ISSN : 1301-5680
e-ISSN : 2149-8156
Turkish Journal of Thoracic and Cardiovascular Surgery     
Preoperative anemia in cardiovascular surgery patients
Sevil Özkan1, Mehmet Kaplan2, Özlem Tarçın1, Hatice Betül Erer3, Ahmet Yavuz Balcı2, İbrahim Yekeler2
1Departments of Internal Medicine, Siyami Ersek Thoracic and Cardiovascular Surgery Training and Research Hospital, İstanbul
2Departments of Cardiovascular Surgery, Siyami Ersek Thoracic and Cardiovascular Surgery Training and Research Hospital, İstanbul
3Departments of Cardiology, Siyami Ersek Thoracic and Cardiovascular Surgery Training and Research Hospital, İstanbul


Anemia is the most commonly encountered hematological condition during the preoperative evaluation of the cardiovascular surgery patients. Preoperative anemia is associated with an increase in morbidity and mortality in patients who undergo cardiac surgery. In addition, it is the most important determinant of perioperative blood transfusion, with its many risks and side effects. Therefore, determining and treating the reason of preoperative anemia may resolve post-surgical untoward results. Future studies are warranted to determine whether the treatment for anemia administrated before the cardiovascular surgery will resolve postoperative untoward results.

Coronary artery bypass grafting (CABG) and valvular surgery are among the most commonly performed cardiac operations. Anemia is the most commonly encountered hematological problem during the preoperative evaluation of these patients.[1]

Anemia is the presence of a decrease in the oxygen transport capacity of the blood. As this is a function of the volume of total red blood cells present in the circulation, anemia may also be defined as a decrease in the volume of red blood cells (Erythrocytes). While the measurement of chrome-labeled erythrocytes is the most accurate method to determine the volume of erythrocytes, due to its unpractical nature, hematocrit (Hct) and hemoglobin (Hb) values are used for clinical evaluation. However, it should be noted that when evaluating anemia, Hct and Hb values could be influenced by plasma volume.[2]

For patients undergoing cardiac surgery, the presence of preoperative anemia is associated with an increase of morbidity and mortality and appears as a finding of secondary disease.[3,4] Preoperative anemia is the most important determinant of perioperative blood transfusion that has many risks and side effects,[5] making it important to determine and treat the cause of preoperative anemia.[3] In the study performed by Karski et al.,[6] the reasons of anemia in patients who underwent cardiovascular surgery (CVS) include hospital-induced anemia (37.3%), iron deficiency anemia (29.3%), anemia related to chronic renal failure (10.7%), anemia of chronic disease, folate deficiency and thalassemia. Hospital-induced anemia was diagnosed when the hemoglobin drop was 9 g/L or more between admission to hospital and surgery and hemoglobin on the day of surgery was ≤120 g/L. Possible explanations are blood sampling while in the hospital and blood losses during coronary angiography.

For patients undergoing cardiovascular surgery, the first step of the evaluation for preoperative anemia should be the medical history and physical examination. When taking the medical history, bleeding symptoms such as menstruation, melena, hematemesis, hemoptysis and hematuria should be cautiously examined. Fatigue, dyspnea, tachycardia and angina, which are compensatory responses of the body and the symptoms associated with anemia, are among the most important findings. Constitutional symptoms of diseases associated with anemia, such as malignancy, renal failure, endocrine diseases, infections and hepatic disease should be observed.

In the medical background of the patient with anemia, previous levels of Hb, treatments for anemia, the presence of blood transfusions and history of splenectomy are important. In the familial history of the patient, bleeding, the presence of hematological diseases, splenectomy and cholelithiasis with early onset should be questioned. The job of the patient, his/her alcohol consumption and all the drugs that he/she uses, including herbal ones, should be examined.

During the physical examination, most commonly seen signs are pallor of skin and mucous membranes, jaundice, findings of bleeding, petechia, purpura, hepatosplenomegaly and lymphadenopathy. Murmurs are frequently observed during the cardiac examination. To determine the source of bleeding, the gastrointestinal system (GIS) should be frequently evaluated.[3]

The laboratory tests performed at baseline are full blood count, peripheral smear examination and reticulocyte count. To evaluate blood loss occurring in the GIS, gaita should be examined and radiological and endoscopic evaluation should be performed. Reticulocyte counts show the erythrocyte production of bone marrow. However, reticulocyte counts should be adjusted by erythropoietin effect in bone marrow and differences seen in Hct. This is calculated by using the reticulocyte production index (RPI). The reticulocyte production index can be calculated as described below:

RPI=(Reticulocyte count x Htc of the patient) / (normal Htc x 1 / adjustment of maturation)

The cases with a RPI below two show the presence of hypeproliferative anemia or a decrease in the response given by bone marrow to anemia (Table 1). In next step, anemia is classified as microcytic, normocytic and macrocytic according to mean corpuscular volume (MCV) measured during the full blood count.

