Preoperative Anemia
in Patients Undergoing CABG
Predicts Acute Kidney Injury
L.S. De Santo,
G. Romano, A. Carozza,
A. Della
Corte, F. Grimaldi,
N. Galdieri
M. Cotrufo and M. De Feo
Chair of Cardiac Surgery University of Foggia
Department of Cardiothoracic and Respiratory Sciences, Second University of Naples Department of Cardiovascular Surgery and Transplants, V. Monaldi Hospital, Naples
Study Features
• Study aim: determine the frequency rate and examine the implications of preoperative anemia in patients referred for coronary artery bypass grafting.
• Design: a prospective cohort design was employed segregating study patients according to the presence or absence of preoperative anemia.
• Setting: tertiary care, university affiliated, cardiac surgery centre.
• Primary endpoints: the prevalence of preoperative anemia, and its unadjusted and adjusted relationships with in-hospital death, cardiac morbidity and acute kidney injury were obtained.
• Secondary endpoints: to evaluate the potential dose-response relationship between preoperative anemia severity and primary endpoints.
Study Features
• Definitions: All definitions were selected prospectively as part of the original study design.
• Preoperative anemia: The preoperative haemoglobin level was prospectively defined as the lowest documented hemoglobin value among those measured at admission, during the preoperative period, or immediately before induction of anesthesia.
• Gender-based definition of anemia: (12.0 g/dL in women and 13.0
g/dL in men) and severity scaling complied with World Health
Study Features
• In-hospital death: was defined as death occurring after surgery and during the index hospitalization.
• Cardiac morbidity: was defined as the occurrence of myocardial infarction and / or heart failure.
• Kidney function: The change in kidney function was based on plasma creatinine concentration and defined as the difference between baseline concentration and the highest concentration during the stay in ICU.
• e GFR: Preoperative glomerualr filtration rate (GFR) and smallest GFR during ICU stay were calculated with the Modification of Diet in Renal Disease equation.
Study Features
• Kidney function staging: the National Kidney Foundation Classification staging system was adopted. The severity of chronic kidney disease (CKD) is described by 6 stages, the most severe three are defined by the MDRD-eGFR value, and first three also depend whether there is other evidence of kidney disease (e.g. proteinuria)
•A specific perioperative transfusion algorithm was applied: ie, the patients received two packed red cells units before CPB whenever the preoperative hematocrit value was below 30%, and they received two or more packed red cells units during CPB in case of excessive hemodilution (hematocrit value below 22%).
•After CPB: the patients received packed red cells in order to maintain a hematocrit value higher than 25%. This target value was raised to higher values according to the clinical condition, and namely to the hemodynamic status, the need for inotropic support, and the age of the patient.
•Fresh frozen plasma was not used before reaching the ICU and performing a thromboelastogram.
•Platelets were usually not transfused, unless in patients reaching the operating room under full dose of ASA, ticlopidine or clopidogrel and demonstrating severe postoperative bleeding and altered thromboelastogram.
Acute Kidney injury: followed the classification by the Acute Dialysis Quality Initiative Workgroup.
Study Polpulation
• Time frame: June 2005 and December2006
• Study population: 925 patients (mean age 62.3 12.5, 32.3% females)
• Surgical case mix: CABG 48.8%, valvular procedures 30.1%, thoracic aortic 11%, others 10.1% (heart transplantations 3.8%).
• Surgical priority : elective 72.9%, urgent 15.9% and emergent 11.2%.
• Redo procedures: 6.8%.
WHO Anemia severity scoring Anemia present (n=320) 0 (near normal) 43.1% 1 (mild) 43.4% 2 (moderate) 13.1% 3 (severe) 0.3% 4 (life treathening)
-WHO Anemia severity scoring Anemia present (n=320) 0 (near normal) 71.9% 1 (mild) 20% 2 (moderate) 7.8% 3 (severe) 0.3% 4 (life treathening)
-Baseline Characteristics Study Population (n=1047) Anemia Present (n=320 ) Anemia Absent (n=727) P Age(years) 63.2 9.3 66.9 8.9 61.5 9.1 <0.0001
Body Surface Area (m2) 1.84 0.16 1.81 0.14 1.85 0.16 <0.0001
Female Sex(%) 18.8% 25.3% 16% 0.001
