Preoperative Hemoglobin Levels and Outcomes in Cardiovascular Surgical Patients; systematic review and meta-analysis
Objective: To determine whether preoperative anemia in patients undergoing cardiovascular surgery is associated with higher mortality, renal failure, cerebrovascular accidents and cardiovascular events as compared to patients with normal preoperative levels of hemoglobin.
Methods: A systematic review and a meta-analysis of the cohort observational and of cases and control studies was conducted, exploring the association between the pre-surgical levels of hemoglobin and adverse outcomes in patients undergoing cardiovascular surgery. The MEDLINE, EMBASE, and COCHRANE data-bases up to the 50th week of 2010 were consulted. The studies that complied with the inclusion criteria were independently selected. The sources of heterogeneity among the studies were assessed, including publication bias.
Results: Of the total number of studies reviewed, 260 were identified; sufficient data could be extracted from 11 of them to combine the mortality outcome. Out of these studies, 6 were adjusted for severity and comorbidities, while the results of the remaining ones were not adjusted.
Conclusions: Anemic patients undergoing cardiac surgery have a higher risk of postoperative adverse events. There are several factors limiting the interpretation of the data, including a poor standardized definition of anemia, and the lack of studies explicitly designed to quantify the prevalence and the impact of anemia in patients with cardiovascular diseases.
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