URL: https://www.clinicaltrials.gov. Unique identifier: NCT02185885.

Background: Postoperative cognitive dysfunction (POCD) occurs commonly after cardiac surgery. Near-infrared spectroscopy (NIRS) has been used to monitor regional cerebral oxygen saturation (rScO 2) in order to minimise the occurrence of POCD by applying dedicated interventions when rScO 2 decreases. However, the association between rScO 2 intraoperatively and POCD has not been clarified. Methods: This is a secondary analysis of a randomised trial with physician-blinded NIRS monitoring and cognitive testing at discharge from hospital and at 3 months after surgery. The association between intraoperative rScO 2 values and POCD at discharge from hospital and at 3 months after surgery was investigated. The prespecified candidate predictive variable of interest was cumulative time during surgery with rScO 2 !10% below its preoperative value. Results: One hundred and fifty-three patients had complete NIRS data and neurocognitive assessments at discharge, and 44 of these patients (29%) had POCD. At 3 months, 148 patients had complete data, and 12 (8%) of these patients had POCD. The median time with rScO 2 >10% below preoperative values did not differ for patients with and without POCD at discharge (difference¼0.0 min; Hodges-Lehmann 95% confidence interval, À3.11e1.47, P¼0.88). Other rScO 2 time thresholds that were assessed were also not significantly different between those with and without POCD at discharge. This applied both to absolute rScO 2 values and relative changes from preoperative values. Similar results were found in relation to POCD at 3 months. Conclusions: No significant association was found between intraoperative rScO 2 values and POCD. These findings bring into question the rationale for attempting to avoid decreases in rScO 2 if the goal is to prevent POCD. Clinical trial registration: NCT 02185885.

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In a randomized blinded study, we observed that a higher MAP induced by vasopressors, with a fixed CPB pump flow, leads to lower mean rScO2 and more frequent and pronounced cerebral desaturation during CPB. The mechanism behind these observations is not clear. We cannot exclude extracranial contamination of the NIRS signal as a possible explanation. However, we cannot recommend increasing MAP by vasoconstrictors during cerebral desaturation because this is not supported by the findings of the present study.

BackgroundDebilitating brain injury occurs in 1.6–5 % of patients undergoing cardiac surgery with cardiopulmonary bypass. Diffusion-weighted magnetic resonance imaging studies have reported stroke-like lesions in up to 51 % of patients after cardiac surgery. The majority of the lesions seem to be caused by emboli, but inadequate blood flow caused by other mechanisms may increase ischaemia in the penumbra or cause watershed infarcts. During cardiopulmonary bypass, blood pressure can be below the lower limit of cerebral autoregulation. Although much debated, the constant blood flow provided by the cardiopulmonary bypass system is still considered by many as appropriate to avoid cerebral ischaemia despite the low blood pressure.Methods/designThe Perfusion Pressure Cerebral Infarct trial is a single-centre superiority trial with a blinded outcome assessment. The trial is randomising 210 patients with coronary vessel and/or valve disease and who are undergoing cardiac surgery with the use of cardiopulmonary bypass. Patients are stratified by age and surgical procedure and are randomised 1:1 to either an increased mean arterial pressure (70–80 mmHg) or ‘usual practice’ (40–50 mmHg) during cardiopulmonary bypass.The cardiopulmonary bypass pump flow is fixed and set at 2.4 L/minute/m2 body surface area plus 10–20 % in both groups.The primary outcome measure is the volume of the new ischaemic cerebral lesions (in mL), expressed as the difference between a baseline, diffusion-weighted, magnetic resonance imaging scan and an equal scan conducted 3–6 days postoperatively. Secondary endpoints are the total number of new ischaemic cerebral lesions, postoperative cognitive dysfunction at discharge and 3 months postoperatively, diffuse cerebral injury evaluated by magnetic resonance spectroscopy and selected biochemical markers of cerebral injury.The sample size will enable us to detect a 50 % reduction in the primary outcome measure in the intervention compared to the control group at a significance level of 0.05 and with a power of 0.80.DiscussionThis is the first clinical randomised study to evaluate whether the mean arterial pressure level during cardiopulmonary bypass influences the development of brain injuries that are detected by diffusion-weighted magnetic resonance imaging.Trial registrationClinicalTrials.gov, NCT02185885. Registered on 7 July 2014.Electronic supplementary materialThe online version of this article (doi:10.1186/s13063-016-1373-6) contains supplementary material, which is available to authorized users.

Background: Near infrared spectroscopy (NIRS) is widely used to monitor regional cerebral tissue oxygenation (rScO 2 ). We compared rScO 2 values during cardiac surgery in patients with or without new cerebral ischaemic lesions on diffusion weighted magnetic resonance imaging (DWI). We hypothesised patients with new cerebral lesions would have impaired tissue oxygenation reflected in their rScO 2 values. Methods: NIRS and DWI data were collected in 152 elective cardiac surgery patients. Absolute rScO 2 values, duration of desaturation below thresholds (baseline, 10%, and 20%), and accumulated cerebral desaturation load were compared between patients with or without new cerebral lesions on DWI. Primary outcome was time below 10% from rScO 2 baseline. Results: The time below 10% from rScO 2 baseline was significantly longer for patients with new cerebral lesions than for patients without [median (inter-quartile range): 11.0 (0.4; 37.5) min vs 1.8 inter-quartile range: (0.05; 20.9) min, P¼0.02]. Furthermore, they had a higher accumulated desaturation load below baseline (P¼0.02) and 10% below baseline (P¼0.02). Finally, their absolute minimum rScO 2 value was significantly lower (P¼0.01). However, the frequency of patients with desaturation below 10% and 20% was comparable between patients with and without new cerebral lesions. Receiveroperating characteristic curve analysis did not identify a clear-cut critical threshold among the investigated rScO 2 variables. Conclusions: Use of NIRS identified significant group differences in rScO 2 values between patients with or without new ischaemic lesions. However, a critical threshold could not be identified because of a high variation in NIRS values across both groups.

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