Brain Monitoring and Protection During Pediatric Cardiac Surgery

Abstract

With advances in medical care, survival after cardiac surgery for congenital heart disease has dramatically improved, and attention is increasingly focused on long-term functional morbidities, especially neurodevelopmental outcomes, with their profound consequences to patients and society. There are multiple reasons for concern about brain injury. Some cardiac defects are associated with brain anomalies and altered cerebral blood flow regulation. Brain imaging studies have demonstrated that injury to gray and white matter is quite frequent before heart surgery in neonates. Cardiopulmonary bypass and deep hypothermic circulatory arrest are associated with short- and longer-term adverse neurologic outcome. Additional brain injury can occur during the patient's recovery from surgery. Strategies to optimize neurologic outcome continue to evolve. With new technological developments, perioperative neurologic monitoring of small children has become easier, and data suggest these modalities usefully identify adverse neurologic events and might predict outcome. Monitoring methods to be discussed include processed electroencephalography, near infrared spectroscopy, and transcranial Doppler ultrasound. Alternative perfusion techniques to deep hypothermic circulatory arrest have been developed, such as regional antegrade cerebral perfusion during cardiopulmonary bypass. Other neuroprotective strategies employed during open-heart surgery include temperature regulation, acid-base management, degree of hemodilution, blood glucose control and anti-inflammatory therapies. Evidence of the impact of these measures on neurologic outcome is examined, and deficiencies in our current understanding of neurologic function in children with congenital heart disease are identified.

Use of near‐infrared spectroscopy to identify trends in regional cerebral oxygen saturation in horses

“…An rSO 2 value less than 50% or a relative decrease of ≥ 20% compared to pre-induction baseline values is considered clinically significant, and has been associated with focal cerebral ischaemia in human patients 12,36,51 . Decreasing rSO 2 values are thought to reflect shifts in the delicate balance between cerebral O 2 supply and demand, suggestive of cerebral hypoxia; and indicate the need for interventions aimed at improving cerebral perfusion 33,53 .…”

“…The ideal neurophysiological monitor should be non-invasive and provide real-time, continuous, objective and rapid assessment of cerebral perfusion and function 12,35,36 .…”

“…Not only does EEG have a low sensitivity for the detection of cerebral ischaemia (false negative rate of 40.6%) but also the interpretation of an EEG trace requires a trained neurophysiologist 12,36 . Due to these limitations, EEG is unlikely to be used routinely in veterinary medicine.…”

“…By continuously and non-invasively measuring changes in the velocity of blood flow through both the intracranial arteries and veins, TCD is not only able to instantly recognise alterations in cerebral blood flow, but also allows the detection of clinically significant microemboli 12,13,36,38,51 . However, due to the anatomical structure of the horse's skull it is not possible to adequately image the intracranial vessels, therefore rendering TCD of very limited use in equine medicine.…”

Signal Processing for Non-Invasive Brain Biomarkers of Sensorimotor Performance and Brain Monitoring

“…Recently, it has been also suggested that measurements of the skin conductance was a better tool to monitor nociceptive stimulation and pain than heart rate and blood pressure (Storm et al, 2008). Another important family of functional biomarkers includes status measurements of brain functions in order to monitor and interpret neural activity, identify specific neurological events and predict outcomes (e.g., Gentili et al, 2008;Guarracino, 2008;Hatfield et al, 2004;Irani et al, 2007;Tuner et al, 2009;van Putten et al, 2005;Williams & Ramamoorthy, 2007). These brain indicators, or brain biomarkers, can be derived from signals recorded by means of invasive acquisition techniques such as implantable microelectrodes arrays or electrocorticography (Schalk et al, 2008), or, alternatively, non-invasive techniques such as electroencephalography (EEG), magnetoencephalography (MEG), functional magnetic resonance imaging (fMRI) or emerging neuroimaging technologies such as functional near infrared spectroscopy (fNIRS) (Irani et al, 2007;Parasuraman & Rizzo, 2007).…”