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Comparison of cardioplegia methods in patients undergoing cardiopulmonary bypass surgery / by Suzanne Lyn Schaller, B.S.

by Schaller, Suzanne Lyn

Cardiac arrest, Induced

Heart Arrest, Induced

Intraoperative Complications -- prevention & control

Postoperative Complications -- prevention & control

Potassium Channels -- metabolism

vi, 96 leaves : ill. ; 28 cm.

Advisors: Dr. Charles Tritt, Charles Altenbern

Committee members: Dr. Larry Fennigkoh, Dr. Vincent Canino

Introduction -- Problem -- Background -- Purpose -- Hypotheses -- Materials and Methods -- Results -- Potassium -- Myocardial Protection -- Electrolytes -- Hematocrit -- Cost Evaluation -- Discussion -- Conclusion -- References -- Appendix A) Instructions for Authors B) Large-Sample Significance Test C) Institutional Review and Patient Informed Consent Documents D) Raw Data Tables

Two cardioplegia methods currently utilized at St. Luke’s Medical Center, Milwaukee, Wisconsin are the BCD VanguardTM to deliver Buckberg solutions (Buckberg) and the Quest Myocardial Protection SystemTM to deliver potassium chloride and magnesium sulfate (Quest). While the Buckberg is widely used and its performance well documented, concerns have arisen regarding high serum potassium levels – perhaps due to its design limitations – and the cost of its customized crystalloid solutions. In addition to being less expensive to operate, the recently introduced Quest offers more flexible and precise potassium delivery, but little published data is available on its impact on serum potassium levels and myocardial protection.

The study was undertaken to compare the effects of the Buckberg and Quest on serum potassium levels, myocardial protection, hemodilution, and cost. The study compared potassium levels at the time the aortic cross-clamp was removed, potassium balance at termination of cardiopulmonary bypass by subtracting urinary excretion and hemofiltrate from the sum of contributions from cardioplegia, blood transfusion, fluid administration, and hemolysis. Myocardial protection was analyzed by comparing cardiac index; cardiac output; time to arrest; activity between cardioplegia doses; number of patients who required cardiac pacing, defibrillation, inotropes, and intra-aortic balloon pump; and intensive care unit and hospital stay.

The effect on hemodilution was compared by measuring hemotocrit levels at the time the aortic cross-clamp was removed and administration and excretion of fluid during CPB. A cost evaluation was performed on the cardioplegia disposable delivery sets, equipment, and the solutions utilized with each method.

Statistical analysis was performed using Microsoft Excel 97 (Microsoft Corporation, USA) and Systat® 6.0 for Windows® Student Version (SPSS Inc., Chicago, IL) (significant differences were defined as probabilities for each test of p ≤ 0.05). Two of the 40 patients were excluded from the electrolyte statistical analysis due to specimen containing hemolyzed blood from incorrect collection. The two-student sample t-test (or independent t-test) was used on continuous data to compare means from the Buckberg and Quest groups. A binomial large-sample significance test was used to compare count-data from the Buckberg and Quest groups. One-way analysis-of-variance (ANOVA) and Bonferroni pairwise procedures were used to compare means of continuous data from three groups based on serum potassium levels.

The study found no significant difference between the Buckberg and Quest in regards to their effect on serum potassium levels or myocardial protection. The two methods did not differ significantly on hematocrit values, but the Quest patients did receive significantly more packed red blood cells than the Buckberg group. It was found that the Quest is less expensive with a total cost saving of $247.50 per case.

It was concluded that both the Quest and Buckberg provide adequate myocardial protection and that the occurrence of high serum potassium levels appears to be due to potassium homeostasis rather than the amount of potassium delivered by either method. All three groups (normal, mild, and moderate to severe hyperkalemia group) in the ANOVA analysis had approximately the same potassium intake from cardioplegia and other sources, however, the preoperative creatinine was higher in the moderate to severe hyperklalemia group and the normal group had a significantly higher urine output. This data suggests the importance of renal function in regards to potassium homeostasis rather than the actual amount administered.

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