Haemodynamics during partial extracorporeal circulation in the dog.

Circulatory changes were studied in 9 mongrel dogs during partial extracorporeal circulation from the right atrium to the carotid and/or femoral artery. The bypass circuit consisted of a membrane oxygenator and a roller pump. Cardiac output and arterial pressure decreased during bypass, but changed little when extracorporeal flow (EF) was increased from 1/10 to 3/4 of control cardiac output. Right atrial and pulmonary wedge pressures were lower than control. Total blood flow was equal to control when EF was 1/2 of the control cardiac output, and exceeded control flow at 3/4. Such enhanced venous return presumably resulted from sympathetic stimulation via atrial mechanoreceptors.