Maximal oxygenation of dilute blood cardioplegic solution.

The content of dissolved O2 (the major source of O2 for the myocardium) of dilute blood cardioplegic solution (dBCS) varied widely when oxygenated at 4 degrees C by surface flow of O2 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 O2 through a 16-gauge intravenous catheter in a central Luer-Lok port of the cardiotomy reservoir provided contents of dissolved O2 that were consistently near maximal. We then studied 17 patients in the operating room. The first 6 patients received dBCS oxygenated with 100% O2 with a high dissolved O2 content of 3.2 +/- 0.2 ml/dl. However, the pH of the dBCS became highly alkaline (7.83 +/- 0.11 at 37 degrees C). Therefore, in the remaining 11 patients, 2% CO2 was added to the O2. The dissolved O2 content remained high (3.3 +/- 0.1 ml/dl), and the pH was in a more physiological range (7.35 +/- 0.09 at 37 degrees C). We conclude that consistently maximal oxygenation of a dBCS at a more physiological pH can be achieved by this method.