Diabetes mellitus (type I or II) (%) 38.9% 39.4% 38.7% 0.07
Hypertension(%) 70.1% 70.9% 69.7% 0.69
COPD(%) 13.7% 13.5% 13.1% 0.08
Peripheral vascular disease(%) 5.9% 6.0% 5.8%% 0.52
Cerebrovascular disease(%) 6.9% 7.1% 6.6% 0.41
Hypercholesterolemia(%) 41.4% 41.8% 41.2% 0.67
Left ventricular ejection fraction <35%, (%) 15.3% 20.3% 13.1% 0.004
Baseline eGFR (ml/min/1.73m2) 64.2 31.6 60.2 49.56 66.2 18.7 <0.0001
Preoperative medications(%)
Heparin (within 24 h of surgery) 7.4% 10% 6.2% 0.019
Warfarin (within 5 d of surgery) 0.7% 1.3% 0.4% 0.2
Acetylsalicylic acid (within 5 d of surgery) 45.2% 45.3% 45.1% 1
Clopidogrel (within 5 d of surgery) 14.2% 15.4% 13.7% 0.5
Surgical characteristics Study Population (n=1047) Anemia Present (n=320) Anemia Absent (n=727) P Emergent surgery(%) 7.4% 10% 6.2% 0.019 Urgent surgery(%) 24.5% 27.5% 23.2% 0.019 Redo surgery(%) 1.0% 1.3% 0.8% 0.5 Distal anastomosis n 2.66 0.84 2.67 0.83 2.66 0.85 0.78 CPB duration (min) 83.9 33.2 85.3 35.5 83.2 32.2 0.348
Aortic X Clamp duration (min) 44.9 20.2 45.2 20.4 44.8 20.1 0.799
Perioperative Hb/Hct and transfusions variables Study Population (n=1047) Anemia Present (n=320) Anemia Absent (n=727) P Hb, preoperative ( g/dL) 13.42 1.69 11.49 1.15 14.27 1.08 <0.0001 RBCs during CPB (mean SD) 0.55 1.06 1.25 1.41 0.25 0.67 <0.0001 Hct, lowest during CPB(%) 27.3 3.9 25.4 3.2 28.1 3.9 <0.0001
DO2, lowest during CPB (mL min-1m-2) 297.6 48.9 279.8 38 305.5 51.1 <0.0001
RBCs in OR (mean SD) 0.8 1.54 1.66 1.88 0.43 1.04 <0.0001
Hb, ICU admission ( g/dL) 9.33 1.16 8.8 0.9 9.5 1.1 <0.0001
Chest drains (mL/24Hrs) 702.6 356.6 702.6 356.6 727.9 365.8 0.3
Resternotomy for bleeding (%) 2.4% 2.5% 2.3% 0.514
RBCs in ICU 1.07 1.92 1.50 2.27 0.88 1.71 <0.0001
Overall RBC transfusion (mean SD) 2.05 2.89 3.39 3.52 1.46 2.34 <0.0001
Overall PLT transfusion 1.60 3.97 1.95 5.11 1.45 3.32 <0.0001
Overall FFP transfusion 1.54 3.22 1.96 3.67 1.36 2.98 0.006
Outcomes Study Population (n=1047) Anemia Present (n=320) Anemia Absent (n=727) P Cardiac Complications (%) 7.3% 10.3% 5.9% 0.014
Peak eGFR (ml/min/1.73m2) 64.2 31.6 60.2 49.56 66.2 18.7 <0.0001
CVVH (%) 3.4% 6.4% 2.2% 0.002
Prolonged ventilation (>24h) (%) 3.2% 5.3% 2.3% 0.021
Stroke (%) 1.9% 2.8% 1.5% 0.22
Deep Sternal Wound Infection (%) 1.5% 1.5% 1.6% 1.0
ICU stay (days) 3.2 3.9 3.9 5.2 2.9 3.2 <0.0001
Hospital stay (days) 8.07 4.7 8.9 5.8 7.6 4.1 <0.0001
0% 10% 20% 30% 40% 50% 60% NKF class 0 NKF class 1 NKF class 2 NKF class 3 NKF class 4 NKF class 5 Non Anemic Anemic p<0.0001 0% 10% 20% 30% 40% 50% 60% NKF class 0 NKF class 1 NKF class 2 NKF class 3 NKF class 4 NKF class 5 Non Anemic Anemic Preoperative Postoperative p<0.0001
0% 10% 20% 30% 40% 50% 60% 70%
Normal Risk Injury Failure
Non Anemic Anemic
Study overview
Study strength
•Single centre design
•Non selected sample
•“State of the art” definitions of target events
• correction for numerous major confounders
Study limitations
•Single centre design
•observational nature
•lack of information on the etiology and
Conclusions
•Preoperative anemia is frequent in patients referred for CABG and adds
to a significantly more complex preoperative comorbidity profile.
•Even mildly anemic patients experience increased risk of in-hospital
mortality and postoperative morbidity.
•Preoperative anemia is an independent predictor of acute kidney injury a
major determinant of unfavourable outcomes.
•In this respect the effect of anemia is independend from that exerted
Conclusions
•The finding that the odds of being transfused is the other
independent predictor underlies that some critially ill cardiac surgical patients may reach a state of oxygen-supply dependency that goes beyond preoperative anemia and low perioperative hemoglobin concentration.
•The pathophysiologic effect of anemia is multifaced but low CPB DO2
emerges as a crucial step.
•Management of CPB should be therefore targeted to take into account
Conclusions
•Absence of a dose responsivity in the context of at most moderately
severe preoperative anemia actually enhances the importance of this feature
•Lack of information on etiology and chronicity of this illness, and the
observational nature of the study itself prevent the definition of a causal link with outcomes. If these changes are reflective of underlying conditions, then anemia may be a marker of risk and not a modifiable risk factor.
