WBR0949
| Author | [[PageAuthor::William J Gibson (Reviewed by Yazan Daaboul, M.D.)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biochemistry, MainCategory::Physiology |
| Sub Category | SubCategory::Pulmonology |
| Prompt | [[Prompt::A 22-year-old woman is brought to the emergency department (ED) after several members of her family witnessed her suffering a seizure. On the way to the hospital, she admitted to swallowing 50 aspirin pills in a suicide attempt. She is unconscious but responds to painful stimuli. In the ED, results from arterial blood gas on room air demonstrate the following: pH=7.32, pCO2=18 mmHg, pO2=111 mmHg, Bicarbonate=15 mEq/L. Blood samples are withdrawn, and electrolytes are as follows: Sodium=140 mEq/L, Chloride=100 mEq/L. Which of the following would have a similar effect on the oxygen-hemoglobin dissociation curve as this patient’s condition?]] |
| Answer A | AnswerA::Decrease in altitude |
| Answer A Explanation | AnswerAExp::A decrease in altitude would left-shift the oxygen-hemoglobin dissociation curve. |
| Answer B | AnswerB::Decrease in temperature |
| Answer B Explanation | AnswerBExp::A decrease in temperature would left-shift the oxygen-hemoglobin dissociation curve. |
| Answer C | AnswerC::Decrease in CO2 |
| Answer C Explanation | AnswerCExp::A decrease in CO2 would left-shift the oxygen-hemoglobin dissociation curve. |
| Answer D | AnswerD::Increase in 2,3-bisphosphoglycerate (2,3-BPG) |
| Answer D Explanation | AnswerDExp::An increase in 2,3-BPG would right-shift the oxygen-hemoglobin dissociation curve. |
| Answer E | AnswerE::Increase in carbon monoxide (CO) |
| Answer E Explanation | AnswerEExp::Because carbon monoxide (CO) has a 200x higher affinity for hemoglobin than does oxygen, an increase in CO would cause a non-competitive decrease in the oxygen binding capacity of hemoglobin. |
| Right Answer | RightAnswer::D |
| Explanation | [[Explanation::This patient has a high anion gap metabolic acidosis due to salicylate toxicity. The criteria for high anion gap metabolic acidosis is pH < 7.35 and an anion gap >16 (anion gap limit differs with age). The anion gap is defined by the following equation:
Educational Objective: The following factors result in a right shift of the oxygen-hemoglobin dissociation curve:
References: First Aid 2013 page 548]] |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Oxygen, WBRKeyword::Hemoglobin, WBRKeyword::Curve, WBRKeyword::Metabolic acidosis, WBRKeyword::Aspirin, WBRKeyword::Toxicity, WBRKeyword::Overdose, WBRKeyword::BPG, WBRKeyword::High anion gap |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |