Preoperative Anemia in Elective Cardiac Surgery: Prevalence, Risk Factors, and Influence on Postoperative Outcome

Manuel Muñoz, PhD; Daniel Ariza, PhD; Susana Gómez-RamÍrez‡, MD; Paula Hernández, MD; José A. García-Erce§ PhD; Santiago R. Leal-Noval; PhD

Disclosures

Transfusion Alter Transfusion Med. 2010;11(2):47-56.

Abstract and Introduction

Abstract

Preoperative anemia in patients undergoing cardiac surgery is associated with a higher transfusion risk and poorer outcomes. This retrospective study was undertaken to assess the prevalence of preoperative anemia and its associated risk factors, as well as its influence on postoperative outcomes, in 576 patients undergoing elective cardiac surgery (52.3% with cardiopulmonary bypass) for myocardial revascularization, valve replacement, coronary + valve, or miscellaneous pathology at a single institution. Perioperative data were reviewed according to the presence or absence of preoperative anemia (hemoglobin < 13 g/dL for men, hemoglobin < 12 g/dL for women). Overall, 210 patients (36.5%) presented with anemia. Logistic regression analysis revealed that age, chronic kidney disease, and consumption of proton pump inhibitors histamine H₂ receptor antagonists and diuretics were independent risk factors for the presence of preoperative anemia. Postoperatively, anemic patients received transfusions and inotropic support and stayed longer than 4 days in the recovery unit more frequently than non-anemic patients, but there were no differences in the composite outcome variable (stroke, myocardial infarction, renal failure or death). In conclusion, our data seem to indicate that preoperative anemia has a high prevalence among elective cardiac surgical patients and increases postoperative morbidity. Therefore, we need to address two specific areas about preoperative anemia in these patients: early recognition and evaluation, and appropriate and timely treatment.

Introduction

Cardiac surgery (CS) procedures, with or without cardiopulmonary bypass (CPB), are frequently associated with a substantial blood loss, and a significant proportion of patients receive perioperative allogeneic blood transfusion (ABT), which in turn may increase the risk for postoperative complications (e.g. increased rate of postoperative infections)^[1–3] and mortality.^[4] On the other hand, in the last few years there have been an increased demand for CS in elderly patients (> 65 years old), in spite of their higher rate of comorbidities.^[5,6] All these had led to changes in the relative risk associated to well-known risk factors and to take into consideration new risk factors, such as preoperative anemia (PA).

Thus, preoperative hemoglobin (Hb) or hematocrit values are useful parameters for predicting the risk of receiving ABT,^[7] whereas PA is associated not only with an increased risk of ABT,^[8,9] but also with an increased risk for postoperative complications and lower survival rates after coronary bypass grafting surgery.^[10–14] In addition, PA and low preoperative erythrocyte mass are among the few preoperative risk factors that can be modified to reduce the risk of perioperative ABT.^[15]

Consequently, if patients at risk of receiving perioperative ABT can be identified early enough prior to CS, they can be targeted to specific preventive and therapeutic measures.^[16] Among them, early detection of PA would most probably allows the implementation of therapeutic measures to reduce risks (level of evidence A, recommendation class I).^[17] We therefore analyzed the prevalence of and risks factors for PA, as well as the influence of PA on transfusion rates and adverse postoperative outcomes, in patients undergoing elective CS.

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Abstract and Introduction
Methods
Results
Discussion
References

Table 1. Demographic and clinical data of patients undergoing elective cardiac surgery, according to the presence or absence of preoperative anemia
	Non-anemic patients	Anemic patients	P
Patients (n)	366	210	–
Age (years)	63 ± 11	67 ± 10	0.001
Gender (female/male)	94/272	66/144	0.158
Creatinine (mg/dL)	1.0 ± 0.3	1.2 ± 0.7	0.002
Glomerular filtration (mL/min/1.73 m²)	83 ± 34	74 ± 31	0.006
LVEF, n (%)			0.716
> 50%	260 (71)	145 (69)
30–50%	84 (23)	51 (24)
< 30%	22 (6)	14 (7)
EuroScore	5.0 ± 2.7	5.8 ± 2.6	0.001
Comorbidities, n (%)
Hypertension	191 (52)	135 (64)	0.005
Diabetes	117 (32)	84 (40)	0.054
Chronic kidney disease	7 (2)	16 (8)	0.001
Dyslipemia	190 (52)	109 (52)	0.957
Chronic cardiac failure	118 (32)	65 (31)	0.402
Chronic obstrutive pulmonary disease	41 (11)	20 (10)	0.529
Medications, n (%)
Antiplatelets	171 (47)	97 (46)	0.902
Anticoagulants	131 (36)	79 (38)	0.577
Diuretics	138 (38)	104 (50)	0.015
β-Blockers	233 (64)	129 (61)	0.558
ACEI/ARAII	185 (50)	131 (63)	0.006
Ca-antagonists	89 (24)	61 (29)	0.212
Statins	159 (43)	94 (44)	0.717
Nitrites	142 (39)	93 (44)	0.160
Digoxine	54 (15)	19 (9)	0.048
PPI/antiH₂	160 (44)	119 (57)	0.003

LVEF, lef ventricular ejection fraction; ACEI/ARAII, angiotensin-converting enzyme inhibitors or angiotensin receptor antagonists; PPI/antiH₂, proton pump inhibitors or histamine H₂ receptor antagonists.

Table 2. Variables independently associated with preoperative anemia in the multivariate analysis
	Typo of variable	Odds ratio	95% confidence interval	P
Age	Continuous	1.037	1.017–1.056	< 0.001
CKD	Categorical	3.161	1.258–7.946	0.014
Diuretics	Categorical	1.504	1.048–2.159	0.027
PPI/antiH₂	Categorical	1.531	1.066–2.201	0.021

CKD, chronic kidney disease; PPI/antiH₂, proton pump inhibitors or histamine H₂ receptor antagonists.

Table 3. Perioperative clinical data of patients undergoing elective cardiac surgery, according to the presence or absence of preoperative anemia
	Non-anemic patients	Anemic patients	P
Patients (n)	366	210	–
Hemoglobin (g/dL)
Preoperative	14.1 ± 1.2	11.4 ± 1.0	0.001
Postoperative	11.3 ± 1.2	10.3 ± 1.3	0.001
Discharge from PCU	10.5 ± 1.0	10.3 ± 1.1	0.068
Type of surgery, n (%)			0.216
Coronary bypass	206 (56)	117 (56)
Valve replacement	126 (34)	63 (30)
Coronary + valve	20 (5)	21 (10)
Miscellaneous	14 (4)	9 (4)
CPB use, n (%)	109 (52)	111 (53)	0.818
Length of surgery (min)	259 ± 61	263 ± 71	0.430
CPB time (min)	109 ± 38	119 ± 44	0.040
Cross-clamping time (min)	73 ± 27	81 ± 36	0.046
Number of grafts (n)	1.4 ± 1.3	1.5 ± 1.6	0.341
Perioperative blood loss (mL)	1203 ± 615	1101 ± 445	0.250
Transfusion rates (n, %)
RBC	121 (33)	142 (68)	0.001
Platelets	16 (2.7)	9 (4.3)	0.409
FFP	15 (4.1)	16 (7.6)	0.578
Transfused RBC index (U/pte)	0.8 ± 1.4	1.8 ± 1.7	0.001
Extubation time (h)	12 ± 57	10 ± 34	0.653
Length of PCU stay (days)	5 ± 8	6 ± 8	0.500
Length of hospital stay (days)	11 ± 18	13 ± 13	0.134

CBP, cardiopulmonary bypass; RBC, red blood cell concentrate; FFP, fresh frozen plasma; PCU, postoperative care unit.

Table 4. Postoperative complications in patients undergoing elective cardiac surgery, according to the presence or absence of preoperative
	Non-anemic patients	Anemic patients	P
Patients (n)	366	210	81
Infection, n (%)	27 (7)	20 (9)	0.432
Urinary tract	3	2
Pneumonia	13	9
Mediastinitis	0	1
Sepsis	8	6
Surgical wound	0	1
Catheter	3	1
Atrial fibrillation, n (%)	80 (22)	51 (24)	0.501
Inotropic support, n (%)	180 (49)	129 (61)	0.005
Respiratory dysfunction, n (%)	29 (8)	21 (10)	0.520
Re-operation, n (%)	6 (2)	3 (1)	0.845
Myocardial infarction, n (%)	17 (5)	16 (8)	0.139
New onset renal failure, n (%)	4 (1)	6 (3)	0.182
Stroke, n (%)	5 (2)	0 (0)	0.089
In-hospital mortality, n (%)	19 (5)	12 (6)	0.787
Composite outcome, n (%)	34 (9)	27 (13)	0.180

Table 5. Postoperative infection, and in-hospital mortality rates in transfused (+ABT) and non-transfused (−ABT) patients undergoing elective cardiac surgery, according to the presence or absence of preoperative anemia
	Infection rate, n (%)			Mortality rate, n (%)			Composite, n (%)
	−ABT	+ABT	P*	−ABT	+ABT	P*	−ABT	+ABT	P*
All patients	20 (6.4)	27 (10.3)	0.125	13 (4.2)	18 (6.8)	0.155	25 (8.0)	36 (13.7)	0.038
Non-anemic patients	14 (5.7)	13 (10.7)	0.115	11 (4.5)	8 (6.6)	0.384	20 (8.2)	14 (11.6)	0.285
Anemic patients	6 (8.8)	14 (9.9)	0.823	2 (2.9)	10 (7.0)	0.110	5 (7.4)	22 (15.5)	0.189
P	0.426**	0.799***		0.575**	0.902***		0.854**

Composite outcome: stroke, myocardial infarction, renal failure or in-hospital death. P*, for +ABT vs.−ABT;**P, between groups differences for −ABT patients;***P between groups difference for +ABT patients.

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