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.
