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Eur J Cardiothorac Surg 2001;20:891-892
© 2001 Elsevier Science NL
Letter to the Editor |
a Department of Cardiovascular Surgery, University Hospital of Angers, 4 Rue Larrey, 49033 Angers Cedex 01, France
b Department of Neurology, University Hospital of Angers, 4 Rue Larrey, 49033 Angers Cedex 01, France
Received 25 June 2001; accepted 7 July 2001.
Corresponding author. Tel.: +33-2-4135-4573; fax: +33-2-4135-5280
e-mail: chbaufreton{at}chu-angers.fr
Key Words: Aorta • Thoracic surgery • Cardiopulmonary bypass • Perfusion methods • Brain/blood supply • Neuropsychological tests • Cognition disorders
We read with great interest the article by Reich and colleagues entitled "Retrograde cerebral perfusion during thoracic aortic surgery and late neuropsychological dysfunction" [1]. The authors concluded that retrograde cerebral perfusion (RCP) was associated with postoperative neurological deficits and adverse neuropsychological outcome in a small cohort of patients undergoing thoracic aortic surgery.
We would appreciate the opportunity to comment on their results since we have demonstrated evidence of brain perfusion through RCP [2], and since we published, 3 years ago, our initial experience in acute surgery of the aortic arch [3]. In quite a similar number of patients with prolonged RCP as reported by Reich, we found that RCP exceeding 45 min in duration in 90% of our patients (median duration at 68 min) was safe from a neuropsychological point of view. Risk factors impairing the long-term neuropsychological performance, namely increasing age and a poor education level, were the same as those generally observed in a population undergoing conventional cardiac surgery. Our results are thus in opposition to the conclusion reported by the authors.
However, the data found in the article by Reich do not support the statements reported in the discussion. Although these elective patients have been prospectively enrolled in a trial under an approved informed consent, the RCP use has not been randomized, and the reason for using it or not was not clearly mentioned, as well as the exclusion criteria for not completing the neuropsychological testing after the operation. It appears that in some patients, RCP was used for washing atheroembolic debris from the brachiocephalic vessels, thus showing evidence that RCP has been employed in a high-risk subset of patients. This is consistent with the fact that those patients having RCP were also older and had longer cerebral ischemic times. Perfusion pressure in the superior vena cava during RCP is generally recommended to range between 25 and 35 mmHg, even up to 50 mmHg [4]. A perfusion pressure of between 15 and 25 mmHg appears to be too low. The association between RCP and a worse neuropsychological outcome has been established statistically on very few patients, particularly in the subgroup of patients more prone to such a poor outcome when the ischemic time exceeded 35 min. Moreover, the statistical relationships between RCP and an adverse outcome were controlled separately for cerebral ischemic time and for age, but did not reach statistical significance when considered together in the multivariate analysis. There are other variables, such as education level or time interval between operation and testing, that are of major importance in that type of neuropsychological evaluation [5,6]. Education level was apparently not considered in the analysis. Furthermore, if the preoperative neuropsychological assessment is available close to the operation (data not shown), it may reflect the magnitude of anxiety more than cognitive function [7]. On the other hand, the influence of cardiopulmonary bypass and general anesthesia may have a significant impact on the neuropsychological performance up to 6 months postoperatively [5,6]. In this study, the postoperative surgical follow-up visit occurred systematically within a time range potentially affected by factors other than RCP itself.
Should we consider that RCP has to be compared with hypothermic circulatory arrest (HCA) for short episodes of cerebral ischemia? HCA protects the brain efficiently for up to 30 min of cerebral ischemia, as mostly encountered in this study. We rather believe that the aim of RCP is first of all to improve the neurological and neuropsychological outcome, knowing that this outcome would be impaired if HCA, as a sole method of cerebral protection, exceeded 45 min in duration. RCP is easy to achieve without additional cannulae disturbing the supra-aortic vessels and allows for precise reconstruction of a markedly diseased aortic arch when required. For the moment, there is no reported upward duration of RCP at a significant cut-off value associated with impaired long-term neuropsychological outcome.
References
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