Heart-Lung Machine: Impact of the Priming Solution on Acid-Base Balance, Electrolytes and Outcome on Patients Undergoing Cardiac Surgery

Most cardiac surgery procedures requires the use of heart-lung machine. The heart-lung machine circuit needs to be filled with a fluid before connecting it to the patients circulation. This is called priming and is accomplished by filling the circuit with a solution used for fluid replacement. The circuit in our institution requires 1100 mL to be filled. The body has several mechanisms with the purpose to maintain its state of balance. When a large amount of clear solution suddenly enters the blood stream this balance can be altered. The goal of this clinical trial is to investigate different priming solutions in the heart-lung machine circuit. The main questions it aims to answer are: How do different priming solutions alter the acid-base balance, osmolality and electrolytes which reflects the body's water balance for patients undergoing cardiac surgery with the use of heart-lung machine? There will be 4 different groups: 1. Ringer-Acetate, 1100 mL / no addition 2. Ringer-Acetate, 1100 mL + 80 mmol sodium chloride (NaCl) 3. Ringer-Acetate, 1100 mL + 160 mmol NaCl 4. Plasmalyte, 1100 mL / no addition Blood samples will be taken before, during and after surgery, post operative day 1 and 4 to analyze acid-base balance, electrolytes, and plasma osmolality. Urine output and hydration status will also be collected until post operative day 1. After 3 months, a blood sample will be taken for analysis of electrolytes and kidney function.