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Letters to the Editor

Guided cerebral protection in cardiac surgery

^a Department of Anaesthesiology, University Hospital of Geneva, Switzerland
^b Department of Cardiovascular Surgery, University Hospital of Geneva, Switzerland

Received 6 July 2007; accepted 8 August 2007.

^_* Corresponding author. Tel.: +41 22 3723311; fax: +41 22 3727511. (Email: christoph.ellenberger{at}hcuge.ch).

Key Words: Cardiac surgery • Stroke • Cerebral blood flow • Neuromonitoring • Neuroprotection

Papantchev et al. [1] have to be congratulated for providing clinicians valuable information based on their extensive anatomical examination of the main cerebral arteries (circle of Willis) in 112 cadavers. The results from this study show the need for reassessing the current perioperative care of cardiac patients in at least three areas: (1) demonstration of the high prevalence of anatomical variations in the circle of Willis (42%) stresses the need for preoperative CT-angiographic imaging of the cerebral vascular network; (2) a low-to-normal blood pressure and/or selective cerebral perfusion (SCP) could be blamed for increasing the risk of diffuse watershed strokes by preventing washout of small emboli and by limiting perfusion in brain areas with abnormal vascular supply; (3) with a broader understanding of the frequency and mechanisms of neurological injuries, we should be able to tailor personalised neuroprotective strategies that may considerably improve quality of life after cardiac surgery.

Several clinical investigations have demonstrated the usefulness of both the bispectral index (BIS) of the electroencephalogram and the transcranial Doppler (TCD) monitoring of the cerebral blood flow to detect neurological dysfunction in critically ill patients and in those undergoing cardiac surgical procedures [2,3]. For instance, sudden falls in BIS or near-infrared spectroscopy (NIRS) values are highly suggestive of ischaemic-induced cerebral events in patients with atheromatous vascular disease as a result of malposition of the arterial cannula or disruption of an atheromatous plaque (aortic cross-clamping and ‘sandblasting effect’ of the high-velocity pump flow). In contrast, progressive and sustained low BIS/NIRS values during cardiopulmonary bypass call for reassessing not only the depth of anaesthesia but also cerebral blood flow with TCD.

During moderate or deep hypothermia, BIS values decrease in parallel with the metabolic cerebral activity whereas changes in NIRS values poorly correlate with CT-imaging and histologic brain damages [2–4]. Accordingly, assessment of the cerebral blood flow with TCD through the temporal, ophthalmic and/or occipital windows is strongly advocated in high-risk cardiac procedures such as aortic root and arch reconstruction using deep hypothermic circulatory arrest, SCP or retrograde cerebral perfusion. Abnormal flow patterns (bilateral or unilateral) could be potentially reversed either by increasing pump flow, increasing systemic blood pressure or by cannulating the contralateral brachiocephalic trunk.

Given the high prevalence of cerebrovascular abnormalities, better knowledge of the mechanisms of brain injuries and the economic burden of postoperative neurological damages, outcome research studies are urgently required in this important area toward making the perioperative period and beyond, safer for all patients undergoing cardiac surgical procedures [4].

In line with the authors’ proposals, we recommend the routine application of a stepwise multimodality neuroprotective approach (e.g., hypothermia, SCP unilateral vs bilateral, carotid endarterectomy) guided by preoperative radiological imaging (circle of Willis abnormality, carotid stenosis/occlusion) as well as by current intraoperative monitoring tools such as transoesophageal echocardiography (e.g., intra-cardiac thrombus, atheroma and calcification of the ascending aorta), TCD and brain activity monitors (e.g., NIRS, BIS) [5].

References

1. Papantchev V, Hristov S, Todorova D, Naydenov E, Paloff A, Nikolov D, Tschirkov A, Ovtscharoff W. Some variations of the circle of Willis, important for cerebral protection in aortic surgery—a study in Eastern Europeans. Eur J Cardiothorac Surg 2007;31(6):982-989.[Abstract/Free Full Text]
2. McKhann GM, Grega MA, Borowicz Jr. LM, Baumgartner WA, Selnes OA. Stroke and encephalopathy after cardiac surgery: an update. Stroke 2006;37:562-571.[Abstract/Free Full Text]
3. Vretzakis G, Ferdi E, Argiriadou H, Papaziogas B, Mikroulis D, Lazarides M, Bitzikas G, Bougioukas G. Influence of bispectral index monitoring on decision making during cardiac anesthesia. J Clin Anesth 2005;17:509-516.[CrossRef][Medline]
4. Newman MF, Mathew JP, Grocott HP, Mackensen GB, Monk T, Welsh-Bohmer KA, Blumenthal JA, Laskowitz DT, Mark DB. Central nervous system injury associated with cardiac surgery. Lancet 2006;368(9536):694-703.[CrossRef][Medline]
5. Edmonds Jr. HR. Multi-modality neurophysiologic monitoring for cardiac surgery. Heart Surg Forum 2002;5(3):225-228.[Medline]

This article has been cited by other articles:

				V. Papantchev, G. Nachev, D. Petkov, and W. Ovtscharoff Reply to Ellenberger et al. Eur. J. Cardiothorac. Surg., November 1, 2007; 32(5): 823 - 823. [Full Text] [PDF]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ellenberger, C. Articles by Licker, M. Search for Related Content PubMed PubMed Citation Articles by Ellenberger, C. Articles by Licker, M. Related Collections Anesthesia Cerebral protection Extracorporeal circulation