T'he brains of dogs subjected to total cardiac bypass were examined for early signs of ischaemic nerve cell changes. Diffuse nerve cell changes were found immediately following two-and threehour non-pulsatile perfusions but not following pulsatile perfusions of the same durations. The nerve cell changes found in the brains were acute cell swelling and early isohaemic cell change. Acute cell swelling was found only in the cerebellar Purkinje cells. Ischaemic cell change was found in several regions of the brain but the cerebral cortex and cerebellar Purkinje cells were most frequently affected. Diffuse nerve cell changes are attributed to non-pulsatile blood flow but some complicating factors are recognized.Focal lesions found in three brains may have been due to embolism by blood cell aggregates and/or gas microbubbles.Roller pumps are currently in general use for the production of extracorporeal circulation during open-heart surgery. Their remarkable efficiency and easy control have been a hindrance to the development of alternative types of pump. However, an increasing volume of evidence supports the view that pumps producing pulsatile blood -flow would provide more efficient tissue perfusion than roller pumps producing ripple (non-pulsatile) blood flow. We have performed experiments to test this view using brain damage as a criterion for assessing tissue perfusion.
MATERIALS AND METHODSGeneral anaesthesia was induced in 20 beagle and harrier dogs, 6-5-20-0 kg body weight, by intravenous injection of 0 25-0 5 g of sodium thiopentone (Intraval (DeBakey, 1934) or the MortonKeele prototype pulsatile pump (Sanderson et al.) with Harvard remote diaphragm heads. The circuit tubing was 6-0 mm internal 'diameter polyvinyl chloride (PVC). The reservoirs were also PVC and each reservoir had a capacity of 300 ml. The heat exchanger consisted of four stainless steel tubes each 15 m in length and with an internal diameter of 6-0 mm mounted in a copper water jacket. The heat exchanger was placed in the left atrial return instead of being in the delivery line from the left pump. This translocation was introduced to reduce damping of the pulse delivered by the pulsatile pump.All of the cannulae were made of stainless steel.The atria were drained through 6&0 mm internal diameter fenestrated cannulae. The internal diameters of the arterial cannulae were 4-0 or 5-0 mm for the pulmonary artery, 2 5, 3 0 or 3-5 mm for the femoral artery, and 4 0, 5 0 or 6-0 mm for the proximal aorta, depending upon the diameter of the lumen of the artery.The extracorporeal circuit was primed with 1,300 ml dog blood; 10 ml 10% low molecular weight dextran in 0-9% sodium chloride (Rheomacrodex) and 4 ml 10% mannitol/kg of body weight; plus 4 ml 20% sodium bicarbonate, 2,500 international units heparin, and 3 ml 20% calcium chloride/ 500 ml priming fluid.Using clean surgical techniques, a median sternotomy was performed to permit cannulation of the right and left atria and the pulmonary artery. For non-pulsatile flow, the aorta was retrogradely per...
