Carbon Monoxide poisoning in children - Toxicology

Introduction

Carbon monoxide is a colorless, odorless, and tasteless toxic gas, that can be produced from the combustion of any carbon-containing fuel.

CO is the most commonly involved gas in poisonous exposure in children.

It's a medical emergency and needs treatment right away.

Etiology - Common Sources involved in Pediatric CO poisoning

1. wood-burning stoves and fireplaces
2. Fires
3. Automobiles
4. kerosine generators
5. Old furnaces
6. Hot water heaters

Pathophysiology

The majority of effects of CO poisoning are due to systemic toxicity than local.

Carbon monoxide has a much higher affinity for Hb than oxygen. Gets rapidly attached to hemoglobin displacing oxygen molecule from its sites. You are talking about the affinity that is 210 times that of oxygen that of oxygen. [Yildiz, 2018]

The mechanisms involved are

1. Reduction in Oxygen carrying capacity and thus oxygen delivery

CO combines with Hemoglobin and reduces oxygen-carrying capacity and tissue hypoxia ensues afterward.

CO+Hb HbCO → tissue Hypoxia

2. Disruption of Cellular respiratory chain

Carbon monoxide combines with Cyt. Oxidase making it unavailable for respiratory chain cycle at cellular levels

3. Promoting Inflammation

Results in triggering inflammatory cascade at high-oxygen demand organs such as the heart, brain (AAP 2011)

4. Displacing NO

Clinical Features - What are the common symptoms of CO poisoning in children?

Symptoms of CO poisoning are variable and non-specific.

Children are specifically susceptible to CO poisoning due to relatively high metabolic and oxygen demands than adults.

Early-onset

Often the early mild symptoms can be easily confused with ‘flu-like’
illness and lead to the wrong diagnosis as a viral infection or Gastroenteritis especially if no specific history of exposure.

1. Headache
2. Nausea
3. Vomiting
4. Malaise
5. Weakness/clumsiness
6. Mental status changes like Confusion, irritability, and irrational behavior
7. Ataxia
8. Syncope
9. Tachycardia
10. Tachypnea

Moderate

1. seizure
2. acidosis
3. Cherry Red skin(very typical sign)

Severe

1. hypotension
2. cardiovascular collapse
3. Coma
4. Death

Acute exposure to very high CO levels will rapidly result in brain injury, cerebral edema, coma, and death without going through initial symptoms.

The normal level of carbon monoxide is 0.5%

Symptoms of Carbon monoxide exposure in children based on the extent of exposure

Diagnosis

Diagnosis is based on

History of exposure + Clinical findings + Confirmatory testing

Confirmatory testing

Even at significant carboxyhemoglobin levels, the patient can have normal oxygen saturation on pulse oxymeters. Therefore the confirmatory testing must include...

1. The levels of Carboxyhemoglobin should be obtained by Direct measurement of blood carboxyhemoglobin
2. Measurement of carboxyhemoglobin using a co-oximetry.

A CO-oximeter is a device that measures oxygen-carrying hemoglobin as well as the other non-normal hemoglobins such as carboxyhemoglobin and methemoglobin.

It is essential to rule out methemoglobinemia where history is not clear.

Blood Gas

1. Pa02 - Will essentially show normal PaO2 level.
2. Lactate - High lactate will support the findings of tissue hypoxia

Creatinine Kinase (Ck)

Ck is a useful indicator of Tissue Breakdown from hypoxia and Rhabdomyolysis

ECG

To rule out dysrhythmias

Imaging

1. CXR: To rule out pulmonary edema. Pulmonary edema due to CO poisoning is rare in children. Rather the pulmonary edema is caused due to LVF resulting from myocardail injury and secondory aspirations (more about aspiration syndromes) due to altered sensorium and loss of cough reflex.
2. CT/MRI brain: may conclude cerebral edema acutely and cerebral atrophy demyelination in later stages

Differentials - What are other exposure which can cause similar symptoms

The mild symptoms of CO poisoning can mimic exposure to

1. Indoor air pollutants
2. Allergens
3. Tobacco smoke
4. Volatile organic compounds

How to differentiate Exposure to CO for others

CO typically does not irritate the eyes and lungs, which is usually the case with other masqueraders.

Treatment

Acute Treatment

1. Move the child to a safe place with fresh air.
2. Try to eliminate the source of exposure.

Specific Treatment of CO poisoning in Children

Mainstay of Treatment

Oxygen therapy

How to administer oxygen?

100% oxygen through a non-rebreathing mask to achieve a highest possible concentration of alveolar oxygen concentration PAo2 in the beginning This can be later reduced to 60 to 90% as per the situation

Hyperbaric oxygen

Indication of Hyperbaric oxygen in CO poisoning

1. HbCO levels less than 25%
2. Abnormal cerebellar examination
3. Pregnancy
4. Syncope
5. Seizure
6. coma
7. acute coronary syndrome
8. altered mental status

What are the Outcomes/Sequelae of CO poisoning in children?

CO poisoning is a predictable cause of mortality and morbidity in post-disaster situations when widespread power cut occur CDC-MMWR 2012.

Persistent and delayed cognitive and cerebellar effects.

Further reading

Dive Deep If you would like to

• Carbon monoxide poisoning in children – own observations - Jackowska, T. et al. Carbon monoxide poisoning in children – own observations. (2013). Source - [Image 1 ]
• Practice Recommendations in the Diagnosis, Management, and Prevention of Carbon Monoxide Poisoning
• Hyperbaric oxygen for carbon monoxide poisoning - Life in the fast lane

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4. Lead Poisoning in Children
5. Cold injuries in children

( This article is reviewed pre-publication )

Author

Shama Sowdagar | DNB (Pediatrics)

Shama has completed residency from Kanchi kamakoti Child Trust Hospital, Chennai and works as a Pediatrician