for blood conservation, risk factors were analysed in 343 cardiac surgical ... red cell, plasma and platelet transfusions were 3.29 ± 0.4, 1.96 ± ...
131-
Factors influencing haemostasis and blood transfusion in cardiac surgery Bo Liu, Ali Belboul, Sture Larsson and Donald Roberts
Department of Thoracic and Cardiovascular Surgery,
Sahlgrenska University Hospital, Gothenburg
To find out the risk factors influencing perioperative bleeding and use of blood products in cardiac surgery so that appropriate intervent.ions 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, intraopera-
tive 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 geometric mean of postoperative bleeding in the entire series was 1085 ml and the mean packed red cell, plasma and platelet transfusions were 3.29 ± 0.4, 1.96 ± 0.39 and 0.21 ± 0.05 units respectively. 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.
Introduction
Despite improvements in surgical and bloodsaving techniques, perioperative bleeding following cardiopulmonary bypass (CPB) is still a maAddress for correspondence: Bo Liu, Department of Thoracic and Cardiovascular Surgery, Sahlgrenska University Hospital, University of Gothenburg, S-413 45 Gothenburg, Sweden.
jor concern for cardiac surgeons. Excessive bleeding is associated with increased revision rate, homologous blood transfusion and hospital costs. Blood conservation has now
become an of major interest for the cardiac surgeon. This increased concern is caused by infectious complications of blood transfusion, in particular those due to hepatitis and, more recently, acarea
quired immunodeficiency syndrome (AIDS).
132 ’ ’
Among many other efforts to reduce postoperative bleeding and the need for homologous blood transfusion, use of the antiproteinase inhibitor aprotinin during the operation has shown to be significantly effective in previous studies.l-3 Unfortunately, the use of aprotinin is expensive and carries a low risk of allergic reaction and a potential risk for renal failure and graft occlusion in coronary artery bypass graft (CABG) surgery. Even though there is no definite evidence to confirm the latter two potential side-effects, many surgeons prefer to use aprotinin in those patients with a higher risk for bleeding and blood transfusion. Therefore, the identification of these risk factors becomes interesting from a therapeutic point of view. The aim of this study was to find out the pattern and risk factors for perioperative bleeding and homologous blood transfusion in cardiac patients undergoing CPB in our institute. Since a wide variation in perioperative bleeding and blood transfusion have been reported by different centres, our analysis could be used as a reference by other future studies on blood conservation. Risk factor analysis might be helpful for the surgeon in selecting patients for aprotinin therapy or other types of interventions.
Table 1
the first three months of 1994, 359 underwent cardiac surgery with CPB in our clinic. After excluding those patients who had heart and/or lung transplantation and high-dose aprotinin treatment, 343 patients were reviewed retrospectively in this study. The data collected and abbreviations are described in the appendix. The perioperative data are shown in Table 1.
During patients
General
surgical principles Aspirin was discontinued
one
week before
surgery in all of the elective
patients. Anticoagstopped three to four days before the operation in the elective patients. Standard premediation, anaesthesia and extracorporeal circulation (ECC) with membrane oxygenators were used in all patients. Intraoperative anticoagulation was achieved by giving 3 mg/kg heparin and additional heparin was added to maintain an activated clotting time (ACT) of more than 480 seconds during CPB. Heparin was neutralized by giving protamine chloride at the end of the operation at a ratio of 1:1. In the presence of inadequate haemostasis at the end of the operation and early ICU, additional protamine was given if the ACT was still more than 130 seconds. Postoperative monitoring ulants
were
Perioperative data
Group I: CABG; Group 11: valve; Group III: CABG appendix.
the
Patients and methods
+
valve; Group IV: miscellaneous. Other abbreviations
are
described in
133 of the
coagulation
routinely done suspected. including revision for patients with persistent
status was not
except when abnormal bleeding
was
Appropriate measures, bleeding, were taken in bleeding. Intraoperative retransfusion
of remaining blood in the oxygenator and ECC circuit, and postoperative autotransfusion of shed mediasti- ~ nal blood up to 12 hours postoperatively were used as routine blood-saving procedures. There was no other on-going blood conservation programme and no major surgical policy change during this period. The indications for homologous blood transfusions during the operation were haemodynamic instability (MAP 42
acute cases or
seconds) received
and most of them anticoagulants pre-
operatively.
