**2.2 Intra-operative blood salvage**

The collection of blood shed from the wound is an integral part of CPB surgery. The procedure consists of two steps, namely, cardiotomy suction carried out during CPB with standard heparinisation and blood recuperation during normocoagulation.

#### **Cardiotomy suction**

The system is usually composed of two suction lines, two pumps and a cardiotomy reservoir with filters. Blood is retrieved not only from some heart and aorta sections, but also directly from the operative field which continually fills with blood coming from the open sternum and the mediastinum, and from around the cannulae connecting the circuit. The shed blood is aspirated and collected in the reservoir, passes through a filter and is returned via an oxygenator into the circulation. The patient can thus be re-infused with several litres of blood. However, during this process blood is exposed to air in the operative wound and to synthetic surfaces of tubing, which activates a non-specific inflammatory response including coagulation. Suction-produced mechanical stress results in damage to erythrocytes and contributes to haemolysis. An improvement could be achieved by processing shed mediastinal blood in an autotransfusion device that would separate viable erythrocytes from the rest of activated blood with cellular detritus, fat and vasoactive mediators. A good effect on pulmonary function and haemodynamics has been shown in patients receiving processed blood [26]. This technique, however, is not much used because of technical problems with processing large volumes of blood and the necessity of plasma and platelet substitution.

#### **Blood recuperation**

The processing of blood drained from the operative wound is carried out at the time the patient is not fully heparinised, i.e., before the beginning or after the end of extracorporeal perfusion. If, after the termination of perfusion, a large volume of blood with low HCT is left in the reservoir, its recuperation is advisable, particularly when problems with renal function are expected. A large reservoir blood volume can be avoided by inserting a haemofiltration coil in the CPB system. The approach, however, removes only water and low-molecular-weight substances.

From the clinical point of view, the patient always benefits from blood recuperation because no or only few blood products are necessary [27]. In terms of costs, the situation depends on the degree of bleeding. With current blood products prices on the one hand and the costs of a recuperation set on the other, the results are equal if at least two PRBC units are obtained. It means that recuperation is cost-effective in patients with excessive

levels. The efficiency of both plasmapheresis and thrombopheresis has been evaluated in many studies. Some have reported lower requirements for allogeneic blood transfusion [19, 20, 21] as well as lower post-operative blood losses [22]. A positive effect of pre-operative plasmapheresis has been demonstrated by low tendency to pathological fibrinolysis [23]. On the other hand, other authors described a low efficacy of pre-operative apheresis in cardiac surgery [24] and related it to the pre-operative administration of an anticoagulation and platelet anti-aggregation therapy. The patients who, before surgery, have received coumarin derivatives, heparin and non-steroidal anti-phlogistic drugs do not benefit from

The collection of blood shed from the wound is an integral part of CPB surgery. The procedure consists of two steps, namely, cardiotomy suction carried out during CPB with

The system is usually composed of two suction lines, two pumps and a cardiotomy reservoir with filters. Blood is retrieved not only from some heart and aorta sections, but also directly from the operative field which continually fills with blood coming from the open sternum and the mediastinum, and from around the cannulae connecting the circuit. The shed blood is aspirated and collected in the reservoir, passes through a filter and is returned via an oxygenator into the circulation. The patient can thus be re-infused with several litres of blood. However, during this process blood is exposed to air in the operative wound and to synthetic surfaces of tubing, which activates a non-specific inflammatory response including coagulation. Suction-produced mechanical stress results in damage to erythrocytes and contributes to haemolysis. An improvement could be achieved by processing shed mediastinal blood in an autotransfusion device that would separate viable erythrocytes from the rest of activated blood with cellular detritus, fat and vasoactive mediators. A good effect on pulmonary function and haemodynamics has been shown in patients receiving processed blood [26]. This technique, however, is not much used because of technical problems with processing large volumes of blood and the necessity of plasma

The processing of blood drained from the operative wound is carried out at the time the patient is not fully heparinised, i.e., before the beginning or after the end of extracorporeal perfusion. If, after the termination of perfusion, a large volume of blood with low HCT is left in the reservoir, its recuperation is advisable, particularly when problems with renal function are expected. A large reservoir blood volume can be avoided by inserting a haemofiltration coil in the CPB system. The approach, however, removes only water and

From the clinical point of view, the patient always benefits from blood recuperation because no or only few blood products are necessary [27]. In terms of costs, the situation depends on the degree of bleeding. With current blood products prices on the one hand and the costs of a recuperation set on the other, the results are equal if at least two PRBC units are obtained. It means that recuperation is cost-effective in patients with excessive

standard heparinisation and blood recuperation during normocoagulation.

plasmapheresis [25].

