Fifty patients perferming the open heart surgery with cardiopulmonary bypass have been studied to define serum potassium and PaCO2 changes associated with anesthesia, bypass and hypothermia.
For a long time in maintaining normal heart action the importance of potassium has been known. The first successful heart operation under cardiopulmonary bypass was performed by Gibbon. Since then, a fall in plama potassium during bypass has been noted by many workers.
Hypokalemia is prone to occur following cardiopulmonary bypass. Oxygenator primed with hemodilution techniques found a decreased potassium concentration. In addition to the diluted priming solution, there is the number of factors to hypokalemia such as respiratory alkalosis, post-operative urinary excretion and anticipated maximal aldosterone response associated with maximum stress. Hypokalemia should be avoided by including potassium chloride in the priming solution and during extracorporeal circulation the dose of potassium supplements should be determined entirely by plasma potassium. .
Bubble oxygenation is the most widely used principle for heart lung bypass during open heart surgery.
In the Rygg-Kyvsgaard oxygenators the size of the bubble is 1.5-3mm. Arterial carbon dioxide tension is kept normal and about 40mmHg, the concentration of COZ ´supplied to the oxygenator is varied according to the temperature.
In the using of the Rygg-Kyvsgaard heart lung machine, low arterial carbon dioxide tension seems mainly to be eliminated due to bubbles of high gas flow rate. A1teroation in the serum and urine potassium was studied in fifty patient who underwent open heart
surgery in National Medical Center during the period from Mar. 1977 to Dec. 1978, and the following results were obtained.
1) Total number of patient on this study. wass 50 cases, and among them 29 cases were male and 21 cases were female.
2) The sum of congenital heart failure was 31 cases (62%) and acquired heart failure was 19 cases (38%).
3) Reviewing of the pumping time, over 3 hours were 9 cases (18%) between 3 hours and 2 hours were 22 cases (40161) and within 1 hour were 191cases (38%).
4) Preoperative serum potassium level was 4.3mEq/L, and at the pumping serum potassium
level was 3. gmEq/L, and end of bypass serum potassium level was 3.6MEq/L.
5) During extracorporeal circulatron, potassium level in urine was 22mEq/L at average ane
potassium was added 36.4mEq/L for male and 39.6mEq/L for female.
6) During extracoreal circulation, PaCOZ showed 35 tors immediately after pumping and the lowest level was 25 torr 80 minutes after pumping started.
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