Neuro - anesthetic implications Flashcards
exam 1
Average CBF in adults
750 mL/min (15-20% of CO)
Rate of CSF production
15-20 mL/hr
total volume of CSF in system
150 mL
Spinal cord and brain blood supply
often have redundancy
Only artery of spinal chord that is not redundant
Artery of Adamkiewicz (Enters SC at T7 and suplies lumbosacral section)
SCPP level recomendations
> 40
Most important extrinsic factor influencing autoregulation
Key regulator or CBF
PaCO2
Intracranial HTN
sustained ICP 20-25 mmHg or higher
*some texts say 15 mmHg
Nitrous with neuro?
NO
Volatiles and neuro
give 0.5 MAC because all volatiles interfere with autoregulation
Ketamine a vasoconstrictor/vasodilator?
vasodilator and should be avoided
Circulatory steal phenomenon
arterioles in ischemic areas are maximally dilated and will not respond to vasodilators
so other vessels vasodilate and get blood instead
Fluid management: avoid
- dextrose
- hespan
- dextran
use NS
What agents are associated with isoelectric EEG changes?
- propofol
- isoflurane
- thiopental
Somatasensory evoked potentials (SSEP) monitors
ascending pathway (peripheral to brain)
tells us if there is an intact pathway from peripheral to spinal cord
SSEP anesthetic considerations
- Need goo mAP for good signals
- 0.5 MAC because SSEP is decreased with volatiles
*communicate what you give because monitoring is happening
Motor evoked potentials (MEP)
Monitors descending pathway, represents integrity of autonomic areas of spinal cord
stim applied to different areas, usually with TOF
Motor evoked potentials (MEP) anesthetic consideration
- No muscle relaxant during case
- affected by hypothermia, hypoxia, hypotension
BRainstem auditory evoked potentials (BAEP) does what?
monitor 8th cranial nerve during surgery that puts auditory nerve at risk
Visual Evoked Potentials (VEP) does what?
Monitors visual pathways from retina via optic nerve
what is the LEAST (barely) sensitive to anesthetics?
BAEP (brainstem auditory evoked potentials)
What is the MOST sensitive to anesthetic agents?
VEP (Visual evoked potentials)
Sensitivity to anesthetics in orders (evoked potential procedures)
VEP>MEP>SSEP>BAEP
Craniotomy induction/intubation consideration
smooth and gentle! Don’t want to stimulate
What is very common after craniotomy?
PONV
Craniotomy emergence considerations
Smooth wake up (dont want to stimulate) - prevent bucking/coughing
want quick emergence for early neuro assessment
MAP decreases (positioning)
decreases 0/7mm Hg/cm above heart (or 1.5mm Hg / inch)
In sitting procedures, MAP should be at
head level
Venous embolism and sitting
20-40% incidence rate
do not use nitrous
Most sensitive monitor for Venous air embolism
TEE (invasive)
pre-cordial doppler (non invasive)
Earliest sign of Venous air embolism
Sudden drop in ETCO2
then overall decompensation
Main treatment goal of venous air embolism
Stop entrainment of air!
Steps in venous air embolism treatment:
- Notify surgeon, floods field with NS
- Give 100% O2
- Place pt in L Lateral position with head down (Durant maneuver)
- aspirate air from R atrium if you have central line
Postoperative vision loss risk
prone spinal surgeries
Prevention postoperative visual loss
- appropriate position
- avoid eye compression
- MAP 60-70 to maintain BF to eyeballs
Once patient is positioned in sterotactic brain procedure (3D imaging):
do not touch patient
Ketamine and surgery to control seizures
avoid - activates seizures
The only truly reliable neuro exam for craniotomy is
an awake patient
allows for intra op speech, motor and sensory testing
Inclusions for awake craniotomy (3):
- normal airway exm
- able to lie still for extended period of time
- cooperative
Risk of transphenoidal hypophysectomy procedures
massive hemorrhage
(via nose)