Table 1: Hemotocrit associated with maturation

Iron deficiency anemia and thalassemia are the most common causes of microcytic anemia. As laboratory tests for microcytic anemia, serum iron, total ironbinding capacity and ferritin levels are first determined. These tests will be followed by bone marrow biopsy and hemoglobin electrophoresis. In normocytic anemia, acute blood loss should be excluded. Other causes of normocytic anemia include hepatic and renal diseases, iron deficiency anemia and early period of vitamin B12, folate deficiency, dysmorphic anemia, myelodisplastic anemia, aplastic anemia and chronic disease resulting from inflammatory diseases.

For the diagnosis of normocytic anemia, tests for hepatic and renal function and bone marrow biopsy are performed in addition to tests used for the diagnosis of microcytic anemia mentioned above. Macrocytic anemia is classified as megaloblastic and non-megaloblastic anemia. The causes of megaloblastic anemia are deficiency of vitamin B12, folic acid, drugs (anticonvulsants, chemotherapy agents) and myelodysplasia. The causes of non-megaloblastic anemia are alcohol, hepatic diseases and hypothyroidism. Laboratory tests done at baseline are tests for vitamin B12 and folic acid. Further tests include liver function tests and bone marrow biopsy.

The cases with a RPI above two may show an increased response of bone marrow to acute blood loss or hemolysis. As laboratory tests, direct and indirect bilirubin, lactate dehydrogenase level, haptoglobin level and direct and indirect Coombs test should be requested.

Peripheral blood smears may provide important clues about underlying disease. Polychromatosis and basophilic stippling are seen in hemolytic anemia; systotitis is seen in microangiopathic hemolytic anemia and spherocytes are seen in hereditary spherocytosis, autoimmun hemolytic anemia and microangiopathic hemolytic anemia.[3]

The results of preoperative anemia in CVS patients have been investigated in some studies. In the study performed by Zindrou et al.,[7] which compared 62 patients with anemia (Hb ≤10 g/dl) and 2075 patients without anemia (Hb >10 g/dl), patients with anemia showed a three-fold increase in nosocomial deaths.

In the study performed by Cladellas et al.,[8] 42 patients with anemia (Hb ≤12 g/dl) and 159 patients without anemia (Hb >12 g/dl) were compared in terms of nosocomial mortality and morbidity. For the patients with anemia, it was determined that rates of death increased by three-fold and major complications increased by five-fold. In the study performed by Kulier et al.,[4] in 4804 patients with preoperative anemia, a strong correlation was found between cardiac and non-cardiac (cerebral, renal, gastrointestinal etc.) complications. For the hemoglobin concentrations, each decrease by 1 g/dl below 14 g/dl led to an increase in non-cardiac adverse events by 15%.[4]

In the study performed by Carson et al.,[9] it was shown that risk for mortality was increased in patients with a preoperative hemoglobin level below 11 g/dl and that 30-day mortality was 33% in patients with a hemoglobin level below 6 g/dl. In an investigation performed on 1958 patients who underwent CABG, it was observed that 30-day mortality was 33.3% in patients with a preoperative Hb level of 6 g/dl and 1.3% in patients with a preoperative Hb level of 12 g/dl. In numerous clinical studies,[10-12] it was found that during the cardiopulmonary bypass (CPB) period, serious anemia and low oxygen distribution were associated with increased risks for renal failure, stroke and death. Low Hb levels are the independent determinant of both comorbidity and shortand long-term mortality. Low preoperative Hb level is a risk factor for early and late mortality.

