Discussion:
CPB is a standard procedure in paediatric cardiac surgery.[3]The general principles of CPB are same for neonates and adults. It requires aortic and bicaval cannulations, andsome modifications are necessary to accommodate the multiple anatomical variations that may be encountered in congenital defects i.e. two aortic and three cava cannulas in associated interrupted aortic arch and a persistent left superior vena cava (LSVC) for adequate drainage during the CPB.[4] The aortic cannulation is primarily done at the distal ascending aorta, positioning the cannula close to the origin of the brachiocephalic trunk.[5]The appropriate arterial cannula size depends upon the required CPB flow, calculated using the formula ;CPB blood flow rate (litre/ min)=Body surface area (BSA)(m2)×Cardiac index (CI),(L m−2/min). Flows of 1.8 to 2.5 L/min/m2 are commonly used for infants, children, and adults during mildtomoderate systemic hypothermia.The pump flow for this patient was calculated as Weight in KG x 150 ml/min= 750ml/min and accordinglyrecommended aortic cannula of 12 Fr for 700 ml – 1000 ml flow was used.If a cannula is too large, it can obstruct native heart output, particularly in the ascending aortic position as this output is critical during cannulation and the initiation and weaning phases of bypass, also too large of a cannula may require an aortotomy that is difficult to close in a standard fashion. Therefore, aortic cannula size should be selected in conjunction with the perfusionist team to utilize the appropriate cannula for adequate flow during CPB.Table below shows general sizes of cannulas used for initiating CPB.