Table 3
Perioperative bleeding non-revision patients
and blood transfusion in
The mean volumes of intraoperative bleeding and blood transfusion are shown in Table 7. The
Multiple regression analysis of preoperative factors for postoperative bleeding and blood transfusion
Code values for category variables: male: 1, female: 0; operation group 1: 0, II: 1, III: 2 and IV: 3; emergency: 1, elective: 0.
Table 4
Multiple regression analysis of intraoperative factors for postoperative bleeding and blood transfusion
Code values for category variable: with IMA
graft: 1, without
IMA
graft:
0.
136 lowest bleeding and transfusion volumes were noted in Group I and the highest in Group IV. They were also significantly higher in Group III when compared to Group I. The mean volumes of postoperative bleeding Table 5
and blood transfusion are also shown in Table 7. Bleeding, both at 12 hours and at drainage removal (total), were similar in all groups. About half of the total blood loss was re-transfused back to the patients by autotransfusion in the first
Incidence of blood transfusions in relation to treatment
periods in the groups
< 0.05, bp < 0.01, ~p < 0.001 when compared to CABG (Group I). Group I: CABG; Group li: valve; Group III: CABG + valve; Group IV: miscellaneous. Other abbreviations the appendix.
ap
Table 6
Incidence of blood transfusion in relation to
*With Fisher’s exact test p 0.0309. 11: valve; Group III: CABG
perioperative factors
=
Group I: CABG; Group
+
valve; Group IV: miscellaneous.
Figure 1 Mean haemoglobin changes. The postoperative reductions significant in all the groups. Group I: CABG; Group 11: valve; Group III: CABG with valve; Group IV: miscellaneous.
were
are
described in
137
Figure
2
changes in platelet counts (x 109/I). The postoperative significant in all the groups with the least decline in Group I: CABG; Group 11: valve; Group III: CABG with valve;
reductions
Mean
were
Group I. Group IV: miscellaneous. Table 7
Perioperative bleeding (ml) and blood transfusion (ml) in nonrevision patients
ap < 0.05, bp < 0.01, ~p < 0.001, dp < 0.0001 when compared to CABG (Group I). Group I: CABG; Group 11: valve; Group III: CABG + valve; Group IV: miscellaneous. Other abbreviations the appendix.
three groups, but only one-third of the total was re-transfused in Group IV. Blood transfusions were similar in Groups I and II, but were significantly more in Groups III and IV when compared to Group I. In addition to blood product transfusion, volume replacement by dextran 70 (Macrodex@, was similar in all groups with a mean volume of 276 ml for the entire subset of non-revision patients.
bleeding
are
described in
The mean units of blood transfusion during hospital stay in nonrevision patients was 2.851 t 0.452. The respective values for Groups I-IV were 1.569 t 0.228, 2.333 t 0.380, 6.184 t 1.441 and 13.562 t 6.820. It was significantly higher in Groups III and IV when compared to Group I. The proportions are shown in Figure 3. In Groups I and II, packed red cells were the main blood products transfused. In contrast, there
138
3 Total blood transfusion units and their proportions in nonrevision patients. Group I: CABG; Group li: valve; Group III: CABG with valve; Group IV: miscellaneous. d p < 0.0001 when compared to group I.
Figure
=
Table 8
Perioperative data for transfused and nontransfused patients in nonrevision group
aTotal volumes of blood transfusion up to the end of ICU stay. bGeometric means and Mann-Whitney U test. Abbreviations are described in the appendix.
plasma and thrombocyte transfusions III and IV, particularly in Group IV. The factors related to transfusion are analysed in Table 8. There were 168 patients who received some form of blood products (54.5%) and 140 who did not receive any such products during hospital stay. The total transfused volume, including autotransfusion in the transfused were more
in
Groups
was 1829 ml, which is higher than their total volume of blood loss (1781 ml) while in the non-transfused patients the autotransfusion only replaced 41% of the total blood loss. Aorta clamp time, CPB time and operation time were significantly longer in the transfused patients (p 0.0002). Other data are shown in Table 8.
patients,
=
139
Effect of IMA graft Patients in Group I undergoing elective surgery and who were not revised for bleeding were included in the analysis below. Patients treated preoperatively with anticoagulants were excluded from the analysis. The perioperative blood loss and transfusion requirements are shown in Table 9. Multiple regression (Table 4), including all patients in Groups I and III, showed that the use of IMA graft theoretically increased postoperative bleeding by about 300 ml when compared to patients without IMA graft. On the other hand, it did not increase homologous blood transfusion.