Compared to the general population, patients with preoperative anemia showed a worse survival than was expected.[13] For patients with preoperative anemia who underwent CABG, the reason of the low long-term survival rates was not well defined. These patients are more sensitive to anemia because increased heart rate and beat volume, which are compensatory responses occurring secondary to anemia, are restricted.[14] This restricted compensatory response leads to tissue hypoxia, cellular deficiency, organ dysfunction and failure.[15] All these causes result in an increase of mortality during the postoperative period.[13] In a study performed by Shander et al.,[16] it was shown that for preoperative CVS patients, the target Hb level for transfusion (approximately 10 g/dl) should be higher compared to patients without cardiovascular diseases.

In iron deficiency anemia, the primary reason should be determined and treated. Therefore, the gastrointestinal system should be frequently screened. Iron replacement therapy should be initiated and, if there is no contraindication, treatment with oral iron is preferred. Each 325 mg tablet of ferrous sulphate contains 65 mg elemental iron. The daily recommended amount of elemental iron for adults is 150-200 mg. An increase in reticulocyte count is seen at day 7-10 of treatment. Hemoglobin levels increase by 1 g/dl per 2-3 weeks.

Indications for parenteral iron replacement therapy are inflammatory intestinal disease, celiac disease, intolerance of the patient for oral iron replacement therapy and chemotherapy for cancer. For parenteral iron replacement therapy, sodium ferric gluconate and iron sucrose are used.[17-19]

If the anemia results from a vitamin B12 or folic acid deficiency, it can be easily treated with replacement therapy. In the presence of folate deficiency, the treatment with 1 mg/day is administrated until the resolution of anemia. In the presence of vitamin B12 deficiency, intramuscular treatment with cobalamin is used. Therapeutic doses of cobalamin vary according to severity and symptoms of anemia. It is administrated at a dose of 1000 μg/day or 1000 μg/week. Oral cobalamin is as efficient as intramuscular cobalamin. Reticulocyte counts increase within 3-5 days and Hb levels begin to increase after 10 days.[20,21]

For anemia of chronic disease, chronic renal failure and HIV-infected patients treated with zidovudine and other hematologic diseases, preoperative use of erythropoietin may provide benefits. The use of erythropoietin increases the level of hemoglobin and thereby decreases the need for postoperative blood transfusion.[22,23] If erythropoietin is used, hemoglobin levels should be maintained below the targeted hemoglobin level of 12 g/dl and all the patients treated with erythropoietin should be given prophylaxis against thromboembolism.[24] As some studies showed that erythropoietin increases the growth of tumors, in patients with cancer, the use of erythropoietin should be avoided.[25]

Preoperative anemia is the most important determinant of perioperative erythrocyte transfusion that has many risks and side effects.[26,27] The aim of blood transfusion is to increase oxygen delivery. However, increasing oxygen delivery may not lead to an increase in tissue oxygenation or oxygen consumption.[28,29]

In patients who underwent cardiac surgery, it was found that blood transfusion is correlated with increased morbidity and mortality. For patients who received blood transfusions during the CBAG, it was reported that the risk for infections especially pulmonary infections was increased and the incidence of ischemic events was higher.[30] In acute intensive care patients, limited blood transfusion (when Hb is <7 g/dl, transfusion) and liberal (Hb<10 g/dl) transfusion strategies were compared and the group that received limited blood transfusion showed lower mortality and organ failure.[31] Thereafter, investigators reviewed the results of patients with underlying cardiac disease and saw that a total of 357 patients were not different in terms of mortality but in the liberal group, organ dysfunction was more frequently observed.[32]

The American Society of Anesthesiology recommends transfusion when hemoglobin levels are lower than 6 g/dl. When hemoglobin levels are greater than 10 g/dl, transfusion is rarely required. When hemoglobin levels are between 6-10 g/dl, the decision about transfusion should be based on intravascular volume status, ischemia status of organs, predisposition to insufficient oxygenation and risks for bleeding.[3,33] If there is no ischemic heart disease and the patient is asymptomatic, a hemoglobin level of 7 g/dl may be safely used as the transfusion threshold for the majority of preoperative patients.[3] In humans, the critical Hb/Hct limit which will impair tissue oxygenition is unknown, although a previous study showed that tissue oxygenation was not impaired even at a level of 5 g/dl.[34] For patients with cardiovascular disease, the optimal transfusion threshold is not known. There is no randomized, clinical study to determine it. Transfusion should not be based on hemoglobin level alone, but also on symptoms and clinical findings of the patient.[3]

