Excessive increase in circulating catecholamines during cross-clamping of the descending thoracic aorta in pigs

Abstract

The purpose of this study was to determine the plasma catecholamine response to cross-clamping of the descending thoracic aorta in pigs and to relate the plasma catecholamine response to cardiac output during cross-clamping. This prospective, controlled animal study was done at the University Hospital of Trondheim, Norway. Eight pigs (19–25 kg) underwent cross-clamping of the descending thoracic aorta for 30 minutes. The time course of plasma adrenaline, plasma noradrenaline, and ascending aortic blood flow were measured. It was found that the increase of plasma catecholamines during cross-clamping of the descending thoracic aorta in pigs was parallel to the increase of aortic blood flow during cross-clamping. Plasma adrenaline increased from 0.22 nmol/L to a maximum of 11.75 nmol/L and plasma noradrenaline increased from 0.17 nmol/L to a maximum of 46.92 nmol/L after 10 minutes of cross-clamping (p = 0.01). Ascending aortic blood flow increased from 2.6 L/minute to a maximum of 4.7 L/minute after 10 minutes of cross-clamping (p = 0.01). Our findings support the theory that increased plasma catecholamines might be a mechanism of increased cardiac output during cross-clamping of the descending thoracic aorta. The increase of plasma catecholamines during cross-clamping is most likely due to distal hypotension with increased sympathetic activity.