Discussion Increased morbidity and mortality, increased hospital expenses and increased transmission risk of infectious disease associated with excessive perioperative bleeding and homologous blood transfusion have stimulated studies to examine various methods of blood conservation in cardiac surgery. Since perioperative blood loss and transfusion vary considerably from centre to centre and, in addition, can be affected by many factors, it is difficult to compare the efficacies of various interventions in different centres. Furthermore, most interventions carry some side-effects. Therefore, it is important for the cardiac surgeon to be aware of these risks to the patients and to select appropriate interventions for perioperative bleeding and homologous blood transfusion. The Table 9
Effect of IMA
graft
on
blood loss and transfusions
NS: not significant. Abbreviations are described in the
appendix.
difference between cardiac surgery and other surgery is the use of cardiopulmonary bypass (CPB) which leads to activation of the systemic inflammatory response,44 including activation of coagulation, fibrinolysis, complement system and platelet damage. Therefore, the cardiac surgeon is required to take time and care to ensure that the wounds are adequately dry before the chest is closed. In spite of this, blood loss, revision for bleeding and use of homologous blood products have not been fully controlled. The reason is multifactorial and several factors, such as preoperative aspirin and warfarin treatment, emergency surgery, liver disease and preexisting coagulation defects, have been shown to be related to this problem. 5-7 The overall revision rate in our series was 10.2% which is higher than those in other reports8,9 and our own annual revision rate (6.8% ) in the same year (unpublished data). This might be due to the high volume of operations and relatively large proportion of acute aortic aneurysms in our series. The revision rate in CABG surgery was 7.6%, which is lower than that reported by Parolari et al.1° and higher than that of Breyer et al.ll Although local active bleeding was found in 30 of 35 revision patients, we suspect that probably there was some coexisting disturbance in coagulation functions in those patients due to the simultaneous presence of diffuse bleeding. Furthermore, during revision, the need to check the entire wound for bleeding with the help of wound irrigation and clot removal might re-start local bleeding. This can be further sup-
major
140
the fact that blood loss after revision almost twice as high as in nonrevision
ported by was
patients. This study revealed that complicated procedures (Groups III and IV) requiring longer CPB times bled more and received more blood products during and after surgery. In addition to increase packed red cells transfusions, plasma and thrombocyte transfusions were particularly high in those two groups, indicating that they required more replacement of coagulation factors which could be related to prolonged CPB times and relatively more complicated surgery. This has been observed by other authors.12 Regarding Group IV of this study, acute aneurysm or VSD operations have longer CPB times and, therefore, influence the group’s risk profile. Heterogeneous groups like Group IV of this study should be avoided in future. The observation by Parolari et awl.10 that CABG patients carried a higher risk for postoperative bleeding when compared to valve surgery patients was not confirmed in this study. In contrast, CABG patients had the least amount of perioperative bleeding and blood transfusion. Male gender became a risk factor for postoperative bleeding and blood transfusion. This might be related to increased body weight and, therefore, a proportionally larger wound size, which would increase the surface area for bleeding. Male gender also was found to be a risk factor in Parolari’s study and was explained as uneven distribution.l° On the other hand, female gender had a higher incidence of blood transfusion, which is probably related to the increased surgical risk associated with female patients.13,14 Increased incidence of blood transfusion in women was also observed by Breyer et al.’1 and, therefore, further studies are awaited before making any conclusion on the effect of gender. Higgins score was the risk factor both for postoperative bleeding and blood transfusions, while preoperative ejection fraction (EF), New York Heart Association (NYHA) class and Canadian Cardiac Society (CCS) class were not predictive for bleeding and blood transfusion. Higgins scoring system includes several factors (raised serum creatinine, prior vascular surgery, anaemia, chronic obstructive pulmonary disease on medication) which are absent in the Parsonnet scoring system and these factors probably influence
patients’ postoperative haemostasis and blood product requirements. Other significant preoperative variables for red blood cell transfusions were preoperative haemoglobin, whose influence was inversely related, and emergency for total blood transfusion. We had a large proportion of aortic aneurysms and failed percutaneous transluminal coronary angioplasty (PTCA) (usually on aspirin at the time of surgery) in our emergency surgery. Both of these types of patients are known to bleed more and require transfusions,7 especially plasma and thrombocyte transfusions. Intraoperative volume of blood loss and duration of CPB showed a positive relationship with postoperative bleeding and blood transfusion. We know that intraoperative bleeding is associated with disturbances in the coagulation system during surgery. Activation of platelets, the coagulation system, fibrinolysis and occurrence of blood cell trauma associated with