Case Study: Cardiopulmonary Bypass (CPB)

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1 Cardiopulmonary bypass (CPB)
1.1 Introduction

Cardiovascular diseases are the leading cause of death globally. Different types of cardiac operations are performed every day in hospitals varying in complexity to treat several lesions such as coronary artery bypass graft, heart valve replacement and total heart replacement. Cardiopulmonary bypass (CPB) is a crucial technique employed in the majority of these operations (Punjabi and Taylor 2013). It takes over the function of the heart and lungs during the surgery to maintain the adequate circulation of oxygen and nutrients over the procedure.
1.1.1 Coronary artery bypass graft (CABG)

CABG is a common procedure that used CPB to treat the blockage of the coronary arteries. It diverts blood
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The Hagen-Poiseuille equation is described below:
Blood flow rate= Pressure / resistance.
There are two types of pumps: roller and centrifugal pumps. Both types are widely used due their accuracy and the ability to generate different blood flow rates (Machin and Allsager 2006).
A roller pump is a curved metal shape surrounded by length of PVC and silicon tube. This pump is based on the forward blood flow (positive displacement device). A centrifugal pump instead consists of a plastic cone with a vaned impeller. This cone is powered by electrical motor that generates centrifugal force which is converted into kinetic energy to deliver the blood through the circuit. It has many advantages compared to the roller pump, such as reducing the likelihood of rupture and the disconnection of other circuit components, flow obstruction, and reducing blood trauma.
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Direct contact between the blood from the patient and the tube materials lead to the activation of inflammatory cascades such as complement and coagulation cascades. Therefore, an anticoagulant is necessary to prevent clotting factors during surgery that are associated with these cascades (O 'Carroll-Kuehn and Meeran 2007). Heparin is a popular anticoagulant that used in different operations. The required amount is 300 units/kg, and this is given to the patient and to the CPB circuit (Michelsen et al. 1996).
Priming solutions and CPB circuit

It is essential to use prime solutions and fluids in CPB to prevent any risk of air embolism. The required volume of the priming solutions is determined by the caliber and length of the tube used in both sides (venous and arterial) and the CPB design. The normal priming solution range for adult patients is between 1400 -1800 ml (Gu and Boonstra 2006).
Priming solutions classification
Choosing the appropriate prime solution for CPB has been a concern for a number of decades (Boonstra and Gu 2004). Basically, priming solutions can be classified into two groups: crystalloids and colloids (Gu and Boonstra 2006). The prime solution varies throughout different medical centres based on the cost and ease of use. A comprehensive survey was conducted in 31 cardiac centers in United Kingdom and Ireland showed that surgeons recommended using crystalloids during cardiopulmonary

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