Acute Carbon Monoxide Poisoning

Objectives
Diagnosis
Criteria for HBO therapy
Work-up considerations
Treatment
Suggested treatment threshold
ICD 10 codes
Level of evidence

Objectives

Accelerate the dissociation of CO from hemoglobin and intracellular/ intra-mitochondrial haemes, and enhance the elimination thereof from plasma and other tissue. Maintain adequate tissue oxygenation. Reduce intracranial pressure and cerebral oedema. Antagonise brain lipid peroxidation. Enhance mitochondrial oxidative processes. Avert leukocyte adhesion.

Diagnosis

History of acute exposure to exogenous or endogenous carbon monoxide (e.g. catabolism of methylene chloride), resulting in symptoms. Symptoms suggestive of CO poisoning following closed space operation of internal combustion engines. Elevated carboxyhemoglobin levels.

Criteria for HBO therapy

Carboxyhemoglobin (COHb) level > 5% (note that higher levels are found in smokers), and/or history of loss of consciousness, pregnancy, neurological or ischemic presentation +/- abnormal psychometric evaluation after a suspected CO exposure. Failure to respond to normobaric 100% oxygen in 3-4 hours or in cases of severe CO-related and concomitant cyanide poisoning.

Work-up considerations

1. Patient needs to be referred from or discussed with medical specialist.
2. Comprehensive medical history & physical examination including baseline psychometric test where possible.
3. Administer 100% oxygen via non-rebreather reservoir mask during work up.
4. ABG: COHb & Lactate.
5. Exhaled CO monitoring.
6. Serum glucose/ HGT.
7. Pregnancy test in females of child bearing age.
8. ECG.
9. Troponin if COHb > 40% or ischemic ECG changes, or COHb >25% in known ischaemic heart disease.
10. CXR in suspected inhalation injury.
11. Drug screen if suspected suicide attempt.
12. Optimal stabilisation & maintenance of medical treatment i.e. IVI fluids, urinary catheter, intubation, etc. Consider Cyanide poisoning and manage accordingly where smoke inhalation associated with closed space fires, involving synthetic materials, occurred.
13. Consider emergency myringotomies. 
14. Signed informed consent for HBOT.

Treatment

1. HBO at 2.5 - 3.0 ATA for 90 minutes with two 5 – 10 minute air breaks. If symptoms persist or post-treatment psychometric testing remains abnormal provide additional treatments at 2.0 – 2.4 ATA for 90 minutes.
2. Treatment schedule: First treatment ASAP, then q6-12hrly
3. Continue medical supportive care as necessary. Monitor ECG. Intravenous fluid therapy, as indicated
4. Repeat neuropsychometric screening following each treatment where possible

Suggested treatment threshold

1 – 5 treatments

ICD 10 codes

T58 - Toxic effect of Carbon Monoxide

Level of evidence

Level A