Question 1
35 years old female is brough to the ER on new year's night with complaints of severe headache and confusion. In the ER, the patient appears to be confused, and irritable. Her vital signs are normal, except for oxygen stauration of 88 %, and ABG shows hypoxia with normal PO2. Her CBC is normal, Blood sugar level is normal. The accompanying friends also had headache but was not severe enough as the patient. What is the phathophysiology of the complaints?
A) Alcohol induced hypoxia
B) Meningeal irritation
C) Cytochrome oxidase inhibition
D) Panic Attacks
E) Oxidized heme groups
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1 comments:
Answer) C: Cytochrome Oxidase Inhibition.
CO poisoning should be suspected in this scenario. The hints to look out for is New years night (Cold Climatic conditions when we use room heaters) and friends who also had similar but milder symptoms.
CO poisoning is usually caused by Room Heaters, smoke inhalation, automobile exhaust. CO competes with O2 for binding on Hb (CO has 210 times more affinity to bind Hb than O2). It inhibits cytochrome oxidase in the oxidative phosphorylation pathway (ETC), thus causing a left shift of O2 binding curve.
Typically the patient presents with low SaO2 and a normal PaO2 and Hb. Cherry red discoloration of skin/blood may be presented. Headaches is the most common and initial symptom, that may progress to confusion and coma. CO causes necrosis of Globus Pallidus in the brain.
Points to note:
CO poisoning with Low SaO2 and Normal PaO2.
Treat it with 100 % Oxygen
CO and Cyanide inhibits cytochrome oxidase.
Other Options:
A) Alcohol is an uncoupling agent and a mitochondrial toxin which will present with Hyperthermia and hypoxia.
B) Meningeal irritation is seen in meningitis, which will present with fever and neck stiffness.
D) Panic Attacks can present with headache, but more likely it presents with palpitations and sweating. Physical Examination/SaO2/Vitals are normal. There may be hypocapnia due to hyperventilation.
E) Oxidized heme group (Fe+3) is seen in Methemeoglobinemia. Look out for someone on sulfa (Diuretics/dapsone) or nitrates or someone who drank water form streams in the Rocky Mountains. Typically, these cases also present with Normal PaO2, and Low SaO2, but scenario described would be different than CO poisoning. Patients have chocolate colored blood and cyanosis. Treat these cases with Methylene Blue and Vitamin C.
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