Patients receiving lower dose of heparin has lower postoperative blood loss. Of those achieving the target ACT, group B was significantly the closest to the target ACT. A starting dose of 200 iu/kg of heparin and if necessary one 50 iu/kg increment achieved target ACT in 81.5% of patients. The added benefit of significant drop in postoperative blood loss is evident.

The incidence of electrical failure during cardiopulmonary bypass (CPB) has been reported to occur in approximately 1 per 1000 cases. While the resultant morbidity and mortality is low, electrical failure is a life-threatening scenario. We report three major electrical failures during CPB in a patient population of 3500 over a 15-year period. These cases involved mains failure and generator shut down, mains failure and generator power surge, and failure of the uninterruptable power supply (UPS), which caused protected sockets to shut down. Protocols for preventative maintenance, necessary equipment, battery backup and guidelines for the successful management of such accidents during CPB are discussed.

We have previously demonstrated the role of univentricular pacing modalities in influencing coronary conduit flow in the immediate post-operative period in the cardiac surgery patient. We wanted to determine the mechanism of this improved coronary conduit and, in addition, to explore the possible benefits with biventricular pacing. Sixteen patients undergoing first time elective coronary artery bypass grafting who required pacing following surgery were recruited. Comparison of cardiac output and coronary conduit flow was performed between VVI and DDD pacing with a single right ventricular lead and biventricular pacing lead placement. Cardiac output was measured using arterial pulse waveform analysis while conduit flow was measured using ultrasonic transit time methodology. Cardiac output was greatest with DDD pacing using right ventricular lead placement only [DDD-univentricular 5.42 l (0.7), DDD-biventricular 5.33 l (0.8), VVI-univentricular 4.71 l (0.8), VVI-biventricular 4.68 l (0.6)]. DDD-univentricular pacing was significantly better than VVI-univentricular (P=0.023) and VVI-biventricular pacing (P=0.001) but there was no significant advantage to DDD-biventricular pacing (P=0.45). In relation to coronary conduit flow, DDD pacing again had the highest flow [DDD-univentricular 55 ml/min (24), DDD-biventricular 52 ml/min (25), VVI-univentricular 47 ml/min (23), VVI-biventricular 50 ml/min (26)]. DDD-univentricular pacing was significantly better than VVI-univentricular (P=0.006) pacing but not significantly different to VVI-biventricular pacing (P=0.109) or DDD-biventricular pacing (P=0.171). Pacing with a DDD modality offers the optimal coronary conduit flow by maximising cardiac output. Biventricular lead placement offered no significant benefit to coronary conduit flow or cardiac output.

The practice of flushing the cardiopulmonary bypass circuit and oxygenator with carbon dioxide (CO 2) has been shown to reduce priming time. However, the optimal flow rate of CO2 and the time for which it must be flushed through the circuit in order to remove the air, have not been determined. In this experiment, CO2 was passed through the arterial filter and arteriovenous (AV) loop at various flow rates and serial gas samples were taken from the circuit. The residual concentration of air in each sample was measured using a gas chromatograph. It was shown that as the flow rate of CO2 was increased, the time taken to remove the residual air decreased. Flushing the circuit with CO2 at a flow rate of 6 l/min for four minutes ensures a residual air concentration of less than 0.01%.

Errors in blood flow delivery due to shunting have been reported to reduce flow by, potentially, up to 40-83% during cardiopulmonary bypass. The standard roller-pump measures revolutions per minute and a calibration factor for different tubing sizes calculates and displays flow accordingly. We compared displayed roller-pump flow with ultrasonically measured flow to ascertain if measured flow correlated with the heart-lung pump flow reading. Comparison of flows was measured under varying conditions of pump run duration, temperature, viscosity, varying arterial/venous loops, occlusiveness, outlet pressure, use of silicone or polyvinyl chloride (PVC) in the roller race, different tubing diameters, and use of a venous vacuum-drainage device.