The efficacy of early supplemental intravenous immunoglobulin G (ivIgG) treatment was investigated in 41 patients at risk for sepsis following cardiac surgery (APACHE II score > or = 19 on the 1st postoperative day). The ivIgG preparation (Psomaglobin N) was chosen because of its reported high antibody titers and effectiveness in animal models against gram-positive microorganisms, preponderant as infective agents after heart surgery. The control group consisted of a historical cohort of 42 cardiac surgical patients of comparable pretreatment disease and sepsis severity. Following ivIgG therapy on the 1st and 2nd days after surgery, we found a marked improvement in disease severity (fall in APACHE II scores) in contrast to the control patients, especially evident in the high-risk group of patients with an APACHE II score > or = 24 on the 1st postoperative day (n = 26). In this group, ivIgG therapy led to higher (p < 0.05) response rates defined as a score decrease > or = 7 within 4 days (ivIgG-treated patients 54%, controls 19%), and a reduction in mortality (ivIgG-treated patients 46%, controls 76%; p = 0.08). Given the good comparability of the study groups, the results of this trial indicate, despite its nonrandomized design, that early supplemental ivIgG treatment seems to decrease disease severity and probably also improve the prognosis in APACHE II score identified high-risk patients after cardiac surgery.