An 11-year-old girl is brought to the office for a health maintenance visit. She feels well and has no chronic medical conditions. As part of routine care, the patient receives a first dose of the quadrivalent meningococcal conjugate vaccine and the 9-valent human papillomavirus vaccine. Five minutes later, while being escorted to the waiting area, the patient appears pale and reports feeling dizzy. She immediately loses consciousness, but a fall is prevented by the health care provider. Blood pressure is 70/40 mm Hg and pulse is 46/min. On physical examination, the patient has normal lung and heart sounds. There is no rash. Which of the following is the most likely cause of this patient's syncope?

Question

An 11-year-old girl is brought to the office for a health maintenance visit.  She feels well and has no chronic medical conditions.  As part of routine care, the patient receives a first dose of the quadrivalent meningococcal conjugate vaccine and the 9-valent human papillomavirus vaccine.  Five minutes later, while being escorted to the waiting area, the patient appears pale and reports feeling dizzy.  She immediately loses consciousness, but a fall is prevented by the health care provider.  Blood pressure is 70/40 mm Hg and pulse is 46/min.  On physical examination, the patient has normal lung and heart sounds.  There is no rash.  Which of the following is the most likely cause of this patient's syncope?

Quizplus · Accepted Answer

11ec160b_37c0_8dbe_9249_f7c770b15796_MD0001_00 This patient most likely experienced vasovagal syncope, which involves a pain-induced or an emotional distress-induced cardioinhibitory and vasodepressor response. Vaccine administration is a known precipitant of vasovagal syncope, especially in adolescents. Because syncope-related falls can lead to serious injury (eg, skull fractures, intracranial hemorrhage), patients should be closely monitored for 15 minutes following vaccine administration. Patients with vasovagal syncope typically experience a prodrome (eg, pallor, nausea, diaphoresis) prior to losing consciousness. The mechanism is not well understood, but the trigger, in combination with a state of orthostatic stress (eg, upright posture, dehydration), is believed to signal the CNS to decrease sympathetic activity and increase parasympathetic tone, overriding the normal baroreceptor response. This leads to bradycardia, reduced LV contractility, and decreased peripheral vascular resistance, resulting in hypotension, decreased cerebral perfusion, and, ultimately, syncope. Symptoms rapidly resolve within 1-2 minutes. Postvaccination syncope can be confused with anaphylaxis, a rare but serious adverse effect resulting from IgE-mediated hypersensitivity to a vaccine component (eg, egg or yeast proteins). Anaphylaxis can develop rapidly following vaccination and may cause hypotension and syncope; however, affected patients typically experience urticaria or flushing rather than pallor, respiratory symptoms (eg, upper airway edema, bronchospasm), and reflex tachycardia rather than bradycardia (Choice C). (Choice A) Delayed-type reactions are due to the direct action of sensitized T cells when stimulated by contact with an antigen. They occur hours to days, rather than minutes, after exposure and typically present with a rash. (Choice B) An excessive cytokine response to the microbial components of a vaccine can result in a self-limiting local reaction (eg, redness or pain at the vaccination site) or, sometimes, systemic symptoms (eg, fever, malaise). (Choice E) The administration of a live attenuated vaccine (eg, measles, mumps, and rubella) to an immunocompromised host may cause uncontrolled replication and systemic invasion of the virus. Symptoms of an active infection would not manifest until >12-24 hours. Neither the meningococcal nor the HPV vaccine is live, and this patient is not immunocompromised. Educational objective: Vasovagal syncope is a known complication of vaccine administration, particularly in adolescents. It typically involves a prodrome and can be differentiated from anaphylaxis based on skin findings (pallor vs urticaria), absence of respiratory symptoms (eg, upper airway edema, bronchospasm), and presence of bradycardia (vs tachycardia). __________ References: Vaccine-associated hypersensitivity. (http://www.ncbi.nlm.nih.gov/pubmed/29413255) Syncope: epidemiology, etiology, and prognosis. (http://www.ncbi.nlm.nih.gov/pubmed/25538626)

An 11-Year-Old Girl Is Brought to the Office for a Health