WHICH TECHNIQUES OF CARDIOPLEGIA PREVENT ISCHEMIA

One hundred seven patients undergoing coronary artery bypass grafting were randomized to receive warm antegrade (n = 21), warm retrograde (n = 22), cold antegrade (n = 20), cold retrograde (n = 22), or intermit tent cold antegrade (n = 22) blood cardioplegia. Myocardial oxygen con sumption and lactate production, adenine nucleotides, and adenine nucl eotide degradation products were measured during the operation, and cr eatine kinase-MB release was assessed postoperatively. Warm cardiopleg ia resulted in greater myocardial lactate production than cold cardiop legia (p = 0.048). Retrograde cardioplegia was associated with greater lactate production than antegrade cardioplegia (p = 0.015). Adenosine triphosphate depletion was similar among groups. However, poorly diff usible metabolites of adenosine triphosphate accumulated to the greate st extent in the intermittent cold group. Levels of hypoxanthine were highest after warm retrograde cardioplegia. Operative mortality and mo rbidity were low and were not different among groups. In summary, none of the five techniques of cardioplegia evaluated in this study was ab le to completely prevent myocardial ischemia. Anaerobic lactate produc tion was minimized with cold cardioplegia and with antegrade cardiople gic delivery. Hypothermia may have impaired regeneration of adenosine triphosphate, however, particularly in association with inadequate or intermittent cardioplegic flow.