Neuro Monitoring Lesson 8 PDF

- **Overall goal of neuro anesthesia** = provide sufficient oxygen and glucose to fulfill the brain's metabolic demands - **Perioperative goals** = ensure a favorable supply-demand relationship (of blood and oxygen), prevent herniation, and provide muscle relaxation - Patients wi...

- **Overall goal of neuro anesthesia** = provide sufficient oxygen and glucose to fulfill the brain's metabolic demands - **Perioperative goals** = ensure a favorable supply-demand relationship (of blood and oxygen), prevent herniation, and provide muscle relaxation - Patients with neurologic disease undergoing surgical procedures have an increased risk of hypoxic and ischemic damage to the CNS - Intraoperative monitoring helps improve pt outcomes via early detection and tailoring of the anesthetic/surgical procedure - Routine/standard of care anesthesia monitors = EKG, BP, SPO2, ETCO2, temperature, precordial or esophageal stethoscope - Expanded monitors = art line, CVP, PA, precordial doppler - **3 categories of neurophysiologic monitoring = function, blood flow, and metabolism** - **Monitoring of function = EEG, evoked potentials, electromyography** - **Monitoring of blood flow = CBF and ICP** - Nitrous oxide wash-in - Radioactive xenon clearance - Laser doppler blood flow - ICP only monitors = intraventricular catheter, sub-arachnoid bolt, epidural catheter, fiberoptic parenchymal catheter - **Monitoring of metabolism** - Invasive via intercerebral PO2 electrode - Non-invasive via transcranial cerebral oximetry and jugular venous oximetry - **EEG** = **electroencephalography** = Recording of the electrical activity of the brain from the cerebral cortex - Produced by the pyramidal cells in the cerebral cortex - Summation of excitatory and inhibitory postsynaptic potentials of pyramidal cells - Primarily records cortical (i.e. cortex) activity, little recording of subcortical structures, spinal cord, cranial nerves, and peripheral nerves - Dependent on an adequate supply of oxygen and glucose - Can be monitored from the scalp and forehead - Scalp is an electrically neutral area - Electrodes can be taped or small needles - International 10-20 system is a standardized way to place EEG electrodes - Distance is 10 or 20% of skull circumference - Even numbers are in the right hemisphere - Odd numbers are in the left hemisphere - Nasion = depressed area between eyes - Inion = lowest point of the skull - **Beta waves** = high frequency, Low amplitude waves that are dominant while awake - **Alpha waves** = medium frequency, higher amplitude waves that are seen in an awake but restful state (i.e. relaxed) - **Theta waves** = low frequency and not associated with any set condition in adults. Associated with children during normal sleep - **Delta wave** = low frequency, high amplitude waves that signify depressed functions consistent with deep coma, anesthesia, hypoxia - EEG reflects the brain's wakefulness and metabolic activity - Depression of EEG can be caused by decrease in blood flow, oxygen, or glucose - **Awake EEG are predominantly beta wave activity with high frequency and low amplitude waves** - Hypoxia/ischemia - Transient increase in beta activity as a compensation mechanism as the brain increases CBF and metabolic rate to compensate for hypoxia/ischemia - Slow theta waves - Disappearance of beta waves - Delta waves with low amplitude - Abnormal EEG patterns - Generalized slowing - Focal or localized slow activity - Period pattens e.g. burst suppression, background suppression, electro-cerebral inactivity (ECI) - Spikes = epileptiform patterns - Spike and wave complexes indicate epilepsy - Ischemia/hypoxia and EEG - Continued insult can progress to suppression of electrical activity then burst suppression - Then complete isoelectric EEG which is indicative of irreversible brain damage - **Burst suppression** = EEG pattern characterized by periods of high voltage electrical activity alternating with periods of no brain activity - Causes are anesthesia (especially in elderly due to slow metabolism), hypothermia \