Infrarenal aortic clamp hypertension is exacerbated by baroreceptor blockade.
Aortic clamp-induced hypertension has long been implicated in the cardiovascular mortality and morbidity following infrarenal aortic operations. We studied the physiologic mechanisms leading to clamp-induced hypertension. Mean arterial pressure (MAP), cardiac output, heart rate, and left ventricular pressure were measured in alpha-chloralose-anesthetized dogs. Animals received alpha, beta, both alpha and beta, or no adrenergic blockade (n = 3, 4, 12 and 7, respectively). The infrarenal aorta was clamped following ligation of the infrarenal collateral vessels (lumbar, circumflex iliac, and tail arteries). Statistical analysis used paired t tests within groups, and ANOVA and unpaired t tests between groups, with Bonferroni's correction as indicated. Following placement of the clamp, MAP increased immediately in all groups, with magnitude of the increase related to the extent of adrenergic blockade. MAP increased 5.6 +/- 0.8 mm Hg with no blockade (P = 0.0005), 6.7 +/- 0.8 mm Hg with alpha blockade (P = 0.0153), 15 +/- 3.1 mm Hg with beta blockade (P = 0.0163), and 16.7 +/- 1.3 mm Hg with combined alpha and beta blockade (P < 0.0001). The increase in MAP immediately following infrarenal aortic clamping was most pronounced with combined alpha and beta blockade. We suggest that acute intraoperative hypertension associated with infrarenal aortic clamping is caused by the attenuation of compensatory baroreceptor reflex mechanisms.
Giglia
J S
JS
Department of Surgery, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA.
Zelenock
G B
GB
D'Alecy
L G
LG
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001012:Aorta, Abdominal / Q000601:surgery*; D001794:Blood Pressure / Q000187:drug effects; D004285:Dogs; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology; D006978:Hypertension, Renovascular / Q000209:etiology* / Q000601:surgery; D008297:Male; D011311:Pressoreceptors / Q000187:drug effects* / Q000601:surgery; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology; D013525:Surgical Instruments / Q000009:adverse effects*
D000319:Adrenergic beta-Antagonists