In sickle cell disease, preoperative transfusion should be administrated, because in this patient group, the perioperative complication rate is 67%. Surgical stress and trauma may increase the formation of sickle cells.[35,36]

A correlation was found between storage time of blood and mortality. A correlation was also found between the age of red blood cells given to patients during CABG and postoperative morbidity-mortality.[37] In a recently published study, data of approximately 6000 patients who underwent open cardiac surgery were reviewed and it was seen that in patients who received transfusion with blood stored for a period of more than two weeks, the incidence of complications such as nosocomial mortality, intubation lasting more than 72 hours and septicemia/sepsis were significantly higher.[38]

The refusal of Jehovah's Witnesses to accept transfusion of blood or blood products under any circumstances presents both moral and ethical challenges to surgeons and anaesthetists undertaking high-risk surgical procedures. Cardiac surgery is often associated with heavy blood loss and high transfusion requirements.[39-41] Preoperative donation and storage of autologous blood, as well as intraoperative blood storage and normovolemic or hypervolemic haemodilution, using crystalloid or artificial colloid solutions are effective in decreasing homologous blood transfusion.[42,43] The use of aprotinin has provided a potential opportunity for improving blood conservation in patients. Aprotinin has convincingly been demonstrated to reduce blood loss during and after CPB, possibly by decreasing CPB-mediated platelet activation and reduction of fibrinolytic activity.[44] The preoperative use of erythropoietin therapy among a group of Jehovah's Witnesses elevated their hemoglobin levels and faciliated autologous blood donation. Yazıcıoğlu et al.[45] reported that erythropoietin therapy helped restore Hct more quickly in patients with severe postoperative anaemia after CABG.

In conclusion, since there is a correlation between preoperative anemia and adverse events seen after cardiac surgery in patients who underwent CVS, determination and treatment of the reasons for preoperative anemia may lessen postoperative adverse events. Treatment of preoperative anemia has low risks but can lead to delays in surgical intervention.[46] Preoperative low hemoglobin levels are a determinant of both comorbidity and short- and long-term mortality. Future studies are warranted to understand whether, in patients who will undergo cardiac surgery, the strategies targeting treatment for preoperative anemia would prevent adverse cardiac events.

Declaration of conflicting interests
The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

The authors received no financial support for the research and/or authorship of this article.


1) Weisberg AD, Weisberg EL, Wilson JM, Collard CD. Preoperative evaluation and preparation of the patient for cardiac surgery. Med Clin North Am 2009;93:979-94.

2) Jacob G, Raj SR, Ketch T, Pavlin B, Biaggioni I, Ertl AC, et al. Postural pseudoanemia: posture-dependent change in hematocrit. Mayo Clin Proc 2005;80:611-4.

3) Patel MS, Carson JL. Anemia in the preoperative patient. Med Clin North Am 2009;93:1095-104.

4) Kulier A, Levin J, Moser R, Rumpold-Seitlinger G, Tudor IC, Snyder-Ramos SA, et al. Impact of preoperative anemia on outcome in patients undergoing coronary artery bypass graft surgery. Circulation 2007;116:471-9.

5) Spiess BD. Transfusion of blood products affects outcome in cardiac surgery. Semin Cardiothorac Vasc Anesth 2004; 8:267-81.

6) Karski JM, Mathieu M, Cheng D. Etiology of preoperative anemia in patients undergoing scheduled cardiac surgery. Can J Anaesth 1999;46:979-82.

7) Zindrou D, Taylor KM, Bagger JP. Preoperative hemoglobin concentration and mortality rate after coronary artery bypass surgery. Lancet 2002;359:1747-8.

8) Cladellas M, Bruguera J, Comín J, Vila J, de Jaime E, Martí J, et al. Is pre-operative anaemia a risk marker for in-hospital mortality and morbidity after valve replacement? Eur Heart J 2006;27:1093-9.

9) Carson JL, Duff A, Poses RM, Berlin JA, Spence RK, Trout R, et al. Effect of anaemia and cardiovascular disease on surgical mortality and morbidity. Lancet 1996; 348:1055-60.

10) Habib RH, Zacharias A, Schwann TA, Riordan CJ, Durham SJ, Shah A. Adverse effects of low hematocrit during cardiopulmonary bypass in the adult: should current practice be changed? J Thorac Cardiovasc Surg 2003;125:1438-50.

