Introduction

Autologous blood transfusion has been reported to be less detrimental than allogenic blood. Methods for collecting and using autologous blood are many, for example, pre-deposition, peri-operative acute normovolaemic haemodilution (ANH), and intraoperative or postoperative cell salvage.

Cell salvage has been demonstrated to be safe and effective at reducing allogeneic blood transfusion requirements in adult elective surgery, with stronger evidence in cardiac and orthopaedic surgery [1]. Many earlier studies have highlighted the potential clinical advantages of cell salvage in decreasing the need for and risks associated with allogenic transfusion [2]. The cell saver is an established mechanical device to reduce blood wastage in cardiac surgery. The technology of cell salvage systems has progressively evolved since its inception in the 1960s.

Today, essentially all blood salvage practices use techniques that wash the scavenged blood, usually with normal saline (0.9% sodium chloride), and return a solution of red blood cells suspended in normal saline with a haematocrit of 50–70%. The Fresenius Continuous AutoTransfusion System (CATS®) device (Fresenius HemoCare Inc., Bad Homburg Germany) is currently the only cell salvage apparatus that uses a continuous technique, thereby allowing scavenged blood to be collected, washed, concentrated, and returned in an uninterrupted process [3].

Amongst all types of cardiac surgeries, off-pump coronary artery bypass grafting (OPCABG) not only significantly reduces the need for postoperative transfusion requirement (p < 0.05) but also has several other potential advantages over on pump coronary artery bypass grafting including less cost [4]. Still, it has been reported that the blood loss during OPCABG is approximately 500 ml intraoperatively. In our study, we used the cell saver (Fresenius C.A.T.S®plus Continuous Auto Transfusion System, Terumo Cardiovascular group U.S) to avoid loss of red blood cells (RBCs) to be shed away in waste and thus to prevent blood transfusions if required. We aimed to study the safety and overall effectiveness of autologous transfusion using cell saver processed blood in patients undergoing OPCABG and to evaluate any new findings in regard to the Indian context apart from the already established paradigms of transfusing cell saver blood in cardiac patients.

Material and methods

This was a 1-year-long randomized prospective study which included all consecutive patients undergoing off-pump coronary artery bypass grafting for coronary artery disease. We randomized the patients into two study groups. In group I, the cell saver (Fresenius C.A.T.S®plus Continuous Auto Transfusion System, Terumo Cardiovascular group U.S.) was used to salvage and auto transfuse shed blood from the time of incision. In group II, banked homologous packed red blood cells were used as the only blood replacement therapy.

The same surgeon and team operated all patients. All patients were first-time cardiac surgery patients undergoing isolated off-pump coronary artery bypass grafting, and their Aspirin® or Clopidogrel was discontinued at least 5 days preoperatively. All patients gave written consent according to the regulations of the science ethics committee. All patients had their baseline investigations done and were operated only when these were within the normal range. We excluded emergency surgeries, concomitant valvular/congenital surgeries and those patients with known acquired platelet/clotting disorders, renal disease or hepatic diseases.

The surgeries were performed under general anaesthesia via a median sternotomy, and cardiac positioning & stabilization was done with the Octopus suction device (Medtronics® Evolution AS, Minneapolis, Minnesota, USA). Standard anaesthesia techniques using midazolam, fentanyl, vecuronium and isoflurane were used for induction and maintenance.

After harvesting the internal mammary artery, anticoagulation was achieved using heparin (100 IU/kg) for a target ACT of more than 250 s. Besides the Octopus suction device, different manoeuvres were used to help expose the target vessels like deep pericardial stitch and intracoronary shunts. After completion of anastomoses, heparin reversal was achieved with intravenous protamine in a proportion of 1 mg/kg. Routinely, we used the left internal mammary artery and reversed saphenous vein as graft conduits. Occasionally, radial artery was used as free graft.

All the shed blood from the time of incision till skin closure was collected by a single lumen negative pressure suction cannula flushed with heparinised saline. It was collected in the reservoir of the cell saver. The collected blood was then subjected to washing and centrifugation. The processed red blood cells were collected in sterile blood bags and were auto-transfused to the patients in the operation theatre before they were shifted to the intensive care unit (ICU).

The indication for homologous banked blood transfusion was haemoglobin of less than 9 g/dl or haematocrit of less than 27%. This protocol was followed in both groups. Haemoglobin concentration, haematocrit and coagulation profile were measured preoperatively and on arrival in the ICU and on fourth postoperative day. Detailed postoperative records of mediastinal drainage, inotropic support, ventilation time, number of units of packed red blood cells (PRBC), platelets and fresh frozen plasma (FFP) transfusion, arrhythmia, mediastinitis, stroke, urine output, blood investigation parameters, chest X-ray and other progress notes were maintained.

The postoperative management in the ICU consisted in maintaining a good perfusion of organs and tissues. Mean arterial pressure was kept between 60 and 70 mmHg, and ionotropic support was provided as and when required.

The data was analysed using Statistical Package for Social Sciences (SPSS) version 15.0. Chi-square test and Independent samples’ test was used to compare the data. Within group, comparisons were made using chi-square test and paired t test. The confidence level of the study was kept at 95%, hence a ‘p’ value less than 0.05 indicated a statistically significant association.

Results

Out of 50 patients enrolled in this study, half were managed using autologous cell saver blood transfusion method and comprised group I (study group) whereas the remaining 25 (50%) patients were managed without the cell saver (group II-control group). Table 1 shows the demographic and anthropometric profile of the patients enrolled in the study whereas Table 2 shows the distribution of cases according to exposure to risk factors. Statistically, the two groups were equally matched in regards to risk factors as well as their laboratory profiles (Table 3).

