Postoperative WBC counts were lower in the carvedilol plus NAC group compared with the metoprolol group ( 12.9 vs 14.8 ; P = 0.004 ) , were similar between the carvedilol and the metoprolol groups ( 13 vs 14.8 ) and between the carvedilol plus NAC group and the carvedilol group ( both P > 0.05 ) .