Prevention of Overoxygenation During Treatment with a Heart-Lung Machine in Cardiac Operations

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MANY improvements have been made on oxygenators of heart-lung machines to assure sufficient oxygenation of blood, but little attention has been given to the problem of avoiding overoxygenation of blood. The possible dangers of overoxygenation, and its prevention by means of a polarograph are discussed in this paper.

Overoxygenation of blood is likely to occur under the following conditions: (1) during recirculation of blood through an oxygenator prior to connection of a patient to the machine; (2) during partial cardiac bypass with a small flow rate, which is a routine procedure at the beginning and at the end of many perfusions; and (3) during perfusion of a small patient with an oxygenator of large capacity.

Our use of the polarograph in the control of oxygenation was based on our impression that some sudden and unexpected fatalities that occurred 10 to 12 hours after perfusion might be due to overoxygenation of the patients’ blood during treatment with heart-lung machines. Kirklin1 has reported a similar impression.

Effect of Oxygen Excess

The data on toxicity of oxygen are scarce. Ninety to 95 per cent of oxygen at atmospheric pressure can be breathed by man for short periods without ill effects; however, Pichotka and Kühn2,3 found that in guinea pigs and rabbits degenerative changes of the liver occur after exposure to 90 per cent of oxygen for eight hours every day for 90 days, and that death eventuates after continuous exposure of from 65 to 75 hours. Necropsy of these animals showed severe damage. . .



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