Cerebral lesions due to emboli of silicone anti‐foam in dogs subjected to cardio‐pulmonary bypass

Abstract

PLATES I1 AND 111) EARLY in 1957 work was started in the Department of Surgery of the University of Birmingham on a method of total cardiopulmonary bypass for eventual use on patients needing open cardiac surgery. It was decided to use the Lillehei-DeWall system, already employed successfullyin theunited States, in which oxygen is bubbled through a vertical column of blood (" bubble oxygenation ") (Lillehei et al., 1957). The reasons for selecting this particular apparatus for use in Birmingham have been given elsewhere (d'Abreu, 1958). The development of the apparatus, together with experiences in its laboratory use on 42 consecutive occasions, have already been described by Abrams et al. (1958), whose report should be consulted for further details.A few animals subjected to bypass showed post-operative evidence of neurological damage, a complication also encountered by other workers (Giannelli et al., 1957;Taylor, 1958;Yates et al., 1959) and because of this I was invited to examine the brains of perfused dogs.Thirty-nine brains were received for examination and this paper describes the histological changes. Yates et al. (1959) in a short preliminary communication reported that emboli of silicone anti-foam result in focal brain lesions in dogs perfused with a system incorporating a bubble oxygenator. They found that emboli ranging from 10-80 p were easily seen with a phase-contrast microscope in frozen sections of brain and kidney mounted in a watery medium. At the time of the above report I had found similar lesions and by a process of elimination concluded that silicone emboli were the probable cause, but had not demonstrated the emboli to my own satisfaction. This paper describes the lesions in more detail, supports the findings of Yates et al., and adds experimental confirmation. MATERIALS AND METHODSOperutice procedure. The apparatus ( fig. 1 ) is filled with blood taken from heparinised donor-dogs. The anaesthetised dog is heparinised ( 2 mg. per kg.) and cannulae are inserted into the left common carotid artery (or brachial artery) and the superior and inferior venae cavz?. Blood passes from the venous cannuke via th0 venous hose to the venous pump and then up the vertical tube, the oxygenator, into which oxygen is bubbled through a perforated disk at its lower end, so oxygenating the blood as it ascends. Foaming blood then passes into the wider tube inclined a t 25" to the horizontal, the de-bubbler, 9 J. PATH. BA0T.-YOL. (1960)

The Physiological Aspects of Extracorporeal Circulation

“…Ashton, quoted by Smith (1959) noted circular capillary "holes" in the renal glomeruli of dogs subjected to total cardiopulmonary by-pass using a bubble-oxygenator. He assumed that these were embolic silicone lesions.…”

“…Taylor (1958) described similar neurological damage and Yates et al (1959) demonstrated silicone emboli histologically. Smith (1959) examined the brains of 39 dogs subjected to extracorporeal circulation in Birmingham using a bubble-oxygenator. He found histological evidence of extensive silicone embolism in 28 animals (72 per cent) including lesions in 18 dogs which survived for 14 days after total cardiopulmonary by-pass without obvious clinical neurological damage.…”