SAQ 253 – Toxicology – carbon monoxide poisoning and hyperbaric oxygen

Question 6. carbon monoxide poisoning and hyperbaric oxygen.

a. Clinical features

• Headache.
• Nausea or vomiting.
• Dyspnoea.
• Angina.
• Weakness.
• Confusion or altered higher mental function.
• Visual disturbance.
• Tachycardia or arrhythmia.
• Seizure.
• Coma or death.

b. Hyperbaric oxygen indications

• Carboxyhaemoglobin above 20%, or above 15% in pregnancy, children, or older patients.
• Altered mental state not otherwise explained.
• Unexplained metabolic acidosis with base excess below -2.
• ECG evidence of myocardial toxicity.
• Treatment can commence within six hours of exposure.

c. Alfred study finding

• Hyperbaric oxygen did not reduce cognitive deficit or improve neuropsychological performance and may have caused harm.

d. Alfred study criticisms

• Specific neuropsychological assessment techniques used.
• Approximately 50% lost to follow-up.
• Study group was severely poisoned with unusually high neurological toxicity.
• Practical limitations of continuous 100% oxygen for 48 hours.

e. Salt Lake City study finding

• Hyperbaric oxygen produced a strong significant reduction in cognitive complications compared with normobaric oxygen.

f. Salt Lake City study criticisms

• Groups were unmatched at entry.
• Only about one-third were suicide attempts.
• Many patients had prolonged carbon-monoxide exposure.
• Patient population differed from Australian emergency-department patients.