WBR0196

Author	PageAuthor::Vendhan Ramanujam
Exam Type	ExamType::USMLE Step 3
Main Category	MainCategory::Community Medical Health Center, MainCategory::Primary Care Office, MainCategory::Emergency Room
Sub Category	SubCategory::Psychiatry, SubCategory::Respiratory, SubCategory::Electrolytes
Prompt	[[Prompt::A 26 year old women comes to ER with complaints of nausea, sweating, dizziness and palpitations. She appears anxious, tremulous and breathes rapidly. She used to be previously in good health. These symptoms appeared suddenly before 30 minutes on her arrival to the ER. Her blood pressure is 110/70 mm Hg, pulse rate 110/minute and temperature is 36.6 C. Acute coronary syndrome and pulmonary embolism have been ruled out. While waiting for the physician, she also began complaining about numbness and a tingling sensation around her mouth and in her fingertips. The most appropriate next step by the physician will be]]
Answer A	AnswerA::Order an immediate intravenous bolus infusion of 50 ml of D50W solution
Answer A Explanation	[[AnswerAExp::Incorrect-D50W bolus infusion will not be useful since this patient is not suffering from hypoglycemia.]]
Answer B	AnswerB::Draw a blood sample for plasma catecholamine and metanephrine levels
Answer B Explanation	[[AnswerBExp::Incorrect-Although she continues to remain anxious, sweating, tremulous and palpitating, her blood pressure is normal. So plasma catecholamine and metanephrine levels for diagnosing pheochromocytoma will not be the next step in the level of management.]]
Answer C	AnswerC::Draw a blood sample for serum free T3, T4 and TSH levels
Answer C Explanation	[[AnswerCExp::Incorrect-Before proceeding with further tests to rule out other possible causes like thyrotoxicosis, it is necessary to attend to the patients complaints of respiratory alkalosis and hypocalcemia first.]]
Answer D	AnswerD::Ask the patient to breathe into a paper bag
Answer D Explanation	[[AnswerDExp::Correct-The symptoms experienced by this patient are classical of hyperventilation and is probably due to a panic attack, which is a common cause of hyperventilation. Hyperventilation leads to respiratory alkalosis with a fall in blood CO2 levels. Fall in blood CO2 causes constriction of cerebral blood vessels. This leads to dizziness and a sense of derealization following cerebral hypoxia. Ionized calcium usually competes with hydrogen ions for the same negatively charged binding sites on albumin and other calcium-binding proteins. This binding is pH dependent and alters the level of ionized calcium in the blood. An increase in pH in alkalosis promotes increased protein binding, which decreases the ionized fraction of serum calcium levels. Low ionized calcium levels lead to signs of perioral tingling and paresthesia. Signs of tetany, which is painful muscle spasm, will follow if the serum calcium levels are too low. Especially after ruling out life threatening causes like acute coronary syndrome and pulmonary embolism, breathing into a paper bag reverses the symptoms by recycling the inspired air with a higher concentration of CO2 than the normal inspired atmospheric air.]]
Answer E	AnswerE::Draw a blood sample to evaluate blood alcohol concentration
Answer E Explanation	[[AnswerEExp::Incorrect-Alcohol intoxication presents with confusion, altered level of consciousness, seizures and respiratory depression. Only in such a case a blood sample will be required to evaluate the patients blood alcohol concentration.]]
Right Answer	RightAnswer::D
Explanation	[[Explanation::The symptoms experienced by this patient are classical of hyperventilation. It is commonly seen in panic attacks and other anxiety disorders. Hyperventilation leads to respiratory alkalosis with a fall in blood CO2 levels. Fall in blood CO2 causes constriction of cerebral blood vessels. This leads to dizziness and a sense of derealization following cerebral hypoxia. Ionized calcium usually competes with hydrogen ions for the same negatively charged binding sites on albumin and other calcium-binding proteins. This binding is pH dependent and alters the level of ionized calcium in the blood. An increase in pH in alkalosis promotes increased protein binding, which decreases the ionized fraction of serum calcium levels. Low ionized calcium levels lead to signs of perioral tingling and paresthesia. Signs of tetany, which is painful muscle spasm, will follow if the serum calcium levels are too low. Breathing into a paper bag reverses the symptoms by recycling the inspired air with a higher concentration of CO2 than the normal inspired atmospheric air. Educational objective: During panic attacks, patients who hyperventilate classically present with symptoms and signs of cerebral hypoxia and hypocalcemia following a fall in blood CO2 and increase in blood pH due to respiratory alkalosis. The approach after ruling out life threatening causes like acute coronary syndrome and pulmonary embolism in these patients will be to ask them to breathe into a paper bag that reverses the symptoms by recycling the inspired air with a higher concentration of CO2 than the normal inspired atmospheric air. This will improve the patients symptoms. Educational Objective: References: ]]
Approved	Approved::Yes
Keyword
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::