Case Presentation:

Hypotension in the hospital setting is a common finding with a broad differential diagnosis.  The workup includes evaluation for cardiac and infectious etiologies, among others.  We present an infrequent cause of hypotension to demonstrate the importance of manually measuring blood pressure. 

A 62 year-old woman with impaired fasting glucose and hyperlipidemia was admitted to the neurology service for intermittent leg weakness, numbness, and blurry vision for six months. Her admission vital signs were remarkable only for hypotension with a blood pressure of 74/55.  The initial physical exam revealed carotid bruits with otherwise unremarkable neurological, cardiac, and pulmonary examinations.  Her orthostatic hypotension improved after two liters of normal saline.  On hospital day two, our medicine team was consulted for recurring symptomatic hypotension.

Laboratory studies revealed a normocytic anemia, no electrolyte abnormalities, elevated TSH, negative troponins, and an unremarkable EKG. Her dysuria and urinalysis results suggested a urinary tract infection; she received three days of antibiotics. A transthoracic echocardiogram revealed a normal left ventricular ejection fraction with preserved diastolic function.  Head imaging via CT and MRI showed evidence of remote infarcts. A cervical spine MRI showed C5-6 disc protrusion, concerning for spinal canal stenosis and autonomic dysfunction causing hypotension.  Surgical intervention was planned. Upon further chart review, patient was noted to have extremity-dependent fluctuating blood pressures. Manual blood pressure measurement on both arms revealed discordant blood pressures.  Thus a CT angiography was performed to rule out aortic dissection, but surprisingly showed signs of bilateral subclavian steal syndrome. The vascular surgery team performed carotid-subclavian bypass with post-operative resolution of her hypotension.  

Discussion: Hospitalized patients commonly experience hypotension; the broad differential includes sepsis, cardiac arrhythmias, acute coronary syndrome, pneumothorax, and hypovolemia. While the mainstay treatment includes volume replacement and vasopressors to maintain adequate perfusion to vital organs, one should promptly consider the differential diagnosis while ruling out and treating infectious etiologies, investigating cardiac function, and evaluating for life-threatening causes. 

Conclusions: Bilateral subclavian steal syndrome refers to the phenomenon of blood flow reversal in vertebral arteries due to subclavian artery stenosis and manifests as cerebrovascular ischemia with neurological symptoms or arm ischemia, among other presentations. While this case shows an uncommon cause of hypotension, it more importantly emphasizes the importance of bilateral manual blood pressure measurement during evaluation.