Background

An acute aortic dissection (AAD) can be a life-threatening emergency which frequently requires rapid and precise control of the patient’s heart rate and blood pressure. The 2010 guidelines for management of patients with thoracic aortic disease suggest a heart rate goal of <60 bpm and a systolic blood pressure between 100-120 mmHg. In order to achieve this, a rapid-acting beta-blocker (i.e., esmolol) may be used in combination with an IV calcium channel blocker (i.e., nicardipine or clevidipine). These medications need to be monitored closely to avoid overshooting these goals and causing hemodynamic compromise. Ideally, an arterial line would be used to monitor the patient’s blood pressure, however this may not always be feasible so a traditional, noninvasive blood pressure cuff can be used. This may be complicated if the patient has the classic, but not universal, finding of unequal systolic blood pressure values between their left and right extremities. This raises the question, in a patient with an AAD and disparate blood pressures in each arm, which arm reading should be used for monitoring?

Evidence

A 2018 study from Um et al. evaluated 111 patients with an AAD and compared them with 111 control patients. This study found that while a systolic blood pressure difference of >20 mmHg between sides was a positive predictor for an AAD, the presence of a pulse deficit had a higher diagnostic accuracy. For the purpose of this study, a pulse deficit was defined as “any recorded difference in volume/force or difference in obvious signs of malperfusion”. The cause of an unequal blood pressure or pulse deficit in the upper extremities in this population is typically due to dissection of the brachiocephalic or subclavian arteries. In order to properly achieve the desired blood pressure reduction in patients with divergent blood pressure values, the higher value should be used for titration of antihypertensives. This is due to the occurrence of pseudohypotension occurring in the limb with the dissected artery.

Bottom-line

  • Aggressive and precise heart rate and blood pressure control are critical for patients with an acute aortic dissection
  • The presence of a pulse deficit may provide better diagnostic accuracy than a difference in systolic blood pressure
  • When titrating blood pressure medications in patients with unequal blood pressure readings between extremities, the higher value should be utilized

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References:

  1. Hiratzka LF, Bakris GL, Beckman JA, et al. 2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM guidelines for the diagnosis and management of patients with thoracic aortic disease Circulation. 2010;121(13):e266-369. doi: 10.1161/CIR.0b013e3181d4739e. PMID: 20233780.
  2. Um SW, Ohle R, Perry JJ. Bilateral blood pressure differential as a clinical marker for acute aortic dissection in the emergency department. Emerg Med J. 2018;35(9):556-558. doi: 10.1136/emermed-2018-207499. PMID: 30021832.
Mike O'Brien, PharmD

Mike O'Brien, PharmD

ALiEM Series Editor, EM Pharm Pearls
EM Clinical Pharmacy Specialist
Massachusetts General Hospital
Mike O'Brien, PharmD

@MikeEMPharmD

Digital Engagement MSL at Novartis | Thoughts & views are my own
Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP

Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP

Leadership Team, ALiEM
Creator and Lead Editor, Capsules and EM Pharm Pearls Series
Attending Pharmacist, EM and Toxicology, MGH
Associate Professor of EM, Division of Medical Toxicology, Harvard Medical School
Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP

@PharmERToxGuy

EM Pharmacist & Toxicologist @MassGeneralEM | Asst Prof @HarvardMed/@EMRES_MGHBWH | @ALiEMteam leadership | Capsules creator, ALiEMU | President, ABAT | #FOAMed