Table 1 Demographic and anthropometric profile of the patients enrolled in two study groups
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Table 2 Distribution of cases according to exposure to risk factors
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Table 3 Comparison of preoperative haematological and biochemical parameters between two groups
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On the other hand, the postoperative haematological and biochemical parameters showed differences between the two groups, namely, for mean haemoglobin (Hb) and haematocrit (Hct) level, respectively, which were found to be significantly higher in group I as compared to group II (Table 4).

Table 4 Comparison of postoperative haematological and biochemical parameters between two groups
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As shown in Table 5, the use of a cell saver did not affect the length of the overall procedure as compared to the controls. The total collected cell saver volume ranged from 350 to 1600 with a mean value of 790.40 ± 376.47. The maximum number had cell saver volume more than 1000 ml (28%).

Table 5 Comparison of operative data
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Both the groups were comparable for mediastinal drainage with a mean value of 473.20 ± 219.03 ml in group I and 493.20 ± 229.03 in group II, respectively (Table 6). However, the mean ventilatory time in group I was 8:20 ± 2:00 (hh:mm) and significantly lower than that of group II (12:21 ± 7:29 hh:mm). Majority of cases in the former had ventilatory time ≤ 8 h (52%); however, in the latter group, 16 patients (64%) had ventilator time > 8 h. Statistically, these differences between two groups were also significant (p = 0.016).

Table 6 Different outcome parameters
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Table 7 shows the comparison of complications, side effects and final outcome between two groups. In group I, none of the cases required reintubation, none had renal failure, stroke, endocarditis or mediastinitis and none required resternotomy. Overall, one mortality was recorded in this group. In comparison, in group II, 1 (4%) required reintubation, 8(32%) had arrhythmia, 2 (8%) had renal failure and 1 had pneumonia. One mortality was seen in this group too.

Table 7 Comparison of complications, side effects and final outcome between two groups
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Thus, the results showed significant differences between two groups for the need of PRBC transfusion, ventilatory time and for postoperative Hb and haematocrit levels.

Discussion and conclusions

Cardiac surgical procedures carry the risk of considerable bleeding which is caused by the surgical wound itself and by heparin and protamine together with other causes such as hypothermia, anaemia, inflammation or drug effects (e.g. antiplatelet agents, low molecular weight heparins). Thus, blood transfusions are often needed but are also associated with complications like transfusion-associated immunomodulation, lung injury and circulatory overload resulting in decreased patient survival with an increasing number of transfusions. These problems are less with autologous blood transfusions in which shed blood is collected to a cell-saver, processed and returned back to the patient [5].

Amongst the 50 patients who underwent this study, 16 (64%) patients in the non-saver group and 4(16%) patients of cell saver group required homologous blood transfusion (HBT). Haemoglobin concentration fell significantly in both groups on the first postoperative day from preoperative values with no difference between groups. But on comparing the two groups with their postoperative day 1 parameters, the difference was found to be significant statistically (p < 0.05), for mean Hb and Hct levels which were found to be higher in group I (11.14 ± 1.35, 33.98 ± 4.20) as compared to that in group II (10.08 ± 1.60, 30.56 ± 5.01), showing that the requirement for HBT per patient was significantly reduced in the cell saver group. These results are in line with the studies by Damgaard [6] and others, who suggest that retransfusion of washed processed shed blood during OPCABG significantly reduces the requirement of homologous blood transfusion. Autotransfusion of washed red blood cells was not associated with excessive bleeding in the postoperative period. Overall, allogeneic and RBC transfusions were comparably reduced by one unit in the cell saver group versus the control group in their studies.

Earlier experiments with cell salvage demonstrated that autotransfusion was associated with increased bleeding and coagulopathy; however, in modern times, these problems have been addressed by modern cell salvage and washing systems, which effectively remove activated leukocytes, platelets, and inflammatory mediators from salvaged blood. This is partly due to the fact that when using mechanical cell salvage, the ‘activated’ plasma fraction of the shed blood is removed. This plasma fraction contains cytokines, leucocyte activation products, lipids and other proinflammatory mediators. In fact, the cell salvage device has also been used, for this reason, to process cardiotomy suction blood during cardiopulmonary bypass [7].

Thus, there has been a lot of debate over the effects of cell saver blood (and even cardiopulmonary bypass cardiotomy blood) having varied effects on coagulation parameters as well as the overall cost effectiveness of this technique. Vymazal and colleagues [5] showed that retransfusion of patient’s own blood from cardiopulmonary bypass as well as from cell saver have similar effects on coagulation, namely, increased fibrinolysis. Of note in this context, it is important to mention another finding of a study in which it was shown that although shed mediastinal blood has a substantially reduced haemostatic capacity; autotransfusion of an average of 350 mL did not affect the overall haemostatic capacity [8].

In the present study, the coagulation markers increased significantly on the first postoperative day but revealed no difference between two groups (p > 0.05), showing that in patients undergoing OPCABG, autotransfusion is not associated with any clinically significant coagulopathy with or without the use of cell saver.

Significant differences between two groups in regard to PRBC transfusion need (p = 0.001), ventilatory time (p = 0.016) and duration of ICU stay (p = 0.034) showed that the use of cell saver was cost effective as compared to the usage of homologous blood. Another major limitation in context of our native country in regard to blood donation is the relative unavailability of healthy donors and the social unwillingness wherein blood donation is considered detrimental to health. The need to arrange for donors also entails the necessity for arrangements to be made for their travel (often overnight long journeys), stay and food. For patients who are government aided for surgeries, arranging blood donors becomes a costly affair.

We would thus like to conclude that the use of cell salvage in OPCABG is a safe and effective method. It does involve costs; however, in the context of the risk of complications of regular blood transfusion and the costs of longer hospitalizations in the background of the problems of procuring donors, it is a viable technique and proves to be cost effective in the long run as opposed to similar studies.