Maximal oxygenation of dilute blood Cardioplegic solution

Abstract

The content of dissolved O 2 (the major source of O 2 far the myocardium) of dilute blood cardioplegic solution (dBCS) varied widely when oxygenated at 4 °C by surface flow of O 2 in a Bentley BCR-3500 cardiotomy reservoir. We have modified the system to consistently deliver maximally oxygenated dBCS to the heart. Laboratory studies indicated that bubbling O 2 through a 16-gauge intravenous catheter in a central Luer-Lok port of the cardiotomy reservoir provided contents of dissolved O 2 that were consistently near maximal. We then studied 17 patients in the operating room. The first 6 patients received dBCS oxygenated with 100% O 2 with a high dissolved O 2 content of 3.2 ± 0.2 ml/dl. However, the pH of the dBCS became highly alkaline (7.83 ± 0.11 at 37 °C). Therefore, in the remaining 11 patients, 2% CO 2 was added to the O 2. The dissolved O 2 content remained high (3.3 ± 0.1 ml/dl), and the pH was in a more physiological range (7.35 ± 0.09 at 37 °C). We conclude that consistently maximal oxygenation of a dBCS at a more physiological pH can be achieved by this method.