11) Karkouti K, Beattie WS, Wijeysundera DN, Rao V, Chan C, Dattilo KM, et al. Hemodilution during cardiopulmonary bypass is an independent risk factor for acute renal failure in adult cardiac surgery. J Thorac Cardiovasc Surg 2005; 129:391-400.

12) Ranucci M, Romitti F, Isgrò G, Cotza M, Brozzi S, Boncilli A, et al. Oxygen delivery during cardiopulmonary bypass and acute renal failure after coronary operations. Ann Thorac Surg 2005;80:2213-20.

13) van Straten AH, Hamad MA, van Zundert AJ, Martens EJ, Schönberger JP, de Wolf AM. Preoperative hemoglobin level as a predictor of survival after coronary artery bypass grafting: a comparison with the matched general population. Circulation 2009;120:118-25.

14) Armas-Loughran B, Kalra R, Carson JL. Evaluation and management of anemia and bleeding disorders in surgical patients. Med Clin North Am 2003;87:229-42.

15) Bell ML, Grunwald GK, Baltz JH, McDonald GO, Bell MR, Grover FL, et al. Does preoperative hemoglobin independently predict short-term outcomes after coronary artery bypass graft surgery? Ann Thorac Surg 2008;86:1415-23.

16) Shander A, Knight K, Thurer R, Adamson J, Spence R. Prevalence and outcomes of anemia in surgery: a systematic review of the literature. Am J Med 2004;116 Suppl 7A:58S-69S.

17) Auerbach M, Goodnough LT, Picard D, Maniatis A. The role of intravenous iron in anemia management and transfusion avoidance. Transfusion 2008;48:988-1000.

18) Critchley J, Dundar Y. Adverse events associated with intravenous iron infusion (low-molecular weight iron dextran and iron sucrose): a systematic review. Transfus Altern Transfus Med 2007;9:8-36.

19) Moniem KA, Bhandari S. Tolerability and efficacy of parenteral iron therapy in hemodialysis patients, a comparison of preparations. Transfus Altern Transfus Med 2007;9:37-42.

20) Eussen SJ, de Groot LC, Clarke R, Schneede J, Ueland PM, Hoefnagels WH, et al. Oral cyanocobalamin supplementation in older people with vitamin B12 deficiency: a dosefinding trial. Arch Intern Med 2005;165:1167-72.

21) Kuzminski AM, Del Giacco EJ, Allen RH, Stabler SP, Lindenbaum J. Effective treatment of cobalamin deficiency with oral cobalamin. Blood 1998;92:1191-8.

22) Faris PM, Ritter MA, Abels RI. The effects of recombinant human erythropoietin on perioperative transfusion requirements in patients having a major orthopaedic operation. The American Erythropoietin Study Group. J Bone Joint Surg [Am] 1996;78:62-72.

23) Laupacis A, Feagan B, Wong C. Effectiveness of perioperative recombinant human erythropoietin in elective hip replacement. COPES Study Group. Lancet 1993;342:378.

24) Phrommintikul A, Haas SJ, Elsik M, Krum H. Mortality and target haemoglobin concentrations in anaemic patients with chronic kidney disease treated with erythropoietin: a metaanalysis. Lancet 2007;369:381-8.

25) Henke M, Laszig R, Rübe C, Schäfer U, Haase KD, Schilcher B, et al. Erythropoietin to treat head and neck cancer patients with anaemia undergoing radiotherapy: randomised, doubleblind, placebo-controlled trial. Lancet 2003;362:1255-60.

26) Khanna MP, Hébert PC, Fergusson DA. Review of the clinical practice literature on patient characteristics associated with perioperative allogeneic red blood cell transfusion. Transfus Med Rev 2003;17:110-9.

27) Vincent JL, Baron JF, Reinhart K, Gattinoni L, Thijs L, Webb A, et al. Anemia and blood transfusion in critically ill patients. JAMA 2002;288:1499-507.

28) Lorente JA, Landín L, De Pablo R, Renes E, Rodríguez-Díaz R, Liste D. Effects of blood transfusion on oxygen transport variables in severe sepsis. Crit Care Med 1993;21:1312-8.

29) Fernandes CJ Jr, Akamine N, De Marco FV, De Souza JA, Lagudis S, Knobel E. Red blood cell transfusion does not increase oxygen consumption in critically ill septic patients. Crit Care 2001;5:362-7.