longer CPB time6,11,16 increase the risk for postoperative bleeding and total transfusion products which is a known observation from other reports.10,12 Redo-surgery, usually considered a high risk in the literature,1,9 did not significantly increase blood loss or transfusions in our series and did not enter the risk analysis model. This is probably due to the small number of redo-surgery patients in our series. As regards dicoumoral anticoagulants, this therapy was routinely stopped three to four days before surgery, the discontinuation obviating the risk for bleeding in the multiple regression analysis. However, the frequency of blood product usage was significantly raised in these patients. Postoperative reductions in haemoglobin and platelet counts are common phenomena following the use of CPB. These changes could be related to blood trauma 16 and the activation of many blood factors, 4,11,18 together with blood loss. The reduction in haemoglobin causing anaemia on day two postoperatively is most often due to continuous red cell destruction following initial mechanical trauma during CPB and may necessitate blood transfusions. Thrombocytopenia was observed in Groups II, III and IV postoperatively due to haemodilution, intraoperative consumption and heparin Although the reductions in platelet counts appeared significant, their decline
141 alone is usually not severe enough to produce abnormal haemostasis9 However, platelet dysfunction rather than thrombocytopenia may have been related to postoperative bleeding.20,21 Forty-five per cent of the nonrevision patients were managed without any homologous blood transfusions. In these nontransfused patients, volumes of blood loss were 44% less during and 20% less after the operation when compared to transfused patients and with simultaneous reductions in autotransfusion volumes. Of particular interest in the transfused patients is the fact that the total volume of transfusions (including autotransfusion) was in excess of the total blood loss, whereas the total transfusion volume (only autotransfusion) in the nontransfused patients was less than half of the total blood loss. This could be interpreted as a tendency to overcompensation by using blood products to maintain adequate circulatory volume. However, 33% of the blood products in the transfused patients consisted of plasma and platelet-rich plasma, usually given to control suspected disturbances in coagulation. In the remaining 67%, packed red cell transfusions were given mainly to correct the reduction in haemoglobin (anaemia). Our further analysis showed that the increased use of blood transfusions might be related to surgical risks as expressed by Higgins scores. In fact, the haemoglobin reduction on postoperative day two was significantly greater in the nontransfused patients, suggesting that haemoglobin reduction was not the only cause for transfusion, but that transfusion might have been given to high-risk patients who had a longer respirator time and longer ICU stay related to some temporary haemodynamic instability. Furthermore, the possibility of some unnecessary blood transfusion or over-transfusion could not be ruled out in the transfused patients, particularly regarding the use of packed red cell transfusion. Therefore, stricter criteria for postoperative transfusion therapy following cardiac surgery needs to be established, based on proper objective scientific data. Harvesting IMA grafts, in general, is considered as a risk for increased postoperative bleeding and blood product requirements. Its influence on intraoperative and postoperative bleeding was confirmed in our study. Use of IMA grafts was also confirmed as a risk factor for increasing the
volume of
postoperative bleeding when multiple regression analysis was used. However, homologous blood transfusions were not increased with the use of IMA graft, probably as a result of effective autotransfusion. In contrast, increased incidence of blood transfusion was observed in non-IMA patients by Breyer et as and no explanation was given. The small number of nonIMA patients in our material made group comparison unbalanced because CABG surgery without IMA graft is not a common practice nowadays. The modest increase in bleeding following IMA harvesting seems to have little clinical significance. In summary, perioperative blood loss and transfusion are still problems in cardiac surgery in spite of the improvement in surgical and ECC techniques today. Certain patient groups in this study were shown to be high risk for these problems. The preoperative factors that increased the risk for this were emergency operation, male gen-
der, operation procedures, high Higgins
score
and anaemia. The
intraoperative factors were intraoperative bleeding, use of IMA graft, CPB time and operation time. Better understanding of the coagulation changes on the various patient groups and how they may be adequately controlled perioperatively is still required and appears to be a daunting task. In the meantime, application of available blood conservation techniques may have to be used routinely or selectively in cardiac surgery and the administration of aprotinin is recommended in high-risk patients. Acknowledgement This study was partly supported by a grant from the Swedish Heart and Lung Foundation project No. 55022. References 1
Royston D, Bidstrup BP, Taylor KM, Sapsford RD. Effect of aprotinin on need for blood transfusion after repeat open-heart surgery. Lancet 1987; 2: 1289-91. 2 Liu B, Belboul A, Al-Khaja N, Dernevik L, Roberts D, William-Olsson G. High-dose aprotinin (Trasylol) in reducing bleeding and protecting lung function in potential bleeders undergoing cardiopulmonary bypass. Chin Med J 1991; 104: 980-85.
