Perfusion
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To find out the risk factors influencing perioperative bleeding and use of blood products in cardiac surgery so that appropriate interventions can be selected for blood conservation, risk factors were analysed in 343 cardiac surgical patients, retrospectively, by multiple regression technique. The results showed that the factors related to postoperative bleeding were male gender, Higgins score, cardiopulmonary bypass (CPB) time, operation procedures, intraoperative blood loss and use of internal mammary artery (IMA) graft. Factors related to perioperative homologous blood transfusions were emergency surgery, preoperative haemoglobin level, Higgins score, intraoperative blood loss, operation time and operation procedures. ⋯ The incidence of homologous blood transfusion during the hospital stay was 58.9% for the entire series and 54.5% in the nonrevision patients. Emergency patients received significantly more blood transfusion (p = 0.0001). Perioperative blood loss and transfusions are still problems in cardiac surgery and certain patient groups in this study were identified as high risk; available blood conservation techniques, therefore, are recommended in these patients.
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Comparative Study
Differences in blood activation related to roller/centrifugal pumps and heparin-coated/uncoated surfaces in a cardiopulmonary bypass model circuit.
An in vitro model cardiopulmonary bypass (CPB) circuit consisting ot tubing, oxygenator and venous reservoirs with either a roller or a centrifugal pump, and with either heparin-coated (Carmeda Bioactive Surface, CBAS) or uncoated surfaces, was studied with respect to 'blood activation', using small-scale-based blood volume (450 + 500 ml). Sixteen circuits were tested in each pump group, eight with and eight without heparin-coated surfaces, by circulating heparinized fresh human blood for 72 hours at 30 degrees C. Blood plasma, sampled at defined intervals, was analysed for haemolysis (lactate dehydrogenase and potassium), complement activation (C3bc and C5b-9 (TCC)), complement lytic inhibitors (vitronectin and clusterin), coagulation activation (fibrinopeptide A), granulocyte (lactoferrin and myeloperoxidase) and platelet (beta-thromboglobulin) activation and contaminating endotoxin. ⋯ The two pump types did not differ with respect to these parameters, but the roller pump caused significantly higher increases in plasma LDH and potassium and significantly greater reductions in clusterin and vitronectin than the centrifugal pump. Endotoxin concentration was low at the start and after 24 hours in all groups. These results confirm that heparin-coated CPB surfaces reduce blood activation, and suggest that centrifugal pumps cause less haemolysis and less reduction in lytic complement inhibitors than roller pumps.
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Data relating to the activated clotting time response to a 4 mg/kg heparin loading dose were collected prospectively in 358 patients having cardiopulmonary bypass. After excluding patients with factors known to cause relative heparin resistance or sensitivity, the activated clotting time (ACT) loading dose response ratio (ACTLORR) was calculated retrospectively in 263 patients and found to correlate significantly (p = 0.0001) with the need for extra heparin administration during bypass. ⋯ Where the ACTLORR was between 4.0 and 5.0, it was far less predictive, with approximately 35% of patients requiring additional heparin. This study indicates that a large ACT response to the initial heparin loading dose (a high ACTLORR) is predictive of stable, adequate anticoagulation during the first 90 minutes of bypass, but that a low initial response is not necessarily associated with declining ACTs and the need for additional heparin administration.
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Of the many possible causes of air embolism occurring in patients undergoing cardiopulmonary bypass (CPB), human error due to the perfusionist or the surgeon accounts for the vast majority. This case, however, presents a previously unreported, but recognized, cause of air embolism, due to a technical problem encountered during the administration of blood cardioplegia. ⋯ A situation may then arise whereby air may be entrained and delivered to the patient. The management of massive air embolism is discussed, and recommendations are made to prevent such an occurrence happening in the future.