airway injury - heat, caustics, upper airway
Hydrocarbon aspiration - chocking, coughing dyspnea, hypoxia - low viscosity - acute lung injury, inflammatory, loss of surfactant

Question 8

How do methemoglobin (MetHb) inducers work? (inhibition of oxygen transport)

Answer 8

Methemoglobinaemia - state of oxidised haemoglobin in which haemoglobin iron is in the ferric state (unable to bind oxygen) - causes cyanosis

Question 9

Give examples of MetHb inducers

Answer 9

Benzocaine, dapsone, nitrates, aromatic amines, chlorates

Question 10

How would you investigate and manage MetHb inducers?

Answer 10

Simple bedside tests, lab, arterial blood gas

Manage - methylene blue, hyperbaric oxygen

Question 11

How does CO - carboxyhemoglobin (COHb) work as an inhibitor of oxygen transport

Answer 11

CO binds ~220x as tightly to Hb compared to oxygen
Or bind to Fe2+ in myoglobin and mitochondria, oxidative injury, lipid peroxidation, inflammatory cascade

leads to impaired tissue oxygen delivery and use, hypoxia, ischemic injury, cherry-red skin colour

Question 12

What tests would you use for CO?

Answer 12

Beside - arterial blood gas, COHb. lactate, PaO2 normal, ECG, urinalysis, labs, imaging

Question 13

What management would you use for CO?

Answer 13

Resus - cardiac monitoring, possible intubation. High flow O2, hyperbaric oxygen,, seek and treat cause (suicide, cyanide?)

Question 14

How does cyanide work as mitochondrial toxic agent?

Answer 14

Salts, alkaline, smells of bitter almonds,, similar mechanism to CO –> inhibits cytochrome oxidase enzyme - disrupts enzymatic processes

Causes lactic acidosis, vomiting, seizures, coma

Question 15

wHAT ARE THE SIGNS AND SYMPTOMS OF TOXICITY?

Answer 15

Anxiety, headache, confusion, tachycardia, seizures, hypoventilation, hypotension, dysrhythmias

Question 16

What antidotes can you use against cyanide?

Answer 16

sodium thiosulfate?

nitrites?

Question 17

How does paraquat work?

Answer 17

herbicide - toxic to skin and mucous membranes - mucosal exposure. once ingested migrates to the lungs bc of its oxygen seeking properties

Induces oxygen radical formation in all tissues but active uptake by pneumocytes from the circulation

If patients survive initial caustic ingestion - progressive pulmonary fibrosis with death can happen later

Redox cycling, oxidative stress, secondary inflammatory response causes multiorgan failure (lungs, heart, kidney)

Question 18

List the clinical features of paraquat

Answer 18

formulation, strength and dose are important
worse prognosis - kidney disease and above 50 yrs old
time of ingestion
painful mouth, difficulty in swallowing, nausea vomiting, abdominal pain, splitting nails, loss of nails, nosebleeds burning skin sensation- systemic poisoning

Question 19

What is the testing for paraquat?

Answer 19

General testing, FBC, kidney function - if prognosis is poor - palliative measures

Question 20

How would you manage paraquat?

Answer 20

GI decontamination (charcoal), hemoperfusion, antidotes, severe poisoning - palliative care

Question 21

List unique pulmonary toxic agents

Answer 21

Asbestos, silica, beryllium - combinations (fire smoke, smog)