Title: 25. Neurophysiology
125. Neurophysiology Anesthesia
2CEREBRAL PHYSIOLOGY
- CEREBRAL METABOLISM
- ?? total body oygen? 20? ????
- ?? 60? ATP? ????? ????
- NEURONAL ELECTRICAL activity
- hippocampus? cerebellum? ?? ??
- irreversible cellular injury?????
- cerebral perfusion 10?
- blood flow 3-8?
- primary energy source glucose
- hypoglycemia hypoxia?? ??
- hyperglycemia cerebral acidosis cellular
injury - --gt global focal
hypoxic injury   Â
3CEREBRAL PHYSIOLOGY
- CEREBRAL BLOOD FLOW
- CBF ? metabolic activity ? ??? flow??? cerebral
metabolic rate????? - Â Â
- REGULATION OF CEREBRAL BLOOD FLOW (1)
- Â Â 1.Cerebral Perfusion Pressure(CPP)
- Â Â Â Â Â CPP MAP ICP (or CVP)
- Â Â Â Â Â Â ?, CVP? ICP?? ??? ?? ? CVP??
- Â Â Â Â Â CPP? 80-100mmHg
- Â Â Â Â Â ?? ICP? 10mmHg?? ??
- Â Â Â Â Â ???? CCP? MAP?? ????
- Â Â Â Â Â Â
- Â Â 2.Autoregulation
- Â Â Â Â Â ???? ???????? ??? ? ???? blood flow? ? ???
?? - Â Â Â Â Â ?? ?? CPP? ?? ?? cerebral vasodilation? ???
?? - Â Â Â Â Â CBF ? MAP 60160mmHg????? ?????
- Â Â Â Â Â ???? ?? flow? pressure ? ??? ??
- Â Â Â Â Â BBB? disrupt??? cerebral edema?? hemorrhage?
?? ??
4CEREBRAL PHYSIOLOGY
- REGULATION OF CEREBRAL BLOOD FLOW (2)
- 3.Extrinsic Mechanism
- Â Â Â Respiratory Gas Tensions
- Â Â Â Â Â Â ?? PaCO2??, CBF ??? ??? ?? ? ???
- Â Â Â Â Â Â 20-80mmHg????, CBF? PaCO2? ??
-       ????? CSF ? ? ??? pH? ??? ???
- Â Â Â Â Â Â Â
- Â Â Â Â Temperature
- Â Â Â Â Â Â Â CBF ? ??1?? ??? ?? 5-7? ???
- Â Â Â Â Â Â Â Hypothermia CMR? CBF? ??
- Â Â Â Â Â Â Â
- Â Â Â Â Viscosity
- Â Â Â Â Â Â Â Â viscosity? ????? hematocrit ??
- Â Â Â Â Â Â Â Â ????? CBF ? ? ??? ??
- Autonomic influences
- Â Â Â Â Â Â Â Â brain injury? stroke? vasospasm? ??? ???
??
5CEREBRAL PHYSIOLOGY
- Â Â Â BLOOD-BRAIN BARRIER
- ?? ???? vascular endothelial cell???
junction?? - Â Â
- Â lipid barrier?? lipid soluble substances?
????? - Â Â Â ionized??large molecular weight ? ?? ??? ????
- Â Â Â ? ??,charge,lipid solubility,??? protein
binding? ??? ???? - Â Â
- Â CO2, O2, lipid soluble substances(???? ????)?
????? - Â
- Â water freely across
- Â
- Â electrolyte? osmolality??? ????, sodium??
glucose?? ??? ????  -  mannitol?? BBB?? ??? water content? ???? ??Â
6CEREBRAL PHYSIOLOGY
- Â Â
- CEREBROSPINAL FLUID
- CNS ? trauma??? ??
- Â Â Â ???? ? 21mL/h ????
- ??? ?150ml????
