Carbon monoxide- toxicology. Characteristics. Medical Activities
Written by Anam Hussain
General characteristics
- Is a blood poison
- colourless, odourless and tasteless gas
- Slightly lighter than air
- No solubility in water
- Flammable
- Oxidises to CO2
- Penetrates easily trough materials
- Able to travel long distances
- Compounds in air at normal temperature, are combustible
- One of those most toxic compounds
- CO is 4th on the list for cause of most intoxications after alcohol, drugs and narcotics
Source of exposure: Inhalation only
Pathophysiology:
- Target: blood
- When inhaled, penetrates the alveolar capillary membrane to enter blood circulation
- Enters erythrocytes and binds Fe2+ of haemoglobin to form carboxyhaemoglobin
- This prevents oxygen extraction by alveoli causing hypoxemia which leads to hypoxia of vital organs: heart, brain, liver
- CO also reacts with Fe2+ in cytochrome oxidase and cytochrome p40.
- This blocks oxidative phosphorylation in mitochondria
Clinical symptoms
Syndromes caused by CO poisoning:
- Nervous/psychotic
- Cerebral
- Cardiovascular
- Tiredness and weakness
- Hyperpyrexia
- Changes in consciousness and pupil reactions
Depending on concentration of Carboxyhaemoglobin in body, 4 levels are distinguished
- Light= 20-30% COHb
- Moderate= 30-40% COHb
- Heavy= >50% COHb
- Instant death occurs with levels of 60-70% COHb
- Light level intoxication symptoms
- No disturbance in CNS activity, acceptable general status
- Extreme pulsing headache
- Sight disturbances
- Nausea, vomiting, weakness in joints and muscle pain
- Pink colour of skin and mucosa, Hyperthermia
- Symptoms of increased time and exposure:
- Development of nervous and psychotic symptoms-euphoria, memory loss, disorientation
- Tachycardia, tachypnoea
- Symptoms with heavy level of intoxication:
- Coma from toxic brain damage from hours to days
- Cerebral syndrome peculiarities
- Mydriasis till no pupil reaction
- Apnoea
- Arrhythmia due to metabolic acidosis
Medical Activities
- FA in case of CO pollution and intoxication requires search and rescue teams to wear autonomous respirator or common gas mask with hopcalith bullet
- When casualty shows signs of intoxication- contact with CO has to be interrupted with barrier application: masks etc.
- Primary triage is performed followed by organised evacuation to FMS that is located outside of CAOD.
- First pre-physician Aid:
- Starts with assisting those with impeded breathing
- Oxygen therapy using 100% oxygen via mask. This is started and continued throughout medical evacuation procedure
- Hospital treatment:
- Oxygen therapy continues until COHB levels decrease to 10%
- Casualties undergo hyperbaric therapy in hyperbaric chambers to increase speed and efficiency of treatment
- Hyperbaric therapy 100% recommended for intense intoxication and nerve damages
- Administration of Antidotes including: vitapiracen, orocetam and pyramem given to treat intracellular hypoxia, for brain recovery.