**Cardiotomy suction** 

and platelet substitution.

low-molecular-weight substances.

**Blood recuperation** 

**2.2 Intra-operative blood salvage** 

blood loss; the costs of both approaches are equal in patients with large blood loss and, in patients with low blood loss, recuperation comes at an increased cost to the institution [28]. This medico-economic analysis would be right on the assumption that transfusion of allogeneic PRBCs is as valuable as fresh autologous blood transfusion. The present-day evidence suggests that this is not true, although the major risks of allogeneic blood transfusion, such as infection or immunomodulation, are minimal. Packed red blood cells are more suitable for correcting severe chronic anaemia than for an acute large blood loss. Transfused banked erythrocytes are not capable of immediate oxygen release for tissue supply, and their accumulation in the pulmonary vascular bed may do acute damage to the lung tissue, causing right-sided pulmonary failure and paradoxically making circulatory shock worse. Nonetheless, for a patient with excessive blood loss, allogeneic blood transfusion is the only possible choice. Because of increasing awareness of these facts, blood recuperation is becoming a routine method in a growing number of centres for cardiac surgery and is currently used in about 50% and 60 % of these institutions in the EU and North America, respectively.

#### **2.3 Post-operative blood salvage**

The method of collection and re-infusion of mediastinal blood shed during surgery and drained in the early post-operative period has been used in cardiac surgery since 1978 [29]. The blood is collected into a special auto-transfusion device, or the cardiotomy reservoir of a CPB system can be used when it is connected to mediastinal drainage and a vacuum generator and with anti-coagulation citrate solution added. The cardiotomy reservoir involves a 40- filter, but insertion of an additional 20- filter in the outlet line is recommended. The salvaged blood has 20-25% HCT, a small number of platelets, free haemoglobin and no fibrinogen. It also contains fibrin-degradation products, cardiac enzymes and other inflammatory factors which may adversely affect biochemical tests and clinical outcomes [30, 31]. In spite of the disadvantages, this is a safe technique which can reduce demands for blood transfusion particularly in patients with blood loss exceeding 500 ml in the first two hours [32]. Doubts concerning the quality of salvaged erythrocytes were challenged by Schmidt et al. who did not find any differences in survival between the red blood cells of shed mediastinal blood and those of circulating blood [33]. At present the use of a recuperation technique for mediastinal blood is preferred because it reduces the organism's burden by free haemoglobin and inflammation mediators [34]. It is usually carried out in continuation of intra-operative recuperation and is regarded as a safe method up to 8 hours of the patient's transfer to an intensive care unit [35].

#### **3. Blood bank products**

A rational therapy with blood products and derivatives requires that their administration be based on a documented deficiency or dysfunction. However, surgical bleeding may be associated with additional haemostatic risk factors. A prolonged hypovolaemia with subsequent shock can initiate consumption coagulopathy and the substitution with crystalloids and colloids will result in clotting factor dilution. With the exception of patients with serious vascular disease or very old persons, the majority of patients can tolerate anaemia with a haemoglobin concentration of 7 g/dl or 24% HCT. However, in the early phase of circulatory and haemostatic homeostasis, it is advisable to increase Hb concentration to 8g/dl in order to spare the compensatory capacity of myocardium (increased cardiac output) and to utilise a possibility to regulate systemic blood pressure by blood viscosity. In patients with serious peripheral arterial disease, it is reasonable to increase the transfusion trigger. Transfusion should be administered only after the patient's medical history and their actual health status have been taken into consideration [36, 37].