7CEREBRAL PHYSIOLOGY
- Â Â Â INTRACRANIAL PRESSURE
- Cranial vault? rigid structure?? brain(80),
blood(12), CSF(8)? ?? - Â Â ???? ???? ????? ???? ??? ?? ICP ? ????
- Â Â ICP? ??? supratentorial CSF pressure? ???
- lateral ventricle?? cerebral cortex??
???? ?? 10mmHg?? - Â Â Â Â ??? lumbar CSF pressure? ????? ??
- Â Â Â major compensatory mechanism
- Â Â Â Â (1) initial displacement of CSF (from
cranial to spinal compartment) - Â Â Â Â (2) CSF ? ?? ??
- Â Â Â Â (3) CSF ?? ??
- Â Â Â Â (4) total cerebral blood volume? ??
-    ??? compliance? arterial blood pressure? Â
- PaCO2? ??? ??
????? - Â Â Â Â blood pressure? ???
vasoconstriction, vasodilation
8EFFECT OF ANESTHETIC AGENTS ON CEREBRAL PHYSIOLOGY
- EFFECT OF INHALATION AGENTS (1)
- 1.Volatile Anesthetics
- Â Â Â Cerebral Metabolic Rate
- Â Â Â Â Â dose-dependent ?? ??
- Â Â Â Â Â Isoflurane? ?? ??(50?? ??)
- Â Â Â Â Â Â Â Â
- Â Â Â Cerebral Blood Flow Volume
- Â Â Â Â Â cerebral blood vessels? dilatation,
autoregulation? impair by dose-dependent - Â Â Â Â Â halothane CBF ? ?? ? ?? (200?? ??)
- Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â cf.Isoflurane? 20??
- Â Â Â Â Â time-dependent 2-5???? ????? ???
- blood flow? ????
???? ???? - Â Â Â Â Â hyperventilation (hypocapnia) ? ?????? CBF ?
?????? - Â Â Â Â Â Â Â
           ????? ??? ???? -gtICP ??? ?? -                Â
- Â Â
- Â Â Â Â Â
9EFFECT OF ANESTHETIC AGENTS ON CEREBRAL PHYSIOLOGY
- EFFECT OF INHALATION AGENTS (2)
- Cerebrospinal Fluid Dynamics
- Â Â Â Â Â Â Â Â CSF? ??? ??? ??
- Â Â Â Â Â Â Â Â Isoflurane ??? ??
- Â Intracranial Pressure
- Â Â Â Â Â Â Â ?????? ????? CBF ? ?????
- Â Â Â Â Â Â Â ??? CSF dynamics, arterial CO2 tension?
????? - Â Â Â Â Â Â Â choice - isofluane
- 2.Nitrous Oxide
- Â Â Â Â Â intravenous agent? ??? minimal effect on
CBF, ?, and ICP - Â Â Â Â Â Â ?? ??? ICP??
10EFFECT OF ANESTHETIC AGENTS ON CEREBRAL PHYSIOLOGY
- EFFECT OF INTRAVENOUS AGENTS (1)
- 1.Induction Agents (1)
- Â Â Â Ketamine? ????? ?? ?????? CMR, CBF? ?? ???
??? - Â Â Â Â Â Â Â Â Â ??? ?????
- Â Â Â cerebral autoregulation? CO2???? ????
- Â Â Â ???, blood flow? metabolic rate? parallel??
- Â Â Â Â Â
- Â Â Â Barbiturates
- Â Â Â Â Â Â CNS ? 4?? ??
- Â Â Â Â Â Â Â Â Â (1) hypnosis
- Â Â Â Â Â Â Â Â Â (2) CMR? ??