142 et al. Effect of 3 Liu B, Belboul A, Rådberg G reduced aprotinin dosage on blood loss and use of blood products in patients undergoing cardiopulmonary bypass. Scand J Thor Cardiovasc Surg 1993; 27: 149-55. 4 Kirklin JK, Westaby S, Blackstone EH, Kirklin JW, Chenoweth DE, Pacifico AD. Complement and the damaging effects of cardiac surgery. J Thorac Cardiovasc Surg 1983; 86: 845-57. 5 Khuri SF, Michelson AD, Valeri CR. Effects of cardiopulmonary bypass on hemostasis. In: Loscalzo J, Schafer AI eds. Thrombosis and hemorhage. Boston: Blackwell Scientific Publications, 1994: 1051-73. 6 Taylor KM. Perioperative approaches to coagulation defects. Ann Thorac Surg 1993; 56: S78-82. 7 van Breda A. Thrombolysis in arterial bypass grafts. Semin Thromb Hemost 1991; 17: 7-13. 8 Michelson EL, Torosian M, Morganroth J, MacVaugh III H. Early recognition of surgical correctable causes of excessive mediastinal bleeding after coronary artery bypass graft surgery. Am J Surg 1980; 139: 313-17. 9 Halfman-Franey M, Berg DE. Recognition and management of bleeding following cardiac surgery. Crit Care Nurs Clin North Am 1991; 3: 675-89. et al. The effect 10 Parolari A, Antona C, Gerometta P of ’high dose’ aprotinin and other factors on bleeding and revisions for bleeding in adult coronary and valve operations: an analysis of 2190 patients during a five-year period (1987-1991). Eur J Cardiothorac Surg 1995; 9: 77-82. 11 Breyer RH, Engelman RM, Rousou JA, Lemeshow S. Blood conservation for myocardial revascularization : Is it cost effective? J Thorac Cardiovasc Surg 93: 512-22. 1987; 12 Khuri SF, Wolfe JA, Josa M et al. Hematologic changes during and following cardiopulmonary bypass and their relationship to the bleeding time and non-surgical blood loss. J Thorac Cardiovasc Surg 1992; 104: 94-107. 13 Higgins TL, Estafanous FG, Loop FD, Beck GJ, Blum JM, Paranandi L. Stratification of morbidity and mortality outcome by preoperative risk factors in coronary artery bypass patients. JAMA 1992; 267: 2344-48. 14 Parsonnet V, Dean D, Bernstein AD. A method of uniform stratification of risk for evaluating the results of surgery in acquired adult heart disease. Circulation 1989; 79: I3-I12. 15 Dechavanne M, Ffrench M, Pages J et al. Significant reduction in the binding of a monoclonal antibody (LYP 18) directed against the IIb/IIIa glycoproteincomplex to platelets of patients who have undergone extracorporeal circulation. Thromb Haemost 1987; 57: 106-109. 16 Hirayama T, Roberts DG, Allers M, Belboul A, AlKhaja N, William-Olsson G. Association between
bleeding and reduced red cell deformability following cardiopulmonary bypass. Scand J Thor Cardiovasc Surg 1988; 22: 171-74. 17 Edmunds LH, Colman RW, Niewiarowski S. Blood-surface interaction during cardiopulmonary bypass. In: Friedel N, Hetzer R, Royston D eds. Blood use in cardiac surgery. New York: SpringerVerlag, Darmstadt: Steinkopff Verlag, 1991: 27-32. 18 Michelson AD. Pathomechanism of defective hemostasis during and after extracorporeal circulation : The role of platelets. In: Friedel N, Hetzer R, Royston D eds. Blood use in cardiac surgery. New York: Springer-Verlag, Darmstadt: Steinkopff Verlag, 1991: 16-26. 19 Harker LA, Malpass TW, Branson HE, Hessel II EA, Slichter SJ. Mechanism of abnormal bleeding in
patients undergoing cardiopulmonary bypass: Acquired transient platelet dysfunction associated with selective alpha-granule release. Blood 1980; 56: 824-34. 20 Tabuchi N, De Haan J, Boonstra PW, Gallanda Huet RCG, van Oeveren W. Aprotinin effect on platelet function and clotting during cardiopulmonary bypass. Eur J Cardiothorac Surg 1994; 8: 87-90. 21 van Oeveren W, Harder MP, Roozendaal KJ, Eijsman L, Wildevuur CR. Aprotinin protects platelets against the initial effect of cardiopulmonary bypass. J Thorac Cardiovasc Surg 1990; 99: 788-96.