30) Murphy GJ, Reeves BC, Rogers CA, Rizvi SI, Culliford L, Angelini GD. Increased mortality, postoperative morbidity, and cost after red blood cell transfusion in patients having cardiac surgery. Circulation 2007;116:2544-52.

31) Hébert PC, Wells G, Blajchman MA, Marshall J, Martin C, Pagliarello G, et al. A multicenter, randomized, controlled clinical trial of transfusion requirements in critical care. Transfusion Requirements in Critical Care Investigators, Canadian Critical Care Trials Group. N Engl J Med 1999; 340:409-17.

32) Hébert PC, Yetisir E, Martin C, Blajchman MA, Wells G, Marshall J. Transfusion Requirements in Critical Care Investigators for the Canadian Critical Care Trials Group. Is a low transfusion threshold safe in critically ill patients with cardiovascular diseases? Crit Care Med 2001;29:227-34.

33) American Society of Anesthesiologists Task Force on Perioperative Blood Transfusion and Adjuvant Therapies. Practice guidelines for perioperative blood transfusion and adjuvant therapies: an updated report by the American Society of Anesthesiologists Task Force on Perioperative Blood Transfusion and Adjuvant Therapies. Anesthesiology 2006;105:198-208.

34) Weiskopf RB, Viele MK, Feiner J, Kelley S, Lieberman J, Noorani M, et al. Human cardiovascular and metabolic response to acute, severe isovolemic anemia. JAMA 1998; 279:217-21.

35) Vichinsky EP, Haberkern CM, Neumayr L, Earles AN, Black D, Koshy M, et al. A comparison of conservative and aggressive transfusion regimens in the perioperative management of sickle cell disease. The Preoperative Transfusion in Sickle Cell Disease Study Group. N Engl J Med 1995;333:206-13.

36) Vichinsky EP, Neumayr LD, Haberkern C, Earles AN, Eckman J, Koshy M, et al. The perioperative complication rate of orthopedic surgery in sickle cell disease: report of the National Sickle Cell Surgery Study Group. Am J Hematol 1999;62:129-38.

37) Vamvakas EC, Carven JH. Length of storage of transfused red cells and postoperative morbidity in patients undergoing coronary artery bypass graft surgery. Transfusion 2000;40:101-9.

38) Koch CG, Li L, Sessler DI, Figueroa P, Hoeltge GA, Mihaljevic T, et al. Duration of red-cell storage and complications after cardiac surgery. N Engl J Med 2008;358:1229-39.

39) Covin R, O'Brien M, Grunwald G, Brimhall B, Sethi G, Walczak S, et al. Factors affecting transfusion of fresh frozen plasma, platelets, and red blood cells during elective coronary artery bypass graft surgery. Arch Pathol Lab Med 2003; 127:415-23.

40) Bélisle S, Hardy JF. Hemorrhage and the use of blood products after adult cardiac operations: myths and realities. Ann Thorac Surg 1996;62:1908-17.

41) Steiner ME, Despotis GJ. Transfusion algorithms and how they apply to blood conservation: the high-risk cardiac surgical patient. Hematol Oncol Clin North Am 2007;21:177-84.

42) Licker M, Ellenberger C, Sierra J, Kalangos A, Diaper J, Morel D. Cardioprotective effects of acute normovolemic hemodilution in patients undergoing coronary artery bypass surgery. Chest 2005;128:838-47.

43) Trouwborst A, Hagenouw RR, Jeekel J, Ong GL. Hypervolaemic haemodilution in an anaemic Jehovah's Witness. Br J Anaesth 1990;64:646-8.

44) Bojanov G, Belani KG. Aprotinin - an update for the perioperative physician. Ann Card Anaesth 2005;8:75-80.

45) Yazicioğlu L, Eryilmaz S, Sirlak M, Inan MB, Aral A, Taşöz R, et al. Recombinant human erythropoietin administration in cardiac surgery. J Thorac Cardiovasc Surg 2001; 122:741-5.

46) Karkouti K, Wijeysundera DN, Beattie WS. Risk associated with preoperative anemia in cardiac surgery: a multicenter cohort study. Circulation 2008;117:478-84.

Keywords : Anemia/etiology/therapy; blood transfusion; cardiopulmonary bypass/adverse effects; comorbidity; coronary artery bypass/method; Infection/etiology; postoperative complications
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