- Â Â Â Â Â Â Â Â Â (3) CBF ? ????? cerebral vascular
resistance? ?? - Â Â Â Â Â Â Â Â Â (4) anticonvulsant activity
- Â Â Â Â Â Â CMR, CBF? ??? EEG? isoelectric????
dose-dependent (?? 50??) -      barbiturate-induced vasoconstriction
- -gtnormal? ????
ishemia? ???? ?????? - Â Â Â Â Â Â CSF? ??? ?? -gt lower ICP
- Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
11EFFECT OF ANESTHETIC AGENTS ON CEREBRAL PHYSIOLOGY
- EFFECT OF INTRAVENOUS AGENTS (2)
- 1.Induction Agents (2)
- Opioids
- Â Â Â Â Â Â CBF , CMR ,ICP? ????? ??????
- Â Â Â Â Â Â ??????? CO2? ????
- Â Etomidate
- Â Â Â Â Â Â CMR CBF ICP ??
- Â Â Â Â Â Â Â induction ? myoclonic movement ?? ???
?????? - Â Â Â Â Â Â Â (?? seizure?? ????)
- Â Â Â Â Â Â Â epilepsy Hx?????? avoid
- Â Propofol
- Â Â Â Â Â Â Â CBF CMR ??
- Â Â Â Â Â Â Â Anticonvulant activity? ??
- Â Â Â Â Â Â Â short elimination half-life
- Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
12EFFECT OF ANESTHETIC AGENTS ON CEREBRAL PHYSIOLOGY
- EFFECT OF INTRAVENOUS AGENTS (3)
- 1.Induction Agents (3)
- Benzodiazepines
- Â Â Â Â Â Â Â barbiturates, etomidate, and propofol ???
????, - CBF CMR ? ??
- Â Â Â Â Â Â Â anticonvulsant properties
- Â Â Â Â Â Â Â midazolam? short half-life??? choice???
- Â Â Â Â Â Â Â ?? ???? unstable ???? CPP? ????
-
emergence? ????              -      Ketamine
- Â Â Â Â Â Â Â cerebral vasculature? ????? CBF ? ?????
- Â Â Â Â Â Â Â seizure activity? ???
- Â Â Â Â Â Â Â Intracranial compliance? ????? ??? ???
- CBF ????? ICP ??
- Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
13EFFECT OF ANESTHETIC AGENTS ON CEREBRAL PHYSIOLOGY
- EFFECT OF INTRAVENOUS AGENTS (4)
- 2.Anesthetic Adjuncts
- Â Â Â Â Â Â Iv lidocaine ??????? ??? CMR CBF ICP??
- Â Â Â Â systolic toxicity?
seizures ???? ?? repeat dose?? - Â 3.Vadopressors
- Â Â Â Â Â MAP? 50-60mmHg?? ?? 150-160mmHg??? ?? CBF ??
- Â Â Â Â Â
- Â 4.Vasoilators
- Â Â Â Â Â Hypotension? ?? ??, ???? vasodilators?
cerebral vasodilation? - Â Â Â Â Â Â ???? CBF ? dose-relate?? ?? ???
- Â Â Â Â Â Â
- Â 5.Neuromuscular Blocking Agents
- Â Â Â Â Â succinylcholine - ?? ??
- Â Â Â Â Â (thiopental or propofol? ???,
hyperventilation?? ??? ??) - Â Â Â Â Â ICP? ??? ?? ??? ???????
- Â Â Â Â Â hypercapnia?? hypoxemia? acute ?? ?? ? ? ??
- Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
14PHYSIOLOGY OF BRAIN PROTECTION
- PATHOPHYSIOLOGY OF CEREBRAL ISCHEMIA
- Â ?? ?? ??? glucose metabolism??? ischemic injury?
???? - ex. interruption of cerebral perfusion,
metabolic substrate, or hypoxemia - STRATEGIESÂ FOR BRAIN PROTECTION (1)
- Â Â 1.Hypothermia
- Â Â Â Â focal and global ischemia? most effective
method - Â Â Â Â profound hypothermia? ?? total circulatory
arrest??? - Â Â Â Â Â neurologic impairment?? 1???? ????
- Â Â Â Â basal and electrical metabolic requirements?
????? - Â Â Â Â mild hypothermia(33-35?) - some protective
effect? ??? - Â Â Â Â Â
adverse effect? profound hypothermia?? ??
