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Cerebral oxygen saturation monitoring in on-pump cardiac surgery – A 1 year experience

J. Schön1, V. Serien1, T. Hanke2, M. Bechtel2, H. Heinze1, H. V. Groesdonk1, B. Sedemund-Adib1, K. U. Berger1, S. Eleftheriadis3, M. Heringlake1
1Departments of Anesthesiology and 2Cardiac and Thoracic Vascular Surgery, University of Lübeck, Lübeck, Germany; 3Department of Anesthesiology, General University Hospital of Alexandroupolis, Greece
[Applied Cardiopulmonary Pathophysiology 13: 243-252, 2009]


Objective: To determine the usefulness of cerebral oxygen saturation monitoring in a heterogeneous population of patients undergoing on-pump cardiac surgery and the relationship between minimal perioperative cerebral oxygen saturation (rSO2) levels and clinically relevant outcome parameters.
Setting: Cardiac anesthesia unit of a University Hospital 
Design: Retrospective analysis
Participants: n=274 patients monitored bi-hemispherically with an INVOS 5100 cerebral oxymeter and n=526 matched patients without cerebral oxygenation monitoring. The decision to monitor a patient was based on individual co-morbidities associated with an increased risk of stroke (cerebral and/or peripheral artery disease, history of stroke) at the discretion of the attending anesthetist.
Interventions: None prespecified.
Measurements and main results: In a first analysis, all patients that had been monitored by cerebral oximetry in 2006 were determined by analysis of the anesthesia charts and the institutional cardiac surgery database and compared with a control group matched for Euroscore, age, and type of surgery. This analysis revealed that monitored patients had more preoperative risk factors, had a longer duration of surgery, cardiopulmonary bypass and aortic crossclamp, and needed longer high dependency unit care (all p<0.05) than the control patients. However, major postoperative complications were not different between both groups.
In a second analytical step, monitored patients showing intraoperative minimal rSO2 levels of less than 50% or rSO2 levels greater than 50% were compared. This analysis revealed a higher incidence of postoperative organ dysfunction and hospital length of stay in patients with low rSO2 levels. However, groups were not comparable with respect to the preoperative risk profile.
To adjust for these differences, in a third analytical step, patients were stratified according to the median Euroscore. This analysis revealed, that patients with an Euroscore ≤ 8 and intraoperative rSO2 levels <50% had more postoperative organ complications and longer high dependency unit and hospital stay in comparison to patients not showing intraoperative cerebral hypoperfusion. Such effects were not detectable in patients with a Euroscore > 8.
Conclusions: These data suggests that patients with a higher risk profile for cerebral vascular accidents and renal dysfunction undergoing on-pump cardiac surgery may benefit from cerebral oxygenation monitoring and that rSO2 levels < 50% are associated with an unfavourable clinical course. However, the association between low cerebral oxygen saturation and worse outcome seems to be limited to patients with a low to moderate risk profile (Euroscore ≤ 8).

Keywords: cerebral oxygenation, near infrared spectroscopy, cardiac surgery, outcome

Address for corresponding:
Priv.-Doz. Dr. Matthias Heringlake; Klinik für Anästhesiologie, Universität zu Lübeck, Ratzeburger Allee 160, 23538 Lübeck; Germany
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