60 year old 80 kg male patient. Blood group B+ve. Previous PCI During coronary artery bypass grafting surgery, once Cardiopulmonary bypass (CPB) commenced, there were very high pre-oxygenator P1 line pressures in the bypass circuit (450mmHg). The oxygenator was a Medtronic Fusion. P2 post-oxygenator pressures were within 'normal' range. All potential causes were eliminated but it persised.

The high P1 pressures were not resolving and the p02 oxygen measurement started to fall gradually, although not compromising patient oxygenation. Clotting levels were within range and no clots were seen in the oxygenator. The surgeon was kept informed and the situation monitored before progressing with operation. The decision was made to change out the oxygenator. The anaesthetist was informed and the patient was ventilated conventionally.

CPB was stopped and the oxygenator changed. CPB recommenced and the same high P1 pressures seen again but with no compromise to oxygenation so bypass was continued and monitored very closely. After 30 minutes, the pressures fell to 'normal' levels and remained that way for remainder of the bypass. It was also noted that patient haematocrit on CPB was high (38%) and following discussion with the anaesthetist the patient was diluted with the addition of crystalloid.

Post CPB and protamine, a distal vein graft needed repair and heparin was administered and CPB recommenced. P1 and P2 were both within 'normal levels'. As high P1 pressures seen with both devices on initial use, this was suggestive of a patient specific incident. No untoward effects were noted in the post-op period.