Patients undergoing cardiac surgery with cardiopulmonary bypass require significant fluid administration. Fluids are used routinely to replace blood lost during and after surgery. Significant amounts of fluid are also used to prime the tubing and components of the cardiopulmonary bypass pump before and during its use. The use of Pentaspan - a synthetic pentastarch - was started because of the restriction of use for blood and blood products, particularly albumin. Pentaspan is usually used after surgery in the Intensive Care Unit (ICU). The impact of the use of pentastarch on coagulation, fluid balance and bleeding are very limited. This study will methodically evaluate the impact of using increasingly greater amounts of pentastarch during surgery on an open heart surgery patient's recovery in particular - is there more bleeding, does his/her blood clot as well, and how much fluid overall is used and excreted?

Inclusion Criteria:

• All patients undergoing either coronary artery bypass surgery or valve surgery requiring the use of cardiopulmonary bypass circuit

Exclusion Criteria:

• Emergency surgery
• Regurgitant valve pathology
• Redo surgery
• Significant left ventricular (LV) dysfunction
• Significant renal insufficiency
• Anticipation of associated procedure - eg carotid endarterectomy
• Ongoing sepsis or endocarditis
• Received aspirin (ASA) or Plavix within 96 hours of surgery