OPTIMAL FLOW-RATES FOR INTEGRATED CARDIOPLEGIA

Background: Antegrade cardioplegic delivery may be impaired by coronar y occlusions, whereas retrograde delivery of cardioplegic solution may be inhomogeneous, leading to an accumulation of lactate and hydrogen ions, the products of anaerobic metabolism, Integrated cardioplegia us ing continuous retrograde cardioplegia and antegrade infusions into co mpleted vein grafts washes out metabolites accumulated in regions inad equately perfused by retrograde cardioplegia alone, To determine the h ow rates required to achieve the greatest washout, we compared a high flow rate (200 ml/min) to a low flow rate (100 ml/min). Methods: Twent y patients scheduled for isolated coronary bypass surgery were prospec tively randomized to compare two flow rates for integrated cardioplegi c protection using tepid (29 degrees C) blood cardioplegia, Arterial a nd coronary sinus blood samples were collected to evaluate myocardial metabolism, After antegrade arrest, cardioplegic solution was delivere d by coronary sinus perfusion and simultaneous infusions into each com pleted vein graft at either high or low flow. Results: Increasing from low to high flow increased the washout of lactate and hydrogen ions d uring the aortic crossclamp period, Two hours after crossclamp removal , ventricular function was better in the high flow group, Conclusions: Tepid retrograde cardioplegia resulted in an accumulation of toxic me tabolites, The addition of antegrade vein graft infusions at a flow ra te of 100 ml/min resulted in a washout of these metabolites, A flow ra te of 200 ml/min further improved this washout and resulted in improve d ventricular function, An integrated approach to myocardial protectio n using a flow rate of 200 ml/min may improve the results of coronary bypass surgery.