Washing of stored red blood cells by an autotransfusion device before transfusion.

BACKGROUND AND OBJECTIVES: The use of an autotransfusion device to wash blood of the incision site is increasing. After washing, this blood is retransfused without side effects caused by activated plasma factors and cell release products. This procedure could be extended to washing of donor blood, which may be particularly useful for red blood cells (RBCs) stored for more than 4 weeks that contain high concentrations of free haemoglobin, potassium, lactate and other metabolites. It is not known whether stored RBCs can withstand the cell washing procedure with the use of an autotransfusion device, while keeping their primary functions intact. The objective of this study was to determine the quality of RBCs, after cell washing in comparison to untreated RBCs. MATERIALS AND METHODS: RBCs were studied in terms of integrity (free haemoglobin), stored energy (2,3-diphosphoglycerate, adenosine triphosphate), metabolites (lactate, potassium) and physical characteristics (osmotic resistance, aggregability, deformability). RESULTS: After washing, free lactate and potassium were significantly reduced as compared to the levels before washing. The osmotic resistance of RBCs slightly improved, whereas aggregation capacity reduced after washing. Fifteen per cent of haemoglobin was lost during washing. The deformability and free haemoglobin levels remained unchanged. CONCLUSION: Washing stored blood before transfusion may be of benefit, because the waste products are effectively removed from the stored RBC.

Induction and detection of disturbed homeostasis in cardiopulmonary bypass.

During cardiopulmonary bypass (CPB) haemodynamic alterations, haemostasis and the inflammatory response are the main causes of homeostatic disruption. Even with CPB procedures of short duration, the homeostasis of a patient is disrupted and, in many cases, requires intensive postoperative treatment to re-establish the physiological state of the patient. Although mortality is low, disruption of homeostasis may contribute to increased morbidity, particularly in high-risk patients. Over the past decades, considerable technical improvements in CPB equipment have been made to prevent the development of the systemic inflammatory response syndrome (SIRS). Despite all these improvements, only the inflammatory response, to some extent, has been reduced. The microcirculation is still impaired, as measured by tissue degradation products of various organs, indicating that CPB may still be considered as an unphysiological procedure. The question is, therefore, whether we can detect the pathophysiological consequences of CPB in each individual patient with valid bedside markers, and whether we can relate this to determinant factors in the CPB procedure in order to assist the perfusionist in improving the adequacy of CPB. The use of these markers could play a pivotal role in decision making by providing an immediate feedback on the determinant quality of perfusion. Therefore, we suggest validating the proposed markers in a nomogram to optimize not only the CPB procedure, but also the patient's safety.

Surgical sealant in the prevention of early vein graft injury in an ex vivo model.

BACKGROUND: The amelioration of the adaptation process (arterialisation) of the vein graft wall to the arterial circulation in coronary artery bypass surgery by using extravascular support is clearly established in animal models and in in vitro and ex vivo set-ups. This support consists of some form of external graft-supporting modality like a prosthetic graft of stent. The clinical application of perivenous support, however, is hampered due to the fact that no easy applicable external support is available. Considering that application in the form of a spray is the most convenient modality, we evaluated whether polyethylene glycol is capable of providing adequate perivenous support. Polyethylene glycol is a synthetic, biodegradable product, used in cardiac surgery as a sealant, and is commercially available in the form of a spray. METHODS: Segments of human saphenous vein graft obtained during coronary artery bypass graft (CABG) procedures were placed in an ex vivo model, a side loop of the extracorporeal perfusion circuit, and perfused with autologous blood, making the circumstances identical to the implanted saphenous vein grafts concerning pressure, temperature, level of complement and leukocyte activation and blood pressure. Alternately around every other study vein graft segment polyethylene glycol was applied. Unsupported grafts served as control. After 1 min of solidification, perfusion was started with a pressure of about 60 mmHg (nonpulsatile flow). Perfusion was maintained for 60 min, after which the grafts were collected for light microscopy and electron microscopy. RESULTS: Light microscopy and electron microscopy showed remarkable attenuation of endothelial cell loss and less injury of smooth muscle cells of the circular and longitudinal layer of the media in the supported group compared to the nonsupported vein graft segments. CONCLUSION: Polyethylene glycol is able to provide adequate external vein graft support, preventing overdistension, in an ex vivo model. This provides a basis for clinical application. Further investigation is warranted to evaluate long-term effects.

Perivenous application of fibrin glue reduces early injury to the human saphenous vein graft wall in an ex vivo model.

