Abstract
Blood cardioplegia in conjunction with iced slush topical cooling has been shown by the authors' group and others to cause postoperative conduction disturbances in 50% of patients. Because this is significantly higher than crystalloid cardioplegia, they tested whether a lower concentration of blood in the cardioplegia mix might change the rheology of the solution and hence lower the conduction defects if cold sludging of red blood cells caused the defects. They compared 289 consecutive patients receiving 4:1 blood cardioplegia (BC) with 90 consecutive patients who received 2:1 blood cardioplegia for the presence of postoperative conduction defects.
The 4:1 BC caused conduction defects in 141/289 (49%) patients versus 8/90 2:1 BC patients (9%) (p=0.01). Perioperative heart block requiring pacing occurred in 67 patients with 4:1 BC (23%); no patients with 2:1 BC required pacing (p=0.001). Only 10 of 141 (7%) 4:1 BC patients had resolution of conduction defects prior to discharge, whereas all 2:1 patients but 1 resolved their defects within twelve hours of operation (p=0.05). There was no difference in patients' ages, grafts, ischemic time, or cardioplegia amount. Iced slush was used in all patients.
The authors conclude that the concentration of blood in cardioplegia solutions appears to have a direct effect on postoperative conduction disturbances; their group now routinely uses a 2:1 mixture. This concentration allows continued use of iced slush topical cooling.
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