15PHYSIOLOGY OF BRAIN PROTECTION
- STRATEGIESÂ FOR BRAIN PROTECTION (2)
- Â Â 2. Anesthetic Agents
- Â Â Â Â barbiturates,etomidate,propofol, and
isoflurane - Â Â Â Â Â Â - complete electrical silence of the
brain - Â Â Â Â Â Â Â Â eliminate the metabolic cost of
electrical activity - Â Â Â Â barbiturates produce inverse steal
- Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â reduce cerebral edema and
calcium influx - Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â inhibit free radical
formation - Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â blockade of sodium
channels - Â Â Â Â Â Â Â Â Â Â -- effective brain
protection in focal ischemia - Â Â Â Â Â anesthetic agents? global ischemia?? ??? ??
(only hypothermia) - Â
- 3. Specific Adjuncts
- Â Â Â Â calcium channel blockers
- Â Â Â Â Â Â Â cerebral vasodilation but CBF ??
- Â Â Â Â Â Â Â neurologic outcome? ?? ???? ???
16PHYSIOLOGY OF BRAIN PROTECTION
- STRATEGIESÂ FOR BRAIN PROTECTION (3)
- Â 4.General Measures
- Â Â Â Â ??? CPP??? ????
- Â Â Â Â Â Â Â 1) arterial blood pressure normal or
slight elevated - Â Â Â Â Â Â Â 2) avoid - venous and ICP ??
- Â Â Â Â Â Â Â 3) oxygen carrying capacity
- normal arterial tension
hematocrit 30 - Â
- Â Hyperglycemia neurologic injury ??
- Â Â Â Â normocarbia?? hypo? cerebral
vasoconstriction -gt ischemia ?? - Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â hyper? steal
phenomena ?? acidosis ??
 Â
17PHYSIOLOGY OF BRAIN PROTECTION
- EFFECT OF ANESTHESIA
- ON ELECTROPHYSIOLOGICAL MONITORING
- CNS ? ??? ??
- ?? EEG ?? Evoked potentials??
- anesthetic depth- dose- related change
- Â blood pressure, body temperature,
- respiratorygas tension? ????
- Â Â recording? bilateral,??? event?
- ???? ???? ??? ??
18PHYSIOLOGY OF BRAIN PROTECTION
- ELECTROENCEPHALOGRAPHY (1)
- EEG cerebral perfusion? ??
- Â carotid endarterectomy(CEA), controlled
hypotension ? ?? - Â Â ???? ?????? biphasic pattern? ????
- Â Â Â dose-dependent depression ? ?? initial
activation? EEG?? ???? -  Â
- 1.Inhalation Anesthetics
- Â Â Â Â Isoflurane high dose(1-2 MAC)???
isoelectric EEG? ???? ??? ?? - Â Â Â Â Sevo and Des burst suppression pattern at
high dose - Â 2.Intravenous Agents
- Â Â Â Â Benzodiazepines typicalbiphasic pattern on
EEG - Â Â Â Â Barbiturates, etomidate, and propofol
typical biphasic pattern - Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â high dose??? burst
suppression and electrical silence
19PHYSIOLOGY OF BRAIN PROTECTION
- EVOKED POTENTIALS
- Â Â Â Â somatosensory evoked potentials(SSEPs)
- Â Â Â Â Â Â Â dorsal spinal columns? sensory cortex?
??? ?? - Â Â Â Â Â Â Â Â Â spinal tumor? resection and spine, CEA,
aortic surgery? ??? - ? ????
- Â Â Â Â
- Â brain stem auditory evoked potentials
- Â Â Â Â Â Â Â Â Â 8th nerve and auditory pathway above
pons - Â Â Â
- Â Â visual evoked potentials optic nerve and
upper brain stem  -  Â
- Â Â EEG ?? more complicated??
- Â Â Â Â Â Â ??? ?? short and intermediate potentials?
???? ? ? ??