During the use of Cardiopulmonary Bypass (CPB) for cardiac surgery there is an instant mixture of the patient's blood and the fluid needed to fill the extracorporeal circuit before use. This will change the composition of the body fluids. This study aims to plot these changes in regard to particle concentration (osmolality).

During the use of CPB for cardiac surgery there is an instant mixture of the patient's blood and the fluid needed to prime the extracorporeal circuit. Many studies have pointed to the benefits of using a hyperosmolar prime to counteract formation of tissue oedema. Rapid changes in osmolality may as a serious consequence lead to osmotic demyelination syndrome. At the Heart Centre of Umeå University Hospital, Sweden, there is a tradition of using a hyperosmolar prime. This study aims to explore changes in osmolality during coronary artery bypass grafting surgery by repeated measurements of osmolality and concentration shifts of sodium, glucose and urea in plasma.

Inclusion Criteria:

• Age 60-80 yr
• New York Heart Association Functional Classification(NYHA) I-III
• Body Surface Area(BSA) 1.8-2.5 m2

Exclusion Criteria:

• Diabetes
• Estimated Glomerular Filtration Rate(eGFR)<50ml/min/1,73 m2

Patients subjected to coronary artery bypass grafting with the aid of Cardiopulmonary Bypass.

Data will be shared after reviewing final results after study completion at this site and through publication in a scientific journal.