Microembolic Signals and Cerebrospinal Fluid Markers of Neuronal Damage After Surgical Aortic Valve

Patients and clinical procedures 10 patients scheduled for open aortic valve surgery at our institution will be included into this prospective, observational study. The Human Ethics Committee of the University of Gothenburg, approved the study protocol. The day before surgery a lumbar puncture at level L3-4 will be performed using a 27G Whitacre needle. A sample of 2.5 ml of cerebrospinal fluid will be taken for analysis of S-100B, NSE, Tau and albumin.

On arrival at OR, standard perioperative monitoring will be established, including an Auditory Evoked Potential (AEP) monitor for anaesthetic depth measurements (AEP Monitor/2, Danmeter, Odense, Denmark) and radial arterial and central venous lines. General anaesthesia is induced with propofol 0.5-1 mg/kg and fentanyl 10 μg/kg. Tracheal intubation will be facilitated using atracurium 0,5 mg/kg. Sevoflurane is used to maintain an anaesthetic depth adjusted to an AAI index of 15-30 as recorded by the AEP monitor. Hemodynamic stability will be obtained by the use of colloidal solution administration, guided by the use of intra-operative transesophageal echocardiography, and norephineprine to maintain a mean arterial pressure above 75 mmHg-Also during CPB. A lumbar puncture will be repeated the first postoperative day repeating the measurement of markers in CSF A certified cardiologist or anaesthesiologist assess focal neurological impairment before and within 24 hours after the procedure.

Transcranial Doppler (TCD) By TCD the right medial cerebral artery (RMCA) will be insonated by the transtemporal approach at a depth of approximately 50 mm using standard criteria. The investigators use a 2 MHz power M-mode TCD monitor (ST3 ©, Spencer Technologies Seattle, WA), with the probe fixed in position using a head frame. The Doppler signals will be continuously monitored and saved to monitor hard drive. Two physicians independently evaluate the TCD data files offline, and identify microembolic signals (MES) using criteria for counting emboli signals on spectral and PMD TCD.