Cerebral Oximetry and Neurocognitive Functions in Cardiosurgical Patients

Influence of Intraoperative Monitoring of Cerebral Oximetry on Neurocognitive Function After Coronary Artery Bypass Surgery: Randomized, Prospective Study

It is previously reported that the cerebral oxygen desaturation during cardiac surgery is associated with an increased incidence of cognitive impairment. The aim of this study is to determine whether intraoperative monitoring and predetermined interventions protocol to improve cerebral oxygenation during coronary artery bypass surgery provides benefits in neurocognitive functions.

Neurologic complications are major cause of morbidity following coronary artery bypass graft surgery. The neurologic injuries range in severity from subclinical cognitive changes to fatal brain injury and death. These complications represent a big impact on overall morbidity, and mortality in association with increased costs and length of hospital stay. The social impact is also very important with consequences on patients' quality of life. Several studies reported the incidence of cognitive decline after cardiac surgery that ranges from 30 to 80%. The most common etiologies are embolization and hypoperfusion of the brain. The In Vivo Optical Spectroscopy (INVOS) system uses near-infrared spectroscopy (NIRS) and provides noninvasive and continuous information on changes in regional oxygen saturation of blood in the brain (rSO2). When rSO2 decline occurs it can be responded with simple interventions to prevent a brain injury. These interventions include: repositioning of the head or perfusion cannulae, increasing arterial carbon dioxide tension, increasing oxygen inspiration concentration, increasing arterial blood pressure, adjusting pump flow rate, temperature decreasing, increasing of anesthetic depth and blood transfusion. Recent studies reported that intraoperative cerebral oxygen desaturation is associated with early postoperative neuropsychological dysfunction in patients undergoing cardiac surgery. Neurocognitive function can be assessed with battery of standardized neurocognitive tests. Mini Mental State Examination, Color Trail Test, Grooved Pegboard Test are easy to perform bedside tests that test orientation, registration, attention, calculation, recall, language and complex visual-motor coordination.

INVOS : Cerebral oxygenation (rSO2) monitoring with INVOS. If rSO2 decreased for more than 20% from patient's baseline value, simple interventions were performed to prevent brain injury. These interventions included: repositioning of head or perfusion cannulae, increasing arterial carbon dioxide tension, increasing oxygen inspiration concentration, increasing arterial blood pressure, adjusting pump flow rate, temperature decreasing, increasing of anesthetic depth and blood transfusion.

The CONTROL arm did not have INVOS or any other cerebral oxygenation monitoring, so interventions to control cerebral oxygenation were not performed.

Monitoring cerebral oxygenation (rSO2) with INVOS. When rSO2 decline occur it can be responded with simple interventions to prevent a brain injury including: repositioning of the head or perfusion cannulae to avoid mechanical obstruction of cerebral blood flow, increasing arterial carbon dioxide tension within normal referent values, increasing oxygen inspiration concentration to maintain adequate tissue oxygen saturation, increasing arterial blood pressure, pump flow rate and cardiac index, temperature decreasing and increasing of anesthetic depth to reduce cerebral oxygen consumption and blood transfusion if hematocrit decreases below 22%. None of the interventions are outside the range of good clinical practice.

Difference in Incidence of Cognitive Impairment Between Groups. Change Between Preoperative and Postoperative Cognitive Function Was Assessed by Performing Standardized Neurocognitive Tests.

The Mini-Mental State Examination (MMSE) total score is calculated by summing the item scores across several aspects of cognition. The maximum possible total score is 30 points. Color Trials Test (CTT) measures sustained visual attention, visual scanning and graphomotor skills. The examiner records the length of time (in seconds) required by the patient to rapidly draw a line connecting the circles numbered 1 through 25 in consecutive order. Grooved-Pegboard test (GP test) is manipulative dexterity test that contains twenty-five holes with randomly positioned slots and pegs which have a key along one side. Pegs must be rotated to match the hole before they can be inserted. The examiner records the time in seconds. Cognitive impairment was defined as a decline in postoperative performance in one or more tests: decrease of MMSE score three points or more from baseline and decrease of one standard deviation or more in performance on CTT 1 and GP tests

Evidence of Coma, Stupor, Cerebral Insult, Delirium, Ventilation Longer Than 24 Hours, Myocardial Infarction, Atrial Fibrillation, Dialysis, Reoperation for Bleeding, Infection, Hospital Stay > 7 Days

Inclusion Criteria: All patients with coronary artery disease undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass Exclusion Criteria: Who refuse to participate Previous stroke Preexisting psychiatric disease Significant carotid stenosis Ejection fraction below 25% Reoperations Emergent surgery Dialysis

Colak Z, Borojevic M, Bogovic A, Ivancan V, Biocina B, Majeric-Kogler V. Influence of intraoperative cerebral oximetry monitoring on neurocognitive function after coronary artery bypass surgery: a randomized, prospective study. Eur J Cardiothorac Surg. 2015 Mar;47(3):447-54. doi: 10.1093/ejcts/ezu193. Epub 2014 May 7.