The hypotension which follows release of the occluding aortic clamp has been noted by everyone doing surgery for abdominal aortic aneurysms. This hypotension may be only temporary or it may be sustained. Experimentally, at least, temporary hypotension occurs after release of aortic clamping of short duration, and sustained hypotension is expected only if the aorta has been occluded for an hour or more before declamping. Significant hypotension, whether temporary or sustained, is undesirable in any patient, but particularly so in those with degenerative arterial disease affecting the coronary, carotid, or cerebral arteries. Since the incidence of such disease is high in patients with aortic aneurysms1 the prevention of hypotension in these cases is obviously highly desirable.
Several factors probably contribute to hypotension developing after declamping the aorta. The sudden increase in the size of the vascular bed to be filled undoubtedly accounts for some decrease in arterial pressure, and
ENGLER HS, ELLISON LT, MORETZ WH, SIMPSON JG, GLEATON HE, FREEMAN RA. Shock Following Release of Aortic Cross-Clamping: Its Prevention by Shunt. Arch Surg. 1963;86(5):791–797. doi:10.1001/archsurg.1963.01310110101014
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