ACE 20A Sample Question
A patient presenting for lower extremity vascular surgery has a blood pressure of 180/90 mm Hg in the right arm and 130/70 mm Hg in the left arm by automated cuff measurement. Which of the following locations would be MOST appropriate for placement of an artery catheter for invasive blood pressure measurement?
A. The right arm ✔
B. The left arm X
C. A central location (eg, axillary or femoral) X
Read the discussion below.
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Older patients with significant atherosclerotic disease may present with an asymptomatic—and previously unrecognized—discrepancy in blood pressure between the right and left arms. This arises from partial or complete obstruction of the proximal arterial tree, with limb perfusion preserved through the development of collateral channels. A difference exceeding 20 mm Hg in systolic pressure between limbs is considered clinically significant.
When invasive arterial pressure monitoring is indicated, the arm with higher pressure is the more appropriate site for catheter placement because it will better reflect pressures in the central circulation. Ancillary technologies based on the arterial pressure waveform, such as calculation of stroke volume variance, will also be more accurate if the arm with higher pressure is used.
Placement of an arterial catheter in a more central location—axillary or femoral—would yield even more reliable results than radial placement in the arm with higher pressure. However, the increased risk of thrombosis and infection and the increased logistical challenge of placement and maintenance of a central arterial catheter will mostly likely not justify the minor gain in accuracy unless the measured pressure in the higher arm is already known to be inaccurate.
It may be pertinent to consider the differential diagnosis and review any available patient imaging, such as angiograms. Besides atherosclerosis, other potential causes of blood pressure discrepancy between the arms include subclavian artery stenosis, Takayasu arteritis, aortic dissection, aortic coarctation, and compression in the thoracic outlet.
- Gropper MA, Cohen NH, Eriksson LI, Fleisher LA, Leslie K, Wiener-Kronish JP, eds. Miller’s Anesthesia. 9th ed. Elsevier; 2020:1164.
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