Cerebral Perfusion Monitoring With Transpharyngeal Ultrasonography

Study Overview
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Brief Summary
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This prospective observational pilot study investigates transpharyngeal ultrasonography (TPU) as an additional neuromonitoring strategy to assess cerebral perfusion during on-pump cardiovascular surgery. In the first part of the study the investigators will investigate the feasibility of TPU for visualization of aortic arch branches including the innominate and the carotid arteries in twenty patients undergoing coronary artery bypass grafting with extracorporeal circulation (cohort 1.). In the second part the investigators plan to adopt the investigators previous experiences on TPU to a selected population of twelve patients undergoing ascending aortic and/or arch repair in deep hypothermic circulatory arrest (DHCA, cohort 2.). In contrast to cohort 1., patients in cohort 2. are exposed intraoperatively to intermittent cerebral perfusion stops or reductions due to surgical procedure, perfusion technique and their underlying disease (aortic dissection or aortic aneurysm). The investigators hypothesize that cerebral perfusion monitoring using TPU as a non-invasive technique provides a simple and real-time adjunct to assess blood flow velocity in the extracranial cephalic vessels with Doppler ultrasound. Especially in aortic arch surgery with its inherent risk of cerebral hypoperfusion TPU might be a valuable adjunct to routine.

Detailed Description
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Background Cerebral hypo- or malperfusion during cardiovascular surgery can lead to grave consequences including transient cerebral ischemia or stroke impairing patient's daily life and affect surgical outcome. For this reason a multimodal neuromonitoring strategy using a variety of devices (evoked potentials, near-infrared spectroscopy, transcranial Doppler ultrasonography) with different technologies has been recommended by medical societies. These techniques have various limitations and cannot be used in all clinical situations. In contrast, transpharyngeal ultrasonography (TPU) represents a simple and readily available technique: the transesophageal echocardiography probe, routinely placed in most cardiac surgical patients for monitoring and assessment of surgical results, will be withdrawn into the upper esophagus making the visualization of supraaortic branches possible. To date, there are several reports about imaging of aortic arch branches using TPU. The utility of this technique, however, for systematic cerebrovascular monitoring has not have been investigated so far. Objective The aim of this study is to investigate TPU as a cerebrovascular monitoring adjunct in two cohorts of on-pump cardiac surgery procedures. Clinical feasibility and diagnostic accuracy of antegrade carotid flow detection are compared to the established reference methods of Duplex sonography and transcranial Doppler ultrasound. Methods All patients receive anesthetic and surgical management according to institutional standards. Patient enrollment in the study occurs consecutively and unblinded for surgical procedure. All patients receive TPU, Duplex sonography and transcranial Doppler examination after anesthesia induction preoperatively, during extracorporeal circulation and after weaning from cardiopulmonary bypass. In addition, the patients in cohort 2.(ascending aortic repair with DHCA) receive above mentioned noninvasive ultrasound / Doppler measurements also during the period of DHCA with and without antegrade cerebral perfusion. Image acquisition and data extraction are conducted by different persons to avoid investigator-related bias.

Official Title
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Monitoring the Brain in On-pump Cardiovascular Surgery: The Role of Transpharyngeal Ultrasonography as a Non-invasive Adjunct to Assess Cerebral Perfusion

Conditions
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Cardiopulmonary Bypass

Intervention / Treatment
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* Device: Transpharyngeal ultrasonography
* Device: Duplex sonography


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Signed informed consent Cardiopulmonary bypass procedure (normo-(group 1) or hypothermic (group 2)) Exclusion Criteria Contraindication for transesophageal echocardiography Carotid artery stenosis

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Cardiopulmonary bypass group<br>Patients requiring normothermic (or mild hypothermic) cardiopulmonary bypass. | Device: Transpharyngeal ultrasonography<br>* Transpharyngeal Dopplerultrasonography (Device: iE33 xMatrix Philips). Assessment of cerebral blood flow by detection of blood flow velocities in the extracranial carotid arteries.<br>Device: Duplex sonography<br>* Assessment of cerebral blood flow by detection of blood flow velocities in the extracranial carotid and middle cerebral arteries during coronary artery bypass grafting.<br>|
| Hypothermic Cardiopulmonary Bypass Group<br>Patients requiring (deep) hypothermic cardiopulmonary bypass. | Device: Transpharyngeal ultrasonography<br>* Transpharyngeal Dopplerultrasonography (Device: iE33 xMatrix Philips). Assessment of cerebral blood flow by detection of blood flow velocities in the extracranial carotid arteries.<br>Device: Duplex sonography<br>* Assessment of cerebral blood flow by detection of blood flow velocities in the extracranial carotid and middle cerebral arteries during coronary artery bypass grafting.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| accuracy of cerebral flow velocity measurement | Cerebral blood flow velocity measurements will be performed using the pulsed wave Doppler technique. Doppler peak flow velocities (obtained at the same intraoperative phase and at the same time) will be compared between the different Doppler techniques. | intraoperative phase, expected to be ca. 4 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| clinical feasibility | Clinical feasibility will be assessed by analyzing the accuracy of data concordance, i.e. location of cerebral blood vessel, blood flow velocity and cerebral vessel area between the different Doppler techniques. Data will be plotted using Bland-Altman analysis. | intraoperative phase, expected to be ca. 4 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Cardiac surgery, Echocardiography, Cerebral perfusion, Intraoperative period