Data collection and abbreviations
Appendix:
Preoperative Age: Gender: EF:
BW: FC:
variables: Years at the operation date. Male or female. Percentage of ejection fraction, estimated by cardioangiography or echocardiogram. If both were available, estimation by angiography was used.
Preoperative bodyweight (kg). New
York
classification AC:
Higgins:
Heart
Association
(NYHA) I, II, III,
IV. Canadian Cardiac Society classification (CCS) I, II, III, IV. Higgins score. Factor(s) of 6 points is emergency; 4 points: creatinine > 168 pmol/l; 3 points: severe left ventricular dysfunction, reoperation and operative mitral valve insufficiency; 2 points: ages
143
Acute:
Anticoag:
75 years, prior vascular surgery, chronic obstructive pulmonary disease and anaemia; 1 point: creasinine > 141 and < 167 pmol/I, ages 65 and < 74 years, operative aortic valve stenosis, weight < 65 kg, diabetes and cerebrovascular disease.
Postoperative
Emergency operation, performed
Bldl2:
HB:
PLT:
PTc:
aPTT:
variables: Volume of
mediastinal
shed
at 12 hours from
for
the end of surgery or end of revision if patient was re-operated for
operation. Anticoagulant agents (warfarin or dicoumoral) used between date of decision and surgery, usually it was discontinued three days prior with sternotomy. Earlier cardiac operation with thoracotomy was not included. Blood haemoglobin (g/1). Prefixes Pre- Dl- and D2- represent the values before haemoglobin one and two days afsurgery, day ter the surgery, respectively. The reference ranges at our hospital were 132-166 g/1 for men and 116-149 g/1 for women. Platelet counts x 109/1. Prefixes are the same as in HB. Our reference range was 150-350 x 109/1 for adults. Prothrombin complex, relative activity (%) to reference plasma. The reference range was 70130% for adults at our hospital. Activated partial thromboplastin time (seconds). The reference range was 30-42 seconds for adults.
Formerly
heart
variables: Aorta crossclamp time (minutes) CPB time (minutes) Operation time (minutes)
Number of moses,
peripheral anastoincluding IMA graft.
With internal mammary artery
(IMA) graft. Without internal mammary artery
(IMA) graft.
bleeding. BldT: T.
bleeding:
operated
AC time: CPB time: Op. time: Graft no:
-IMA:
Intraoperative bleeding (ml), estimated by blood volume in the swabs added to the intraoperative drainage in excess of fluid used for wound irrigation and/or topical cooling.
drainage (ml)
Intraoperative
+IMA:
Bld:
within 24 hours after the decision
to elective surgery.
Redo:
Op.
Same as Bldl2 (ml), but up to the removal of the drains. BldT added to the volume of mediastinal drain from the end of surgery to time of revision if patients was re-operated on for
bleeding. AT:
Autotransfusion, volume of postautotransfusion of mediastinal shed drainage (ml). Re-operated for excessive bleed-
operative Revision: Res. time:
ing. Respirator time (hours), from the end of operation to the time of extubation.
Transfusion of homologous blood products Packed red cell transfusion. PrePRC: fixes Prim, ECC, Op and ICU represent the volume of packed red cells in the priming volume, during ECC, operation and ICU respectively and U.PRC represents the mean total units of PRC used during the hospital stay. One unit of PRC is equal to 290 ml, on average. Plasma: Plasma or fresh frozen plasma transfusion. Prefixes as in PRC. One unit of plasma transfusion is equal to 230 ml, on average. PLT: Platelet-rich plasma transfusion. Prefixes as in PRC. One unit of
platelet-rich plasma usually comes from six blood donors. One unit of PLT is equal to 350 ml, on average.
