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Letters to the Editor |
Department of Anesthesia and Intensive Care, IRCCS Policlinico S. Donato, Via Morandi 30, San Donato Milanese, Milan 20097, Italy
Received 26 May 2008; accepted 11 June 2008.
* Corresponding author. Tel. +39 02 52774320; fax: +39 02 55602262. (Email: cardioanestesia{at}virgilio.it).
Key Words: Heparin-bonded circuits • Clinical impact
We read with interest the systematic review and meta-analysis of Mangoush and co-workers [1] recently published in the European Journal of Cardiothoracic Surgery, addressing the clinical impact of heparin-bonded circuits (HBCs) on clinical outcome following cardiac operations. The authors retrieved 41 randomized control trials (RCTs) and could demonstrate that patients treated with HBCs experienced a better outcome, namely in terms of reduced incidence of allogeneic blood product transfusions and resternotomy. Within the exclusion criteria, the authors considered the use of auto-transfusion techniques to manage postoperative bleeding. Of course it is in the right of the authors to decide which criteria should be applied to include RCTs in their meta-analysis. However, the reason for excluding studies where auto-transfusion techniques were employed is unclear. Their decision led to the exclusion of two major RCTs, from Wildevuur and co-workers [2] and McCarthy and co-workers [3], respectively including 805 and 350 patients. Moreover, it is unclear how they could decide in which studies the postoperative auto-transfusion was allowed. As a matter of fact, in one excluded study [2] this technique was clearly mentioned, whereas in the other [3] this is not stated. Conversely, Mangoush and co-workers included in their meta-analysis our study published in 1999 [4]. Actually, our study was focused on high-risk patients, and we applied exactly the same protocol as the previous one [2] focused on low-risk patients, which I co-authored, where postoperative auto-transfusion was allowed. Finally, the authors included the study from Baufreton and co-workers [5], being unaware that it was designed as a separate arm of the main study on low-risk patients [2]. By doing this, they included the same patient population coming from two different studies, and again admitted to the meta-analysis another study, which allowed postoperative auto-transfusion.
As a result of these biases, 1155 patients have been excluded by the analysis. Considering that the population included in the meta-analysis accounts for 3434 patients, the exclusion of 25% of the potential total patient population may lead to wrong conclusions.
Strictly looking at the allogeneic blood transfusions, the authors found out that heparin-bonded circuits were associated with a significant decrease in transfusion rate (odds ratio 0.8, 95% confidence interval 0.6–0.9, p = 0.004). This result is of course strongly dependent on a single study [4] including 886 patients, that theoretically should have been excluded according to the authors’ criteria.
This outcome analysis can be addressed in a different way. If we simply consider the three major RCTs [2–4], without applying artificial exclusion criteria, we can analyze as many as 2041 patients. Pooling these three studies together, the odds ratio for allogeneic blood transfusions is 0.99 (95% confidence interval 0.83–1.19, p = 0.924).
This result denies the protective effect of heparin-bonded circuits in terms of allogeneic blood transfusion rate, and is so far from significant that even including the other 39 RCTs (with a total population of 2548 patients, and a mean number per study of only 65 patients) we are inclined to believe that the results will not change.
References
This article has been cited by other articles:
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  M. Ranucci, A. Balduini, A. Ditta, A. Boncilli, and S. Brozzi A Systematic Review of Biocompatible Cardiopulmonary Bypass Circuits and Clinical Outcome Ann. Thorac. Surg., April 1, 2009; 87(4): 1311 - 1319. [Abstract] [Full Text] [PDF]
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 O. Mangoush Reply to Ranucci Eur. J. Cardiothorac. Surg., September 1, 2008; 34(3): 704 - 705. [Full Text] [PDF]
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