OBJECTIVES: From animal and clinical studies it is known that prevention of 'over-distention' of vein grafts by using extravascular support ameliorates the arterialization process in vein grafts with subsequent more favorable patency. The most ideal support is a biodegradable, porous, elastic graft (Biomaterials, 15 (1994) 83). However, a specific graft meeting these criteria is not available yet. Fibrin glue on the other hand, although used for other purposes in cardiac surgery, theoretically meets the criteria for ideal extravascular support. In this ex vivo study, we evaluated the possible beneficial effect of perivenous application of fibrin glue. METHODS: Segments of human vein graft obtained during CABG procedures in 14 consecutive patients were placed in a side loop of the extracorporeal perfusion circuit. In this way the study vein grafts did meet identical circumstances as the vein grafts implanted. Perfusion in the loop was started with a flow just enough to counteract the collapse of the vein, usually about 8 mm Hg, and alternately around the segments fibrin glue was applied or no perivenous support was administered as control. After 1 min of soldification, perfusion was started with a pressure of about 60 mm Hg (non-pulsatile flow). Perfusion was maintained for 60 min, after which the grafts were collected for light microscopic and electron microscopic assessment. RESULTS: Light microscopy and electron microscopy showed remarkable attenuation of endothelial cell loss and less injury of smooth muscle cells of the circular muscle layer of the media in the fibrin glue supported vein grafts compared to the non-supported group. CONCLUSION: Fibrin glue is able to accomplish adequate external vein graft support, preventing overdistention, in an ex vivo model. This provides a basis for clinical application. Further investigation is necessary to evaluate long-term effects.

Perivenous support reduces early changes in human vein grafts: studies in whole blood perfused human vein segments.

BACKGROUND: Patency of vein grafts in coronary artery bypass grafting procedures is generally less favorable than those of selected arterial grafts. However, vein grafts still are needed in cardiac operations. It would be desirable to find measures to improve the patency of vein grafts next to antithrombotic regimens. Animal studies demonstrated that arterial pressure induces overdistention of the thin-walled vein grafts and that prevention of this overdistention with extravascular support ameliorates the arterialization process with, subsequently, more favorable patency. To evaluate whether perivenous stenting of the rather muscular human vein grafts is also beneficial, we designed an in vitro model to study the early effects of perivenous support in human vein grafts. METHODS: Seven paired segments of human vein graft obtained during coronary artery bypass grafting procedures were placed in a perfusion circuit and perfused simultaneously with autologous whole blood, with a pressure of 60 mm Hg (nonpulsatile flow). After 30 minutes of perfusion, one segment, and after 60 minutes of perfusion, the remaining segment were taken for histologic and immunohistochemical examination. In the next experiments 7 segments of human vein graft were placed in the circuit and supported with a polytetrafluoroethylene graft to prevent overdistention with 7 unstented segments as controls. RESULTS: In unsupported vein grafts perfused with autologous blood under a pressure of 60 mm Hg, a complete de-endothelialization was shown after 1 hour of perfusion. In the study vein grafts, with a perivenous polytetrafluoroethylene graft preventing overdistention (n = 7), the endothelium remained intact. Electron microscopic investigation of the media showed severe damage in the circular smooth muscle layer in the unstented group, whereas in the stented group almost no injury was found. CONCLUSION: In our in vitro closed-loop model, reproducible vessel wall changes were observed in all human vein graft specimens studied. The beneficial effect of perivenous support could also be established for the human greater saphenous vein, providing a basis for clinical application.

Cardiopulmonary bypass with modified fluid gelatin and heparin-coated circuits.

We have assessed the efficacy of cardiopulmonary bypass (CPB) using normal colloid oncotic pressure (COP) in a randomized, controlled study of 20 patients undergoing elective coronary artery surgery using heparin-coated circuits. For CPB, we used either crystalloid priming 1650 ml (n = 10) or colloid priming 1650 ml (2.4% modified fluid gelatin, n = 10). While COP did not change during bypass in the colloid group, a decline was observed in the crystalloid group (P = 0.005). By the end of bypass, the decrease in COP compared with baseline (delta COP) was 8.5 (S.D. 1.1) mm Hg in the crystalloid group compared with 1.5 (2.1) mm Hg in the colloid group (P = 0.0001). delta COP correlated positively with fluid balance during bypass (r2 = 0.41, P = 0.002). Similar increments in complement factors C3b/c and C4b/c, tumour necrosis factor-alpha and neutrophil elastase, but not endotoxins, were found in both groups as indicators of a systemic inflammatory response. A clinical performance score composed of fluid balance, postoperative duration of intubation and the difference between rectal temperature and skin temperature was more favourable in patients treated with colloid priming (P = 0.03). Median postoperative hospital stay was 7 (range 5-16) days in the crystalloid group compared with 5 (4-8) days in the colloid group (P = 0.016). Regression analysis indicated that CPB time, fluid balance during operation and postoperative PO2/FlO2 ratio were independent factors that predicted postoperative hospital stay. From these preliminary results we conclude that in the absence of endotoxaemia, use of a normal COP during CPB with modified fluid gelatin in heparin-coated circuits resulted in an improved postoperative course an a reduction in hospital stay.