Patient-related factors
1. Risk factors related to patient pathophysiologic status
CPB-related inflammatory response
Intraoperative hypoperfusion
Intraoperative cerebral oxygenation status
Intraoperative anesthetics used during operation
2. Risk factors related to underlying patient status
Perioperative comorbid states (diabetes mellitus, hypertension, atherosclerosis especially in ascending aorta, previous cerebrovascular pathologies)
Preoperative cerebral blood flow (CBF) velocity, which demonstrates cerebral perfusion status (even, preoperative left-sided hypoperfusion could be a risk factor)
Old age
Perioperative sleep status
Perioperative administration of medications
3. Risk factors related to patient social status
Underlying social class and social status
Postoperative administration of rehabilitation care
Underlying level of education
Gender
Ethnic differences
Procedure-related factors (intraoperative and postoperative surgical factors, anesthetic factors, and extracorporeal circulation (ECC) factors)
Using cardiotomy suction (time of using suction during surgery, using cell saver and arterial filter)
Duration of aortic cross clamp
Using hypothermia, optimal rewarming, severity and duration of hypothermia (especially if using DHCA)
Hyperthermia after CPB
Deairing management during surgery
Type of surgery (especially valve surgery or involving the aortic root)
Intraoperative use of epi-aortic scanning by the surgeon for aortic cannulation
Unstable hemodynamic status before, during, or after CPB
Location of the possible side of hypoperfusion during operation (left vs. right carotid system)
Using or avoiding CPB (on pump vs. off pump)
Duration of CPB
Amount of bleeding and the volume of transfused blood
Readmission to the operating theater for control of acute postoperative bleeding
Only one fifth (20 %) of postoperative CNS complications of cardiac surgery occur due to postoperative events
Hyperthermia after CPB
Hypotension
Amount of bleeding and the volume of transfused blood
Readmission to the operating theater for control of acute postoperative bleeding
10.2 Prevention Strategies
10.2.1 Pharmacologic Neuroprotection
Though a number of pharmaceutical agents have been proposed as neuroprotective agents, none has been fully proved yet; however, the following agents have been demonstrated to be effective in suppressing the ischemic penumbra in some studies (Hogue et al. 2007; Nelson et al. 2008; Mitchell et al. 2009; Lombard and Mathew 2010; Benggon et al. 2012; Dabbagh and Rajaei 2012; Zhang et al. 2012; Bruggemans 2013):
Intraoperative lidocaine might have neuroprotective effects through suppressing the inflammatory response in cardiac surgery patients.
Thiopental mainly decreases the embolic load (possibly due to cerebral vasoconstriction).
Propofol might decrease the oxygen consumption during ischemic period.
Postoperative donepezil might have therapeutic (rather than preventive) effects for postoperative cognitive dysfunction.
17β-estradiol might limit ischemic injury of the neuronal tissue in women undergoing cardiac surgery.
In some studies, antagonists of N-methyl-d-aspartate have been demonstrated as neuroprotective agents; among them, anesthetics could be mentioned as the prototype of these drugs used for cardiac surgery patients. Usually, these pharmaceuticals are blamed for their neuroapoptotic effects; however, some agents like xenon and dexmedetomidine may have neuroprotective effects; on the other hand, although ketamine might have adverse neurodevelopmental effects in neonatal animal brain studies, it might be effective in decreasing postoperative neurocognitive dysfunction after cardiac surgery. Magnesium is another agent with potential have anti-inflammatory effects, being an antagonist of NMDA.
Dextromethorphan, nimodipine, aprotinin, remacemide, beta blockers, pexelizumab, and a number of other agents have been proposed; however, none have been conclusive yet.
10.2.2 CPB-Related Equipment
A full description of the CPB-related factors affecting the CNS is discussed in detail in this book in a separate chapter titled “Cardiopulmonary Bypass: Postoperative Effects” (Chap. 12).
10.3 Neurologic Monitoring
Novel and older technologies are used to improve the CNS outcome. These monitoring are used more commonly nowadays. A full description of the neurologic monitoring in cardiac surgery is discussed in detail in this book in a separate chapter titled “Central Nervous System Monitoring” (Chap. 5). However, a brief discussion is presented here. The main currently available CNS monitoring are the following:
Clinical assessment of CNS status and of sedation in postoperative period (Intensive Care Unit)
Classic electroencephalogram (EEG) including multichannel or uni-channel EEG
Monitoring depth of anesthesia
Evoked potentials (including motor evoked potential, somatosensory evoked potential, and auditory evoked potential)
Regional cerebral oximetry (rSO2) by near-infrared spectroscopy technique (NIRS)
Jugular vein oxygen saturation (SjvO2)
Transcranial Doppler (TCD)
Other modes for assessment of cerebral blood flow
A full description of these devices is found in this book in the chapter discussing “Central Nervous System Monitoring” (Chap. 5).
References
Carrascal Y, Casquero E, Gualis J, Di Stefano S, Florez S, Fulquet E, Echevarria JR, Fiz L (2005) Cognitive decline after cardiac surgery: proposal for easy measurement with a new test. Interact Cardiovasc Thorac Surg 4:216–221PubMedCrossRef
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