Angiotensin and alpha-adrenoceptor activation play a role in hemodynamic response to aortic cross-clamping.
This study was designed to identify the possible role of vasoconstricting compounds released from ischemic tissues in the hemodynamic response to cross-clamping of the thoracic aorta. Twenty-one dogs were anesthetized with pentobarbital sodium. The left hindlimb was denervated, vascularly isolated, and pump perfused at a constant rate with blood drained from the inferior vena cava after passing through a gas-exchanging membrane where oxygen and carbon dioxide tensions were maintained within normal limits. Left and right thoracotomies were performed, and the aorta and inferior vena cava were cross-clamped. The cross-clamping was associated with 33-45% increase in limb vascular resistance in denervated control animals (n = 6). In animals pretreated with Enalaprilat (2 mg/kg, n = 6), an angiotensin-converting enzyme inhibitor, limb vascular resistance did not change significantly. In animals pretreated with phenoxybenzamine (3 mg/kg, n = 6), an alpha-adrenoceptor antagonist, limb vascular resistance significantly decreased to 43% of preclamped level. The study demonstrated that vasoconstrictive compounds, such as angiotensin and catecholamines, play a role in systemic hemodynamic changes, including arterial hypertension, observed during cross-clamping of the thoracic aorta.
Gelman
S
S
Department of Anesthesiology, University of Alabama, Birmingham 35233.
Bredle
D L
DL
Bradley
W E
WE
Cain
S M
SM
D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology*; D002395:Catecholamines / Q000502:physiology; D004285:Dogs; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology*; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology; D010100:Oxygen / Q000378:metabolism / Q000493:pharmacokinetics; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D002395:Catecholamines; D011942:Receptors, Adrenergic, alpha; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D010100:Oxygen