Cerebral Oxygen Saturation Monitoring In Cardiac Surgery (COSMICS) (COSMICS)

A Multicenter, Randomized, Controlled Clinical Trial of Cerebral Oxygen Saturation Monitoring In Cardiac Surgery (COSMICS)

Neurological dysfunction continues to be one of the complications of considerable concern in patients undergoing cardiac surgery. It was previously reported in the literature, that cerebral oxygen desaturation during cardiac surgery was associated with an increased incidence of cognitive impairment. This study aims to determine whether continuous monitoring of cerebral oximetry improves the neurocognitive outcome in coronary artery bypass surgery when associated with predetermined intervention protocol to optimize cerebral oxygenation.

Despite all the progress over the last decades regarding the improvement of the perioperative care of patients with heart disease and the development of new surgical techniques, neurological dysfunction continues to be one of the complications of the greatest concern in patients undergoing cardiac surgery with cardiopulmonary bypass. Brain injury can manifest itself through permanent or temporary injury, contributing to the increase in-hospital mortality, in the length of stay in intensive care, in the length of hospital stay, to a higher incidence of motor dysfunction requiring rehabilitation, and consequently, to reduced quality of life. Even though the causes of brain injury are multifactorial, perioperative cerebral hypoperfusion, tissue hypoxia, and thromboembolic events are among the main factors related to neurological dysfunction. Several clinical studies have indicated an association between cerebral desaturation and the increase of neurological complications. Cerebral oximetry monitoring using near-infrared spectroscopy (NIRS) is a non-invasive technique used to estimate regional cerebral oxygen saturation (rSO2) and has been associated with diminishing the incidence of neurological complications. There is no consensus in the literature about its real benefit, mainly due to the absence of well-designed scientific studies that demonstrate that cerebral desaturation associated with intervention measures to improve rSO2, are related to the prevention of neurological dysfunction in adult cardiac surgery. The study hypothesis evaluates whether continuous monitoring of cerebral oximetry improves the neurocognitive outcome in coronary artery bypass surgery when associated with early interventions to optimize rSO2.

Patients will be monitored with cerebral oximetry using INVOS 5100 monitor (Covidien, Boulder, CO), with electrodes applied bilaterally in the frontal region. Following the placement of the electrodes, the baseline records HR, blood pressure, rSO2, and peripheral O2 saturation (SPO2) will be recorded following 1 minute of electrode placement and the proper verification of the signal on the monitor. Later, during the surgery, if the rSO2 reaches levels below 15% of the baseline values or below 50% in absolute value for over 30 seconds, protocol-based interventions will be performed in the intervention group to return the oximeter to baseline values. The alarm on the equipment should be programmed to signal values below 15% of the baseline values.

Patients will be masked concerning the allocation group. The anesthesiologist responsible for conducting the case will not be involved in the application of the neurocognitive tests, nor will he be aware of the test results. Investigators who apply the tests will be covered up by the patient allocation group.

The following procedures should be performed sequentially in the event of cerebral desaturation after 30 seconds: The positioning of the head, the presence of facial plethora, and bad position of catheters should be corrected; In case of arterial hypotension, the causal factors should be assessed and treated; In the presence of arterial hypoxemia, the causal factors should be assessed and treated to maintain a PaO2 > 150 mmHg; In the presence of hypercapnia, adjust the ventilation parameters avoiding hyperventilation; In the presence of anemia, the causal factors should be assessed, and the decision to undergo transfusion should also take into consideration the presence of tissue hypoperfusion; In cases of SvO2 below 70% and signs of hemodynamic instability, optimize fluid replacement and ventricular global contractility; Assess the increase of brain consumption of O2, avoiding the superficial level of anesthesia, hyperthermia, and tremors.

Patients will be treated according to the attending anesthesiologist, without the monitoring of cerebral oximetry, but to maintain a heart rate between 70 - 100 bpm, lactate levels <3 mmol/L and urine output> 0.5mL/Kg/h. In case of arterial hypotension the causal factors should be assessed and treated; in case of SvO2 below 70% and signs of hemodynamic instability, optimize volume replacement and global ventricular contractility through inotropic agents (epinephrine, dobutamine or milrinone); in the presence of anemia (Hb <6 to 7g/dL during CPB or Hb <8g/dL in the pre-CPB or post-CPB period), the causal factors should be assessed and the decision to transfuse should also take into account the presence of hypoperfusion tissue (increased lactate, low SvO2, acidosis); in episodes of bradycardia with hemodynamic instability, atropine may be used.

In the intervention group, an alarm threshold below 15% of the baseline rSO2 value will be established. Based on the predetermined algorithm the rSO2 will be maintained at or above 85% of the baseline measurements. If the rSO2 reaches levels below 15% of the baseline values or below 50% in absolute value for over 30 seconds, protocol-based interventions will be performed to restore rSO2 to baseline levels.

Delirium assessment CAM-ICU preoperatively (baseline) and postoperatively twice a day during the first seven days or until discharge

Inclusion Criteria: Age 60 or older Elective coronary artery bypass graft surgery using cardiopulmonary bypass Preoperative cognitive assessment by means of Mini-Mental State Examination (MMSE) test, greater than or equal to 24 Signed informed consent Exclusion Criteria: Patients with focal neurologic deficit Carotid artery stenosis greater than 70% Patients with pre-existing cognitive dysfunction Patients with psychotic disorders History of allergy to adhesive part of the electrode History of craniofacial surgery

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