Complement activation was studied during cardiopulmonary bypass (CPB) in the pig. One group of animals was perfused for 2 h using a standard extracorporeal circuit including a hollow fiber membrane oxygenator with full systemic heparinization. Another group was treated in the same way, except that bypass was performed through a heparin‐coated CPB circuit (Carmeda Bio‐Active Surface, CBAS) and systemic heparinization was reduced by 75%. It was found that complement activation during CPB, measured as changes in the ratio C3d/C3, was significantly less in the CBAS group, most probably reflecting a better biocompatibility.
Blood cell trauma and postoperative bleeding remain important problems in cardiopulmonary bypass (CPB). We compared heparin-coated with non-coated circuits in the pig. Twenty animals were perfused for 2 h at normothermia using membrane oxygenators (Bentley Bos 50). Two groups were studied. In the non-coated group (NC, n = 11) the CPB circuits used were without a heparin coating. This group had systemic heparinization of 400 IU/kg to maintain an ACT (activated clotting time) of over 400 s during CPB. In the coated group (C, n = 9), all surfaces exposed to blood in the CPB circuits were heparin-coated. This group had the heparin dose reduced to 25% (100 IU/kg) without further administration regardless of ACT. During CPB, group C displayed shorter ACT (per definition), higher platelet count, platelet adhesion and lower fibrinolysis and haemolysis (P less than 0.05) as compared to group NC. No thromboembolic events were detected during CPB. Three animals in group NC and 4 animals in group C were weaned from CPB and protaminized. Four hours postoperatively, the leucocyte consumption was two-fold greater and blood loss about four-fold greater in group NC as compared with group C (P less than 0.05). Perfusion with heparin-coated surfaces reduces blood cell trauma. The decreased postoperative blood loss observed in group C is probably explained by the reduced dosages of heparin and protamine.
During myocardial ischemia there is a drop in high-energy phosphates in the myocardium. Cold potassium cardioplegia decreases but does not altogether prevent this reduction. Supplementation of cardioplegic solutions with the high-energy compound creatine phosphate (10 mmol/L) compared to plain cardioplegic solutions was investigated in this study. Thirty patients scheduled for aortic valve replacement were included. The patients were randomized to group I (creatine phosphate) or group II (control). Postoperative hemodynamic evaluation revealed no significant differences between the groups. However, group I exhibited a tendency toward a better stroke-work index (135 +/- 18% vs. 102 +/- 5% recovery 15 minutes after bypass and 145 +/- 16% vs. 119 +/- 11% recovery 105 min after bypass). There were fewer patients in group I (5/15) needing inotropic support compared to group II (9/14). The myocardial content of ATP and creatine phosphate showed no significant differences during ischemia and reperfusion. It is concluded that the myocardial protection during ischemia was sufficient to prevent significant reductions of myocardial ATP and creatine phosphate irrespective of supplementation with CP.
The present study tests the hypothesis that the changes in myocardial lactate metabolism in the early period of coronary surgery are caused by raised adrenergic activity, and that these are preventable by the addition of thoracolumbar epidural blockade to high dose fentanyl/midazolam anesthesia. Twenty-seven male beta 1-blocked patients undergoing coronary surgery were included in a prospective, controlled, randomized study. High dose fentanyl/midazolam anesthesia alone (control) or supplemented with thoracolumbar epidural blockade (treatment) was used. Measurements were performed before the induction of anesthesia and after sternotomy. After sternotomy adrenaline (A) and noradrenaline (NA) had decreased and were both in the low range, especially in the epidural group (P < 0.01). Arterial pressures decreased in both groups, especially in the epidural group, where coronary perfusion pressure (CPP) decreased from 61 (42-88) to 48 (33-64) mm Hg; Systemic vascular resistance (SVR) decreased with 30% in the epidural group (P < 0.01), but not significantly in the control group. The myocardial fractional extraction of lactate decreased in both groups, from 33 (10-45) to 13 (0-42)% in the control group (P < 0.01), and from 36 (19-43) to 10 (2-20)% in the epidural group. It is concluded that high dose fentanyl/midazolam anesthesia prevents hyperadrenergic activity in the early phase of coronary surgery, but cannot eliminate changes in myocardial lactate metabolism. The addition of the thoracolumbar epidural blockade to high dose fentanyl/midazolam anesthesia offers no obvious benefits in the early phase of coronary surgery.
Myocardial substrate metabolism is abnormal in the early period after cardiac surgery. Myocardial uptake of substrates remains restricted 6 hours postoperatively and cannot match the demand during periods of increased energy requirements. We investigated the relationship between myocardial oxidative rate and substrate uptake in 22 men c. 8 hours after coronary surgery. Myocardial energy demand was raised experimentally by infusing dopamine. The influence of selective beta 1-blockade was analyzed. The uptake of free fatty acids dominated (34.74 +/- 8.83 mmol/min*10(-3) and sufficed to explain the oxygen consumption in basal postoperative conditions (0.468 +/- 0.051 mumol/min) and during amplified energy requirements (0.881 +/- 0.117, r = 0.71). Although the capacity to adjust substrate uptake to energy requirements thus was regained, the uptake of glucose and of lactate (6.14 +/- 13.13 and 2.29 +/- 20.31 mmol/min*10(3) respectively) was marginal, which may be important for ischaemic tolerance. Metoprolol influenced oxygen consumption during amplified adrenergic activity, but did not markedly affect substrates.
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