Cardiopulmonary bypass (CPB) exposes blood to artificial surfaces, which induces a systemic inflammatory activation.This may contribute to hypotension during CPB. A perceived difference between two membrane oxygenators was noted. Data were collected on 222 consecutive patients; four were excluded from the analysis due to having emergency operations. One hundred and twelve (51%) patients received the Apex oxygenator whilst 106 (49%) received the Quadrox. There was no difference between the two groups in the primary outcome; 90/112 patients (80%) in the Apex group and 77/106 (73%) in the Quadrox group (p=0.18, OR: 0.65; 95% CI: 0.34, 1.22) received meteraminol due to marked hypotension during CPB. There was also no difference in the secondary outcomes, length of stay in ICU (22.8 versus 22.7 hours, (OR 0.79, 95% CI: 0.42, 1.48, p=0.16) and length of stay in hospital (8.5 days versus 8.0 days (OR: 0.83, 95% CI: 0.48, 1.45; p=0.52). The choice of oxygenator between the Apex and Quadrox does not have an effect on hypotension in cardiac surgery.