A 39-year-old woman comes to the emergency department due to mild shortness of breath and right-sided pleuritic chest pain that began this morning. The patient underwent a mastectomy for left-sided breast cancer 2 weeks ago. She has a history of hives after eating seafood.
Blood pressure is 148/96 mm Hg, pulse is 114/min, and respirations are 21/min. Oxygen saturation is 91% on room air.
Chest x-ray is unremarkable and urine pregnancy test is negative. Creatinine is 0.8 mg/dL.
Which of the following is the most appropriate diagnostic approach?

Question

A 39-year-old woman comes to the emergency department due to mild shortness of breath and right-sided pleuritic chest pain that began this morning.  The patient underwent a mastectomy for left-sided breast cancer 2 weeks ago.  She has a history of hives after eating seafood.
Blood pressure is 148/96 mm Hg, pulse is 114/min, and respirations are 21/min.  Oxygen saturation is 91% on room air.
Chest x-ray is unremarkable and urine pregnancy test is negative.  Creatinine is 0.8 mg/dL.
Which of the following is the most appropriate diagnostic approach?

Quizplus · Accepted Answer

This patient's presentation with dyspnea, tachypnea, tachycardia, chest pain, and hypoxia, along with a history of breast cancer, is highly suggestive of acute pulmonary embolism (PE). CT pulmonary angiography (CTPA) using intravenous, usually iodinated radiocontrast, is the first-choice imaging test for diagnosing acute PE. The exact mechanism of radiocontrast-induced anaphylaxis is not known. However, the widely held notion that seafood allergy increases the risk of anaphylaxis to iodinated contrast has no basis in medical literature. Therefore, patients with seafood allergy can receive iodinated contrast and do not require pretreatment with glucocorticoids and antihistamines (Choice A). The converse is also true-patients who have had anaphylaxis due to iodinated contrast do not need to avoid seafood. (Choice B) High-osmolar radiocontrast is associated with increased rates of allergic reaction and contrast-induced nephropathy. Therefore, low- or iso-osmolar radiocontrast is used in most settings regardless of allergy history. (Choice D) Compression ultrasonography can diagnose deep venous thrombosis (DVT) and suggest the presence of PE. However, the absence of DVT does not rule out PE. CTPA is more diagnostically definitive and is the preferred study in patients without contraindication. (Choice E) Ventilation-perfusion scanning may be used in evaluation of PE in patients with a contraindication to CTPA (eg, renal insufficiency, true contrast allergy) or in those with an inconclusive CTPA. It is also the initial test of choice for pregnant patients with suspected PE and a normal chest x-ray. Educational objective: Seafood allergy does not confer any increased risk of anaphylaxis from iodinated contrast media and does not necessitate pretreatment with glucocorticoids and antihistamines. __________ References: 2014 ESC guidelines on the diagnosis and management of acute pulmonary embolism. (http://www.ncbi.nlm.nih.gov/pubmed/25173341) The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed. (http://www.ncbi.nlm.nih.gov/pubmed/20045605) Seafood allergy and radiocontrast media: are physicians propagating a myth? (http://www.ncbi.nlm.nih.gov/pubmed/18261505)

A 39-Year-Old Woman Comes to the Emergency Department Due to Mild