Prospective Analysis of Regional Cerebral Perfusion Using Head Ultrasound and Multi-source-detector Near Infrared Spectroscopy (NIRS) Imaging

Purpose: There are 4 objectives for this study.

1. To determine if the use of cranial ultrasound and multi-source-detector near infrared spectroscopy can identify alterations in cerebral perfusion that are associated with long-term neurologic dysfunction.
2. Evaluate whether changes in resistive indices as determined by cranial ultrasound after cardiopulmonary bypass are associated with major neurologic dysfunction.
3. Describe regional changes in brain tissue oxygenation during selective cerebral perfusion using near-infrared spectroscopy and determine if there are critical thresholds that correlate with poor neurologic outcomes. To accomplish this, we will describe differences in cerebral blood flow and oxygenation as related to structural anatomy of the heart. Specifically, we will compare single ventricle and two ventricle hearts with regards to use of cardiopulmonary bypass with or without selective cerebral perfusion. We will also determine if a prolonged reduction in cerebral oxygenation intraoperatively is associated with ultrasound-diagnosed periventricular leukomalacia at discharge.
4. Prospectively collect patients' DNA to determine if differences exist in neurologic outcomes that are associated with genetic variation. Specifically, we will look at simple karyotyping, single nucleotide polymorphisms, and copy number variation differences between patients. This DNA will be collected and stored for future comparison with other children with congenital heart disease who undergo neurodevelopmental testing.

Background:

The incidence of congenital heart disease is at least 10 per 1000 live born children and children with congenital heart disease are at high risk for developing neurologic abnormalities1. Patients with a single ventricle have a mean full scale IQ between 89-97 and the incidence of severe mental retardation in hypoplastic left heart syndrome is as high as 18%2, 3. The factors influencing this risk are multiple and include preoperative, intraoperative, and postoperative events. One major risk factor is the use of deep hypothermic circulatory arrest (DHCA), which has historically been employed to obtain a bloodless operating field for aortic arch reconstruction. Since it is becoming increasingly evident that there is no safe duration of DHCA, newly developed strategies are aimed at maximizing cerebral blood flow and thereby improving neurologic outcomes4-7. One such strategy that has been widely employed is selective cerebral perfusion (SCP), which increases cerebral blood flow via a dedicated brain cannula advanced into the right common carotid artery during aortic arch reconstruction.8 This technique, which decreases the period of cerebral ischemia, has been shown in animal models to improve neurologic outcome, but similar studies have not been performed in humans9.

It is known that cerebral vascular resistance is increased after DHCA and it has been suggested that SCP may contribute to post-bypass cerebral vascular hypertension10, 11. Single channel near-infrared spectroscopy (NIRS) measurements have been shown to correlate with cerebral blood flow in animal models, but evaluation of SCP with multi-site-detector NIRS has not been performed, and it is unknown if there are regional oxygenation differences12, 13. This study would provide important information on the cerebral blood flow characteristics of regional tissue, particularly as it relates to unilateral perfusion as well as differences in patients with complex anatomy and compromised cerebral blood flow.