You are working in a busy ED when a patient who is 54 arrives with an acute onset headache associated with syncope but no focal neurologic deficits.  His physical exam is unremarkable but his BP is mildly elevated at 175/80. The patient’s head CT is consistent with an aneurysmal subarachnoid hemorrhage.  You begin anti-hypertensive treatment, but wonder how reliable non-invasive blood pressure measurement is in this patient.

Non-invasive blood pressure (NIBP) monitoring with an automated BP cuff is ubiquitous.  But how closely does the NIBP measurement correlate with the intra-arterial blood pressure (IABP)?  What patient factors might predict a clinically relevant discordance? A recent retrospective study from the University of Maryland explored this question.  They reviewed charts of patients admitted with hypertensive emergencies (most were neurologic, aortic, eclamptic, and cardiac) where the systolic blood pressure was required to be maintained in a tight range.  A clinically relevant difference in BP measurement was defined as >10mmHg between the NIBP and IABP as well as requiring a change in management based on guidelines relevant to each.

68% of patients had a difference >10mmHg and 28% of patients would have required a change in management based on the difference.  Spontaneous intracranial hemorrhage was the leading diagnosis associated with a clinically relevant discordance (OR 13.5, 2.3-79.5).  In view of these results the investigators concluded that clinicians should have a low threshold for intra-arterial blood pressure monitoring when tight BP control is required.

While this is a retrospective study, it does lend credence to the practice of using IABP monitoring liberally for patients whose disease processes require tight BP control for optimal management.

Reference:

Raffman A, Shah U, Barr JF, et al. Predictors of clinically relevant differences between noninvasive versus arterial blood pressure. Am J Emerg Med. February 2020. doi:10.1016/j.ajem.2020.02.044.