A prospective study was conducted with the aims of 1) determining the normal trans-oxygenator pressure gradient characteristics for a range of oxygenators and 2) determining the characteristics, incidence and outcome of abnormally raised gradients. The trans-oxygenator pressure gradient was monitored in 3684 patients undergoing open-heart surgery in eight different hospitals. When the normal pressure gradient was measured during cardiopulmonary bypass in mmHg/L blood flow, a constant figure was obtained which was specific for each oxygenator. This gradient was abnormally raised in 16 cases (one in every 230 cases) and was raised to such an extent in three of these cases that an emergency oxygenator changeout was required (one in every 1228 cases). Among the 16 reported incidents, three different patterns of gradient changes occurred, suggesting the possibility that there were three different aetiologies. In nine of these incidents, the pressure gradient was normal immediately upon going on bypass, but rose rapidly to a plateau value, which then returned to the normal value within 40 minutes. In three cases, the pressure gradient was raised immediately upon going on bypass and then rapidly returned to the baseline. In one case, the pressure gradient was raised immediately upon going on bypass and stayed raised throughout the operation.

This prospective study confirms incidence of intraperitoneal anaerobic metabolism of glucose during CPB and impaired utilisation of glucose in the postoperative period. Microdialysis provides a novel and minimally-invasive method to measure real time intraperitoneal events.

Fenoldopam infusion induced transient tachycardia, with no augmentation of hepatic blood flow whereas dopexamine induced tachycardia and did not augment hepatic blood flow. Fenoldopam and dopexamine may have hepato-protective effect.

Higher pump flows during hypothermic CPB increase hepatic blood flow. There was a trend towards attenuation of post-operative inflammatory response; however, larger studies will be needed to confirm these findings.

Increasing numbers of obese patients are presenting for cardiac surgery. The convention for heparin dose dictates that a bolus of 300 IU heparin per kilogram of total body weight (TBW) is administered before CPB. During CPB, the activated clotting time (ACT) is maintained for longer than 480 seconds. At the end of the procedure, protamine is administered to neutralize heparin and achieve hemostasis. Both of these drugs can have serious side effects: heparin can induce thrombocytopenia, and protamine has been known to cause reactions in patients allergic to fish, vasectomized men, and some patients with insulin-dependent diabetes. The calculation of lean body mass (LBM) may be a more accurate method of determining drug doses as opposed to TBW and may avoid giving obese patients a relative overdose of heparin, which must subsequently be neutralized with protamine. LBM can be determined by different methods. This study used bio-electrical impedance analysis as a simple, quick, and accurate method of calculating LBM. A comparison was made between two groups of patients whose body mass index (BMI) was >27 kg/m2: Group 1, n _ 13, mean BMI _ 32, mean body fat _ 36% received the conventional dose of 300 IU/kg heparin for their TBW. Group 2, n _ 14, mean BMI _ 31, mean body fat _ 35% received a dose of 300 IU/kg heparin for their calculated LBM. ACT was conducted before and after heparin administration. Additional heparin was administered as required to achieve target ACT > 400 s. Mean ACT results and total heparin doses were analyzed using unpaired two tailed t tests. Our results indicate that with care, a reduction of as much as 25% in the doses of heparin (p_0.0001) and protamine can be achieved for a substantial number of patients classified as overweight or obese.