We studied 64 patients who underwent cardiac surgery. Hemodynamic and metabolic variables-cardiac index (CI), total peripheral resistances (TSR), oxygen consumption and (VO2), urinary output, alveolar-arterial oxygen difference (delta A-a O2) - were related with oxygenator (bubble or membrane oxygenator) and with treatment (with or without methylprednisolone). 31 patients were perfused with membrane oxygenator (MO), 33 with bubble oxygenator (BO), 13 patients MO and 18 patients, BO were treated with methylprednisolone (mps). The analyzed variables were sampled 15 minutes after the start and one to five times during the perfusion. At first data were analyzed in terms of mean values in whole set of time intervals. Only delta A-a O2 showed statistically significant difference between the MO and the BO group (282 +/- 110 versus 361 +/- 82, p less than 0.005). Between nomps-treated and mps-treated patients statistically significant difference were found in TSR (2.134 +/- 362 versus 1.785 +/- 317, p less than 0.005) and in delta A-a O2 (293 +/- 92 versus 355 +/- 108, p less than 0.02). Secondo analysis is concerning time change of variables. The time behaviour of TSR is similar in all groups studied, but a statistically significant lower value was found in mps-treated patients in every time interval. The VO2, in the last time interval, is statistically higher in the mps-treated than in the nomps-treated patients (p less than 0.05) and furthermore, for the same temperature change, the rise of VO2 is higher in the mps-treated (p less than 0.001). The delta A-a O2 shows time increase both in the MO and in the BO group, but the MO patients start from statistically significant lower values than the BO and the behaviours remain parallel for all analyzed time. The results are interpreted and discussed in relation to hemodynamic and metabolic patterns of perfusion as good or bad tissue perfusion.