ENVELOP B 7 CREDITS 10 MARKS Flashcards
(2 cards)
envelop B
1
A 32-year-old man presents to the emergency department with complaints of shortness of breath, fatigue, and a bluish tint to his lips and fingers that has been gradually worsening over the last 24 hours. He reports a recent history of using a topical numbing agent containing benzocaine to treat a sore throat. He denies any significant medical history and is not on any chronic medications. On examination, he appears cyanotic, and his oxygen saturation on pulse oximetry reads 85%, despite being given supplemental oxygen. His arterial blood gas (ABG) shows a normal PaO2 but a decreased oxygen saturation. A co-oximeter reveals a methemoglobin level of 18%.
Question 1: What is the most likely diagnosis in this patient?
Question 2: What is the pathophysiology behind methemoglobinemia?
Question 3: How would you manage this patient’s condition?
ANS:
Q1: methemoglobinemia, which is suggested by the patient’s cyanosis, hypoxia despite normal PaO2, and abnormal pulse oximeter readings. benzocaine is a known cause of methemoglobinemia,
Q2: hemoglobin is oxidized to methemoglobin (MetHb), which cannot carry oxygen effectively. Normally, hemoglobin is in the ferrous (Fe2+) state, but in methemoglobinemia, it is in the ferric (Fe3+) state, which impairs oxygen binding and release.
Q3: Discontinuing the offending agent
Administering 100% oxygen
Methylene blue
if methylene blue is not effective or contraindicated (e.g., in patients with G6PD deficiency), exchange transfusion or other supportive measures may be necessary.
2
A 45-year-old woman presents to the emergency department with complaints of dizziness, confusion, and fatigue. Her husband mentions that she has been feeling unwell for the last two days, with progressively worsening symptoms. She has a history of using an over-the-counter teething gel containing benzocaine for her sore gums. Upon examination, the patient appears mildly cyanotic, and her oxygen saturation is 87% on room air. The initial ABG shows a normal PaO2, and a co-oximeter reveals a methemoglobin level of 22%.
Questions:
Q1: What clinical findings would raise suspicion for methemoglobinemia in this patient?
Q2: What is the role of co-oximetry in the diagnosis of methemoglobinemia?
Q1
Cyanosis that is not relieved by oxygen therapy.
Normal PaO2 with low oxygen saturation on pulse oximetry.
Use of a benzocaine-containing product
hypoxic symptoms
Q2
measures the levels of methemoglobin (MetHb) in the blood, which pulse oximetry cannot differentiate from oxygenated hemoglobin. Co-oximetry provides a more accurate measurement of oxygen saturation and helps confirm the diagnosis.
